Ryohei Hosokawa

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.

Multimodality Imaging of Cardiac Sarcoidosis Before and After Steroid Therapy

A 65-year-old woman was referred to our hospital because of chest pain. Right ventricular bundle-block was noted on the ECG. Angiotensin-converting enzyme level was elevated (33.2 IU/L). Delayed-enhanced magnetic resonance imaging (MRI) using an inversion-recovery segmented gradient echo sequence performed 15 minutes after gadolinium contrast injection (0.15 mmol/kg of gadodiamide) disclosed hyperenhancement, mainly in the outer layer of the septal, inferior, and anterolateral walls (Figure 1A). Cine MRI revealed wall motion abnormalities in septal and inferior walls (Figure 1B and 1C; Movie I). Left ventricular ejection fraction was 44%. Resting 201thallium single photon emission tomography revealed perfusion defects in these walls (Figure 1D). Positron emission tomography with 18fluorodeoxyglucose (FDG PET) imaging performed in a fasting condition …

Noninvasive Assessment of Myocardial Viability by Positron Emission Tomography With 11C Acetate in Patients With Old Myocardial Infarction Usefulness of Low-Dose Dobutamine Infusion

BACKGROUND When patients with severely depressed left ventricular function are treated, it is crucial to know in advance how much functional recovery is expected from coronary revascularization. METHODS AND RESULTS We compared the results of 11C acetate positron emission tomography (PET) with dobutamine infusion with changes in regional wall motion evaluated by left ventriculography in 28 patients with old Q-wave anterior myocardial infarctions. Dysfunctional but viable myocardium (group A, n = 13) was separated from nonviable myocardium (group B, n = 15) by echocardiographic assessments of regional wall motion before and after successful coronary revascularization. 11C acetate PET was performed to characterize normalized myocardial blood flow and oxidative metabolism (the clearance rate constant, k mono). While the baseline k monos of the infarct areas of the two groups were different with overlap, the responses to dobutamine infusion were directionally different. In addition, relative perfusion by 11C acetate PET could predict recovery of left ventricular function as well as or better than dobutamine 11C acetate kinetics. The extent of the increase in k monos of the infarct area with dobutamine infusion correlated well (P < .01) with the degree of the increase in the percentage of systolic segment shortening in the infarct area (left ventriculography) after coronary revascularization. CONCLUSIONS 11C acetate PET with dobutamine infusion can predict not only the reversibility of dysfunctioning myocardium after coronary revascularization but also the extent of improvement of regional wall motion in patients with old Q-wave infarction.

Evaluation of myocardial infarct size in rat heart by pinhole SPECT.

BackgroundHigh-resolution single photon emission computed tomography (SPECT) with a pinhole collimator is a new method for evaluating the regional properties of radiopharmaceuticals in small laboratory animals in vivo. Although several reports of normal images of rat taken by this new technique are available, there are as yet few reports on its use in disease models, such as myocardial infarction. In this study, we clearly visualized myocardial flow in the rat heart with myocardial infarction using this system, and evaluated the relationship between SPECT images and histologic analysis.Methods and ResultsFor visualization of myocardial flow in rat heart, 201Tl images were taken just before and 24 days after left coronary artery ligation. The images were taken using a 4-head SPECT scanner with pinhole collimators. The percent infarct size on 201Tl-SPECT imaging (%SI) and the defect score were then assessed and compared with the percent infarct size on histologic analysis (%HI). Both the %SI and defect score correlated well with %HI (r=0.97 and 0.74, respectively).ConclusionSerial SPECT imaging using pinhole collimators permits estimates of myocardial flow even in small laboratory animals noninvasively in vivo.

