DIAGNOSTIC APPLICATIONS OF SIMULTANEOUSLY ACQUIRED DUAL-ISOTOPE SINGLE-PHOTON EMISSION CT SCANS

PURPOSE: To report the development and validation of a technique of du al tracer single-photon emission CT brain imaging using technetium-99m hexamethyl-propyteneamine oxime and iodine-223 iodoamphetamine agents and the application of this technique in patients with a variety of d iagnoses. METHODS: Contamination between the two isotopes' energy wind ows was calculated by opening both energy windows while scanning a gro up of patients using a single isotope. To compare uniformity of I-123 down-scatter, Tc-99m studies were performed both before and after the administration of I-123 in five of 24 dual studies. The 24 patients st udied with the dual-isotope technique were evaluated during acetazolam ide testing, trial balloon occlusion, or embolization of an arterioven ous malformation. RESULTS: In a dual acquisition, average count contam ination of an I-223 study by Tc-99m was less than 1% of the total I-12 3 counts, and contamination of a Tc-99m study by I-123 was approximate ly 12% of the total Tc-99m counts. Tc-99m studies performed both befor e and after the administration of I-123 demonstrated that contaminatin g counts do not adversely affect scan interpretation. Dual-tracer scan s were completed in all 24 patients, 10 of whom showed changes after i ntervention. CONCLUSIONS: Dual-tracer single-photon emission CT brain scans of adequate diagnostic quality are possible using Tc-99m and I-1 23.