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TRANSCRIPT
International Radiation Protection Association11th International Congress
Madrid, Spain - May 23-28, 2004
Refresher Course
Radiation Protection in Cardiac and Interventional Procedures
C. Reek
IRPA 11 Refresher Course 2
Overview
• Introduction and Background• Regulations• Dose• Patient Dose Reduction-Factors• Special Cases• Limitation of Staff Dose• Good Practice• Recommendations
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Sources of Radiation
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November 8th 1895
Wilhelm Conrad Röntgen
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• 23rd January 1896• Public lecture on X rays• Hand of von Kolliker
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First British Radiographs
• 25th January 1896• BMJ Alan Campbell Swinton
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British Medical Journal 18th April 1896
• First published report of the dangers of X rays
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1921
• Deaths attributed to X rays
• No regulations prior to 1928
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Stochastic (Random) Effects
1 in 83,333Majority of NHS staff (<0.3mSv/yr)
1 in 25,000Cancer from radiation exposure of 1 mSv
1 in 43,500Accidents at work
1 in 9500Accidents on road
1 in 850Natural causes (40 yr old)
1 in 200Smoking 10 cigarettes/day
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Deterministic Effects
>25 to eye>250 to eye>5Cataract5050010Telangiectasia
9090018Dermal necrosis
7070014Dry desquamation
353507Permanent epilation
<<11002Transient erythema
Mins fluoro0.2Gy/min
Mins fluoro0.02Gy/min
Threshold Dose to Skin
Injury
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Development of Interventional Cardiology
1929First documented human
cardiac catheterisationEberswald, GermanyDr Werner Forssman
1958Diagnostic coronary
angiogramDr Mason Sones
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Development of Interventional Radiology
1964Transluminal angioplastyDr Charles Dotter
1967Judkins techniqueDr. Melvin Judkins
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Development of Interventional Cardiology
1974
First peripheral balloon angioplasty
Dr Andreas Gruentzig
1977
First cath lab PTCA on awake patient
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Development of Interventional Cardiology
1980Use of angioplasty in
evolving myocardial infarct
Dr Geoffrey Hartzler
1987First use of coronary stents
in human
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• Transplant post-biopsy
9.9 x 24.6 mm det. balloon
Embolisation: detachable balloon occlusion
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Regulations
• Ionising Radiation Regulations 1999-relate to public and staff safety
• Ionising Radiation (Medical Exposure) Regulations IR(ME)R 2000
-govern the fate of patients undergoing a medical exposure
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Regulations
• Duties of all bodies- employer, practitioner, operator and referrer
• ALARA/ ALARP principle• Training• Diagnostic Reference Levels (DRLs)• Local Rules-policies, procedures, protocols• Other Bodies eg NRPB, ICRP, ACC, BCIS,
European Commission’s Radiation Protection Research Program
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Dose Definitions
• Gray - energy absorbed per unit mass(in diagnostic = KERMA, energy transferred)
• Sievert - equivalent dose=absorbed dose x radiation weighting factor
• Effective dose – equivalent dose in each organ and tissue x tissue weighting factor and summed over whole body
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Dose Definitions
• DAP - dose area product (Gycm²)incident dose x area of X ray field
• Entrance skin dose – absorbed dose in the skin at a given location on the patient (Gy)
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Annual Dose Limits
1 mSv1 mSvFetus50 mSv150 mSv500 mSvOrgans
15 mSv50 mSv150 mSvEyes
1 mSV6 mSv20 mSvWhole body
PublicUnclassified / trainees
Classified Staff
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Monitoring
Ensure
• Film badges and TLDs are easily available
• Results of monitoring are available to all
• Reminders to wear them are in appropriate places
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Dose to patient
13.07070CA + ad hoc PTCA + stent
9.04920PTCA + stent
9.35060CA + ad hoc PTCA
6.93760PTCA
5.63040Coronary angiography
ED mSVDAP cGycm²Procedure
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Diagnostic Reference Levels
• Set for categories of procedures – 20/annum• At least 100 cases• DAP (dose area product) or screening time and
mAs• Level set - 90th percentile• No national DRLs for coronary angiography• NRPB – proposed 36 Gcm²• European DIMOND – proposed 45 Gcm²
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Dose Reduction - Equipment
• Frame rate selection• Pulsed fluoroscopy• Fluoroscopy and image
acquisition dose rate selection
• Last image hold• ‘Replay fluoro’• Electronic magnification• Image processing• Flat panel detectors
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Dose reduction -Equipment
• Road map• Reload facility• Virtual collimation• Intelligent filtration• Dose display
BUT• Most dose reduction
features optional• Improved imaging allows
more complex cases
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Dose Reduction - Equipment
• Modification of existing equipment• Equipment maintenance • Quality assurance
regular IQ and dose checksmanufacturermedical physicists
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Factors affecting exposure
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Inspiration
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Operational Factors
• Arterial access• Oblique views
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Operational Factors
• Suitable kV and mA
• Centring
• Diaphragms-ROI
• Field size -panning
• Magnification
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Appropriate Views
Views should not be prescriptive-depend on patient
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Lateral View
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Operational
• Stenting strategy
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Behavioural
• Table and detector in correct position before screening
• Screening time• Image acquisition –operator / radiographer?• Use of equipment features-dose reduction
programmes etc• Prolonged procedures – reduce skin dose• Operator fatigue
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Radiation Awareness
• Regular audit• Feedback on dose information
patientsstaff
• High standards of equipment maintenance and quality assurance
• Appropriate theoretical training with annual updates
• Practical training and regular re-assessment
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Audit - Operator key
0
1
2
3
4
5
6
7
8
9
Ave . scr. Tim e
Operator Key
1 2
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31 32 33 34 35
36 37 38 39 40 41 42
TOTAL - REG TOTAL - ALL
3 4 5 6 7
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Audit
1513
0 0
23
323740
15
24
46
37
27
0
32
9
1
434342
030 0
47
0
25
40
79
3 2
21
2927
6 5
55
4
0
10
20
30
40
50
60
70
80
No.
