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Biomedical subjects

Kuni Ohtomo

Publications and source records attributed to Kuni Ohtomo.

At least 55 records · Page 3Linked to original sources
PubMed2005

Measurement of skeletal muscle glucose utilization by dynamic 18F-FDG PET without arterial blood sampling.

OBJECTIVE: Skeletal muscle glucose utilization (SMGU) can be measured by 18F-FDG PET to characterize insulin resistance. The aim of this study was to determine whether femoral muscle SMGU can be measured without arterial blood sampling by sequential PET imaging of the thoracic and femoral regions. METHODS: Ten patients with possible insulin resistance underwent dynamic 18F-FDG PET of the femoral region during hyperinsulinaemic euglycaemic clamping (group A), and femoral muscle SMGU was calculated using PET data of various time periods and measured arterial input. SMGU was also calculated using venous plasma activity, instead of arterial activity, as input during the late phase. Another five patients underwent sequential PET of the thoracic and femoral regions after single tracer injection (group B). The input function was estimated from aorta activity on thoracic images during the early phase and from venous activity during the late phase, and SMGU with this estimated input was compared with that with measured arterial input. RESULTS: In group A, exclusion of early dynamic PET data from analysis had essentially no effect on the calculated SMGU, and partial substitution of venous activity for arterial activity only marginally changed the estimates. The difference between SMGUs with measured and estimated inputs was minimal in group B. CONCLUSION: Femoral muscle SMGU can be calculated without femoral imaging early after tracer injection, and the input function can be assessed using data of thoracic imaging and venous blood samples. These results support the validity of measuring femoral muscle SMGU without arterial sampling, simultaneously with measurement of myocardial glucose utilization.

Adult↗
PubMed2005

The experience of concurrent chemoradiation for Japanese patients with superficial esophageal squamous cell carcinoma: a retrospective study.

PURPOSE: To evaluate the treatment outcome of concurrent chemoradiation therapy (cCRT) for 13 clinically confirmed T1 esophageal cancer patients. METHODS: Between June 2000 and February 2004, patients with T1 esophageal cancer (tumor invading lamina propria or submucosa) received cCRT (50.4 Gy; CDDP: 75 mg/m2, day 1, bolus; 5-FU: 1000 mg/m2, days 1 to 4, continuous) (n = 13, T1 group). This treatment regimen was compared with the following 2 other groups treated during the same period: one was treated with radiation therapy alone for T1 disease (n = 5, RT-alone group); and the other group of patients consisted of those with T2 disease (tumor invading muscularis propria) who received the same cCRT regimen as the first T1 group (n = 9, T2 group). RESULTS: The overall survival rates at 1 and 3 years were in the T1 group, 75% and 75%; in the T2 group, 75% and 45% (P =0.2890); and in the RT-alone group, 60% and 40% (P = 0.2978). No treatment-related mortalities occurred in the T1 and RT-alone groups, but one patient in the T2 group died of radiation-induced pneumonitis. CONCLUSIONS: Although this study was not randomized, the results showed that cCRT is a safe and effective method for treating patients with superficial esophageal cancer.

Aged↗
PubMed2005

Pancreas duct abnormalities in patients with ulcerative colitis: a magnetic resonance pancreatography study.

BACKGROUND: The presumed etiology and prevalence of pancreatic abnormalities in patients with ulcerative colitis (UC) have been controversial. We conducted a controlled (cross-sectional) study of patients with UC compared with non-UC controls to determine the prevalence of pancreatic duct abnormalities in patients with UC and to determine if these are specific to UC using magnetic resonance cholangiopancreatography. METHODS: Magnetic resonance cholangiopancreatography was performed on 79 unselected patients with UC and 45 non-UC controls, without a history of pancreatitis attack, between February 2000 and May 2003. RESULTS: Among patients with UC, the prevalence of pancreatic duct abnormalities was 16.4% (95% confidence interval, 8.3%-24.6%): coexisting dilatation and narrowing of the main pancreatic duct were found in 5; diffuse narrowing of pancreatic ducts in 5; and dilatation of pancreatic ductal branches in 3. These abnormalities were compatible with chronic pancreatitis. Among the controls, no pancreatic duct abnormality was found. CONCLUSIONS: Changes in the pancreatic duct were found in approximately one-sixth of patients with UC, none of whom had a history of overt pancreatitis. These pancreatic duct abnormalities are likely to be specific to patients with UC.

