Flow-Dependent Uptake of ¹²³I-CMICE-013, a Novel SPECT Perfusion Agent, Compared with Standard Tracers.

Abstract

Rotenone derivatives have shown promise in myocardial perfusion imaging (MPI). CMICE-013 is a novel (123)I-labeled rotenone derivative developed for SPECT MPI. The objective of this study was to assess the image quality of CMICE-013 and compare its uptake with tetrofosmin, sestamibi, and (201)Tl in vivo in a porcine model of stress-induced myocardial ischemia. Microspheres were injected simultaneously with the radiotracer injections at rest and stress to measure blood flow. Mimicking a 1-d tetrofosmin protocol, stress imaging used 3 times as much activity and occurred 1 h after the rest injection. SPECT images were obtained at both rest and stress. After imaging, the heart was sectioned into 44-50 pieces. In each heart sample, the tracer uptake was measured in a γ counter. The images were aligned, and the decay-corrected ratio of the signals at rest and stress was used to separate the well-counter signal into rest and stress components. The uptake at rest and stress was compared with microsphere flow measurements. The CMICE-013 images showed good contrast between the heart and surrounding organs, with heart-to-liver and heart-to-lung uptake ratios similar to those of the standard tracers. Uptake of CMICE-013 was 1.5% of the injected dose at rest and increased more rapidly with increased blood flow than did the standard SPECT tracers. The percentage injected dose of CMICE-013 taken up by the heart was greater (P < 0.05) than (201)Tl, tetrofosmin, or sestamibi at flows greater than 1.5 mL/min/g. CMICE-013 is a promising new SPECT MPI agent.