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Biomedical subjects

R Iwata

Publications and source records attributed to R Iwata.

At least 37 records · Page 2Linked to original sources
PubMed1999

FDG PET evaluation of residual masses and regrowth of abdominal lymph node metastases from colon cancer compared with CT during chemotherapy.

Fluorine-18-2-deoxy-2-fluoro-D-glucose (F-18 FDG) PET may be more suitable for follow-up after cancer treatment than other morphologic approaches, because it reflects tumor viability. A patient with abdominal lymph node metastases from colon cancer was followed by CT and F-18 FDG PET during chemotherapy. F-18 FDG PET tumor images changed in accordance with the clinical progress, whereas CT findings were relatively unchanged. This case clearly shows the utility of F-18 FDG PET for follow-up during cancer chemotherapy.

Abdominal Neoplasms↗
PubMed1998

Helical computed tomography in the diagnosis of portal vein invasion by pancreatic head carcinoma: usefulness for selecting surgical procedures and predicting the outcome.

OBJECTIVE: To evaluate the use of helical computed tomography (CT) in diagnosing portal vein (PV) invasion by pancreatic head carcinoma and its usefulness in predicting outcome. DESIGN: Validation cohort study. SETTING: Tertiary care public hospital. PATIENTS: Twenty-seven patients with carcinoma involving the pancreatic head were preoperatively studied with helical CT. All patients underwent resection. MAIN OUTCOME MEASURE: By quantifying the contact between the tumor and PV on helical CT, the relationship between them was classified into 1 of 4 types: type 1, visible fat layer between PV and the tumor; type 2, with the total PV circumference defined as 360 degrees, contact between the tumor and PV was considered to be 90 degrees or less; type 3, contact ranged between 91 degrees and 180 degrees; and type 4, contact greater than 180 degrees. Helical CT results were compared with intraoperative observation, histological findings of the resected specimen, and postoperative course. RESULTS: When helical CT showed type 3 or 4, the case was diagnosed as positive for PV invasion. Sensitivity, specificity, and overall accuracy were 83%, 100%, and 89% when compared with the intraoperative assessment, and 92%, 79%, and 85% with the histological assessment, respectively. One- and 2-year survival rates were 86% and 69% for type 1, 100% and 75% for type 2, and 33% and 12% for type 3, respectively. The survival rates of patients with types 1 and 2 were significantly higher than that of those with type 3 (P<.05). All 3 patients with type 4 died within 9 months. CONCLUSIONS: Helical CT facilitates detection of PV invasion by pancreatic head carcinoma. The extent of PV involvement reflected the outcome after pancreatectomy.

Adenocarcinoma↗
PubMed1998

Small polypoid lesions of the gallbladder: differential diagnosis and surgical indications by helical computed tomography.

OBJECTIVES: To demonstrate the helical computed tomographic (CT) features of small polypoid lesions of the gallbladder and to establish a clinical strategy based on CT findings for the treatment of such lesions. DESIGN: Validation cohort study. SETTING: Tertiary care public hospital. PATIENTS: Thirty-one patients with polypoid lesions of the gallbladder (< or = 3 cm) underwent CT followed by resection. MAIN OUTCOME MEASURE: The detectability of the lesions on both unenhanced and enhanced CT and the configuration of the lesions on enhanced CT were prospectively evaluated in comparison with the histopathological findings. RESULTS: Unenhanced CT detected 14 (45%) of the 31 lesions, whereas enhanced CT detected all of the lesions. The detection rates of the neoplastic lesions (adenoma, adenocarcinoma, and metastatic tumor) and cholesterol polyps were 81% (13/16) and 7% (1/15), respectively (P<.001). Among the 20 lesions demonstrated as pedunculated, 6 (30%) were neoplastic, whereas 10 (91%) of the 11 lesions demonstrated as sessile were neoplastic (P<.001). When a lesion was demonstrated on unenhanced CT or its shape was sessile on enhanced CT, the case was diagnosed as a neoplastic lesion. The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of the CT diagnosis of the neoplastic lesions were 88% (14/16), 87% (13/15), 88% (14/16), 87% (13/15), and 87% (27/31), respectively. CONCLUSION: Computed tomography can differentiate neoplastic and nonneoplastic small polypoid lesions of the gallbladder and reliably identify the presence of neoplastic lesions that should be resected.

