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Muneo Ohba

Publications and source records attributed to Muneo Ohba.

6 recordsLinked to original sources
PubMed2006

A catheter-based intravascular radiation detector of vulnerable plaques.

UNLABELLED: Detection of vulnerable plaques before rupture is important in preventing acute coronary events such as myocardial infarction. Although therapeutic strategies such as percutaneous transluminal coronary angioplasty appear to prevent coronary occlusion and consequently may lead to improved prognosis in these patients, a method of detecting vulnerable plaques has not been established. A nuclear method that uses an intravascular radiation detector (IVRD) with the plaque-avid tracer (18)F-FDG is one of the most promising methods. The catheter-based IVRD consists of a catheter probe (a scintillator and flexible optic fibers), photomultipliers, a controller, and an automatic pullback unit and personal computer. A phantom study demonstrated that this detector was highly sensitive to (18)F and enabled the detection of (18)F point sources. However, details of the detection system in vivo remain unclear. METHODS: To evaluate vulnerable plaques in vivo, we investigated a canine femoral artery and coronary artery using this detector system. Our goal was to estimate the ability of this device to navigate through these arteries and to detect (18)F point sources fixed on their adventitia. RESULTS: In the study using a canine femoral artery, the IVRD could detect the point sources with good repeatability. In the study using an open-chest canine model, the catheter probe could easily be advanced into the left descending coronary artery, and the IVRD could detect target sources attached externally to the coronary artery (7- to 15-mm intervals) with good resolution. CONCLUSION: This newly developed catheter-based IVRD was able to detect, with good resolution, the slight radioactivity from (18)F point sources attached to the femoral artery and the coronary adventitia. These results show that catheter-based detection of coronary vulnerable plaques may be feasible.

Animals↗
PubMed2005

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 by 15O-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 thallium-201 (201T1) 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 ml/g/min, respectively; p < 0.01, for both) and in ischemic segments (1.3 +/- 0.4 and 1.5 +/- 0.4 ml/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.

Adenosine Triphosphate↗
PubMed2005

Cardiac functional analysis with multi-detector row CT and segmental reconstruction algorithm: comparison with echocardiography, SPECT, and MR imaging.

PURPOSE: To evaluate accuracy of cardiac functional analysis with multi-detector row computed tomography (CT) and segmental reconstruction algorithm over a range of heart rates. MATERIALS AND METHODS: Institutional review board approval was obtained. Informed consent was not required. Multi-detector row CT (500-msec rotation time, 8 x 1-mm detector collimation) and magnetic resonance (MR) imaging were performed in 50 patients (28 men, 22 women; age range, 46-84 years; mean age, 67 years). Two-dimensional echocardiography was performed in 41 patients, and electrocardiographically (ECG)-gated single photon emission computed tomography (SPECT) was performed in 27. End-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), and left ventricular (LV) mass were estimated with multi-detector row CT and compared with values estimated with MR imaging, which served as the reference standard. Additionally, EF values estimated with multi-detector row CT, echocardiography, and SPECT were compared with those estimated with MR imaging. Systemic error and degree of agreement of global functional parameters measured with MR imaging and other modalities were assessed. In a second analysis, linear regression analysis was added. RESULTS: EF estimated with multi-detector row CT agreed and correlated well with EF estimated with MR imaging (bias +/- standard deviation, -1.2% +/- 4.6; r = 0.96). Agreement and correlation were similar for EDV (-0.35 mL +/- 15.2; r = 0.97), ESV (1.1 mL +/- 8.6; r = 0.99), and LV mass (2.5 mL +/- 15.0; r = 0.96). Standard deviation of EF difference between multi-detector row CT and MR imaging was significantly less than that between echocardiography and MR imaging (P < .001) or that between SPECT and MR imaging (P < .001). CONCLUSION: Various LV functional parameters were measured with multi-detector row CT with a segmental approach, and measurements correlated and agreed with those obtained with MR imaging. Moreover, functional analysis with multi-detector row CT was more accurate than that with two-dimensional echocardiography or ECG-gated SPECT.

Aged↗
PubMed2005

Effectiveness of delayed enhanced MRI for identification of cardiac sarcoidosis: comparison with radionuclide imaging.

OBJECTIVE: The purpose of this study was to evaluate the usefulness of delayed enhanced MRI for detecting cardiac sarcoidosis and to clarify the relationship between the findings of MRI and those of radionuclide imaging. CONCLUSION: Delayed enhanced MRI is considered a useful method for the early identification of cardiac sarcoidosis. Delayed hyperenhancement is frequently associated with a reduction of regional wall motion and thallium-201 perfusion defects.

Cardiomyopathies↗
PubMed2004

Myocardial metabolism of 123I-BMIPP under low-dose dobutamine infusion: implications for clinical SPECT imaging of ischemic heart disease.

PURPOSE: 123I-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (123I-BMIPP) is a fatty acid analog for single-photon emission computed tomography (SPECT) imaging that is mainly stored in the triglyceride pool. Low-dose dobutamine infusion has been reported to improve BMIPP uptake in the stunned myocardium, but the mechanism underlying this effect remains unclear. The purpose of this study was therefore to investigate the myocardial metabolism of 123I-BMIPP in the stunned myocardium under low-dose dobutamine infusion, and to elucidate the mechanism by which dobutamine improves BMIPP uptake. METHODS: Using open-chest dogs, stunned myocardium was induced by occlusion of the left anterior descending artery (LAD) for 30 min, with subsequent reperfusion (ischemia group, n=6). After direct injection of BMIPP into the LAD, myocardial extraction and retention were examined and metabolites evaluated (using high-performance liquid chromatography) during dobutamine infusion. The results in the ischemia group were compared with findings obtained in a control group under dobutamine infusion (n=6). RESULTS: Dobutamine infusion significantly increased both the rapid extraction (within 30 s) of BMIPP into the myocardium (control vs ischemia group: 48+/-19% vs 66+/-14%, p<0.05) and its subsequent retention (73+/-13% vs 85+/-8%, p<0.05). The metabolites from the myocardium consisted of back diffusion of nonmetabolized BMIPP, the alpha-oxidation metabolite, intermediate metabolites, and the full-oxidation metabolite. Among these metabolites, the full-oxidation metabolite decreased significantly (from 34.0+/-20.0% to 15.8+/-9.3%, p<0.05) in the stunned regions, though back diffusion of nonmetabolized BMIPP increased (from 51.3+/-21.9% to 71.3+/-10.1%, p<0.05). CONCLUSION: These results indicate that increased uptake of BMIPP in stunned myocardium is mainly due to decreased beta-oxidation in tissue and increased shunt retention of BMIPP in the triglyceride pool, and thereby provide further insight into the pathophysiology of stunned myocardium.

Animals↗