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Biomedical subjects

T Nishidai

Publications and source records attributed to T Nishidai.

At least 37 records · Page 2Linked to original sources
PubMed1985

[Physical dose distribution].

In radiotherapy planning it is essential to compose dose distribution curves on a transverse section of patient. For this purpose we have developed the radiotherapy planning system using a computer (Modulex), in which CT images and CT numbers were input on off-line with a CT magnetic tape, CT numbers were converted into relative electron densities and then, dose distribution curves calculated were output directly on CT images. One of problems lying in this system was that the three-dimensional dose distribution had to be surmised with a couple of two-dimensional ones. Clinical application of this system has been applied to planning of intraoperative radiotherapy that was considered to provide ideal dose distributions, and its effectiveness was discussed.

Computers↗
PubMed1983

Time dependence of response of transplanted mouse mammary tumors to single or split radiation doses.

The effect of single and different split radiation doses with varying rates and time intervals was investigated in an experimental system in vivo using second generation isotransplants of two mouse mammary carcinomas. The changes in the growth delay time (GDT) and tumor control rate (TCR) were analyzed, and explained by a dose dependence of the repair of sublethal radiation damage, reoxygenation and cellular repopulation in the tumors. A direct relationship was found between the size of the first of two dose fractions and the time interval between two exposures at which treatment with split doses is most effective in delaying or preventing tumor growth. Multiple exposures to unequal dose fractions are more effective than to equal fractions with the same total dose.

Animals↗
PubMed1983

[Recent advances in hypoxic cell radiosensitizer].

The comparative studies on the radiosensitizing efficacy of misonidazole (MISO) and SR-2508, a new 2-nitroimidazole which is less neurotoxic than MISO, were performed using C3H/He mouse mammary tumors. The enhancement ratios of 1.42 for 0.5 mmole/kg of MISO and 1.82 for 1.5 mmole/kg of SR-2508, the equitoxic dose to MISO, were obtained when each drug was administered in combination with a single dose of radiation. When the radiation was delivered in three and five fractions, enhancement ratios decreased to 1.15 and 1.11 for MISO while they remained at 1.40 and 1.34 for SR-2508 respectively. Potentiating effect of diethyl maleate (DEM) on the radiosensitization of MISO was also studied using the same experimental tumor. Although DEM, in itself, has a radiosensitizing effect in the dose range of more than 600mg/kg combined use of DEM and MISO showed more efficient synergism, e.g., the enhancement ratio of 0.5 mmole/kg of MISO increased from 1.42 to 2.06 when it was given in combination with 760 mg/kg of DEM. However, synergistic effects of MISO and DEM observed were dependent upon given dose of each drug. i.e.

Animals↗
PubMed1983

[Biological and physical approach to the improvement of radiotherapy].

A double blind trial of misonidazole (MISO) was undertaken. A total of 147 patients were enrolled. They were randomly allocated into two groups receiving either MISO or placebo. They were irradiated with 2 Gy 5 times a week to a total dose of about 60 Gy. 0.5g/m2 of MISO was given orally 4 hours before each irradiation. The effect of the treatment was evaluated as a decrease in the volume of the tumors. No radiosensitizing effect of the drug was observed. Twenty-nine tumors considered to be radioresistant were treated by RF hyperthermia combined with radiation. 48% of the tumors developed complete regression. No definite relationship between heat sensitivity of the tumors and their histological types was observed.

Animals↗