Metabolic and improved organ scan studies. II. Nitrogen-13 labeled compounds used as in-vivo probes for enzyme therapy and as tumor localizing and organ imaging agents

A number of 13N-labeled compounds have been enzymatically synthesized and are being evaluated as tumor and/or organ localizing agents. 13N-Ammonia, produced after cyclotron generation of 13N-nitrate and subsequent reduction was used to enzymatically aminate the appropriate substrate to yield 13N-L-glutamic acid, L-glutamine, L-asparagine, L-valine, L-leucine and L-alanine. The use of 13N-asparagine as a myocardial scanning agent and as a tumor localizing agent in asparaginase-sensitive tumors is discussed. Two imaging devices were used to study the effectiveness of the compounds as localizing agents. For static whole body distribution studies, a dual-detector high energy gamma ray (HEG) rectilinear scanner, equipped with constant response collimators was employed. The uniformity of response of this system permits quantitative determination of the amount of 13N activity present in the organ or tumor of interest. The total organ kinetic imaging monitor (TOKIM) gamma camera system was used for dynamic studies covering smaller areas of the subject's body