PET-CT用于肿瘤精确放疗靶区勾画的困惑

PET-CT用于精确放疗靶区勾画时,存在诸多困惑。谁来勾画靶区?差异可能来自哪些方面?究竟取多大标准化摄取值区分肿瘤和正常组织最适宜?当局部PET和CT显示肿瘤范围不一致时,靶区应当怎样确定?当区域淋巴结或远隔部位PET阳性而CT阴性或相反时,靶区的选择当作何种取舍?在目前阶段,这些问题尚未达成统一的共识,有待更进一步的关于影像和与之相匹配的病理标本相关性研究,而且需要更多远期临床增益结果来反证靶区勾画原则的可行性。

The dilemma of the target delineation with PET-CT in the radiotherapy planning for malignant tumors

Questions are currently still not clearly conclusively answered, when contouring target with PET/CT in the radiotherapy planning. Who needs to contour the PET volume, the radiation oncologist or the nuclear medicine physician? Which factors will contribute to the increase of the inter-observer variability between them? What should be taken as the optimal SUV threshold to demarcate malignant tumors from the benign tissue? When the PET volume is not in accordance with the CT finding in the local area, which part should be contoured as the target? When PET positive while CT negative or PET negative while CT positive were shown in the regional lymph node draining area or in the remote region, in which way the target could be decided and selected? Further study concerning the corresponding relationship between PET-CT and its registered pathological specimen are needed. The long-term clinical results of increased therapeutic ratio will finally verify the applicability of the guideline to contour the target with PET-CT in the radiotherapy planning.