Purpose: Iterative reconstruction methods based on ordered-subset expectation maximisation (OSEM) has replaced filtered backprojection (FBP) in many clinical settings owing to the superior image quality. Whether OSEM is as accurate as FBP in quantitative positron emission tomography (PET) is uncertain. We compared the accuracy of OSEM and FBP for regional myocardial (18)F-FDG uptake and (13)NH(3) perfusion measurements in cardiac PET.
Methods: Ten healthy volunteers were studied. Five underwent dynamic (18)F-FDG PET during hyperinsulinaemic-euglycaemic clamp, and five underwent (13)NH(3) perfusion measurement during rest and adenosine-induced hyperaemia. Images were reconstructed using FBP and OSEM +/- an 8-mm Gaussian post-reconstruction filter.
Results: Filtered and unfiltered images showed agreement between the reconstruction methods within +/-2SD in Bland-Altman plots of K (i) values. The use of a Gaussian filter resulted in a systematic underestimation of K (i) in the filtered images of 11%. The mean deviation between the reconstruction methods for both unfiltered and filtered images was 1.3%. Agreement within +/-2SD between the methods was demonstrated for perfusion rate constants up to 2.5 min(-1), corresponding to a perfusion of 3.4 ml g(-1) min(-1). The mean deviation between the two methods for unfiltered data was 2.7%, and for filtered data, 5.3%.
Conclusion: The (18)F-FDG uptake rate constants showed excellent agreement between the two reconstruction methods. In the perfusion range up to 3.4 ml g(-1) min(-1), agreement between (13)NH(3) perfusion obtained with OSEM and FBP was acceptable. The use of OSEM for measurement of perfusion values higher than 3.4 ml g(-1) min(-1) requires further evaluation.