Patient doses in CT Examinations in 18 countries: Initial results from international atomic energy agency projects

(1)

SCIENTIFIC NOTE

PATIENT DOSES IN CT EXAMINATIONS IN 18 COUNTRIES:

INITIAL RESULTS FROM INTERNATIONAL ATOMIC ENERGY AGENCY PROJECTS

W. E. Muhogora¹, N. A. Ahmed², A. Beganovic³, A. Benider⁴, O. Ciraj-Bjelac⁵, V. Gershan⁶, E. Gershkevitsh⁷, E. Grupetta⁸, M. H. Kharita⁹, N. Manatrakul¹⁰, M. Milakovic¹¹, K. Ohno¹², L. Ben Omrane¹³, J. Ptacek¹⁴, C. Schandorf¹⁵, M. S. Shabaan¹⁶, D. Stoyanov¹⁷, N. Toutaoui¹⁸, J. S. Wambani¹⁹and M. M. Rehani^20,*

1Tanzania Atomic Energy Commission, PO Box 743, Arusha, Tanzania

2Sudan Atomic Energy Commission, PO Box 3001, Khartoum, Sudan

3Clinical Centre of University of Sarajevo, Bolnicka 25-71000, Sarajevo, Federation of Bosnia &

Herzegovina

4Centre National de Radioprotection, Rabat, Agdal, Morocco

5Vinca Institute of Nuclear Sciences, PO Box 522, 11001 Belgrade, Serbia

6Institute of Radiology, Clinical Centre, Skopje, the former Yugoslav Republic of Macedonia

7North Estonia Regional Hospital, Hiiu Street 44, 11619 Tallinn, Estonia

8St. Luke’s Hospital, St. Luke’s Road, Guardamangi, Malta

9Atomic Energy Commission of Syria, Damascus, Syria

10Department of Medical Sciences, Ministry of Public Health, Tiwanon Road, Nonthaburi 11000, Thailand

11Clinical Centre Banja Luka, 12 Beba 6, 7800 Banja Luka, Republic of Srpska, Bosnia & Herzegovina

12Department of Radiology Technology, Faculty of Medical Sciences, College of Medical Science, Kyoto, Japan

13Center National de Radioprotection, Hospital d’Enfants, Place Bab, Saadoun, 1006 Tunis, Tunisia

14Department of Medical Physics and Radiation Protection, University Hospital Olomouc, I.P. Pavlova 6, 775 20 Olomouc, Czech Republic

15Radiation Protection Institute, Ghana Atomic Energy Commission, PO Box LG 80, Legon, Accra, Ghana

16Radiology Department, Al-Sabah Hospital, Shuwaikh, Kuwait

17National Centre of Radiobiology and Radiation Protection, 132 Kliment Ohridski, 1756 Sofia, Bulgaria

18Division of Radiation and Medical Devices, Commissariat a` l’e´nergie atomique, Centre de recherche nucle´aire d’alger 2, Boulevard Frantz Fanon, B.P. 399, Alger-Gare, Algeria

19Kenyatta National Hospital, PO Box 20723, Nairobi, Kenya.

20International Atomic Energy Agency, Wagramer Strasse 5, A-1400 Vienna, Austria

Received December 30 2008, revised July 4 2009, accepted July 16 2009

The purpose of this prospective study at 73 facilities in 18 countries in Africa, Asia and Eastern Europe was to investigate if the CT doses to adult patients in developing countries are higher than international standards. The dose assessment was performed in terms of weighted computed tomography dose index (CTDIw) and dose length product (DLP) for chest, chest (high resolution), lumbar spine, abdomen and pelvis CT examinations using standard methods. Except in one case, the mean CTDIw values were below diagnostic reference level (DRL) while for DLP, 17 % of situations were above DRLs. The result- ing CT images were of adequate quality for diagnosis. The CTDIw and DLP data presented herein are largely similar to those from two recent national surveys. The study has shown a stronger need to create awareness and training of radiology personnel as well as monitoring of radiation doses in many developing countries so as to conform to the ALARA principle.

INTRODUCTION

The use of computed tomography (CT) in medicine is now firmly established as an essential tool for diagnosis, follow-up and aid in intervention. In many cases, it is a life-saving resource when rapid decisions are needed in the emergency room.