No. of cases
Left Heart Catheters - January - March 2001 (No. of Cases)
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Audit
0
500
1000
1500
2000
2500
3000
3500
CGycm2
Ave dose
Left Heart Catheters - January - M arch 2001 (Ave Dose)
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Audit
0 0
13
6
1110
7
4
2 3
19
25
11
0
7
16
19
0
2
4
2524
0
24
17
22
0 0
13
0
15
12
0
5
10
15
20
25
%
% above DRL
Left Heart Catheters - January - March 2001 (% Above DRL)
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Special Cases-Cardiology
• EPS/RFA• Brachytherapy• CT angiography• Radio-isotopes• Echocardiography• Magnetic Resonance Imaging
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Electrophysiology
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Brachytherapy
60mm seed delivery catheter Catheter in diagonal 6 month follow up result
in LAD
Bifurcation in-stent restenosis Two wires Cutting balloon final result
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CT Angiography
• Anomalous right coronary artery arising from LC sinus
• Occlusion of RCA
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Magnetic ResonanceImaging
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Special Cases-Radiology
Per-operative arterial rupture
Covered stent deployment
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Radiology
• Dose ranges depend on type and site of intervention
• Dose reduction to patient -principles as cardiology
• Tube movements less• Position of operator more variable• Use ultrasound guidance where possible• CT fluoroscopy-decreased operation times
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Risk
0.00
0.04
0.08
0.12
0.16
0.20
0 15 30 45 60 75 90
Age at Exposure
Death per Sievert
(Sv)
FemaleMale
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Doses
3.8450Closure of persistent ductusarteriosus
8.4670Tetralogy of Fallot
ED mSvDAP cGcm²
Dose from common paediatric procedures
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Paediatric Intervention
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Limitation of Staff Exposure
• Reduce patient exposure - reduce staff exposure
• Radiation awareness and education• Dedicated interventional equipment• Reduce time of exposure• Use inverse square law• Use shielding by barrier
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Limitation of Staff Dose
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Use lead shields
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Wear appropriate lead protection
• Lead glasses• Thyroid shield• Lead apron – 3.5 - 5mm
lead equivalent• Monitoring
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Use mobile barriers
• Lead shield for operator
• Mobile barrier for radiographer
• Other staff appropriately positioned
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• Position monitors so that operator looks away from beam
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Paediatrics-always a special case
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Good Practice 1
• Follow Local Rules, procedures and protocols• Have all available information about patient
eg. previous grafts, echo data etc• Check patient identity, exposure justification,
consent• Position patient• Ensure all appropriate staff in room are
protected and wearing monitors• Use all lead shielding
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Good Practice 2
• Position table before screening• Keep mA low-kV high (60-90kV for coronaries)• X ray tube at max and II at min distance from
patient• Check staff position• Use dose reduction programmes if possible• Acquire images on full inspiration where
possible• Collimate to area of interest and choose views
carefully
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Good Practice 3
• Prolonged procedure-change beam angulation• Minimise fluoroscopy, high dose rate time,
number of acquisitions• Remember software features to reduce dose eg
replay fluoro• Don’t over use magnification• Remove grid for small patients• Check and record screening time and DAP cf
DRL
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Recommendations
• Dedicated interventional equipment• Radiation dose reduction packages should be mandatory• Radiation dose should be displayed on monitors• Radiation awareness should be promoted by audit and
regular feedback• Local standards-regular review and improvement• Continuing education-including practical training with
annual updates and testing• Research continued-to develop international standards