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Biomedical subjects

T Nishidai

Publications and source records attributed to T Nishidai.

54 records · Page 3Linked to original sources
PubMed1978

[Determination of thorotrast amount deposited in patients (author's transl)].

Thorotrast amount deposited in patients, chiefly in the liver and the spleen, was determined with a NaI detector and a Computerised Axial Tomography (CT). In the measurement of the gamma-rays with the NaI detector, the geometry-factors, that are the distance from the detector to the source, the attenuation of the gamma-rays in the tissue and the shapes of the liver and the spleen, were studied, and the mean amount deposited in the organs was determined. In the measurement with CT, the relationship of CT-Number and the amount of thorium was got, and the localized amount and the distribution in the organ were measured.

Gamma Rays↗
PubMed1978

Significance of tumor volume and blood flow in tumor control by radiation.

The mean rate of blood flow in C3H/He mouse mammary carcinoma determined by the clearance of 133Xe was 0.1 ml/g/min in tumors greater than approximately 2.0 cm3, and then blood flow became increasingly greater as the tumor size decreased further. The dose required to produce lethal damage in the tumor increased with the size of the tumors. In large tumors the control rate increased with increasing doses to a maximum at a certain level; at higher doses the rate was somewhat decreased. The present experiments show that changes in blood flow could account for radiosensitivity of the tumor, and a tumor larger than a certain volume can no longer be controlled by a single dose of radiation.

Animals↗
PubMed1977

Trials of new forms of radiotherapy for locally advanced bronchogenic carcinoma. Irradiation under 95% O2 plus 5% CO2 inhalation, uneven fractionation irradiation and intraoperative irradiation.

In order to improve the survival rate of patients with clinically inoperable but localized bronchogenic carcinoma, we have developed the following three forms of radiotherapy and analyzed the results in comparison with those obtained by conventional radiotherapy: 1. Irradiation under 95% O2 plus 5% CO2 inhalation, 2. Uneven fractionation irradiation, 3. Intraoperative irradiation. The tumor regression rate was most pronounced in the 95% O2 plus 5% CO2 breathing group and the one-year survival rate was significantly increased. However, the longterm survival rate was almost the same as that of patients treated by conventional radiotherapy. In uneven fractionation irradiation, the follow-up period is short, but the preliminary results seem most encouraging. Intraoperative irradiation is well indicated for patients with poor pulmonary functions, in whom the localized malignant lesions were left behind following excision of the main mass. The reason is that a cancerocidal dose can be delivered directly to the unresectable remnants without affecting normal structures.

Adult↗
PubMed1976

Radiation therapy in the treatment of glioblastoma.

A retrospective study of 127 cases irradiated for glioblastoma was made to assess the role of radiation therapy and to determine the optimal technique of radiation therapy. The over-all survival rates of our series were 52 percent at one year, 19 percent at three years, and twelve percent at five years after radiation therapy. Survival time of the patients is influenced by various factors other than treatment: age, sex, histologic grading, duration of symptoms, and location of tumor. Among these factors, the location of the tumor was the most important in our present series. Surgical treatment can extend the survival time. More extensive resection results in longer survival, provided that the location of the tumor allows such a surgical procedure. Radiation therapy can prolong the survival time of those with glioblastoma, but a high tumor dose of more than 6,000 rads or 1,700 rets is necessary to improve the prognosis significantly. Therefore, irradiation should be administered through generous fields according to the extent of the tumor under precise planning to determine the accurate localization and extent of the tumor.

Adolescent↗
PubMedDate not supplied

Laser projection system for radiotherapy and CT-guided biopsy.

We devised a laser projection system combined with a CT scanner and radiotherapy treatment planning computer (CT stimulator). The irradiation field can be projected over a range of 180 degrees on the skin of a patient lying on the CT couch. For CT-guided biopsy, the system can project the skin entry point and needle direction.

Biopsy, Needle↗
PubMedDate not supplied

Influence of scattered radiation on heterogeneity correction in three-dimensional treatment planning.

The first and multiple scattered radiations of 60Co gamma rays and 10 MV X-rays were measured using an ionization chamber, and the values obtained were compared with the calculated values. The experimental values of the angle distributions of the first scattered photons from tissue-equivalent materials in free space agreed well with the theoretical values calculated from the Klein-Nishina probability in the compton scattering process. However, the scattered radiation in phantoms was not represented by only the first scatter components. The results indicate that the weighting factor of all scattered radiations in the calculated three-dimensional dose distribution can be set by the inverse square correction for the distance from the scattering point to the reference point within an accuracy required in clinical dosimetry. The present method provides a simple and practical approach to obtaining the computation speed in three-dimensional treatment planning.

Cobalt Radioisotopes↗
PubMedDate not supplied

Studies in radiosensitizing effects of misonidazole and SR-2508 on C3H/He mouse mammary tumors.

The radiosensitizing efficacy of SR-2508, a new 2-nitroimidazole, which is less neurotoxic than misonidazole (MISO) was studied using transplantable mammary carcinoma of C3H/He mice. Tumor responses to treatments were evaluated by growth-delay time assay. In single irradiations, the enhancement ratios of 0.5 mmole/kg of MISO and 1.5 mmole/kg of SR-2508, which were equitoxic to C3H/He mice, were 1.42 and 1.84 respectively. In fractionated irradiations with three fractions over two days or five fractions over four days, the enhancement ratios of 1.5 mmole/kg of SR-2508 were 1.40 and 1.34 respectively. On the other hand the enhancement ratios of MISO at the above mentioned dose in respective fractionated irradiations were 1.15 or 1.11. SR-2508 is considered promising as a hypoxic cell radiosensitizer for clinical use.

Animals↗