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Biomedical subjects

K Ohara

Publications and source records attributed to K Ohara.

At least 523 records · Page 29Linked to original sources

Resection combined with intraoperative radiation therapy (IORT) for stage IV (TNM) gallbladder carcinoma.

From October 1976 to May, 1990, a total of 86 patients with stage IV (TNM) gallbladder cancer were treated at Tsukuba University Hospital. Twenty-seven of the 86 patients underwent tumor resection; 43 patients received palliative surgery. The remaining 16 were too advanced to have surgery. Of 27 patients who had tumor resection, 9 had resection alone, 17 had intraoperative radiation therapy (IORT) +/- postoperative external radiotherapy (ERT), and 1 had postoperative ERT. The procedures used were: extended right hepatic lobectomy plus hepaticobiliary resection (HBR) (n = 2), hepatic segmentectomy (SIVb, SV) plus HBR (n = 9), hepatic segmentectomy (SIV, V, VI) with HBR (n = 1), hepatic segmentectomy (SIV, V) plus HBR with pancreaticoduodenectomy (PD) (n = 3), PD plus HBR (n = 1), cholecystectomy with wedge resection of the gallbladder fossa plus HBR (n = 3), and cholecystectomy plus HBR (n = 3), and cholecystectomy (n = 4). Regional lymph node dissections were performed in every patient and 17 of 27 patients underwent additional resections of adjacent organs such as the stomach, duodenum, colon, and abdominal wall. A single dose of 20-30 Gy was delivered intraoperatively for 17 patients. A mean total dose of 36.4 Gy (1.8/fraction) was added to IORT for 10 patients. The three-year cumulative survival rate was 10.1% for resection plus IORT but 0% for resection alone. The longest survivor is alive and well at 3 years and 3 patients are alive 16, 13, and 4 months after tumor resection followed by IORT plus ERT.

Adenocarcinoma↗

The micronucleus test of methyl methanesulfonate with mouse peripheral blood reticulocytes using acridine orange-coated slides.

The usefulness of the micronucleus assay using mouse peripheral blood erythrocytes and acridine orange (AO)-coated slides was evaluated with methyl methanesulfonate (MMS). The micronucleus test was carried out at doses ranging from 20 to 80 mg/kg body weight in CD-1 mice by intraperitoneal injection. Peripheral blood cells were examined from 0 to 72 h after treatment at 12- or 24-h intervals. Bone marrow cells from other mice treated with 80 mg/kg MMS were also sampled at the same times. The frequency of micronucleated reticulocytes (MNRETs) increased dose-dependently at every sampling time except 72 h, and the maximum frequency of MNRETs was observed at about 36 h after treatment. Micronucleated polychromatic erythrocytes (MNPCEs) in bone marrow after a dose of 80 mg/kg were significantly induced at 12 h to 36 h, and the maximum frequency of MNPCEs was observed at 24 h after treatment. The induction of MNRETs was delayed by about 12 h compared to that of MNPCEs in bone marrow, and the maximum frequencies of MNRETs were lower than those of MNPCEs, but the induction of MNRETs by MMS was significant and dose-dependent. It is concluded, therefore, that bone marrow cells could be replaced by peripheral blood cells as material for the micronucleus assay using AO-coated slides.

Acridine Orange↗

Acute retinal necrosis following contralateral herpes zoster ophthalmicus.

BACKGROUND: A case report of contralateral acute retinal necrosis (ARN) following herpes zoster ophthalmicus. CASE: A 61-year-old male patient developed iridocyclitis and well-demarcated creamy-white retinal lesions at the nasal periphery in the right eye 1 month after herpes zoster ophthalmicus in the left eye. The patient had undergone surgery for primary lung cancer, and had subsequent intracranial metastasis of the tumor. OBSERVATIONS: The clinical diagnosis of ARN was supported by polymerase chain reaction investigation of the aqueous humor resulting in positive for varicella-zoster virus. Retinal lesions disappeared after systemic treatment with acyclovir, corticosteroids, and acetylsalicylate. No retinal detachment developed. CONCLUSIONS: We propose a careful ophthalmic follow-up for herpes zoster ophthalmicus patients because of the possibility of acute retinal necrosis developing in the contralateral eye.

