Purpose: The aim of this study was to validate positron emission tomography feature tracking (PETFT) for assessing endocardial wall strain by comparing it with conventional tagging-cine magnetic resonance (MR) derived strain analysis (TAG).
Methods: Consecutive 62 patients who underwent ¹³N-ammonia PETMR (52 males, mean age 66 years) were enrolled. PETFT and TAG were obtained through simultaneous acquisition with electrocardiography-gated PET and cine-MR for rest scan. Global longitudinal and circumferential strain (GLS and GCS) were calculated. Correlations and Bland-Altman plots were employed to evaluate associations, bias, and 95% limit of agreement (LOA) between PETFT and TAG.
Results: PETFT and TAG showed significant correlations (r = 0.69 [95% CI: 0.54 to 0.80], p<0.0001; r = 0.55 [95% CI: 0.33–0.80], p<0.0001 for GCS and GLS, respectively). Bland-Altman plot showed acceptable agreements (Bias 0.7±6.7, LOA -12.5 to 13.9; Bias 1.3±5.5, LOA -9.5 to 12.0 for GCS and GLS, respectively). In patients with abnormal perfusion, the correlations were still significant (r = 0.76 [95% CI: 0.62 to 0.93], p<0.0001; r = 0.59 [95% CI: 0.18 to 0.82], p=0.007 for GCS and GLS, respectively)
Conclusion: PETFT has been identified as a feasible technique compared to TAG, demonstrating its potential as a novel tool for assessing wall strain in routine clinical practice. However, discrepancies in strain values may arise due to differences in algorithms and the presence of perfusion defects.

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The measurement of absolute myocardial blood flow (MBF) has played a pivotal role in the development of nuclear cardiology and other perfusion imaging techniques. However, the capacity to perform such experiments may be diminished. This review examines the basic physiology of microsphere measurement of absolute MBF which was developed over 50 years ago, with multiple refinements over time. The use of different types of microspheres is presented in depth. The set-up and performance of a large animal model is detailed with tips and pitfalls explained. It is the purpose of this review to stimulate the next generation of investigators into considering this skill as part of their research tool box.

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Background: The quantitative analysis of myocardial blood flow and myocardial flow reserve (MFR) is expected to address challenges in evaluating the relative distribution of myocardial perfusion imaging. This study aimed to determine the normal range of MFR index using the myocardial uptake ratio (MUR) method in normal volunteers (NV) with an Anger-type single photon emission computed tomography/computed tomography (SPECT/CT) system and to evaluate its diagnostic accuracy for ischemic heart disease (IHD) and heart failure (HF).
Method: Two methods for calculating the MUR were evaluated. The area under the curve (AUC) method utilized the AUC of the time-activity curve (TAC) of the aortic arch as the input function (AUC-based MFR index). The DOSE method employed the dose activity (dose-based MFR index). IHD was categorized into single-vessel disease (SVD) and multivessel disease (MVD; double- and triple-vessel disease combined).
Results: Normal range of AUC-based MFR index was 1.63±0.30, 1.40±0.24 for SVD, 1.28±0.17 for MVD, and 1.11±0.12 for HF. The normal range of the dose-based MFR index was 1.18±0.14, 1.15±0.26 for SVD, 1.02±0.10 for MVD, and 0.99±0.06 for HF. Significant differences were observed among the NV, MVD, and HF groups. No significant differences were noted between NV and SVD groups. The results of the receiver operating characteristic curve (ROC) analysis in combination with NV showed that the AUC of the ROC curve was 0.732 (95%CI 0.542–0.922) for SVD, 0.841 (95%CI 0.717–0.965) for MVD, and 0.969 (95%CI, 0. 922–1.0) for HF. The AUC of dose-based MFR index were 0.667 (95%CI 0.404–0.929) for SVD, 0.817 (95%CI 0.684–0.950) for MVD, and 0.908 (95%CI 0.814–1.0) for HF. DeLong’s test showed no significant differences between the AUC of AUC-based and dose-based MFR indices.
Conclusion: The findings suggest the potential clinical application of AUC and DOSE methods for quantitative analysis of the MFR index using an Anger-type SPECT/CT system. These methods are expected to enhance the accuracy of diagnosis and prognosis in patients with IHD and HF.

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