RADIATION DOSES TO PATIENTS UNDERGOING BARIUM MEAL AND BARIUM ENEMA EXAMINATIONS

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1 Radiation Protection Dosimetry (2004), Vol. 109, No. 3, pp. 243±247 DOI: /rpd/nch047 RADIATION DOSES TO PATIENTS UNDERGOING BARIUM MEAL AND BARIUM ENEMA EXAMINATIONS M. G. Delichas 1, K. Hatziioannou 2,, E. Papanastassiou 1, P. Albanopoulou 3, E. Chatzi 4, A. Sioundas 1 and K. Psarrakos 1 1 Medical Physics Department, Medical School, Aristotle University of Thessaloniki, Thessaloniki, Greece 2 Medical Physics Department, Papageorgiou Hospital, N. Efkarpia, Thessaloniki, Greece 3 Department of Surgery, `G Gennimatas' Hospital, Ethnikis Amynis 41, Thessaloniki, Greece 4 Department of Surgery, Regional Hospital of Larissa, Tsakalof 1, Larissa, Greece Received December , amended March , accepted March The radiation doses received by patients during 41 barium meal (BM) and 42 barium enema (BE) examinations in two Greek hospitals are presented. Radiation dose was measured in terms of the dose area product (DAP). The effective dose and doses to certain organs were estimated using the ODS-60 software. Mean total DAP values were found to be Gy cm 2 for BM and Gy cm 2 for BE examinations, whereas the estimated mean values of effective dose were and msv respectively. DAP to effective dose conversion coef cients were estimated to be 0.34 msv per Gy cm 2 for BM and 0.41 msv per Gy cm 2 for BE. INTRODUCTION It is generally recommended that dosimetry should be performed regularly to evaluate the potential for optimisation of the radiation dose received by the patients (1). Radiological examinations, such as barium meal (BM) and barium enema (BE), include a combination of a uoroscopy screening and a number of radiographic exposures, all of which result in high radiation doses to patients (2±5). Signi cant dose variations have been observed in both BM and BE examinations, which have been attributed to various parameters such as complexity characteristics, radiologist experience and differences in examination procedures and X-ray equipment performance (6,7). The effective dose, E, introduced by the ICRP (1), has been widely used as a risk-related factor to assess radiation detriment. An estimation of the effective dose can be obtained from measurements of the dose area product (DAP) (8,9). DAP measurements are a valuable and convenient method for dose assessment, especially for dynamic procedures, such as BM and BE, in which beam direction and exposure parameters are continuously varying. In the present study, the radiation doses received by 41 patients who underwent BM and 42 patients who underwent BE examinations in two Greek hospitals were assessed. The effective doses were estimated using the ODS-60 software (10). Comparisons between procedures performed by specialists and trainees were attempted. Corresponding author: hatzikim@hol.gr MATERIALS AND METHODS Patient dose measurements were performed in two Greek public hospitals: G. Gennimatas General Hospital of Thessaloniki (hospital A) and Regional General Hospital of Larissa (hospital B). A total of 41 patients (19 males, 22 females) who underwent BM examinations and 42 patients (30 males, 12 females) who underwent BE examinations were enrolled in the study. The selection was random and included patients who underwent BM or BE examination during a one month period without any optional criteria. Each examination was carried out either by a specialist or by a trainee. In detail, 15 out of 25 BM examinations in hospital A and 10 out of 16 BM examinations in hospital B were carried out by specialists. Similarly, 12 out of 26 BE examinations in hospital A and 11 out of 16 BE examinations in hospital B were carried out by specialists. Barium sulphate for BM and barium sulphiricum for BE were used as contrast agents in both hospitals. In hospital A, the procedures were performed on a General Electric Prestige X-ray system, whereas in hospital B the procedures were performed in a Siemens Gigantos Siregraph X-ray system. Both units were conventional, equipped with an image intensi er and screen/ lm technique, automatic exposure control (AEC) systems and overcouch tubes. Quality assurance measurements (high voltage accuracy and reproducibility, AEC system evaluation, entrance dose measurement and image intensi- erðtv system performance) were performed regularly during the study to ensure proper function of the equipment. 243 Radiation Protection Dosimetry Vol. 109 No. 3 ã Oxford University Press 2004; all rights reserved

