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Visualization and Quantification of Brown and Beige Adipose Tissues in Mice using [18F]FDG Micro-PET/MR Imaging
Published on: July 1, 2021
Optimizing protocol efficiency in [18F]flurpiridaz positron emission tomography myocardial perfusion imaging through
Maria Alwan1, Ahmad El Yaman1, Mahmoud Al Rifai1
1Houston Methodist DeBakey Heart & Vascular Center, Houston, TX, USA.
Background:
[18F]flurpiridaz is a newly FDA-approved tracer for positron emission tomography myocardial perfusion imaging (PET MPI) with a long half-life and improved physical characteristics. However, its long half-life leads to residual rest activity. Prior trials used 30 to 60 minutes delays between rest and stress injections and proposed stress-to-rest dose ratios of 1:2 to 1:3 to mitigate the potential impact of residual rest counts on the stress myocardial perfusion images.
Objective:
To evaluate the effect of stress-to-rest dose ratio and time interval between injections on residual activity.
Methods:
We analyzed consecutive 115 patients who underwent PET MPI with [18F]flurpiridaz. Relative residual activity was calculated as the ratio of tissue activity concentration (kBq/mL) in the first stress frame to that in the stress tissue phase. Linear regression was used to assess the association of dose ratio and injection time interval with global residual activity. The optimal dose ratio cutoff was identified. Mixed-effects models with interaction terms were used to assess whether the effect varied across vascular territories.
Results:
A total of 115 patients underwent PET MPI. Results showed that increasing the stress-to-rest dose ratio was significantly associated with lower relative residual activity (β = -3.41; 95% confidence interval (CI): -4.72; -2.11 per 1-unit increase), while increasing the time interval between injections up to 39 minutes showed no significant association (β = 0.03 95% CI: -0.12; 0.17 per 1-minute increase) within this time window. The optimal cutoff dose ratio to achieve relative residual activity <20% ranged between 3.2 and 4.3.
Conclusion:
Increasing the stress-to-rest dose ratio between 3.2 and 4.3 effectively reduces residual activity to <20% of the stress dose across all time intervals, thereby enabling back-to-back imaging and improving protocol efficiency on digital PET systems. Further validation is warranted for older, non-digital scanners.
Insights
Increasing the stress-to-rest dose ratio for [18F]flurpiridaz PET MPI effectively reduces residual activity. Optimal ratios between 3.2 and 4.3 enable efficient back-to-back imaging on digital PET systems.
Area of Science:
- Nuclear medicine
- Cardiovascular imaging
- Radiopharmaceutical science
Background:
- [18F]flurpiridaz is an FDA-approved PET tracer for myocardial perfusion imaging (MPI) with a long half-life.
- Its long half-life can cause residual rest activity, potentially impacting stress imaging.
- Previous studies suggested dose ratios and time delays to mitigate this issue.
Purpose of the Study:
- To evaluate how stress-to-rest dose ratio and injection time intervals affect residual activity in [18F]flurpiridaz PET MPI.
- To determine optimal parameters for reducing residual activity and improving imaging efficiency.
Main Methods:
- Analysis of 115 patients undergoing [18F]flurpiridaz PET MPI.
- Calculation of relative residual activity as the ratio of rest to stress tissue activity.
- Linear regression and mixed-effects models used to assess the impact of dose ratio and time interval.
Main Results:
- Higher stress-to-rest dose ratios significantly correlated with lower relative residual activity.
- Increasing the time interval between injections up to 39 minutes did not significantly reduce residual activity.
- An optimal dose ratio between 3.2 and 4.3 was identified to achieve <20% relative residual activity.
Conclusions:
- A stress-to-rest dose ratio of 3.2-4.3 effectively minimizes residual activity (<20%) for [18F]flurpiridaz PET MPI.
- This finding supports back-to-back imaging protocols and enhances efficiency on digital PET systems.
- Further validation is needed for older, non-digital PET scanners.
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