Estimation of adult patient doses for common diagnostic X-ray examinations in Rio de Janeiro, Brazil

Physica Medica (2008) 24, 21e28

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ORIGINAL PAPER

Estimation of adult patient doses for common diagnostic X-ray examinations in Rio de Janeiro, Brazil O.A. Osibote a,b, A.C.P. de Azevedo b,* a

Department of Physics, Olabisi Onabanjo University, Nigeria FIOCRUZ e Escola Nacional de Sau´de Pu´blica Se´rgio Arouca e CESTEH, Pre´dio 1 de Maio sala 2, Rua Leopoldo Bulho˜es 1480, Manguinhos, 21041-210, Rio de Janeiro, Brazil b

Received 12 July 2007; received in revised form 24 October 2007; accepted 10 November 2007

KEYWORDS Entrance skin dose; DoseCal software; Effective dose; Adult radiographs

Abstract DoseCal software has been used to evaluate the Entrance Surface Dose (ESD) and Effective Dose (ED) of adult patients undergoing abdomen, cervical spine, chest, lumbar spine and skull diagnostic X-ray examinations in AP, PA and LAT projections. The survey was carried out in nine hospitals in Rio de Janeiro state with a total of 1917 radiographs. The mean values of ESD (mGy) and ED (mSv) were recorded. Although the results obtained are below the international diagnostic reference levels, they present large variations within and between hospitals which reflects the disparity of radiographic techniques used in the examinations. The results were compared with the European Community Reference Levels. Even though in Brazil there are specific legislations on radiation protection and implementation of Quality Assurance Programs (QAPs) in all medical institutions, there is still a need for personnel training and national guidance on good practice for optimization of patients’ doses. ª 2007 Published by Elsevier Ltd on behalf of Associazione Italiana di Fisica Medica.

Introduction The increasing knowledge of the hazards of ionising radiation has led to the need for radiation dose assessment of patients during diagnostic X-ray examinations. The International Commission on Radiological Protection, ICRP

* Corresponding author. Tel./fax: þ55 21 2487 7228. E-mail address: [email protected] (A.C.P. de Azevedo).

[1] defined the stochastic radiation effects as a lethal cancer or a mutation expressed in the first two post-irradiation generations. Diagnostic imaging has an increasing role in medicine with approximately 5% growth per year with worldwide annual per caput dose of 0.4 mSv [2]. The development of practical methods for patient dose assessment in Radiology is desirable since Quality Assurance Programs (QAPs), including patient dosimetry, are a legal requirement now-a-days in most countries, including Brazil. A QAP in diagnostic radiology includes the patient dosimetry

1120-1797/$ - see front matter ª 2007 Published by Elsevier Ltd on behalf of Associazione Italiana di Fisica Medica. doi:10.1016/j.ejmp.2007.11.002

22 Table 1

O.A. Osibote, A.C.P. de Azevedo Patient information and mean exposure parameters

Exam projection

Abdomen

Cervical spine

AP

AP

Chest LAT

Lumbar spine AP

Skull

PA

LAT

LAT

73 10.3 150 51 64

85 18.2 143 51 64

74 59.8 89 48 69

83 80.8 84 48 69

PA

Hospital A kV mAs FSD (cm) Age (years) Weight (kg) Filtration

74 47.4 97 57 66 3.00 mmAl

Hospital B kV mAs FSD (cm) Age (years) Weight (kg) Filtration

71 56 26.4 22.8 123 100 35 36 59 69 2.00e2.50 mmAl

)) )) )) )) ))

