van Asselen B, Raaijmakers C P, Hofman P, Lagendijk J J
Department of Radiotherapy, Q.00.118, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
Radiother Oncol. 2001 Mar;58(3):341-7. doi: 10.1016/s0167-8140(00)00278-4.
In spite of the complex geometry of the breast, treatment planning for tangential breast irradiation is conventionally performed using two-dimensional patient anatomy information. The purpose of this work was to develop a new technique which takes the three-dimensional (3D) patient geometry into account.
An intensity-modulated radiotherapy (IMRT) technique was developed based on the division of the tangential fields in four multi-leaf collimator (MLC) shaped segments. The shape of these segments was obtained from an equivalent path length map of the irradiated volume. Approximately 88% of the dose was delivered by two open fields covering the whole treated volume. Dose calculations for the IMRT technique and the conventional technique were performed for five patients, using computer tomography (CT) data and a 3D calculation algorithm. A planning target volume (PTV) and ipsilateral lung volume were delineated in these CT data.
All patients showed similar equivalent path length patterns. Analysis of the dose distribution showed an improved dose distribution using the IMRT technique. The dose inhomogeneity in the PTV was 9.0% (range 6.4-11.4%) for the conventional and 7.6% (range 6.5-10.3%) for the IMRT technique. The mean lung dose was reduced for the IMRT technique by approximately 10% compared with the conventional technique.
A new breast irradiation technique has been developed which improves the dose homogeneity within the planning target volume and reduces the dose to the lung. Furthermore, the IMRT technique creates the possibility to improve the field matching in case of multiple field irradiations of the breast and lymph nodes.
尽管乳房的几何形状复杂，但传统上乳腺切线照射的治疗计划是使用二维患者解剖信息进行的。这项工作的目的是开发一种考虑三维（3D）患者几何形状的新技术。
基于将切线野划分为四个多叶准直器（MLC）成形段，开发了一种调强放射治疗（IMRT）技术。这些段的形状是从照射体积的等效路径长度图获得的。大约88%的剂量由覆盖整个治疗体积的两个开放野提供。使用计算机断层扫描（CT）数据和三维计算算法，对五名患者进行了IMRT技术和传统技术的剂量计算。在这些CT数据中勾画了计划靶体积（PTV）和同侧肺体积。
所有患者均表现出相似的等效路径长度模式。剂量分布分析表明，使用IMRT技术剂量分布得到改善。传统技术在PTV中的剂量不均匀性为9.0%（范围6.4 - 11.4%），IMRT技术为7.6%（范围6.5 - 10.3%）。与传统技术相比，IMRT技术的平均肺剂量降低了约10%。
已开发出一种新的乳腺照射技术，可改善计划靶体积内的剂量均匀性并减少肺部剂量。此外，IMRT技术为在乳腺和淋巴结多野照射时改善野匹配创造了可能性。