Adolescent↗
PubMed2005

Complications of percutaneous radiofrequency ablation for hepato-cellular carcinoma: imaging spectrum and management.

Percutaneous radiofrequency (RF) ablation is feasible for the treatment of unresectable hepatocellular carcinoma, and experience at the authors' institution during 5 years indicates that percutaneous RF ablation can be performed safely in most cases. However, early or late complications related to mechanical or thermal damage may be observed at follow-up examination. Complications may be classified in three groups: vascular (eg, portal vein thrombosis, hepatic vein thrombosis with partial hepatic congestion, hepatic infarction, and subcapsular hematoma), biliary (eg, bile duct stenosis and biloma, abscess, and hemobilia), and extrahepatic (eg, injury to the gastrointestinal tract, injury to the gallbladder, pneumothorax and hemothorax, and tumor seeding). Most complications can be managed with conservative treatment, percutaneous or endoscopic drainage, or surgical repair. Because an early and accurate diagnosis is necessary for proper management, radiologists should be familiar with the imaging features of each type of complication.

Aged↗
PubMed2005

Gamma knife surgery for hemangioblastomas.

OBJECT: The authors reviewed their 14-year experience using stereotactic radiosurgery for the treatment of hemangioblastomas and define the role and the proper strategy for radiosurgery of this condition. METHODS: This is a retrospective study of 38 hemangioblastomas in 13 patients. Seven patients had von Hippel-Lindau disease. All patients have undergone at least one follow-up visit. The median and mean tumor volumes were 0.23 cm3 and 0.72 cm3 respectively (range 0.004::4.84 cm3). Twenty-eight tumors received 20 Gy to the margin, and the remainder received 18 Gy. The median clinical follow-up period was 36 months (range 3-159 months). No patient died. The survival rate was 84.6% (11 of 13 patients). The actuarial 5- and 10-year survival rates were both 80.8%. The median radiological follow-up period was 35 months (range 7-147 months). Only one tumor increased in volume 24 months after treatment in association with an intratumoral hemorrhage. The tumor control rate was 97.4% (37 of 38 tumors). Actuarial 5- and 10-year control rates were both 96.2%. New lesions and/or those increasing in size outside the irradiated area were discovered in five patients (38.5%). Nine tumors revealed peritumoral contrast enhancement which was seen more frequently in larger tumors with a volume greater than 0.5 cm3 (p = 0.0034). CONCLUSIONS: Gamma knife surgery is a safe and effective method to control hemangioblastomas for as many as 10 years. Higher doses and smaller tumors probably contribute to good outcomes. Recurrence outside the original irradiated area is common. Peritumoral contrast enhancement may be seen in larger tumors. The authors recommend regular imaging follow up and early repeated treatment in the face of new or growing tumors.

Adult↗
PubMed2005

Quantitative evaluation of the pyramidal tract segmented by diffusion tensor tractography: feasibility study in patients with amyotrophic lateral sclerosis.