69 8.2 154 48 65

82 15.8 150 48 65

70 27.3 105 48 64

76 32.8 110 35 61

Hospital C kV mAs FSD (cm) Age (years) Weight (kg) Filtration

)) 72 )) 18.0 )) 123 )) 44 )) 66 2.50e3.00 mmAl

73 18.3 114 44 66

73 15.5 121 47 66

85 23.6 109 47 66

76 26.2 87 47 68

86 35.3 78 47 68

76 24.7 102 33 61

Hospital D kV mAs FSD (cm) Age (years) Weight (kg) Filtration

76 39.6 94 52 66 3.50 mmAl

65 12.7 110 52 69

66 13.7 120 52 69

75 5.2 151 46 68

85 10.7 153 46 68

71 38.1 109 54 70

83 56.0 105 54 70

73 21.0 92 40 66

Hospital E kV mAs FSD (cm) Age (years) Weight (kg) Filtration

64 88.6 96 47 56 2.50 mmAl

68 39.7 136 43 68

68 40.7 138 43 68

83 8.5 162 52 63

95 16.4 157 53 63

)) )) )) )) ))

)) )) )) )) ))

95 64.6 87 51 66

Hospital F kV mAs FSD (cm) Age (years) Weight (kg) Filtration

67 59.1 88 46 62 2.1e3.4 mmAl

60 66.8 91 46 67

)) )) )) )) ))

70 15.4 124 44 67

)) )) )) )) ))

71 95 73 56 65

83 152.7 64 51 68

66 80.9 76 41 70

Hospital G kV mAs FSD (cm) Age (years) Weight (kg) Filtration

81 43.6 117 37 67 2.00e4.00 mmAl

73 17.4 91 46 65

73 17.5 96 46 65

80 11.8 121 44 66

)) )) )) )) ))

86 48.6 94 45 69

95 74.2 93 45 70

78 30.9 87 32 65

Hospital H kV mAs FSD (cm)

)) )) ))

71 55.5 124

71 34.7 119

70 36.3 120

)) )) ))

72 132.0 82

64 32.8 95 46 64

65 22.5 93 46 66

81 188 76

69 41.1 99 43 63

)) )) )) )) ))

)) )) ))

Estimation of adult patient doses for common diagnostic

23

Table 1 (continued ) Abdomen

Cervical spine

Exam projection

AP

AP

Age (years) Weight (kg) Filtration

)) 61 )) 64 1.93e3.20 mmAl

Hospital I kV mAs FSD (cm) Age (years) Weight (kg) Filtration

66 36.1 85 32 70 3.30 mmAl

)) )) )) )) ))

Chest LAT 61 64

)) )) )) )) ))

PA

Lumbar spine LAT

AP

Skull LAT

PA

46 62

)) ))

53 70

53 70

)) ))

79 4.6 160 51 70

)) )) )) )) ))

65 39 85 50 70

)) )) )) )) ))

)) )) )) )) ))

))Missing data for projections not used/available in some hospitals during the period of this evaluation.

as one of the most relevant items to be assessed together with the image quality. An extensive literature on the design and implementation of QAP for diagnostic radiology exists [3]. Quality Assurance (QA) is a program used by management to maintain the optimal diagnostic image quality with minimum hazards and sufferings to patients. The European Union Council Directive 97/43/Euratom introduces the concept of Diagnostic Reference Levels (DRL) [4], defined as dose levels in medical radiodiagnostic practices to patients of standard-sized groups or standard phantoms, for typical examinations and broadly defined types of equipment. These levels should not be exceeded for standard procedures when good and normal practice is applied, regarding diagnostic and technical performance. Wide variations in patient doses up to a factor of 100 for radiation exposure for the same type have been reported in the literature [5e7]. Reference dose levels provide a framework to reduce this variability [8,9]. Variations of dose within a hospital emphasize the importance of QAP so that inconsistencies and errors in technique and equipment can be discovered early and then reduce the variation in dose to patients. In 1998, the Brazilian Sanitary Surveillance and the Ministry of Health of Brazil published the decree 453 (DOU 1998) [10] establishing radiation protection guidelines for diagnostic radiology in Medicine and Odontology. Among the legal requirements contained in that decree, is the mandatory implementation of QAP in all medical institutions that use ionising radiation.

