Myocardial perfusion quantitation with super(15)O-labelled water PET: high reproducibility of the new cardiac analysis software (Carimas registered )

Purpose: Carimas registered (Cardiac Image Analysis System) is a new software package developed at the Turku PET Centre for the quantitation of PET studies of the heart with a broad range of tracers. The goal of this study was to assess the reproducibility of results the package provides for myocardial perfusion (MP) quantitation using super(15)O-labelled water. Methods: Four observers with various levels of experience in nuclear medicine independently analysed 20 MP studies (10 rest flow: 'rest', 10 adenosine-induced hyperaemia: 'stress'). Each study was analysed twice. The linear mixed model for repeated measures was fitted to the data to calculate intraclass correlation coefficients (ICC), differences between the repeats (the intraobserver differences) and differences between the observers (the interobserver differences). Also, Pearson correlation coefficients (r) were calculated and Bland-Altman plots were drawn. The reproducibility of MP was assessed on global, regional and segmental levels. Thereafter, this analysis was applied in 48 consecutive clinical patients with suspected coronary heart disease (CHD). Results: For the experienced observer the Pearson r for all segments was 0.974 at rest and 0.978 at stress (p