[digest version] guidelines for radiation safety in interventional...

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I GeneralIssues 1 Informulatingtheguidelines 2 Basicknowledgeofradiationexposurecontrol: A Differencesbetweenpatientexposureand exposureofmedicalpersonnel B Stochasticeffectsanddeterministiceffects C Measuringradiation(radiometry): (1)Tissue-absorbeddose (2)Equivalentdose

TABLE OF CONTENTS

(3)Effectivedose 3 Classificationbyseverityofradiation-induced skininjuriesandclinicalcourseII SpecificIssues(QsandAs) 1 Basicknowledgeofradiation-inducedskininjuries A Radiation-inducedskininjuriesinPCI B Areaswhereradiation-inducedskininjuriesare mostlikelytooccur 2 Informedconsentandcountermeasuresin

Chair:RyozoNagai,DepartmentofCardiovascularMedicine,

GraduateSchoolofMedicine,TheUniversityofTokyo

Members:KazuoAwai,DepartmentofRadiology,NationalHospital

OrganizationFukuiNationalHospital

YoshitoIesaka,DepartmentofInternalMedicine,TsuchiuraKyodoGeneralHospital

SugaoIshiwata,DepartmentofInternalMedicine, CardiovascularCenter,ToranomonHospital

TohruKikuchi,JichiMedicalSchoolRadioisotopeCenter

HarumizuSakurada,TokyoMetropolitanHirooHospital

MorioShoda,DepartmentofCardiology,TheHeartInstituteofJapan,TokyoWomen’sMedicalUniversity

InketsuSoh,Departmentofdermatology,ShowaUniversityNorthernYokohamaHospital

ShigemasaTani,DepartmentofCardiology,SurugadaiNihonUniversityHospital

HiromuNishitani,DepartmentofRadiology,TheUniversityofTokushima

YasunobuHirata,DepartmentofCardiovascularMedicine,GraduateSchoolofMedicine,TheUniversityofTokyo

HiroshiMizutani,DepartmentofRadiology,MatsuyamaRedCrossHospital

IchiroYamaguchi,YamagataPrefecture,MurayamaPublicHealthCenter

HiroshiYamashita,DepartmentofCardiovascularMedicine,GraduateSchoolofMedicine,TheUniversityofTokyo

IndependentAssessmentCommittee:TohruIzumi,DepartmentofCardio-angiology,Kitasato

University,SchoolofMedicine

TohruOhe,DepartmentofCardiovascularMedicine,TheSakakibaraHeartInstituteofOkayama

KatsuoKanmatsuse,TokyoHeartCenter

TetsuYamaguchi,ToranomonHospital

(TheaffiliationsofthemembersareasofMarch2010)

Guidelines for the Diagnosis and Treatment of Cardiovascular Diseases(2004-2005 JCS Joint Working Groups Report)

[digest version]

Guidelines for Radiation Safety inInterventional Cardiology (JCS 2006)

Joint Working Groups: The Japanese Circulation Society, The Japanese Coronary Association, The Japanese Society of Interventional Cardiology, The Japanese College of Cardiology, The Japanese Association of Cardiovascular Catheterization Therapeutics, The Japanese Society of Electrocardiology, The Japanese Dermatological Association, The Japanese Heart Rhythm Society, The Japanese Society of Radiation Safety Management, The Japanese Society of Radiological Technology

ThisEnglishlanguagedocumentisadigestversionofGuidelinesforRadiationSafetyinInterventionalCardiologyreportedattheJapaneseCirculationSocietyJointWorkingGroupsperformedin2004-2005.(CirculationJournal2006;70:Suppl.IV:1301-1327)

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GuidelinesfortheDiagnosisandTreatmentofCardiovascularDiseases(2004-2005JCSJointWorkingGroupsReport)

Ⅰ GeneralIssues

11 In formulating the guidelines

Astheprevalenceof interventionalprocedures to treatcardiovascular diseases increases, cases of radiation-inducedskininjuryamongpatientswhoundergocardio-vascular intervention are increasing rapidly. Warningsconcerningskin injuriesassociatedwith interventionalcardiologyhavebeenissuedbytheUSFoodandDrugAdministration(FDA)andtheJapanRadiologicalSoci-etysincethemid-1990s.However,cardiovascularphysi-cianshavegenerallynotbeenwell awareof radiation-inducedskininjuries,possiblybecauseoftheirinterestmainly in life-threatening diseases such as ischemic

heartdiseaseandarrhythmias.Interventionalcardiologyhasbecome increasinglysophisticated,and the indica-tionsforithaveexpanded.Thistrendhasresultedinanincreasednumberofradiation-inducedskininjuriesandothertypesofhealthhazards,suchascataractandhypo-thyroidism,inthosewhoperformtheprocedures.

Sincenotallphysiciansengagedininterventionalcar-diologyhavebasicknowledgeofradiation,appropriateeducationandtrainingprogramsarerequired.Fornurs-es and medical technologists working in departmentsother than radiology as well, it is important to have agood understanding of exposure doses that can occurduring work hours and their effects. In this situation,“the Guidelines for Prevention of Radiation-inducedSkinInjuriesAssociatedwithInterventionalRadiology(IVR)”were formulated in2001by the JapanAssoci-ation on Radiological Protection in Medicine with theparticipation of 13 academic institutions. The Guide-

caseofexcessexposureandonsetofradiation- inducedskininjuries A Matterstobeincludedintheexplanationof radiationinjuries B ExplanationandconsentduringPCIprocedureand subsequentmeasures C Explanationofandmeasurestakenafterexposure toexcessivedoses DMeasurestakenincaseofonsetofradiation- inducedskininjuries 3 Variablesaffectingexposuredoses: AEffectsofirradiationpulserate BEffectsofpatientbodytype C Distancebetweenimageintensifierandpatient DDistancebetweenX-raytubeandpatient ESizeoftransilluminationfield FEffectsofbeamlimiting G Effectsoffluoroscopic/imagingangle H Flatpaneldetector(FPD)typeimagingsystem I Effectsofpacemakersandleads J Effectsoftheupperarmintheirradiationfield onfluoroscopy/imaging 4 Effortstowardreductionofpatientexposuredose: A Generalrulesforreductionofexposuredose B Exposureduringemergencyexamination/treatment 5 Patientvariablesaffectingtheonsetofradiation- inducedskininjuries 6 Strategiesforreducingexposureinmedicalpersonnel: A Medicalpersonnelexposure B Howtousepersonaldosimeters C Typesandeffectsofprotectiveclothingandeffects ofleadequivalent D Maintenanceandmanagementofprotectiveclothing

E Effectsofgogglesandneckprotectors F Protectivedevicesrecommendedforinstallation intheimaginglaboratoryandhowtousethem G Dosedistributioninthecatheterizationlaboratory H Pregnancyoffemalemedicalpersonnel I Educationandre-educationofmedicalpersonnel J Requirementsforlaboraccidentindemnification approval 7 Managementofimagingsystems A Maintenanceandmanagementofimagingsystems B Measurestoreduceexposure 8 Non-coronaryintervention A PrecautionsinheadandneckIVR B Precautionsinpercutaneoustransluminal angioplasty(PTA)inlowerlimbs 9 Electrophysiologicalexaminationsandtreatments A Exposuredosestopatientsundergoingcatheter ablation BPrecautionsforpediatricpatients 10 Nuclearimaging A PrecautionsinperformingPCIonthesamedayas thallium(Tl)myocardialscintigraphyorthe followingday BExposureofmedicalpersonnelengagedinTl myocardialscintigraphy C Howtohandlesubcutaneousleakageofisotopes 11 CT A ExposuredosetopatientsundergoingcoronaryCT B Effectsoftheuseofmulti-rowdetectors C Effectsonpacemakerandimplantablecardioverter defibrillator(ICD) 12 Examinationandtreatmentofpregnantpatients

(All rights reserved)

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GuidelinesforRadiationSafetyinInterventionalCardiology

linesdescriberelevantissuesinareadilyunderstandablefashion, includingQ-and-Alessons,andarequiteuse-ful for cardiovascularphysiciansaswell.Unfortunate-ly,however,cardiovascularphysiciansarenotingener-alawarenessoftheiravailability.Inaddition,therehasbeenademandformorereadilyunderstandableguide-linesincludinganswerstocommonquestionssharedbycardiovascular physicians, procedures characteristicsofcardiovascularmedicine,suchaspercutaneouscoro-nary intervention(PCI)andablation, thebestmodeofinformedconsent, andother issues. In theUS, similarguidelinesforcardiovascularphysicianshavebeenfor-mulatedandpublished.

Members of the Japan Association on RadiologicalProtection in Medicine made significant contributionsto the formulationof thepresentguidelines.FeaturingQ-and-Alessonswithmanystraightforwardtablesandfigures,theguidelinesarebelievedtohelpeducateandtraincardiovascularphysicianswhoarenotspecializedinradiology.Wehopethatthepresentguidelineswillbeusedinthebestwaypossibleforthesakeofthesafetyofpatientsandmedicalpersonnel.

22 Basic knowledge of radiation exposure control: stochastic and deterministic effects, absorbed dose, effective dose, and dose units (Gy/Sv)

A Differences between patient exposure and exposure of medical personnel

Cardiac catheterization is a procedure performedfor diagnostic and therapeutic purposes by means ofimagesobtainedbythedeliveryofX-irradiationtothepatient.TheX-raysfromtheX-raysystem(X-ray tubefocus)delivereddirectlytothepatientduringthispro-cedure are termed primary X-rays. The X-rays thathaveenteredthepatient’sbodycollidewith theorbitalelectronsofatomsinthebodyandexhibitinteractions,suchasflippingoforbitalelectronswithlossofenergy(photoelectriceffect)andscattering indirectionsotherthanthedirectionofentrance(Comptonscattering).TheX-raysemittedfromthebodyasaresultoftheseinterac-tionsaretermedsecondaryX-rays.

AfactrequiringspecialattentionisthatwhiletheX-raytubeisthesourceofradiationcausingexposuretothepatient,thesecondaryraysfromthepatient’sbodymakeamuchlargercontributiontoexposureoftheoperator.

B Stochastic effects and deterministic effects

Mostorgansand tissues remainunaffectedby the lossofaconsiderablenumberofcells.Ifthenumberreachesacritical level,however, impairmentof tissuefunctionresults in an observable disorder. Although the prob-abilityofcausingsuchadisorder isnearlyzeroat lowdosesofradiation,itrisesto100%rapidlyafteragivenlevel ofdose (thresholdvalue) is exceeded.Above thethresholdvalue, theseverityofdisorder increaseswiththedose.Effectsof this typeare termeddeterministiceffects.Ifbiodefensivemechanismsfailtofunctionwellintheprocessofrepairofradiation-irradiatedcellsthathavesurvived,malignancy,i.e.,cancer,candevelopaftera latentperiod.Theprobabilityofonsetofcancerduetoradiationprobablyrisesinproportiontotheincreaseindose,withoutathresholdvalue,atleastatdosessuf-ficientlylowerthanthethresholdvaluefordeterministiceffects.Theseverityofcancerisnotinfluencedbydose.Effectsofthistypearealsoknownasstochasticeffects.Intheeventofsuchaninjurytogermcells,theeffectsofradiationwillbemanifestedinoffspringoftheper-sonexposed.Stochasticeffectsofthistypearetermedgeneticeffects.

C Measuring radiation (radiometry)

Theionizingradiation(hereinaftersimplyreferredtoasradiation) delivered to a patient is mostly absorbed inhis or her body tissue, with only a very small portionpermeating the body to contribute to the formation ofimages.Inaddition,theradiationdeliveredtothehumanbodyscatters inambientspace, reaching thebodiesofmedical personnel. The radiation delivered to humanbeings can have adverse effects. Because the amountofexposurecanbemarkedlyreducedbyimplementingappropriatemanagement,however,dosimetryisofcriti-cal importance inquantifying the levelofexposureofindividuals in particular conditions and thus enablingcontrolofexposureandensuringsafeprocedures.

(1) Tissue-absorbed dose

Thetissue-absorbeddoseofradiationisdefinedas theenergyperunitmassofhumantissueororgantransmit-tedbytheradiation.Assuch, thetissue-absorbeddoseserves as the basis for calculations of equivalent doseandeffectivedose,andisalsousedtoexpressdosesthathavecausedacuteradiation injuriesand inothercasesaswell.Theinternationalsystemofunits(SI)fortissueabsorbeddosesisJ/kg,with“gray”and“Gy”usedasthe

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specialunitnameandsymbol,respectively.

