West Michigan Cancer Center, 200 North Park Street, Kalamazoo, Michigan 49007, USA.
Med Phys. 2010 Jun;37(6):2837-46. doi: 10.1118/1.3431994.
To measure patient-specific-QA dose distributions with a 2D array of diodes, the MapCHECK, for the dose delivered, with step-and-shoot and rotational IMRT.
Two MapCHECKs were used that had different styles of diode connection. These MapCHECKs were used in their original manufactured configuration and in a modified configuration. The modification made in the clinic consists of filling air gaps with sheets of Lucite that had custom-machined slots for the diodes and by adding pieces of copper to offset the intrinsic asymmetry of the diodes. The MapCHECKs were housed in a tight-fitting phantom fabricated from solid water. Measurements were made on IMRT treatment plans delivered with Varian linear accelerators with step-and-shoot and RapidArc methods, and a TomoTherapy machine with helical delivery. Patient plans and QA plans were developed with the XiO, Eclipse, and TomoTherapy planning systems. All MapCHECK data were analyzed with its commercially available software.
Kilovoltage CT imaging of the MapCHECK in its phantom has streak artifacts from high atomic number components. These artifacts must be corrected in order to obtain accurate calculation of dose. The original MapCHECK is found to have an angular dependence of +/- 20%. A modification of the MapCHECK has been made that reduces the angular dependence to +/- 2%. Proper compensation for attenuation by the treatment couch is also necessary for accurate results. The modified MapCHECK has been successfully used for doing patient-specific QA for IMRT treatments delivered with step-and-shoot, TomoTherapy, and RapidArc methods. Treatment plans that require large amounts of fluence from the 90 degrees and 270 degrees directions have significantly better QA measurements when made with modified MapCHECKs.
When properly modified, the MapCHECK response becomes isotropic. It can then be used for patient-specific QA measurements for IMRT treatments delivered with step-and-shoot and rotational techniques such as helical Tomotherapy and RapidArc.
使用二维二极管阵列 MapCHECK 测量剂量分布，用于步进和旋转调强放射治疗（IMRT）的剂量传递。
使用了两种具有不同二极管连接方式的 MapCHECK。这些 MapCHECK 按照原始制造配置和修改后的配置进行使用。在临床实践中进行的修改包括用有机玻璃片填充空气间隙，这些有机玻璃片上有定制加工的用于二极管的插槽，并添加一些铜片以抵消二极管的固有不对称性。MapCHECK 被安装在由固体水制成的紧密贴合的体模中。使用瓦里安直线加速器的步进和 RapidArc 方法以及 TomoTherapy 螺旋式机器进行 IMRT 治疗计划的测量。患者计划和 QA 计划是使用 XiO、Eclipse 和 TomoTherapy 规划系统开发的。所有 MapCHECK 数据都使用其商业可用软件进行分析。
MapCHECK 在体模中的千伏级 CT 成像存在高原子序数成分的条纹伪影。为了获得准确的剂量计算，必须对这些伪影进行校正。原始的 MapCHECK 被发现具有 +/-20%的角度依赖性。已经对 MapCHECK 进行了修改，将角度依赖性降低到 +/-2%。为了获得准确的结果，还需要对治疗床的衰减进行适当补偿。经过修改的 MapCHECK 已成功用于对使用步进和 TomoTherapy、RapidArc 方法进行的 IMRT 治疗进行患者特异性 QA。对于需要从 90 度和 270 度方向大量强度的治疗计划，使用修改后的 MapCHECK 进行 QA 测量会有显著改善。
经过适当修改后，MapCHECK 的响应变得各向同性。然后，它可以用于对使用步进和旋转技术（如螺旋 Tomotherapy 和 RapidArc）进行的 IMRT 治疗的患者特异性 QA 测量。
