Zoberi Jacqueline E, Garcia-Ramirez Jose, Hu Yanle, Sun Baozhou, Bertelsman Carol G, Dyk Pawel, Schwarz Julie K, Grigsby Perry W
Washington University School of Medicine.
J Appl Clin Med Phys. 2016 Jan 8;17(1):121-131. doi: 10.1120/jacmp.v17i1.5736.
The purpose of this study was to describe the clinical implementation of a magnetic resonance image (MRI)-based approach for adaptive intracavitary brachytherapy (ICBT) of cervix cancer patients. Patients were implanted with titanium tandem and colpostats. MR imaging was performed on a 1.5-T Philips scanner using T2-weighted (T2W), proton-density weighted (PDW), and diffusion-weighted (DW) imaging sequences. Apparent diffusion coefficient (ADC) maps were generated from the DW images. All images were fused. T2W images were used for the definition of organs at risk (OARs) and dose points. ADC maps in conjunction with T2W images were used for target delineation. PDW images were used for applicator definition. Forward treatment planning was performed using standard source distribution rules normalized to Point A. Point doses and dose-volume parameters for the tumor and OARs were exported to an automated dose-tracking application. Brachytherapy doses were adapted for tumor shrinkage and OAR variations during the course of therapy. The MRI-based ICBT approach described here has been clinically implemented and is carried out for each brachytherapy fraction. Total procedure time from patient preparation to delivery of treatment is typically 2 hrs. Implementation of our tech-nique for structure delineation, applicator definition, dose tracking, and adaptation is demonstrated using treated patient examples. Based on published recommendations and our clinical experience in the radiation treatment of cervix cancer patients, we have refined our standard approach to ICBT by 1) incorporating a multisequence MRI technique for improved visualization of the target, OARs, and applicator, and by 2) implementing dose adaptation by use of automated dose tracking tools.
本研究的目的是描述基于磁共振成像（MRI）的宫颈癌患者适应性腔内近距离放疗（ICBT）方法的临床应用。患者植入钛制施源器和阴道柱状容器。使用1.5-T飞利浦扫描仪，采用T2加权（T2W）、质子密度加权（PDW）和扩散加权（DW）成像序列进行磁共振成像。从DW图像生成表观扩散系数（ADC）图。所有图像进行融合。T2W图像用于定义危及器官（OARs）和剂量点。ADC图结合T2W图像用于靶区勾画。PDW图像用于施源器定义。采用归一化到A点的标准源分布规则进行正向治疗计划。将肿瘤和OARs的点剂量和剂量体积参数导出到自动剂量跟踪应用程序。在治疗过程中，根据肿瘤缩小和OARs变化调整近距离放疗剂量。本文所述的基于MRI的ICBT方法已在临床应用，且每次近距离放疗分次均采用该方法。从患者准备到治疗实施的总过程时间通常为2小时。通过已治疗患者的实例展示了我们在结构勾画、施源器定义、剂量跟踪和调整方面技术的应用。基于已发表的建议和我们在宫颈癌患者放射治疗方面的临床经验，我们通过以下方式改进了ICBT的标准方法：1）采用多序列MRI技术，以更好地显示靶区、OARs和施源器；2）使用自动剂量跟踪工具实施剂量调整。