(2) Equivalent dose

Evenwhen themean tissue-absorbeddose for a tissueor organ is constant, the effects of radiation on livingorganismsvarydependingonthetypeofradiation.Forexample, the likelihood of chromosomal abnormalitydiffers between X-rays and neutron rays. Essentially,the equivalent dose of radiation is a modification ofthemeanabsorbeddoseforeachtissueororgantakinginto account the effectsof the radiation, andhasbeendefined as an index of the risk of carcinogenesis andgeneticeffectsintissuesandorgansresultingfromlow-doseexposure(riskofstochasticeffect).Inrelatedlaws,however,theequivalentdoseisusedasanindexoftheriskofdeterministiceffectsontheskin,lens,andfemaleabdomen (fetuses).The special unit name and symbolforequivalentdoseare“sievert”and“Sv”,respectively.

(3) Effective dose

Susceptibility to radiation-inducedcancersandgeneticeffects varies among tissues and organs. Hence, theequivalentdosemaybeaveragedbyweighingaccordingtotheradiosensitivityofeachtissueororgantoobtainanumericalindexknownastheeffectivedose.Theeffec-tivedoseservesasanindexoftheriskforcarcinogenesisandgeneticeffectsresultingfromlow-doseexposureinindividualpersons.Inrelatedlaws,theeffectivedoseisusedtospecifynotonlythelimitsofexposuretopersonsengagedinmedicalpractice,butalsoplacerelatedlimi-

tations, such as the boundaries of radiation-controlledareas.Thisisbecausethesedoselimitshavebeenestab-lishedaslegalregulationsonthedosestowhichpersonsenteringacertainlocationmaypossiblybeexposed.Aswithequivalentdose,thespecialunitnameandsymbolforeffectivedoseare“sievert”and“Sv”,respectively.

33 Classification by severity of radiation-induced skin injuries and clinical course

Ifthehumanbodyisaffectedbytissuedamageresult-ingfromradiationexposure,thisconditionistermedaradiationinjury.Sometypesofradiationinjurieshavenoclinicalsymptoms,andarehenceundetectablewithoutappropriateexamination.Ithasbeenshownthatthresh-olddosesexistfordeterministiceffects,suchasskinandlensinjuries,underwhichsucheffectsarenotobserved.The doses irradiated in ordinary imaging proceduressuchaschestX-rayradiographyaremuchsmallerthanthe threshold doses and will never cause skin injury.However,inPCI,catheterablation,andotherproceduresthatcaninvolvethedeliveryoflargeamountsofradia-tion, skin injuries can occur, making confirmation ofradiationdoseofparamountimportance.Alistofeffectsof radiationon theskinand lens, thresholddoses,andtimesofonsetisgiveninTable1.Thethresholddoseisanumericalvaluethatmustalwaysbeborneinmindbythe individual responsible for radiation delivery in thecontextofprotectionagainst radiation injuries. Inper-formingPCIorcatheterablation,itisimportantthatthe

Roughly estimated Effect threshold dose Time to onset (Gy)

Table 1

Early transient erythema 2 2 to 24 hours

Main erythema 6 within 1.5 weeks

Temporary epilation 3 within 3 weeks

Permanent epilation 7 within 3 weeks

Dry desquamation 14 within 4 weeks

Moist desquamation 18 within 4 weeks

Secondary ulceration 24 > 6 weeksDermal

Late erythema 15 8 to 10 weeks

Ischemic dermal necrosis 18 > 10 weeks

Dermal atrophy (1st phase) 10 > 52 weeks

Induration (invasive fibrosis) 10

Telangiectasia 10 > 52 weeks

Late dermal necrosis > 12 > 52 weeks

Skin cancer not known > 15 years

Lens opacity (detectable) > 1 to 2 > 5 yearsOphthalmologic

Lens/cataract (symptomatic) > 5 > 5 years

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Figure 1A Figure 1B Figure 1C

patient’sskin-absorbeddosebekeptbelowthethresholdvalue for serious injuries, in order to prevent seriousdeterministiceffects. It shouldbenoted,however, thatinactualcasesofskinorlensinjury,thecourseiswidelyvariable; the numerical value is thus not applicable toallcases.PriortoperformingPCIorsimilarprocedures,theupperlimitoftheskindoseshouldbespecifiedasanumericaltargetforradiationmanagementattheinsti-tution.Since therearecases inwhichpriority isgivento completion of the treatment over control of minordeterministiceffects,asinemergencymedicalservices,it isnecessary todetermine inadvance theproceduralstepstobetakeninordertoobtainthebestoutcomeforthepatient;thisincludesdeterminationoftheindividualmakingjudgmentsregardingcontinueddeliveryofirra-diationatlevelsexceedingthemanagementtargetvalue.

The earliest change after acute delivery of radia-tion is transient erythema,whichdevelops in severalhours.Thisisduetocapillarydilationuponreleaseofahistamine-likesubstancefromdamagedepithelialcells,andisonlyrarelyobservableclinically.Theskindam-age that follows (acute skin reaction) is classified intofour grades of severity, from degree 1 to degree 4, asshownbelow.

(1) Skin reactions of first degree

After irradiation, the proliferation of epithelial basalcellsisfirstinhibited,followedbykeratinizedlayerdes-quamation,resultinginthinningoftheepithelium.Thisreactionemergesabout3weeksafterirradiationof3to4Gydose.Theskinbecomesdry,andepilationoccurs.Almostnoothersymptomsdevelop.

(2) Skin reactions of second degree [dry dermatitis](Figure1A)

The major symptom is main skin erythema, in whicharterioles become partially stenosed, with increasedblood flow, resulting in dry dermatitis. The skin con-gestsandswells,butdoesnoterode,thendesquamationbegins.Erythemabecomesevidentabout2weeksafter

irradiationof6to19Gy,anditpersistsforabout3to4weeks.

(3) Skin reactions of third degree [moist dermatitis]

(Figure1B)

Irradiationofasingledoseof20to25Gyproducesbul-laeintheepithelium.Athigherdoses,bullaealsoappearinsubcutaneoustissue,andfusetogether.Uponbreakageofthebullae,subcutaneoustissuebecomesbare.Moistdermatitis develops about1weekafter irradiation andpersistsfor4to5weeks.Fibrindepositsinthewounds.Affectedregionsaresusceptibletoinfection.Afterabout1to2weeksregenerationoftheepitheliumbegins.

(4) Skin reactions of fourth degree [ulceration]

(Figure1C)

Thesereactionsoccurwithin1weekafterirradiationofadoseof30Gyormore.Deep-rederythemadevelops,followedbyformationofbullae,whichinturnerodetoformulcers,andtheepitheliumnecrotizesandsloughsoff. At higher doses, sharply indented radiation ulcerstypicallydevelop.Theepitheliumloses itsbasalmem-brane, leaving the thin layer of epithelium directly incontact with subcutaneous tissue; the affected skin isnowvulnerabletomechanicalstress.

It is important that the dose received by the patientinPCIbeaccuratelydeterminedwiththeabovefactsinmind,andthatthedoseandtimeofonsetofitseffectsbeconfirmed.Wheneverpossible,thepatientshouldbefollowedforanappropriateperiod,consideringthetimecourse of the adverse reactions to radiation describedabove.

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Ⅱ SpecificIssues(QsandAs)

11 Basic knowledge of radiation-induced skin injuries

A Radiation-induced skin injuries in PCI

Q1: I’ve heard that in PCI the patient receives higher doses than in other radiological procedures. Is this true?A: Figure 2 shows mean cumulative doses per examin62patientsundergoingPCIanddiagnosticcontrast-enhanced coronary angiography (CAG) at the Nation-alCardiovascularCenter.ItisevidentthatPCIinvolvesgreater doses than diagnostic contrast-enhanced CAG.InPCI,thetransilluminationtimeisextendedbecauseacathetermustbeinsertedintothetargetcoronaryartery,andathinguidewire,balloon,andstentareinsertedintothecoronaryarteryanddilatedorleftdeployed.Imagingmustberepeatedlyperformedtocheckthepositionsanddegreesofpatencyoftheballoonandstent.Asaresult,thedosereceivedbythepatientincreases.

Q2: I’ve heard that in PCI greater exposure occurs during transillumination than during imaging. Is this true?A: In diagnostic contrast-enhanced angiography, cath-eter insertion in the target coronaryartery is followedonly by repeated positioning and imaging in variousdirections. Since PCI, on the other hand, involves notonly catheter insertion into the target coronary arterybutalsothedeliveryofathinguidewire,balloon,andstenttotheinsideofacoronaryarteryanddilationandpositioningofthestentatdeployment,transilluminationtimemustbeextended.Inadditionimagingisrepeatedlyperformedtocheckthepositionsanddegreesofdilationoftheballoonandpatencyofthestent.Figure3showsmeantransillumination-imagingdoseratiosperexam

in62patientsundergoingCAGattheNationalCardio-vascularCenter.AlthoughPCI involves longer transil-lumination times than diagnostic contrast-enhancedangiography,thenumberoftimesimagingisperformedincreasesproportionately,sotheratioofdosesrequiredfor transillumination and imaging does not differmuchbetweenPCIandCAGperformedfordiagnos-ticpurposes.

Q3: How many grays of exposure are needed to induce complications such as skin erythema and skin ulcers on a patient?A: Thehumanbodyisinfluencedbyradiationinvari-ousways. If the skin-absorbeddose is2Gyormore,transienterythemaoftheskincanoccurrelativelyearly(within several hours), while irradiation of 24 Gy ormorecancauseskinulcers(seeTable1).

B Areas where radiation-induced skin injuries are most likely to occur

Q4: Why are skin injuries more prevalent on the right part of the back in PCI?A: As shown in Figure 4, the distance between theX-ray tube focus and the patient’s skin surface isshorter in the left anterior oblique (LAO) positionthan in right anterior oblique (RAO) position becausetheheartislocatedonthepatient’sleftside.Evenwithdelivery of X-irradiation of the same intensity for thesamelengthoftime,agreaterdoseentersthepatient’sbodyinLAOthaninRAO.WhenthedirectionofX-rayentranceisRAO,theheartisobservedthroughtheleftlungfromthepatient’sleftback.Incontrast,inthecaseofLAO,theheartisobservedthroughthevertebralcolumn and mediastinum from the patient’s rightback.ThelungsareeasilypermeatedbyX-raysbecausetheycontainmuchair,while thevertebralcolumnandmediastinumaremuchlesspermeabletoX-raysbecauseoftheirhighdensities,andthusrequiringhigherdoses.

Figure 2 Patientexposuredosesindiagnosticcoronaryangiog-raphyandpercutaneouscoronaryintervention(PCI)

Comparative data with 1 unit dose received by the patient in conventional diagnostic coronary angiography

Diagnosis includingbypass surgery

Angiography diagnosis 1.00

1.36

1.48PCI

0 0.5 1 1.5 2

Figure 3 Dosesdeliveredduringfluoroscopyandimaginginanexamination

PCI:percutaneouscoronaryintervention

PCI

49.0

54.0

50.2

51.0

46.0

49.8

0 50 100

Diagnosis includingbypass imaging

Fluoroscopy Imaging

Angiography diagnosis

(%)

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Forthisreason,skininjuriesaremoreprevalentontherightpartofthepatient’sbackthanelsewhere.

22 Informed consent and countermeasures in case of excess exposure and onset of radiation-induced skin injuries

A Matters to be included in the explanation of radiation injuries

Q5: In obtaining informed consent prior to CAG or PCI, what should be explained regarding radiation injuries? I am concerned that explana-tion of such injuries may increase patient anxiety.A: Although the PCI procedure is less invasive thanordinarysurgicaloperations,itinvolvestheuseofradi-ation, so prolonged treatment can result in radiation-induced skin injuries. It is therefore important thatprior toperformingPCIanexplanationofradiation-inducedskininjuriesbeprovided,inadditiontoinfor-mationonthemethodusedintheprocedureandpossiblecomplications.

Sinceinconsistencyincontentofexplanationsamongthoseproviding themmakes thepatientmoreanxious,it is important that an explanatory manual or the likebe produced to ensure that the contents of explana-tionareunifiedacross the institution.Althoughexpertknowledgeisrequiredtoexplaintheeffectsofradiation,itisimportantthattheprovideroftheexplanationbearinmindthereasonforthepatient’sanxiety,ratherthanmerelyusingjargonandpresentingnumericaldata,soastoputhimorheratease.

Sinceaspecificexplanationhelpseasethepatient,the

operatorshouldendeavor tobeable toexplain the fol-lowing:

- There are threshold values for radiation-inducedskininjury.

- Thedosecanexceedthe thresholdvalueforradi-ation-inducedskininjurydependingonthecourseoftreatment.Insuchcases,consenttocontinueordiscontinuetheexaminationistobeobtainedfromthepatient.

- Thesystemusedfordeliveryofradiationisappro-priatelycontrolledtoensurethattheexaminationisalwaysperformedattheoptimaldose.

- Theoperatorwillendeavortocheckskinentrancedoses by monitoring the conditions of irradiationandimplementingotherprotectivemeasures.

- Countermeasures against radiation-induced skininjuryareavailable.

Explanation of the above is required even in emer-gencyexaminations.

