A guide to the applications of Nuclear Medicine in bone disease for improved detection and treatment of bone disorders, such as metastases or orthopedic conditions, via imaging procedures.
by Partha Ghosh, Siemens AG
Main application in bone diseases
The major application of Nuclear Medicine in diseases related to the bone is to detect spread of cancer to the bone or to detect bone changes in some orthopedic conditions like bone infections, decreased blood supply to the bone etc.
How does it work?
The procedure involves an injection of a radioactive isotope (99mTc MDP) to the blood which is accumulated in the skeleton in proportion to the degree of bone metabolism.
Thus regions of bone with cancer have high metabolism due to high bone turnover because of the malignant process and consequently show high uptake of the radioactive isotope within the cancerous bone which is then imaged with a gamma camera which images the distribution of radioactive isotope in the whole body and can easily find out the regions of abnormal metabolism which represent metastases from cancer.
Although most of these studies are performed using SPECT gamma camera, in recent times PET/CT scanners have also been used for bone metastases detection using different PET specific radioactive isotopes.
What could be imaged
Bone metastases is common in several cancers like prostate and breast cancer and nuclear medicine procedures are routinely used to evaluate if patients during follow up after treatment . Presence of bone metastases as visualized by bone scanning on SPECT scanners represent advanced disease stage or disease progression which needs to be treated aggressively, mostly with chemotherapy or radiation. Thus finding early bone metastases is important for appropriate management and repeated follow up bone scans help in cancer follow up.
In several orthopedic conditions like bone infections or osteomyelitis, decreased blood supply to the bone often secondary to fracture or injury (avascular necrosis), stress fractures etc, the metabolism of bone is altered very early and imaging using nuclear medicine techniques is often the earliest method of detection and effective treatment. In such indications bone SPECT scanning is often used.
Introduction of SPECT/CT systems which combine a gamma camera with CT have improved on detection accuracy for bone disease by combining the metabolic information from a gamma camera with the bone structure image from CT.