survey of patient dose in computed tomography in ...

Radiation Protection Dosimetry Advance Access published May 28, 2010 Radiation Protection Dosimetry (2010), pp. 1–13

doi:10.1093/rpd/ncq155

SURVEY OF PATIENT DOSE IN COMPUTED TOMOGRAPHY IN SYRIA 2009 M. H. Kharita1,* and S. Khazzam2 1 Protection and Safety Department, Atomic Energy Commission, Damascus, PO Box 6091, Syria 2 Radiation Protection and Safety Office, Ministry of Health, Damascus, Syria

Received February 8 2010, revised March 30 2010, accepted April 26 2010 The radiation doses to patient in computed tomography (CT) in Syria have been investigated and compared with similar studies in different countries. This work surveyed 30 CT scanners from six different manufacturers distributed all over Syria. Some of the results in this paper were part of a project launched by the International Atomic Energy Agency in different regions of the world covering Asia, Africa and Eastern Europe. The dose quantities covered are CT dose index (CTDIw), dose-length product (DLP), effective dose (E) and collective dose. It was found that most CTDIw and DLP values were similar to the European reference levels and in line with the results of similar surveys in the world. The results were in good agreement with the UNSCEAR Report 2007. This study concluded a recommendation for national diagnostic reference level for the most common CT protocols in Syria. The results can be used as a base for future optimisation studies in the country.

INTRODUCTION This study is the first one in Syria that included survey of radiation dose from CT scanners. Over the years, several surveys have been carried out trying to estimate not only the collective dose of computed tomography (CT) examinations but also the effective dose for specific scan regions. Only few surveys of large sample size have been carried out, e.g. in the UK 1999, 2001 and 2003(1 – 3); Germany 1992–1995, 1999, 2002(4 – 7); Switzerland 1998(8); Austria 2000(9), USA 2000–2001 (Next surveys) and Japan 2002(10 – 14), while a larger number of surveys with smaller sample sizes can be found in the literature. Large-scale surveys are necessary to take into account the considerable variations in patient size and differences in scan parameters and settings even within the various sites. Surveys with small sample size, showing only a snapshot of the current situation using CT scanners of only one or two vendors, can be found more frequently in medical journals. The larger surveys are all carried out on behalf of national authorities such as National Radiological Protection Board in the UK, Bundesamt fu¨r Strahlenschutz in Germany, Bundesministerium fu¨r soziale Sicherheit und Gesundheit in Austria with a typical time frame of 5–15 y between updates. This work is part of a project launched by the International Atomic Energy Agency (IAEA) in different regions of the world covering Asia, Africa and Eastern Europe. The initial results of the project included 15 CT scanners from this survey in Syria(15 – 18). In this paper, the dose levels to adults and paediatric patients have been assessed and compared with European diagnostic reference levels

(DRLs)(12) and with the results of other surveys over the world. This survey covers 30 CT scanners (6 different manufacturers) from 28 hospitals and clinics covering most cities in Syria. MATERIALS AND METHODS The dose levels for chest, chest high resolution (HR), abdomen, pelvis and head CT examinations for adult and paediatric patients were studied. The dose quantities used were the weighted CT dose index (CTDIw) and the dose-length product (DLP). The effective doses (E) resulting from each procedure were also determined. CT Facilities Thirty CT scanners in 26 public hospitals and 4 private hospitals covered most cities in Syria have been investigated (Figure 1). Dose quantities The CTDIw (in mGy) and the DLP (in mGy) cm are determined for all CT scanners using direct phantom measurements. Head and body Perspex phantoms with one hole in the centre (to measure CTDIc) and four holes in the peripheral (to measure CTDIp) and a 10-cm length ionisation chamber were used (Figure 2). The weighted CTDIw was evaluated using the following formula(19 – 23): CTDIw ¼

1 2 CTDIc þ CTDIp : 3 3

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M. H. KHARITA AND S. KHAZZAM

