Quantitative assessment of myocardial perfusion abnormality on SPECT myocardial perfusion imaging is more reproducible than expert visual analysis

Abstract

Background: Current guidelines of Food and Drug Administration for the evaluation of SPECT myocardial perfusion imaging (MPI) in clinical trials recommend independent visual interpretation by multiple experts. Few studies have addressed whether quantitative SPECT MPI assessment would be more reproducible for this application.

Methods and results: We studied 31 patients (age 68 +/- 13, 25 male) with abnormal stress MPI who underwent repeat exercise (n = 11) or adenosine (n = 20) MPI within 9-22 months (mean 14.9 +/- 3.8 months) and had no interval revascularization or myocardial infarction and no change in symptoms, stress type, rest or stress ECG, or clinical response to stress on the second study. Visual interpretation per FDA Guidance used 17-segment, 5-point scoring by two independent expert readers with overread of discordance by a third expert, and percent myocardium abnormal was derived from normalized summed scores. The quantitative magnitude of perfusion abnormality was assessed by the total perfusion deficit (TPD), expressing stress, rest, and ischemic perfusion abnormality. High linear correlations were observed between visual and quantitative size of stress, rest, and ischemic defects (R = 0.94, 0.92, 0.84). Correlations of two tests were higher by quantitative than by visual methods for stress (R = 0.97 vs R = 0.91, P = 0.03) and rest defects (R = 0.94 vs R = 0.82, P = 0.03), respectively, and statistically similar for ischemic defects (R = 0.84 vs R = 0.70, P = ns).

Conclusions: In stable patients having serial SPECT MPI, quantification is more reproducible than visual for magnitude of perfusion abnormality, suggesting its superiority for use in randomized clinical trials and monitoring the effects of therapy in an individual patient.

Figure 1

A figure illustrating the concept of total perfusion deficit (TPD). A circumferential profile for one short axis slice is shown with corresponding normal limits. The areas below the normal limit curve but above the circumferential profile curve for a given slice define perfusion deficit in a given slice. These areas are computed for all circumferential profiles in the myocardium and summed forming TPD.

Figure 2

Correlation of stress perfusion defects by visual (left) and quantitative (right) analyses between study 1 and study 2. P = 0.03 for the comparison between visual and quantification. % myo = percent of myocardium abnormal; TPD = total perfusion deficit.

Figure 3

Correlation of rest perfusion defects by visual (left) and quantitative (right) analyses between study 1 and study 2. P = 0.03 for the comparison between visual and quantification. Abbreviations as in Figure 2.

Figure 4

Correlation of ischemic perfusion defects by visual (left) and quantitative (right) analyses between study 1 and study 2. P > 0.05 for the comparison between visual and quantification. Abbreviations as in Figure 2.

Figure 5

Correlation (left) and differences (right) of stress perfusion defects by visual and quantitative analyses on study 1. Quant = quantitative; other abbreviations as in Figure 2.

Figure 6

Correlation (left) and differences (right) of rest perfusion defects by visual and quantitative analyses on study 1. Abbreviations as in Figure 5.

Figure 7

Correlation (left) and differences (right) of ischemic perfusion defects by visual and quantitative analyses on study 1. Abbreviations as in Figure 5.