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Biomedical subjects

Masanobu Namura

Publications and source records attributed to Masanobu Namura.

16 recordsLinked to original sources
PubMed2006

Development of a novel catheter preventing the outflow of debris and thrombus on percutaneous transluminal angioplasty for hemodialysis access fistulas.

If a large amount of debris or thrombus dislodges from a lesion because of dilation of the stenotic or occluded lesion in the hemodialysis access fistula when angioplasty is performed, it may move into the pulmonary artery via the central vein, resulting in pulmonary embolism. A novel sheath has been developed to prevent the outflow of debris or thrombus to the central vein. The catheter consists of a 5 F sheath introducer and a silicone balloon attached at the tip of the sheath. The silicon balloon is inflated via small inflation lumen on the shaft wall of the sheath. In the case of percutaneous transluminal angioplasty (PTA), the silicone balloon is inflated to block the blood flow by a mixture of contrast medium and physiological saline, and then dilate a stenotic or occluded lesion by PTA balloon. Next, the debris and thrombus are aspirated using the flush-lumen of this device. Finally, the silicone balloon is deflated and the dilation of the lesion is confirmed. A case of hemodialysis access fistula graft with massive thrombotic occlusion was presented. This device enabled Fogarty procedure using PTA balloon and the blood flow of the graft was completely improved and a large amount of thrombus was removed. This novel device is useful to prevent the embolic complication of the intervention for hemodialysis access fistula.

Angioplasty, Balloon↗
PubMed2006

Usefulness of fluorine-18-fluorodeoxyglucose positron emission tomography in a patient with Takayasu's arteritis associated with antiphospholipid syndrome.

A 36-year-old woman was admitted for recurring chest pain and hemoptysis. Blood pressure in the right and left arms was equal, and no murmurs or bruits were heard. Body temperature was normal on admission and remained within the normal range during the hospital stay. C-reactive protein was slightly elevated (2.3 mg/dL) and lupus anticoagulant was positive. Angiography showed no abnormality of the aorta or its branches, but the left pulmonary artery showed occlusion at the proximal portion. Computed tomography (CT) revealed segmental wall thickening of the thoracic aorta. Fluorine-18-fluorodeoxyglucose positron emission tomography (18FDG PET) showed high uptake in the proximal portion of the left pulmonary artery and in the thoracic aorta with wall thickening on CT. Based on these findings, a diagnosis of Takayasu's arteritis associated with antiphospholipid syndrome was made and high-dose steroid therapy (prednisolone 30 mg/day) was started. Two months later, the C-reactive protein level had decreased from 2.3 mg/dL to 1.1 mg/dL, and both the focal wall thickening and (18)FDG uptake of the thoracic aorta were decreased. 18FDG PET was useful for evaluating the efficacy of the steroid therapy in addition to making a diagnosis of Takayasu's arteritis associated with antiphospholipid syndrome.

Adult↗
PubMed2005

Characterization of cartilaginous tumors with 201Tl scintigraphy.

UNLABELLED: Histological diagnosis and grading of cartilaginous tumors are closely correlated with patient prognosis; consequently, they are essential elements. We attempted to clarify the characteristics of 201Tl uptake in various histological types of cartilaginous tumors and to assess its clinical value. METHODS: Twenty-two cases with histologically proven cartilaginous tumors (3 enchondromas, 15 conventional chondrosarcomas (grade I = 9, II = 5, III = 1), 3 mesenchymal chondrosarcomas, and 1 de-differentiated chondrosarcoma) were examined retrospectively. Planar 201Tl images were recorded 15 min following intravenous injection of 201Tl (111 MBq). 201Tl uptake in the tumor was evaluated visually employing a five-grade scoring system: 0 = no appreciable uptake, 1 = faint uptake above the background level, 2 = moderate uptake, 3 = intense uptake but lower than heart uptake and 4 = uptake higher than heart uptake. RESULTS: 201Tl uptake scores were 0 in 3 of 3 enchondromas, 9 of 9 grade I, and 4 of 5 grade II conventional chondrosarcomas. 201Tl uptake scores were 1 among 1 of 5 grades II and a grade III conventional chondrosarcoma. Mesenchymal chondrosarcoma and de-differentiated chondrosarcoma displayed 201Tl uptake scores of 2 or 3. CONCLUSIONS: Absence of elevated 201Tl uptake in cartilaginous tumors was indicative of enchondroma or low-grade conventional chondrosarcoma. However, in instances in which 201Tl uptake is obvious, high-grade chondrosarcoma or variant types should be considered.

