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Biomedical subjects

K Ohtomo

Publications and source records attributed to K Ohtomo.

At least 235 records · Page 13Linked to original sources
PubMedDate not supplied

Portosystemic collaterals on MR imaging.

Fourteen patients with various portosystemic collaterals (seven esophageal varices, three paraumbilical veins, two splenorenal shunts, and two mesenteric varices) were imaged with magnetic resonance (MR) imaging using a superconducting imager. Collateral pathways were demonstrated as tortuous structures of no or low signal intensity on spin-echo image, and flow related enhancement did not cause any difficulty in evaluation. Direct sagittal images are especially useful for paraumbilical vein and coronal images for esophageal and mesenteric varix. The clinical role of MR in the assessment of portosystemic collaterals is discussed also in comparison with CT and ultrasound.

Adult↗
PubMedDate not supplied

MR imaging of hepatocellular carcinoma.

Forty-two patients with hepatocellular carcinoma (HCC) were examined by magnetic resonance (MR) imaging. The presence of tumor was suggested in 41 of 42 cases by a high-intensity area on T2 weighted spin-echo (SE) images with a repetition time (TR) of 1.6 s. Specific findings of HCC such as the presence of a capsule, mosaic pattern, and tumor thrombus in major veins were noted in 10, two, and seven cases, respectively. In six cases the tumor pattern changed from a well-defined mass to an irregular, ill-defined one according to pulse sequence (SE: echo time 35 and 70 ms; TR 1.6 and 0.4 s). In our early experience MR was almost equal to conventional X-ray CT in the detection of main or daughter lesions and in the determination of extent and characterization of HCC.

Adult↗
PubMedDate not supplied

MR imaging of hepatoma treated by embolization.

The magnetic resonance findings of two hepatomas treated by embolization are presented. The T2-weighted spin echo images showed an increase in signal intensity in the tumor after embolization. This phenomenon corresponded to a decrease in tumor density on CT and to necrosis observed histologically. Magnetic resonance also demonstrated gas bubbles as low signal foci within the embolized tumor.

Carcinoma, Hepatocellular↗
PubMedDate not supplied

CT demonstration of gas in dilated pancreatic duct.

A case of "innocent" pancreatic gas is reported. The patient had cystic dilatation of the main pancreatic duct limited to the head. Air entered through the patulous ampulla of Vater. Pancreatic gas can be present without abscess or fistula.

Aged↗
PubMedDate not supplied

CT and MR imaging of fatty tumors of the liver.

The presence of fat in hepatic masses narrows the range of differential diagnoses down to hepatic angiomyolipoma, lipoma, adenoma, hepatoma, metastatic fatty tumors of the liver, focal fatty infiltration of the liver, and extrahepatic fatty masses such as intraperitoneal implants from malignant teratomas, and packed omentum. We report six hepatic tumors containing fat (lipoma, hepatocellular carcinoma, and calcified mass with fat-fluid level) with CT and magnetic resonance (MR) imaging. The distribution of fat was diffuse in the lipomas and some hepatocellular carcinomas and localized in other hepatocellular carcinomas and fat-fluid masses. The density ranged from - 100 to 0 HU. High intensity areas on both T1- and T2-weighted MR images corresponded to the hypodense areas on CT.

Adult↗
PubMedDate not supplied

CT demonstration of fluid-fluid levels in nonenhancing hemangiomas of the liver.

A fluid-fluid level was observed in three cases of liver hemangioma and in two cases of liver cancer. The patients with hemangioma of the liver did not show enhancement on dynamic CT and the fluid-fluid levels were not detected by ultrasound in two of these patients. Fluid-fluid levels detected by CT but not by ultrasound strongly suggested the diagnosis of nonenhancing hemangioma of the liver.

Carcinoma, Hepatocellular↗
PubMedDate not supplied

Microcystic adenoma of the pancreas: spectrum of computed tomographic findings.