B Explanation and consent during PCI procedure and subsequent measures

Q6: If transillumination time is prolonged during PCI to the extent that the patient exposure dose approaches levels that can cause skin injuries, how can I determine whether to continue or discontinue the procedure?A: Thethresholddoseforpossibleonsetofearlytran-sienterythemais2Gy(Table1).Theexposuredoseperunittimevarieswidelyamongdifferentinstitutions,andalsodependsonimagingconditions(thepatient’sbodytype,angleofimaging,framerate,etc.).Therefore,eachinstitution shouldestablish a reference levelof transil-lumination and imaging times corresponding to 2 Gy.Whenitisfoundthatthesumoftransilluminationandimagingtimesislikelytoreachthislevel,theoperatorshoulddeterminewhethertocontinueordiscontinuetheexaminationorprocedure.Iftheoperatorjudgesthatthebenefitstothepatientofcontinuingtheexaminationortreatmentwilloutweightheriskofradiationinjuries,theexaminationortreatmentmaybecontinued.Itisdesir-able, however, that even when prior consent has beenobtainedwithafullexplanationoftheriskofradiation-inducedskininjury,thepatient’sintentbereconfirmedatthetimewhenthisjudgmentismade.Ifitisdifficulttoconfirmthepatient’sconsent,consentmaybeobtainedfromhisorherfamily.Insituationsinwhichthepatient’slifeisthreatenedbyacutemyocardialinfarction,shock,orothersevereconditions,priorityshouldbeplacedonlife-savingratherthanonavoidingtheonsetofradiation-

Figure 4 DifferencesinX-rayentranceangleandexposuredosebetweenLAOandRAO

LAO: leftanterioroblique,RAO:rightanterioroblique, I.I.: imageintensifier

An organ featuring high X-ray absorption is present

The distance is short X-ray tube focus position

The distance is long

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inducedskininjuries.If the examination or procedure is continued even

afterthethresholddoseisjudgedtohavebeenreached,stillgreatercautionshouldbeexercisedinreducingtheexposure dose. Possible measures include (1) loweringthe fluoroscopy pulse rate and/or imaging frame rateand(2)changingthefluoroscopyand/orimagingangletoshifttheskinirradiationfieldtootherpositions(seeQ22andFigure15).

C Explanation of and measures taken after exposure to excessive doses

Q7: If it is found after the performance of catheter intervention that the patient exposure dose may have exceeded the threshold dose for the onset of skin injury, what measures should be taken?A: Thepersoninchargeofradiationsafetymanagementshould informtheattendingphysicianof thepredicteddoseandseverityofskininjury,andrequestsubsequentcountermeasures.

Thespecificactionstobetakenareasfollows:1.Obtain informed consent from the patient for such

actions(seeQ8).2.Prepare a patient skin-absorbed dose report and

inform all persons concerned of the delivery of adose exceeding the threshold as documentation forfollow-upexamination(seeQ9).

3.Detectionofinitialinjuries:Earlytransienterythemaappearssoonaftertheexamination,askanattendingphysicianornursetomonitorthesiteofirradiation.

4.Notification to dermatologist and request for coop-eration(ifrequiredbecauseofseverityofpredictedinjury):Notify thedermatologistof thesiteof irra-diation,exposuredose,andpredictedseverityofskininjury. It is desirable that the skin-absorbed dosereportbesubmittedwithattachmentofanexamina-tion status report (examination records) and refer-ence documents concerning radiation-induced skininjuries.

Withthesecontentsincluded,amanualshouldbepre-paredfortheinstitutioninordertodealwithskininju-ries.Inallcases,it isimportantthatallstaffmembersendeavortodevelopandmaintaingoodcommunicationwitheachotherinordertoworktogetherasateam.

Q8: If a dose that can cause radiation-induced skin injuries has been delivered, what explanation should the patient receive?A: Irrespectiveofwhetherprior informedconsenthasbeenobtained,informthepatientthatthetreatmentwasnecessary, and provide an explanation of your institu-

tion’spolicyonthetreatmentofskininjuries.Evenwhenprior informedconsenthasbeenobtained,anexplana-tionshouldbeprovidedagainforthesakeofconfirma-tion.

Thepatientshouldbegiventhefollowingadviceandsuggestionsregardingmeasurestobetakenforthepartsoftheskinwhereinjuriesmayoccur:1.Periodicmedicalfollow-upexaminationisnecessary.2.Theeffectsof radiationusuallyappearaftera time

lag.3. Tellthepatientthepartsoftheskinwhereinjurymay

occur,andinstructhimorhernottoscratchthem,toavoidtheuseofhighlyirritatingbathingagentsandsoapsduringbathing,andnottoapplyanydrugsoth-erthanthoseprescribedbythephysician.

4.Ifanychangeoccurs inskinsymptoms, thepatientshouldundergomedicalexamination.

Q9: If a dose that can cause skin injury has been delivered, is it necessary to record the fact? If so, please show how this is done and which form is used.A: In PCI performed with repeated delivery of radia-tion, the effects of radiation are additive, even doseslowerthanthethresholdvaluecancauseskininjury,andrepeatedirradiationduringaprocedurecanexacerbatean injury. In case of irradiation to the same site withshort intervalsbetweenboutsof irradiation, thesiteofirradiationanddoseshouldberecorded,andtheopera-torshouldstrivetopreventexcessiveirradiation.IntheInternational Commission on Radiological Protection(ICRP)Publ.85,itisrecommendedthatiftheskinexpo-suredosecanbeestimatedtobe3Gy(1Gyforcasesofrepeatedirradiation)ormore,theestimateddoseandthesiteof irradiationbe indicatedonanappropriatebodysurfacemap.

D Measures taken in case of onset of radiation-induced skin injuries

Q10: In case of slight acute dermatitis that has remitted quickly, is it necessary for the patient to be treated with medication or to undergo ambulatory treatment at an outpatient dermatology clinic?A: IfslightskininjurydevelopsearlyafterperformingPCIandthendisappearsspontaneously,theconditionisdeemed early transient erythema (early erythema:thresholddose=2Gy)ormainerythema(thresholddose=6Gy).Mainerythemaoftenleavespigmentation(ordepigmentation)afterhealing.Ifithashealedwith-outpigmentation, it isquiteunlikely thatdelayed skininjurywilldeveloplater,sonodermatologicaltreatmentisnecessary,noristhereanyneedforperiodicfollow-up

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examination.Visits toadermatologistareneededonlyafterthepatientorhisorherfamilyhasnotedachangeinthepatient’sskin.Ifandyschromiaremainsinapartoftheskinwhererashhashealed(mainerythema),therisk of subsequent development of delayed skin injurycannotberuledoutevenif thechangeisinitiallyverymild,soperiodicfollow-upexaminationbyadermatolo-gist is required.Regarding thedurationand frequencyofambulatorymedicalcheckups,itisdesirablethatthepatientvisit the institutionevery3months for about1year.Evenifthedyschromiaremains,however,macro-scopic observation alone is sufficient, with no specialtreatmentrequired.Inallcases,itisimportantthatthesiteof irradiation anddosebe recorded at the timeofirradiation.

33 Variables affecting exposure doses

A Effects of irradiation pulse rate

Q11: To what extent can I reduce the exposure dose by lowering the pulse rate or image acquisi-tion rate during fl uoroscopy?A: Pulsedfluoroscopyiseffectiveasamethodofreduc-ingexposureinPCI.AsshowninFigure5A,exposuredosedecreasesasthepulseratefallsfrom30p/sto15p/sandthento7.5p/s.Itshouldbenoted,however,thatthe doses irradiated at high pulse rates are similar tothosewithcontinuousfluoroscopy,soifpulsedfluoros-copy isused inanattempt to reducepatient exposure,a lowpulseratemustbeused.In thesystemshowninFigure5A,thereisaproportionalrelationshipbetweenpulserateanddose.Inothertypeofsystemsasshownin

thefigure,however,evenwhenalowpulserateischosentoexamineapatientwithalargebody,thesystemauto-matically expands the pulse width, increases the tubecurrent, or takes other measures to ensure that dosescomparable to those with high pulse rate fluoroscopyaredelivered. Insuchcases,choosinga lowpulseratedoesnotalwaysleadtoareducedexposuredose.Priortousingthesystem,it isnecessarytobecomefamiliarwiththeitsperformancebytakingactualmeasurementsusingit,oraskingthemanufacturertoprovidedetailedspecifications for the instrument in different operatingconditions.Inaddition,sinceitisdifficulttoconfirmthepositionofcathetersandotherdevicesinbloodvesselsunder low pulse rate fluoroscopy if performed by anunskilledoperator,itisimportantthatthistechniquebeutilizedonlyafterafulldiscussionwiththeoperator.

Theimageacquisitionrateduringimagingalsoinflu-encespatientexposuredose.Figure5Bshowsthedosesreceivedbythepatientatimageacquisitionratesof15f/s,30f/s,and60f/s.Becausethedosereceivedbythepatient increases as the image acquisition rate rises,emphasisshouldbeplacedonchoosinganimageacqui-sitionratesuitableforthepatient’sheartrateandpatho-logiccondition,andminimizingthedosereceivedbythepatient,ratherthanonincreasingtheimageacquisitionratemerelytoimprovevisibility.

B Effects of patient body type

Q12: To what extent does exposure dose differ depending on the body type of the patient?A: Generally, obese patients receive greater doses perunittimethanthinpatients.Figure6showsthediffer-ence in entrance surface dose for two patients 15 cmand25cminbodythickness;asthesubjectofimaging

Figure 5A Relationshipbetweenpulserateandexposuredoseinfluoroscopy

Exposure doses are expressed using the dose at 7.5 p/s as a unit (using 9-inch image intensifi er and acrylic resin phantom 20 cm in diameter)

Figure 5B Relationship between number of imaging framesandexposuredose

Exposure doses are expressed using the dose at 15 f/s as a unit (using 9-inch image intensifi er and acrylic resin phantom 20 cm in diameter)

5

7.5p/s 15p/s 30p/s

4

3

2

1

0

Patient exposure dose

Operator exposure dose

5

15f/s 30f/s 60f/s

4

3

2

1

0

Patient exposure dose

Operator exposure dose

10


thickensby10cm,theentrancesurfacedosenearlyqua-druples.Therefore,whenthesubjectisanobesepatient,the cumulative dose administered during examinationmustbecarefullymonitoredinordernottoadministerexcessivedosesofradiation.Ofnote,theoperatorisalsosubject to greater exposure when examining an obesepatient.

C Distance between image intensifi er and patient

Q13: Why does the exposure dose increase as the image intensifi er becomes more distant from the patient? What is the operator exposure dose under such conditions?A: IfthedistancebetweentheX-raytubeandpatientisconstant,thedistancebetweentheX-raytubeandimageintensifier increases as the image intensifier becomesmoredistantfromthepatient,soautomatedadjustmentby the system ensures delivery of a larger amount ofX-rays.Asaresult,thepatientexposuredoseincreases.Figure 7 shows the change in entrance surface dosewhereradiationenterswhentheimageintensifierisdis-tancedfromthepatientwhilekeepingthecathetertableheightconstant.Withincreaseindistanceoftheimageintensifierofonly10cm,theentrancedoseincreasesbyabout15%.Inroutineexamination,theimageintensifierandpatient areoften separatedby about10 cm.How-ever,sinceevensmallchangeswillleadtomajordiffer-

encesindoseiftheyaccumulate,thedistancebetweenthe image intensifier and the patient must be kept ascloseaspossibleinordertoavoidexcessiveirradiationofthepatient.Thedosereceivedbytheoperatorchangesrelativelylittlewhentheimageintensifierisplacedmoredistantfromthepatient.

D Distance between X-ray tube and patient

Q14: Tips for reducing radiation exposure include the statement “distance the patient from the X-ray tube as much as possible.” Why? And what is the operator exposure dose when the examination table is at low position?A: AsthedistanceofthepatientfromtheX-raytubeisincreased,thedistancebetweentheX-raytubefocusandimageintensifierincreases,sotheX-rayoutputincreas-es.Atthesametime,however,theamountoflow-energyX-raysreachingthepatient,whichdonotcontributetoimagesbutdohaveamajorimpactonpatientexposure,decreases,soskindosedecreases.ThisisexemplifiedinFigure8.Asthepatientisbroughtabout10cmclosertotheX-raytube,thedoseincreasesbyabout15%,soitisnecessarytoheightenthecathetertabletodistancethe patient from the X-ray tube, as long as this doesnotinterferewithproceduresbytheoperator.Thedosereceived by the operator remains unchanged with thisalteration.

