[Radioimmunoscintigraphy using SPECT: methodology, problems and clinical experiences].

Radioimmunoscintigraphy (RIS) with 111In-and 131I-labelled monoclonal antibodies (MAbs) against CEA and/or CA 19-9 was performed in 83 patients with various gastrointestinal carcinomas. A total of 276 body regions could be examined. The results of planar scintigraphy and SPECT were compared intraindividually. Using 111In-labelled MAbs the sensitivity of RIS was significantly improved by SPECT (88.9 vs. 52.4% with planar scintigraphy, p less than 0.01). For 131I-labelled MAbs the effect was smaller (83.9 vs. 65.6% with planar scintigraphy, n.s.). This finding can be explained by different kinetics and biodistribution of the used MAb preparations. 111In-labelled MAbs with long whole-body retention and rapid blood clearance reveal ideal qualities for SPECT; on the other hand, the short whole-body retention of 131I-labelled MAbs leads to small count rates and therefore long counting times that make delayed SPECT unsuitable in clinical practice.