Fourteen cases of microcystic adenoma (serous cystadenoma) of the pancreas were reviewed and radiological findings were correlated with pathological specimens. Microcystic adenomas appeared grossly either as solid tumors with innumerable tiny cysts or as honeycombed cystic tumors depending on the size and number of cysts and amount of connective tissue. Dynamic enhanced CT of the tumor reflected the amount of connective tissue and appeared as (a) densely enhanced spongy masses (n = 6: classic appearance); (b) cystic masses with (n = 6) or without (n = 1) enhanced septa; or (c) dense diffusely enhanced mass (n = 1). Ultrasound similarly showed a variety of features such as echogenic masses with or without small cystic portions, multilocular cysts, or mixed hyperechoic and hypoechoic masses. The ultrasonic features mainly reflected the dominant sizes of cysts. Angiography almost always showed inhomogeneously hypervascular masses with tumor vessels. The imaging diagnosis is easy and conclusive in classic subtypes, but a correct diagnosis can be made even in other subtypes. However, mucinous cystic neoplasm can be confused with microcystic adenoma with large cysts and a small amount of connective tissue, and islet cell tumors can be mistaken for microcystic tumors with minute cysts.

Adult↗
PubMedDate not supplied

CT and MR imaging of postnecrotic liver scars.

Four cases of postnecrotic liver scar were examined by dynamic CT or MR imaging or both. Postnecrotic scars appeared as low-density areas on plain CT, showed marked and prolonged enhancement on single level dynamic CT, and became isodense on postcontrast scan. On T2-weighted images, postnecrotic scar were as hyperintense as the spleen. Postnecrotic liver scar is an example of localized attenuation or intensity difference not corresponding to mass lesion. It should be distinguished from mass lesions associated with lobar or segmental attenuation (or intensity) difference of the liver as well as nonmass lesions such as irregular fatty infiltration, radiation hepatitis, and hepatic infarction.

Adult↗
PubMedDate not supplied

CT and MR appearances of splenic hamartoma.

The MR and CT appearances of two cases of splenic hamartoma are presented. Computed tomography showed a well demarcated low-density mass without calcification. Dense spreading enhancement was seen in one case on dynamic CT, and prolonged enhancement was noted in both. The masses were demonstrated as areas of isointensity on T1-weighted MR images and of high intensity on T2-weighted images. On gadolinium-enhanced T1-weighted images they were shown as areas of high intensity. Prolonged enhancement on postcontrast CT and MR imaging was a useful finding in differentiation of splenic hamartoma from malignant lesions of the spleen, especially from nodular lesions of malignant lymphoma.

Adult↗
PubMedDate not supplied

Breath-hold T2-weighted MRI of hepatic tumors: value of echo planar imaging with diffusion-sensitizing gradient.

PURPOSE: The purpose of our study was to evaluate the efficacy of echo planar imaging (EPI) as a breath-holding T2-weighted technique for imaging focal hepatic lesions. METHOD: Forty-eight patients with focal hepatic lesions (9 metastases, 21 hepatocellular carcinomas, 1 cholangiocarcinoma, 16 hemangiomas, and 2 cysts) underwent single shot EPI with and without a small diffusion-sensitizing gradient (DSG) (beta values = 55 s/mm2) at 1.5 T. Comparison was made with breath-holding T2-weighted fast SE (FSE) sequences. RESULTS: Lesion-to-liver signal intensity ratio of EPI was significantly better than that of T2-weighted FSE (p < 0.05) in patients with metastasis. Use of DSG suppressed bright signals from vessels or periportal tissue, resulting in better conspicuity of small lesions. EPI with DSG visualized more metastatic deposits than T2-weighted FSE (p < 0.01). CONCLUSION: EPI with a small DSG is helpful for detection of small hepatic metastases.

Adult↗
PubMedDate not supplied

Pedunculated bronchogenic cyst mimicking pleural lesion.

We report a rare case of a bronchogenic cyst presenting as a pleural nodule. CT and MRI demonstrated a well circumscribed, homogeneous lesion located on the pleural surface apart from the mediastinum. It was proven to be a bronchogenic cyst localized between the parietal and visceral pleurae and connected with the mediastinum only through fibrous tissue. Radiologists should be aware that a mediastinal bronchogenic cyst may be located apart from the mediastinum.

Bronchogenic Cyst↗
PubMedDate not supplied

Diffusion property in a hamartomatous lesion of neurofibromatosis type 1.