PURPOSE: Diffusion tensor imaging can evaluate the cerebral white matter quantitatively using fractional anisotropy (FA) and also can extract a certain tract by tractography, but these two have been used separately and not combined. The purpose of this study was to assess the clinical feasibility of ROI analysis using diffusion tensor tractography (DTT) in patients with amyotrophic lateral sclerosis (ALS). MATERIALS AND METHODS: Sixteen patients with ALS (9 limb-onset type, 7 bulbar-onset type) and nine age-matched volunteers were studied. DTT of the corticobulbar tract (DTT-CBT) and corticospinal tract (DTT-CST) were visualized by free software (dTV/VOLUME-ONE). Regions-of-interest (ROIs) were semi-automatically placed on the tracts defined by DTT methods, and FA values within the ROIs were measured. RESULTS: Mean FA values of ALS patients in the ROIs along the DTT-CST (bulbar-onset: 0.574, limb-onset: 0.594) were significantly lower than those of controls (DTT-CST: 0.629) (p<0.05). The mean FA of DTT-CBT of the bulbar-onset type (0.509) was significantly lower than that of the limb-onset type (0.558) and that of volunteers (0.561). CONCLUSION: DTT could segmentate certain white matter tracts and evaluate them quantitatively. It could depict the subtle changes between subtypes of ALS as well as the changes between the patients and volunteers.

Amyotrophic Lateral Sclerosis↗
PubMed2005

[In-vitro phantoms for estimating diffusion tensor tractography].

No literature has reported on in-vitro diffusion tensor tractography, although it is a useful method to visualize neuronal fiber projections in the living human brain. We applied this technique to phantoms of asparagus stems and bundled polyester yarn, and obtained tractography with high-quality images. On the asparagus stem phantom, straight tracts along the axis were displayed. On the polyester phantom, these tracts followed the course of the bundle whether it was straight or curved. These phantoms are useful for in-vitro evaluation of diffusion tensor tractography.

Algorithms↗
PubMed2004

Potentiality of DNA-dependent protein kinase to phosphorylate Ser46 of human p53.

DNA damage induces accumulation and activation of p53 via various posttranslational modifications. Among them, several lines of evidence indicated the phosphorylation of Ser46 as an important mediator of DNA damage-induced apoptosis but the responsible kinase remains to be clarified, especially in the case of ionizing radiation (IR). Here we showed that DNA-dependent protein kinase (DNA-PK) could phosphorylate Ser46 of p53 in addition to reported phosphorylation sites Ser15 and Ser37. However, IR-induced phosphorylation of Ser46 was seen even in M059J, a human glioma cell line lacking DNA-PKcs, and it was, at most, only slightly less than in control M059K. On the other hand, a related kinase ataxia-telangiectasia mutated (ATM), which was shown to be essential for IR-induced phosphorylation of Ser46, could poorly phosphorylate Ser46 by itself. These results collectively suggested two pathways for IR-induced phosphorylation of Ser46, i.e., direct phosphorylation by DNA-PK and indirect phosphorylation via ATM.

Binding Sites↗
PubMed2004

Localized volume reduction in prefrontal, temporolimbic, and paralimbic regions in schizophrenia: an MRI parcellation study.

Functional and structural abnormalities of the anterior cingulate gyrus (ACG) in patients with schizophrenia have been repeatedly reported. However, one remaining issue is whether gray matter volume reduction in ACG exists to an extent comparable with, or even in excess of, that in other prefrontal and temporolimbic regions. High-spatial-resolution magnetic resonance imaging was performed on patients with schizophrenia (n=27) and on age-, gender-, and parental socioeconomic-status-matched healthy control subjects (n=27). After the gray and white matter were semiautomatically segmented, whole prefrontal and temporal lobes were manually parceled into 15 subregions-by-two hemispheres (30 regions of interest) constituting seven prefrontal gray matter regions, six temporal gray matter regions, the prefrontal white matter, and the temporal white matter. Compared with healthy subjects, schizophrenic patients showed significant gray matter volume reduction in the bilateral ACG, this being the largest effect size (left, 0.84; right, 0.56) among all the regions examined. There were also significant gray matter volume reductions in the bilateral posterior STG, bilateral inferior frontal gyrus, left posterior amygdala-hippocampal complex (mostly hippocampus), and the left insula. These results suggest that gray matter volume reductions in the ACG are prominent among prefrontal and temporolimbic regions in patients with schizophrenia. These findings indicate the importance of ACG abnormalities in the pathophysiology of schizophrenia.

Adult↗
PubMed2004

The optimal trackability threshold of fractional anisotropy for diffusion tensor tractography of the corticospinal tract.