Because of such important benefits, the frequency of CT examinations is increasing rapidly all over the world, a fact that is evidenced in a number of CT dose surveys^{(1 – 8)}. Notwithstanding attempts to develop quality criteria and achieve harmonisation by the European Commission^(9,10), uniformity in image quality and patient dose is a challenge yet to be met. Whereas discrete slice-by-slice scanning was generally used just over a decade ago, now volume

*Corresponding author: M.Rehani@iaea.org Advance Access publication 17 August 2009

at Maastricht University on June 22, 2014http://rpd.oxfordjournals.org/Downloaded from

(2)

scanning using faster multi-slice CT systems is used.

The speed and ease with which imaging procedures can be performed can result in misuse of this imaging modality to carry out whole body scanning rather than confining the image study to a small part of the body⁽¹¹⁾. Although technological devel- opments provide the opportunity to decrease individual CT doses, the ambition to obtain quality images and cover larger area of the patient’s anatomy can lead to the opposite result. It is increasingly being documented that patient doses are higher than necessary and the image quality in CT often exceeds the level needed for confident diagnosis⁽¹⁰⁾. This message needs to penetrate widely among radiologists and radiographers^{(11 – 14)}. There is a need to ensure that the principles of justification and ALARA or/and optimisation, which are funda- mentals of radiation protection, are applied in CT.

Therefore, there is a need to establish programs aimed at managing doses from CT examinations.

One of the approaches towards this endeavour is the survey of parameters and associated doses for the purposes of comparison with diagnostic reference levels (DRLs). Such an approach has proven to be useful in many studies as it provides the baseline information for subsequent dose reduction or optimisation. Studies of this kind on a national level have been documented for a number of developed countries^{(2 – 8)}, and the examples cited here are not exhaustive. However, there is a paucity of information from developing countries and an even greater lack of multi-national studies. The United Nations Scientific Committee of Effects of Atomic Radiation provides information on CT usage but information on doses in developing countries is not enough⁽¹⁾. The objectives of the study were to investigate doses from CT examinations of adult patients among different centres and to compare the doses with international standards as provided in DRLs.

MATERIALS AND METHODS General

This report is from a prospective multi-national study project launched by the International Atomic Energy Agency (IAEA) in developing countries. The classification of countries into different regions (Africa, Asia and Europe) is in accordance with IAEA regional classification. The study was carried out from August 2005 to May 2008. The attempt has been made to survey dose levels to adult patients and to assess the potential for compliance with the ‘as low as reasonably achievable’ (ALARA) principle.

Although the focus of the project was on developing countries, Japan volunteered to participate, and this provides a useful reference for developed countries.

The project was started in the latter part of 2005 and

details can be found at http://rpop.iaea.org/RPOP/

RPoP/Content/InformationFor/MemberStates/

1_RegionalProjects/Task5PatientDose901.htm CT facilities

In the project, data are currently available from only 18 countries. The countries are: Algeria, Ghana, Morocco, Kenya, Sudan, Tanzania, Tunisia (Africa), Japan, Thailand, Kuwait, Syria (Asia), Bulgaria, Czech Republic, Bosnia and Herzegovina (Federation of & Republic of Srpska), Estonia, former Yugoslav Republic of Macedonia, Malta and Serbia (Eastern Europe). In view of shortage of space in tables, the Federation of Bosnia and Herzegovina is stated as Bosnia & Herz., Republic of Srpska as Srpska B&H and the former Yugoslav Republic of Macedonia as FYROM. Twelve more countries are collecting data, but sufficient information was not available at the time of analysing the data for this paper. Out of 88 CT facilities, data on patient doses were not available from 15 CT facilities (3 in Mongolia, 1 Serbia, 1 Thailand, 3 in Kuwait and 7 in Moldova). They provided data on frequency only, and thus these centres are not included in this analysis. Eighty-eight CT facilities were mostly from large teaching or non-teaching hospitals and the majority of these offer CT services to both adult and paediatric patients. At least one paediatric hospital from each of the three regions was additionally included in the study. The majority of the CT equipment under the study was manufactured by well- established multi-national companies, namely General Electric, Siemens, Philips, Toshiba and Shimadzu, while some equipment (,10 %) was manufactured by Marconi, Elscint, Hitachi or Picker. In most countries, the number of CT facilities covered was30 % of all CT facilities in each country and 23 % (20 out of 88) of these facilities had CT system which was more than 10 years old. Information on the frequency of CT examinations is available from 88 CT facilities while information on patient doses is available from 73 CT facilities. Structured instruc- tions and forms for data collection were provided to countries so that the results could be collected in a consistent and meaningful way for intercomparison.