Material and methods The aim of this work was to estimate the Entrance Skin Dose (ESD) and the Effective Dose (ED) for several kinds of exposures of adult patients. Measurements were performed in a wide range of hospitals by using different X-ray equipment and examination techniques. The most common types of examinations were included in the survey, such as abdomen AP, chest PA and LAT, cervical spine AP and LAT, lumbar spine AP and LAT and skull PA. Only diagnostically acceptable images were included in the study. Patients involved in the study were preselected by age (above 15 years), and weight (45e94 kg). All patients who fulfilled these criteria and who underwent a particular examination

at the time of the study were included in the survey. For good statistical analysis, reference was needed for 10 patients (minimum) [4] at each X-ray unit for every examination. For each patient and X-ray equipments, the following parameters were recorded: sex, age, weight, focus-to-skin distance, kVp and mAs. This survey was carried out in nine (eight public, one private) hospitals with a total of 19 rooms from various municipal regions of Rio de Janeiro state. A total of 1917 radiographs were included in this study with the chest PA examinations (713 radiographs) being the most common (37%) and abdomen AP (85 radiographs) being the least (4.4%). The X-ray equipments which were all analogue systems were from Siemens, model RG 150/100 GL, Intecal CR 125, CGR, Dinan AF 500, Medicor R-3 DR 154-3, General Electric, RORIX DR 154-3 and Philips. The film-screen combination was 400 and the total filtration in each X-ray equipment was measured with the NERO 8000. Filtration ranged from 2.00 to 3.5 mmAl. In order to increase the speed and efficiency of patient dosimetry process, a windows based computer program, called DoseCal was used in this study. This software has been developed to generate the ESD as well as the ED. The DoseCal software was designed by the Radiological Protection Center of Saint George’s Hospital, London [11]. The programme is fast and enables the processing of a large volume of data and serves as a realistic alternative method to Thermoluminescent Dosemeters (TLDs) measurements calculating the ESD and ED from exposure factors recorded at the time of the examination. For the DoseCal software, the tube output of all X-ray equipment was measured using calibrated ionisation chambers: Radcheck Plus X-rays exposure meter and Nero 8000Inovision. The tube calibration was performed at 1 m and 10 mAs. Once the tube potential, the tube current, the exposure time and the focus-to-skin distance are known, the ESD can be calculated from Eq. (1) [12].  ESDZOutput 

2  2 kV 100 mAs  BF 80 FSD

ð1Þ

where Output is the output of the X-ray tube in mGy/mAs at 80 kV at a distance of 1 m normalised to 10 mAs, kV is the tube potential, mAs is the product of the tube current

24

O.A. Osibote, A.C.P. de Azevedo

and the exposure time, FSD is the focus-to-skin distance and BF is the back scatter factor. The details of the software have been fully described in a previously published paper [13] and the reliability of using the software has been proven previously [14].

Table 2

Results and discussion Patients’ information and exposure parameters e the range of the tube potential kV, currentetime product mAs, focusto-skin distance FSD and filtration used are shown in

Mean values of ESD (mGy) and ED (mSv) for five routine X-ray examinations

Examination projections

Abdomen

Cervical spine

Chest

Lumbar spine

Skull

AP

AP

LAT

PA

LAT

AP

LAT

PA

Hospital A ESD SD Sample size ED

1.49 1.28 20 0.20

0.68 0.76 16 0.03

0.44 0.28 14 0.002

0.10 0.03 153 0.01

0.29 0.13 68 0.02

1.98 1.27 30 0.20

3.37 2.92 35 0.10

0.81 0.38 10 0.01

Hospital B ESD SD Sample size ED

0.92 0.51 10 0.10

0.91 0.12 10 0.03

)) )) )) ))

0.18 0.07 55 0.02

0.50 0.32 56 0.04

1.86 0.78 11 0.16

2.26 1.33 10 0.05

)) )) )) ))

Hospital C ESD SD Sample size ED

)) )) )) ))

