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药物可以通过它们的治疗效果来鉴定,而放射性药物却由于应用的剂量很小,通常它们在体内并不能产生任何可测量的变化。放射性药物通过它们和时间相关的分布进行研究。通过测定放射性药物的类似物是否具有更多(或者更少)有利的动力学或组织吸收来提供下述构效关系的基础。既然放射性药物携带有可被检测的放射性标记,人们便可以定量检测放射活性的存在。假如放射性标记是β-粒子发射体(一种弱电子),那末检测只能通过取出组织,匀化之后计算其放射性。但是,假如放射性标记是γ-射线发射体(电磁能),在机体外部即可被检测,即放射性药物辐射的γ-射线在生命
Drugs can be identified by their therapeutic effect, whereas radiopharmaceuticals usually do not produce any measurable change in the body due to the small doses used. Radiopharmaceuticals are studied by their time-related distribution. The basis for the following structure-activity relationships is provided by determining whether the radiopharmaceutical analog has more (or less) favorable kinetics or tissue uptake. Since radioactive drugs carry radioactive labels that can be detected, one can quantify the presence of radioactivity. If the radioactive label is a beta-particle emitter (a weak electron) then the assay can only calculate its radioactivity by removing the tissue and homogenizing it. However, if the radioactive label is a gamma-ray emitter (electromagnetic energy), it can be detected outside the body, that is, the γ-rays radiated by the radiopharmaceutical are in the life