| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2006: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 2005: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2004: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Research Abstract |
Using a plastic scintillating plate, a CCD camera, and a wedge-type range shifter(WRS), we produced a distal-shaped and distal-position detector capable of measuring depth dose distribution in range-scanning technique. At the 2^<nd> exposure room in the proton medical research center (PMRC), University of Tsukuba, we took basic data concerned with characteristics of dose profiles in the proton beam. Measuring charges recorded on the dose monitors (M1 and M2) in the proton beam line, charges on the reference dose meter (M3) setup on the isocenter, and charges on the CCD elements viewing the scintillating plate (SciCCD) just behind M3, we compared the depth dose distributions obtained by SciCCD to those done by the reference M3. They revealed a quenching effect; 15% light-yield reduction at maximum at the Bragg peak and in the high LET regions of 20-mm measured from the distal edge. This effect was confirmed as well as in the regions of the 50-mm width SOBP and the depth dose distribution produced with the bolus and collimator. In the comparison among the depth dose distributions obtained using SciCCD and M3 detectors, and calculated with the pencil beam algorithm (PBA) in the treatment planning program, we revealed difference in detailed shapes of the distribution and importance of more accurate positioning methods as well as correction of quenching effects. Installing an automatic control system to the WRS system is expected to improve data taking speeds and to provide various kinds of dose distribution. The scintillating plate and the CCD camera were applied to the isocenter verification system at PMRC. This system improved measurement time to 30-min, the one-forth of the conventional method, without degradation in accuracy of ±0.1 mm.
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