1.0 Dose Unit << 4.0 Dose Unit

15cm 25cm

1.0 Dose Unit 4.0 Dose Unit

Patient dose

X-ray tube X-ray tube

Thin patient (15 cm body thickness) Obese patient (25 cm body thickness)

Figure 6 RelationshipbetweenpatientbodytypeandexposuredoseDoses received by the patient/operator are expressed relative to those in the thin patient case, with the latter considered 1 dose unit (7.5-inch image intensifi er [I.I.], pulsed fl uoros-copy at 15 p/s)

11


Whenashortoperatorperformstheexamination,heorsheisapttolowerthecathetertabletofacilitatetheoperation.However,loweringthetablemakesthepatientand X-ray tube approach each other, which in turnincreasesthepatientexposuredose;cautionthusneedstobeexercisedinthisregard.

E Size of transillumination fi eld

Q15: In PCI, magnifi ed views are often used to obtain clear images of the guidewire and stent. What is the extent of change in dose received by the patient associated with this?A: Whenthe image intensifiersize is reducedand the

Figure 7 Relationshipbetweenimageintensifier(I.I.):subjectdistanceandexposuredoseComparative data with 1 dose unit received by the patient/operator with the I.I. in close contact with the patient’s body

1.0 Dose Unit << 1.15 Dose Unit

1.0 Dose Unit

1.0 Dose unit

10cm

The I.I. placed in close contact with the patient’s body

Patient dose


The I.I. placed 10 cm from the patient’s body

Patient dose1.0 Dose Unit << 0.87 Dose Unit

10cm


Figure 8 Relationshipbetweenexposuredoseandpatient-X-raytubefocusdistanceWhen the distance between the X-ray tube and patient is increased by 10 cm, the dose received by the patient decreases by 13%.I.I.:imageintensifier

12


screen is expanded, the dose received by the patientincreases, as shown in Figure 9. By contrast, whenthe image intensifier size is increased and the field iswidened,thedosedecreases.Traditionally,thishasnotcommonlybeenperformedsincemagnifiedviewswithsmaller image intensifier sizes lead to a lack of dose,whichhampersobtainingclearimages.However,recenttechnical innovations, including theexpandedcapacityofX-raytubesandtheintroductionofnewtechnologiessuch as digital image processing have, along with thespreadofPCI,ledtothecurrentwideuseofmagnifiedviewsatmanyinstitutions.AlthoughthisisessentialforensuringsafeperformanceofPCI, it results ingreaterpatientdoses,souseshouldbelimitedtotheminimumrequiredfrequencytopreventskininjuries.Evenwhenthefieldofirradiationisexpanded,irradiationofpartsof the skin where irradiation is unnecessary must beavoidedbyusingthebeamlimitingdevice.

As the image intensifier size is reduced, thefieldofirradiationisautomaticallynarrowed,andtheoperator’sdosethereforedecreases.Astheimageintensifiersizeisincreased,thefieldofirradiationwidens,withincreaseinscattereddoseandatendencyforoperatorexposuredosetoincrease.

F Effects of beam limiting

Q16: As the fi eld of irradiation is narrowed, does patient exposure dose actually decrease?A: Figure10comparespatientexposuredosesproducedwithafullyopenfieldofirradiationandanarrowedfieldof irradiationwith70%of the initial area.Evenwhenthefieldofirradiationisnarrowed,thedoseperunitareareceived by the patient remains unchanged. However,as thefieldof irradiation increases, theareaofskinatrisk for skin reactions to radiation such as ulcers willincrease, so effort is always needed to avoid irradia-tionofsiteswhereitisunnecessary,inordertopreventradiationinjury.Additionally,bynarrowingthefieldofirradiation, the area of skin irradiated repeatedly dur-ing fluoroscopy or imaging at different angles can benarrowed. In Q22 a method is described for avoidingskin injuriesby changing the angleofX-ray entrance.Whenthefieldofirradiationislimitedtoasmallareainadvance,theoperatormaychangetheentranceangleonlyslightlytoavoidirradiatingthesameregionoftheskin.Ofcourse, theoperator’s dosealsodecreasesasthefieldofirradiationisnarrowed.

Figure 9 Magnificationinfluoroscopy/imagingandexposuredosesComparative data with 1 dose unit received by the patient/operator from a 7-inch image intensifi er (I.I.)

Patient dose1.0 Dose Unit << 1.3 Dose Unit


5-inch I.I.


7-inch I.I.

13


G Effects of fl uoroscopic/imaging angle

Q17: I’ve heard that in LAO cranial views and LAO caudal views, the patient skin-absorbed dose is high. Why? And how can I reduce this dose?A: TheX-rayfluoroscopic/imagingdeviceiscontrolledtokeepthedoseenteringtheimageintensifierconstant.AsthedirectionofX-rayentranceischanged,thethick-nessofthesubjectimagedchangesaswell,andthedoseis adjusted according to the thickness irradiated. Thisis why the patient entrance dose differs depending onthe X-ray entrance angle. Figure 11 compares doseswith various entrance angles using phantoms; there isanapproximatelytwo-folddifferenceindoseamongthedifferent entrance angles evaluated. In the LAO pro-jection,theheartisexaminedthroughthevertebralcolumn and mediastinum from the patient’s rightback, sogreaterdosesaredelivered. In the cranialor caudal projection, body thickness increases stillmore,sogreaterdosesaredelivered (seeFigure4).This is the reasonwhy thedose increases in theLAOcranialandLAOcaudalprojections.When theexami-nationisperformedusingtheseX-rayentranceangles,theoperatorshouldendeavortoreducethedoseby,forexample,loweringthepulserateorincreasingtheimage

intensifiersize.SincePCIinvolvesrepeatedcyclesoffluoroscopyand

imagingwithaconstantX-rayentranceangleforapro-longedperiodoftime,itisimportanttounderstandtherelationshipbetweentheentranceangleanddoseforthe

Figure 10 BeamlimitingdeviceandexposuredoseComparative data with 1 dose unit received by the operator when the fi eld of irradiation is fully open (7-inch)I.I.:imageintensifier


The entrance dose perunit area is the same

Beam limiting device

Fully open irradiation field Limited irradiation field


Figure 11 FluoroscopicangleandexposuredoseComparison of exposure doses during pulsed fl uoroscopy at 15 p/s at different angles. The dose in a 7.5-inch P-A view was set as 1 dose unit. P-A:posterior-anterior,RAO: right anterior oblique,CRA: cranial,CAU:caudal,LAO:leftanterioroblique,L-LAT:leftlateralposition

2.5

P-A RAO30° RAO30°+CRA25°

RAO30°+CAU25°

LAO60° LAO55°+CRA25°

L-LAT

2

1.5

1

0.5

0

Dos

e ra

tio

Arm angle

14


systemused,and toprevent thepatient fromreceivingexcessivedoses.

H Flat panel detector (FPD) type imaging system

Q18: The FPD type imaging system reportedly generally enables reduction of exposure dose, although I’ve heard that the exposure dose in fact increases in some cases. In which cases does the exposure dose rise? And what are the points of note in using the system?A: Currently,therearetwomodesofimagingbyFPD:directconversionand indirectconversion (Figure12).The direct conversion type employs amorphous sele-nium (a-Se) as the X-ray imaging medium. The elec-tricchargegeneratedbyX-rays in thea-Semediumisdirectlyreadoutusingathin-filmtransistor(TFT).Thedirectconversiontypeinvolvesonlyslightlossofenergyduringenergyconversion,andhasexcellentspatialreso-lution. In the indirectconversion type,X-raysenteringtheimagingsystemareconvertedtovisiblelightthroughafluorophoresuchascesiumiodide(CsI)astheX-rayimagingmedium,usingaphotodiodeorthelike,whichisthenconvertedtoelectricsignals.Althoughsomelossofimagequalityduetolightscatteringisunavoidable,this type is now commonly used for cardiovascularimagingbecauseitiseasytoperform.

AdvantagesofFPDincludethefollowing:1.The device undergoes less time-related deteriora-

tion,ensuringimagequalitythatisstableoveralongperiodoftime;

2. Lackofdistortion;3.Highcontrast.

Since FPD has higher efficiency in X-ray detectionthanimageintensifiers,ittheoreticallyenablesreductionofdose. In fact, in imagingatahighdose rate,whichisnotinfluencedbyX-rayquantumnoise(noisecausedbyrandomfluctuationofquantumflow),someextentofdose reduction is possible. On the other hand, in low-dosefluoroscopy,whichisinfluencedbyX-rayquantumnoise,FPDcontributeslesstodosereductionthanimageintensifiers,sothecumulativedoseperexaminationisthesameaswithimageintensifiers.However,becauseFPD has advantages including little time-related dete-rioration,aswellaseaseofsystemqualitycontrolandfreedomfromimagedistortion,itisexpectedtoreplaceimageintensifiersinthefuture;expansionofitsuseandimprovement of its performance will together lead toreductionsofdose.

Inaddition,sinceFPDhasabroaddynamicrange,nohalationisproducedevenwithoutuseofacompensatingfilter.AnotheradvantageoftheFPDdeviceisitseaseofuse,since thedosedoesnot increasemuchevenwhenthefieldisexpanded,aswithimageintensifiers.Howev-er,itsdynamicrangeiswideenoughthatexcessivedosesofirradiationarelikelytobeoverlookedbecauseoftheabsenceofhindrancetoimagereconstitution.Evenmoreeffortisthusneededtoreduceradiationexposureusingconventionaldose-reductionapproaches.

Figure 12 Schemesofflatpaneldetector(FPD)typeimagingsystemsComparison of different types of devicesCsI:cesiumiodide,TFT:thin-filmtransistor

X-ray

Input phosphor screen

Photoelectricsurface

Focusingelectrode

Output phosphorscreen

Optical lens

TV camera

Electric signal

Light

Positive electrode

Electrons

Light

(a) Image intensifier-TV camera type (b) Indirect conversion type FPD (c) Direct conversion type FPD

Fluorophore (CsI etc.)

Photodiode

X-ray

Light

Electricsignal

Amorphousselenium

Ele

ctric

sig

nal

X-ray

TFTTFT

X-ray

15


I Effects of pacemakers and leads

Q19: Why does the exposure dose increase when the body of a pacemaker or a lead enters the fi eld of irradiation?A: X-irradiation conditions during fluoroscopy andimagingdependonthedosereceivedbythephotorecep-tor in the center of the image intensifier. Figure 13showstherelationshipbetweenthepositionofthepace-makerinthefieldofirradiationandthecorrespondingdoseratio.Whenapacemakerispresentintheperiph-eralportionofthefield,wheredeterminationofX-irra-diationconditionsisnotaffected,theconditionsremainunchanged,sothedosereceivedbythepatientdoesnotchange.However,whenthepacemakerispresentinthecenterofthefield,X-irradiationoccursinamountsthatdepend on the material of the pacemaker. Generally,sincethepacemakerismadeofmetal,largeramountsofX-raysarerequiredthanforahumanbodyofthesamethickness.Therefore,whenthepacemakerispresentin

thecenterofthefieldofirradiation,thedosereceivedbythepatientincreases,andatthesametimeanexcessivedose is delivered to the surrounding tissue where thepacemakerisabsent,whichcanresultindeteriorationofimagequalityduetohalationorotherfactors.Forthesereasons, it is importantnot to locate thepacemaker inthecenteroftheimageintensifierwheneverpossible.

J Effects of the upper arm in the irradiation fi eld on fl uoroscopy/imaging

Q20: In case of entry of the patient’s arm (upper arm) into the irradiation fi eld, does the dose received by the patient change? What are the points to note in protection against skin injury in this case?A: WhenX-raysaredeliveredtoapatientfordiagnosticor therapeuticpurposes,abasic ruleofX-ray imagingis to remove objects that interfere with imaging fromtheirradiationfieldinordertoobtainclearimages.Forthisreason,thepatientisaskedtoraisehisorherarmif

Figure 13 EffectsofapacemakerintheirradiationfieldondoseComparative data with 1 dose unit without pacemaker

1.50

1.25

1.00

0.75

0.50

0.25

0.000 1 2 3 4 5 6 71234567

Dos

e ra

tio

Distance from center of image intensifier (cm)

The image intensifier determines X-irradiation conditions in this region

16


it enters the irradiationfieldduringcoronary imaging.Recently,however,CAGhasoftenbeenperformedwithapproachfromthecubitalarteryorradialartery,andthenumber of cases of inability to raise the arm has cor-respondinglyincreased.

Additionally, catheter ablation is sometimes per-formedwhileneitherarmisraised,forvariousreasons,includingthegreatburdenplacedonthepatientbythelong period of examination; the use of an electrodecatheter,whichfeaturesrelativelyhighX-rayvisibility,ensuring that the presence of interfering shadows ofarmsinthefieldofirradiationdoesnotmarkedlyinter-fere with examination; and the increased capacity ofX-raytubesystemsallowingfluoroscopyevenwithbotharmslocatedintheirradiationfield.

