What can a hip/pelvic ct scan show that a mri cannot? (dr ordered bilateral hip/pelvic ct scan 2x45min in machine-worried about radiation)

The CT: Gives fine detail about the bones of the pelvis and hips. If your doctor is worried about arthritis or femoral-acetabular impingement this may give more information. Best to ask your doctor and relay your concerns.

Bones vs Soft Tissue: Ct shows the surface of the bones and any calcifications very well. Mri is better for soft tissues such as muscles and tendons. The actual scanning time for a ct of the hip(s) is just a few seconds. All the rest of the time is spent making sure the test is optimized for the best image quality.