Divyalakshmi Janahiraman, Rafic K Mohamathu, Babu Ebenezer Suman, Balasingh Timothy Peace, Sebastin Amalan, Sujith Christopher J, Raj L Jose Solomon
Department of Radiation Oncology, Christian Medical College, Vellore, Tamil Nadu, India.
Regional Cancer Centre, Govt. Rajaji Hospital, Madurai, Tamil Nadu, India.
Rep Pract Oncol Radiother. 2021 Dec 30;26(6):1019-1028. doi: 10.5603/RPOR.a2021.0117. eCollection 2021.
The aim of the study was to investigate the dosimetric feasibility of using optically stimulated luminescence dosimeters (OSLD) and an electronic portal imaging device (EPID) for central axis (CA X) and off-axis (OAX) dosimetric leaf gap (DLG) measurement.
The Clinac 2100C/D linear accelerator equipped with Millennium-120 multileaf collimator (MLC) and EPID was utilized for this study. The DLG values at CA X and ± 1 cm OAX (1 cm superior and inferior to the CA X position, respectively along the plane perpendicular to MLC motion) were measured using OSLD (DLG) and validated using ionization chamber dosimetry (DLG). The two-dimensional DLG map (2D DLG) was derived from the portal images of the DLG plan using a custom-developed software application that incorporated sliding aperture-specific correction factors.
DLG and DLG, though measured with diverse setup in different media, showed similar variation both at CA X and ± 1 cm OAX positions. The corresponding DLG values derived using aperture specific corrections were found to be in agreement with DLG and DLG. The 2D DLG map provides insight into the varying patterns of the DLG with respect to each leaf pair at any position across the exposed field.
Commensurate results of DLG with DLG values have proven the efficacy of OSLD as an appropriate dosimeter for DLG measurement. The 2D DLG map opens a potential pathway to accurately model the rounded-leaf end transmission with discrete leaf-specific DLG values for commissioning of a modern treatment planning system.
本研究的目的是探讨使用光激励发光剂量仪（OSLD）和电子射野影像装置（EPID）进行中心轴（CA X）和离轴（OAX）剂量学叶片间隙（DLG）测量的剂量学可行性。
本研究使用配备了Millennium - 120多叶准直器（MLC）和EPID的Clinac 2100C/D直线加速器。使用OSLD（DLG）测量CA X以及±1 cm OAX（分别沿垂直于MLC运动平面在CA X位置上方和下方1 cm处）的DLG值，并使用电离室剂量学（DLG）进行验证。二维DLG图（2D DLG）是通过使用一个定制开发的软件应用程序从DLG计划的射野图像中得出的，该软件应用程序纳入了特定于滑动孔径的校正因子。
尽管DLG和DLG是在不同介质中采用不同设置测量的，但在CA X和±1 cm OAX位置均显示出相似的变化。发现使用特定孔径校正得出的相应DLG值与DLG和DLG一致。2D DLG图提供了关于在整个照射野的任何位置上各叶对的DLG变化模式的见解。
DLG与DLG值的相应结果证明了OSLD作为DLG测量的合适剂量仪的有效性。2D DLG图为使用离散的特定叶DLG值准确模拟圆形叶端透射开辟了一条潜在途径，用于现代治疗计划系统的调试。
