What is the procedure and indications for a bone scan, including technetium-99m (Tc-99m) methylene diphosphonate (MDP)?

From the Guidelines

A bone scan is a nuclear medicine imaging procedure used to detect bone abnormalities by injecting a radioactive tracer, typically technetium-99m (Tc-99m) methylene diphosphonate (MDP), which accumulates in areas of increased bone metabolism, and is indicated for detecting metastatic bone disease, primary bone tumors, osteomyelitis, fractures, avascular necrosis, Paget's disease, and evaluating unexplained bone pain 1. The procedure involves intravenous injection of Tc-99m MDP, followed by a waiting period of 2-4 hours to allow the tracer to accumulate in bone tissue. During this waiting period, patients should drink plenty of fluids to promote excretion of unbound tracer. The imaging phase involves whole-body scanning with a gamma camera, with additional spot views as needed. Some key points to consider when using bone scans include:

• The scan works because Tc-99m MDP binds to hydroxyapatite crystals in bone, with increased uptake in areas of high osteoblastic activity or blood flow 1.
• This makes it particularly sensitive for detecting lesions with increased bone turnover, though it lacks specificity as both benign and malignant processes can show increased uptake 1.
• PET imaging has significant advantages over bone scintigraphy for evaluation of skeletal metastatic disease, including superior diagnostic accuracy, higher spatial resolution, and shorter imaging times 1.
• The diagnostic pathway for multiple myeloma is somewhat different, as myeloma bone disease is often missed on radionuclide bone scans, and low-dose whole-body CT or FDG-PET-CT imaging are preferred imaging modalities in this case 1. The procedure is minimally invasive with rare complications, primarily limited to minor injection site reactions. Patients should inform their provider about pregnancy, breastfeeding, or recent nuclear medicine studies. Some of the indications for a bone scan include:
• Detecting metastatic bone disease
• Primary bone tumors
• Osteomyelitis
• Fractures (especially stress or occult fractures)
• Avascular necrosis
• Paget's disease
• Evaluating unexplained bone pain It is essential to consider the patient's overall clinical context when interpreting the results of a bone scan, as the scan may not be able to distinguish between benign and malignant processes 1.

From the FDA Drug Label

INDICATIONS AND USAGE Technetium Tc 99m Pyrophosphate Injection is a skeletal imaging agent used to demonstrate areas of altered osteogenesis DOSAGE AND ADMINISTRATION Bone and Cardiac Imaging The recommended adult doses of Technetium Tc 99m Pyrophosphate Injection are: Indication Doses as Technetium Tc 99 Fraction of Vial Contents Required Skeletal Imaging 185 to 555 megabecquerels (5 to 15 mCi) 0.07 to 0.91

The procedure for a bone scan using technetium-99m (Tc-99m) methylene diphosphonate (MDP) involves injecting the radiopharmaceutical intravenously, followed by imaging with a gamma scintillation camera.

• The recommended adult dose for skeletal imaging is 185 to 555 megabecquerels (5 to 15 mCi)
• Imaging should be done 1 to 6 hours after administration. The indications for a bone scan include demonstrating areas of altered osteogenesis. Key points:
• Technetium Tc 99m Pyrophosphate Injection is used for skeletal and cardiac imaging
• The dose for skeletal imaging is 185 to 555 megabecquerels (5 to 15 mCi)
• Imaging should be done 1 to 6 hours after administration 2 2

From the Research

Procedure for a Bone Scan

• A bone scan is a diagnostic test that uses technetium-99m (Tc-99m) methylene diphosphonate (MDP) to detect bone abnormalities 3, 4.
• The procedure involves injecting a small amount of radioactive material into the bloodstream, which accumulates in the bones and is then detected by a gamma camera 3, 4.
• The scan can be performed in various phases, including a three-phase bone scan, which includes an immediate postinjection radionuclide angiogram, a blood-pool image, and delayed static images, or a four-phase bone scan, which adds a 24-hour static image 5.

Indications for a Bone Scan

• The most important and most frequent role of bone scanning is evaluating the skeletal areas in patients who have a primary cancer, especially a malignant condition that has a tendency to spread to bone areas 3.
• Bone scans can also be used to diagnose and localize bone infection, such as osteomyelitis 6, 5, 7.
• Insufficiency fractures (IFs) can be challenging to diagnose, and a bone scan can be useful in evaluating IFs and determining the etiology of IF 4.
• Stress fractures and trauma suspected in battered babies can be diagnosed by scanning before there is radiological evidence 3.

Advantages and Limitations of a Bone Scan

• The bone scan is superior to bone radiographs in diagnosing bone abnormalities, and can detect abnormalities earlier than radiographs 3.
• The procedure is free from acute or long-term side effects, and sedation is seldom necessary, except in cases of very young patients 3.
• However, the test is not specific, and therefore, it is difficult to overemphasize the importance of clinical, radiographic, biochemical, and scanning correlation in each patient 3.
• The addition of a 24-hour image, creating a four-phase bone scan, can improve the accuracy of diagnosing osteomyelitis 5.
• SPECT/CT can improve the diagnostic performance of three-phase bone scan for osteomyelitis by avoiding false positive or equivocal results 7.

Common Findings on a Bone Scan

• The majority of bone metastases appear as hot spots on the scan and are easily recognized 3.
• Bone scintigraphy shows positive uptake in 95 percent of cases with acute osteomyelitis 3.
• Insufficiency fractures can be identified on a bone scan, with the most common sites being the dorsolumbar vertebrae, ribs, and lower limb bones 4.