Newer ultrasound probes can be used inside the vagina for a closer look at a fetus, or inside the rectum to detect signs of colon cancer, or to view the prostate gland. Specialized ultrasound probes have also proven useful in diagnosing the cause of female infertility. At first, radiation from radionuclides was used to destroy cancerous tissue inside the body. In 1963, however, a body scanner using radionuclides was developed. Unlike an X-ray machine, which beams radiation at the body from outside, a nuclear scan places the source of radiation inside the patient.
Nuclear scans lack the clear definition of structure visible on an X-ray.
But they can reveal areas of an organ, such as the liver, that are not functioning normally. Some radionuclides that concentrate in diseased areas, such as tumors, show them as hot spots on a scintigram. Others concentrate in healthy, functioning tissues to reveal areas of disease as cold spots. Nuclear scans of bones can enable doctors to detect bone tumors long before they show up on X-rays. They also aid in diagnosing bone injury, infection, and arthritis.