Abnormal Bone Scan

Bone scans are ordered by physicians for a variety of reasons including pain of undetermined origin. There are many conditions that will result in an abnormal finding on a bone scan. Scan results may confirm or rule out clinical suspicions, but abnormal bone scans alone rarely point to a specific diagnosis.

Description

A bone scan is performed by injecting a radioactively-tagged compound intravenously. The compound in this case selectively concentrates in areas of increased bone formation. An imaging device, sensitive to the radioactive compound, then scans the body. The resulting image looks like an indistinct grey reproduction of the skeleton.

Abnormal Findings

In an abnormal or "positive" bone scan, areas where the radioactive compound is concentrated will appear dark. These dark areas are referred to as "hot spots." It is normal for the scan to show some increased concentration near the ends of the long bones, especially in young people who are still growing. The breast bone, spine, pelvic joints, and thyroid are also areas of normally increased concentration. Hot spots in other areas are especially significant. Guidelines produced by the European Association of Nuclear Medicine stress that symmetrical and homogeneous uptake of the tracer compound in bone structures are the important indicators of a normal scan.

Specificity

Bone scans are very sensitive tests. That means that they are good for identifying subtle abnormalities in bone. The text, "Essentials of Skeletal Radiology" states that bone scans are ten times more sensitive than conventional X-rays in identifying certain abnormalities of bone. Bone scans are not, however, specific tests. While they readily identify areas of bone destruction and repair, they do not reveal much information as to the underlying cause of the destruction and repair.

Conditions

Bone scans are useful in detecting stress fractures or other subtle fractures that may not show up on traditional X-rays. They can also help to determine if a fracture has fully healed. In addition to fractures, Mayoclinic.com lists arthritis, Paget's Disease of bone, some tumors originating in bone, cancer that has spread to bone, bone infections, fibrous dysplasia and bone destruction from impaired blood supply as other causes of abnormal scan results.

Perspective

Bone scanning is an imaging tool used to detect a number of abnormalities of the skeletal system. Because a variety of conditions can result in abnormal findings, bone scan results must be considered in the context of other clinical findings or test results in order to reach a definite diagnosis.