Search PubMed⌕ Search

Biomedical subjects

Y Onai

Publications and source records attributed to Y Onai.

At least 19 recordsLinked to original sources
PubMed1990

[Physical considerations on the method for improving the outcome of radiation therapy].

The outcome of radiation therapy is closely related to the dose that has been delivered to the target volume and the organs at risk. In this report, sources of errors in dose delivery and their magnitudes at each step of radiation therapy from data acquisition of patient to execution of irradiation, and the methods for reducing the errors are discussed. The influences of systematic or random errors in the target dose level and of dose inhomogeneities throughout the target volume on the dose-effect curve are also described. To improve the outcome of radiation therapy, a constant effort from radiotherapists, physicists and technicians is required for reducing the systematic and random errors at each step of radiation therapy.

Artificial Intelligence↗
PubMed1985

[Physical aspects of standardization and optimization in radiotherapy].

Establishment of a quality assurance program of radiotherapy is required for the standardization and optimization of radiotherapy. Items to include in the quality assurance program are discussed briefly such as: evaluation of radiation dose, test of performance characteristics of radiotherapy equipments, system to prevent mistakes in delivery of radiotherapy, dose specification, method of statistical procedure and analysis of treatment results of patients, members of the radiation treatment planning team.

Humans↗
PubMed1978

[A new method for elimination of artifacts produced by collimator septum effect in gamma-camera images (author's transl)].

Collimator artifacts may be present within the images produced by collimators whose septal width approaches the inherent resolution of the gamma-camera system. As the inherent resolution of the gamma-camera is improved, collimator artifacts become more prominent. The purpose of this study is to eliminate collimator artifacts from gamma-camera images. To eliminate the septum effect produced by high-energy parallel-hole collimators with thick septa, the following method was used: X and Y signals from the detector are made to ride on the triangular waves changing periodically, and resultant position signals obtained by this processing are applied to the corresponding deflection circuits in the CRT display. The oscillation amplitude of processed position signals can be regulated by the frequency and amplitude of the triangular waves. Regulation of the oscillation amplitude of position signals, which would produce maximum reduction of collimator artifacts, was to approach the spatial frequency responses of the overall processed line spread functions obtained experimentally to those of the Gaussian functions with FWHM equal to the geometric resolution calculated from the equation given by Gerber and Miller. In images of a pancreas phantom containing 131I, collimator artifacts were clearly seen in the unprocessed case, but were eliminated in the processed case.

Models, Theoretical↗