Validation for Dual Isotope Reversibility Maps using 4D-MSPECT.

Forty-six patients (32 male, 14 female, 58 ± 10 years) were randomly selected from the clinic population to validate reversibility polarmaps using 4D-MSPECT. Each of the patients underwent a dual-isotope protocol involving a resting thallium (3mCi) followed by stress Tc-99m-Sestamibi (30mCi) study. The reconstructed filtered backprojection images were processed with 4D-MSPECT and presented to two physicians who visually scored the images using a 19 segment overlay. Perfusion scores were 0 = normal, 1 = equivocal, 2 = abnormal, 3 = severely abnormal. In regions where the stress images were scored = 2, reversibility scores (0 = no change or fixed, 1 = partially reversibility, 2 = complete reversibility) representing the positive change between the rest and stress studies were noted. Discordant regions between the two reviewers were reread and given a consensus scoring. The 19 segment overlay was then reduced to the 3 region vascular (LAD, LCx, RCA) overlay. Using this overlay, there were 54 defects identified visually, 38 were partially or completely reversible and 16 were fixed.

Reversibility polar maps were then computed using 4D-MSPECT and compared to a normal database where the defect cutoff was globally set to 10%. Reversibility was visually displayed in white cross-hatch in the area of the stress perfusion defects which was displayed as black. Regional statistics for defect and reversibility extent were also displayed. 4D-MSPECT correctly identified 32 of 38 (84%) partially or completely reversible defects and 14 of 16 (88%) fixed defects. These results compare quite well to the published data(1) from the FDA approved program CEqual^TM which showed a 73% agreement for reversible defects and 80% for fixed defects.

1. Garcia EV et al. Quantification of the reversibility of stress-induced thallium-201 myocardial perfusion defects: A multi-center trial using bull's-eye polar maps and standard normal limits. J Nucl Med 1990; 31: 1761-1765.

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