Figure14showsthepositionalrelationshipbetweentheirradiationfieldandthepatient’sarmasitenters,andcorrespondingdoseratios.Evenifanarmispositionedin thevicinityof the irradiationfieldand thepresenceof thearmdoesnotaffectX-ray irradiationconditionsbecausethearmitselfwillnotbeexposed,thedistancebetweentheX-raysourceandskinisdecreasedbythethicknessofthearm,andthedoseattheskinentrancesurface increases.Furthermore, ifanarmis locatedatthecenteroftheimageintensifier,moreintenseirradia-tionisrequiredduetothepresenceofthearm,andthedistancebetweentheX-raysourceandskindecreases,

sothedosereceivedbythepartofthearmintheirradia-tionfieldisextremelyhigh.

In irradiation with an upper arm in the irradiationfield, the distance the X-ray beam travels across thepatienttoreachtheimageintensifierincreases,buttheintensityofradiationisexponentiallyattenuatedwithinthe patient’s body. For this reason, lateral irradiationwithanupperarmintheirradiationfieldresultsindeliv-eryofgreatenergytotheskinoftheupperarmatthesiteofentrance,whichtheoperatorneedstobeawareof.Everyeffortshouldthusbemadetokeeptheupperarmawayfromtheirradiationfieldto themaximumextentpossible by, for example, changing the X-ray entranceangle and positioning the upper arm distal from thetrunkappropriatelysothatitdoesnotentertheirradia-tionfield.

44 Efforts toward reduction of patient exposure dose

A General rules for reduction of exposure dose

Q21: Please show how to reduce the patient dose during PCI.

Figure 14 RelationshipbetweenpatientarmpositionandexposuredoseComparative data with 1 dose unit received by the patient without the patient’s arm in the irradiation fi eldI.I.:imageintensifier

With arm in the irradiation fieldWithout arm in the irradiation field

X-ra

y tub

e

X-ra

y tub

e

17


A: The general rules for protection from sources ofradiation outside the patient’s body concern (1) time(shortenthetimeofirradiation),(2)shielding(blockradiation), and (3) distance (ensure sufficient dis-tancefromthesource).Table2showsspecificwaysoffollowingtheserules.

B Exposure during emergency examination/treatment

Q22: A patient with acute myocardial infarction is undergoing PCI. The monitored dose has exceed-ed the level that can cause skin injuries, but the examination cannot be terminated prematurely because no other means of treatment is available. Is there any way of continuing the examination without causing skin injury?A: Although priority should be placed on saving thepatient’slife,ratherthanavoidingskininjury,skininju-ryshouldbeminimizedtotheextentpossible.Toavoidskininjury,thesystem’sarmmayberotatedtochangethesiteof irradiationonthepatient’sskinsurfacetoadifferent position. In some types of imaging systems,overlappingexposureofregionsofskintoprimaryX-raybeamscanbeeliminatedbyrotatingtheX-rayentranceangleby40˚ormore(Figure15);thesameappliesnotonlytotheaxialdirection(RAO-LAO)butalsothecra-

nio-caudaldirection.SincePCIisperformedatananglethat enables the best identification of the lesion, it issometimesdifficulttochangetheanglemidway,thoughthismayneedtobeconsidered,anditisimportantthattheoperatorbeawareoftheanglesofradiationoverlapofthesystemusedinhisorherinstitution.

55 Patient variables affecting the onset of radiation-induced skin injuries

Q23: Are some patients more susceptible to radia-tion-induced skin injury than others (due to the age and body type of the person exposed, which part of the skin is exposed, underlying disease, drugs, and other variables)? Are there any age-related dif-ferences in the likelihood of radiation-induced skin injury? If the elderly are particularly likely to suffer skin injury, is it better to consider the patient’s age in deciding whether to perform restudy CAG?A: The likelihood of radiation-induced skin injuriesdependsonthefollowingvariablesonthepatientside.1.Age:The biological effects of radiation are thought to vary

1. Avoid unnecessary fl uoroscopy and imaging. 2. Set the frame rate to as low a level as possible and

shorten the imaging time to minimize imaging-related irradiation.

3. Have a good understanding of the relationship between dose and image quality, and perform the examination under irradiation conditions suitable for the system and examination procedure. For example, fl uoroscopy and imaging using high tube voltages generally leads to reduction of skin-absorbed doses due to its favorable X-ray penetration, although contrast may decrease slightly due to increased Compton scattering.

4. For fl uoroscopy, use the minimum possible pulse rate acceptable to the operator.

5. Use a supplementary fi lter. 6. Distance the X-ray tube from the patient as much as

possible. 7. Bring the image intensifi er into a position as close to

the patient as possible (avoid frequent use of geometric magnifi cation).

8. Minimize the use of magnifi cation during fl uoroscopy and imaging.

9. For patients of small body size and in procedures in which the image intensifi er remains away from the patient, remove the grid.

10. Be sure that the irradiation fi eld is always kept in the narrowest range possible.

Table 2

Figure 15 ExampleofreductionofpatientskinentrancedoseWhen the X-ray entrance angle is changed by 40°, there is no overlap of exposed skin areas.I.I.:imageintensifier

X-ray tubeX-ray tube X-ray tube

X-ray tube

18


dependingonthepatient’sageatthetimeofexposure.Generally,youngercellsaremoresensitivetoradiation.Radiation injuries are essentially the result of impair-mentof cellproliferationbyX-rays; cellswith shortercycles of proliferation are more radiosensitive thanslowlyproliferatingcellsandrestingcells.Ontheotherhand,therateanddegreeofrecoveryofdamagedtissuesalso affect themanifestationof radiation-induced skininjuries.Itthusremainsunclearwhethertheelderlyareparticularlylikelytosufferskininjuries.2.Bodytype:For patients with thick thoracic cage due to obesity,muscularity,orotherfactors,greaterdosesarerequiredthanfor thinpatientsbecauseof thedecrease inX-raypermeability. Additionally, in obese patients, the posi-tionofthediaphragmisrelativelyhigh,sotheabdomi-nalorgansareoftenincludedintheirradiationfield;theX-irradiation dose is thus further increased. For thesereasons,obesepatientstendtobeexposedtogreaterdos-es,andarehencemorelikelytosufferradiation-inducedskininjury(seeQ12andFigure6).3.Site:The degree of susceptibility to radiation also dependsonwhichpartoftheskinreceivesexposure.AccordingtoKalzetal.thepartsoftheskinmostlikelytoexhibitacuteresponsesarethefrontalsurfaceoftheneckandthebendingportionsof the limbs,suchas theanteriorcubitalregionandpoplitealfossa,followedbythechest,abdomen,face,back,outeraspectsofthelimbs,napeoftheneck,scalp,hands,andankles.Thehairfolliclesaremoresensitivethanotherskinstructures.4.Underlyingdisease:Itisreportedthatradiation-inducedskininjuryisexacer-batedinsystemicsclerosis,systemiclupuserythemato-sus(SLE)andmixedconnectivetissuedisease(MCTD)patients, but no clear correlationhas been established.Diabetesmellitusandhyperthyroidismintensifyradia-tioninjuries.Areportisavailableonapatientcomplicat-edbyMCTDanddiabetesmellituswhosufferedseverenecroticulcerationafter undergoing IVR. Ataxia tel-angiectasia patients with a homozygous genotype areparticularlysusceptibletoradiation.5.Effectsofdrugs:Skin radiosensitivity also increases in the presence ofchemotherapeutics such as actinomycin D, adriamy-cin, bleomycin, fluorouracil (5-FU), and methotrexate(MTX). Ithasbeen reported that even severalmonthsafterhealingofinitialreactionsfollowingX-irradiation,skin injuries recurred locallyonlywith administrationofactinomycinDforseveralweeks.

When the clinical benefits of catheter techniquesare considered very significant and outweigh the riskof radiation-induced skin injury, catheterization for

theexaminationand/or treatmentof the targetdiseaseshould be considered reasonable. It should be noted,however, that obtaining informed consent concerningtheriskofradiation-inducedskininjuryisessential.

66 Strategies for reducing exposure in medical personnel

A Medical personnel exposure

Q24: I’ve heard that regarding operator exposure, the radiation produced from the patient’s body is more important than that from the X-ray tube. What is meant by this?A: Sinceoperatorexposureisforthemostpartduetoscattering of X-rays from the patient, to reduce thedosereceivedbytheoperator,emphasisshouldbeplacedoncontrollingtheX-raysscatteredfromthepatient.Inparticular,minimizingthedosereceivedbythepatientleadstoareductioninthedosereceivedbytheoperator.

Q25: Persons engaged in PCI procedures receive high exposure doses, and I am anxious about the radiation injuries that may result from this. Please describe the radiation injuries that can occur in PCI personnel. How long per year can we be involved in PCI or CAG without injury to our health?A: InPCI,sinceX-rayfluoroscopyisperformedathighdose rates forprolongedperiodsof time, theexposuredoseforthePCIoperator,whoworksinthevicinityofthepatient,ishigherthanthatforotherpersonsinvolvedin interventional radiological procedures. Cataract canoccurfromexposuretoatotalof2Gyormoreoverashortperiodoftime,orfromanexposuretoatotalof5.5Gyormoreover3monthsor longer.Accordingly, theupperdoselimitforPCIpersonnelhasbeensetat150mGy/yearfortheocularlens,and500mGy/yearfortheskin. Prevention and management of exposure shouldbe emphasized to ensure that these upper limits willneverbeenexceeded.Recently, itwasreported thatanAmericanphysicianinchargeofIVRdevelopedocularcataractevenwithradiationexposurethatdidnotexceed2 Gy. “The Chernobyl Cataract Study” has suggestedthat radiationcataractcanoccurevenat relatively lowdosesofapproximately250mSv;thisfindingisconsis-tentwiththeresultsofstudiesofatomicbombvictims,astronauts, and patients undergoing X-ray computedtomography (CT) scan examination of the head. Withtheseconsiderationsinmind,thecatheterizationlabora-torymanagershouldendeavortopreventradiationinju-riesinthemedicalpersonnelworkinginthelaboratory.

Lawsandregulationsstipulatethatthecatheterization

19


laboratory manager must ensure that persons involvedin interventional radiological procedures in cardiaccatheterization examinations and other interventionaltechniqueswillnotbeexposed todosesexceeding thefollowinglimits:1. 100mSvin5years2.50mSvin1year3.Forfemales,5mSvin3months,inadditiontothe

twolimitationsabove4.Forpregnantwomen, inadditiontotheabove,1

mSvofinternalexposureduringtheperiodfromthe time when the hospital or clinic managerbecomesawareofherpregnancyasaresultofherreportingitorothermeanstodelivery

5.Fortheabdominalsurfaceofapregnantwoman,2mSvduringtheperiodspecifiedin4.above

6.Fortheocularlens,150mSvin1year7.Fortheskin,500mSvin1year

Thecatheterizationlaboratorymanagerisrequiredtoensure that the persons involved in radiological medi-calprocedures,includingCAG,carefullyobservethesedoselimitations,nomatterhowmanyexaminationstheyperform.Tothisend,itisimportantthateffortsbemadetoreduceexposurebymakingthebestuseofprotectiveclothingandprotectivedevices,andthatworkerswearpersonal dosimeters such asglassbadges anddo theirwork in an environment controlled to avoid exposureexceedingthedoselimit.

B How to use personal dosimeters

Q26: Personal dosimeters (photoluminescentglass dosimeters and optically stimulated lumines-cent [OSL] dosimeters) are available to wear on the head and chest. Where should we put them on? And if we put them on under protective clothing, where should they optimally be placed?

A: Figure16showsrecommendedpositionsforwearingpersonaldosimeters.DuringPCIprocedures,twodosim-etersshouldbeworn,oneinsidetheprotectivecloth-ingand theotheroutsideof it. For protection insidethe protective clothing, personal dosimeters should bewornontheabdomeninthecaseoffemaleworkers,andon the chest in the case of males and women deemedwithoutthepotentialtobecomepregnant.Outsideoftheprotectiveclothing,personaldosimetersshouldbewornontheheadandnecktomonitorlensexposuredoses.

C Types and effects of protective clothing and effects of lead equivalent

Q27: What type of protective clothing should I wear during PCI? Protectors with lead equivalents of 0.25 mmPb and 0.35 mmPb are available. Please tell me the effi ciency of protection for each type of clothing compared with exposure without protective cloth-ing. Is a 0.35 mmPb protector more effective? Oth-erwise, is a 0.25 mmPb protector suffi cient? A: Regardingprotectiveclothing,thehighertheprotec-tiveperformance is, thebetter, thoughgenerally itemswithhighprotectivecapacityareheavy.Wearingheavyprotectiveclothingcanaffect theoperator’sconcentra-tion,andcancauselumbago.