0.41 0.17 30 0.02

0.51 0.27 31 0.003

0.37 0.15 142 0.04

1.02 0.35 61 0.7

1.61 0.69 76 0.18

3.25 1.56 74 0.6

1.31 1.18 24 0.01

Hospital D ESD SD Sample size ED

1.55 1.47 10 0.21

0.20 0.15 12 0.01

0.18 0.09 10 0.001

0.07 0.08 95 0.01

0.18 0.16 80 0.02

0.77 0.44 15 0.08

1.86 1.45 16 0.04

0.48 0.13 37 0.004

Hospital E ESD SD Sample size ED

4.28 0.94 10 0.46

1.05 0.65 14 0.04

0.98 0.53 15 0.01

0.19 0.07 66 0.02

0.54 0.18 61 0.05

)) )) )) ))

)) )) )) ))

3.25 0.78 10 0.02

Hospital F ESD SD Sample size ED

0.96 0.45 11 0.10

0.65 0.27 12 0.03

)) )) )) ))

0.13 0.09 79 0.01

)) )) )) ))

1.92 0.96 12 0.20

5.02 3.56 11 0.15

1.19 0.30 30 0.01

Hospital G ESD SD Sample size ED

1.93 1.23 10 0.25

0.72 0.34 25 0.03

0.67 0.36 23 0.01

0.36 0.21 55 0.04

)) )) )) ))

3.03 1.72 33 0.38

5.38 2.61 31 0.19

1.67 1.01 43 0.01

Hospital H ESD SD Sample size ED

)) )) )) ))

0.94 0.51 10 0.04

1.00 0.54 10 0.01

0.64 0.37 10 0.06

)) )) )) ))

10.13 8.63 13 0.97

18.58 8.08 13 0.44

)) )) )) ))

Hospital I ESD SD Sample size ED

1.65 0.53 14 0.19

)) )) )) ))

)) )) )) ))

0.09 0.02 58 0.01

)) )) )) ))

1.78 0.60 27 0.17

)) )) )) ))

)) )) )) ))

))Missing data for projections not used/available in some hospitals during the period of this evaluation.

Estimation of adult patient doses for common diagnostic

25 projections, respectively) was previously reported from Sao Paulo city of Brazil [15,16]. From literature, there are different factors that could be attributable to the difference between hospital dose values, among which are radiographic equipments, the choice of exposure factors, FSD, collimation, film-screen speed, the processing chemicals and processing conditions [17,18]. Three of the nine hospitals studied give the mean ESD values for chest PA above the international reference levels (hospitals C, G, and H) and one hospital gives ESD value for lumbar spine AP slightly higher than the reference level (hospital H). Some of the reasons for these high doses could be accounted for from the radiographic technical parameters (kV, mAs and FSD) used in these hospitals

Table 1. Missing data appear as ())) for projections not used/available in some hospitals during the period of this evaluation. Only three of the X-ray equipments have filtration below 2.5 mmAl. The filtration for each X-ray equipment was calculated automatically with the use of the NERO 8000 system, by using its appropriate aluminium filters. To obtain an estimation of the patients’ dose values, adult measurements were made on a representative sample of patients with a mean weight of 66 kg. The descriptive statistics of ESD (mGy), mean, standard deviation and the mean ED (mSv) are given in Table 2. It was observed that there is a wide variation in patient dose within and between hospitals. A large variation of ESD for chest examinations (range 0.07e0.6 mGy and 1.30e4.01 mGy for AP and LAT

Box Plot for Abdomen AP Median; Box: 25 -75 ; Whisker: NonOutlier Range

Box Plot for Cervical spine LAT Median; Box: 25 -75 ; Whisker: Non-Outlier Range 2.6

6

2.4 2.2

5

2.0 1.8

ESD (mGy)

ESD (mGy)

4

3

2

1.6 1.4 1.2 1.0 0.8 0.6 0.4

Median 25 -75 Non-Outlier Range Outliers Extremes

0.2

1

0.0 -0.2

0

-1

Median 25 -75 Non-Outlier Range Outliers

A B D E F G I

A

C

D

E

G

H

Hospital

Hospital Box Plot for Cervical spine AP Median; Box: 25 -75 ; Whisker: NonOutlier Range