PURPOSE: In order to ensure that three-dimensional diffusion tensor tractography (3D-DTT) of the corticospinal tract (CST), is performed accurately and efficiently, we set out to find the optimal lower threshold of fractional anisotropy (FA) below which tract elongation is terminated (trackability threshold). METHODS: Thirteen patients with acute or early subacute ischemic stroke causing motor deficits were enrolled in this study. We performed 3D-DTT of the CST with diffusion tensor MR (magnetic resonance) imaging. We segmented the CST and established a cross-section of the CST in a transaxial plane as a region of interest. Thus, we selectively measured the FA values of the right and left corticospinal tracts at the level of the cerebral peduncle, the posterior limb of the internal capsule, and the centrum semiovale. The FA values of the CST were also measured on the affected side at the level where the clinically relevant infarction was present in isotropic diffusion-weighted imaging. RESULTS: 3D-DTT allowed us to selectively measure the FA values of the CST. Among the 267 regions of interest we measured, the minimum FA value was 0.22. The FA values of the CST were smaller and more variable in the centrum semiovale than in the other regions. The mean minus twice the standard deviation of the FA values of the CST in the centrum semiovale was calculated at 0.22 on the normal unaffected side and 0.16 on the affected side. CONCLUSION: An FA value of about 0.20 was found to be the optimal trackability threshold.

Aged↗
PubMed2004

Utilization of low-field MR scanners.

The evident advantage of high-field MR (magnetic resonance) scanners is their higher signal-to-noise ratio, which results in improved imaging. While no reliable efficacy studies exist that compare the diagnostic capabilities of low- versus high-field scanners, the adoption and acceptance of low-field MRI (magnetic resonance imaging) is subject to biases. On the other hand, the cost savings associated with low-field MRI hardware are obvious. The running costs of a non-superconductive low-field scanner show even greater differences in favor of low-field scanners. Patient anxiety and safety issues also reflect the advantages of low-field scanners. Recent technological developments in the realm of low-field MR scanners will lead to higher image quality, shorter scan times, and refined imaging protocols. Interventional and intraoperative use also supports the installation of low-field MR scanners. Utilization of low-field systems has the potential to enhance overall cost reductions with little or no loss of diagnostic performance.

Cost-Benefit Analysis↗
PubMed2004

Amyotrophic lateral sclerosis: diffusion tensor tractography and voxel-based analysis.

The purpose of this study is to investigate whether the diffusional anisotropy of water molecules is disrupted in the pyramidal and extra-pyramidal regions in patients with amyotrophic lateral sclerosis (ALS). We studied seven patients with probable ALS (four women, mean age +/- SD, 57.3 +/- 6.2 years old) according to the criteria of the World Federation of Neurology. A control group consisted of 11 age- and sex-matched volunteers (six women, 57.1 +/- 4.5) without disorders affecting the central nervous system. Voxel-based diffusion tensor analysis was made with statistical parametric mapping (SPM99). We also created the normalized corticospinal tractography from the diffusion tensor data. The significant fractional anisotropy (FA) decrease in the ALS group was found in the right frontal subgyral white matter and left frontal precentral white matter. These clusters with significant FA decrease corresponded well to the average group map of the corticospinal tract in a standard reference frame. These results suggested that the combination of voxel-based diffusion tensor analysis and diffusion tensor tractography might help determine the location of the affected neuronal tissues among ALS patients in a non-invasive manner.

Algorithms↗
PubMed2004

Impaired myocardial vasodilatation during hyperaemic stress is improved by simvastatin but not by pravastatin in patients with hypercholesterolaemia.