Survey of CT exposure parameters

A survey of exposure parameters in common body CT procedures was performed at all participating centres of different countries. These procedures included chest, chest-high resolution (HR), lumbar spine, abdomen and pelvis CT examinations for adult patients. For each examination, information was collected on the tube voltage employed, the tube current displayed, the scan rotation time and the type of scanning (axial or helical). Additional information CT PATIENT DOSES IN EIGHTEEN DEVELOPING COUNTRIES

119

(3)

that was collected but was retained at the facility for subsequent use included the slice width, number of slices, pitch, field of view and gantry tilt where appli- cable. However, communication between the coordi- nating centre and the hospitals was maintained as a data-auditing mechanism and clarification was sought where needed for quality assurance purposes.

The exposure parameters were used to assess the dose to patients as described in the next section.

Dose quantities utilised

The weighted computed tomography dose index (CTDIw) and the dose length product (DLP) for a complete examination in mGy.cm are well-accepted dose descriptors in CT^(1,9). Because of the variable dosimetry capabilities in participating centres, the values for CTDIw were determined under direct supervision of the country representing author by one of the following methods: (a) direct phantom measurements; (b) calculation using an Internet-based method⁽¹⁵⁾; or (c) noting the values from the display console of the CT equipment. If the measurement method used was (a) above, the CT radiation dose profile integrated along the 100 mm length of the ionisation chamber (CTDI100) was measured at the central and peripheral positions of a standard head or body CT dosimetry phantom. The ionisation chambers were within the validity of calibration. On the assumption that the dose in a particular phantom decreases linearly with the position from the surface to the centre, the dose was approximated by a weighted CT dose index (CTDIw)⁽⁹⁾. CTDIw provides a weighted average of the central (CTDI100center) and the peripheral (CTDI100peripheral) dose measurements. This value was calculated using the following equation: CTDIw¼[(1/3).(CTDI100center)]þ[(2/

3).(CTDI100peripheral)] (mGy)⁽⁹⁾. The DLP values for the axial scan format were calculated using the following equation:

DLP¼X

i

ðnCTDIwTNCÞ_i ðmGycmÞ where nCTDIw is the normalised CTDIw per radio- graphic exposure (mGy/mAs),irepresents each scan sequence forming part of an examination andNis the number of slices, each of thicknessT(cm) and radio- graphic exposure C (mAs). In the case of helical (spiral) scanning, DLP values were calculated using the following equation:

DLP¼X

i

ðnCTDIwTAtÞ_i ðmGycmÞ whereirepresents each scan sequence forming part of an examination, T is the nominal irradiated slice

thickness (cm),Ais the tube current (mA) andtis the total acquisition time (s) for the sequence.

For the Internet-based method (b), CTDIw and DLP values were calculated by using a freeware software package developed by the Imaging Performance Assessment of CT scanners (ImPACT) group⁽¹⁵⁾ using the exposure parameters for the examination of actual patients. The software can also calculate the volume CTDI (CTDIvol), which is the ratio of CTDIw to the pitch factor⁽⁹⁾wherever pitch is constant. Although the patient technique factors were used in the calculation, the dose is to a standard PMMA phantom of diameter 32 cm. For centres that had no access to ImPACT software, the CTDIw or CTDIvol values were alternatively calculated by using scanner-specific normalised CTDI values tabulated in the ImPACT worksheet⁽¹⁵⁾. For the third method (c) above, post-CT scan CTDIvol values were directly read from the console (manufac- turer-based values) and used to derive the corresponding DLP values from the product of CTDIw and scan length. Where CTDIvol was recorded, DLP was obtained from the product of CTDIvol and scan length. For centres that recorded console readings in CT dose assessment, comparisons were also done with the values derived from the ImPACT method. Provided initial checks are carried out locally to validate the readings, dose displays on the scanner consoles have also been found to be adequate^(2,16).

The radiologists were requested to subjectively assess the image quality of each CT image at their hospitals. In the current study, the concern was whether the images were used for diagnosis or not.

All images of the reported data under this study were used for diagnosis. In the subsequent phase when dose management is to be practiced, quantitat- ive assessment of image quality on a scale of 1 – 5 is planned to see if poor quality images are being gen- erated because of dose reduction.

