Klein Eric E, Mamalui-Hunter Maria, Low Daniel A
Washington University, St. Louis, MO, USA.
Phys Med Biol. 2009 Jan 21;54(2):327-39. doi: 10.1088/0031-9155/54/2/010. Epub 2008 Dec 19.
Electron beam radiotherapy is an accepted method to treat shallow tumors. However, modulation of electrons to customize dose distributions has not readily been achieved. Studies of bolus and tertiary collimation systems have been met with limitations. We pursue the use of photon multi-leaf collimators (MLC) for modulated electron radiotherapy (MERT) to achieve customized distributions for potential clinical use. As commercial planning systems do not support the use of MLC with electrons, planning was conducted using Monte Carlo calculations. Segmented and dynamic modulated delivery of multiple electron segments was configured, calculated and delivered for validation. Delivery of electrons with segmented or dynamic leaf motion was conducted. A phantom possessing an idealized stepped target was planned and optimized with subsequent validation by measurements. Finally, clinical treatment plans were conducted for post-mastectomy and cutaneous lymphoma of the scalp using forward optimization techniques. Comparison of calculations and measurements was successful with agreement of +/-2%/2 mm for the energies, segment sizes, depths tested for delivered segments for the dynamic and segmented delivery. Clinical treatment plans performed provided optimal dose coverage of the target while sparing distal organs at risk. Execution of plans using an anthropomorphic phantom to ensure safe and efficient delivery was conducted. Our study validates that MERT is not only possible using the photon MLC, but the efficient and safe delivery inherent with the dynamic delivery provides an ideal technique for shallow tumor treatment.
电子束放射治疗是治疗浅表肿瘤的一种公认方法。然而，对电子进行调制以定制剂量分布尚未轻易实现。对匀整块和三级准直系统的研究存在局限性。我们致力于将光子多叶准直器（MLC）用于调制电子放射治疗（MERT），以实现定制的剂量分布，供临床潜在使用。由于商业治疗计划系统不支持将MLC与电子束联合使用，因此使用蒙特卡罗计算进行治疗计划。配置、计算并交付了多个电子射野的分段和动态调制照射，以进行验证。进行了带有分段或动态叶片运动的电子束照射。设计并优化了一个具有理想化阶梯状靶区的模体，并通过测量进行后续验证。最后，使用正向优化技术对乳房切除术后和头皮皮肤淋巴瘤进行了临床治疗计划。对于动态和分段照射所测试的能量、射野大小和深度，计算结果与测量结果的比较成功，偏差在±2%/2毫米范围内。所执行的临床治疗计划在保护远端危险器官的同时，为靶区提供了最佳剂量覆盖。使用拟人化模体执行计划以确保安全、高效的照射。我们的研究证实，不仅可以使用光子MLC进行MERT，而且动态照射所固有的高效和安全照射为浅表肿瘤治疗提供了一种理想技术。