Comparative study of201Tl-scintigraphic image and myocardial pathologic findings in patients with dilated cardiomyopathy

The objective of the present study was to characterize the production of201Tl myocardial perfusion defects, the relation between the201Tl multiple small defects and the myocardial damage indicated by myocardial fibrosis shown histopathologically in patients with dilated cardiomyopathy (DCM).Rest201Tl scintigraphy was performed in thirty-seven patients with myocardial tissue fibrosis by endomyocardial biopsy, and without stenosis of the coronary artery.201Tl myocardial SPECT images were visually classified into 4 grades according to the severity of inhomogeneous perfusion defects (IPD), 0: none, 1: slight, 2: moderate, 3: severe.201Tl uptake, defect regions (DR), and coefficient of variation % (CV%) were also quantified by Bull’s eye quantification in nineteen patients. During cardiac catheterization, three biopsy specimens were obtained from the lateral wall to the apical region of the left ventricle and the amount of fibrosis was assessed by means of light microscopic morphometry. The myocardial fibrosis was also classified into 4 grades by a pointcounting method. Autopsy study was also assessed in six patients.201Tl perfusion defects were observed in 35 (94.6%) patients, of whom 29 (78.4%) showed inhomogeneous perfusion defects. Twenty-four (64.9%) showed Stage 0 and 1201Tl findings, and 21 (62.2%) had myocardial fibrosis in stage 1. Clinically, the correlation between the grades of the IPD, %201Tl uptake, DR and CV% of myocardial uptake, which were calculated semiquantitatively by Bull’s eye image, and the histological grades of fibrosis were also good (IPD vs. fibrosis: r = 0.7014; %201Tl uptake vs. fibrosis: r = −0.6542; DR vs. fibrosis: r = 0.7027; CV% vs. fibrosis: r = 0.6985). The201Tl SPECT findings were in close agreement with the severity of myocardial fibrosis confirmed by autopsy, but the grading of the IPD was not related to the ejection fraction or left ventricular diameter.It showed a higher rate of inhomogeneous201Tl myocardial perfusion defects (78.4%) in patients with DCM. This result may contribute to the clinical evaluation of DCM or differentiation from other diseases. Furthermore, the grading of201Tl inhomogeneous perfusion defects related to the myocardial fibrosis of left ventricular myocardium may contribute to speculation of the myocardial degenerative stage in clinical settings.

Evaluation of coronary blood flow reserve by13N-NH3 positron emission computed tomography (PET) with dipyridamole in the treatment of hypertension with the ACE inhibitor (Cilazapril)

PurposeThe purpose of this study was to evaluate the effect of treatment with an angiotensin-converting enzyme (ACE) inhibitor (Cilazapril) for early hypertensive patients in terms of coronary blood flow reserve evaluated by13NH3-positron emission tomography (PET).MethodsBefore and after 12 weeks of ACE inhibitor treatment,13NH3-PET with dipyridamole provocation test was performed, and definite myocardial perfusion and coronary flow reserve (CFR) were calculated.ResultsCompared to our normal subjects previously reported (2.61±0.74), average coronary flow reserve was decreased (1.70±0.64 in hypertensive patients), and improved after treatment (1.77±0.52), but not significantly. Of 12 patients, five (42%) showed improved coronary flow reserve from 1.34 to 1.99 without a significant change in the resting flow. Only one patient (8%) showed deterioration after the ACE inhibitor treatment. The coronary vascular resistance (CVR) after ACE inhibitor treatment of the patients with CFR<2.0 decreased significantly compared with those with CFR≧2.0 (p<0.03).ConclusionsThese results indicate that hypertensive patients at the early stage show decreased coronary flow reserve despite having normal resting flow. Treatment with an ACE inhibitor (Cilazapril) for 12 weeks improved coronary flow reserve in 42% of our patients. The CVR of the patients with CFR<2.0 showed improvement compared to those with CFR≧2.0.This result indicates that an ACE inhibitor (e.g., Cilazapril) should be one of the choices for improving CFR if hypertensive patients in early stage show signs of ischemia or diastolic dysfunction, which may be one of the sequels of reserve restriction.

Thoracoabdominal-Aortoiliac MDCT Angiography Using Reduced Dose of Contrast Material

