Kit-labeled technetium-99m red blood cells (Tc-99m-RBC's) for clinical cardiac chamber imaging

Abstract

We have studied 223 consecutive patients by R-wave synchronized cardiac imaging using Tc-99m-RBC's labeled by the Brookhaven kit method. Preparation of the Tc-99m-RBC's is simple and can be accomplished in less than 20 min per patient. The average percent RBC labeling was 96.89%. Only 5 of 223 patients (2.2%) had yields less than 95%. Fifty patients were randomly selected from among the 223 patients for more detailed analysis. Image quality was uniformly excellent with good visualization of the cardiac chambers. The spleen was prominently seen. The average left ventricular chamber to background ratio was 2.69±0.56 (X ± S.D.). Among 12 patients imaged with Tc-99m-RBC's (Brookhaven) in whom blood activity was followed, the blood disappearance could be resolved into two components: a major component (95% of total blood activity) with a t-1/2 of 29 h; and a minor component (5% of total activity) with a t-1/2 of 20 min. Splenic uptake obtained with the aid of a computer system in two of these patients showed progressive uptake in the spleen over the first 30 min after injection, with a plateau thereafter.

Purposeful degradation of the Brookhaven kit labeled Tc-99m-RBC's study was accomplished in five patients by adding free TcO ⁻₄ . Even small increments of free Tc-99m-pertechnetate resulted in visual deterioration of the cardiac image. Over the course of this study, the percent of total blood activity on the red blood cells dropped from 99% to 78%, and the average end-diastolic left ventricular (LV) to back-ground (BKG) count ratio dropped from 3.5 to 2.4. Ejection fraction measured from the BKG corrected LV curve decreased very slightly.