# The impact of fast vs. slow rubidium-82 infusion profile on precision and accuracy of PET myocardial blood flow perfusion metrics using a 1-tissue compartment model

## TL;DR

This study compares fast and slow rubidium-82 infusion rates for PET myocardial blood flow measurements, finding that fast infusions improve precision but not accuracy.

## Contribution

The study evaluates how infusion rate affects the precision and accuracy of a 1-tissue compartment model in PET myocardial perfusion imaging.

## Key findings

- Fast infusion improves precision with lower repeatability coefficients and coefficients of variance compared to slow infusion.
- 4DM 1-TCM overestimates resting myocardial blood flow in transmural scar regardless of infusion rate.
- HeartSee GSRM remains accurate and precise across both infusion profiles.

## Abstract

Gould’s simplified retention model (GSRM), as implemented in the HeartSee software, demonstrates 10% same-day test-retest precision for PET-CT myocardial perfusion using a 50 or 20 mL/min Rb-82 infusions. HeartSee-GSRM also accurately quantifies resting myocardial blood flow (rMBF) in transmural scar (0.26 mL/min/g), aligning with reference standards. However, the impact for varying infusion rates on precision and accuracy of a 1-tissue compartment model (1-TCM) as implemented within 4DM software remains unclear. We assessed whether varying infusion rates of Rb-82 impacts 1-TCM precision and accuracy.

Ninety-eight volunteers (Normals, Clinicals, and Infarcts), underwent 3D PET-CT stress testing. Three resting scans and two stress scans were performed with randomized fast (F) 50 mL/min or slow (S) 20 mL/min Rb-82 infusions. rMBF and stress MBF (sMBF) were calculated using 4DM software (1-TCM). Repeatability coefficients (RC) and coefficients of variance (COV) were calculated. Accuracy was assessed by comparing rMBF in infarcted myocardium (from 1-TCM and GSRM) against established reference standard for transmural myocardial scar (TMS). Fast infusion yielded better precision. RC was lower for F-F vs. S-S resting pairs (24.3% vs. 32.9%), and COV was lower (12.9% vs. 17.4%, P = 0.03). No difference in rMBF or sMBF was found between infusion rates (rMBF: 0.93 vs. 0.94 mL/min/g; sMBF: 2.23 vs. 2.30 mL/min/g). HeartSee GSRM produced rMBF values consistent with TMS (<0.30 mL/min/g), while 4DM 1-TCM overestimated rMBF (Fast: 0.79 ± 0.33; Slow: 0.82 ± 0.27 mL/min/g, P = 0.791), for both infusion profiles.

Fast infusion improves 4DM 1-TCM precision, but 4DM 1-TCM overestimates rMBF in TMS regardless of infusion rate. HeartSee GSRM remains accurate and precise across profiles.

Graphical Abstract