MR/CT和18FDG PET/CT对鼻咽癌肿瘤区勾画比较研究

目的比较MRI/CT或PET/CT对鼻咽癌调强放射治疗患者肿瘤区(GTV)勾画的差异。方法2007年2~11月间,26例实施根治性调强放射治疗的鼻咽癌患者在放射治疗开始前1w内行PET/CT,MRI以及增强定位CT扫描,一组医师根据PET/CT勾画GTV,而另一组医师则根据MRI/CT勾画GTV,两组医师再共同评价肿瘤区间勾画部位差异。为便于研究,对于原发灶部位,GTV1C定义为MRI/CT基础上的GTV,GTV1P为PET/CT基础上的GTV,对于颈部区域淋巴结则分别定义为GTV2C及GTV2P,在此基础上,GTV1C和GTV1P的合并肿瘤区被定义为GTV1T,重叠肿瘤区则被定义为GTV1M,GTV2C和GTV2P的合并肿瘤区定义为GTV2T,重叠肿瘤区定义为GTV2M。结果GTV1P和GTV2P均明显小于GTV1C及GTV2C,GTV1T相较GTV1C无明显增大,但GTV2T则明显大于GTV2C,原发灶部位肿瘤区间勾画差异主要位于颅底,颈部淋巴结差异主要源于小淋巴结及淋巴结包膜外侵犯累及肌肉。结论PET/CT有助于鼻咽癌肿瘤区勾画,PET/CT基础上的肿瘤区明显小于MRI/CT基础上的肿瘤区,但PET/CT基础上的肿瘤区并不总是包含于MRI/CT基础上的肿瘤区,两者间的差异在颈部更为明显。

Delineation of gross tumor volume in nasopharyngeal carcinoma:comparison between MR imaging/CT and 18FDG PET/CT

Objective To compare magnetic resonance imaging/ computed tomography (MRI/CT)-based gross tumor volume (GTV) to 18F-fluoro-2-deoxy-D-glucose positron emission tomography/ computed tomography (PET/CT)-based GTV for radical radiotherapy of nasopharyngeal carcinoma. Methods The subjects consisted of 26 patients with nasopharyngeal carcinoma who were treated with radical Intensity Modulated Radiotherapy (IMRT) between Feb 2007 and Nov 2007. PET/CT and MRI/CT were performed for each patient within one week before radiotherapy. The GTVs were separately delineated by two groups of experienced physicians, including a radiation oncologist and radiologist/ PET physician, respectively. For primary tumor, PET/CT-based GTV and MRI/CT-based GTV was defined as GTV1P and GTV1C, respectively. Similarly, GTV2P and GTV2C for regional lymph node. The GTVs mentioned above were contoured by physicians. GTV1P combined with GTV1C were defined as GTV1T and GTV overlapped both in GTV1P and GTV1C was defined as GTV1M for primary tumor, GTV2T and GTV2M for regional lymph node. The GTVs were generated from eclipse treatment-planning work stations. To assess the potential geographic difference between the PET/CT-based GTV and the MRI/CT-based GTV, The geographic difference were analyzed by both of the two groups of physicians.Results GTV1P (14.2cm3) and GTV2P (12.9cm3) were smaller compared of GTV1C(34.4cm3) and GTV2C(22.0cm3), respectively (P=0.000,0.000, respectively). No statistic significant difference was observed between the volume of GTV1T(35.6cm3) and GTV1C (P = 0.065). However, GTV2C was significantly smaller compared of GTV2T (23.5 cm3 )(P = 0.065). The geographic difference between the PET/CT-based GTV and the MRI/CT-based GTV mainly located in the base of skull for primary tumor and the isolated or scatted small lymph node for the regional lymph node, respectively.Conclusions PET/CT-based GTV was significantly smaller compared of MRI/CT-based GTV. However, PET/CT-based GTV was not always included in MRI/CT-based GTV. The addition of PET/CT imaging was useful in GTV determination especially for regional lymph node.