Box Plot for Chest PA Median; Box: 25 -75 ; Whisker:NonOutlier Range

2.6

1.4

2.4 1.2 2.2 1.0

2.0

ESD (mGy)

1.8

ESD (mGy)

1.6 1.4 1.2

0.8 0.6 0.4

1.0 0.2

0.8 0.6

0.0

0.4 0.2 0.0 -0.2

A B C D E F G H

Median 25 -75 Non-Outlier Range Outliers Extremes

-0.2

A B C D E F G H

I

Median 25 -75 Non-Outlier Range Outliers Extremes

Hospital

Hospital

Figure 1

The Box and Whisker plot for all the five routine diagnostic X-ray examinations and projections.

26

O.A. Osibote, A.C.P. de Azevedo Box Plot for Chest LAT Median; Box: 25 -75 ; Whisker: NonOutlier Range 1.6

Box Plot for Lumbar spine LAT Median; Box: 25 -75 ; Whisker: NonOutlier Range

1.4

35

1.2

30

1.0

25

0.8

20

ESD (mGy)

ESD (mGy)

1.8

0.6 0.4

15 10 5

0.2 Median 25 -75 Non-Outlier Range Outliers Extremes

0.0 -0.2

A B

C D

E

Median 25 -75 Non-Outlier Range Outliers Extremes

0 -5

A

B

C

D

F

G H

Hospital

Hospital Box Plot for Lumbar spine AP Median; Box: 25 -75 ; Whisker: NonOutlier Range

Box Plot for Skull PA Median; Box: 25 -75 ; Whisker: NonOutlier Range

28 26 24

4.5

22 4.0

20

3.5

16 3.0

14

ESD (mGy)

ESD (mGy)

18

12 10 8

2.5 2.0 1.5

6 4

1.0 Median 25 -75 Non-Outlier Range Outliers Extremes

2 0 -2

A B C D F G H I

0.0

A

Hospital

C

D

E

F

G

Hospital

Figure 1

Table 3

Median 25 -75 Non-Outlier Range Outliers Extremes

0.5

(continued).

Distribution of ESD (mGy), maximum to minimum ratios and interquartile range of ESD

Radiograph

Projection

Min.

Mean

Max.

Ratio max./min.

