A CT scan is a scan using an x-ray machine that takes a cross-section shot of the body using very little radiation. The purpose is to measure the bone length of the legs to determine if there is one leg shorter than the other.
Ultrasound imaging uses sound waves to produce pictures of the soft tissues inside of the body. It is used to help diagnose the causes of pain, swelling, soft tissue, ligament and tendon tears.
X-rays are effective for zeroing in on the bones and identifying fractures, joint ailments, osteoarthritis and osteoporosis