Thecurrentversionof the Japanese IndustrialStan-dards (JIS) specifies lead-containing sheets with leadequivalentsof0.25mmPb,0.35mmPb,and0.50mmPbasmaterialsforprotectiveclothing.Generally,thegreat-er the leadequivalent is, thehigher theprotectiveper-formance is, though protective clothing becomes pro-portionallyheavierwiththeincreaseinleadequivalent.Figure17Ashowstherelationshipbetweentheshield-ing material thickness and shielding power of pro-tective clothing between 0.25 mmPb and 0.35 mmPbleadequivalents.Figure17Bshowsactuallymeasuredshielding effects in coronary examination. Sufficientshieldingpowerwasobtainedwiththe0.25mmPbleadequivalent,withnosignificantdifferencefoundinthisrespect between 0.25 mmPb and 0.35 mmPb. It isrecommendedthattheoperatorusearelativelylightitemofabout0.25mmPbleadequivalentincombina-tionwithotherprotectivedevices,ratherthancover-inghisorherentirebodysurfacewithheavymate-rial.

Q28: There are various types of protective cloth-ings, including the apron type, which does not include lead in the back; the coat type, which includes lead both in the front and back; and the Figure 16 Positionsforwearingofpersonaldosimeters

Head and neck (outside of protective clothing)

Head and neck (outside of protectiveclothing)

Chest (inside ofprotectiveclothing)

Abdomen (inside of protective clothing)

20


top-bottom separation type. Are there any differ-ences among them in degree of protection from radiation exposure? Which is the ideal type?A: Generally, wearing of protective clothing on theoperator’s back prevents entry of the X-rays producedwhentheoperatorisworkingwithhisorherbacktothepatientinfluoroscopy,andentryoftheX-raysscatteredagainst the patient and further scattered against walls

and equipment. When the back is covered with 0.25mmPbprotectiveclothing,thetissue-absorbeddoseonthe back can be reduced by half or so. However, pro-videdthattheoperatordoesnothavehisorherbacktothepatient,theamountofX-raysenteringtheoperator’sbody from theback isnotmuch, so theeffectivedoseremains almost unchanged. It is thus practical for theoperator towearprotectiveclothingof theapron type,rather than covering his or her body with protectiveclothingofthecoattype,whichisheavyandmayaffectoperatorperformance,andtobecarefulnottohavehisorherbacktothepatientduringtheoperation.Whereasthe apron type places weight mainly on the operator’sshoulders, theweightof the separate type isdispersedover the shoulders and hips, with less induction offatigueandimprovedworkperformance.

D Maintenance and management of protective clothing

Q29: I’ve heard that protective clothing is not damage-resistant. Please explain quality control for protective clothing.A: Protectiveclothingiscomprisedofasheet-likebasematerialuniformlycontaininganelementofhighatom-

Figure 17A ShieldingeffectofprotectiveclothingComparison of 0.25 mmPb and 0.35 mmPb (tube voltage: 120 kV)Comparative data with 1 dose unit received by the operator without protective clothingI.I.:imageintensifier

0.07 Dose Unit

0.25 mmPb 0.35 mmPb

0.1 Dose Unit


Figure 17B Shieldingeffectofprotectiveclothingincoronaryangiography

Comparison of doses on the operator’s chest

0.25 mmPb 0.35 mmPb

30

20

10

0

n=9n=4

Mean: 9.2% Mean: 7.7%

Pen

etra

tion

rate

(%

)

Lead equivalent of protective clothing

21


ic number such as lead, and a sheet of rubber or syn-theticresincoveringthebase.Sinceitistoughenoughthat breakage and tears do not occur readily, it mightbe thought that it can be used on a semi-permanentbasis.However,wearingitcancausephysicalfatigueinthematerial,whichinturncanproducerupturesoftheshielding material inside. Adhesion of liquids such assweat,blood,andcontrastmediacandecreasedurabil-ity.Usually,commerciallyavailableprotectiveclothingbears an expiration date; it is necessary to stop usingtheclothingbeforethatdate,andtoperiodicallyimple-mentqualitycontroltoconfirmthesafetyofprotectiveclothing.

In using protective clothing, the following points ofnoteshouldbeborneinmind.1.Protective clothing does not completely block X- rays.2.If protective clothing isusedbeyond the expiration

datespecifiedbythemanufacturer,safetyshouldbeconfirmedbytheuser’sfacility.

3.When storing protective clothing, avoid foldingand use hangers or hooks capable of keeping itsmooth.

4.Donotplaceexcessivestressonprotectiveclothing(donotleaveitonchairsanddonotsitonit).

5.Wipeoffbloodandcontrastmediaadheringtopro-tectiveclothingwithlukewarmwaterorotherappro-priatedetergentstokeepitclean.

6.Checktheappearanceofprotectiveclothingperiodi-callytoconfirmtheabsenceofbreakageofthecoversheet.

7. It is also recommended that protective clothing bechecked by fluoroscopy periodically to confirm theabsenceofbreakageandlossofprotectivematerial.

E Effects of goggles and neck protectors

Q30: I perform PCI many times everyday, and am curious about my exposure. Please show protec-tive devices, other than protective clothing, that are effective during PCI. If I wear such devices, to what extent will exposure dose be reduced?A: Neckguardsforprotectionof theneckandthyroidgland,protectivespectaclesandgogglesforprotectionoftheeyes,faceguardsfortheface,andprotectiveglovesforthehandsandsimilartypesofprotectiveequipmentareavailable.SomeexamplesareshowninFigure18A.In choosing thesedevices, aswithprotective clothing,avoidthose thatare tooheavy; it isrecommendedthatyou choose ones that do not prove bothersome evenwhenwornforalongperiodoftime.Generally,theangi-ographicsystemhastheX-raytubepositionedbelowthepatient(under-the-tabletype),suggestingthatthedoseto

theupperhalfofthebodyisnothigh.InPCI,however,X-raysaredeliveredoverabroadrangeofdirections,soprotectionoftheupperhalfofthebodyaswellisoftenrequired.

Protective spectacles are a protective device to bewornoverthefacetoprotecttheface,andparticularlytheocularlenses,fromradiationexposure,andaremadeof lead-containing glass or lead-containing acrylicresin.Lead-containingglasspermitsusewithhighleadequivalentvalues,soitcanbeprocessedintoprotectivedevices that are strongly protective, though they areheavy.Lead-containingacrylicresinislightandhighlyworkable,so itcanbefabricatedintoabroadrangeofshapes. However, its transparency is less than that ofglass,soitisdifficulttofabricatewithhighleadequiva-lentvalues.Useofprotectivespectaclesisalsorecom-mendednotonlytoguardagainstX-rayirradiationbutalsotoprotecttheeyesagainstscatteredbloodandotherbodyfluids.

Neck guards are protective devices for protectionof the thyroid gland, and are made of lead-containingsheets,aswithprotectiveclothing.

Figure18Bshowstheprotectiveeffectsof0.07mmPbprotective spectacles made of lead-containing acrylicresinand0.25mmPbneckguardsmadeoflead-contain-ingsheets.Evenrelativelythinprotectivespectaclesof0.07mmPb leadequivalenthaveaprotectiveeffectofabout60%.The0.25mmPbneckguardsmadeoflead-containingsheetshaveaprotectiveeffectofabout90%,aswithprotectiveclothing.

F Protective devices recommended for installation in the imaging laboratory and how to use them

Q31: Please describe the variety of protective devices that are helpful in the catheterization labo-

Figure 18A Protectivedevices

Protective spectacles: goggle type (0.07 mmPb)

Neck guard

22


ratory where PCI is performed, and show where to set them for effective use and how to use them.A: Whenaprotectivedeviceisattachedtotheimagingsystem,medicalpersonnelcanlessentheirfatiguesincewearing lightweight protective clothing is sufficientto obtain the desired protection. If a single protectivedevice is used to obtain all protection, the increasedoverallsizehampersmovementofthesystem’sarmandcatheter table, so it is recommended that a number ofprotective devices of various shapes be combined asappropriateforthepatient’sposition.Protectivedevicesrecommendedtobeinstalledinthecatheterizationlabo-ratory room are shown below. Their appearances andshieldingeffectsareshowninFigures19Aand19B.Itcanbeseenthatcombiningthethreetypesproducesastillbroaderrangeofshieldingeffect.1.Typeforprotectionofthelowerhalfoftheoperator’s

body(rubbershield) Thesearemadeoflead-containingrubber,tobesus-

pendedfromthecathetertable.2. Typeforprotectionoftheoperator’sabdomen

(L-shapedprotector) L-shaped protective devices for insertion between

the catheter table and the patient’s back are bothradioprotective and function as a patient arm rest.Although the protective effect increases with theheightof the screenportion,workabilitydecreases.ThedeviceshowninFigure19is15cmhigh.

3.Typeforprotectionoftheupperhalfoftheoperator’sbody(protectiveacrylicglass)

Lead-containing acrylic panels attached directly toceilingsorplacedonceilingrailsarecommonlyused.Ifapanelofthistypeisplacedonaceilingrail,abroadrangeofmotionisobtained;however,sinceitcaninter-fere with the image intensifier and other equipment atsomeanglesof the system’s arm, caution isneeded in

handling the panel. X-ray exposure to the operatorcomesforthemostpartfromsecondaryX-raysscatteredagainstthepatient.Forthisreason,theprotectivepaneliseffectiveifplacedbetweenthepatientandtheopera-tor (notbetween theoperatorand theX-ray tube),andasclosetothepatientaspossible.Figure20showsanexampleofplacementformaximumeffect.

G Dose distribution in the catheterization laboratory

Q32: Please show the dose distribution in the cath-

Figure 18B EffectsofprotectivedevicesComparative data with 1 dose unit received by the operator without each protective deviceI.I.:imageintensifier

0.4 DoseUnit 0.1 Dose

Unit

Neck guard (0.25 mmPb)Protective spectacles (0.07 mmPb)

Figure 19A Protectivedevicesattachedtotheinstrument

Protective acrylic glass

L-shaped protector

Rubber shield

23


Figure 20 Effectivepositionofguardscreen(arrow)

eterization laboratory during PCI.A: Sinceknowledgeofthedosedistributioninthecathe-terizationlaboratoryallowssmoothoperationwithlowerexposure doses, it is important that medical personnelenteringthelaboratorybeawareofthisdistribution.1. Dose distribution during fl uoroscopy

Figures21A,21B,and21Cshowthedosedistribu-tions forvariousdirectionsofentryofX-rays. InPCI,X-raysareprojected fromdifferentdirections, and thedosedistributionchangeswitheachchangeindirection;however, ingeneral,greaterdosesaredeliveredonthesidewheretheX-raytubeispresent.Hence,thedoseisgreateron thepatient’s left side in theRAOdirection,andonthepatient’srightsideintheLAOdirectionandleftlateraldirection.2. Dose distribution during imaging

The dose rate is more than 10 times greater duringimaging than during fluoroscopy (Figure 21D). Evenintheperipheralareasofthecatheterizationlaboratory,wherethedoserateisrelativelylowduringfluoroscopy,thedoserateoccurringduringimagingiscomparabletothatobservedat theoperator’spositionduringfluoros-copy.Itisrecommendedthatmedicalpersonnelworkinginthecatheterizationlaboratoryuseaguardscreendur-ingtheimagingprocedure,orleavethelaboratory.

Taking into account these dose distributions, ICRPPubl.85(AvoidanceofRadiationInjuriesfromMedicalInterventionalProcedures)recommendsthattheopera-torstandontheimageintensifierside.However,thisis

oftenimpossibleorunrealistic,dependingonthetypeofexaminationandtheshapeofthesystem.Itisfeasiblefortheoperatortostandontheoppositesideoftheimageintensifierwithappropriateprotectivedevices.

H Pregnancy of female medical personnel

Q33: I am a female physician who performs angi-ography, and have become pregnant. What actions should I take?

Figure 19B EffectsofthreeprotectivedevicesattachedtotheinstrumentOutlined areas indicate 50% shielding areas on horizontal cross-sections 50 cm, 100 cm, and 150 cm above the fl oor

Protective acrylic glass

Protective rubber shield

L-shaped protector

50 cm above floor

Protective acrylic glassProtective rubber shieldL-shaped protector

100 cm above floor 150 cm above floor

24


A: First,youneedtoinformthefacilitymanagerofyourpregnancy.Themanagermustensurethatfetalexposuredoesnotexceed thedose limit.Lawsand legulationsstipulate that the upper limit of equivalent dose ontheabdominalsurfaceduringgestation,betweenthetimeofestablishmentofthediagnosisofpregnancyanddelivery, is2mSv. It isalso legally required thatrecordsbekeptontheequivalentdoseontheabdominalsurfaceof themothereverymonthand thecumulativedoseoverthegestationalperiod.Inthecaseoffetuses,publicdoselimitsapply,sothecumulativeabsorbeddosereceivedbythefetusduringtheperiodfromfertilizationtodeliveryshouldnotexceed1mSv.However,althoughlawsandregulationsindicatethattheexposurestatusofpregnantfemalemedicalstaffmustbeadequatelyman-aged,theydonotrequirepregnantwomentocompletelyavoidworkinvolvingtheuseofradiationorradioactivesubstances,nordotheyprohibitthemfromaccessing,orworkingin,specifiedareaswithradiationexposure.Itisimportantthatthepersonsconcernedarealwaysawareofthesefactswhileatwork.

