Muneo Ohba

Diagnostic accuracy of cardiac metaiodobenzylguanidine scintigraphy in Parkinson disease

Background and purpose:  To estimate the diagnostic accuracy of cardiac 123I‐metaiodobenzylguanidine (MIBG) scintigram for detection of Parkinson disease.

Automated quantitation of pericardiac fat from noncontrast CT.

Introduction:Increased abdominal visceral fat has been shown to be a cardiovascular risk factor. Preliminary studies indicate that pericardiac fat (PF) may provide similar information. We aimed to develop new software (QFAT) for automatic quantitation of PF from noncontrast cardiac CT and compare PF measures to other cardiovascular risk factors. Methods:QFAT accepts user-defined range of noncontrast transverse cardiac CT slices, automatically segments the heart, and determines PF volume (PFV) as contiguous pericardial fat voxels. PFV normalized to cardiac volume defines PF ratio (PFR). QFAT and manual processing (MAN) was performed in 105 patients (mean BMI, 27; range, 17–41) by 2 observers. Results:Mean processing time was 20 ± 4 seconds for QFAT, and 9 ± 6 minutes for MAN. There was excellent agreement between QFAT and MAN for PFV (R = 0.98) and PFR (R = 0.98). MAN and QFAT interobserver variability were comparable. Interscan and interscanner variability for PFV and PFR were comparable to corresponding interobserver variability. PFV (R = 0.88, P < 0.0001) and PFR (R = 0.81, P < 0.0001) correlated strongly with abdominal visceral fat area, moderately with BMI (R = 0.58, P < 0.0001 and R = 0.48, P < 0.0001), and weakly with abdominal subcutaneous fat area (R = 0.33, P < 0.0001 and R = 0.32, P = 0.001). Conclusions:PFV and PFR can be accurately and automatically quantified from noncontrast CT acquired for coronary calcium screening and may provide complementary information regarding cardiovascular risk.

Automatic Global and Regional Phase Analysis from Gated Myocardial Perfusion SPECT Imaging: Application to the Characterization of Ventricular Contraction in Patients with Left Bundle Branch Block

Although many patients with heart failure benefit from cardiac resynchronization therapy (CRT), predicting which patients will respond to CRT remains challenging. Recent evidence suggests that the analysis of mechanical dyssynchrony using gated myocardial perfusion SPECT (MPS) may be an effective tool. The aim of this study was to evaluate global and regional gated MPS dyssynchrony measurements by comparing parameters obtained from patients with a low likelihood (LLk) of conduction abnormalities and coronary artery disease and patients with left bundle branch block (LBBB). Methods: A total of 86 consecutive patients with LLk and 72 consecutive patients with LBBB, all without prior myocardial infarction or sternotomy, were studied using gated MPS. Global (histogram SD [σ], bandwidth [β], and entropy [ε]) and regional (wall- and segment-based differences of means [ΔμW and ΔμS, respectively] or modes [ΔMW and ΔMS, respectively]) dyssynchrony measures were calculated by Fourier harmonic phase-angle analysis of local myocardial count variations over the cardiac cycle for each patient, and then unpaired t tests were used to determine which parameters were sex-specific and how well they discriminated between the LLk and LBBB populations. Receiver-operating-characteristic analysis was also performed to calculate the area under the curve (AUC), sensitivity (Ss), specificity (Sp), and optimal threshold (Th). Results: Global parameters were found to be sex-specific, whereas regional differences were sex-independent. All parameters studied showed statistically significant differences between the groups (all global, P < 0.05; all regional, P < 0.0001). Receiver-operating-characteristic analysis yielded higher AUC, Ss, and Sp for ε and regional parameters (ε: AUC = 0.95/0.96, Ss = 94%/88%, Sp = 89%/91%, and Th = 53.9%/60.6% for women/men; ΔμW: AUC = 0.93, Ss = 88%, Sp = 86%, and Th = 10.5°; ΔμS: AUC = 0.94, Ss = 90%, Sp = 94%, and Th = 9.2°; ΔMW: AUC = 0.95, Ss = 90%, Sp = 94%, and Th = 15°; and ΔMS: AUC = 0.95, Ss = 88%, Sp = 90%, and Th = 10.5°) than for global parameters (σ: AUC = 0.75/0.67, Ss = 81%/66%, Sp = 63%/64%, and Th = 16.5°/22.2° for women/men; β: AUC = 0.80/0.72, Ss = 71%/71%, Sp = 79%/64%, and Th = 69°/81° for women/men). Conclusion: The computed parameters all discriminate effectively between LLk and LBBB populations. Measurements that are less dependent on the shape of the phase-angle distribution histogram provided higher sensitivity and specificity for this purpose. Further study is needed to evaluate these parameters for the purpose of predicting response to CRT.

