李泳衡, 巩贯忠, 苏亚, 王俪臻, 侯传珂, 卢洁, 尹勇. 颅骨及脑组织CT MR显示差异对脑肿瘤放疗剂量学影响的研究[J]. 中国肿瘤临床, 2021, 48(4): 180-185. DOI: 10.3969/j.issn.1000-8179.2021.04.373
引用本文: 李泳衡, 巩贯忠, 苏亚, 王俪臻, 侯传珂, 卢洁, 尹勇. 颅骨及脑组织CT MR显示差异对脑肿瘤放疗剂量学影响的研究[J]. 中国肿瘤临床, 2021, 48(4): 180-185. DOI: 10.3969/j.issn.1000-8179.2021.04.373
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Yongheng Li, Guanzhong Gong, Ya Su, Lizhen Wang, Chuanke Hou, Jie Lu, Yong Yin. Effects of display differences on computed tomography/magnetic resonance imaging between the skull and brain tissues on dosimetric variations in brain tumor radiotherapy[J]. CHINESE JOURNAL OF CLINICAL ONCOLOGY, 2021, 48(4): 180-185. DOI: 10.3969/j.issn.1000-8179.2021.04.373
Citation: Yongheng Li, Guanzhong Gong, Ya Su, Lizhen Wang, Chuanke Hou, Jie Lu, Yong Yin. Effects of display differences on computed tomography/magnetic resonance imaging between the skull and brain tissues on dosimetric variations in brain tumor radiotherapy[J]. CHINESE JOURNAL OF CLINICAL ONCOLOGY, 2021, 48(4): 180-185. DOI: 10.3969/j.issn.1000-8179.2021.04.373
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颅骨及脑组织CT MR显示差异对脑肿瘤放疗剂量学影响的研究

Effects of display differences on computed tomography/magnetic resonance imaging between the skull and brain tissues on dosimetric variations in brain tumor radiotherapy

    摘要
  • 摘要:
      目的  研究颅骨及脑组织CT/MR显示差异对脑瘤放疗剂量学的影响。
      方法  选取60例接受放疗的脑转移瘤（brain metastases，BM）患者，每例患者均行CT和MR模拟定位，将CT图像和MR图像刚性配准，在CT/MR融合图像上勾画肿瘤靶区、危及器官、颅骨（分别命名为Skull-CT、Skull-MR）、脑组织（分别命名为Brain-CT、不包含脑膜的Brain-MR-1、包含脑膜的Brain-MR-2）等组织和器官。基于CT图像制定三维适形放射治疗（3D-CRT）或调强放射治疗（IMRT）计划为Plan1；复制CT图像，基于CT/MR图像确定的颅骨（Skull）显示的差异区域Skull-sub赋予CT值20 HU，得到CT2图像，再将Plan1复制到CT2图像上进行放疗剂量的再次计算，获得Plan2。评估两组计划的靶区及组织器官的剂量学变化。
      结果  Skull-MR较Skull-CT体积平均减少约46%，Brain-CT的体积较不包含脑膜的Brain-MR-1与包含脑膜的Brain-MR-2平均减少约0.8%和6.7%，差异均具有统计学意义（均P < 0.05）。相比Plan1，Plan2的颅骨剂量变化率平均 < 3.5%；计划靶区（planning target volcome，PTV）剂量指标的变化率除了靶区剂量均匀性（HI）平均减少约6.8%，其他指标平均变化均 < 1.1%；危及器官的剂量平均变化率均 < 2%。此外，全脑放疗患者的PTVBrain-MR-1及PTVBrain-MR-2剂量指标较PTVBrain-CT，除了HI平均变化约11%和2.4%，其他指标的平均变化率均 < 2.2%。
      结论  颅骨及脑组织在CT/MR上的显示差异显著，虽然未对正常器官与肿瘤靶区的放疗剂量带来显著性变化，但对HI的影响仍不可忽视。

     

    Abstract:
      Objective  To study the effects of display differences on computed tomography (CT)/magnetic resonance (MR) imaging between the skull and brain tissues on dosimetric variations in brain tumor radiotherapy.
      Methods  Sixty patients with brain metastases who underwent radiotherapy were selected; they underwent CT and MR imaging simulations. The CT and MR images were rigidly registered, and the tumor target volume, organs at risk (OARs), skull (Skull-CT and Skull-MR), and brain (Brain-CT, Brain-MR-1 without meninges, and Brain-MR-2 with meninges) were contoured on the CT/MR fusion images. Three-dimensional conformal and intensity-modulated radiotherapy plans were designed based on CT images and named Plan-1. The CT2 image was obtained by copying the CT image and assigning a CT value of 20 Hounsfield units to the Skull-sub area determined on the CT/MR image. Plan-2 was designed by copying Plan-1 on the CT2 image and recalculating the radiation dose. Dosimetric variations in tumor target volume and OARs between the two plans were compared.
      Results  The Skull-MR volume was reduced by 46% compared with the Skull-CT volume, and the Brain-CT volume was reduced by 0.8% and 6.7% compared with the Brain-MR-1 and Brain-MR-2 volumes, respectively. All differences were statistically significant (P < 0.05). Compared with Plan-1, Plan-2 showed a skull dose variation rate of < 3.5%, a variation rate of most planning target volume (PTV) dose indexes of < 1.1%, a decrease in the variation rate of the homogeneity index (HI) by 6.8%, and an OAR dose variation rate of < 2%. Moreover, the variation rates of most dose indexes for PTVBrain-MR-1 and PTVBrain-MR-2 in patients receiving whole-brain radiotherapy were < 2.2% as compared with those of PTVBrain-CT, whereas the variation rates of the HI were 11% and 2.4%, respectively.
      Conclusions  The appearances of the skull and brain on CT/MR images were significantly different. We found no significant variations in the dose indexes of the tumor target volume and OARs; however, the effect of dose homogeneity of the tumor target volume should not be ignored.

     

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