Itisrecommendedthatthemanagerkeepavailableforfemaleworkersaformfornotificationofpregnancytothemanagerorequivalentindividual,andobtaininfor-mationoneachpregnantworkersoastosecureagoodworkenvironmentforthem.Inallcases,uponlearningofthepregnancyofafemalemedicalstaffmember,themanager must consult with her closely to ensure thatshewillbeable todoherworkcomfortablywhilesheispregnant.

I Education and re-education of medical personnel

Q34: What are the legal requirements concerning education and re-education related to radiation for physicians, nurses, and radiologic technologists engaged in PCI?A: According to the Laws Concerning the PreventionfromRadiationHazardsduetoRadioisotopesandOth-ers,MinistryofHealth,LabourandWelfare (MHLW)

100 cm above fl oor

100 cm above fl oor

P-A:posterior-anterior,RAO:rightanterioroblique,LAO:leftanterioroblique

100 cm above fl oor

100 cm above fl oor

Figure 21A Dosedistributioninthecatheterizationlaboratory(directionofX-rayentrance:fluoroscopyinP-Aview)

Figure 21B Dosedistributioninthecatheterizationlaboratory(directionofX-rayentrance:fluoroscopyinRAO30°view)

Figure 21D Dosedistributioninthecatheterizationlaboratory(directionofX-rayentrance:imaginginP-Aview)

Figure 21C Dosedistributioninthecatheterizationlaboratory(directionofX-rayentrance:fluoroscopyinLAO60°view)

25


OrdinanceonPreventionofIonizingRadiationHazards,theRulesoftheNationalPersonnelAuthority,andsimi-larlawsandlegulations,educationandtrainingofmedi-calpersonnelinradiologyismandatory.Inadditiontothemandatoryeducation/traininginradiology,individu-alswhoareengagedindutiesinvolvingthedeliveryofradiationtopatientsmusteducatethemselvestoobtainknowledgeandexpertiseproactivelytoensuretheirownandtheirpatients’safety.TheMHLWOrdinancestipu-latesthatspecialeducationconcerningradiationsafetybeprovided forpersonsengaged inoperationofX-raysystems.

[Items for education and training]1.Effectsofradiationonthehumanbody[30minutes]2.Safehandlingofradioisotopesandradiationgenera-

tors[4hours]3.Laws and regulations concerning the prevention of

radiationinjuriesduetoradioisotopesandradiationgenerators[1hour]

4.Rulesonpreventionofradiationinjuries[30minutes]

Note that for those with adequate knowledge andskills,allorpartoftheeducation/trainingprogramsmaybeskipped.

[Frequency]The Laws Concerning the Prevention from RadiationHazardsduetoRadioisotopesandOthersindicatesthathealthcareprofessionalsinradiologyshouldbeeducatedand trainedoncebefore theirfirst access tocontrolledareas,andeveryperiodthatdoesnotexceed1yearaftersuchaccess.

J Requirements for labor accident indemnifi cation approval

Q35: Please show the requirements for labor acci-dent indemnifi cation approval in case of the onset of cancer in a healthcare professional in radiology.A: If a person engaged in radiological practice devel-opsa radiation injurydue to radiation receivedduringradiation-relatedwork,heorshecanreceivecompensa-tion formedical care and the likebasedon theWork-ers’AccidentCompensationInsuranceAct(fornationalpublic officers, the National Public Officers’ AccidentCompensationActapplies).Regardingtherequirementsfor approval, criteria are available for acute radiationsyndrome,acuteradiation-inducedskininjuries,chronicradiation-inducedskininjuries,radiation-inducedhema-topoieticdisorders,leukemia,andcataract.Forexample,oneoftherequirementsforapprovalforleukemiaisanonset of illness later than 1 year after exposure, with

confirmation of the fact that the sufferer received acumulativedoseof5mSvormoreperyear.

77 Management of imaging systems

A Maintenance and management of imaging systems

Q36: Please show the points to note for users of angiographic systems in maintaining the quality of such systems.A: The amount of X-rays that a patient is exposed tocannotbekeptconstantunlessthetubevoltageandtubecurrent are constant. Variation in X-ray quality influ-ences theonsetof skin injury inpatients,and thesizeoftheirradiationfieldiscloselyrelatedtobothpatientandoperatorexposuredoses.Inensuringthesafetyofangiographic systems and maintaining good qual-ity and performance, it is important that not onlyself-inspections but also periodic maintenance andinspectionsbeimplementedbythemanufacturersofthesystems.Inparticular,thebrilliancyofimageinten-sifiers decreases over time, so if reduced brilliancy isleftasis,theautomaticexposuremechanismwilladjustthedose,resultingindeliveryofagreaterexposuredosetothepatient.Althoughdosevariationamongdifferentinstitutionsmaybedue,inpart,tointrinsicfeaturesofthesystemsused, thestatusof implementationofdoseadjustmentduringsysteminspectionsmayalsoaffectit.Itisimportantthatontheoccasionofperiodicinspec-tions,thebrilliancyoftheimageintensifierbemeasured,andthattheirisdiaphragmandothercomponentsaffect-ing thequalityof imagesbeadjustedwheneverneces-sarytopreventthedosefromincreasing.

Notethatifthebrilliancyfallsbeyondtheadjustablerange,increaseinthedoseirradiatedtothepatientwillbeinevitable;replacementoftheimageintensifiermustthenbeconsidered.

TheJapanIndustriesAssociationofRadiologicalSys-tems(JIRA)hasspecifiedtwocasesinwhichtheimageintensifiershouldbereplacedwithanewone:1. Incasesinwhichthereferenceconditionsasofthe

timeofinstallationcannotbemaintainedevenafteradjustment,andtheexposuredosehasincreasedby50%ormorefromtheinitiallevel.

2. IncasesinwhichtheX-rayconditionsasofthetimeofinstallationcanbemaintainedbyadjustment,butthediagnosticperformancehasevidentlydecreasedfromtheinitialleveltoanextentthathampersdiag-nosis.

26


B Measures to reduce exposure

Q37: I’ve heard that new angiographic systems are provided with a number of functions for ensuring the safe performance of PCI. When such a system is used, don’t skin injuries occur in the patient?A: Recently developed angiographic systems suitableforPCIareprovidedwithdigitizedfeaturesandmanyPCIaid functionsas shownbelow.These functions, ifutilizedeffectively,enabletheoperatortoperformPCIsmoothlywhilereducingbothpatientandoperatorexpo-sures.1.Low pulse rate fluoroscopy function is included to

reduceexposure.2.A supplementary filter to reduce exposure is pro-

vided.3.Map image display and roadmap functions for

smoothadvancementofthecatheterandguidewiretothetargetsiteareincluded.

4.Imagestorageandretrievalarefacilitatedbydigitalimageacquisition.

5.Digital fluoroscopy is available, offering good vis-ibilityoftheguidewireandstent.

Itshouldbeunderstood,however,thatthesefunctionsnever ensure the prevention of skin injuries, althoughtheyincludemeasurestoreduceexposure.Becauseerro-neoususecanleadtoirradiationathigher-than-expecteddose rates, it is important that the user have a clearunderstanding of these performance features beforeusingthem.

88 Non-coronary intervention

A Precautions in head and neck IVR

Q38: Please show the points to note for head and neck IVR, such as in internal carotid artery stenting.A: Theheadhashair:Whichisasignificantdifferencefromtheskinofthetrunkirradiatedduringcardiacinter-vention.Exposuretodosesexceeding3Gycancausetemporaryepilation.Evenwhenitistemporary,epila-tioncanhaveamajormental impactonthepatient,soyoushouldalwaysbesuretotheextentpossibletoavoidirradiationofthesamesiteintheheadforaprolongedperiodoftime.Becausedirectexposureofthepatient’seyestoX-rayscaninducecataract,shieldingandirra-diationanglemustbetakenintoaccount.AccordingtoICRPPubl.85,thethresholddoseforcataractcausedbyasingleexposureis2Gy;thisdocumentalsosuggeststhatexposureto5Gyormoremayproduceprogressive

change. In ICRP Publ.60, it is stated that lens opacitywithoutvisualimpairmentcanoccurevenwithexposureof 0.2 Gy or less, so prolonged irradiation of the lensmusttotheextentpossiblebeavoided.

B Precautions in percutaneous transluminal angioplasty (PTA) in lower limbs

Q39: Please show what to note during lower limb PTA.A: PTAisaneffectivemeansoftreatmentforarterio-sclerosisobliterans(ASO),andthenumberofcases inwhich it is performed is steadily increasing in Japan.SincepatientswithischemicheartdiseaseoftendevelopASOasacomplication,cardiologistsarenowmorecom-monlyengagedinitstreatment.Becauseoftheproximityofthepuncturesiteandthetreatmentsite,theoperatorisexposedtorelativelylargeamountsofscatteredX-rays.In addition, a large-diameter image intensifier isoftenused,andproduces largeramountsof scatteredX-raysthanasmall-diameter image intensifier. Inperformingexamination for PTA, it is important that the irradia-tionfieldbenarrowedtothemaximumpossibleextentrequired,andthattheappropriateimageintensifiersizebeused.

Becausethetargetvesselsareoftendelineatedintheposterior-anterior views rather than the oblique viewscommonly used in PCI, protective rubber shields andprotectiveacrylicglassequippedwiththeradiationsys-temortheexaminationroomareeffective(Figure19A).Itisrecommendedthattheoperatorobtainradioprotec-tionusingtheseprotectivedevices.

99 Electrophysiological examinations and treatments

A Exposure doses to patients undergoing catheter ablation

Q40: What are the distinct features of radiation exposure in electrophysiological examinations and treatments, such as catheter ablation and pace-maker implantation compared with those in PCI? Are there any aspects of such procedures that require special attention as regards protective measures?A: Inelectrophysiologicalexaminationsandtreatments,fluoroscopy is mainly used, with imaging performedonly minimally. In addition, since catheter electrodes,whicharemoreeasilyrecognizablethanguidewires,are

27


used,itiscommonpracticetoperformtheexaminationatreducedfluoroscopypulserates.ThesefeaturesofferprotectiveadvantagescomparedwithPCI.Itshouldbenoted,however, thatsincecatheterablation is likely toinvolvecontinuousfluoroscopyatafixedX-rayentranceangle, irradiation of the same site is often prolonged.IncaseofalongperiodofirradiationintheLAOposi-tion, inparticular, concentratedexposurecanoccur inthe right subscapular regionandrightupper limb;special caution is required with regard to this. Effortsshouldbemadetouselowpulseratefluoroscopy,andtokeeptheupperarmsawayfromtheirradiationfield,by,forexample,distancingtheupperarmsfromthetrunkasfaraspossible.

B Precautions for pediatric patients

Q41: What are the points to note for pediatric patients? I’ve heard that paralysis can occur when the upper limbs are placed in a raised position for a long time. Is there any effective method of prevent-ing this?A: Whenapediatricpatientundergoescatheterizationor intervention under general anesthesia, frontal andlateralviewsusingbiplanefluoroscopyareoftenused;tosecureafieldforlateralfluoroscopy,theupperlimbsare sometimes immobilized while raised. Prolongedimmobilizationcancauseinjuriestothebrachialplexus,brachial nerve, ulnar nerve and other nerves which inturncanresultinparalysisandhypesthesiaintheulnarside of the palm, as well as distal from the shoulderjointsorcubitaljoints.Thisisattributedtoulnarnervehyperextensionduetoelbowabductionundertheweightofthearm,ortodamagetotheentirebrachialnerveduetoaxillaryhyperextension,asa resultof inappropriateimmobilization.Althoughsignsandsymptomssuchasmotor paralysis and hypesthesia are for the most parttransient,recoverycantake6monthsorlongerinsomecases. This can be prevented by avoiding immobiliza-tion in a constant limb position. If immobilization isunavoidable,itisrecommendedthattheimmobilizationbeloosened,withupperlimbadduction,toachievetran-sientdecompressionofthenerves,atintervalsofabout30to60minutes.