Motion-Frozen Myocardial Perfusion SPECT Improves Detection of Coronary Artery Disease in Obese Patients

In this study, we compared the diagnostic performance of the standard SPECT with motion-frozen (MF) myocardial perfusion SPECT (MPS) in obese patients. Methods: A total of 90 consecutive obese patients (body mass index, 30.1–46.8, average, 34.3 ± 3.6; age, 63 ± 12 y; 30% women) underwent standard supine rest 201Tl/stress 99mTc dual-isotope gated MPS and cardiac catheterization within 3 mo. MF images were obtained by nonlinear warping of cardiac phases to the end-diastolic position. Total perfusion deficit (TPD) was obtained for summed (S-TPD) and motion-frozen (MF-TPD) datasets with sex-specific standard and MF normal limits. Results: The area under the receiver-operating-characteristic (ROC) curve for detection of coronary artery disease (CAD) by MF-TPD was significantly larger than that for S-TPD (0.93 ± 0.25 vs. 0.88 ± 0.32, P < 0.05). MF-TPD had higher specificity (77% vs. 55%, P < 0.05) and accuracy (89% vs. 80%, P < 0.05) than did S-TPD. Conclusion: MF processing of MPS improves CAD detection in obese patients.

Comparison of myocardial blood flow induced by adenosine triphosphate and dipyridamole in patients with coronary artery disease

Myocardial perfusion imaging with adenosine triphosphate (ATP) has been used increasingly to diagnose coronary artery disease (CAD) and assess risk for this disease. This study compared absolute myocardial blood flow (MBF) and myocardial flow reserve index (MFR) with ATP and dipyridamole (DIP) in patients with CAD. MBF was quantified by15O-H2O PET in 21 patients with CAD (17 male, 4 female), aged 55 to 81 years. MBF was measured at rest, during intravenous injection of ATP (0.16 mg/kg/min), and again after DIP infusion (0.56 mg/kg). Regions of interest were drawn in nonischemic and ischemic segments based on findings from fhallium-201 (2O1T1) scintigraphy and coronary angiography (CAG). Absolute MBF values and indexes of MFR were calculated in nonischemic and ischemic segments. Intravenous injection of ATP and DIP significantly increased MBF in nonischemic (2.4 ± 0.9 and 2.1 ± 0.8 m//g/min, respectively; p < 0.01, for both) and in ischemic segments (1.3 ± 0.4 and 1.5 ± 0.4 m//g/min, respectively; p < 0.01, for both). There was a significant difference in MBF values between ATP and DIP in nonischemic segments (p < 0.05), which was not observed in ischemic segments. In nonischemic segments, ATP produced higher MFR than DIP (2.1 ± 0.8 and 1.8 ± 0.7, respectively; p < 0.05), while no significant difference was observed in ischemic segments (1.5 ± 0.6 and 1.7 ± 0.3, respectively). ATP produced a greater hyperemia than DIP between the ischemic and nonischemic myocardium in patients with CAD. ATP is as effective as DIP for the diagnosis of CAD.

Myocardial metabolism of 123

1 Department of Cardiovascular Medicine, and Nuclear Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan 2 Department of Cardiology, Kitano Hospital, The Tazuke Kofukai Medical Research Institute, 2-4-20 Ohgimachi, Kita-ku, Osaka 530-8480, Japan 3 Molecular Imaging, Biomedical Imaging Research Center, Fukui Medical University, Fukui, Japan 4 Department of Cardiology, Nara Hospital, Kinki University School of Medicine, Nara, Japan