Naoto Kawaguchi

Qualitative and Quantitative Assessment of Adenosine Triphosphate Stress Whole-Heart Dynamic Myocardial Perfusion Imaging Using 256-Slice Computed Tomography

Background The aim of this study was to investigate the correlation of the qualitative transmural extent of hypoperfusion areas (HPA) using stress dynamic whole-heart computed tomography perfusion (CTP) imaging by 256-slice CT with CTP-derived myocardial blood flow (MBF) for the estimation of the severity of coronary artery stenosis. Methods and Results Eleven patients underwent adenosine triphosphate (0.16 mg/kg/min, 5 min) stress dynamic CTP by 256-slice CT (coverage: 8 cm, 0.27 s/rotation), and 9 of the 11 patients underwent coronary angiography (CAG). Stress dynamic CTP (whole–heart datasets over 30 consecutive heart beats in systole without spatial and temporal gaps) was acquired with prospective ECG gating (effective radiation dose: 10.4 mSv). The extent of HPAs was visually graded using a 3-point score (normal, subendocardial, transmural). MBF (ml/100g/min) was measured by deconvolution. Differences in MBF (mean ± standard error) according to HPA and CAG results were evaluated. In 27 regions (3 major coronary territories in 9 patients), 11 coronary stenoses (> 50% reduction in diameter) were observed. In 353 myocardial segments, HPA was significantly related to MBF (P < 0.05; normal 295 ± 94; subendocardial 186 ± 67; and transmural 80 ± 53). Coronary territory analysis revealed a significant relationship between coronary stenosis severity and MBF (P < 0.05; non-significant stenosis [< 50%], 284 ± 97; moderate stenosis [50–70%], 184 ± 74; and severe stenosis [> 70%], 119 ± 69). Conclusion The qualitative transmural extent of HPA using stress whole-heart dynamic CTP imaging by 256-slice CT exhibits a good correlation with quantitative CTP-derived MBF and may aid in assessing the hemodynamic significance of coronary artery disease.

Three-dimensional phase-sensitive inversion recovery sequencing in the evaluation of left ventricular myocardial scars in ischemic and non-ischemic cardiomyopathy: Comparison to three-dimensional inversion recovery sequencing

BACKGROUND Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) is a useful technique for detecting myocardial fibrosis. LGE images are typically acquired using the inversion recovery (IR) method. Recently, phase-sensitive inversion recovery (PSIR) technology has been developed. The purpose of this study was to evaluate free-breathing 3D PSIR sequencing in comparison with breath-held 3D IR sequencing for the detection of myocardial fibrosis. METHODS One hundred twenty-three patients with suspected ischemic cardiac disease (n=27) or non-ischemic cardiomyopathy (hypertrophic cardiomyopathy, n=29; dilated cardiomyopathy, n=22; sarcoidosis, n=21; arrhythmia, n=9; myocarditis, n=4; amyloidosis, n=3; and others, n=8) were evaluated by LGE-MRI, which was performed first with the IR sequence and then with the PSIR sequence, using a 3T MRI scanner. Image quality was scored by two independent readers using a four-point scale. The 3D LGE volume was analyzed quantitatively and compared between both sequencing methods. RESULTS There was no significant difference in overall image quality (p=0.19). LGE was detected in 73 patients, who were evaluated visually. Ultimately, 58 patients with acceptable image quality were enrolled in further quantitative analyses (volume assessment). Although quantification of LGE volume revealed a strong correlation between both methods, larger LGE volumes were detected with PSIR compared to IR in patients suspected of non-ischemic cardiomyopathy (39.5 ± 25.9 cm(3) for PSIR and 32.8 ± 23.9 cm(3) for IR, p<0.001). The LGE volume did not differ significantly in patients suspected of ischemic cardiac disease (17.9 ± 12.7 cm(3) for PSIR and 17.5 ± 11.1cm(3) for IR, p=0.34). CONCLUSIONS 3D PSIR is suitable for detection of LGE and may be an option in cases with IR images of unacceptable quality but overestimates LGE volume in non-ischemic cardiomyopathy.

Clinical Usefulness of Coronary Flow Reserve Ratio for the Detection of Significant Coronary Artery Disease on 13N-Ammonia Positron Emission Tomography

