Exercise PET: More insight or more complex?

Abstract

In this issue of the journal, Aggarwal et al 1 report on 265 patients undergoing diagnostic treadmill stress myocardial perfusion imaging by PET using N-13 ammonia and rotating rod attenuation correction. 194 patients were obese (74%) with average treadmill capacity significantly less than non-obese patients as reflected by significantly lower exercise duration, functional aerobic capacity, METs achieved, and pressurerate product. Coronary angiograms were done in 43 (16% of 265) patients of whom 36 (14% of 265) had significant CAD by visual assessment. Diagnostic sensitivity was 86% and specificity 74%, with no difference between obese and non-obese patients. The authors conclude that treadmill stress perfusion PET is ''feasible and useful clinically with higher rate of good image quality, greater spatial, temporal, and contrast resolution, robust attenuation correction, high-count statistics, and less hepatobiliary tracer uptake of PET compared to SPECT.''The authors deserve credit for a large series of patients using a treadmill exercise PET perfusion imaging protocol. Due to the short half-life of cyclotron-produced N-13 ammonia, simply timing and coordinating the exercise stress with producing N-13 ammonia for injection at peak exercise and moving patients into the scanner gantry for adequate count images are a singular achievement. The effort to get good relative perfusion images is worthwhile given the attenuation artifacts of SPECT and its lack of management impact in the literature.2,3