2 A Diamentor M4 (PTW Freiburg) was used for DAP measurements. The DAP meter was calibrated free in air, against a Victoreen 660 dosemeter (with a 4 cm 3 chamber) separately for each tube (11). Data recorded for each procedure included equipment type and radiologist name, patient demographic data, uoroscopy time, number of radiographic lms used, anode current (ma), ma s and kv p per projection. Beam direction and exposure parameters are varying continuously in BM and BE examinations. The projections used during the above procedures were posteroanterior (PA), anterioposterior (AP), right anterior oblique (RAO), right posterior oblique (RPO), left anterior oblique (LAO), left posterior oblique (LPO) and left lateral (LLAT). For each procedure, DAP measurements were recorded separately for each of the above projections. Patient-size-corrected DAP data were also calculated. The correction was performed as proposed by Chapple et al. (12), where the appropriate size correction factor is derived using patient equivalent diameter, the reference man equivalent diameter and an experimentally derived factor k. M. G. DELICHAS ET AL. Patient dosimetry included the estimation of effective dose using the ODS-60 software (Rados Technology, Turku, Finland), introduced by Rannikko et al. (10). ODS-60 uses a patient size and sex-adjustable phantom, which is based on the male Alderson Rando phantom, the ICRP Reference Man and a topographic atlas (13). The female phantom is a modi- ed male phantom with different dimensions in the breast, waist and pelvic areas. Each phantom is divided into 36 slices, each 2.5 cm thick. The program includes the outer contours of the phantom slices and organs in each slice. Organ and effective doses are computed on-line using a method similar to the traditional dose planning systems used in radiotherapy. The ODS-60 calculation method based on semi-empirical depth±dose data allows the selection of all the exposure parameters for X-ray examinations. The parameters that the software needs for the calculation of effective dose and organ doses are: (a) patient's sex, height and weight, (b) tube ltration, (c) high voltage, (d) projection of the eld with respect to the patient, (e) focus to skin distance (FSD), (f ) eld size and (g) location of the centre of the X-ray eld in patient's skin. The Table 1. Range and mean DAP, size-corrected DAP, mean uoroscopy time and mean number of radiographic lms for BM and BE examinations in both hospitals. Hospital N DAP a DAP range Size-corrected DAP a Fluoro time a (min) No. of lms a BM A ± B ± BE A ± B ± a Values presented as mean SD. AP LLAT AP 31% LPO 48% PA 5% LAO 1% RPO 6% RAO 16% LPO 27% RPO 11% RAO 7% (a) (b) Figure 1. Mean contribution of each projection in the total DAP. (a) BM and (b) BE. 244

3 exposures were divided into smaller segments (namely upper stomach, lower stomach and duodenum, small and large intestine), in order to get a realistic recording. RESULTS The patients who underwent BM examination had a mean height of m and a mean weight of kg (values presented as mean SD). Their DAP (Gy.cm 2 ) PATIENT DOSES IN BARIUM MEAL AND ENEMA EXAMINATIONS Specialists Trainees mean age was y. The patients who underwent BE examination had a mean height of m and a mean weight of kg. Their mean age was y. Table 1 summarises the results of DAP measurements, size-corrected DAP values, uoroscopy time and number of radiographic lms. The mean contribution of each projection to the total DAP for BM and BE examinations is presented in Figure 1. Figure 2 shows the differences in mean DAP values recorded in procedures performed by specialist physicians against those performed by trainees. The mean effective doses and doses to the higher irradiated organs estimated with the ODS-60 software, are presented in Table 2. For BE examinations, the doses to gonads are quoted only for females since for males the corresponding doses are very small, contributing <0.2% of the effective dose. Figure 3 shows the mean contribution of organ doses to the effective dose for each examination. Figure 4 shows the correlation between DAP and effective dose in both hospitals for BM and BE Barium Meal Barium Enema Figure 2. Mean DAP and radiologist experience. DISCUSSION The measured DAP values are comparable with those reported in recent studies (4±7,14) and higher compared with a recent similar study in Greece (15). For Table 2. Mean organ doses (mgy) and mean effective dose (msv). Organ dose (mgy) Exam. Hospitals Gonads Colon Stomach Liver Effective dose a (msv) BM A B BE A 42.0 b B 30.5 b a Values presented as mean SD. b Females. LIVER 12% RESIDUAL 14% STOMACH 50% RESIDUAL 14% GONADS 29% STOMACH 28% COLON COLON 29% (a) (b) Figure 3. Per cent mean contribution of organ doses to the effective dose: (a) BM and (b) BE (females). 245

