Improved spatial resolution by MOSFET dosimetry of an x‐ray microbeam

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Abstract
Measurement of the lateral profile of the dose distribution across a narrow x‐ray microbeam requires a dosimeter with a micron resolution. We investigated the use of a MOSFET dosimeter in an “edge‐on” orientation with the gate insulating oxide layer parallel to the direction of the beam. We compared results using this technique to Gafchromic film measurements of a 200 micrometer wide planar x‐ray microbeam. The microbeam was obtained by using a vernier micrometerdriven miniature collimator attached to a Therapax DXT300 x‐ray machine operated at 100The “edge‐on” application allows utilization of the ultra thin sensitive volume of the MOSFET detector. Spatial resolution of both the MOSFET and Gafchromic film dosimeters appeared to be of about 1 micrometer. The MOSFET dosimeter appeared to provide more uniform dose profiles with the advantage of on‐line measurements.