Progress using Tc-99m radiopharmaceuticals for measuring high capacity sites and low density sites

•Technetium-99m (Tc-99m) has long been a mainstay in clinical nuclear medicine.•Tc-99m radioligands that target low-density, specific proteins have been developed.•The strengths remain the cost of Tc-99m, high-yield kits, and widespread SPECT.

Technetium-99m (Tc-99m) has long been a mainstay in clinical nuclear medicine, primarily monitoring biological processes in the heart, kidney, liver, and brain. More recently, Tc-99m chelates have been used as the reporter in targeted nuclear medicine probes that monitor changes in specific protein expression products. The strengths remain the inexpensive source of Tc-99m from the Mo-99/Tc-99m generator, its rich chemistry, high-yield kit formulation, and its widespread availability. Hardware and software advances, such as OSEM reconstructions with scatter and attenuation corrections, have led to quantitation of the injected radioactivity in terms of kBq/cm.