The DLP was then calculated as follows: DLP ¼ CTDIw scanlength: The E effective dose was calculated by the following: E ¼ DLP CF; where CF is conversion factor, theses conversion factor of effective dose per DLP for various body regions are 0.002, 0.014, 0.014 and 0.015 mSv mGy cm for head, chest, abdomen and pelvis, respectively in adults and 0.003, 0.013, 0.015 and 0.015 mSv mGy cm for head, chest, abdomen and pelvis, respectively in children(3). The CTDIw and DLP were estimated for varying protocols (chest, chest high resolution (HR), abdomen, pelvis and head) for adults and children for each CT scanner. RESULTS AND DISCUSSION There are 255 CT scanners in Syria (2009 estimate), and it is about 9 % of all diagnostic X-ray units in the country (Figure 3). The CT scanners belong to seven global manufacturers listed in Table 1. The

population in Syria is about 19.4 million (2007 estimate), with 60 % adults over 15 y old. This means that the CT scanner density in Syria is about 13.1 CT scanners per 1 million inhabitants. Comparison of the CT density with those of various countries is shown in Figure 4. The CT scanner density in Syria is similar to that of the median density. The substantial sample used in this survey includes reasonable geographical spread of CT scanners in Syria. Table 2 gives detailed analyses for the regional distribution of CT scanners both in the surveyed sample and in the country. Around 50 % of the CT scanners in the surveyed sample were based in and around Damascus (the capital city), with about 13.2 % in the north and middle, the remaining 36.8 % were distributed on coastal, east and south. Overall, the sample included over 13 % of the estimated total of 255 CT scanners in clinical service in Syria during 2009. Table 3 presents the variation in scanner density in the different cities in Syria. All CT scanners in the present survey are of single slice type. The survey has included detailed information for 241 separate scan sequences, related to the five mentioned common protocols for adults and five protocols for paediatric patients (less than 15 y of age). Chest HR and head examination were largely performed using axial scan sequences, other examinations are performed using axial or helical scan modes.

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Figure 1. Geographical distribution of CT scanner sites in survey sample (not to scale). CTs in sample/CTs in governorate.

SURVEY OF PATIENT DOSE IN COMPUTED TOMOGRAPHY

Figure 3. Number of diagnostic units in Syria (2009).

A database has been designed using Microsoft Excel to collect, process and analyse the data from 30 CT scanners. The database contained information about the hospitals and radiologists, workloads (number of patients per year for each protocol) and information about CT scanners (manufacturers, model and date of installation). The parameters of routine examinations stored in the CT machine or used by radiographers were also collected [tube voltage (kVp), tube current

(mA), exposure time (s), slice thickness (mm)] in addition to the mode of scan (axial or helical). The database contained also the measured CTDI using phantoms and the weighted CTDI (CTDIw) using (Nero 8000 with 10-cm pen ionisation chamber), scanlength for region of interest (cm) and number of slices to calculate DLP. The average age of CT scanners in the surveyed sample is about 10 y old; this is similar to the average age of CT scanner in the country.

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Figure 2. Head and body Perspex phantoms and a 10-cm length ionisation chamber.

M. H. KHARITA AND S. KHAZZAM Table 1. Analysis of CT scanner models in survey sample in comparison with distribution of CT scanner in Syria. Manufacturer

Toshiba

Model

Picker Siemens GE Philips Shimadzu Hitashi Total

Number of CT scanners in the country

9 2 4 2 2 2 5 3 1 — 30 (11.8 % of total number)

70 52 46 37 29 17 4 255

Comparison with ImPACT software results The normalised CTDI (nCTDIw) is obtained by dividing the CTDIw value by the mA s that was used to measure CTDIw: n CTDIw

¼

CTDIw : mA s

It is worthwhile (and indeed necessary) to note that the nCTDIw is a characteristic quantity for scanner (dose-rate coefficient), which simply represents the capacity of a scanner in terms of output and which conveys absolutely nothing about patient dose. Very often it is assumed that scanner with a high value of nCTDIw are more ‘dangerous’ than other models with lower nCTDIw values. This is not necessarily the case. References to patient dose cannot be made unless the nCTDIw has been multiplied by mA s, which is required in order to produce images of diagnostic quality with the type of scanner under consideration. Only after having carrying out this step is it possible to decide if a particular scanner delivers more or less dose than other model for a specified type of examination(5). The results in terms of nCTDIw in the survey were compared with ImPACT database results(24). Table 4 illustrates the comparison between nCTDIw survey (measured in this survey) and nCTDIw ImPACT (estimated using ImPACT database) using head phantom. It is clear that some of the results of the survey are not in line with those from ImPACT, the largest differences were 219 % for Siemens and þ36 % for Toshiba (for the head phantom). Table 5 shows a similar behaviour for the comparison results of body phantom, the largest differences in this case were 220 % for Siemens and þ15 % for Toshiba. These

