Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
Phys Med. 2024 Jul;123:103403. doi: 10.1016/j.ejmp.2024.103403. Epub 2024 Jun 12.
Although plastic scintillator detectors (PSDs) are considered ideal dosimeters for small field dosimetry in conventional linear accelerators (linacs), the impact of the magnetic field strength on the response of the PSD must be investigated.
A linac Monte Carlo (MC) head model for a low-field MR-linac was validated for small field dosimetry and utilized to calculate field output factors (OFs). The MC-calculated OFs were compared with the treatment planning system (TPS)-calculated OFs and measured OFs using a Blue Physics (BP) Model 10 commercial PSD and a synthetic diamond detector. The field-specific correction factors, [Formula: see text] , were calculated for the PSD in the presence of a 0.35 T and magnetic field. The impact of the source focal spot size and initial electron energy on the MC-calculated OFs was investigated.
Good agreement to within 2 % was found between the MC-calculated OFs and BP PSD OFs except for the 0.415 × 0.415 cm field size. The BP PSD [Formula: see text] correction factors were calculated to be within 1 % of unity. For field sizes ≥1.66 × 1.66 cm, the MC-calculated OFs were relatively insensitive to the focal spot size and initial electron energy to within 2.5 %. However, for smaller field sizes, the MC-calculated OFs were found to differ up to 9.50 % and 7.00 % when the focal spot size and initial electron energy was varied, respectively.
The BP PSD was deemed suitable for small field dosimetry in MR-linacs without requiring any [Formula: see text] correction factors.
尽管塑料闪烁体探测器（PSD）被认为是传统线性加速器（linac）中小野剂量测量的理想剂量计，但必须研究磁场强度对 PSD 响应的影响。
为低场 MR-linac 的 linac 蒙特卡罗（MC）头部模型进行了小野剂量验证，并利用该模型计算了场输出因子（OFs）。将 MC 计算的 OFs 与治疗计划系统（TPS）计算的 OFs 和使用 Blue Physics（BP）Model 10 商业 PSD 和合成金刚石探测器测量的 OFs 进行了比较。计算了 PSD 在存在 0.35T 和磁场时的特定场校正因子[Formula: see text]。研究了源焦点尺寸和初始电子能量对 MC 计算的 OFs 的影响。
MC 计算的 OFs 与 BP PSD OFs 之间的差异在 2%以内，除了 0.415×0.415cm 的场尺寸外。BP PSD [Formula: see text]校正因子计算值在 1%以内。对于大于等于 1.66×1.66cm 的场尺寸，MC 计算的 OFs 对焦点尺寸和初始电子能量的变化相对不敏感，在 2.5%以内。然而，对于较小的场尺寸，当焦点尺寸和初始电子能量分别变化时，MC 计算的 OFs 发现差异高达 9.50%和 7.00%。
BP PSD 被认为适合于 MR-linac 中的小野剂量测量，无需任何[Formula: see text]校正因子。