RESULTS

Computed tomography dose index

Table 1 presents the mean values of CTDIw for adults in participating centres in different countries and regions. The DRLs shown in the table (in brackets) for each CT procedure are taken from the European guidelines on quality criteria for CT⁽⁹⁾ assuming patients of a similar average size. The corresponding ranges in CTDIw values as well as the ratio of maximum to minimum CTDIw values are presented in Table 2. The CTDIw values for adults were in most cases below the DRLs, but the wide variation in CTDIw values of up to a factor of 16 in abdomen CT indicates a need to review the scanning

(4)

parameters (Table 2). Regionally also a similar situation of variations was observed. Differences in the performance of CT equipment form a main expla- nations for such variations.

Dose length product

The mean DLP values for adults in participating centres in the three regions are presented in Table 3.

Presented with the mean values for each country are the median and overall mean values for all facilities, which further characterise dose distribution. The corresponding DLP ranges are presented in Table 4, where DLP values are seen to vary up to a factor of 13 in pelvis CT. The DLP variations indicate a need to reduce dose without affecting the diagnostic quality so as to exercise the ALARA principle. The reasons for DLP variations were mainly due to differences in the CT performance characteristics

and scanning parameters used such as pitch and scan lengths as well as varied patient characteristics.

DISCUSSION

Initial efforts in dose management in CT primarily in developed countries addressed issues such as the potential for high patient doses in CT procedures, the increasing frequency of CT examinations, changes in clinical applications and the increasing contribution of CT to collective dose^(13,14). Other issues emerged from these efforts such as lack of appropriate parameter selection in pediatric CT examinations and the potential risk of cancer induc- tion from the use of CT in children^(17,18). There is a paucity of information on the available practice and apparently on awareness of dose management in CT practice in many developing countries, and this can lead to higher patient doses than necessary.

Table 1. Mean CTDIw values for adult patients in different countries (a) and regions (b). The determination method is indicated as based on phantom measurements (P), calculation by Internet data (I) or display of console (C). The (DRL⁽⁹⁾is

shown in brackets.

By country Method Mean CTDIw (mGy)

Chest Chest HR Lumbar spine Abdomen Pelvis

DRL (30) (35) (35) (35) (35)

Algeria P 9.2 6.8 16.2 15.4 19.1

Ghana P or I 17.1 17.2 20.4 20.4 20.4

Kenya P 20 – – 13 20

Morocco P 10 25.8 11.9 11.9 10.6

Sudan P, I or C 19.2 14.1 – 20.5 7.3

Tanzania I 16.8 13.9 38.8 22.7 26

Tunisia C 24.3 – – – 25.4

Japan C 14 15 19.3 19.3 19.3

Kuwait C 12 18.2 – 11.7 –

Syria P 18.6 24.3 – 21.6 28.4

Thailand C or P 15.3 14.4 19.5 18.5 16.8

Bulgaria P 16.7 14.7 20.7 16.3 18.2

Czech Republic P, I or C 21.3 16.9 23.9 18.4 20.3

Bosnia & Herz. P 13.5 20.6 21.2 21.2 20.1

Srpska B&H C 6.9 – 22.8 10.2 8.3

Estonia C 15.7 – – 19 14.5

FYROM I 11.4 – – 13 11.4

Malta C 11.5 10 15.4 14.8 21.8

Serbia C 20.1 – 12.3 12.3 14.1

By region Mean CTDIw (mGy) (DRL shown in brackets⁽⁹⁾)

(30) (35) (35) (35) (35)

Africa 9.2 – 24.3 6.8 – 25.8 11.9 – 38.8 11.9 – 22.7 7.3 – 26

Asia 12 – 18.6 14.4 – 24.3 19.3 – 19.5 11.7 – 21.6 16.8 – 28.4

Eastern Europe 6.9 – 21.3 10 – 20.6 12.3 – 23.9 10.2 – 21.2 8.3 – 21.8

Dash (2) indicates data not available.

CT PATIENT DOSES IN EIGHTEEN DEVELOPING COUNTRIES

121

(5)

Table 2. Ranges of CTDIw values for adult patients in different countries. The DRL is given below each CT examination while the ratio of maximum-to-minimum CTDIw value is shown in brackets against each range.

