Presentation Development of 3D measurement device dedicated for range-compensator QA

福田, 茂一

(Purpose)In carbon therapy, the broad-beam method is used to irradiate beams to the tumor conformally. The broaden beams are cut to the shape of the target tumor projected in the beam’s eye view by a patient collimator or MLC. To adjust the range of the beams to the target in the depth a range-compensator is used. The range-compensator is a block that has an engraved depression in the shape of the target tumor. Though it is desirable to check the 3D shape of the range-compensator compared to the planned shape at all points, over 2000 points, in terms of QA/QC, only the limited points, 30-40 points, are usually checked by the contact length measurement sensor device (CLMSD). To verify all points automatically in a short time, the 3D measurement device (3DMD) dedicated for range-compensators QA has been developed.(Methods)The 3DMD has a XY-stage with high precision and a range-compensator is attached to the XY-stage. Two CCD laser displacement sensors were employed to measure the height of each point of the range-compensator by detecting reflected laser. The one sensor was changed to another type of sensor to improve the precision of the measurements. We verified some range-compensators.(Results)Due to the shape there were some points which cannot be measured, but the ratio of the number of the unmeasured points to that of all points was less than 1%. The precision of the measurements by the new sensor was improved and the concave positions were verified as acceptable.(Conclusion)After further commissioning of the 3DMD, we plan to use this device to check the range-compensators routinely.
The 15th International Congress of Radiation Research (ICRR 2015)

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