van Heerden Laura E, Houweling Antonetta C, Koedooder Kees, van Kesteren Zdenko, van Wieringen Niek, Rasch Coenraad R N, Pieters Bradley R, Bel Arjan
Department of Radiation Oncology, Academic Medical Center/University of Amsterdam, The Netherlands.
Department of Radiation Oncology, Academic Medical Center/University of Amsterdam, The Netherlands.
Radiother Oncol. 2017 May;123(2):319-324. doi: 10.1016/j.radonc.2017.03.015. Epub 2017 Mar 31.
Structure-based deformable image registration (DIR) can be used to calculate accumulated brachytherapy (BT) and external-beam radiation therapy (EBRT) dose-volume histogram (DVH) parameters in cervical cancer. Since direct parameter addition does not take dose non-uniformity into account, the added value of DIR over addition methods was investigated for bladder and rectum.
For twelve patients (EBRT: 46Gy, EBRT+BT: D 85-90Gy in equivalent dose in 2Gy fractions) the EBRT planning CT and BT planning MRI were registered using DIR. Affected lymph nodes, located far from the BT boost region, received an EBRT boost (9.2Gy) not contributing to the BT boost dose. Cumulative bladder/rectum D/D were calculated and compared to direct addition methods, assuming uniform EBRT doses (UD), or overlapping high dose volumes (OHD).
Between the three methods, the maximum differences in the cumulative DVH parameters were 3.2Gy (bladder) and 3.3Gy (rectum). The difference between DIR and UD was <1.8Gy for both organs.
The UD method provides a better estimate of D/D than the OHD method. There is no added value of DIR since differences with direct addition methods are clinically insignificant. EBRT dose distributions can be considered uniform in bladder and rectum for the evaluated dose parameters.
基于结构的可变形图像配准（DIR）可用于计算宫颈癌近距离放疗（BT）和外照射放疗（EBRT）累积剂量体积直方图（DVH）参数。由于直接相加参数未考虑剂量不均匀性，因此研究了DIR相对于相加方法在膀胱和直肠方面的附加价值。
对于12例患者（EBRT：46Gy，EBRT + BT：等效剂量85 - 90Gy，分2Gy分次），使用DIR对EBRT计划CT和BT计划MRI进行配准。远离BT推量区域的受累淋巴结接受EBRT推量（9.2Gy），该剂量对BT推量剂量无贡献。计算累积膀胱/直肠D/D，并与直接相加方法进行比较，假设EBRT剂量均匀（UD）或高剂量体积重叠（OHD）。
在三种方法之间，累积DVH参数的最大差异为膀胱3.2Gy和直肠3.3Gy。DIR与UD之间的差异在两个器官中均<1.8Gy。
UD方法比OHD方法能更好地估计D/D。DIR没有附加价值，因为与直接相加方法的差异在临床上无显著意义。对于所评估的剂量参数，EBRT剂量分布在膀胱和直肠中可视为均匀。