AIMS: Impaired myocardial vasodilatation during hyperaemic stress with dipyridamole has been documented in hypercholesterolaemics without evidence of ischaemia. This study investigated whether two commonly used hydroxymethylglutaryl coenzyme A reductase inhibitors, simvastatin and pravastatin, are equally effective in restoring myocardial vasodilatation. METHODS AND RESULTS: Forty-four hypercholesterolaemics with a low probability of coronary artery disease and 22 controls were studied. Before and after lipid-lowering therapy with simvastatin (n = 22) or pravastatin (n = 22), myocardial blood flow at rest and during dipyridamole loading was measured using positron emission tomography with [(13)N]ammonia, and myocardial vasodilatation was assessed. Treatments with simvastatin and pravastatin similarly reduced plasma total cholesterol and plasma low-density lipoprotein cholesterol. Resting myocardial blood flow was comparable in the controls, simvastatin group, and pravastatin group and unchanged after therapy. Myocardial blood flow during dipyridamole loading and myocardial vasodilatation was lower in the two therapy groups before treatment than in the controls. These parameters improved significantly after therapy with simvastatin, whereas no improvement was observed after pravastatin therapy. The per cent change in myocardial vasodilatation after simvastatin therapy was significantly and inversely correlated with per cent changes in plasma lipid fractions. CONCLUSION: Diminished myocardial vasodilatation in hypercholesterolaemics is improved by simvastatin but not by pravastatin, suggesting differences in vascular effects among statins.

Anticholesteremic Agents↗
PubMed2004

Abnormal association between reduced magnetic mismatch field to speech sounds and smaller left planum temporale volume in schizophrenia.

Schizophrenia is associated with language-related dysfunction. A previous study [Schizophr. Res. 59 (2003c) 159] has shown that this abnormality is present at the level of automatic discrimination of change in speech sounds, as revealed by magnetoencephalographic recording of auditory mismatch field in response to across-category change in vowels. Here, we investigated the neuroanatomical substrate for this physiological abnormality. Thirteen patients with schizophrenia and 19 matched control subjects were examined using magnetoencephalography (MEG) and high-resolution magnetic resonance imaging (MRI) to evaluate both mismatch field strengths in response to change between vowel /a/ and /o/, and gray matter volumes of Heschl's gyrus (HG) and planum temporale (PT). The magnetic global field power of mismatch response to change in phonemes showed a bilateral reduction in patients with schizophrenia. The gray matter volume of left planum temporale, but not right planum temporale or bilateral Heschl's gyrus, was significantly smaller in patients with schizophrenia compared with that in control subjects. Furthermore, the phonetic mismatch strength in the left hemisphere was significantly correlated with left planum temporale gray matter volume in patients with schizophrenia only. These results suggest that structural abnormalities of the planum temporale may underlie the functional abnormalities of fundamental language-related processing in schizophrenia.

Adult↗
PubMed2004

New method of using reconstructed images for assessment of patency of intracochlear spaces for cochlear implant candidates.

OBJECTIVE/HYPOTHESIS: A new method of reconstruction using multidetector-row helical computed tomography (MDCT) was applied for assessment of cochlear patency in cochlear implantation candidates. STUDY DESIGN: Descriptive study comparing radiologic and surgical findings in eight radiologically normal cochleas and four abnormal cases. METHODS: In unusual cases including cochlear ossification and misinsertion of electrodes, intracochlear space was evaluated on two types of reconstructed images: the "basal turn plane" that was vertical to the modiolus and contained whole basal turn was effective in the assessment of the lining of the inner bony wall of the otic capsule; "cochlear cross plane" images allowed evaluation of the patency of the intracochlear space and the location of inserted electrodes at the sections vertical to the direction of insertion of the electrodes. RESULTS: Preoperative evaluation was useful for predicting possible problems in electrode insertion and therefore helped in decision-making in regards to surgical strategies, especially in candidates with a high probability of cochlear ossification such as those with meningitis and otosclerosis. Furthermore, the new reconstruction method also provided useful information on the position of the cochlear implant electrodes after surgery. CONCLUSIONS: These unusual cases demonstrated that preoperative MDCT evaluation by our reconstruction method was useful for predicting possible problems in electrode insertion and decision-making in regards to surgical strategies, especially in cochlear implantation candidates with a high probability of cochlear stenosis.

Adolescent↗