Making a Back Pain Diagnosis: Imaging Tests - Bone Scan and Discogram

The diagnostic tools available to doctors to diagnose back pain include X-Rays, CT Scan, MRI. Bone Scan, discogram, Dual Energy X-Ray Absorptiometry, nerve tests, and blood tests. Here we will take a look at the bone scan and discogram.

Bone Scan. Like the CT Scan with Myelogram, the bone scan involves the injection of radioactive dye and the medical imaging of the structures of the musculoskeletal system. In a bone scan, a small amount of radioactive dye is injected into the body, through a vein in the arm. After the injection, the dye circulated around the body, over a couple of hours, through the body. The dye absorbed into the structures of the back, including the bones of the spine.

After about two hours after the injection, a special camera collects the images and produces images that can be read by a radiologist or physician that specializes in back pain medicine. The scan taken an image of the whole body, highlighting areas where there is increased bone-forming cell activity and blood flow. Areas of increased blood flow or osteoblastic activity (bone-forming activity) may indicate bone fractures, infection, or tumors.

A bone scan is a medical imaging procedure that involves the injection of a nuclear radioactive dye that circulates throughout the body and indicates bone damage or bone tumors, if present, upon scanning. A bone scan, may be used to detect these types of diseases or damage to the musculoskeletal system:
  • Pathologic changes to the bone as a result of infections.
  • Micro-fractures that X-Rays miss detecting.
  • The source(s) of bone inflammation and bone pain due to infection or fracture.
  • Primary cancers on the bone.
  • Cancers that have spread (metastasized) to the bone

Bone scans are one of the types of diagnostic tests/procedures of nuclear medicine. Bone scans are used to detect bone abnormalities, such as inflammation, changes in metabolism, or the development and growth of cancers in or one the bone. Other nuclear medicine tests that observe the metabolism of bones include the PET Scan (Positron emission tomography). The bone scan, or bone scintigraphy, is not the test of choice for observing bone density, or bone density loss (DXA is more appropriate to measure these changes to the skeletal system).

Procedure. For this test, the radiocontrast is injected into one of the veins in the arm through an IV line. One common type of nuclear medicine dye used is 600 MBq of technetium-99-MDP. After 2-3 hours of injection, the patient then lies on a specialized medical table fitted with an arm and camera above the patient that takes the images. The body is scanned with a gamma camera. The radioactive material is absorbed into healthy, non-injured bone at a certain rate, and bone sections that have been traumatized by infection, fracture, or tumors absorb the radioactive material at a much higher rate.

A bone scan image produces a photograph of the patient's entire skeletal system. The entire scan is a black and white photo, with healthy bone visualized in lighter grey and grainy, and injured bone or bone with metastatic tumors presenting as solid dark grey or solid black. Infections, fractures, and tumors show up as areas of increased uptake.