What angle does the tube need to be tilted for the PA projection of the sacrum?

For the PA (posteroanterior) projection of the sacrum, the x-ray tube needs to be tilted 15 degrees caudad. This angling is necessary to ensure that the radiation beam aligns appropriately with the anatomy of the sacrum. When viewing the sacrum, the caudal angle helps to decrease the curvature and reduce distortion in the image, allowing for a clearer presentation of the sacral anatomy on the radiograph. The position and tilt also help to minimize superimposition over surrounding structures and optimize visualization. Hence, a 15-degree caudad angling is standard practice for obtaining an accurate PA projection of the sacrum.