Half-Time SPECT Myocardial Perfusion Imaging with Attenuation Correction

Abstract

Reducing acquisition time may improve patient throughput, increase camera efficiency, and reduce costs; reducing acquisition time also increases image noise. Newly available software controls the effects of noise by maximum a posteriori reconstruction while maintaining resolution with resolution-recovery methods. This study compares half-time (HT) gated myocardial SPECT images processed with ordered-subset expectation maximization with resolution recovery (OSEM-RR) (with and without CT-based attenuation correction [AC]) with full-time (FT) images obtained with a standard clinical protocol and reconstructed with filtered backprojection (FBP) and OSEM (with and without AC). Methods: A total of 212 patients (mean age, 57 y; age range, 27-86 y) underwent 1-d rest/stress 99m Tc-tetrofosmin gated SPECT. FT (12.5 min, both rest and stress) and HT (rest, 7.5 min; stress, 6.0 min) images were acquired with low-dose CT for AC in 112 patients. HT acquisitions were processed with OSEM-RR (with and without AC) using software, and FT acquisitions were processed with FBP and OSEM (with and without AC). In another 100 patients, test-retest repeatability was assessed using 2 sets of FT images (FBP reconstruction) that were acquired one immediately after the other. Radiologists unaware of the acquisition and reconstruction protocols visually assessed all reconstructed images for summed stress, summed rest, and summed difference scores and regional wall motion using a 17-segment model. Automated analysis on gated SPECT was used to determine left ventricular volumes, ejection fraction, and dilation (end-diastolic volume, end-systolic volume, left ventricular ejection fraction, and transient ischemic dilation [TID]). A clinical diagnosis was also determined. Results: All measurements resulted in significant correlations (P , 0.01) between the HT and FT images. The only significant difference in mean values was for OSEM-RR plus AC; this method led to an increase in TID by 4% over FT imaging. The concordance in the clinical diagnosis for HT versus FT was 106 to 112 (k 5 0.88) for no AC and 102 to 106 (k 5 0.91) for AC, similar to the repeatability of FT versus FT (98/100, k 5 0.95). Conclusion: HT images processed with the new algorithm provided a clinical diagnosis in concordance with that from FT images in 95% (no AC) to 96% (AC) of cases. This concordance is similar to the test-retest repeatability of FT imaging.

Reduced-time myocardial perfusion study processed with “Myovation Evolution” — assessment of diagnostic efficacy

“…Those values are not as high as the ones presented by Ali et al [6], Valenta et al [7], and Armstrong et al [8], who also made use of "Evolution for Cardiac" software package. They obtained agreement between full time and half time studies equal to 95% without AC and 96% with AC [6], 96% with 100% agreement in a clinical interpretation [7], and 83% to 96% (in case of acceptance of minor inconsistencies) [8]. A more detailed analysis of results presented in specified above publications was provided in our previous publication [5].…”

Nuclear myocardial perfusion imaging using thallium-201 with a novel multifocal collimator SPECT/CT: IQ-SPECT versus conventional protocols in normal subjects

“…Complementary information such as calcium scoring could be obtained with SPECT/CT [13], although Symbia T6 cannot perform CT coronary angiography for fusion imaging between CT and MPI [14]. Attenuation correction could be successfully achieved with a CT attenuation map, and this method is more patient-specific to compensate for attenuation [17].…”

New SPECT technology: potential and challenges

“…Siemens Smartzoom collimator, a recent revision of cardiofocal collimation [15]) and/or reconstruction strategies (e.g. modelling the system spatial response [16,17]). Bocher et al point out a wide range of potential applications for the new technology, mainly applications that are feasible with standard gamma cameras, but where the newer technology offers potential technical advantage.…”