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Biomedical subjects

K Ohtomo

Publications and source records attributed to K Ohtomo.

At least 253 records · Page 14Linked to original sources
PubMedDate not supplied

C-MOS flat-panel sensor for real-time X-ray imaging.

PURPOSE: The aim of this report is to introduce a flat-panel, self-scanning, solid-state diagnostic X-ray imaging device using complementary metal-oxide-semiconductor (C-MOS) arrays for real time digital X-ray imaging and to present findings on its performance. METHODS: A device with a 5.12 cm by 5.12 cm sensor area was developed and tested. The device consists of a cesium iodide scintillator and C-MOS detector arrays. The detector arrays are composed of a regular arrangement of pixels (256x256), each of which is made of a C-MOS photodiode sensor coupled to a C-MOS FET (field effect transistor). RESULTS: A sampling speed of 30 frames per second and spatial resolution of 2.5 lines per mm were achieved. Noise level and maximum signal were 1.5 mV rms and 1.8 V, respectively. CONCLUSIONS: The C-MOS flat-panel sensor is a significant step in actualizing real-time X-ray imaging. A large area sensor needs to be fabricated for clincial use.

Cesium↗
PubMedDate not supplied

Contrast medium precipitation in the stomach between contiguous plain and contrast CT scans.

Precipitation of diluted Gastrografin (meglumine sodium amidotrizoate) occurred in the stomach during computed tomography (CT) examination in a 43-year-old man with fasting. Precipitation was not observed on the initial plain CT scan, but was demonstrated on the contrast-enhanced CT scan following the plain CT. Hyperacidity in the stomach might be promoted during CT examination and cause precipitation between scans.

Adult↗
PubMedDate not supplied

Multilocular cystic hemangioma: CT and MR appearance.

An atypical case of multilocular cystic hemangioma is presented. A 4.5 cm multilocular cystic mass was incidentally found in a 66-year-old healthy woman on ultrasound screening. CT, MR imaging, and angiography were performed: however, the features that are characteristic of cavernous hemangioma were not obtained. The final diagnosis could not be made until surgery.

Aged↗
PubMedDate not supplied

Experimental study on the electrophysiological effects of the combination of the antiarrhythmic drugs aprindine and verapamil.

The acute electrophysiological effects of the antiarrhythmic drugs aprindine and verapamil, injected intravenously either alone or in combination, were studied in 14 dogs during invasive electrophysiology. The AH and HV intervals during sinus rhythm were significantly prolonged, especially in the aprindine and the aprindine plus verapamil groups. The cycle lengths of the antegrade and retrograde atrio-ventricular block were most prolonged in the combination group. The effective refractory period and the functional refractory period of the atrial tissue, as well as the functional refractory period of the atrio-ventricular node, the effective refractory period of ventricular tissue and the ventriculo-atrial conduction system were most prolonged when the combination of the agents was given. The effective refractory period of the atrio-ventricular node was prolonged in the groups receiving verapamil and verapamil plus aprindine. There was no significant difference in the serum concentration of each agent given alone or in combination. These results suggest that the efficacy of the combination of verapamil and aprindine may be due to additive or synergistic effects of these antiarrhythmic agents.

Animals↗
PubMedDate not supplied

Magnetic resonance imaging in chronic liver disease evaluated in relation to hepatic fibrosis--clinical and experimental results.

In 21 patients with chronic liver disease, the ratio of liver to muscle signal intensity on T1-weighted images was negatively correlated with the progression of hepatic fibrosis defined according to findings by laparoscopy and liver biopsy, and differentiated six patients with early chronic hepatitis from eight with liver cirrhosis. On T2-weighted images, the number of low intensity nodules comparable in size to regenerating nodules surrounded by connective tissues showed a positive correlation with stage. When hepatic fibrosis with no necrosis or fat infiltration was induced in rats, T2 values were positively correlated with hepatic hydroxyproline content, though there was no such correlation for T1 values. These results suggest that MR imaging may be useful for determining the progression of hepatic fibrosis in chronic liver disease. T2 values may directly reflect hepatic fibrosis.

Adult↗
PubMedDate not supplied

Hepatocellular carcinoma: MR appearance mimicking cavernous hemangioma.

A case of hepatocellular carcinoma is reported in which a calculated T2 value of the tumor was exceptionally long and differentiation from cavernous hemangioma based on T2 signal intensity was difficult. Pathologically, the mass consisted of dense, homogeneous acinar formation (pseudoglandular type). The T2 prolongation of the mass was probably due to abundant fluid in the acini.

