arab congress of radiology (arc 5) 25 th /28 th april 2012 le royal hotel - hamamet –tunisia

MEASUREMENTS OF RADIATION DOSES MEASUREMENTS OF RADIATION DOSES IN MULTISLICES COMPUTED IN MULTISLICES COMPUTED

TOMOGRAPHY EXAMINATIONSTOMOGRAPHY EXAMINATIONS

A. ELMAHDI*, A. SULIEMANA. ELMAHDI*, A. SULIEMAN

*Presenting author*Presenting author11Sudan Atomic Energy Commission, Radiation Safety Sudan Atomic Energy Commission, Radiation Safety Institute. Institute. P.O. Box 3001, Post code 11111, Khartoum, P.O. Box 3001, Post code 11111, Khartoum,

Sudan.Sudan.22Sudan University of Science and Technology, College of Sudan University of Science and Technology, College of Medical Radiologic Science. P.O Box 1908, Post code Medical Radiologic Science. P.O Box 1908, Post code

11111, Khartoum, Sudan.11111, Khartoum, Sudan.

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LE ROYAL HOTEL - HAMAMET –TUNISIALE ROYAL HOTEL - HAMAMET –TUNISIAVR3

IntroductionIntroduction

The motivations for this study are the relatively The motivations for this study are the relatively high radiation dose to the patient in CT high radiation dose to the patient in CT examinations and the increasing frequency and examinations and the increasing frequency and variety of examinations.variety of examinations.

The UNSCEAR, 2000 has highlighted that the The UNSCEAR, 2000 has highlighted that the worldwide there about 93 million CT examinations worldwide there about 93 million CT examinations performed annually at a rate of about 57 performed annually at a rate of about 57 examinations per 1000 persons.examinations per 1000 persons.

ARAB CONGRESS OF RADIOLOGY (ARC 5) 25th/28th APRIL 2012 LE ROYAL HOTEL - HAMAMET –TUNISIA ARAB CONGRESS OF RADIOLOGY (ARC 5) 25th/28th APRIL 2012 LE ROYAL HOTEL - HAMAMET –TUNISIA

The doses tissues from CT can often approach or The doses tissues from CT can often approach or exceed levels known to increase the probability of exceed levels known to increase the probability of cancer .cancer .

technologists are responsible for managing the technologists are responsible for managing the dose in collaboration radiologists and medical dose in collaboration radiologists and medical physicists.physicists.

In Sudan, the number of CT machines was In Sudan, the number of CT machines was increased in last few years. increased in last few years.

Cont.IntroductionIntroduction

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The current study intended to:The current study intended to:

(i)(i) Measure the radiation dose for patients Measure the radiation dose for patients during CT examinations.during CT examinations.

(ii) Increase the benefits of CT examination (ii) Increase the benefits of CT examination compare with the risk of radiation.compare with the risk of radiation.

(iii)(iii) Estimate the effective dose for the patients Estimate the effective dose for the patients undergoing CT examination.undergoing CT examination.

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Objectives Objectives

A total of 130 patients with different CT A total of 130 patients with different CT examinations were referred to Alzaytouna examinations were referred to Alzaytouna specialist and Alamal National hospitals in the specialist and Alamal National hospitals in the period of study.period of study.

All the patients were performed using All the patients were performed using departments’ protocols with Multislice CT (MSCT) departments’ protocols with Multislice CT (MSCT) 64 slice (Toshiba Sensation aquilion 64).64 slice (Toshiba Sensation aquilion 64).


Materials and MethodsMaterials and Methods

Cont.Materials and MethodsCont.Materials and Methods Data were collected to the study the effects of Data were collected to the study the effects of patient-related parameters :patient-related parameters :

((e.g. age, sex, diagnostic of examination, and use e.g. age, sex, diagnostic of examination, and use of contrast media) on the patient dose).of contrast media) on the patient dose).

Data were collected to investigate the effect of Data were collected to investigate the effect of exposure-related parameters (gantry tilt, kilo exposure-related parameters (gantry tilt, kilo voltage (kV), tube current (mA), exposure time, voltage (kV), tube current (mA), exposure time, slice thickness, table increment, number of slices, slice thickness, table increment, number of slices, and start and end positions of scans) on patient and start and end positions of scans) on patient dose. dose. ARAB CONGRESS OF RADIOLOGY (ARC 5) 25th/28th APRIL 2012 LE ROYAL HOTEL - HAMAMET –TUNISIA

The average age of the patients was 45The average age of the patients was 4518 18 years. years.