Adult↗
PubMed2005

Time course of discordant BMIPP and thallium uptake after ischemia and reperfusion in a rat model.

UNLABELLED: Serial changes in fatty acid metabolism or use associated with acute ischemia and reperfusion were examined in rat hearts. METHODS: Male Wistar rats were subjected to occlusion of the left coronary artery for 20 min followed by reperfusion. After release of the occlusion, groups of animals were allowed to recover for intervals of 20 min (n = 9), 1 d (n = 9), 3 d (n = 6), 7 d (n = 6), or 30 d (n = 6). Hearts were excised 15-20 min after injection of 0.74 MBq of (125)I-15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) and 14.8 MBq of (201)Tl. One minute before resection, the left coronary artery was reoccluded and 185 MBq of (99m)Tc-sestamibi were injected to document the area at risk. Triple-tracer autoradiography was performed to assess tracer uptake. Uptake ratios of BMIPP and (201)Tl in the area at risk were calculated on the basis of the count density in the lesion divided by that in the normally perfused area. RESULTS: (201)Tl uptake did not change throughout the observation period (P = 0.25). In contrast, BMIPP uptake increased early in the acute phase (20 min and 1 d), decreased during the subacute phase (7 d), and subsequently recovered in the chronic phase (30 d). CONCLUSION: The present investigation clearly illustrated that BMIPP uptake is higher than (201)Tl uptake in the acute phase, that BMIPP uptake is lower than (201)Tl uptake in the subacute phase, and that BMIPP uptake and (201)Tl uptake are similar in the chronic phase. These results yield data essential to the precise interpretation of BMIPP images.

Animals↗
PubMed2004

Left ventricular ejection and filling rate measurement based on the automatic edge detection method of ECG-gated blood pool single-photon emission tomography.

UNLABELLED: The objective of the present investigation was to determine the feasibility of assessing left ventricular systolic ejection and diastolic filling via the automatic edge detection method employing ECG-gated blood pool single-photon emission tomography (SPET GBP) data. METHODS: Thirty-five patients, who had undergone both SPET GBP and ECG-gated equilibrium blood pool scintigraphy by the planar method (planar GBP), were enrolled in this study. Planar GBP was performed with a single-headed gamma camera. From the left anterior oblique projection, data were acquired at 24 frames/cardiac cycle with ECG-gating during the equilibrium state. SPET GBP was conducted utilizing a triple-headed gamma camera, with 60 projection views over 360 degrees by 60 sec per view, in 16 frames/cardiac cycle. In each frame, left ventricular volume was determined by automatic edge detection employing a quantitative gated SPET program. Additionally, the time-volume curve was fitted by the 4th harmonics of Fourier transform. Ejection fraction (EF, %), peak ejection rate (PER, /sec), peak filling rate (PFR, /sec) and mean filling rate during the initial one-third of diastolic time (1/3 FRm) were calculated from the fitted curve. These parameters were also calculated with planar GBP data. RESULT: Left ventricular ejection and filling parameters were calculated by SPET GBP with the automatic edge detection program for all patient data. Correlation coefficients of EF, PER, PFR and 1/3 FRm between SPET and planar GBP were 0.91 (p < 0.001), 0.82 (p < 0.001), 0.78 (p < 0.001) and 0.74 (p < 0.001), respectively. CONCLUSION: Ejection and filling rates can be calculated using SPET GBP with the edge-detection software. These parameters displayed significant correlations with those values obtained via planar GBP. Additional studies are warranted to determine the reliability of parameters with SPET GBP.

Adult↗
PubMed2004

Brown adipose tissue: evaluation with 201Tl and 99mTc-sestamibi dual-tracer SPECT.

