Introduction: X-ray of the thoracic organs is the most common diagnostic radiological
test. Purpose: The purpose of the BA thesis was to compare lung X - ray in anterior-posterior (AP) and posterior-anterior (PA) projection, in order to determine whether the literature-based differences between the projections are also detected and visible in radiographs of the thoracic organs in the above- mentioned projections. In addition, the aim was to ascertain whether a difference in DAP, the effective dose and absorbed dose on selected radiosensitive organs in AP and PA projections is observed.
Methods of work: The study was carried out in two parts. In the first part, we compared the patients’ chest radiographs, obtained from a freely accessible electronic base of medical records, to own acquired images. We compared lung radiographs of the same patient in AP and PA projections according to the standards for the evaluation of radiographs. In the second part, we performed DAP measurements, and calculated effective doses and absorbed doses on selected radiosensitive organs in the area of the thoracic organs of the phantom. We did 20 X-ray images, 10 of it in horizontal position at the distance of 115cm between the source spot on the tube and the image receptor (SID) - 5 in AP and 5 in PA projection - and 10 images in the upright position at SID 180cm, also 5 in AP and 5 in PA projection.
Results: The results of the comparison of lung radiographs in AP and PA projections demonstrated differences in structure view. The heart is closer to its real size in the PA projection; shoulder blades are projected more laterally and outside the lungs, the collarbones are not projected too high in the apex of lungs. In the AP projection, the heart is bigger and extended, shoulder blades are projected more medially, collarbones are projected higher and more horizontally, the chest looks wider and shallower. Artefacts and displacement of the patient to the side are more frequent in AP projection rather than in the PA due to the patient's condition, which often disables the removal of various medical devices. The results of the phantom measurements showed lower DAP values in PA projection compared to those in AP projection (values at SID 115 cm lower by 7.6 %, at SID 180 cm by 4.8 %). The effective dose is lower in PA projection by 82.9 % at SID 115 cm and by 39, 9% at SID 180 cm. The absorbed dose for radiosensitive organs such as breasts, gall bladder, heart, liver, pancreas, stomach, thymus and thyroid is lower in PA projection. The dose received by the lungs, the oesophagus and the spleen is lower in AP projection. Discussion and conclusion: The PA projection is the preferred method of choice for lung X-ray imaging, since the quality of the radiograph and a dose of radiation are more optimal than in the AP projection.
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