Characterization of 3D PET systems for accurate quantification of myocardial blood flow

Abstract

Three-dimensional (3D) mode imaging is the current standard for positron emission tomography-computed tomography (PET-CT) systems. Dynamic imaging for quantification of myocardial blood flow (MBF) with short-lived tracers, such as Rb-82- chloride (Rb-82), requires accuracy to be maintained over a wide range of isotope activities and scanner count-rates. We propose new performance standard measurements to characterize the dynamic range of PET systems for accurate quantitative imaging. Methods: 1100-3000 MBq of Rb-82 or N-13-ammonia was injected into the heart wall insert of an anthropomorphic torso phantom. A decaying isotope scan was performed over 5 half-lives on 9 different 3D PET-CT systems and 1 3D/twodimensional (2D) PET-only system. Dynamic images (28x15s) were reconstructed using iterative algorithms with all corrections enabled. Dynamic range was defined as the maximum activity in the myocardial wall with <10% bias, from which corresponding dead-time, count-rates and/or injected activity limits were established for each scanner. Scatter correction residual bias was estimated as the maximum cavity blood-tomyocardium activity ratio. Image quality was assessed via the coefficient of variation measuring non-uniformity of the left ventricle (LV) myocardium activity distribution. Results: Maximum recommended injected activity/body-weight, peak dead-time correction factor, count-rates and residual scatter bias for accurate cardiac MBF imaging were: 3-14 MBq/kg, 1.5-4.0, 22-64 Mcps singles and 4-14 Mcps prompt coincidence count-rates, and 2-10% on the investigated scanners. Non-uniformity of the myocardial activity distribution varied from 3-16%. Conclusion: Accurate dynamic imaging is possible on the 10 3D-PET systems if the maximum injected MBq/kg values are respected to limit peak dead-time losses during the bolus first-pass transit.