The mean effective dose for ANH was 17.4±12.7 The mean effective dose for ANH was 17.4±12.7 mSv, 22.9±14.3 mSv and 2.4±0.9 mSv for the mSv, 22.9±14.3 mSv and 2.4±0.9 mSv for the chest, abdomen and brain examinations, chest, abdomen and brain examinations, respectively.respectively.

The mean effective doses for ASH specialist The mean effective doses for ASH specialist hospital were 26.3±7.8 mSv, 47.6±33.0 mSv, and hospital were 26.3±7.8 mSv, 47.6±33.0 mSv, and 3.7±1.5 mSv for the chest, abdomen and brain, 3.7±1.5 mSv for the chest, abdomen and brain, respectively.respectively.


ResultsResults

Table 1: Comparison of patient dose during CT Table 1: Comparison of patient dose during CT with previous studieswith previous studies

Author No. of pts Exam Machine model

Present study

130 Chest, Abd,

Brain& s

Toshiba Sensation aquilion 64

A.M Nour (2010)

83 Abd Siemens Somatom emotion

Entisar Omer (2011)

51 CTU Siemens Somatom emotion duo

European Commission1999

Routine Abd,

Pelvis & Liver

I.I.Suliman

(2010)

445 Head, chest, abd& pelvis

Toshiba Somatom sensation16

Table 2: Comparison of patient dose during CT Table 2: Comparison of patient dose during CT with previous studieswith previous studiesAuthor Pitch kVp mAs Slice

thickness

Present

study

1.5 120 242.8 5.5

A.M Nour 0.75-1 80-120 42-243 24

Entisar Omer 110-130 37-111

I.I.Suliman NA 120 41±17 5.8±1

Table 3: Comparison of patient dose during CT Table 3: Comparison of patient dose during CT with previous studies(Dose-mSv)with previous studies(Dose-mSv)Author CTDIvol DLP Effective dose

Present study 178.3 2344.4 20.05

A.M Nour 18.87 mGy 865.3 mGy.cm 13.5

Entisar Omer 25.1-10.95 85-425 1.29-6.37

European

Commission1

999

NA 780 11.7

I.I.Suliman 65 507.3 11.3

A total of 130 patients were examined over 4 months. Table 4.1 and A total of 130 patients were examined over 4 months. Table 4.1 and Table 4.2 represent the anatomical regions of all patients.Table 4.2 represent the anatomical regions of all patients.

Anatomical regions are important in radiation dosimetry because in Anatomical regions are important in radiation dosimetry because in CT imaging the applied protocol affects drastically radiation dose CT imaging the applied protocol affects drastically radiation dose (region of interest ROI) and use of contrast media.(region of interest ROI) and use of contrast media.

There were large variations in the radiation dose to the patients. There were large variations in the radiation dose to the patients. ARAB CONGRESS OF RADIOLOGY (ARC 5) 25ARAB CONGRESS OF RADIOLOGY (ARC 5) 25 thth/28/28thth APRIL 2012 LE ROYAL HOTEL - HAMAMET –TUNISIA APRIL 2012 LE ROYAL HOTEL - HAMAMET –TUNISIA

DiscussionDiscussion

In general, these variations of doses can be In general, these variations of doses can be attributed to the differences in tube voltages attributed to the differences in tube voltages (kVp), number of scan, tube current time product (kVp), number of scan, tube current time product (mAs) and repeated scans.(mAs) and repeated scans.

There may be justifiable reasons for some There may be justifiable reasons for some variability in practice; of which the most important variability in practice; of which the most important one is the difference in anatomical regions.one is the difference in anatomical regions.

This difference is greater if operators and This difference is greater if operators and practitioners are insufficiently educated in newly practitioners are insufficiently educated in newly emerging technology.emerging technology.


Cont.Discussion Cont.Discussion

Further, increasing demand in CT examination Further, increasing demand in CT examination in Sudan may induce operators to overcome the in Sudan may induce operators to overcome the ideal referring criteria because the vast majority ideal referring criteria because the vast majority of CT services are concentrated in Khartoum of CT services are concentrated in Khartoum state.state.

It is perceived that this is more likely to occur It is perceived that this is more likely to occur with relatively inexperienced workers and it is with relatively inexperienced workers and it is also possible that some examinations are carried also possible that some examinations are carried out more intensively than needed as a mean of out more intensively than needed as a mean of radiation risk limitations.radiation risk limitations.



Patients were referred to the CT scan department for different examinations (e.g. brain, chest, abdomen and Patients were referred to the CT scan department for different examinations (e.g. brain, chest, abdomen and others).others).

The patients were scanned with routine protocols which were desired by the manufacturer adopted by the operator. The patients were scanned with routine protocols which were desired by the manufacturer adopted by the operator.