Adult↗
PubMed1998

Biotransformation of digitoxigenin by cultured Strophanthus hybrid cells.

Hybrid cells between Strophanthus gratus and S. amboensis were obtained by electrofusion and confirmed to be hybrids through isozyme and RFLP analyses. Because a new and hybrid compound, 17 beta H-periplogenin beta-D-glucoside, was isolated as a biotransformation product of digitoxigenin by the hybrid cells, isomerization of 17 beta-lactone ring on S. gratus and glucosylation on S. amboensis were demonstrated simultaneously as the biotransformation abilities in the hybrid cells. Moreover, the productivity of the hybrid compound was increased by raising the sucrose concentration.

Biotransformation↗
PubMed1997

Bosentan, a novel synthetic mixed-type endothelin receptor antagonist, attenuates acute gastric mucosal lesions induced by indomethacin and HCl in the rat: role of endogenous endothelin-1.

Endothelin-1 has been reported to be responsible for gastric mucosal damage in various experimental models. We evaluated the role of endogenous endothelin-1 in the pathogenesis of gastric mucosal damage induced by indomethacin and HCl in the rat. Rats were given indomethacin (25 mg/kg) subcutaneously, and 15 min later, 0.2N HCl intragastrically. Gastric mucosal damage, gastric endogenous endothelin-1, and gastric mucosal hemodynamics were measured. The effects of bosentan, a mixed endothelin receptor antagonist, on gastric mucosal integrity and hemodynamics were assessed. Gastric endogenous endothelin-1 was significantly elevated at 20 min, gastric mucosal blood flow began to decrease significantly at 25 min, and gastric damage occupied 52.2% of the total glandular mucosa at 135 min after injection of indomethacin. Intragastric pretreatment with bosentan (5, 10, 30, and 60 mg/kg) significantly attenuated gastric damage, to 26.1%, 7.7%, 3.6%, and 1.6%, respectively, of the total glandular mucosa. Bosentan (60 mg/kg) prevented the initial decrease of blood flow and, even at 135 min, improved blood flow and hemoglobin oxygen saturation significantly. We suggest that indomethacin-induced endogenous endothelin-1 diminishes gastric mucosal blood flow and tissue oxygenation and ultimately causes gastric damage. Endogenous endothelin-1 may play an important role in the pathogenesis of the acute gastric mucosal lesions induced by indomethacin and HCl.

Animals↗
PubMed1997

Effects of haloperidol and cocaine pretreatments on brain distribution and kinetics of [11C]methamphetamine in methamphetamine sensitized dog: application of PET to drug pharmacokinetic study.

Repeated administration of methamphetamine (MAP) causes behavioral sensitization in animals. We previously reported that the maximum accumulation level of [11C]MAP in the MAP-sensitized dog brain was 1.4 times higher than that in the control. In behavioral studies, haloperidol (a dopamine D2 receptor antagonist) prevents MAP-induced behavioral sensitization, and cocaine (a dopamine reuptake blocker) has the cross-behavioral sensitization with MAP. In the present study, to elucidate the relation between the MAP-induced behavioral sensitization and the pharmacokinetics of MAP, we investigated the effects of haloperidol and cocaine pretreatments on brain regional distribution and kinetics of [11C]MAP using positron emission tomography (PET). A significant increase of [11C]MAP uptake into the sensitized dog brain was prevented by haloperidol and cocaine pretreatments. These pharmacokinetic changes were not due to the changes in the rate of MAP metabolism. These results suggest haloperidol and cocaine can change the cerebral pharmacokinetic profile of MAP in the behavioral-sensitized dog. The variations of MAP-accumulation may affect the development or expression of MAP-induced behavioral sensitization.

