Department of Radiation Oncology, Sun Yat-Sen University Cancer Center and State Key Laboratory of Oncology in Southern China, Guangzhou 510060, China
Int J Radiat Oncol Biol Phys. 2011 Aug 1;80(5):1581-8. doi: 10.1016/j.ijrobp.2010.10.063. Epub 2011 Jan 14.
A real-time dose verification method using a recently designed metal oxide semiconductor field effect transistor (MOSFET) dosimetry system was evaluated for quality assurance (QA) of intensity-modulated radiation therapy (IMRT).
Following the investigation of key parameters that might affect the accuracy of MOSFET measurements (i.e., source surface distance [SSD], field size, beam incident angles and radiation energy spectrum), the feasibility of this detector in IMRT dose verification was demonstrated by comparison with ion chamber measurements taken in an IMRT QA phantom. Real-time in vivo measurements were also performed with the MOSFET system during serial tomotherapy treatments administered to 8 head and neck cancer patients.
MOSFET sensitivity did not change with SSD. For field sizes smaller than 20 × 20 cm(2), MOFET sensitivity varied within 1.0%. The detector angular response was isotropic within 2% over 360°, and the observed sensitivity variation due to changes in the energy spectrum was negligible in 6-MV photons. MOSFET system measurements and ion chamber measurements agreed at all points in IMRT phantom plan verification, within 5%. The mean difference between 48 IMRT MOSFET-measured doses and calculated values in 8 patients was 3.33% and ranged from -2.20% to 7.89%. More than 90% of the total measurements had deviations of less than 5% from the planned doses.
The MOSFET dosimetry system has been proven to be an effective tool in evaluating the actual dose within individual patients during IMRT treatment.
使用最近设计的金属氧化物半导体场效应晶体管（MOSFET）剂量测定系统，评估一种实时剂量验证方法，用于强度调制放射治疗（IMRT）的质量保证（QA）。
在研究可能影响 MOSFET 测量准确性的关键参数（即源皮距[SSD]、射野大小、射束入射角和辐射能谱）之后，通过与在 IMRT QA 体模中进行的离子室测量进行比较，验证了该探测器在 IMRT 剂量验证中的可行性。还在对 8 例头颈部癌症患者进行的连续调强治疗期间，使用 MOSFET 系统进行了实时体内测量。
MOSFET 灵敏度随 SSD 而变化。对于小于 20×20cm2 的射野大小，MOFET 灵敏度变化在 1.0%以内。探测器角度响应在 360°内为各向同性，在 6-MV 光子能量谱变化引起的灵敏度变化可以忽略不计。MOSFET 系统测量值和离子室测量值在 IMRT 体模计划验证中的所有点都一致，误差在 5%以内。8 例患者中 48 例 IMRT MOSFET 测量剂量与计算值之间的平均差值为 3.33%，范围为-2.20%至 7.89%。超过 90%的总测量值与计划剂量的偏差小于 5%。
MOSFET 剂量测定系统已被证明是一种在 IMRT 治疗期间评估个体患者实际剂量的有效工具。
