Research ArticleClinical Investigation

Future of Radionuclide Myocardial Perfusion Imaging: Transitioning from SPECT to PET

Marcelo F. Di Carli
Journal of Nuclear Medicine November 2023, 64 (Supplement 2) 3S-10S; DOI: https://doi.org/10.2967/jnumed.122.264864

Article Figures & Data

Figures

  • FIGURE 1.
    FIGURE 1.

    Rest and stress SPECT and PET MPI images obtained 2 wk apart on 74-y-old man with known CAD and prior percutaneous coronary intervention presenting with recurrent chest pain. Patient initially underwent rest and stress SPECT MPI. He exercised for 10:00 min of Bruce protocol. His heart rate increased from 58 bpm at rest to peak of 134 bpm (92% of age-predicted maximal heart rate), and blood pressure increased from 130/64 mm Hg at rest to 148/62 mm Hg at peak exercise (rate–pressure product, 19,832). Patient developed chest pain and 2.5 mm of ST segment depression in leads II, III, aVF, and V3–V6, which resolved 11 min into recovery. SPECT images did not show significant perfusion defects. Patient was then referred for rest/stress PET MPI, which demonstrated large and severe perfusion defect throughout inferior and inferolateral walls with complete reversibility. This was associated with significant reduction in MFR in right coronary artery territory, associated with markedly reduced relative flow reserve. Coronary angiography showed 95% stenosis in mid right coronary artery and 70% stenosis in distal right coronary artery. There was 50% lesion in proximal left anterior descending coronary artery with normal instantaneous wave-free ratio. LAD = left anterior descending coronary artery; LCX = left circumflex coronary artery; LM = left main coronary artery; RCA = right coronary artery; RFR = relative flow reserve.

  • FIGURE 2.
    FIGURE 2.

    Reclassification of severe ischemia by automated perfusion assessment between PET and SPECT MPI (24). Among patients with severe ischemia by PET, 41% had either no or mild ischemia when myocardial perfusion was measured via SPECT. Conversely, among patients with severe ischemia on SPECT, 42% had less than severe ischemia by PET MPI.

  • FIGURE 3.
    FIGURE 3.

    (Top) Cumulative adjusted incidence of cardiac mortality for tertiles of coronary flow reserve presented in Kaplan–Meier format showing significant association between coronary flow reserve and cardiac mortality. (Bottom) Unadjusted annualized cardiac mortality by tertiles of coronary flow reserve and categories of myocardial ischemia. Annual rate of cardiac death increased with increasing summed difference score and decreasing coronary flow reserve. Importantly, lower coronary flow reserve consistently identified higher-risk patients at every level of myocardial ischemia, including among those with visually normal PET scans and normal left ventricular function. CFR = coronary flow reserve; HR = hazard ratio. (Reprinted with permission of (36).)

  • FIGURE 4.
    FIGURE 4.

    (Left) Scatterplot of coronary flow reserve and maximal MBF by cardiovascular death. Concordant and discordant impairment of coronary flow reserve and maximal MBF identifies unique prognostic phenotypes of patients. Coronary flow reserve < 2 and maximal MBF < 1.8 mL⋅g−1⋅min−1 were defined as impaired. (Right) Unadjusted annualized cardiovascular mortality for 4 groups based on concordant or discordant impairment of CFR and maximal MBF. CD = cardiac death; CFR = coronary flow reserve; CV = cardiovascular; FU = follow-up; mMBF = maximal MBF. (Reprinted with permission of (35).)

  • FIGURE 5.
    FIGURE 5.

    Examples of patients with and without CMD. (A) A 58-y-old man with hypertension and diabetes evaluated for atypical chest pain. (B) A 63-y-old man with hypertension, diabetes, and high cholesterol evaluated for dyspnea. In both cases, myocardial perfusion results are normal, suggesting no evidence of flow-limiting CAD. Patient A has normal stress MBF and MFR. However, patient B shows severely reduced stress MBF and MFR. Follow-up CT coronary angiography showed no evidence of obstructive CAD. Thus, abnormalities in coronary vasoreactivity in patient B are consistent with CMD. CFR = coronary flow reserve; LAD = left anterior descending coronary artery; LCX = left circumflex coronary artery; LV = left ventricular; RCA = right coronary artery.

  • FIGURE 6.
    FIGURE 6.

    Unadjusted annualized rate of cardiac death and nonfatal myocardial infarction by coronary artery calcium score and myocardial flow reserve category. At every calcium score stratum, there is increased rate of adverse events with reduced myocardial flow reserve. MI = myocardial infarction. (Reprinted with permission of (58).)

  • FIGURE 7.
    FIGURE 7.

    Comparison of outcomes by expert reader standard CAC score from electrocardiography-gated CT vs. score calculated automatically by deep learning from PET/CT attenuation correction maps. (Top) Kaplan–Meier curves for major adverse cardiac event risk by coronary artery calcium score categories. (Bottom) Univariate major adverse cardiac event risk analysis using proportional-hazards Cox model. CAC = coronary artery calcium; CTAC = CT attenuation correction; DL = deep learning; ECG = electrocardiography. (Reprinted with permission of (70).)

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