Though diffusion-weighted MRI has been applied to various intracranial lesions, few reports had been presented about cerebral hamartomatous lesions in patients with neurofibromatosis type 1 (NF1). In this study, we report the interval changes of apparent diffusion coefficient (ADC) in a presumed hamartomatous lesion. In our case, the ADC increased slightly over a 3 year period. This diffusion property may provide specific insight into the etiology of cerebral hamartomatous lesions observed in NF1.

Brain Diseases↗
PubMedDate not supplied

A new bisphosphonate treatment option for giant cell tumors.

Treatment of giant cell tumors (GCT) especially in the vertebrae remains controversial. With multidisciplinary treatments, their results are still insufficient. Moreover, GCT shows the potential for malignant transformation and metastasis, additional options such as adjuvant medication must be considered. We report favorable results in three consecutive cases diagnosed with GCT of the spine which were treated with radiotherapy and bisphosphonate (BP) as a new treatment option, and present a review of the literature and a comparison with these case reports.

Adult↗
PubMedDate not supplied

A quantitative analysis of rat osteoporosis model with a microfocus X-ray tube and digital radiography system.

We have developed an X-ray magnification radiographic system incorporating a microfocus X-ray tube and an imaging plate in order to analyze the trabecular structure and mineral content of rat bone. Femoral bones of control, ovariectomy, and leuprorelin acetate depot rat groups were extracted and tested after the animals were sacrificed. Eleven water-equivalent phantoms, which contained hydroxyapatite at a density of 0 to 400 mg/cm3, were set around each femur and radiographed at the same time. The mean read-out signal intensity of the region of interest in the femur was converted to bone mineral density expressed in hydroxyapatite density through the use of a calibration curve relating the signal intensity to the hydroxyapatite density of the phantoms. The bone mineral density of the ovariectomy group was significantly lower than that of the control group, and no differences were found between the control and the leuprorelin acetate depot group. The present system is thought to be useful for quantitative evaluation of the mineral density of the rat femur.

Absorptiometry, Photon↗
PubMedDate not supplied

Deadtime of a single-crystal gamma camera in abdominal imaging.

The deadtime of a single-crystal gamma camera depends on the scattering condition, and differs among patients. The aim of this study was to estimate deadtime in posterior abdominal imaging. Radionuclide angiography of the posterior abdominal view was performed in 23 patients with a point source in the field-of-view, and temporal changes in count loss were assessed. The deadtime for each patient was calculated based on the count loss for the point source. The estimated deadtime ranged from 7.83-12.52 microsec, and was significantly correlated with the ratio of body weight in kg to body height in cm (y=13.143x+5.595, r=0.852, p<0.001). Count loss was successfully corrected using the deadtime predicted with the regression equation. In conclusion, the deadtime in posterior abdominal imaging can be predicted for each patient from the body weight and body height. The predicted deadtime may aid in improving the reliability of quantitative measurements by scintigraphic techniques.

Abdomen↗
PubMedDate not supplied

Induction of apoptosis by dopamine in human oral tumor cell lines.

Dopamine dose-dependently reduced the viable cell number of both human salivary gland tumor HSG and oral squamous cell carcinoma HSC-2, HSC-4, and NA cells. CoCl2 significantly reduced both the cytotoxic activity and radical intensity of dopamine (determined by ESR spectroscopy). Dopamine produced DNA fragments (demonstrated by TUNEL method) and induced degradation of cytokeratin by activated caspase in HSG cells (detected by an immunocytochemical method, using a specific M30 monoclonal antibody). FACS analysis demonstrated that dopamine induced DNA fragmentation, a biochemical hallmark of apoptosis, in human promyelocytic leukemia HL-60 cells. The addition of catalase did not prevent the apoptosis-inducing activity of dopamine, reducing the possibility of the involvement of H2O2 for dopamine-induced apoptosis. Dopamine transiently induced p38 mitogen-activated protein kinase (MAP kinase) phosphorylation. However, an inhibitor of p38 MAP kinase phosphorylation, SB203680, failed to inhibit the dopamine-induced apoptosis. These data suggest that p38 phosphorylation at an early stage may not be a causative event for apoptosis.

Apoptosis↗