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Asteion X Vision Premier PQ Xtra Somatom Sytec Aura SCT —

Number of CT scanners in the survey sample

differences may have been due to the lack of data about old models (commonly available in Syria) in ImPACT database, which necessitate the use of the data about the nearest models available in ImPACT database. The results may indirectly provide comparison among CT scanners from different manufacturers (currently used in Syria) in terms of doses measured in this survey and those obtained using ImPACT database for head phantom (Figure 5) and for body phantom (Figure 6). The differences can be attributed to the same reasons as in the pervious paragraph. The survey provides a lot of data on examination or scan parameters. CTDIw, DLP and E can be interpreted and compared in different ways. Mean values of common or often used procedures may serve to rank each scanner in comparison with the results of the survey. Median values can be used to evaluate the distribution (for example the skewness or asymmetry) of the data. Of common interest in particular are the third quartile values that can serve as a threshold that should not be exceeded in general(25). These values also provide a well-established base for defining DRL. The third quartile value means that 75 % of the participating institutes and scanner conform to these values, while only 25 % have to change their protocols or procedures. Table 6 presents the values of CTDIw for adults and children in the 30 CT scanners(25). For effective dose, the DLP values were multiplied by CF(3) (as explained in the section Dose quantities), and the results are shown in Table 8. The DRLs shown in Tables 6 – 9 for each CT procedure are taken from the CT European quality criteria (EUR 16262)(12). Table 6 contains sample size, mean value, standard deviation, minimum, maximum and median values, first and third quartile values. The third quartile CTDIw measured in this survey are in some cases not in line with the European DRL for CTDIw. The deviation from European DRLs for adults ranges from 231 % for abdomen to þ1 % for head, the mean deviation for all standard protocols is 218 % (Table 9). On the other hand the deviation for children protocols ranges from 232 % for head to þ37 % for pelvis. The reason of this negative deviation is that some of X-ray tubes in the survey exceeded the maximum number of exposures (in one of the CT scanners the number of exposures was 250 000, while the maximum allowed number of exposures specified by manufacturer was 100 000). This deviation could also be attributed to the slice thickness being in 26 % of CT scanners in the survey larger than the nominal slice thickness. It should be mentioned that DRL are given in term of CTDIw, while the dose values (dose per


slice) are given in term of DLP, which is an integral dose value (dose to the patient). Comparison of DLP from the survey with DLP in European DRLs for adults is shown in Table 7. The deviation ranged from 253 % for chest HR to 25 % for pelvis, and the mean deviation for all standard protocols is 222 % (Table 9). The DLP for child was also compared with European DRLs. The deviations were between 242 % for chest and þ68 % for chest HR. This variation in the results could be due to the deviation in CTDIw (explained earlier) and deviation of scanlength as shown in Table 10. Comparison of average scanlength in Syria with many protocols and scanlength for EUR quality

criteria showed that the difference could vary from 242 % for chest HR in adult and to þ24 % for pelvis in adults, and between 238 % for abdomen and þ 98 % for chest HR in children. This could explain the out layer point of þ68 % in dose for chest HR. The results of this work were also compared with the results of the different similar national surveys. Table 11 shows comparison of DRL CTDIw in Syria with similar international studies. It was clear from this survey that the results are very similar to Germany 2002. Table 12 showed the comparison of DRL for the DLP in Syria and those of other similar national surveys. The comparison indicated

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Figure 4. CT scanner density in various countries reported in UNSCEAR 2007 and Syria (2009).