BACKGROUND This study aimed to evaluate the diagnostic performance of coronary flow reserve (CFR), hyperemic myocardial blood flow (hMBF), and CFR ratio for detecting significant coronary artery disease (CAD) on 13N-ammonia positron emission tomography (PET).Methods and Results:We analyzed 63 patients (mean age, 71±9 years; 43 males) with suspected CAD who underwent both pharmacological stress/rest 13N-ammonia PET and coronary angiography. CFR and hMBF for PET were calculated automatically using quantitative PET software, and the CFR ratio was defined as the ratio of per-vessel CFR to maximum CFR in a standard 17-segment model. We compared the diagnostic performance among the 3 quantitative values. In the per-vessel analysis, 55 vessels were diagnosed as significant CAD (≥70% stenosis and/or fraction flow reserve ≤0.8). CFR, hMBF, and CFR ratio of significant CAD were significantly lower than for non-significant CAD (1.85±0.69 vs. 2.38±0.69; P<0.01, 1.67±0.54 vs. 2.19±0.52 mL·min-1·g-1; P<0.01, and 0.66±0.15 vs. 0.82±0.09; P<0.01, respectively). In the receiver-operating characteristic curve analysis, CFR, hMBF, and CFR ratio had areas under the curve of 0.71, 0.75, and 0.85 respectively, and the CFR ratio was significantly higher than CFR and hMBF (P<0.05). The sensitivity, specificity, and accuracy of the CFR ratio with an optimal cutoff value of 0.75 were 75%, 85%, and 82%, respectively. CONCLUSIONS Clinically, the CFR ratio in 13N-ammonia PET was more effective in detecting significant CAD.

Coronary artery disease incidentally detected by routine oncology 18F-fluorodeoxyglucose positron emission tomography

The patient was a 49-year-old man who had history of malignant melanoma and angina. Follow-up FDGPET/CT [12 hours after overnight fasting showed no findings of recurrence, except focal uptake in the left ventricular (LV) inferior wall (Figure 1A). Adenosine stress N-ammonia PET revealed abnormal coronary flow reserve (CFR) (\2.0) in all territories and \1 in the inferior wall, suggesting multivessel disease (Figure 1B). The coronary angiogram showed severe stenosis in the left anterior descending artery, intermediate stenosis in the left circumflex artery (Figure 2A), and chronic occlusion in the right coronary artery (RCA) (Figure 2B). The abnormal wall motion in the inferior LV wall on the echocardiogram was restored after coronary artery bypass grafting (CABG), which was consistent with hibernating myocardium. Focal FDG uptake in the LV inferior wall markedly diminished after CABG (Figure 3A). Re-examination of N-ammonia PET scans showed the CFR to be improved in all territories ([2.0) (Figure 3B).

Peak enhancement ratio of myocardium to aorta for identification of myocardial ischemia using dynamic myocardial computed tomography perfusion imaging

BACKGROUND This study aimed to evaluate the feasibility of peak enhancement (PE) ratio of myocardium to aorta (PER) derived from stress dynamic computed tomography myocardial perfusion imaging (CTP) for the detection of myocardial ischemia assessed by magnetic resonance (MR) imaging. METHODS Forty-four patients who underwent stress dynamic CTP and MR imaging were retrospectively evaluated. From the time-attenuation curve, myocardial PE, PER, and myocardial blood flow (MBF) were calculated on a segment-based analysis. The correlation between myocardial and aortic PE was assessed by Spearmans correlation, and the differences in myocardial PE and PER between normal and ischemic myocardium were assessed by the Mann-Whitney U-test. The diagnostic accuracies of myocardial PE, PER, and MBF for detecting myocardial ischemia were compared by receiver operating characteristic analysis. RESULTS Of 704 segments, 258 segments (37%) were diagnosed as myocardial ischemia with MR imaging. Myocardial and aortic PE were significantly correlated in both normal and ischemic segments (r=0.76 and 0.58; p<0.05, in each). The myocardial PE and PER of ischemic segments were significantly lower than those of normal segments (p<0.05, in each). Sensitivity and specificity were 61% [95% confidence interval (CI), 55-70%] and 83% (95% CI, 73-87%) for myocardial PE, 78% (67-88%) and 82% (95% CI, 70-91%) for PER, and 81% (95% CI, 73-87%) and 85% (95% CI, 79-92%) for MBF. There was a significantly larger area under the curve for PER (0.87; 95% CI, 0.84-0.90) and MBF (0.88; 95%CI, 0.85-0.91), compared to myocardial PE (0.75; 95% CI, 0.70-0.79) (p<0.05, in each). There was no significant difference in area under the curve between PER and MBF. CONCLUSIONS The semi-quantitative parameter of PER showed a high diagnostic accuracy for the detection of myocardial ischemia, comparable to that of MBF.

Radiation-Induced Cardiomyopathy Incidentally Detected on Oncology 18 F-Fluorodeoxyglucose Positron Emission Tomography

therapy (RTx) with a total dose of 60 Gy for the tumor and lymph nodes, with 40 Gy and 20 Gy using anteriorposterior and parallel-oblique fields, respectively (Figure 1A). Before RTx, 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) A 54-year-old man was referred to Ehime Prefectural Central Hospital because of dysphagia. After several examinations, he was diagnosed with unresectable stage IV esophageal cancer. The patient received chemotherapy (5-fluorouracil+cisplatin) and mediastinal radio-