Deshpande Shrikant, Sathiyanarayanan V K, Bhangle Janhavi, Swamy Kumara, Basu Sumit
Department of Radiation Oncology, Ruby Hall Clinic, Pune, India.
J Med Phys. 2007 Apr;32(2):51-5. doi: 10.4103/0971-6203.33240.
The intensity-modulated radiation therapy (IMRT) planning is performed using the Konrad inverse treatment planning system and the delivery of the treatment by using Siemens Oncor Impression Plus linear accelerator (step and shoot), which has been commissioned recently. The basic beam data required for commissioning the system were generate. The quality assurance of relative and absolute dose distribution was carried out before clinical implementation. The salient features of Konrad planning system, like dependence of grid size on dose volume histogram (DVH), number of intensity levels and step size in sequencer, are studied quantitatively and qualitatively.To verify whether the planned dose [from treatment planning system (TPS)] and delivered dose are the same, the absolute dose at a point is determined using CC01 ion chamber and the axial plane dose distribution is carried out using Kodak EDR2 in conjunction with OmniPro IMRT Phantom and OmniPro IMRT software from Scanditronix Wellhofer. To obtain the optimum combination in leaf sequencer module, parameters like number of intensity levels, step size are analyzed. The difference between pixel values of optimum fluence profile and the fluence profile obtained for various combinations of number of intensity levels and step size is compared and plotted. The calculations of the volume of any RT structure in the dose volume histogram are compared using grid sizes 3 mm and 4 mm. The measured and planned dose at a point showed good agreement (<3%) except for a few cases wherein the chamber was placed in a relatively high dose gradient region. The axial plane dose distribution using film dosimetry shows excellent agreement (correlation coefficient >0.97) in all the cases. In the leaf sequencer module, the combination of number of intensity level 7 with step size of 3 is the optimal solution for obtaining deliverable segments. The RT structure volume calculation is found to be more accurate with grid size of 3 mm for clinical use.Thus a study regarding various aspects of commissioning of the Konrad inverse planning system for IMRT has been presented, which has been implemented in our clinic.
调强放射治疗（IMRT）计划使用康拉德逆向治疗计划系统进行，治疗则通过最近调试完成的西门子Oncor Impression Plus直线加速器（步进和射野）来实施。生成了调试该系统所需的基本射束数据。在临床实施前对相对和绝对剂量分布进行了质量保证。对康拉德计划系统的显著特征，如网格大小对剂量体积直方图（DVH）的依赖性、强度级别数量以及序列器中的步长，进行了定量和定性研究。为验证治疗计划系统（TPS）计划的剂量与实际 delivered 剂量是否相同，使用CC01电离室确定某点的绝对剂量，并结合柯达EDR2、Scanditronix Wellhofer的OmniPro IMRT体模和OmniPro IMRT软件进行轴向平面剂量分布测量。为在叶片序列器模块中获得最佳组合，对强度级别数量、步长等参数进行了分析。比较并绘制了最佳注量分布的像素值与不同强度级别数量和步长组合所获得的注量分布之间的差异。使用3毫米和4毫米的网格大小比较剂量体积直方图中任何放疗结构的体积计算结果。除少数电离室放置在相对高剂量梯度区域的情况外，某点的测量剂量与计划剂量显示出良好的一致性（<3%）。在所有情况下，使用胶片剂量测定法的轴向平面剂量分布显示出极佳的一致性（相关系数>0.97）。在叶片序列器模块中，强度级别数量为7且步长为3的组合是获得可交付段的最佳解决方案。发现对于临床使用，3毫米的网格大小在放疗结构体积计算方面更准确。因此，本文介绍了关于康拉德IMRT逆向计划系统调试各方面的研究，该系统已在我们的诊所实施。 （注：原文中“delivered dose”直译为“交付剂量”，结合语境推测可能是“实际输出剂量”之类的意思，这里保留英文以便准确传达原文信息）