Acyclovir↗

Glucose transporter 1 expression in corneal wound repair under high serum glucose level.

PURPOSE: To determine glucose transporter (GLUT) 1 mRNA and protein expression during corneal epithelial wound healing in diabetic rat. METHODS: Diabetes mellitus was induced by intraperitoneal injection of streptozotocin. At 10 days after injection, unilateral 3-mm epithelial debridement was carried out in the central cornea. At 2, 4, 6, and 24 hours after wounding, whole corneal epithelium was collected and GLUT1 protein and mRNA levels were determined by Western blotting and reverse transcription-polymerase chain reaction, respectively. Sugar content in collected samples was measured by the Anthrone reaction. Normal rats were used as controls. RESULTS: Glucose transporter 1 protein and mRNA levels in unwounded cornea were similarly low in the diabetic and control groups. Healing of corneal wounds was slower in diabetic rats than in controls. After wounding, GLUT1 mRNA and protein expression in both groups were similarly enhanced compared to unwounded epithelium. Sugar content at all time points did not show significant alteration in any group, although in diabetic rats it was significantly higher than in controls throughout the time course. CONCLUSION: Glucose transporter 1 expression in diabetic rat cornea showed little difference from that in normal rat cornea, suggesting minimal influence of GLUT1 on the delayed healing of diabetic corneal wounds.

Animals↗

Use of small pelvic field instead of whole pelvic field in postoperative radiotherapy for node-negative, high-risk stages I and II cervical squamous cell carcinoma.

We investigated whether a small pelvic (SP) field that covers primarily the pericervical regions in postoperative radiotherapy for cervical squamous cell carcinoma is adequate for a subgroup of node-negative patients. Of 84 patients with stage I-II disease treated with postoperative radiotherapy due to pathologic risk factors, 42 node-negative patients received SP-field radiotherapy, whereas remaining 42 node-positive patients were treated with a conventional whole pelvic (WP) field that also covered pelvic lymph nodes, both with 50.0-50.4 Gy/25-28 fractions. The pathologic risk factors included positive nodes, deep stromal invasion (>/=2 /3 thickness), parametrial extension, and positive or close surgical margin. Recurrence was identified for 20 patients: three in the SP group and 17 in the WP group. Intrapelvic recurrence accounted for all three recurrences in the SP group and for four in the WP group; 5-year pelvic-control rate did not differ significantly between the SP (93%) and WP (90%) groups. Extrapelvic recurrence (n = 11) was identified exclusively in the WP group. Patterns of recurrence indicate that use of an SP field instead of a WP field may be adequate in postoperative radiotherapy for a subgroup of node-negative, high-risk patients.

Adult↗

Early radiation effects on the liver demonstrated on superparamegnetic iron oxide-enhanced T1-weighted MRI.

Early radiation-induced liver injury during radiotherapy detected by a particulate reticuloendothelial MR contrast agent (superparamagnetic iron oxide; SPIO) is described in a patient with cholangiocarcinoma. The irradiated hepatic parenchyma appeared as a heterogeneous, less decreased signal intensity area than the nonirradiated area on MR images after SPIO administration. Resultant differences in signal intensity were better visualized on SPIO-enhanced T1-weighted images than SPIO-enhanced T2-weighted images, although SPIO-enhanced T2*-weighted fast field echo imaging was the most sensitive.

Contrast Media↗

Alignment of x-ray tube focal spots for spectral measurement.

A general method to align a diagnostic x-ray machine for x-ray spectrum measurement purpose was theoretically and experimentally investigated by means of the optical alignment of focal pinhole images. Focal pinhole images were obtained by using a multi-pinholed lead plate. the vertical plane, including the central axis and tube axis, was decided upon by observing the symmetry of focal images. the central axis was designated as a line through the center of focus parallel to the target surface lying in the vertical plane. A method to determine the manipulation of the central axis in any direction is presented.