Country Method Mean CTDIw (mGy)

DRL (30) (35) (35) (35) (35)

Algeria P 2.6 – 13.8 (5.3) 3.2 – 9.2 (2.9) 2.6 – 26.1 (10) 2.6 – 24.5 (9.4) 3.5– 36.2 (10.3)

Ghana P or I 11.4 – 29.7 (2.6) 11.4 – 30 (2.6) 13.4 – 42.4 (3.2) 13.4 – 42.4 (3.2) 13.4 – 42.4 (3.2)

Kenya P 7 – 43 (6.1) – – 10 – 15 (1.5) 12– 29 (2.4)

Morocco P 5.3 – 16.4 (3.1) 14.7 – 43.4 (3) 4.6 – 19.3 (4.2) 4.6 – 19.3 (4.2) 7.4– 13.7 (1.9)

Sudan P, I or C 3 – 35 (11.7) 6 – 11 (1.8) – 5.3 – 59.6 (11.2) 3.1– 9.8 (3.2)

Tanzania I 9.5 – 25.5 (2.7) 9.3 – 16.2 (1.7) 9.2 – 47.8 (4.1) 25.8 – 51.7 (5.2) 16.1 – 35.8 (2.2)

Tunisia C 6.5 – 42 (6.5) – – – 12.8 – 38 (3)

Japan C 12– 18 (1.5) 12 – 21 (1.8) 18 – 20 (1.1) 18 – 20 (1.8) 18– 20 (1.8)

Kuwait C 9.7 – 17.6 (1.8) 14.7 – 21.8 (1.5) – 8.2 – 17.6 (2.1) –

Syria P 9 – 36.9 (4.1) 9.9 – 51.5 (5.2) – 13 – 45.7 (3.5) 13– 57.2 (4.4)

Thailand C or P 11.9 – 18.1 (9.5) 5.6 – 32.2 (5.8) – 4.6 – 18.5 (4) 12.6 – 20.2 (1.6)

Bulgaria P 16.4 – 17 (1.04) – 13.5 – 15.9 (1.2) 5.6 – 17 (16.3) 17– 19.4 (1.1)

Czech Republic P, I or C – – – – –

Bosnia & Herz. P 11.6 – 30.6 (2.6) 11.6 – 13.8 (1.2) 10.9 – 25.2 (2.3) 10.9 – 25.2 (2.3) 13.1 – 27.2 (2.1)

Srpska B&H C 3.9 – 10.2 (2.6) – 11.7 – 32.5 (2.8) 5.6 – 13.8 (2.5) 6.3– 12.6 (2)

Estonia C 7.7 – 22.2 (2.9) – – 10.5 – 22.9 (2.2) 9.4– 19.2 (2)

FYROM I 7.8 – 13.5 (1.7) – – 12.8 – 13.5 (1.1) 7.8– 13.5 (1.7)

Malta C 10.4 – 12.5 (1.2) 8 – 12 (1.5) 13.5 – 16 (1.2) 13.5 – 16 (1.2) 12– 31.5 (2.6)

Serbia C 5.8 – 43 (7.4) – 8.7 – 18.4 (2.1) 6.7 – 18.4 (2.7) 6.4– 14.5 (2.7)

W.E.MUHOGORAETAL.

122

(6)

The information obtained in the present survey of CT practices is aimed at assessing the situation and the differences in practices in many developing countries in different parts of the world. A study of this nature results in increased awareness in participating centres and the results of the study have wider potential for many developing countries.

The International Commission on Radiological Protection in its publication 73 recommends the use of DRLs as an optimisation tool. The numerical values of DRLs are compared with the mean value or other appropriate values observed in practice for a suitable reference group of patients or a suitable reference phantom⁽¹⁹⁾. This approach is also suggested in a wide scale national survey⁽¹⁹⁾. The median and third quartile values of the distributions of the mean doses can also be used for comparison with DRLs^(20,21). In this study, the mean CTDIw values for adult patients were below DRLs (Table 1)

except in one situation, while the mean DLP values for adult patients in 17 % (13/77) of situations were above DRLs (Table 3). This is an important finding that reflects that covering larger areas of the patient’s body contributes more to increased patient dose than the equipment performance factor. However, the observed variation in ranges of CTDIw and DLP values (Tables 2 and 4) indicates the need to exercise the ALARA principle. Therefore, in centres where the CTDIw or DLP values were found to be above DRLs, a review of how CT examinations are conducted in practice was recommended in order to investigate the potential for dose reduction. Even for centres where values are below DRLs, published papers indicate that dose values much lower than DRLs can be achieved in practice without affecting the diagnostic purpose^(8,22). The factors contributing to CTDIw and DLP variations appear mainly to be the operator choice and the radiologist preference.

Table 3. Mean DLP values for adult patients in different countries (a) and regions (b). The DRL⁽⁹⁾is shown in brackets.