Brown adipose tissue is one kind of adipose tissue and regulates body temperature and balance of energy via non-shivering thermogenesis. The authors present a case that strongly suggested the presence of activated brown adipose tissue in the neck, shoulders and axillary space by increased 18F-FDG uptake. 99mTc-sestamibi and 201Tl dual-tracer SPECT study showed increased 99mTc-sestamibi uptake and non-increased 201Tl uptake in the corresponding 18F-FDG uptake sites. Brown adipose tissue has dense mitochondria in the cells, which play an important role in thermogenesis. 99mTc-sestamibi uptake and retention depend on the mitochondrial activity but 201Tl uptake does not. Therefore, the activity of mitochondria in activated brown adipose tissue may explain the discrepant uptake between 99mTc-sestamibi and 201Tl.

Adipose Tissue, Brown↗
PubMed2004

Increased circulating matrix metalloproteinase-2 in patients with hypertrophic cardiomyopathy with systolic dysfunction.

BACKGROUND: Some patients with hypertrophic cardiomyopathy (HCM) develop left ventricular (LV) wall thinning associated with LV dilatation and systolic dysfunction. Recently, matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) were reported to be involved in ventricular remodeling, however, little is known about MMPs and TIMPs in patients with HCM. METHODS AND RESULTS: Enzyme-linked immunoassays were used to measure the plasma concentrations of MMP-2, MMP-3, MMP-9, TIMP-1, and TIMP-2 in 11 patients with HCM accompanied by systolic dysfunction (fractional shortening (FS) <25%, group A), 17 patients with HCM who had preserved systolic function (FS> or =25%, group B), and 50 age-matched clinically healthy control subjects (mean age: 57 years). The concentration of MMP-2 in group A was significantly higher than in group B and the control subjects (1,124 +/- 84, 792 +/- 49, 809 +/- 26 ng/ml, respectively), whereas there was no significant difference between group B and the control subjects. MMP-2 concentrations significantly increased as the New York Heart Association functional class increased in patients with HCM. TIMP-2 was also significantly higher in group A patients than in group B and the control subjects (45.3 +/- 4.7, 34.6 +/- 2.2, 33.7 +/- 1.8 ng/ml, respectively), but there was no difference between group B and control subjects. TIMP-1 was significantly higher in HCM patients than in control subjects. MMP-3 and MMP-9 concentrations did not differ among the 3 groups. Both MMP-2 and TIMP-2 correlated significantly with FS and LV dimension, negatively and positively, respectively. CONCLUSIONS: These results suggest that changes in the release and activity of MMP-2 and TIMP-2 may be associated with the mechanisms responsible for cardiac remodeling in patients with HCM.

Cardiomyopathy, Hypertrophic↗
PubMed2004

Difference in the risk factors for coronary, renal and other peripheral arteriosclerosis in heterozygous familial hypercholesterolemia.

BACKGROUND: The aim of the present study was to clarify the risk factors of several types of arteriosclerosis lesions in Japanese individuals with heterozygous familial hypercholesterolemia (FH): renal arteriosclerosis (RAS), abdominal aortic sclerosis (AOS), iliac arteriosclerosis (IAS) and coronary artery disease (CAD). METHODS AND RESULTS: Coronary angiography (CAG) and abdominal aortic angiography (AAA) were performed in 117 consecutive heterozygous FH subjects (79 men, 38 women; age 22-76). RAS (stenotic lesion or aneurysm) was observed in 39 cases (33%), predominantly in the proximal portion (74%) and both sides equally (right/left = 27/23). Most cases of RAS (64%) presented with <25% stenosis. The differences in the contributing risk factors for the progression and development of RAS, AOS, IAS and CAD in FH were then analyzed. Multiple logistic regression analyses showed independent risk factors for formation of atherosclerosis in each artery were: age alone for RAS; age and plasma low-density lipoprotein cholesterol (LDL-C) for AOS; age, LDL-C and high-density lipoprotein cholesterol (HDL-C) for IAS; and HDL-C and diabetes mellitus for CAD. CONCLUSION: In Japanese subjects with heterozygous FH, there are distinct risk factors for the development and progression of atherosclerosis in the renal, iliac, abdominal aorta, and coronary arteries.

