Interpreting the meaning of test results for serious conditions is a stressful experience for patients. Bone scan imagining is one diagnostic tool used by doctors, and the procedure tests for a variety of conditions. Positive test results can have a variety of meanings.
Bone scan imagining is used to diagnose bone tumours, bone cancer and osteomyelitis (bone infection). It also is used to determine if cancers, such as breast, kidney, lung, prostate and thyroid, have spread to the bones. Bone scan imaging can evaluate metabolic disorders, diagnose or determine the cause of bone pain that has no other identified cause and diagnose fractures that cannot be seen on a regular X-ray--the most common of these are hip fractures, spine fractures and stress fractures in the feet or legs.
How it Works
According to MedlinePlus, in a bone scan, radioactive material called a "radiotracer" is injected into a vein and travels through the bloodstream to the bones and organs. The radiation given off by the substance as it wears off is detected by a camera that slowly scans the body and takes pictures of areas where the radiotracer has collected. The amount of radiation injected into the vein is very small and poses no greater risks than a conventional X-ray.
Types of Results
In a normal bone scan, the images show that the radioactive material has been evenly distributed throughout the body. Doctors use the term "hot spots" for areas of increased accumulation of the radioactive material and "cold spots" for areas of decreased accumulation. Hot or cold spots appear in abnormal test results. The areas of increased or decreased accumulation indicate abnormal bone metabolism, according to the Mayo Clinic. Abnormal bone metabolism sometimes is referred to as abnormal bone growth.
What it Means
According to WebMD, dark or cold spots, which lack the presence of tracer, may indicate bone infarction (lack of blood supply to the bone) or certain types of cancer. Bright or hot spots on the scan, where increased amounts of tracer have accumulated in certain areas of the bone, can indicate arthritis, bone cancer, a healing fracture, infection (osteomyelitis) or a disease of abnormal bone metabolism such as Paget's disease.
It is important to realise that even if a bone scan imaging test is positive for a condition, bone scans are used to diagnose conditions together with other tests and clinical information. According to the Mayo Clinic, bone scans are sensitive tests for abnormal metabolism but are not as good at identifying the cause of the abnormality. Bone scan results are interpreted along with symptoms, X-ray results and medical history. In addition, other tests such as computed tomography (CT), magnetic resonance imagining (MRI), blood tests or a biopsy may be needed to help establish a diagnosis.