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Biomedical subjects

S Urahashi

Publications and source records attributed to S Urahashi.

15 recordsLinked to original sources
PubMed2002

[Report on the 13th European Congress of Radiology (ECR): Comparison of primary proton beams and secondary charged-particles].

PURPOSE: In the proton radiotherapy, primary proton beams contribute to the absorbed dose and the share of secondary charged-particles is small. The purpose is to discuss about the ratio of average dose of primary proton beams and secondary charged-particles. METHODS: We performed the dosimetry of 70 MeV proton beams in water using ionization chamber. The ratio of average dose for secondary charged-particles in some range shifter was calculated by the dose ratio of primary and scatter. To exclude the influence of lateral secondary charged-particles, the ratio of average dose for secondary charged-particles was extrapolated to zero field size of each. RESULTS: The ratio of average dose for secondary charged-particles was extrapolated to zero field size by the bi-exponential fit. The ratio of average dose for longitudinal secondary charged-particles for zero fields at each depth is almost the same; the different at the shallow depth is decreased. CONCLUSIONS: The secondary charged-particles from collimator is affected by the dose of shallow depth. The influence of lateral secondary charged-particles in water phantom was excluded with the extrapolation method for zero field size in each depth.

Alpha Particles↗
PubMed1994

[MR lymphography: first application to human].

First clinical trial of MR lymphography is described. The subjects were two normal volunteers. The contrast agent was cideferron, which was an iron colloid. We obtained MR images of the inguinal lymph nodes before and after subcutaneous injection of the agent in the dorsal feet. As a result, the signal intensities on T2 weighted images remarkably decreased at two hours after injection and kept low until three months after. Although pigmentation around the injection site was observed, it was gradually fading within six months. In conclusion, MR lymphography with cideferron can be applied clinically.

Colloids↗
PubMed1994

Inhalation MR lymphography: a new method for selective enhancement of the lung hilar and mediastinal lymph nodes.

On MR lymphography, a new approach to the lung hilar and mediastinal nodes was developed in an animal model. Five rabbits were made to inhale iron colloid (cideferron) that was nebulized to aerosol. Two days after inhalation of the agent, the mediastinal lymph nodes decreased in signal on SE 2000/30 and SE 2000/60 images and proved to have iron on histological evaluation, whereas the popliteal nodes did not have any iron. Experimental results indicate that inhalational administration can deliver the agent to the pulmonary lymphatic system and has the potential of lung hilar and mediastinal MR lymphography.

Administration, Inhalation↗
PubMed1993

[Results of electron beam irradiation for tongue cancer].

One hundred and eighty three patients with squamous-cell carcinoma of the tongue were treated with electron beam irradiation at the Dept. of Radiology, Nihon University School of Medicine, from 1967 to 1988. We analyzed the therapeutic results of the investigation to find out indications of squamous-cell carcinoma of the tongue to see if it could be treated by intra-oral cone irradiation with electron beam (IOC). The patients were restaged, as follows: stage I, 38 cases: stage II, 64 cases: stage III, 58 cases: stage IV, 23 cases. There were 113 males and 70 females, ranging in age from 18 to 87 years old. IOC was applied for T 1 or smaller T 2 cases. External neck irradiation and IOC were combined for larger T 2, T 3 or T 4 cases. The two-year local-control rates for primary lesions with the present method were 85% for T 1, 73% for T 2, and 58% for T 3. There were no two-year local-control cases for T 4. Clinical feature of the tumor were classified into tumourous type, small ulcerating type, and large ulcerating type. The two-year local-control rates were as follows: 80% for tumorous types, 68% for small ulcerating types and 53% for large ulcerating types. Uneven fractionated irradiation was performed on 144 cases and even fractionated irradiation was performed on 39 cases. The two-year local-control rates were as follows: 68% for uneven fractionated irradiation cases, 61% for even fractionated irradiation. In T 2 and T 3 cases, the two-year local-control rates were as follows: 77%, 63% for uneven fractionated irradiation cases, 56%, 40% for even fractionated irradiation cases. The two-year local-control rates were increased by uneven fractionated irradiation for T 2, T 3 cases (P < 0.05). We analyzed the therapeutic results in details for T 3 cases. T 3 patients were classified into two categories according to tumor size (category 1: long axis X short axis > 1000mm2: category 2: long axis X short axis < or = 1000mm2). The two-year local-control rates were 48% for category 1, and 72% for category 2. T 3 patients were classified into two categories according to clinical feature of the tumor (tumors with ulcers and tumors without ulcers). The two-year local-control rates were 43% with ulcers, and 74% without ulcers. The actuarial five-year survival rates were 92% for stage I, 72% for stage II, 67% for stage III, and 12% for stage IV.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1990

[A preliminary study on MR lymphography with iron chondroitin sulfate colloid].

We investigated MR lymphography with iron chondroitin sulfate colloid, which was an intravenous agent for iron deficiency anemia. MR images (SE350/30) of the medial iliac lymph nodes were obtained before and after subcutaneous++ injection of this agent (2 mg Fe) on dorsal hindfeet bilaterally in five rabbits (3.0 kg weight). Signal intensities of the nodes were increased 5-15 minutes after the injection and the nodes were clearly identified in three of them. In the other two, increase in the signal intensity was not shown and any nodes could not be detected macroscopically at the investigated region on dissection. These results indicated the possibility of positive contrast enhancement of lymph nodes on MR imaging using iron colloid.

Animals↗
PubMed1987

[Uneven fractionation irradiation].

To get the better therapeutic ratio with low LET radiation therapy alone, the improvement of the physical dose distribution and the mode of dose fractionation are required. Since 1972, uneven fractionation irradiation with electron beam has been used for head and neck tumors. The 2 year control rates for primary tongue cancer T1, T2 and T3 by this method were approximately comparable to that of the small source implantation. In the treatment results for the cervical lymph node metastasis, uneven fractionation technique is superior to conventional one. Furthermore, this results was reviewed by means of multivariate analysis.

Analysis of Variance↗
PubMed1979

Changes in optic glass-fibers due to X-ray irradiation.

The purpose of this study was to clarify the relationship between x-ray irradiation and changes in the functional properties of flexible fiberscopes. Scanning electron microscopy, electron spin resonance, and thermoluminescent dosimetry techniques were used to determine the nature of the changes and their possible reversibility. Decreases in light transmission were observed at exposures above 5 roentgens (R), color changes were observed above 25 R, and electron spin resonance absorption changes occurred above 100 R. These changes were proportional to the x-ray doses. The x-ray exposure rates of the segmental and the subsegmental bronchi are about 20 percent that of the patient's thoracic skin surface. The above-mentioned studies showed that, for optimal results, a fiberscope should not be exposed to more than 15 minutes of fluoroscopy by a TV apparatus per week.

Bronchoscopes↗