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Published on: December 28, 2013
Consistent tracer administration profile improves test-retest repeatability of myocardial blood flow quantification
Ran Klein1,2,3, Adrian Ocneanu4, Jennifer M Renaud5
1National Cardiac PET Centre, Division of Cardiology, Department of Medicine, University of Ottawa Heart Institute, Ottawa, Canada. rklein@toh.on.ca.
Objectives:
Quantification of myocardial blood flow (MBF) and stress/rest flow reserve is used increasingly to diagnose multi-vessel coronary artery disease and micro-vascular disease with PET imaging. However, variability in the measurements may limit physician confidence to direct revascularization therapies based on specific threshold values. This study evaluated the effects of rubidium-82 (82Rb) tracer injection profile using a constant-activity-rate (CA) vs a constant-flow-rate (CF) infusion to improve test-retest repeatability of MBF measurements.
Method:
22 participants underwent single-session 82Rb dynamic PET imaging during rest and dipyridamole stress using one of 2 test-retest infusion protocols: CA-CA (n = 12) or CA-CF (n = 10). MBF was quantified using a single-tissue-compartment model (1TCM) and a simplified retention model (SRM). Non-parametric test-retest repeatability coefficients (RPCnp) were compared between groups. Myocardium-to-blood contrast and signal-to-noise ratios of the late uptake images (2 to 6 minutes) were also compared to evaluate standard myocardial perfusion image (MPI) quality.
Results:
MBF values in the CA-CA group were more repeatable (smaller RPCnp) than the CA-CF group using the 1TCM at rest alone, rest and stress combined, and stress/rest reserve (21% vs 36%, 16% vs 19%, and 20% vs 27%, P < 0.05, respectively), and using the SRM at Rest and Stress alone, Rest and Stress combined, and stress/rest reserve (21% vs 38%, 15% vs 25%, 22% vs 38%, and 23% vs 49%, P < 0.05, respectively). In terms of image quality, myocardium-to-blood contrast and signal-to-noise ratios were not significantly different between groups.
Conclusions:
Constant-activity-rate 'square-wave' infusion of 82Rb produces more repeatable tracer injection profiles and decreases the test-retest variability of MBF measurements, when compared to a constant-flow-rate 'bolus' administration of 82Rb, especially with SRM, and without compromising standard MPI quality.
Insights
Constant-activity-rate infusion of rubidium-82 (82Rb) improves the repeatability of myocardial blood flow (MBF) measurements compared to constant-flow-rate infusion. This enhanced repeatability aids in diagnosing coronary artery disease with PET imaging.
Area of Science:
- Nuclear Cardiology
- Cardiovascular Imaging
- Radiopharmaceutical Dosimetry
Background:
- Myocardial blood flow (MBF) quantification using PET is crucial for diagnosing coronary artery disease.
- Variability in MBF measurements can reduce physician confidence in treatment decisions.
- Optimizing tracer delivery is essential for improving the reliability of PET-based assessments.
Purpose of the Study:
- To evaluate the impact of rubidium-82 (82Rb) tracer injection profiles on MBF measurement repeatability.
- To compare constant-activity-rate (CA) vs. constant-flow-rate (CF) infusion methods.
- To determine if improved repeatability affects myocardial perfusion imaging (MPI) quality.
Main Methods:
- 22 participants underwent rest and stress 82Rb dynamic PET imaging.
- Two infusion protocols were used: CA-CA (n=12) and CA-CF (n=10).
- MBF was quantified using a single-tissue-compartment model (1TCM) and a simplified retention model (SRM); test-retest repeatability coefficients (RPCnp) were compared.
Main Results:
- The CA-CA group showed significantly better MBF repeatability than the CA-CF group for both 1TCM and SRM models (e.g., 21% vs. 36% RPCnp for 1TCM at rest).
- Repeatability improvements were observed for rest, stress, combined, and stress/rest reserve measurements.
- No significant differences in myocardium-to-blood contrast or signal-to-noise ratios were found between groups.
Conclusions:
- Constant-activity-rate (CA) infusion of 82Rb enhances tracer injection profile repeatability.
- This leads to decreased test-retest variability in MBF measurements, particularly with the SRM.
- The CA method improves diagnostic reliability without compromising standard MPI quality.
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