Receiver Operator Characteristic Confirmation of Potential for Radiation Dose Reduction with Improved Reconstruction for Cardiac SPECT

Dose fractionation is a popular proposed method to lower the radioactive exposure to patients undergoing myocardial perfusion imaging (MPI) SPECT/CT. Recently, we optimized reconstruction strategies employed during dose fractionation in MPI using polar maps in combination with the calculation of total perfusion deficit (TPD) scores employing hybrid defects of various sizes. Although observed to agree well with experienced observers, TPD scores have not been used to judge the impact of reduced dose SPECT imaging for standard two-headed SPECT systems. Thus, the aim of this study was to confirm that the optimized reconstruction strategies are indeed ranked accordingly by TPD in comparison to human observers reading hybrid cardiac defects studies with known truth. We setup our human observer study with 126 test cases and 44 training cases. Four observers participated by reading three different reconstruction strategies, ordered-subset expectation maximization with the original dose, (OSEM100), OSEM with only 25% of the dose (OSEM25), and filtered backprojection with the original dose (FBP100). Before commencing the reading of the actual test cases, training with feedback were done for each of the reconstruction strategies. The test cases were read in nine randomized sessions (42 test cases per session), three for each reconstruction strategy with 8 training images as a warm-up with feedback (50 image sets per reading session). The order of reading the different sets as well as the order of the test cases were different for each observer. ROCKIT (University of Chicago) software was used to analyze the observer data. Areas under the curve (AUC) values of 0.786, 0.754, and 0.643 were recorded for OSEM100, OSEM25, and FBP100 respectively. The ranking of the reconstruction strategies is the same as for the TPD scoring method, while the observers performed worse scoring FBP100.