An improved method for the in vivo labelling of red blood cells with 99mTc in gated cardiac imaging.

Red blood cells of 10 patients were labelled with 99mTc by the in vivo method, 5 of the patients were orally administered with 400 mg potassium perchlorate at the time of stannous pyrophosphate injection and 5 ml blood was withdrawn at 10 min postinjection of pertechnetate to determine the labelling efficiency of RBC's. The RBC and plasma volumes were also determined in all patients by the 51Cr method. Our results indicated higher incorporation of injected radioactivity into RBC's in the perchlorate administered group (83.8% +/- 9.2%) compared to the other (58.5% +/- 22.0%) (P less than 0.01). The thyroid and stomach were visualized in the control group, but not in the perchlorate administered group. In routine application, 50 MUGA studies have been done with perchlorate administration with excellent results. In 60 patients without perchlorate administration previous to the present study the EF could not be determined in 6 patients (10%). Our results indicated that potassium perchlorate may be used routinely for in vivo labelling of RBC's to improve the labelling efficiency and the quality of gated cardiac imaging.