By country Mean DLP (mGy.cm)

DRL (650) (280) (780) (780) (570)

Algeria 347 194 646 554 604

Ghana 396 348 523 496 415

Kenya 933 – – 1314 837

Morocco 256 121 341 341 271

Sudan 423 171 – 725 163

Tanzania 382 366 363 602 494

Tunisia 874 – – – 599

Japan 564 404 513 513 513

Kuwait 223 561 – 552 –

Syria 416 103 – 638 545

Thailand 301 99 720 574 390

Bulgaria 512 – – 435 322

Czech Republic 341 – 507 444 466

Bosnia & Herz. 437 330 460 460 323

Srpska B&H 246 – 541 448 231

Estonia 833 – – 910 698

FYROM 342 – – 526 416

Malta 296 117 289 480 268

Serbia 148 – 512 512 305

Median 82 194 512 520 416

Mean 435 256 492 585 437

By region Mean DLP (mGy.cm)

(650) (280) (780) (780) (570)

Africa 256 – 933 121 – 366 341 – 646 341 – 1314 163 – 837

Asia 223 – 564 99 – 561 513 – 720 513 – 638 390 – 545

Eastern Europe 148 – 833 117 – 330 289 – 541 435 – 910 268 – 698

CT PATIENT DOSES IN EIGHTEEN DEVELOPING COUNTRIES

123

(7)

Of all participating hospitals, none was objectively adjusting CT exposure parameters to patient size, and it is suggested that such efforts should be a starting point for dose reduction in developing countries. Variations in equipment design between manufacturers and models, such as differences in the level of filtration, different focus-isocentre distances and variations in collimator and detector efficiency can have a significant impact on dose⁽¹⁶⁾. Few CT facilities had automatic exposure control (AEC) devices, which is one of the factors contributing to the observed dose variations. It is known that AEC devices have the potential to reduce the dose to around 50 % in some anatomical regions of standard-sized patients, and even greater dose reduction for children and smaller adult patients^(23,24). The influence of the clinical protocols in use, the implementation of which is operator dependent, can also contribute to such CT dose variations^(13,16,24). Despite the few examples given, there is limited comprehensive information on the relative contri- butions of equipment or operator technique to variations in CT dose.

The results obtained from this study indicated that CTDIw and DLP values as well as their variation patterns are similar in Japan and developing countries. Comparisons with other large-scale surveys can conveniently be done using DLP, which is derived irrespective of whether CTDIw or

CTDIvol was used. A report of a CT survey in the USA indicated that the mean DLP values for adults, irrespective of whether axial or helical scanning was used, ranged from 507 – 580 mGy.cm (chest), 423 – 655 mGy.cm (abdomen) and 359 – 490 mGy.cm ( pelvis)⁽⁵⁾. The report of a CT survey done in the UK indicates that the median DLP values for adult patients were 488 mGy.cm (chest), 786 mGy.cm (chest, abdomen and pelvis), 472 mGy.cm (abdomen) and 534 mGy.cm (abdomen and pelvis)⁽²⁾. Therefore the mean DLP values in this study (Tables 3 are largely similar to DLP values in the USA for the same types of CT examinations.

The median DLP values for chest and abdomen CT obtained in this study are also comparable to the DLP values from the UK’s CT dose survey.

The observed variations in dose levels clearly re- confirm the need to reduce doses without affecting diagnostic confidence. Efforts should focus on the training of CT equipment operators to select appropriate parameters tailored to individual patient size, which can achieve the desirable diagnostic image quality at reasonably low doses. These efforts should go hand-in-hand with continuously increasing the awareness of risk and proper CT dose management. An approach involving active partici- pation of all stakeholders at seminars that outline the problems and suggest possible solutions has achieved positive results^(24,25), and is worthy of Table 4. Ranges of DLP values for adult patients in different countries. The DRL⁽⁹⁾is given below each CT examination

while the ratio of maximum-to-minimum DLP value is shown in brackets against each range.

