A routine method for using sodium iodide to stabilize sodium pertechnetate [99Tcm] dispensed for the preparation of 99Tcm-exametazime

Abstract

When preparing 99Tcm-exametazime, it is important to use sodium 99Tcm-pertechnetate that is less than 2 h old. The addition of sodium iodide (NaI) to 99Tcm-pertechnetate is known to extend this time to 6 h. This paper describes a technique for implementing this in routine practice. Sterile kits consisting of 440 micrograms NaI and 1.0 ml sodium chloride injection in a vial with a nitrogen atmosphere were prepared and stored at room temperature, 4 degrees C and -22 degrees C. Titrimetric analysis of iodide showed that under each storage condition, kits were stable for 8 weeks. To determine the effectiveness of the kits, the radiochemical purity (RCP) of 99Tcm-exametazime was measured by high-performance liquid chromatography (HPLC). The validity of this technique was determined by simultaneous analysis with the conventional thin-layer/paper chromatography (TLC/PC) technique on 24 occasions, over a range of RCP (94.5-54.6%). Radiochemical purities measured by HPLC and TLC/PC were 81.2 +/- 10.2 and 81.5 +/- 10.5%, respectively, and did not differ significantly (P greater than 0.30). The correlation between the techniques was high (r = 0.98). 99Tcm-exametazime was prepared using 1 h-old 99Tcm-pertechnetate, 6 h-old 99Tcm-pertechnetate and 6 h-old 99Tcm-pertechnetate dispensed in a NaI kit. At the recommended expiry time for this radiopharmaceutical, i.e. 30 min after preparation, RCPs were found to be 88.4 +/- 2.4, 80.9 +/- 2.0 and 89.3 +/- 3.0%, respectively (n = 5 for each technique).(ABSTRACT TRUNCATED AT 250 WORDS)