1100 Nuclear imaging

A Precautions in performing PCI on the same day as thallium (Tl)myocardial scintigraphy or the following day

Q42: Please indicate the precautions in perform-ing cardiac catheterization on the day of or the day after Tl scintigraphy to evaluate myocardial viability. What issues exist concerning the risk of radiological exposure due to isotopes remaining in the patient’s blood and catheter devices?A: Because the amounts of isotopes administered tothepatientinnuclearimagingaresmall,itisgenerallybelieved that cardiac catheterizationposesnoproblemrelatedtoexposureoftheoperatorandotherstaffevenwhenitisperformedonapatientwhoreceivedaniso-topeonthesameorthefollowingday.However,becausethe patient’s blood contains a residual portion of theisotope, although it may be quite small, the injectionneedles, catheters, and related equipment used in thecardiac catheterization may be contaminated. For thisreason, used disposable instruments should be storeduntiltheirradioactivitylevelbecomesundetectablewithacounter,and thendisposedofas infectiouswaste. Inaddition,sinceisotopesareexcretedathighlevelsintheurine,thepatient’surineshouldbehandledwithgreatercarethantheblood.Theurinalbagsanduseddiapersofpatientsundergoingnuclearimagingshouldbehandledinthesamefashionascathetersandinjectionneedles.

B Exposure of medical personnel engaged in Tl myocardial scintigraphy

Q43: I perform intravenous injection of isotopes during Tl myocardial scintigraphy. What is the extent of exposure of my fi ngers and body? Is any method available to reduce this exposure?A: Accordingtoa1995surveybytheJapaneseSocietyofNuclearMedicineTechnology,exposuredosestothetrunk of radiologic technologists involved in nuclearimagingwere≤ 0.2mSv/monthin≥ 75%oftheinstitu-tionsthatparticipatedinthesurvey,whereastheexpo-suredosestothefingersexceeded0.5mSv/monthinasmanyas30%of the institutions.Manyof the recentlylaunchedisotopesaresuppliedinshieldedsyringeswithtungstenandleadglass.Assuch,greaterconsiderationisgiventoreductionofexposureofmedicalpersonnelthanever,althoughnoshieldingisprovidedontheinjection

28


needlesideandtheplungerside.Actualmeasurementsshowedthattheplasticmaterialusedontheplungersidehadonlya lowshieldingeffect.Evenwhena tungstenplungerwasused,theshieldingeffectestimatedfromtheleakageratewasabout75%fortechnetium(Tc)-99m.Inhandlingtheshieldedsyringesaswell,quickandappro-priateperformanceofproceduresisaneffectivewaytoreduceexposurefromisotopesusedforscintigraphy.

C How to handle subcutaneous leakage of isotopes

Q44: I have erroneously injected an isotope into subcutaneous tissue of a patient during myocardial scintigraphy. Please tell how to handle this.A: Subcutaneousleakageonintravenousinjectionisnotrare in the clinical setting. If a subcutaneously leakedisotope remains localizedat thesite, it ispossible thatthelocaltissuewillabsorbahighdose,indicatingthatcautionisneededeveniftheisotopehasashorthalf-life.InacasereportedinJapan,Tl-201leakedfromsubcu-taneous blood vessels during myocardial scintigraphy;despite immediate treatment, the portion of the skinaroundthesiteofleakagenecrotized2weekslater,fol-lowedbyulcerationwithscarepithelialization3monthslater,andseverescarring,depigmentation,skinatrophy,vasculardilation,andperi-pigmentationinthecenteroftheaffectedpart4yearslater;chronicradiationderma-

titiswaseventuallydiagnosed.Ifleakageofanisotopeisdetectedduringexamination,itisimportantthatthemaximumexpectedskin-absorbeddoseberoughlycal-culatedby,forexample,quicklyobtainingimagesofthesiteofleakagetoobtaindoseinformation,andthatthepatientbefollowedovertime.

1111 CT

A Exposure dose to patients undergoing coronary CT

Q45: Recently, evaluation of coronary lesions by multi-detector computed tomography (MDCT) has become increasingly common. What is the average exposure dose in such cases? How about a com-parison with CAG?A: AcommonlyusedimagingprotocolforcoronaryCTisasfollows:1. Scanography:Obtainanapproximateimagingrange.2.Scout scan for positioning: Determine the range of

scanforcontrastimaging.3.Scan to determine appropriate timing of contrast

imaging scan (Real Prep): After intravenous injec-tionofcontrastmediumatarateof3to4ml/s,thescanisrepeatedatconstantposition.Whilemonitor-ingtheCTvalueoftheregionofinterest(ROI)setin

Figure 22A ComparisonofpatientexposuredosesincoronaryangiographyandcoronaryCTImaging conditions: scanography 120 kV, 10 mA; positioning scan, 135 kV, 300 mA, pitch 1.0; Real Prep, 135 kV, 50 mA; contrast-enhanced helical scan, 135 kV, 450 mA, pitch 0.19AngiographicdatacourtesyofKanazawaUniversityCT:computedtomography,I.I.:imageintensifier

22.5 mGy

11.5 mGy

120 kV 200 mA 1.0 sec

110 kV　 5 min

23 mGy

127 mGy

29


theascendingaortaorcardiaccavity, the timing tostartcontrast-enhancedhelicalscanisdetermined.

4.ECGgated,contrast-enhancedhelicalscan:Theheli-calscandataareobtainedwithsimultaneousrecord-ingoftheECG.

DosesinaphantomwhoseimagesweretakenusingthisprotocolareshowninFigure22A.

The dose received by the patient is greater in coro-naryCTthaninordinarychestCT.InordinaryCAGfordiagnosticpurposes,themaximumskinentrancedoseisseveralhundredmGy,andcoronaryCTpro-ducessimilardoses.IncoronaryCT,itisnecessarytochooseasthinaslicethicknessaspossible(0.5mm)toobtainhigh-resolution three-demensional (3D) images,andtochooseasmallhelicalpitch(HP)toobtainimagesinmultipletimephases.Figure22Bshowstheresultsofobservationofscantraceswiththreedifferentpitchesinaphantomwithafilmplacedaroundit.Althoughsmall-er HPs produce more dense images, they also pro-ducegreaterdoses.ThisisthereasonwhythepatientreceiveslargerdosesincoronaryCT.

Figure22CshowsdosedistributionsinCT.InCAG,thehighestdoseoccursontheskinsurfacewhereX-rayshaveentered.InCT,thedoseinthecenterofthebodyisnotwidelydifferentfromtheskinsurfacedosebecausethetrunkisirradiatedcircumferentially.Forthisreason,withthesamemaximumdose,agreatereffectivedoseisproducedinCT,wheresimilardosesareirradiatedovertheentireimagingarea,thaninCAG,wheredosesarelocalizedontheskinsurface.TheriskofcarcinogenesisthusappearstobehigherwithCT.However,itremainsunclearwhetherthisdifferenceisclinicallysignificant.

Figure 22B ImagesonfilmplacedaroundaphantomDarker colors indicate higher doses.(tube voltage 120 kV, 10 mA, 0.4 s/rotation, slice thickness 5 mm)HP:helicalpitch,CTDIvol:volumecomputedtomographydoseindex

HP ＝ 1.438（CTDIvol：0.4 mGy）



Unit of measurement: mGyChest CT Coronary CT

Q46: Does the exposure dose vary depending on the patient’s body type in CT as in CAG? Is this variation clinically problematic?A: WhenCTimagesaretakenunderthesameconditions,patientsofsmallerconstitutionreceivegreaterexposuredoses.Figure23comparesdosesinthecentersof,andaround,twophantoms16cmand32cmacross,respec-

Figure 22C ComparisonofdosesreceivedbyapatientundergoingchestCTandcoronaryCTDatacourtesyofFujitaHealthUniversityCT:computedtomography

30


tively, imaged under the same irradiation conditions.Because the X-rays used for diagnostic purposes onlyminimally permeate the patient’s body and lose muchof their energy, irradiation under the same conditionsproducesgreatermeanabsorbeddosesinlighterthaninheavierpatients.Inaddition,patientsofsmallerconstitu-tionexhibitsmallerdosedifferencesbetweenthecenterand surrounding area, and hence receive higher dosesat any position on the phantom; irradiation conditionssuitablefor thepatient’sbodytypeshouldthereforebechosenbeforeobtainingimages.Whenachildisbeingexamined, inparticular,measures topreventexcessiveirradiation,suchasreducingthetubecurrent,shouldbetaken.Automatic irradiationcontrol,afunctionwidelyusedrecentlytoallowautomatedadjustmentsofirradia-tionconditionsaccordingtotheacquisitionsitebasedonscoutviews,isexpectedtofacilitateimagingatappro-priatedoseswithoutaffectingimagequality.

B Effects of the use of multi-row detectors

Q47: Does the patient exposure dose increase with the number of detectors in MDCT? What is the difference in exposure dose from ordinary CT in major blood vessels?A: Basically,provided that theslice thicknessandHPare thesame, thedosereceivedby thepatient is thesameirrespectiveofthenumberofdetectorarrays.

Compared with ordinary CT, there is no notable dif-ference. In MDCT, however, images are sometimesacquiredwithsliceoverlapstoobtainclear3Dimages.Insuchcases,greaterdosesareabsorbedintheregionswherescansoverlap.

C Effects on pacemaker and implantable cardioverter defi brillator (ICD)

Q48: What are the points to note in performing CT examination on a patient with a pacemaker or ICD?A: Itwasrecentlyreportedfrommorethanoneinstitu-tion that partial resets occurred during CT of patientswithanimplantedpacemakerorICD.Thiswasattrib-uted to unwanted currents produced as a result of aphotoelectriceffectinducedbyirradiationoftheCMOScircuit, which amplifies the electrical excitation of theheart.Asaresult,inpatientswithapacemaker,transientsuppression of pacing pulse output due to oversensingcanleadtocardiacarrest.InICD,thedefibrillatorcanoperateerroneouslyduetooversensing.

IfCTordeliveryofarelativelyhighdoseofradiationisperformedonapatientwitheitherdeviceimplanted,attentionshouldbepaidtothefollowing:1. Howtohandlepacemaker-relatedproblems•Donotirradiatetheimplantationsitefor5secondsor

longer.•IfanX-raybeammustbecontinuouslydirectedatthe

implantationsitefor5secondsorlonger,takeappro-

Figure 23 ComparisonofexposuredosesforpatientsofdifferentbodytypesincoronaryCTIrradiation conditions: 120 kV, 200 mA, 1.0 secCT:computedtomography

22.5 mGy37.7 mGy

34.5 mGy 11.5 mGy

Phantom diameter: 16 cm Phantom diameter: 32 cm

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priatemeasures todistance the irradiation site fromthepacemakerasmuchaspossible,suchasaskingthepatienttoraisebothofhisorherarms.

•Ifirradiationofthistypefor5secondsorlongercan-notbeavoided,performtheexaminationinthefixedpacingmodewithoutcompetitivepacing,orprepareforexternalpacingincaseofpacemaker-relatedprob-lems.

2.HowtocopewithICD-relatedproblems•Donotirradiatetheimplantationsite.• IfX-rayirradiationoftheimplantationsiteisunavoid-

able, takeappropriatemeasures todistance the irra-diationsitefromtheICDasmuchaspossible,suchasaskingthepatienttoraisebothofhisorherarms.

• Ifirradiationofthistypecannotbeavoided,performtheexaminationonlyafterturningoffthetachycardiadetectionfunction.

•Bepreparedtouseantemporaryexternaldefibrillatororaexternalpacingduringtheexamination.

Inallcases,aspecialistcapableofrespondingquickly,includingresetcancellation,shouldattendtheexamina-tion,anditisessentialthatthepulsebemonitoredviaanECGmonitor.

1122 Examination and treatment of pregnant patients

Q49: What are the points to note in catheterization studies of pregnant women in the middle gesta-

tional stage or later?A: Irradiationofpregnantpatientsshouldbeavoidedtothe extent possible. Since maternal health benefits thefetus, any required examination should be performedwithduecautionconcerningthemattersindicatedbelow.In such cases, it is important that adequate informedconsentbeobtainedfromthepatientafterafullexplana-tionofthepossibleeffectsonthefetusandotherrelatedmatters,andthatthedosereceivedbythefetusbelim-itedto100mGyor less.Whenthe irradiationfield isinthelowerabdomen(directexposureonthefetus),orwhenacatheterizationstudyofthepelvisisrequired,itisnecessarytoconfirmtheneedforexamination,andtodeterminewhethertheexaminationcanbedelayeduntiltheendofgestation.Inexaminationsinwhichthedosereceivedby the fetus is likely tomarkedlyexceed100mGy,amethodofexaminationnotinvolvingtheuseofradiationshouldbeconsidered.

Tominimizethedosetowhichthefetusisexposed,thefollowingshouldbenoted.1.Inexaminationofpartsofthemother’sbodyrelative-

lyfarfromthefetus,suchasthechest,upperlimbs,andhead,acatheterinsertionsitethatdoesnotcausedirect exposure of the fetus to irradiation (cubitalartery,radialartery,etc.)shouldbechosen.

2.Rigoroususeofcommontechniquesforreductionofexposure(e.g.,lowpulseratefluoroscopy,limitationoftheirradiationfield,useofasupplementaryfilter,andshorteningofthedistancetotheimageintensi-fier).

3.Determinethedosetowhichthefetusisexposed.

[digest version] guidelines for radiation safety in interventional...

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