• Clinical science

Bone scan

Abstract

A bone scan (skeletal scintigraphy) is an imaging modality in which an intravenously administered radioactive tracer with an affinity for bone (e.g., Tc99m-methylene biphosphonate) is used to visualize areas of increased metabolic activity within bone with the aid of a gamma camera. Bone scans are used to evaluate bone injuries, musculoskeletal pain, joint conditions, primary bone neoplasms, and malignancies with potential for bone metastases.

Indications

A bone scan is used for the detection, evaluation, and/or follow-up of the following conditions:

References:[1]

Contraindications

  • Absolute contraindication: pregnancy
  • Relative contraindications
    • Breastfeeding women
    • Pathology with a predominantly osteoclastic process (e.g., multiple myeloma)
    • Trauma or surgery in the region of interest within the past 6–12 months .

References:[2]

We list the most important contraindications. The selection is not exhaustive.

Procedure/application

  1. Intravenous administration of a radionucleotide tracer with an affinity for bone (e.g., Technetium-99m diphosphonate, Technetium-99m oxidronate)
  2. Uptake of tracer in areas with high bony metabolic activity (“hot spots”)
    • Uptake of the radiotracer by a particular region of the bone is dependent on:
      • Regional blood flow
      • Osteoblastic activity
      • Amount of osteoid
  3. Detection of these “hot spots” with a gamma camera
    • Angiographic (perfusion) and early blood pool phase imaging
      • Performed immediately (angiographic phase) and 3–5 minutes (early blood pool phase) after injection of the radiotracer
      • Ideal for evaluating inflammatory or infective conditions, bone tumors with increased vascularity (e.g., osteoid osteoma), and conditions with decreased blood flow (e.g., avascular necrosis)
    • Delayed bone phase imaging
      • Performed 2–3 hours after injection of the radiotracer
      • Allows optimal concentration of the tracer by osteoblasts
  4. Renal elimination of the radiopharmaceutical agent with increased uptake in the urinary tract

References:[2][3]

Interpretation/findings

  • Very high sensitivity for the detection of areas of bone with increased metabolism
  • Low specificity