Differences between 1-compartmental and 2-compartmental model in calculation of MBF in Rb-82 PET imaging

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

Methods Twenty seven patients, mean age 57± 8.3, were imaged at rest and pharmacological stress, following an i.v. injection of 1850 MBq of Rb-82 each. A GE DLS PET-CT+16 scanner was used in this study and 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 1 & 2 CM. The results for global and regional LAD, RCA and LCX, rest and stress MBF, and CFR values obtained by 1 & 2 CM were compared by using Bland and Altman method. The reproducibility coefficient was calculated as 1.96 times the SD of the differences between 1 & 2 CM values.

Results The global rest MBF values for both 1 & 2 CM were very similar (0.75 ± 0.17 vs. 0.75 ± 0.17 mL/min/g), and reproducibility was good, 0.12 mL/min/g (15.6% of the mean). The same held true for the stress global MBF values (1.71 ± 0.52 and 1.73 ± 0.47 mL/min/g) with good reproducibility of 0.26 mL/min/g (14.9% of the mean). The regional LCX, LAD and RCA rest and stress MBF values were poorly reproducible, i.e., 50% or more of the mean. The global CFR values for both 1 & 2 CM were very similar (2.37 ± 0.72 vs. 0.2.37 ± 0.80), and reproducibility was good 0.33 (14.1% of the mean).

Conclusions The MBF and CFR global rest and stress values obtained by 1 & 2 CM were close and reproducible. However, the regional LAD, RCA and LCX rest and stress MBF values showed poor reproducibility. Poor 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