Fig. 1

A With larger PI values, a greater fluoroscope cephalad tilt and a more horizontal projector placement were required. However, it was difficult to steer the fluoroscope to an appropriate angle of trajectory to get an optimal and clear pelvic outlet image due to hindrance from the radiolucent table or the patient’s thigh. When setting the pelvic inlet projection, the beamer of the single-arm fluoroscopic intensifier had to be aligned more perpendicularly with respect to the patient. The radiation could pass through excessive abdominal and buttock fat and bowel flatus, which could further interfere with and degrade the resolution of the images. B With smaller PI values, it is easier to position the fluoroscope to project the appropriate cephalad and caudal tilt angles. Solid ine caudad tilt of the fluoroscope, dashed line cephalad tilt of the fluoroscope, dotted line ideal cephalad tilt of the fluoroscope, dashed-dotted line PI angle, PI pelvic incidence