Pasma K L, Heijmen B J, Kroonwijk M, Visser A G
Department of Clinical Physics, Daniel den Hoed Cancer Center/University Hospital Rotterdam, The Netherlands.
Med Phys. 1998 Jun;25(6):830-40. doi: 10.1118/1.598293.
A method is presented for calculation of transmission functions for high energy photon beams through patients. These functions are being used in our clinic for prediction of portal dose images (PDIs) which are compared with PDIs measured with an electronic portal imaging device (EPID). The calculations are based on the planning CT-scan of the patient and on the irradiation geometry as determined in the treatment planning process. For each beam quality, the required input data for the algorithm for transmission prediction are derived from a limited number of measured beam data. The method has been tested for a PDI-plane at 160 cm from the focus, in agreement with the fixed focus-to-detector distance of our fluoroscopic EPIDs. For 6, 23 and 25 MV photon beams good agreement (approximately 1%) has been found between calculated and measured transmissions through anthropomorphic phantoms.
本文提出了一种计算高能光子束通过患者的传输函数的方法。这些函数在我们的临床中用于预测门静脉剂量图像（PDI），并与使用电子门静脉成像设备（EPID）测量的PDI进行比较。计算基于患者的计划CT扫描以及治疗计划过程中确定的照射几何形状。对于每种射束质量，传输预测算法所需的输入数据来自有限数量的测量射束数据。该方法已在距焦点160 cm处的PDI平面上进行了测试，这与我们的荧光透视EPID的固定焦点到探测器距离一致。对于6、23和25 MV光子束，通过人体模型计算和测量的传输之间发现了良好的一致性（约1%）。