The patients were scanned with kVp range The patients were scanned with kVp range from (100-120), and scanned with mAs range from (100-120), and scanned with mAs range (87-743) as shown in the Table 4.3, and with (87-743) as shown in the Table 4.3, and with the pitch (0.75) or less than (1), and the pitch (0.75) or less than (1), and feed/rotation about 18 mm, and slice thickness feed/rotation about 18 mm, and slice thickness collimation was (16x1.5), and slice thickness collimation was (16x1.5), and slice thickness was 5 mm, and rotation time was (0.5 s) and was 5 mm, and rotation time was (0.5 s) and region of scan included thee ROI.region of scan included thee ROI.



These parameters produced these These parameters produced these radiation values represented in Table 4.4 radiation values represented in Table 4.4 which shows the values of DLP average which shows the values of DLP average ((2275.32275.3 mGy.cm), CTDIvol average (168.3 mGy.cm), CTDIvol average (168.3 mGy) and effective dose average (20.05 mGy) and effective dose average (20.05 mSv). The range of DLP was (464.8-mSv). The range of DLP was (464.8-7619.8 mGy.cm) and the large variable in 7619.8 mGy.cm) and the large variable in DLP due to repeated of scans and DLP due to repeated of scans and patients.patients.



In CT examination, patients are exposed In CT examination, patients are exposed to high radiation dose. Therefore, the used to high radiation dose. Therefore, the used of ordinary dose values (CTDI, or DLP) will of ordinary dose values (CTDI, or DLP) will provide less information regarding the provide less information regarding the radiation risks. radiation risks.

Effective dose is the unit of choice in this Effective dose is the unit of choice in this situation (partial exposure) and furthermore, situation (partial exposure) and furthermore, comparisons between different procedures comparisons between different procedures are possible with different imaging are possible with different imaging modalities.modalities.



In this study, the mean effective dose for Al-In this study, the mean effective dose for Al-amal hospital was 17.4±12.7 mSv, 22.9±14.3 amal hospital was 17.4±12.7 mSv, 22.9±14.3 mSv and 2.4±0.9 mSv for the chest, abdomen mSv and 2.4±0.9 mSv for the chest, abdomen and brain, respectively.and brain, respectively.

The mean effective dose for Al-Zaytouna The mean effective dose for Al-Zaytouna hospital were 26.3±7.8 mSv, 47.6±33.0 mSv, hospital were 26.3±7.8 mSv, 47.6±33.0 mSv, 3.7±1.5 mSv for the chest, abdomen and brain, 3.7±1.5 mSv for the chest, abdomen and brain, respectively respectively

––TUNISIARAB CONGRESS OF RADIOLOGY (ARC 5) 25TUNISIARAB CONGRESS OF RADIOLOGY (ARC 5) 25 thth/28/28thth APRIL 2012 LE ROYAL HOTEL - HAMAMET –TUNISIA APRIL 2012 LE ROYAL HOTEL - HAMAMET –TUNISIA


These factors indicate strongly against These factors indicate strongly against measures to provide effective radiation measures to provide effective radiation protection.protection.

It is necessary to establish the minimum It is necessary to establish the minimum exposure threshold that will deliver exposure threshold that will deliver adequate image quality in each adequate image quality in each application, preferably expressed in terms application, preferably expressed in terms of clinical effectiveness.of clinical effectiveness.



The dose of this study is relatively higher compared to previous studies. The dose of this study is relatively higher compared to previous studies. This can be attributed to lack of training in CT dose optimization and CT This can be attributed to lack of training in CT dose optimization and CT modality.modality.

The study showed wide variations of radiation dose and effective dose for The study showed wide variations of radiation dose and effective dose for the same hospital. Continuous training of workers in this field and the same hospital. Continuous training of workers in this field and establishing the diagnostic reference level in the Sudan are very important.establishing the diagnostic reference level in the Sudan are very important.ARAB CONGRESS OF RADIOLOGY (ARC 5) 25ARAB CONGRESS OF RADIOLOGY (ARC 5) 25thth/28/28thth APRIL 2012 LE ROYAL HOTEL - HAMAMET –TUNISIA APRIL 2012 LE ROYAL HOTEL - HAMAMET –TUNISIA


Conclusions Conclusions

Acknowledgement Acknowledgement

The authors would like to than all the staff of all The authors would like to than all the staff of all hospitals for the kind support.hospitals for the kind support.

Thank you for your kind attentionThank you for your kind attention

arab congress of radiology (arc 5) 25 th /28 th april 2012 le royal hotel - hamamet –tunisia

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