ABSTRACT
Abdominal radiographs are often the first diagnostic imaging tool for patients with acute abdominal pain. In most cases, a supine X-ray is sufficient, but in some cases, an erect abdominal radiograph may be warranted and can provide additional benefits. The aim of this study was to compare erect and supine projections in terms of radiation dose and image quality. Body mass index (BMI), sagittal body thickness, dose area product (DAP)and effective dose (ED) data were collected for 81 patients referred for digital abdominal radiography in both the supine and erect positions. The ED was estimated by inserting the dose area product (DAP) for each projection into the dose modelling computer software PCXMC 2.0. Image quality was assessed by both visual and quantitative methods. The mean ± standard deviation (SD) ED was 0.4 ± 0.3 and 0.2 ± 0.1 mSv for erect and supine projections, respectively (p < 0.001). The estimated ED in the erect position was 102% higher compared to the supine position. The mean ± SD visual image quality was reduced (27%) when using an erect position 1.9 ± 0.5 when compared with supine 2.6 ± 0.7. The calculated signal to noise ratio (SNR) was higher in erect position by 14%. Contrast to noise ratio (CNR) was reduced by 16% when using an erect position. Study findings support the continued use of the supine position as the preferred method due to significant reductions in radiation dose when compared to erect imaging. A single projection is likely to be sufficient but in certain situations, for example in case of absence of a computed tomography (CT) scanner or ultrasound, then an additional erect abdominal radiograph may be warranted. The erect abdomen radiograph increases the radiation dose and decreases the image quality. Further research is required to define more holistically evaluation optimisation strategies to reduce the patient dose, such as using an increase source-to-image distance or the development of patient-specific exposure parameters for evaluating different clinical indications and patient sizes.
