Comparison of anteroposterior and posteroanterior projection in lumbar spine radiography.

Background The aim of the study was to compare patient radiation dose and image quality in planar lumbar spine radiography using the PA and AP projection in a large variety of patients of both sexes and different sizes. Patients and methods In the first phase data of image field size, DAP, effective dose and image quality were gathered for AP and PA projection in lumbar spine imaging of anthropomorphic phantom. In the second phase, data of BMI, image field size, diameter of the patient's abdomen, DAP, effective dose and image quality were gathered for 100 patients of both sexes who were referred to lumbar spine radiography. The patients were divided into two groups of 50 patients, one of which was imaged using the AP projection while the other the PA projection. Results The study on the phantom showed no statistically significant difference in image field size, DAP and image quality. However, the calculated effective dose in the PA projection was 25% lower compared to AP projection (p =0.008). Measurements on the patients showed no statistically significant difference between the BMI and the image field size. In the PA projection, the thickness of abdomen was 10% (p < 10-3) lower, DAP 27% lower (p = 0.009) and the effective dose 53% (p < 10-3) lower than in AP projection. There was no statistically significant difference in image quality between the AP and the PA projection. Conclusions The study results support the use of the PA projection as the preferred method of choice in planar lumbar spine radiography.