M. H. KHARITA AND S. KHAZZAM Table 2. Geographical distribution of CT scanners in the survey sample in Syria. Domain

Governorate

North

Scanner in governorate Number

Per cent in Syria

Number

Per cent in sample

Per cent in domain

57 12 18 19 53 28 10 4 1 20 11 7 7 8 255

22.4 4.7 7.1 7.5 20.8 11.0 3.9 1.6 0.4 7.8 4.3 2.7 2.7 3.1

1 1 1 1 15 2 1 2 — 1 — 1 2 2 30

3.3 3.3 3.3 3.3 50 6.7 3.3 6.7

2.9

South

Coastal East

5.4 20.8

3.3

3.3

3.3 6.7 6.7

22.7

Table 3. Geographical distribution of total CT scanners in the Syrian governorates and in the sample. Governorate

Aleppo Edleb Homs Hama Damascus Damascus rural Dara’ AlSwayda AlQunaytera Lattakya Tartous Al Hasakeh AlRaqa Deir Ezzour Total

Number of CT scanners Sample

Total

1 1 1 1 15 2 1 2 — 1 — 1 2 2 30

57 12 18 19 53 28 10 4 1 20 11 7 7 8 255

Per cent

Population (1000)

Population density (thousands person/CT scanner)

22.4 4.7 7.1 7.5 20.8 11.0 3.9 1.6 0.4 7.8 4.3 2.7 2.7 3.1

4393 1359 1647 1491 1669 2487 916 346 79 943 750 1377 854 1094 19 405

77 113 92 78 31 89 92 87 79 47 68 197 122 137

Table 4. Comparison between results of (nCTDIw Manufacturer Picker Toshiba GE Philips Siemens Shimadzu

survey)

with (nCTDIw

ImPACT)

on head phantom (16 cm).

Number

nCTDIw survey

nCTDIw ImPACT

nCTDIw/nCTDIw ImPACT

8 11 5 3 2 1

16.1 18.3 19.8 25.5 21.9 13.5

15.6 13.5 23.2 24.5 26.9 12.9

1.04 1.36 0.85 1.04 0.81 1.04

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Aleppo Edleb Homs Hama Damascus Damascus rural Dara’ AlSwayda Al Qunaytera Lattakya Tartous Al Hasakeh AlRaqa Deir Ezzour Total

Interior

Scanner in sample

SURVEY OF PATIENT DOSE IN COMPUTED TOMOGRAPHY Table 5. Comparison between results of (nCTDIw Manufacturer Picker Toshiba GE Philips Siemens Shimadzu

survey)

with (nCTDIw ImPACT) using body phantom (32 cm).

Number

nCTDIw survey

nCTDIw ImPACT

nCTDIw/nCTDIw ImPACT

8 11 5 3 2 1

11.7 7.0 9.2 12.3 10.8 6.9

11.6 6.1 10.9 12.1 13.5 8.1

1.00 1.15 0.84 1.02 0.80 0.85

Figure 6. Comparison of survey results with ImPACT software using body phantom (32 cm).

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Figure 5. Comparison of survey results with ImPACT software using head phantom (16 cm).

M. H. KHARITA AND S. KHAZZAM Table 6. Statistical analysis of the third quartile of CTDIw for 30 CT units in Syria. CTDIw (mGy) Sample size Adult

28 24 29 25 27 27 13 27 15 26

SD

Minimum

25 %

Median

75 %

Maximum

Refa

16.9 25.7 20.2 23.4 53.5 27.0 37.1 27.3 33.6 35.4

7.8 11.3 8.5 13.2 13.0 14.9 24.0 15.1 18.9 14.8

7.3 12.2 7.3 7.3 27 6.5 10.9 4.9 4.9 7.5

16.0 24.1 19.0 21.1 53.3 24.3 35.1 25.2 32.4 35.5

14.7 23.1 18.5 19.1 52.5 21.8 25.7 21.1 30.7 34.2

22.0 30.5 24.1 27.5 60.7 32.1 39.9 34.2 41.2 47.6

36.9 51.5 45.7 54.5 81.0 73.7 84.5 78.4 78.4 61.6

30 35 35 35 60 30 50 30 30 70

SD, standard deviation. a Ref: reference DRLs (EUR 16262) quality criteria CT. b Dose data for (chest, chest HR, abdomen and pelvis examinations) referred to 32-cm diameter CT dosimetry phantom (and have presently been corrected by multiplication by factor of two in order to allow comparison with 16-cm diameter CT dosimetry phantom).