Carcinoma, Hepatocellular↗
PubMedDate not supplied

Analysis of imaging parameters, relaxation time (T1,T2), and relative proton density as they influence the signal intensity of spin echo images.

It is difficult to recognize signal intensity changes on spin echo (SE) images. Clinically both T1-weighted and T2-weighted images are now used in most institutions to evaluate signal intensity changes due to different T1 and T2 of the lesions in MRI. However, these are not sufficient to understand signal intensity changes completely. The authors attempted to summarize on a two-dimensional graph the effects of T1, T2, proton density, and imaging parameters that influence signal intensities on SE images. Both end point (E) and start point (S), as defined later, depended mainly on proton density, but the former also depended on T2 and the later on T1 value. The image obtained in the former situation (near point E) was then called the T2-weighted image. Conditions to accelerate recovery and attenuation velocities (VR and VA), also mentioned later, were the same as those that increased points E and S, respectively. However, when TR was relatively short, the effect of a shorter T1 on VR was greatly emphasized. Such an image was then called the T1-weighted image.

Adult↗
PubMedDate not supplied

Diagnosis of coexistent hepatic tumors of different kinds: a challenge from CT and MR imaging.

Three cases of multiple, different liver tumors in the same patient were examined with CT and MR imaging. Two patients with coexistent hepatocellular carcinoma and cavernous hemangioma were correctly diagnosed by the following characteristic findings on dynamic CT and/or MR images; spreading and markedly prolonged enhancement in cavernous hemangioma, and the presence of capsule and/or transient diffuse enhancement in hepatocellular carcinoma. The third case of hepatocellular carcinoma and cholangiocarcinoma showed typical findings of hepatocellular carcinoma in one tumor and unusual complex enhancement in the other. CT and MR imaging may enable correct diagnosis to be made even in patients with multiple liver tumors of different kinds.

Adenoma, Bile Duct↗
PubMedDate not supplied

Transhepatic portosystemic collateral pathway via an accessory left gastric vein.

An unusual transhepatic collateral was found in a patient with portal hypertension. This pathway originated from an anomalous portal branch that arose from the left portal vein branch, and was considered a venous analogy to an accompanying accessory left gastric artery. A relation between the development of the intrahepatic pathway and variation in the hepatic artery is suggested.

Aged↗
PubMedDate not supplied

Ultrasonography of small hepatic tumors.

The differential accuracy of ultrasonographic examinations of small hepatic tumours was analyzed by receiver-operating characteristics. Using only one image of a single hepatic tumor under 3 cm in diameter as revealed by real-time scanner, the readers were requested to select one out of five diagnoses (hepatocellular carcinoma, metastatic tumor, cavernous hemangioma, cyst, or miscellaneous) and to choose the credibility from five levels of confidence. The averaged diagnostic accuracy was 68% in hepatocellular carcinoma, 70% in metastatic tumor, and 77% in cavernous hemangioma. Hepatic tumors were classified retrospectively into eight ultrasonographic patterns, based on mutual consent. The mosaic and hypoechoic patterns were relatively characteristic of hepatocellular carcinoma (91% and 92% respectively). Except for these two patterns, ultrasonographic findings in small liver tumors were nonspecific, including frequently reported hyperechoic pattern for cavernous hemangioma.

Carcinoma, Hepatocellular↗
PubMedDate not supplied

Hepatic cavernous hemangioma in patients at high risk for liver cancer.

Cavernous hemangioma of the liver occurring in patients at high risk for liver cancer has been reviewed. Twenty-four patients with hemangioma were encountered during the past 4 years. Five lesions over 3 cm in diameter were correctly diagnosed with enhanced CT alone. Definite CT findings were however obtained in only 6 out of 19 lesions smaller than 3 cm in diameter. Ultrasonography was the most sensitive method for picking up small liver tumors even when compared with angiography, but the findings were non-specific (an echogenic mass was noted in 14 of the 19 lesions). Magnetic resonance imaging (MRI) had almost the same sensitivity as ultrasound in detecting small hemangiomas, and a prolonged T2 was highly suggestive of the diagnosis (T2 over 80 ms in 8 of 11 lesions). The results suggest that combined use of non-invasive diagnostic modalities has sufficient reliability to make a diagnosis of cavernous hemangioma even in small hepatic lesions, in patients at high risk for liver cancer.

