Comparison between 1-compartmental and 2-compartmental model in calculation of myocardium blood flow in 82Rb PET imaging

Abstract

Objective: To the best of our knowledge, no comparison between 1-compartmental (1cm) and 2-compartmental (2cm) models in calculation of myocardium blood flow (MBF) and coronary flow reserve (CFR) in ⁸²Rb PET imaging has been performed. We present our results of comparing 1cm and 2CM in ⁸²Rb myocardial PET imaging.

Methods: Twenty nine patients, mean age 58±9.5 years (mean±standard deviation), were imaged at rest and pharmaco-
logical stress, following an i.v. injection of 1850 MBq of ⁸²Rb each. A GE DLS PET-CT+16 scanner was used in this study. All images were acquired in 2D mode. For each study, 50 frames were acquired. The time per frame was 5sec between 0-3 min, 15sec between 3-5 min and 30 sec between 5-8 min. MBF was calculated by using 1cm and 2cm. The results for global and regional left circumflex artery (LCX), left anterior artery (LAD) and right coronary artery (RCA), rest and stress MBF, and CFR values obtained by 1cm and 2cm were compared by using Bland and Altman method. The reproducibility coefficient was calculated as 1.96 times the standard deviation (SD) of the differences between 1cm and 2cm values.

Results: The global rest MBF values, expressed as mean± SD, for both 1cm and 2cm were very similar (0.74 ± 0.17 vs. 0.73 ± 0.17 mL/min/g), and reproducibility was good, 0.12 mL/min/g (16.3% of the mean). The same held true for the 1CM and 2CM stress global MBF values (1.71 ± 0.54 and 1.73 ± 0.50 mL/min/g) with good reproducibility of 0.25 mL/min/g (14.4% of the mean). The regional, LCX, LAD and RCA rest and stress MBF values, obtained by 1cm and 2cm, were marginally reproducible, i.e., 50% or more of the mean. The global CFR values for both 1cm and 2cm were very similar (2.44 ± 0.84 vs. 0.2.44 ± 0.89), and reproducibility was good 0.34 (14.1% of the mean).

Conclusions: The MBF and CFR global rest and stress values obtained by 1cm and 2cm were close and reproducible. However, the regional LAD, RCA and LCX rest and stress MBF values showed marginal reproducibility. Limited regional MBF reproducibility may be caused by sampling error and/or cardiac and breathing motion. We believe that the reproducibility of regional values can be improved by data smoothing and motion gating.