Animals↗
PubMed1997

Gastric mucosal injury induced by local ischemia-reperfusion in rats. Role of endogenous endothelin-1 and free radical.

We investigated the role of an endogenous vasoconstrictor peptide endothelin-1 (ET-1) and free radicals in local gastric ischemia-reperfusion injury in rats. Local gastric ischemia was induced by clamping the left gastric artery for 15 min and reperfusion was done for 10-30 min in the presence of 150 mM exogenous HCl intragastrically. Local gastric ischemia and reperfusion resulted in significant macroscopic and microscopic gastric mucosal damage together with elevation of gastric tissue ET-1 concentration. Gastric tissue ET-1 was found to increase after 15 min of ischemia alone and also with 30 min of reperfusion. A novel nonpeptide endothelin receptor antagonist, bosentan, or a combination of radical scavengers (superoxide dismutase, catalase, and deferoxamine) both attenuated gastric mucosal injury. However, the greater protection observed with bosentan than with radical scavengers might reflect a preferential role of endothelin-1 in this type of injury.

Animals↗
PubMed1997

Pheochromocytoma growing exophytically from the right adrenal gland and invaginating into the liver.

A 5-cm pheochromocytoma located in segment 7 of the liver was found incidentally in a 45-year-old man with mild diabetes mellitus and hypertension, and resected. The tumor was demonstrated by computed tomography and magnetic resonance imaging to have completely invaginated itself into the liver and to be receiving blood from a dilated right hepatic artery alone. Surgery revealed the hepatic mass to be tightly adherent to the right adrenal gland. The histopathologic diagnosis was pheochromocytoma growing exophytically from the right adrenal gland. There was no association with multiple endocrine neoplasia type 1 and type 2. A postoperative 131I metaiodobenzylguanidine scan revealed no accumulation, and the patient is currently doing well without recurrence or hypertension one year after the operation. A pheochromocytoma deeply invaginating into the liver should be considered in the differential diagnosis of primary hypervascular hepatic tumors.

Adrenal Gland Neoplasms↗
PubMed1997

Analysis of biliary drainage in the caudate lobe of the liver: comparison of three-dimensional CT cholangiography and rotating cine cholangiography.

PURPOSE: To evaluate the bile duct anatomy of the caudate lobe without disease involvement with use of three-dimensional (3D) cholangiography and to compare the usefulness of this technique with that of rotating cine cholangiography. MATERIALS AND METHODS: In 12 patients with obstructive jaundice but without lesions at the hepatic hilum who underwent percutaneous transhepatic biliary drainage, serial examination was performed with cine cholangiography and helical computed tomography (CT). From helical CT scans, 3D cholangiograms were reconstructed. Cine and 3D cholangiograms were evaluated and compared simultaneously. RESULTS: In the 12 patients, 40 branches of the caudate lobe were detected with 3D cholangiography (mean, 3.3 branches per patient), while 31 were detected with cine cholangiography (mean, 2.6 branches per patient). The difference in detection rate was significant (P < .01). Nine (23%) of 40 branches were detected with 3D cholangiography alone, and all 31 branches detected with cine cholangiography were also detected with 3D cholangiography. CONCLUSION: 3D cholangiography was superior to cine cholangiography in assessment of bile duct anatomy of the caudate lobe of the liver because 3D cholangiography eliminated the overlap of different branches of the bile duct.

Aged↗
PubMed1997

Hepatic tumor invasion of bile ducts: wedge-shaped sign on MR images.