Table 7. Statistical analysis of the third quartile of DLP for 30 CT units in Syria. DLP (mGy cm) Sample size Adult

Child

Chest Chest HR Abdomen Pelvis Head Chest Chest HR Abdomen Pelvis Head

28 24 29 25 27 27 13 27 15 26

Mean

SD

Minimum

25 %

Median

75 %

Maximum

Reference

396 116 567 465 668 332 127 439 351 375

164 96 338 308 194 179 83 290 240 190

115 28 166 145 345 91 24 86 69 75

389 96 517 398 663 302 120 388 339 362

364 82 477 381 671 278 112 363 262 343

520 133 721 542 793 347 168 525 537 500

753 429 1634 1363 1012 763 304 1247 784 887

650 280 780 570 1050 600 100 800 500 750

SD, standard deviation.

Table 8. Statistical analysis of the third quartile of E for 30 CT units in Syria. E (mSv) Sample size Adult

Child


28 24 29 25 27 27 13 27 15 26

Mean

SD

Minimum

25%

Median

75%

Maximum

Reference

5.4 1.6 7.7 6.8 1.2 4.3 1.7 6.6 5.3 1.2

2.3 1.3 4.6 4.5 0.4 2.3 1.1 4.4 3.6 0.6

1.6 0.4 2.3 2.1 0.6 1.2 0.3 1.3 1.0 0.2

5.3 1.3 7.0 5.9 1.2 3.9 1.6 5.8 5.1 1.2

5.0 1.1 6.5 5.6 1.2 3.6 1.5 5.5 3.9 1.1

7.1 1.8 9.8 8.0 1.4 4.5 2.2 7.9 8.1 1.6

10.3 6.0 22.2 20.1 1.8 9.9 4.0 18.7 11.8 2.8

8.9 3.9 10.6 8.4 1.9 7.8 1.3 12 7.5 2.4

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Childb


Mean

SURVEY OF PATIENT DOSE IN COMPUTED TOMOGRAPHY Table 9. Comparison of DRLs with third quartile in Syria for adult and children.

Adult

Child

Reference

Ratio (%)

DLP (mGy cm)

Reference

Ratio (%)

E (mSv)

Reference

Ratio (%)

22.0 30.5 24.1 27.5 60.7 32.1 39.9 34.2 41.2 47.6

30 35 35 35 60 30 50 30 30 70

227 213 231 221 1 7 220 14 37 232

520 133 721 542 793 347 168 525 537 500

650 280 780 570 1050 600 100 800 500 750

220 253 28 25 224 242 68 234 7 233

7.1 1.8 9.8 8.0 1.4 4.5 2.2 7.9 8.1 1.6

8.9 3.9 10.6 8.4 1.9 7.8 1.3 12 7.5 2.4

220 253 28 25 224 242 68 234 7 233

Table 10. Comparison between scanlength in Syria for many protocols with EUR 16262. Adult

Chest Chest HR Abdomen Pelvis Head

Child

Reference (cm)

Survey (cm)

Deviation (%)

Reference (cm)

Survey (cm)

Deviation (%)

21.7 8 22.3 16.3 17.5

25 5 27 20 13

þ17 242 þ23 þ24 227

20 2 26.7 16.7 10.7

13 4 16 11 11

233 þ98 238 233 þ1

Table 11. Comparison of DRL for CTDIw (mGy) in Syria with international studies. Examination Head Chest Chest HR Abdomen Pelvis

Syria (2009)

Germany (2002)

UK (2003)

Australia (2000)

EUR (1999)

60.7 22 30.5 24.1 27.5

60 22 — 24 28

70 13 22 20 17

68.9 18.9 28 19.8 23.5

60 30 35 35 35

Table 12. Comparison of DRL for DLP (mGy cm) in Syria with international studies. Examination Head Chest Chest HR Abdomen Pelvis

Syria (2009)

Germany (2002)

UK (2003)

Australia (2000)

EUR (1999)

793 520 133 721 542

1175 650 — 1500 750

760 430 80 510 —

1275 484 76 1109 589

1050 650 280 780 570

the obtained DRL is very close of mean values of all other surveys shown in Table 12. Table 13 presents(26) the maximum and the minimum values of CTDIw (mGy), DLP(mGy cm), E (mSv) for adult patients in different countries and the average+ standard deviation of all surveys excluding Syria.

