Optimization of dynamic Rb-82 PET cardiac acquisition protocol using Monte-Carlo simulation

Abstract

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Objectives: The goal of this study is to optimize the dynamic Rb-82 PET acquisition protocol in quantitative studies of tracer transport between blood and myocardial tissue.

Methods: Time activity curves (TACs) of blood pool, myocardium, and other organs were extracted from Rb-82 PET images from 5 normal patients. The TACs were averaged and smoothed to determine the activities in the first 2 minutes after injection. The resulting TACs were used to create a 4D NCAT phantom representing the distribution of Rb-82 in a normal patient. A combined simSET and GATE Monte-Carlo simulation tool was used to simulate nearly-noise-free PET data that were scaled to clinical count level before Poisson noise fluctuations were added. The simulated datasets were reconstructed using standard OS-EM algorithm. With the Munich Heart program, we performed two-compartmental analyses and extracted kinetic rate constants from noisy images with different acquisition protocols and from noise-free images. Bias versus variance curves for the rate constants were generated and compared for different acquisition protocols.

Results: With increasing post-reconstruction smoothing, our results indicated increasing bias and decreasing variance in the estimated rate constants. Very large or small acquisition time intervals had adverse effects on the accuracy and precision of the kinetic parameters. The optimal acquisition protocol was determined to be 10 points at 12 sec intervals based on the trade-off between bias and variance.

Conclusions: A study based on clinical data and accurate simulation was conducted to determine the optimal acquisition protocol for dynamic Rb-82 PET imaging. The protocol of 10 points at 12 sec intervals was selected based on the trade-off between accuracy and precision in the determination of tracer kinetic parameters.

Research Support: NIH R01-EB000168