99mTcO4

99mTcO4− is the pertechnetate anion containing the metastable nuclear isomer technetium‑99m, a widely used radioisotope in nuclear medicine. The isotope is produced in high‑yield laboratories that irradiate molybdenum‑98 targets using neutron bombardment or proton irradiation, followed by a decay and chemical separation step that yields technetium‑99m. A commercially available mother‑daughter pair, known as the 99Mo/99mTc generator, allows hospitals to elute fresh 99mTcO4− on demand. Technetium‑99m decays by isomeric transition to stable technetium‑99, emitting a 140 keV γ‑ray and a low‑energy internal conversion electron that are optimal for high‑resolution single‑photon emission computed tomography (SPECT). The pertechnetate ion is chemically stable, soluble in aqueous solutions, and biologically acts as a chloride substitute, allowing distribution throughout the bloodstream and uptake in structures such as the thyroid, salivary glands, and bone marrow.

Clinical applications of 99mTcO4− include thyroid imaging and scanning for thyroiditis or cancers, evaluation of gastric motility, bone scans for detecting fractures or bone metastases, cardiac perfusion studies using labeled cardiac agents, and infection or inflammation imaging. Radiopharmaceuticals derived from pertechnetate, such as 99mTc‑labelled colloids, enable imaging of the reticuloendothelial system. The short half‑life of 6.02 hours minimizes patient radiation dose while providing sufficient time for imaging protocols. Handling requires strict adherence to radiation safety protocols, shielding, and waste management, as the isotope decays to stable technetium‑99, which is chemically reactive and must be disposed of according to regulatory guidelines.