Angiography↗
PubMedDate not supplied

CT manifestation of neutron radiotherapy-induced changes in lung.

Sixty-nine chest CT studies of 36 patients with lung cancer were obtained at various times (21 to 649 days) following completion of fast neutron radiotherapy. Multiple scans (2 to 7) were available in 16 cases. Fractionated neutron radiotherapy was delivered over four to seven weeks to a total dose of 60 to 67 Gy photon equivalent. Parenchymal change within the lung was noted in 43% by 12 weeks, in 91% between 12 and 24 weeks, and in 100% after 24 weeks. Three different patterns of lung parenchymal change were evident. Ectatic air-filled bronchi were observed in more than 50% after 24 weeks. Mediastinal shift and thoracic shrinkage were demonstrated in six and three cases, respectively. Serial CT scans revealed that lung parenchymal changes usually became stable or shrunk after 36 weeks. The possible effect of chemotherapy (mitomycin-C, vinblastin and cis-platinum), in 19 of these patients is also discussed.

Adult↗
PubMedDate not supplied

Transcatheter arterial embolization for spontaneous rupture of hepatocellular carcinoma.

Transcatheter arterial embolization (TAE) was performed in 20 patients with ruptured hepatocellular carcinoma (HCC). Bleeding was improved in all patients, but only four survived for over three months. Rerupture occurred in seven patients (35%) and the prognosis was extremely poor. TAE should be considered the treatment of choice for ruptured HCC; however, long-term survival was limited to those patients without portal extension of HCC. The severity of rupture also influenced the prognosis.

Adult↗
PubMedDate not supplied

Magnetic resonance imaging (MRI) of primary liver cancer--MRI-pathologic correlation.

In seven primary liver cancers (HCC 5, CCC 1, mixed 1), MR images (0.35 Tesla super-conducting) were compared with macroscopic appearances, and relaxation times (T1 and T2) with microscopic characteristics. MRI was able to reveal the gross appearance of five nodular lesions, but did not reveal one diffuse HCC and one nodular HCC with marked extracapsular extension. T2-weighted SE images could not demonstrate fibrous capsules around the tumor in four nodular HCCs. The T1 and T2 values of the tumors were longer than those of the surrounding liver parenchyma, and the T1 elongation corresponded roughly to the degree of necrosis and fibrosis within the tumors.

Adult↗
PubMedDate not supplied

Transcatheter arterial embolization (TAE) in treatment for hepatoma--analysis of three-year survivors.

Among 224 hepatomas treated with transcatheter arterial embolization, ten patients who survived for three years are presented. All cases had nodular lesions and the volume ratio of tumor to liver was less than 10% in nine cases. Eight cases had no large venous extension, however, one had 90% occlusion of the portal trunk and the other had tumor thrombus within the inferior vena cava. Laboratory data showed liver function was largely spared in eight cases, whereas the other two had severe liver cirrhosis. CT and/or angiography showed an increase in tumor volume in eight cases after three years of survival. Beneficial factors for long-term survival and the limitations of embolization are also discussed.

Adult↗
PubMedDate not supplied

31P-NMR spectroscopy of myopathies: clinical application of whole-body MR.

Patients with myopathies were examined by 31P-NMR spectroscopy using a whole body MR system operating at 1.5 T. Spectra from the femoral muscles were measured as a function of time during a post-exercise recovery period. A 4-min scanning time was used to obtain a good S/N ratio and enable us to evaluate the relative intensity and position of each absorption line. The results were expressed by PCr/Pi ratio and pH value and compared with values before exercise. Clear changes were observed in the recovery process after workload depending on the stage of disease. We were able to observe the in vivo dynamic energy metabolism of myopathies by whole-body MR.

Adult↗
PubMedDate not supplied

Dynamic MRI of hepatic tumors using gadolinium-DTPA--preliminary results.

Dynamic magnetic resonance imaging (MRI) was performed in two patients with hepatic tumors (one cavernous hemangioma and one hepatoma). A sequential timed scanning technique with spin echo images (TR: 100 msec; TE: 20 msec; data acquisition time: 26 sec) was used with a bolus injection of 0.05 mmol/kg gadolinium DTPA. Dynamic MRI findings in the two cases were similar to those obtained with dynamic CT and angiography using iodinated contrast medium. Our early experience suggested that the less invasive technique of dynamic MRI could replace conventional dynamic CT in assessing the hemodynamics of hepatic tumors.

Carcinoma, Hepatocellular↗