Department of Radiotherapy, University Medical Centre Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.
Phys Med Biol. 2013 Sep 7;58(17):5917-30. doi: 10.1088/0031-9155/58/17/5917. Epub 2013 Aug 6.
The UMC Utrecht MRI/linac (MRL) design provides image guidance with high soft-tissue contrast, directly during radiotherapy (RT). Breast cancer patients are a potential group to benefit from better guidance in the MRL. However, due to the electron return effect, the skin dose can be increased in presence of a magnetic field. Since large skin areas are generally involved in breast RT, the purpose of this study is to investigate the effects on the skin dose, for whole-breast irradiation (WBI) and accelerated partial-breast irradiation (APBI). In ten patients with early-stage breast cancer, targets and organs at risk (OARs) were delineated on postoperative CT scans co-registered with MRI. The OARs included the skin, comprising the first 5 mm of ipsilateral-breast tissue, plus extensions. Three intensity-modulated RT techniques were considered (2× WBI, 1× APBI). Individual beam geometries were used for all patients. Specially developed MRL treatment-planning software was used. Acceptable plans were generated for 0 T, 0.35 T and 1.5 T, using a class solution. The skin dose was augmented in WBI in the presence of a magnetic field, which is a potential drawback, whereas in APBI the induced effects were negligible. This opens possibilities for developing MR-guided partial-breast treatments in the MRL.
乌得勒支大学医学中心磁共振引导直线加速器（MRL）的设计在放射治疗（RT）过程中提供了高软组织对比度的图像引导。乳腺癌患者是从 MRL 中获得更好指导的潜在受益群体。然而，由于电子回流效应，在磁场存在的情况下皮肤剂量会增加。由于乳房 RT 通常涉及大面积的皮肤，因此本研究的目的是研究全乳照射（WBI）和加速部分乳房照射（APBI）时皮肤剂量的影响。在 10 名患有早期乳腺癌的患者中，在术后 CT 扫描上对靶区和危及器官（OAR）进行了勾画，并与 MRI 进行了配准。OAR 包括皮肤，包括同侧乳房组织的前 5 毫米，加上延伸部分。考虑了三种强度调制 RT 技术（2×WBI、1×APBI）。为所有患者使用了个体化的射束几何形状。专门开发的 MRL 治疗计划软件用于生成计划。使用分类解决方案，在 0 T、0.35 T 和 1.5 T 时，均可以生成可接受的计划。在磁场存在的情况下，WBI 中的皮肤剂量增加，这是一个潜在的缺点，而在 APBI 中，诱导的影响可以忽略不计。这为在 MRL 中开发 MR 引导的部分乳房治疗提供了可能性。
