Yutaka Okumura

MODIFICATION OF DOSE DISTRIBUTION IN HIGH-ENERGY ELECTRON BEAM TREATMENT.

A method to modify the dose distribution of high-energy electron beams of betatrons operating in the 4- to 31-MeV energy range was successfully applied to cases of carcinoma of the buccal mucosa, using 10- to 16-MeV energy. Marked radiation reaction occurred only in the area of the lesion. No visible reaction was seen in other parts of the oral cavity. Two of 3 lesions improved and showed no evidence of disease one and one-half years after completion of treatment.

Scattering Foil Device for High-Energy Electron-Beam Therapy

During the past decade, treatment-planning for high-energy electron-beam therapy has progressed along various lines to achieve homogeneous irradiation of tumor, with minimum damage to surrounding normal tissue. One of the most frequently used methods is an absorption technic in which a water-equivalent substance is interposed in the end of a collimator system (8, 11, 13, 14, 16–18). The distribution of beam intensity is thus well adjusted to the individual case for any single fixed field. With the absorbing material in the end of a treatment cone, however, the limited skin-sparing effect is lost because of secondary radiation. The benefits of high-energy radiation without the disadvantage of such absorbing material are desirable. This is a report of an evaluation of a special device consisting of scattering foil to alter the intensity of the betatron electron beam. Isodose curves for clinical use were measured and compiled. Method A betatron3 operating in the 4 to 31 MeV energy range was used in this stud...

In vivo Distributions of 111In and/or 3H Labeled Lymphocyte in C3H/He Mouse

Although 99mTc and 51Cr have been used for lymphocyte labeling, these radionuclides have several disadvantages for study on immunological behaviour of lymphocyte; very high rate elution and low labeling efficiency for both radionuclides, and short half life for 99mTc. Indium-111 has quite suitable physical properties for clinical nuclear medicine, i.e. desirable photon energy (247,173 keV) and 2.8 day half life. 111In-oxine is lipid soluble and is known to pass through the cell membrane and attaches firmly to cytoplasmic component of the cell. On the other hand, 3H-thymidine is well known substance which incorporated to nucleic acid in the cell. In this study, distribution patterns of 111In-oxine and/or 3H-thymidine labeled lymphocyte in C3H/He mice were examined and the suitability of 111In-oxine labeled lymphocyte for radionuclide imaging in vivo was discussed. Thirty minutes after intravenous injection of 3H and/or 111In labeled lymphocyte, about 12% of lymphocyte were found in the lungs and rest of them were distributed mainly in the blood, kidneys and liver. After 24 hours the activity in the lung decreased markedly and the activity in the liver and kidneys increased with time. Between lymphocyte labeled with 111In-oxine and 3H-thymidine, there is not so much differences in terms of distribution patterns. From this study, it is concluded that the 111In-oxine labeled lymphocyte distributes in the same way as 3H labeled one, in spite of different labeling sites. This 111In-oxine labeling method can be used as a useful tool of radionuclide imaging in kinetic studies of lymphocyte in vivo.

Correction of Dose Distribution for Air Space in High-Energy Electron Beam Therapy

Abstract A simple correction of the dose distribution of an electron beam for the oblique incidence is to shift the standard isodose curves the distance of the air space. The error of the corrected distribution from the measured one was more than 10% when the space was more than 3 cm. The electron beam diverged approximately in accordance with the inverse-square law when the scattering foil was assumed to be the virtual source. Correction of the air space shifting and the inverse square law resulted in an error less than 3%.