Department Radiation Oncology, Vydehi Institute of Medical Sciences, Bangalore, Karnataka, India.
Department of Radiology, Vydehi Institute of Medical Sciences, Bangalore, Karnataka, India.
Brachytherapy. 2021 Jan-Feb;20(1):112-117. doi: 10.1016/j.brachy.2020.07.014. Epub 2020 Sep 11.
Image-guided adaptive brachytherapy (IGABT) recently has shown excellent clinical outcomes with superior local control and less toxicity. For IGABT, T2W (T2-weighted) MRI is the gold standard. However, studies have shown that target delineation with the same results in uncertainties, poor interobserver variabilities, and low conformity indices for high-risk clinical target volume contours. In this study, we investigate the role of diffusion-weighted imaging-derived apparent diffusion coefficient (ADC) maps to aid in IGABT. We also evaluated ADC from the baseline to brachytherapy.
Thirty selected patients were enrolled for this study, and two MRIs were taken at diagnosis and before brachytherapy. Patients were divided into two groups, Group 1 being patients with parametrial involvement before external beam radiotherapy and no parametrial involvement before brachytherapy. Group 2 included patients with parametrial involvement before external beam radiotherapy and persistent parametrial involvement before brachytherapy. ADC was measured at the center, edge, and 1 cm from the edge.
The measured ADC increased from diagnosis to brachytherapy, and this increase was more for the patients in Group 1 than in Group 2. The mean TDadc (diagnosis ADC, center), TEadc (tumor edge ADC diagnosis), and T1cmDadc (1 cm from edge at diagnosis) were 0.884, 1.45, and 1.9 × 10 mm/s, respectively. The TBadc (ADC at brachytherapy, center), TEBadc (tumor edge ADC at brachytherapy), and TE1cmBadc (1 cm from edge brachytherapy) were 1.2, 1.8, and 2.3 × 10 mm/s, respectively, p-value <0.00001. No abnormal ADC was present outside the high-risk clinical target volume contours.
MRI-based IGABT using T2W imaging essentially covers all functionally abnormal zones at brachytherapy. Diffusion-weighted imaging, along with ADC maps, should only be used as a supplement for target delineation.
图像引导自适应近距离放射治疗（IGABT）最近显示出优异的临床结果，具有更好的局部控制和更少的毒性。对于 IGABT，T2W（T2 加权）MRI 是金标准。然而，研究表明，在不确定性、观察者间变异性差和高危临床靶体积轮廓的吻合指数低的情况下，用相同的结果进行靶区勾画。在这项研究中，我们探讨了扩散加权成像衍生的表观扩散系数（ADC）图谱在 IGABT 中的作用。我们还评估了从基线到近距离放射治疗期间的 ADC。
这项研究纳入了 30 名患者，在诊断时和近距离放射治疗前进行了两次 MRI。患者分为两组，组 1 为接受外部束放疗前有宫旁浸润且近距离放疗前无宫旁浸润的患者，组 2 为接受外部束放疗前有宫旁浸润且近距离放疗前宫旁浸润持续存在的患者。在中心、边缘和边缘 1cm 处测量 ADC。
ADC 从诊断到近距离放射治疗期间增加，组 1 患者的增加大于组 2。诊断时 ADC 中心（TDadc）、肿瘤边缘 ADC 诊断（TEadc）和 1cm 边缘 ADC 诊断（T1cmDadc）的平均值分别为 0.884、1.45 和 1.9×10mm/s。近距离放射治疗时 ADC 中心（TBadc）、肿瘤边缘 ADC 近距离放射治疗（TEBadc）和边缘 1cm 处 ADC 近距离放射治疗（TE1cmBadc）的平均值分别为 1.2、1.8 和 2.3×10mm/s，p 值<0.00001。高危临床靶体积轮廓外无异常 ADC。
基于 MRI 的 IGABT 使用 T2W 成像基本上涵盖了近距离放射治疗时所有功能异常区域。扩散加权成像及其 ADC 图谱应仅作为靶区勾画的补充。