Radiography↗

Investigation of basic imaging properties in digital radiography 10. Structure mottle of II-TV digital imaging systems.

Single-frame images obtained with image intensifier (II)-TV digital systems contain a large amount of structure mottle. In the present study, we examined several II-TV digital systems by use of Wiener spectral analysis and noted considerable variation of the structure mottle over the wide spatial frequency range. We found that the structure mottle in these systems may originate in the input phosphor, the output phosphor, and/or the electronic components, and that the Wiener spectra of structure mottle seem to depend on the specific combination of these components. The results of observer performance studies indicated that structure mottle can significantly decrease the detection of low-contrast objects in a single-frame image when the exposure incident on the II is greater than approximately 0.1 mR. In addition, we showed that the structure mottle can be removed by subtraction of a uniformly exposed mask. This simple procedure will improve the quality of radiologic images obtained with II-TV digital systems. Note, however, that the structure mottle is largely eliminated by subtraction in digital subtraction angiography (DSA) images.

Humans↗

Investigation of basic imaging properties in digital radiography. 8. Detection of simulated low-contrast objects in digital subtraction angiographic images.

We investigated the effects of imaging and display conditions on the detectability of low-contrast objects in digital subtraction angiographic (DSA) images. The test images were produced by superimposition of low-contrast objects on a uniform noisy background obtained with a DSA system. We employed 18-alternative forced-choice (18-AFC) experiments and predictions based on statistical decision theory to study the dependence of the threshold contrasts of the test objects on the object size, incident x-ray exposure, display window width, and display medium. The results indicated that the threshold contrast decreased with increasing object size, and that the detectability of an object of a given size increased with increasing incident x-ray exposure and decreasing width of the display window. We found that the signal-to-noise ratio (SNR) obtained from the perceived statistical decision theory model, which includes the observer's internal noise, can accurately predict the detectability of low-contrast objects in DSA images. The threshold SNR corresponding to 50% correct detection in the 18-AFC experiments had a constant value of 3.8, in agreement with results reported previously for screen-film systems. The theoretical model will be useful for prediction of the performance of a DSA system based on its physical characteristics, and for evaluation of the tradeoff between patient exposure and diagnostic accuracy for a given DSA unit.

Angiography↗

Investigation of basic imaging properties in digital radiography. 9. Effect of displayed grey levels on signal detection.

Results of an 18-alternative forced-choice experiment have shown that observers were capable of detecting a signal with a contrast of 1 in terms of 10-bit data which were displayed on a CRT monitor with an 8-bit video generator and a window width setting of 1024. We investigated the conditions under which 10-bit signal data can be detected when displayed using an 8-bit video generator. Results show that the 10-bit digital quantum noise, which was approximately Gaussian distributed, can act as a carrier of the signal data, thus allowing a signal having a contrast of a fraction of a displayed grey level to be detected. We demonstrate the relationship between the rms value of the digital noise (obtainable with a clinical digital subtraction angiography system under various exposure levels), the number of bits available in the display video generator, and the "transmitted" signal contrast displayed on the CRT monitor.

Biometry↗

Investigation of basic imaging properties in digital radiography. 13. Effect of simple structured noise on the detectability of simulated stenotic lesions.

We investigated the effects of structured background noise on the detectability of stenotic lesions. Digital subtraction angiographic (DSA) images of stenotic blood vessels were simulated and superimposed onto uniform noise samples. Eighteen-alternative forced choice (18-AFC) experiments were employed to determine the detectability of the stenotic lesion in the structured-noise background of a blood vessel. In this study, the dependence of detectability on lesion size, vessel size, and incident x-ray exposure was examined. Our results indicate that the presence of structured noise in an image will reduce the detectability of a lesion. However, the relative performance of an observer when the lesion size and incident exposure were varied was the same with and without the presence of the structured background. Thus, conclusions obtained previously with regard to changes in the detectability of a lesion in the presence of uniform background noise can be applied directly to conditions in which simple structured anatomic background is present.

Angiography↗