Country Mean DLP (mGy.cm)

DRL (650) (280) (780) (780) (570)

Algeria 76 – 483 (6.4) 95 – 276 (2.9) 136 – 800 (5.9) 136 – 800 (5.9) 117 – 905 (7.7) Ghana 188 – 594 (3.2) 168 – 594 (3.5) 287 – 848 (3) 287 – 848 (3) 283 – 848 (3)

Kenya 550 – 2051 (3.7) – – 466 – 2241 (4.8) 326 – 2241 (6.9)

Morocco 175 – 394 (2.3) 117 – 127 (1.1) 115 – 618 (5.4) 115 – 618 (5.4) 185 – 329 (1.8)

Sudan 77 – 650 (8.4) 150 – 280 (1.9) – – 161 – 2100 (13)

Tanzania 146 – 564 (3.9) 214 – 466 (2.2) 172 – 1078 (6.3) 80 – 640 (8) 49 – 498 (10.2)

Tunisia 268 – 1480 (5.5) – – – 319 – 878 (2.8)

Japan 533 – 626 (1.2) 145 – 533 (3.7) 511 – 518 (1.01) 511 – 518 (1.01) 511 – 518 (1.01)

Kuwait 118 – 387 (3.2) 293 – 736 (2.5) – 187 – 913 (4.9) –

Syria 178 – 753 (4.2) 33 – 286 (8.7) – 267 – 1634 (6.1) 275 – 1142 (4.2)

Thailand 193 – 453 (2.3) 70 – 154 (2.2) – 391 – 757 (1.9) 273 – 507 (1.9)

Bulgaria 403 – 0.512 (1.3) – 435 – 498 (1.1) 322 – 498 (1.5) 169 – 322 (1.9) Czech Republic 220 – 462 (2.1) – 312 – 701 (2.2) 312 – 576 (1.8) 242 – 639 (2.6) Bosnia & Herz. 139 – 734 (5.3) – 163 – 756 (4.6) 163 – 756 (4.6) 156 – 490 (3.1) Srpska B&H 147 – 376 (2.6) – 296 – 795 (2.7) 67 – 389 (5.8) 142 – 319 (2.2)

Estonia 462 – 1697 (3.7) – – 620 – 1632 (2.6) 345 – 1248 (3.6)

FYROM 234 – 405 (1.7) – – 510 – 538 (1.1) 312 – 530 (1.7)

Malta 220 – 592 (2.7) 80 – 153 (1.9) 43 – 534 (12.4) 360 – 600 (1.7) 250 – 285 (1.1)

Serbia 124 – 380 (3.1) – 201 – 703 (3.5) 201 – 793 (3.5) 165 – 714 (4.3)

Dash (2) indicates data not available

(8)

applying in developing countries. However, the use of patient-specific CT exposure parameters will require extensive study.

CONCLUSION

The CT doses to adult patients in some countries of Africa, Asia and Eastern Europe have been presented. The main findings of this study are as follows:

(a) There is a need to increase awareness among radiology staff of radiation dose management in CT.

(b) Except in one case, the mean CTDIw values for adult patients were below DRLs although there were individual values above DRLs. The mean DLP values for adult patients in 17 % of situations were above DRLs, with higher variations of up to a factor of 13. This indicates the need for emphasis on technique more than equipment QC as CTDIw values are not high.

(c) In view of the limited reports on these issues from developing countries, this study has established baseline information on dose levels, which should form a basis for reducing patient doses without affecting diagnostic confidence, which is currently being undertaken.

ACKNOWLEDGMENTS

The authors wish to thank their respective governments for their nomination to participate in the project. Only one principal contributor from each participating team in a country has been included as an author, whereas many members were involved in the project. The authors wish to express their grati- tude to all members of the team for their cooperation and understanding. Except the first author and the last author, who is coordinator of these projects and is corresponding author, all other authors names have been arranged alphabetically with family name.

FUNDING

The work was supported by the Governments of the participating countries and the technical cooperation projects of the International Atomic Energy Agency, RAF/9/033 (Africa), RAS/9/9034&9040 (Asia) and RER/9/079&080 (Europe).

REFERENCES

1. United Nations Scientific Committee on the Effects of Atomic Radiation.Sources and effects of ionizing radiation. Report to the General assembly, Annex D:

medical radiation exposures (New York: United Nations) (2000).

2. Shrimpton, P. C., Hillier, M. C., Lewis, M. A. and Dunn, M.National survey of doses from CT in the UK 2003. Br. J. Radiol.79, 968 – 980 (2006).

3. Origgi, D., Vigorito, S., Villa, G., Belloni, M. and Tosi, G.Survey of computed tomography techniques and absorbed dose in Italian hospitals: A comparison between two methods to estimate DLP and the effective dose and to verify fulfilment to the diagnostic reference levels. Eur. Radiol.16, 227 – 237 (2006).

4. Conway, B. J., McCrohan, J. L., Antonsen, R. G., Rueter, F. G., Slayton, R. J. and Suleiman, O. H.

Average radiation dose in standard CT examinations of the head: Results of the 1990 NEXT survey. Radiology 184, 135 – 140 (1992).