PURPOSE: To clarify the diagnostic importance of wedge-shaped areas of increased signal intensity that surround liver tumors on T1-weighted magnetic resonance (MR) images. MATERIALS AND METHODS: In five patients with hepatic tumors, T1-weighted MR images that demonstrated wedge-shaped areas of increased signal intensity in the liver were reviewed; findings were compared with those at surgical and histologic examinations. RESULTS: MR images showed localized intrahepatic bile duct dilatation lateral (three patients) and medial (two patients) to liver tumors within the wedge-shaped areas. At histopathologic examination, intraductal tumor growth was seen in local bile ducts in the same areas in five patients, and lipofuscin deposits were seen in the cytoplasm of atrophic hepatocytes in three patients. CONCLUSION: On T1-weighted images, wedge-shaped areas of increased signal intensity associated with liver tumors indicate intraductal tumor extension in intrahepatic bile ducts. T1 shortening is possibly caused by lipofuscin deposits in atrophic hepatocytes.

Adult↗
PubMed1997

Assessment of cancer recurrence in residual tumors after fractionated radiotherapy: a comparison of fluorodeoxyglucose, L-methionine and thymidine.

UNLABELLED: This study evaluates the midterm follow-up of tumor and normal tissue uptake of deoxyglucose, thymidine and methionine after fractionated radiotherapy to assess cancer recurrence in residual tumors. METHODS: AH109A tumor-burdened rats were treated with one to eight doses of 5Gy 60Co radiation. Tissue distribution study with 18F-FDG, 3H-thymidine and 14C-methionine, double-tracer autoradiography with 18F-FDG and 14C-methionine, and single-tracer autoradiography with 14C-labeled deoxyglucose, thymidine and methionine were performed 6 days after the end of therapy. RESULTS: Dose response study shows a significant decrease of tumor uptake of all tracers after two and more doses, even in the case of later recurrence. Whereas 3H-Thd and 14C-Met tumor uptake was similar to that of normal muscle, 18F-FDG tumor uptake remains higher than that of muscle, even in the case of complete tumor cure. The irradiated muscle shows a higher 18F-FDG uptake than the nonirradiated muscle. Autoradiography after eight doses (100% tumor cure) reveals elevated 14C-DG tumor uptake to be ascribable to nonmalignant cellular elements, in particular to a macrophage layer at the rim of necrotic areas. Autoradiography after four and six doses (33% and 57% tumor cure) shows the highest methionine and thymidine uptake in viable cancer cells, whereas deoxyglucose uptake did not differ between viable cancer cells and macrophages. CONCLUSION: To detect and differentiate viable cancer cells in a residual tumor mass after radiotherapy, PET using 11C-methionine or 11C-thymidine may have some advantages over 18F-FDG, especially if the residual tumor includes larger areas of necrosis.

Animals↗
PubMed1997

[Three-dimensional positron emission tomography imaging system and its application for medical use].

Current positron emission tomography is capable for three dimensional data acquisition and reconstruction (3D PET). The main advantage of 3D PET is its detectability for lower tracer concentrations. The images by a 3D PET have better signal to noise ratios compared to those by conventional 2D PET. This point is especially important for the studies of distributions of ligands for neuroreceptors such as F-18 FDOPA and C-11 YM-01951, since these ligands show low accumulation in brain. Reduction of scanning time is useful as well for patients are permitting extended scanning periods

Carbon Radioisotopes↗
PubMed1997

[Staging of pancreatic ductal adenocarcinoma using dynamic MR imaging].

Single breath-hold gradient echo images were obtained before and immediately after bolus intravenous administration of Gd-DTPA (dynamic MR imaging) in the study of the pancreas. Of 37 patients with pathologically proved pancreatic ductal adenocarcinoma, seventeen patients who underwent both dynamic MR imaging studies and curative surgery were included in this study. Correlations between histologic findings in the resected specimens and MR images were analyzed as to tumor extension and staging according to the General Rules for the Study of Pancreatic Cancer (4th Edition) published by the Japan Pancreas Society. In comparison with conventional MR images, dynamic MR imaging improved the detectability of pancreatic carcinoma and delineation of the vasculature by clarifying the margin of the tumor and the vessels. Nonenhanced T1-weighted imaging is the best sequence to estimate peripancreatic tumor extension, because the contrast between the tumor and peripancreatic fat deteriorates with the use of contrast material. There is a tendency to overestimate vascular invasion on MR images, the reason for which is considered to be the contractive nature of fibrotic change induced by pancreatic carcinoma. The diagnostic efficacy of lymph node metastasis remains insufficient on MR images because some cases show no enlargement of lymph nodes in spite of the existence of pathological metastasis. Our results suggest that dynamic MR imaging has the advantage of improving the conspicuity of the tumor and the vasculature.

