Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, and Hospital Universitario Virgen Macarena, Sevilla, Spain.
Phys Med Biol. 2010 Mar 7;55(5):1413-27. doi: 10.1088/0031-9155/55/5/010. Epub 2010 Feb 11.
The purpose of this paper is to assess the feasibility of delivering intensity- and energy-modulated electron radiation treatment (MERT) by a photon multileaf collimator (xMLC) and to evaluate the improvements obtained in shallow head and neck (HN) tumors. Four HN patient cases covering different clinical situations were planned by MERT, which used an in-house treatment planning system that utilized Monte Carlo dose calculation. The cases included one oronasal, two parotid and one middle ear tumors. The resulting dose-volume histograms were compared with those obtained from conventional photon and electron treatment techniques in our clinic, which included IMRT, electron beam and mixed beams, most of them using fixed-thickness bolus. Experimental verification was performed with plane-parallel ionization chambers for absolute dose verification, and a PTW ionization chamber array and radiochromic film for relative dosimetry. A MC-based treatment planning system for target with compromised volumes in depth and laterally has been validated. A quality assurance protocol for individual MERT plans was launched. Relative MC dose distributions showed a high agreement with film measurements and absolute ion chamber dose measurements performed at a reference point agreed with MC calculations within 2% in all cases. Clinically acceptable PTV coverage and organ-at-risk sparing were achieved by using the proposed MERT approach. MERT treatment plans, based on delivery of intensity-modulated electron beam using the xMLC, for superficial head and neck tumors, demonstrated comparable or improved PTV dose homogeneity with significantly lower dose to normal tissues. The clinical implementation of this technique will be able to offer a viable alternative for the treatment of shallow head and neck tumors.
本文旨在评估使用光子多叶准直器（xMLC）实现强度调制和能量调制电子放射治疗（MERT）的可行性，并评价在浅层头颈部（HN）肿瘤中所获得的改善。通过 MERT 对四个涵盖不同临床情况的 HN 患者病例进行了计划，该计划使用了一个内部的治疗计划系统，该系统利用蒙特卡罗剂量计算。这些病例包括一个口咽、两个腮腺和一个中耳肿瘤。将所得的剂量-体积直方图与我们临床中使用的常规光子和电子治疗技术（包括调强放射治疗、电子束和混合束，其中大多数使用固定厚度的填充物）获得的结果进行了比较。使用平板平行电离室进行绝对剂量验证，以及 PTW 电离室阵列和放射色胶片进行相对剂量测量，对实验进行了验证。针对深度和侧向靶区容积受限制的 MC 治疗计划系统已进行了验证。为个别 MERT 计划启动了质量保证协议。相对 MC 剂量分布与胶片测量高度一致，在参考点进行的绝对离子室剂量测量与 MC 计算的误差在所有情况下均小于 2%。使用所提出的 MERT 方法，可以实现对浅层头颈部肿瘤的临床可接受的 PTV 覆盖和对危险器官的保护。基于使用 xMLC 来实现强度调制电子束的 MERT 治疗计划，对于浅层头颈部肿瘤，与 PTV 剂量均匀性相比，可获得可比或改善的结果，同时显著降低了对正常组织的剂量。该技术的临床实施将能够为治疗浅层头颈部肿瘤提供一种可行的替代方法。