Ratio third/ first quartile

Ratio max./min. of mean ESD among hospitals

Abdomen Cervical spine

AP AP LAT PA LAT AP LAT PA

0.2 0.075 0.055 0.019 0.03 0.14 0.18 0.26

1.75 0.64 0.6 0.19 0.48 2.37 4.75 1.26

5.26 2.47 2.33 1.25 1.73 26.1 33.4 4.32

27.0 33.0 42.4 65.8 63.8 186.4 185.6 16.9

2.91 2.55 2.33 3.01 3.24 2.14 2.30 3.15

4.7 5.3 5.6 9.1 5.7 13.2 10.0 6.8

Chest Lumbar spine Skull

Estimation of adult patient doses for common diagnostic

27

(Table 1), it is well known that ESD is proportional to the tube current, the length of exposure, the square of the peak voltage and the distance between X-ray source and patient. The use of higher peak kilovoltages increases beam penetration and this may allow the use of a lower tube current, thus reducing the dose, also increasing the FSD reduces the dose greatly, for example, if the FSD is doubled, the dose will be reduced by a factor of four. Fig. 1 shows the box plot of the examination and projection studied. The figure illustrates the median, the outliers and the extremes of the classic box where the superior level of the box represents the 75% values and the lower level represents the 25% values. The coefficient of the outlier is equal to 1.5. The wide variations on ESD are due to several factors specially for the fact that the radiographers do not use standardized radiographic techniques (kV, mAS, etc.) and also because the X-ray equipment are not regularly checked, are old and are not subjected to preventive maintenance. A factor that can contribute for high doses is that the majority of the X-ray equipment are quite old (more than 15e20 years of use). Table 3 shows the maximum/minimum ratio of ESD of individual patients, maximum/minimum ratio of mean ESD among hospitals, ratio of the third quartile to the first quartile. Maximum/minimum ratio of ESD for individual patients ranged from 17 for skull PA to 186 for lumbar spine AP and LAT. The range of the ratio of maximum/minimum mean hospital dose varies from a factor of 4.7 for abdomen AP to a factor of 13.2 for lumbar spine AP which shows that the mean hospital dose values exhibited less variation compared to the individual patient doses. Lumbar spine presented highest ratio due to the use of higher mAs in one hospital compared to other hospitals. The interquartile value for individual patients does not vary greatly; the range varies from 2.14 for lumbar spine AP to 3.20 for chest LAT (Table 3). Table 4 shows the distribution of kV and FSD (cm) and comparison with the EC recommendations. The technical factors used are either too low or too high for some procedures. This study presented maximum values of 125 kV and 180 cm for chest PA and LAT, these values correspond to the EC recommended mean values. Also, lumbar spine AP/LAT and skull PA presented higher maximum kV values and lower FSD than recommended. Table 5 gives the comparison of ESD with the internationally established reference dose values (in mGy). The mean third quartile for all the examinations and projections

Table 5

Table 4 Distributions of kV and FSD and comparison with EC recommendations Exam

Abdomen Cervical spine Chest Lumbar spine Skull

Projection kV

AP AP LAT PA LAT AP LAT PA

FSD (cm)

This study

EC

This study

EC (FFD)

52e96 50e80 50e85 48e125 70e125 58e107 55e125 52e90

e e e 125 125 75e90 80e95 70e85

70e180 75e185 63e185 90e185 90e180 50e150 40e150 66e152

e e e 140e200 140e200 100e150 100e150 100e150

for all the hospitals studied do not exceed the reference levels.

Conclusion The result of this study showed lower exposure levels when compared with the international diagnostic reference values, in some radiology departments. However, a significant dose reduction can further be achieved when adhering to the simple guidelines of a good radiographic technique. On the other hand, it was observed that there was a wide variation in patient doses for the same type of examination. It was mostly caused by the lack of standardization on the radiographic technique and equipment performance. The results show the need for changes in the working procedures and equipments used. It is necessary to investigate the reason for higher dose levels in some hospitals so as to review and reduce it. Training facilities for the medical and technical staff are also necessary. These facts could be achieved if the radiology departments implement QAP and establish national and/or regional diagnostic reference levels. This would promote a reduction on the variability of ESD as well as aid in the optimization of radiation protection so as to keep the patient doses low as reasonably achievable. Reference values would provide reliable data for comparison with the radiation exposure levels from every radiographic facility in Brazil and to identify those practices in most urgent need of investigation and corrective actions.

Comparison of ESD with internationally established reference dose values (in mGy)

Exam

Projection

This study, third quartile values

UK IPSM (1992) [19]

IAEA (BSS) (1996) [20]

EC (1996a) [21] (1999a) [4]

NRPB (1999) [22]

Abdomen Cervical spine

AP AP LAT PA LAT AP LAT PA

2.26 0.82 0.76 0.24 0.62 2.60 4.75 1.55

10 e e 0.3 1.5 10 30 5

10 e e 0.4 1.5 10 30 5

e e e 0.3 1.5 10 30 5

10 e e 0.3 1.5 10 30 5

Chest Lumbar spine Skull

28

Acknowledgments The authors would like to acknowledge the financial support of Fundac ¸a ˜o Oswaldo Cruz, Brazil (PAPES III project), postgraduate fellowship from the Third World Organization for Women in Science (TWOWS) and to the Associateship Scheme of the International Centre for Theoretical Physics, Trieste, Italy. Also, we are greatly indebted to The Radiological Protection Centre-Saint George’s Hospital, London for the generous donation of the DoseCal software.

