Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.
Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.
J Appl Clin Med Phys. 2019 Sep;20(9):149-156. doi: 10.1002/acm2.12707. Epub 2019 Aug 28.
To investigate the angular dependency of the W1 scintillator with and without a magnetic field, the beam incidence angles to the detector varied from 0° to 360° at intervals of 30° when the detector was pointed in both the craniocaudal and right-to-left directions. The beam incidence angles also varied from 0° to 360° at intervals of 45° when the W1 scintillator was in the anterior-to-posterior direction. To investigate the field size dependency of the W1 scintillator with and without a magnetic field, the doses by an identical beam-on time were measured at various square field sizes and the measured doses were normalized to the dose at the field of 10.5 cm × 10.5 cm (FS10.5). With and without a magnetic field, the deviations of the doses to the dose at the beam incident angle of 0° were always less than 1% regardless of the dosimeter positioning relative to the magnetic field direction. When the field sizes were equal to or less than FS10.5, the differences in the output factors with and without a magnetic field were less than 0.7%. However, those were larger than 1% at fields larger than FS10.5, and up to 3.1%. The W1 scintillator showed no angular dependency to the magnetic field. Differences larger than 1% in the output factors with and without a magnetic field were observed at field sizes larger than 10.5 cm × 10.5 cm.
为了研究 W1 闪烁体在有磁场和无磁场情况下的角度依赖性，当探测器指向颅尾和左右方向时，以 30°的间隔从 0°到 360°改变束入射角；当 W1 闪烁体处于前后方向时，束入射角也以 45°的间隔从 0°到 360°改变。为了研究 W1 闪烁体在有磁场和无磁场情况下的射野尺寸依赖性，在各种方形射野尺寸下，以相同的束照射时间测量剂量，并将测量的剂量归一化为 10.5cm×10.5cm（FS10.5）射野的剂量。无论剂量仪相对于磁场方向的定位如何，有磁场和无磁场时，束入射角为 0°的剂量偏差始终小于 1%。当射野尺寸等于或小于 FS10.5 时，有磁场和无磁场时的输出因子差异小于 0.7%。然而，在射野大于 FS10.5 时，这些差异大于 1%，最大可达 3.1%。W1 闪烁体对磁场没有角度依赖性。在射野尺寸大于 10.5cm×10.5cm 时，有磁场和无磁场时的输出因子差异大于 1%。
