Effective dose to patients due to fluoroscopic screening in barium meal examinations: comparison between free and...

Four complete barium meal (BM) fluoroscopic examinations were digitised as sequences of 160 x 128 pixel, 8 bit images, at a rate of about 100 per min using a computer frame-grabber system and were recorded on disk for processing. The images were latter replayed and, using a suitable program, were superimposed in a new picture so that anatomic details coincided. At the same time, two more pictures were created by summing the radiation fields corresponding to the images grabbed, one with open diaphragms at 26 x 22 cm field size and one with simulated closed diaphragms at 7 x 11 cm. The average effective dose rate delivered to the patient during fluoroscopic screening was calculated for a hermaphrodite mathematical phantom and was found to be 0.21 mSv/min and 0.005 mSv/min, respectively, if either technique had been used exclusively. The average effective dose delivered to the patients with the actual techniques used in the 4 BM examinations recorded was 0.394 mSv. Data from these examinations was extrapolated to a sample group of 122 BM examinations, performed during a 9-week period, for which total exposure duration was known. The average effective dose calculated for fluoroscopy was shown to be negligible, particularly if only the 'closed' diaphragm technique was used, when compared to the estimated average effective dose of about 8.6 mSv delivered by the radiographs made during each examination.