Characteristics of Specific Radiopharmaceuticals

Abstract

In this chapter, the practical aspects of preparation, labeling yield, stability, storage conditions, and other characteristics of radiopharmaceuticals most commonly used in nuclear medicine are discussed below. 7.1 99m Tc-Labeled Radiopharmaceuticals The basic principle of 99m Tc-labeling involves reduction of 99m Tc 7+ to an oxidation state that binds to a chelating molecule of interest. In most cases, kits for 99m Tc-radiopharmaceuticals are commercially available for routine clinical use. These kits contain the chelating agent of interest and the reducing agent in appropriate quantities. In some kits, suitable stabilizers are added. Limits of volume and activity of 99m Tc that can be added to specific kit vials and expiration time are given in the package inserts provided by the manufacturer. For most 99m Tc-radiopharmaceuti-cals, the expiration time is 6 h, equal to the physical half-life of 99m Tc (t 1/2 = 6 h). Also included in the package inserts are storage temperatures for the kits before and after the formulation with 99m Tc. The following is a description of the characteristics of the routinely used 99m Tc-radiopharmaceuticals. 7.1.1 99m Tc-Sodium Pertechnetate 99m Tc-NaTcO 4 (t 1/2 = 6 h) is eluted from the 99 Mo-99m Tc generator in saline solution. These generators are supplied by Mallinckrodt Pharmaceuticals and Lantheus Medical Imaging. The 99m TcO 4-solution obtained from the generator is tested for 99 Mo and Al breakthrough, and aliquots are used to prepare different kits, as described below. The shelf-life of 99m TcO 4-is 12 h after elution and can be stored at room temperature. The oxidation state of technetium in 99m TcO 4-is 7+. 99m TcO 4-is primarily used for preparation of 99m Tc-labeled radiopharmaceuticals, but is used as such for thyroid imaging and Meckel's diverticulum detection. 7