Arteriosclerosis↗
PubMed2003

Discrepant uptake between fluorine-18 fluorodeoxy glucose and Tc-99m sestamibi in bronchioloalveolar cell carcinoma.

Several studies have shown the benefit of fluorine-18 fluorodeoxy glucose (FDG) imaging in the differentiation of solitary pulmonary nodules. The majority of malignant tumor have a higher glucose metabolic rate as compared to benign lesions. However, there is a considerable variety in glucose metabolic rate that depends on the aggressiveness and histological subtype of the tumor. Technetium-99m sestamibi (MIBI) is another tumor imaging agent for SPECT. We present a case of bronchioloalveolar cell carcinoma with a false negative finding in FDG imaging and a positive finding in MIBI imaging. This case clearly indicates that the FDG uptake and MIBI uptake might provide different information regarding characteristics of lung cancer.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed2003

Changes in myocardial oxidative metabolism after biventricular pacing as evaluated by [11C]acetate positron emission tomography.

A 70-year-old woman with dilated cardiomyopathy and recurrent severe heart failure was admitted for biventricular pacing (BVP), which was recently reported to have clinical efficacy for severe heart failure with intraventricular conduction delay. An electrocardiogram showed complete left bundle branch block, and the QRS interval was markedly prolonged at 195 msec. Echocardiogram showed marked dilatation, diffuse hypokinesis and dyssynchrony of the left ventricle, and grade III mitral valve regurgitation. The patient underwent implantation of an atriobiventricular pacemaker and three pacing leads transvenously. The QRS interval shortened to 165 msec immediately after the BVP therapy, and improvements in echocardiographic parameters were seen at 5 months after BVP therapy. Myocardial oxidative metabolism was assessed by the monoexponential clearance rate of [11C]acetate (Kmono) as measured by positron emission tomography (PET), and myocardial efficiency was assessed by the work metabolic index (WMI) at 1 and 5 months after the BVP therapy. The PET images obtained 5 months after BVP therapy showed a decrease in the clearance of [11C]acetate compared with that obtained 1 month after BVP therapy. The Kmono of the whole left ventricle decreased from 0.051 at 1 month to 0.038 min-1 at 5 months after BVP therapy, and that of the septum, anterior wall, lateral wall and posterior wall also decreased. The WMI increased from 4.2 x 10(6) to 6.8 x 10(6) mmHg. ml/m2. These results suggest that BVP improved left ventricular function without increasing myocardial oxidative metabolism, resulting in improved myocardial efficiency, and that BVP may improve the long-term prognosis of heart failure patients with ventricular dyssynchrony. [11C]acetate PET is a useful method of evaluating global and regional myocardial oxidative metabolism in patients who have undergone BVP therapy.

Acetates↗
PubMed2002

Perfusable tissue index obtained by positron emission tomography as a marker of myocardial viability in patients with ischemic ventricular dysfunction.

In areas of severe asynergy, the clinically important task is to identify functionally recoverable myocardium. Fourteen patients with asynergy were investigated by H2(15O) dynamic positron emission tomography imaging before revascularization. Regional myocardial blood flow (MBF) was determined and the water-perfusable tissue fraction (PTF) for each region of interest and the total anatomical tissue fraction (ATF) were estimated. The PTF/ATF was analyzed as the water perfusable tissue index (PTI). Asynergy was defined as segments with wall motion more than 2SD below than that of a normal population. An increase of >0.8SD in anterior wall segments with asynergy and an increase of >0.6 SD in inferior wall asynergy were defined as significant improvements of wall motion indicative of viable myocardium. Fifteen segments with wall motion abnormalities less than -2SD and 10 control segments were identified; 7 segments recovered and 8 segments did not. MBF was similar in both groups of segments before revascularization (0.78 +/- 0.27 vs 0.73 +/- 0.18 ml min-(-1) x g(-1), NS). The PTI in the recovered segments was significantly higher than that in the unimproved segments (0.734 +/- 0.058 vs 0.592 +/- 0.038, p<0.0001) and was similar to that of the control segments. After revascularization, the PTI correlated with the SD of wall motion (p<0.05, r=0.58). PTI may be a good predictor of contractile recovery after revascularization.

Aged↗