5. Conference of Radiation Control Program Directors (CRCPD). Nationwide Evaluation of X-ray Trends (NEXT). Tabulation of graphical summary of 2000 survey of Computed Tomography. CRCPD Publication E-07-2 (2007) (Available at http://www .crcpd.org).

6. Hidajat, N., Wolf, M., Nunnemann, A., Liersch, P., Gebauer, B., Techgraber, U., Schroder, R. J. and Felix, R. Survey of conventional and spiral CT doses.

Radiology218, 395 – 401 (2001).

7. Moss, M. and McLean, D. Paediatric and adult computed tomography practices and patient dose in Australia. Australasian Radiol.50(1), 33 – 40 (2006).

8. Tsapaki, V.et al.Dose reduction in CT while maintain- ing diagnostic confidence: Diagnostic reference levels at routine, head, chest and abdominal CT-IAEA coordinated research project. Radiology240, 828 – 834 (2006).

9. European Commission. European Guidelines on quality criteria for computed tomography. EUR 16262 EN, Luxembourg (1999).

10. European Commission. European Quality Criteria for Multislice CT. Luxemborg (2004) (Available at http://

www.msct.eu/CT_Quality_Criteria.htm). Accessed on 16 May 2005.

11. International Commission on Radiological Protection.

Managing patient dose in multi-detector computed tomography (MDCT). ICRP Publication 102. Ann. ICRP 37(1) (2007).

12. Tsapaki, V., Triantopoulou, C.H., Maniatis, P., Siafas, I., Priniotaki, A. and Papailliou, J.Abdomen CT: influence of patient size and technical factors on image noise and quality. Proceedings of 23rd International Congress of Radiology and the ISR. Montreal, Canada, 647 – 650 (2004).

Managing patient dose in computed tomography.

ICRP publication 87. Ann. ICRP30(4) (2001).

14. Rehani, M. M. and Berry, M.Radiation doses in computed tomography. BMJ320, 593 – 594 (2000).

15. Imaging Performance and Assessment of CT scanners (ImPACT). CT patient dosimetry Excel spreadsheet (version 0.99x 20/01/06) (Available at http://www.

impactscan.org/ctdosimetry.htm).

16. Shrimpton, P. C., Hillier, M. C., Lewis, M. A. and Dunn, M. Doses from computed tomography (CT) examinations in the UK-2003 review. National Radiological Protection Board (2005).

17. Donnelly, L. F., Emery, K. H., Brody, A. S., Laor, T., Glylys-Monin, V. M., Anton, C. G., Thomas, S. R.

and Frush, D. P.Minimizing radiation dose for pediatric CT PATIENT DOSES IN EIGHTEEN DEVELOPING COUNTRIES

125

(9)

body applications of single-detector helical CT: strategies at a large children’s hospital. Am. J. Roentgenol.

176, 303 – 306 (2001).

18. International Atomic Energy Agency.Optimization of the radiological protection of patient undergoing radi- ography, fluoroscopy and computed tomography. Final report of a coordinated research project in Africa, Asia and Eastern Europe. IAEA TEC DOC-1423, (Vienna:

IAEA) (2004).

Radiological protection and safety in medicine. ICRP Publication 73. Ann. ICRP26(2) (1996).

20. Wall, B. F.Implementation of DRLs in the UK. Radiat.

Prot. Dosim.114(1– 3), 183 – 187 (2005).

21. Gray, J. E., Archer, B. R., Butler, P. F., Hobbs, B. B., Mettler, F. A. Jr, Pizzutiello, R. J. Jr, Schueler, B. A.,

Strauss, K. J., Suleiman, O. H. and Yaffe, M. J.

Reference values for diagnostic radiology: application and impact. Radiology235, 354 – 358 (2005).

22. Karla, M. K., Maher, M. M., Toth, T. L., Hamberg, L. M., Blake, M. A., Shepard, J.-A. and Saini, S.

Strategies for CT radiation dose optimization.

Radiology230, 619 – 628 (2004).

23. Lewis, M. A. and Edyvean, S.Patient dose reduction in CT. Br. J. Radiol.78, 880 – 883 (2005).

24. Linton, O. W. and Mettler, F. A.National conference on dose reduction in CT with an emphasis on pediatric patients. Am. J. Rontgenol. 181, 321 – 329 (2003).

25. Wall, B. F. What needs to be done about reducing patient doses from CT? The North American approach.

Br. J. Radiol.76, 763 – 765 (2003).