The results of the Syrian survey seem to fit reasonably well with these averages for chest and pelvis whereas for head examination it is not in good agreement. This could be attributed to the fact that only two surveys were included. Table 14 shows(27,28) comparison of the mean values of CTDIw (mGy),

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CTDIw (mGy)

M. H. KHARITA AND S. KHAZZAM Table 13. Maximum and minimum values of [CTDIw (mGy), DLP (mGy cm), E (mSv)] for adult patients in different countries. Year of study

Examination Head

Chest

Pelvis

Minimum Maximum Minimum Maximum Minimum Maximum 1999

UK(1)

1998

Africa(18)

2008

Asia(18)

2008

East Europe(18)

2008

Average (all above results except Syria)+SD Syria

2009

CTDIw DLP E CTDIw DLP E CTDIw DLP E CTDIw DLP E CTDIw DLP E CTDIw DLP E CTDIw DLP E

14 173 0.4 21 231

18+5 200+40 0.4 27 345 0.6

199 2384 14.5 130 2087

5.5 100 1.35 4 72

66 1766 26.4 46.4 1304

6.9 90 1.6 6.8 68

56.2 1349 23 55.2 1324

165+50 2240+210 14.5 81 1012 1.8

9.2 256 3.6 12 223 3.1 6.9 148 2.1 8+3 160+80 3+1 7.3 115 1.6

24.3 933 13 18.6 564 12.2 21.3 833 11.7 35+20 1080+450 16+7 36.9 753 10.3

7.3 163 2.4 16.8 390 5.9 8.3 268 3.5 9+4 200+130 3+2 7.3 145 2.1

26 837 12.6 28.4 545 8.2 21.8 698 7 38+17 950+370 13+7 54.5 1363 20.1


DLP(mGy cm), E (mSv) for adult patients in different countries and the average+standard deviation of all surveys excluding Syria. The results of the Syrian survey seem to be in good agreement with these averages for all types of examinations. The collective effective doses in Syria resulting from CT scanners for adults and children are calculated as shown in Table 15(29). Typical doses from CT scanners in Syria are summarised in Tables 16 and 17, as third quartile values over the whole survey for CTDIw, DLP and E for standard protocols. These results can be used as a recommendation for national DRL (NDRL) for the most common CT protocols in Syria. The CTDI and DLP were rounded to the nearest 5 to obtain the NDRLs (as used by the European Guideline 16262), but not for the effective dose due to the lower value, E has been rounded to the nearest one decimal point.

doses to patient in CT in Syria have been investigated and compared with similar studies in different countries. This work surveyed 30 CT scanners from 6 different manufacturers distributed all over Syria. Typical doses from CT scanners in Syria are summarised in Tables 16 and 17, as third quartile values over the whole survey for CTDIw, DLP and E for standard protocols. It was found that most CTDIw and DLP values were similar to the European reference levels and in line with the results of similar surveys in the world. The results were in good agreement with those reported in various national surveys and with the UNSCEAR Report 2007. This study concluded a recommendation for NDRLs for the most common CT protocols in Syria. The results can be used as a base for future optimisation studies in the country.

ACKNOWLEDGEMENT CONCLUSION Surveys are necessary to define DRLs. They should be carried out on a large scale, because small-scale surveys just result in a snapshot of the current situation in the participating institutes. The radiation

The authors wish to thank Prof Ibrahim Othman director of Atomic Energy Commission in Syria for his support. The thanks are also extended to the IAEA and specially Dr. Madan Rehani for his support and the coordination of the project in medical exposure control launched by the IAEA in

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Germany(26)

SURVEY OF PATIENT DOSE IN COMPUTED TOMOGRAPHY Table 14. Mean [CTDIw (mGy), DLP (mGy cm), E (mSv)] values for adult patients in different countries. Year of study

1999

Germany(7)

2002

Greece(27)

2002

Italy

2002

Italy(28)

2006

UK(3)

2003

Australia(9)

2000

Average (all above results except Syria)+SD Syria

2009

CTDIw DLP E CTDIw DLP E CTDIw DLP E CTDIw DLP E CTDIw DLP E CTDIw DLP E CTDIw DLP E CTDIw DLP E CTDIw DLP E

Head

Chest

Abdomen

Pelvis

57 676 1.8 58.4 1016 2.8 68 919 2.1 59 707 1.6 59.6 — 1.7 57 690 1.5 57.7 1036 2.25 60+4 840+170 2+0.5 53.5 668 1.2