References [1] ICRP. Recommendations of the international commission on radiological protection. 60 Ann. ICRP 21 (1e3). Oxford: Pergamon: ICRP Publications; 1991. [2] UNSCEAR. Report sources and effects of ionizing radiation. vol. 1; 2000. [3] Lindskoug BA. Exposure parameters in X-ray diagnostics of children, infants and the newborn. Radiat Prot Dosimetry 1992;43(1e4):289e92. [4] EC. Guidance on diagnostic reference levels (DRLs) for medical exposures. Radiation protection 109. Directorate-General, Environment, Nuclear Safety and Civil Protection. European Commission; 1999a. [5] Shrimpton PC, Wall BF, Jones DC, Fisher ES, Hillier MC, Kendall GM, et al. A national survey of doses to patients undergoing a selection of routine X-ray exposures in English hospitals. NRPB e R 200. London: HMTO; 1986. [6] Faulkner K, Corbett RH. Reference doses and quality in medical imaging. Br J Radiol 1998;71:100e2. [7] Ng K-H, Rassiah P, Wang H-B. Doses to patients in routine X-ray examinations in Malaysia. Br J Radiol 1998;71:654e60. [8] Contento G, Malisan MR, Padovani R, Maccia C, Wall BF, Shrimpton PC. A comparison of diagnostic radiology practice and patient exposures in Britain, France and Italy. Br J Radiol 1988;61:143e52. [9] Warren-Forward HM, Millan JS. Optimization of radiological technique for chest radiography. Br J Radiol 1995;68:1221e9.

O.A. Osibote, A.C.P. de Azevedo [10] Diretrizes de Protec ¸˜ ao Radiolo ´gica em Radiodiagno ´stico Me ´dico Odontolo ´gico 1998 Portaria 453 do Ministe ´rio da Sau ´de, D O U 103, 01/06/98. [11] Kyriou JC, Newey V, Fitzgerald MC. Patient doses in diagnostic radiology at the touch of a button. London, United Kingdom: The Radiological Protection Center, St. George’s Hospital; 2000. [12] Davies M, McCallum H, White G, Brown J, Helm M. Patient dose audit in diagnostic radiography using custom designed software. Radiography 1997;3:17e25. [13] Azevedo ACP, Osibote OA, Boechat MCB. Paediatric X-ray examinations in Rio de Janeiro. Phys Med Biol 2006;51:3723e32. [14] Mohamadain KEM, Azevedo ACP, da Rosa LAR, Guebel MRN, Boechat MCB. Dose measurements using thermoluminescent dosimeters and DoseCal software at two paediatric hospitals in Rio de Janeiro. Appl Radiat Isot 2003;59:53e7. [15] Fretais MB, Yoshimura EM. An overview of doses to patients and irradiation conditions of diagnostic chest X-ray examinations carried out in hospitals of the city of Sa ˜o Paulo, Brazil. Radiat Prot Dosimetry 2003;103(2):141e8. [16] Fretais MB, Yoshimura EM. Dose measurements in chest diagnostic X-rays adult and paediatric patients. Radiat Prot Dosimetry 2004:1e7. doi:10.1093/rpd/nch363. [17] Muhogora WE, Nyanda AM. The potential for reduction of radiation doses to patients undergoing some common X-ray examinations in Tanzania. Radiat Prot Dosimetry 2001;94(4):381e4. [18] Bogucarskis K, Salmins A, Gfirtner H, Anatschkowa E. Estimation of patient doses for common diagnostic X-ray examinations in Latvian hospitals, analysis of radiographic techniques and comparison with European guidelines. Radiat Prot Dosimetry 2005;114(1e3):176e9. [19] IPSM (Institute of Physical Sciences in Medicine). National protocol for patient dose measurements in diagnostic radiology. Dosimetry Working Party; 1992. [20] IAEA. International basic safety standards protection against ionizing radiation and for the safety of radiation sources. IAEA safety series no. 115; 1996. [21] EC. European guidelines of quality criteria for diagnostic images. Eur 16260 EN. European Commission; 1996. [22] NRPB. Guidelines on patient dose to promote optimization of protection for diagnostic medical exposures. Documents of the NRPB. vol. 10. no. 1; 1999.