4 M. G. DELICHAS ET AL. Figure 4. Correlation between effective dose and DAP for (a) BM and (b) BE. all BM examinations, the mean DAP is Gy cm 2 and for all BE procedures it is Gy cm 2. The maximum to minimum DAP ratio is equal to 8.6 for BM and 11.4 for BE. Higher dose variations have been found in the literature (14). The diagnostic reference levels (DRLs) proposed for BM and BE examinations are 25 and 60 Gy cm 2 respectively (2,16). For BE examinations, a more restrictive value of 40 Gy cm 2 has been proposed (4). In this study, the mean DAP values for BM in hospital B and for BE in hospital A were found to be slightly higher than the corresponding DRLs. In BM examinations, the LPO projection is responsible for 50% of the total DAP whereas in BE, LPO and LLAT projections add up to a 50% contribution to total DAP. There is no statistical difference in the mean DAP values and mean number of radiographic lms used between the two hospitals for both examinations. For BE examinations, the uoroscopy times are signi cantly higher ( p < 0.05) in hospital A compared with the respective times in hospital B. This is due to the fact that in hospital A the majority of BE examinations (14 out of 26) were carried out by a trainee whereas in hospital B, the majority of these examinations (11 out of 16) were carried out by a specialist. For both BM and BE examinations, the mean DAP values for procedures performed by trainees are higher ( p < 0.05) than for those performed by specialists (Figure 2), mainly due to the higher uoroscopy times used. Hoskins and Williams (17) have also reported on the in uence of radiologist grade on uoroscopic patient dose and found that there is a trend for dose decrement after their third year of experience. For all BM examinations, our mean estimated effective dose value is msv and for all BE procedures it is msv. There is no signi cant difference in effective dose between males and females ( p ˆ 0.154) in BM examinations. Nevertheless, the in BE examinations, the effective dose in women is signi cantly higher than in men ( p < 0.05) due to the differences in the genitourinary tract between the two sexes and a different body contour in the abdominal region. This is in accordance with the results of Lampinen and Rannikko (18). DAP to effective dose conversion coef cients estimated for BM (0.34 msv per Gy cm 2 ) and BE (0.41 msv per Gy cm 2 ) examinations are comparable with the value 0.32 msv per Gy cm 2 reported for BM examinations in a national survey in The Netherlands (4). Hart and Wall using Monte Carlo calculation methods estimated the coef cients to be 0.2 msv per Gy cm 2 for BM and 0.28 msv per Gy cm 2 for BE examinations (9). The lower values compared with those derived in this study can be attributed to the use of the Monte Carlo method, which, as pointed out by Rannikko et al. (10), under estimates the effective dose compared with the ODS-60 calculation method, which takes into account the patient's sex and size. Similar differences between the two methods have been found in our survey for Interventional Cardiology procedures (19). Differences in the coef cients can be due to the differences in the tube voltage, FSD and image size since organs may be in different positions with respect to the primary beam. Dose levels are related primarily to the number of radiographic lms used and to screening times (5,6). According to Vehmas et al. (7), the factors controlled by the radiologists ( uoroscopy time and number of radiographic exposures) accounted for 40% of the total variation in the effective dose; 16% of this variation is explained by patient-related factors and equipment-related factors account for the residual 44%. A reduction of the radiation doses measured in this study could be achieved by minimising uoroscopy screening times in both BM and BE examinations. Especially for younger patients, the 246

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