Technetium Tc-99m Hydroxydiphosphonate

**Semantic type:** Indicator, Reagent, or Diagnostic Aid|Pharmacologic Substance

**Definition:** A radioconjugate containing hydroxydiphosphonate (HDP) labeled with the metastable radioisotope technetium Tc (99mTc), with radioimaging activity. Upon intravenous administration, skeletal uptake of technetium Tc-99m HDP occurs as a function of skeletal blood flow and osteogenic activity. HDP has a specific affinity for hydroxyapatite crystals in bone where abnormal accumulation of increased osteoid mineralization has occurred. Labeling of HDP with 99mTc allows gamma scintigraphic imaging of areas of abnormal osteogenesis associated with malignant bone lesions.

**Synonyms:** - 99mTc HDP - Tc-99m Hydroxydiphosphonate