18 420 6.5 14.8 350 5.7 21 430 7.3 21 480 6.2 19.7 — 8 14 400 5.8 16.2 400 6.7 18+3 410+40 7+1 16.9 396 5.4

21 — — — — — 23 493 7.4 23 632 8.3 24.3 — 7.8 16 350 5.3 17.5 877 14.7 21+3 600+220 9+4 20.2 567 7.7

23 480 8 17.1 398 7.2 27 540 10.3 24 434 8.2 24.9 — 8.9 — — — 20.2 487 8 23+4 470+50 8+1 23.4 465 6.8


Table 15. Estimate of collective effective dose in Syria-related CT scanners. Adult Sample size

Annual workload

Chest 25 19 357 Abdomen 25 22 582 Head 25 48 459 Collective dose of CT scanners in sample Annual workload 111 052 patients/y Collective effective dose 298 255/25¼3040 man Sv Population in Syria 11.740.000 Collective dose 0.26 man mSv Collective dose

Child Collective dose (man Sv) 99 149 50 298

Sample size

21 20 25

Annual workload

Collective dose (man Sv)

4312 4522 21 243

8 15 11 33

35 482 patients/y 33 255/22¼383 man Sv 7.665.000 0.05 man mSv

0.31 man mSv

different regions of the world covering Asia, Africa and Eastern Europe. The thanks are also due to Dr. Maher Al Hosami (ex-minister of Health) and Dr. Reda Saeed Minister of Health, Dr. Deeb Hazemah (ex-assistant minister), Dr. Jamal AlWadi, Assistant

of Minister of Health, Prof. Mohammad Saeed Mahasneh, Head of Physics Department in Damascus University, Mr Khaled Wali, Eng. Ammar Chaker, Mr. Majed Omar, Mr. Qusai Abdulla, Eng. Noor Orabi, Eng. Ahmad Al asmar

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Germany(26)

Examination

M. H. KHARITA AND S. KHAZZAM Table 16. National dose reference levels in Syria for adult. CTDIw (mGy)

DLP (mGy cm)

E (mSv)

20 30 25 30 60

520 135 720 540 900

7.1 1.8 9.8 8.0 1.4


Table 17. National dose reference levels in Syria for children. CTDIw (mGy)

DLP (mGy cm)

E (mSv)

30 40 35 40 50

350 175 525 550 500

4.5 2.2 7.9 8.1 1.6


NDRLs in Syria for children.

from Ministry of health, Dr. Fustino Bonoti from Italy, Dr. Colin Martin from Scotland, Dr. Rento Padovani from Italy, Mr. Abdul Qader Sadeea, Dr. Adel Shanan, Dr. Saeed Howayja, Dr. Yaser Safi, Dr. Mustafa Dakak, Dr. Yousef Berro, Dr. Asem Okar, Dr. Wedad Meda’, Dr. Mohammad Taleb and everyone who helped in this work.

REFERENCES 1. National Radiological Protection Board. Guidelines on patient dose to promote the optimisation of protection for diagnostic medical exposures. NRPB Vol. 10(1) (1999). 2. Hart, D. and Wall, B. F. Radiation exposure of the UK population from medical and dental X-ray examinations. NRBP-W4 (2001). 3. Shrimpton, P. C. and Hillier, M. C. Doses from computed tomography (CT) examination in the UK. NRPB-W67 (2003). 4. Bernhardt, J., Veit, R. and Bauer, B. Erhebung zur Strahlenexposition der Patienten bei der Rntgendiagnostik. Z. Med. Phys. 5, 33– 39 (1995). 5. Nagel, H. D. Radiation exposure in computed tomography, fundamentals, influencing parameters, dose assessment, optimization, scanner data, terminology. Med. Phys. 29(8), 1922– 1922 (2002). 6. Brix, G., Lechel, U., Veit, R., Truckenbrodt, R., Stamm, G., Coppenrath, E. M., Griebel, J. and Nagel, H. D. Assessment of a theoretical formalism for dose estimation in CT, an anthropomorphic phantom study. Eur. Radiol. 14, 1275– 1284 (2004).

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NDRLs in Syria for adult.

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