| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that an output radiation dose and a dose distribution in an irradiation field can be monitored in a real time during treatment in a medical linac but there is no means for monitoring radiation energy exerting effect on the dose distribution in a depth direction in a real time during treatment. SOLUTION: The dose distributions in the irradiation fields formed on a beam axis and in the peripheral part of the beam axis are changed when radiation energy is changed. This change is utilized to monitor the ratio of doses by the electrode (8) arranged on the beam axis and the dose distribution monitoring electrodes (5a, 5b, 5c and 5d) arranged in the periphery of the electrode (8) so as to be symmetric with respect to the beam axis and the present value of radiation energy is calculated using the relation between a dose ratio predetermined by measurement and the change of radiation energy. COPYRIGHT: (C)2003,JPO
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