C-11 acetate has excellent reproducibility for quantification of myocardial oxidative metabolism

Abstract

Aims: C-11 acetate PET imaging allows quantification of myocardial oxidative metabolism. We sought to assess the reproducibility of such analysis with the Carimas software.

Methods and results: The myocardial oxygen consumption rate was assessed via a kmono index--the clearance rate constant of a mono-exponential function fitted to a C-11 acetate clearance curve. Two observers of different experience levels--a novice and an expert--analysed 53 C-11 acetate PET studies--each study twice. These results were compared using Bland-Altman (BA) plots with the global kmono-s obtained earlier with a validated reference method. We also assessed intra- and interobserver reproducibility on global, regional, and segmental [17-segment model (AHA)] levels--a linear mixed model for the repeated measures was fitted to our data--using intraclass correlation coefficients (ICCs) and differences between repeats and the observers. Carimas kmono values were lower than the reference--by 10.7% in the novice and by 9.6% in the expert, and were in substantial agreement with it--R(2) values were 0.944 and 0.943 correspondingly; the coefficients of repeatability--1.96 SD of biases in BA plots--were 11.2% in both the observers. The intra- and interobserver ICCs were high on global and regional levels--above 0.99 in the novice and 0.96 in the expert. The intra- and interobserver differences were low on global and regional levels, the most pronounced being the left anterior descending artery (LAD) interobserver difference of 2.2%.

Conclusion: The study showed extremely good reproducibility-both intra- and interobserver-for C-11 acetate PET analysis of myocardial oxidative metabolism.

Keywords: C-11 acetate; Myocardial metabolism; Oxidative metabolism; Reproducibility.