Adult↗
PubMed1996

Positron emission tomography study of the alterations in brain distribution of [11C]methamphetamine in methamphetamine-sensitized dog.

We newly prepared a MAP-sensitized dog by repeated MAP treatment and studied the brain distribution of [11C]MAP in the normal and the MAP-sensitized dog using PET. The maximal level of accumulation of [11C]MAP in the sensitized dog brain was 1.4 times higher than that in the control. No difference was found in the metabolism of MAP between the two conditions. The significant increase of [11C]MAP in the MAP-sensitized brain indicates that subchronic MAP administration causes some functional change in the uptake site of MAP. The pharmacokinetic change may, in part, account for behavioral sensitization.

Animals↗
PubMed1996

Biological evaluation of 5-methyl-branched-chain omega-[18F]fluorofatty acid: a potential myocardial imaging tracer for positron emission tomography.

5-Methyl-17-[18F]fluoroheptadecanoic acid (5-MFHA) has been proposed as a new myocardial imaging tracer for positron emission tomography (PET), containing methyl-branching at the odd-numbered position, except the 3-position. To compare the site of methyl-branching of fatty acids on the contribution to myocardial imaging, the biological evaluation of 5-MFHA-using accumulation studies, metabolic studies, and PET studies of the heart muscle-was investigated. In the comparative biodistribution studies for 16-[18F]fluoropalmitic acid (FPA), 3-methyl-17-[18F]fluoroheptadecanoic acid (3-MFHA) and 5-MFHA, the initial myocardial uptake of 5-MFHA (2.64 [%dose/g tissue]) was relatively high between those of FPA and 3-MFHA (3.45 and 1.58, respectively), and the washout from myocardium of 5-MFHA was midway between those of FPA and 3-MFHA. In the lipid analysis studies, 5-MFHA was mainly metabolized to triglycerides in the myocardium, and its metabolic pattern was similar to that of straight-chain fatty acids (FPA). In the PET studies using 5-MFHA in canines, good myocardial images were obtained for up to 30 min after injection.

Animals↗
PubMed1996

Brain 6-[18F]fluorodopa metabolism in early and late onset of Parkinson's disease studied by positron emission tomography.

We measured 6-[18F]fluorodopa (FDOPA) uptake in the caudate nucleus and the putamen of 20 patients with early and late onset of Parkinson's disease (EOPD and LOPD) and 20 normal control subjects using positron emission tomography. The mean influx rate constant values (Ki) were significantly reduced in the caudate nucleus and the putamen of the patients with EOPD and LOPD compared with age-matched control groups (p < 0.01), respectively. There were significant negative correlations between Ki values in the caudate nucleus (r = -0.67, p = 0.0024) and the putamen (r = -0.67, p = 0.0014), and duration of disease in the LOPD group compared with the EOPD group. Similar negative relationships between Ki values and clinical stages by Hoehn and Yahr and degrees of main clinical symptoms (bradykinesia, tremor and rigidity) were more markedly seen in the LOPD group than in the EOPD group. The present results suggest that the function of presynaptic dopaminergic terminals correlates well with clinical disease severity and degrees of main symptoms in the LOPD group, but not in the EOPD group. We speculate that compensatory up-regulatory function in the postsynaptic dopaminergic receptors may modify disease severity and the degrees of main clinical symptoms of EOPD.

Adult↗