OBJECTIVE The objective of our study was to compare the image quality of MDCT angiography studies obtained by injection of low doses of contrast medium with saline flush versus conventional doses of contrast medium. MATERIALS AND METHODS Seventy-one patients with pre- or postoperative aortic aneurysms underwent MDCT angiography throughout the thoracoabdominal-aortoiliac system using an 8-MDCT scanner. In 37 patients, 100 mL of contrast medium was injected at a flow rate of 3.0 mL/s (hereafter referred to as the 100-mL group). In 34 patients, 50 mL of contrast medium followed by a 20-mL saline flush was injected at a flow rate of 2.5 mL/s (the 50-mL group). For each group, quantitative analysis involved calculating the mean aortoiliac enhancement, plateau deviation, and contrast enhancement in the pulmonary trunk and superior vena cava (SVC). Qualitative analysis involved assessing the 3D postprocessing images. RESULTS Significant differences between the groups in mean aortoiliac enhancement (100-mL group vs 50-mL group, 337 +/- 6 H vs 319 +/- 5 H, p < 0.0001) and mean plateau deviation (51 +/- 4 H vs 58 +/- 4 H, p < 0.0001) were found. However, adequate arterial enhancement (>or= 200 H) was observed in 31 of 34 patients in the 50-mL group and uniform aortoiliac enhancement (< 50 H) was seen in 26 patients. Visual analysis showed no difference in contrast material magnitude and homogeneity between the groups. Furthermore, in the 50-mL group, the thoracic aorta was more clearly visualized because of a reduction in the opacity of the main pulmonary artery and SVC. CONCLUSION In our experience, administration of 50 mL of contrast medium followed by a 20-mL saline flush produces thoracoabdominal-aortoiliac MDCT angiographic examinations of effective quality in most cases.

Basic kinetics of 15-(p-iodophenyl)-3-R, S-methylpentadecanoic acid (BMIPP) in canine myocardium

BMIPP is a radioiodinated fatty acid analogue used for myocardial single photon emission CT (SPECT) imaging based on high cardiac fatty acid metabolism. In normal dogs, 74% of the injected BMIPP was instantly extracted and was then retained in 65.3%. The washout of the retained radioactivity was low, and most of the washout was alpha- and beta-oxidation metabolites. ATP concentration plays an important role in the myocardial uptake and retention of BMIPP. The ATP-dependent BMIPP uptake at the TG pool was strongly regulated by etomoxir with modifying mitochondrial β-oxidation and subsequent ATP production. Thus, myocardial viability was reflected on the BMIPP uptake in acute ischemia. In spite of in-significant changes in early extraction and retention, BMIPP back diffusion (r=−0.92) and full-oxidation metabolite (r=0.78) were correlated with the severity of ischemia. Mismatched region of BMIPP with flow (Tl-201) showed decreased metabolic enzymes such as citrate synthase and 3-hydroxyacyl-CoA dehydrogenase. These data suggest that BMIPP would be feasible for detecting cellular energy state from lipid metabolism.

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.

Effect on treadmill exercise capacity, myocardial ischemia, and left ventricular function as a result of repeated whole-body periodic acceleration with heparin pretreatment in patients with angina pectoris and mild left ventricular dysfunction.

Whole-body periodic acceleration (WBPA) has been developed as a passive exercise device capable of improving endothelial function by applying pulsatile shear stress to vascular endothelium. We hypothesized that treatment with WBPA improves exercise capacity, myocardial ischemia, and left ventricular (LV) function because of increased coronary and peripheral vasodilatory reserves in patients with angina. Twenty-six patients with angina who were not indicated for percutaneous coronary intervention and/or coronary artery bypass grafting were randomly assigned to remain sedentary (sedentary group) or undergo 20 sessions of WBPA with the motion platform for 4 weeks (WBPA group) in addition to conventional medical treatment. WBPA was applied at 2 to 3 Hz and approximately ±2.2 m/s² for 45 minutes. We repeated the symptom-limited treadmill exercise test and adenosine sestamibi myocardial scintigraphy. In the WBPA group, the exercise time until 0.1-mV ST-segment depression increased by 53% (p <0.01) and the double product at 0.1-mV ST-segment depression by 23% (p <0.001). Severity score of myocardial scintigraphy during adenosine infusion decreased from 20 ± 10 to 14 ± 8 (p <0.001) and severity score at rest also decreased from 13 ± 10 to 8 ± 10 (p <0.01). On scintigraphic images at rest, LV end-diastolic volume index decreased by 18% (p <0.01) with an augmentation of LV ejection fraction from 50 ± 16% to 55 ± 16% (p <0.01). In contrast, all studied parameters remained unchanged in the sedentary group. In conclusion, treatment with WBPA for patients with angina ameliorates exercise capacity, myocardial ischemia, and LV function.