Variation of dose distribution by detectors for narrow beam

Percentage depth dose (PDD) is the essential parameter for the absorbed dose determination. Since precise measurement is required for narrow beam especially, several kinds of detectors are commonly used to measure dose distribution for the narrow beam. However, the variation of response caused by kinds of the detectors has not been investigated precisely. In this study, PDDs were measured using several kinds of detectors, such as ionization chambers, silicon diode detectors and films. Furthermore, the absorbed dose of these detection materials in water was calculated using Monte Carlo simulation. As a result, it was shown that the response of ionization chambers (air-gas) was higher than diode detectors (silicon) and a film (photoemulsion). Therefore, the depth dose curves changed by kinds of the detector (materials). (author)