鼻咽癌放疗中基于CT和MR图像勾画腮腺重复性的研究

Reproducibility of contouring parotid gland using CT and MR images in radiotherapy for nasopharyngeal carcinoma

目的 研究鼻咽癌放疗时基于计算机断层扫描（CT）和磁共振（MR）图像进行腮腺勾画的重复性和一致性.方法 选取2012年12月至2013年5月在山东省肿瘤医院接受治疗的鼻咽癌患者27例,放疗前均行强化CT和MR扫描.分别由11名放疗科医师在CT和MR图像上按照统一标准进行腮腺勾画.其中1名医师在27例患者的CT和MR图像上各勾画腮腺10次作组内比较,另外10名医师在27例患者的CT和MR图像上各勾画腮腺1次作组间比较.分析基于CT和MR图像勾画腮腺体积的组内、组间差异.结果 基于CT、MR图像勾画腮腺的组内平均体积分别为（33.8±9.4）cm3（左）、（33.2±7.6） cm3（右）;（24.4±7.6） cm3（左）、（22.5±7.4）cm3（右）;而对应腮腺体积差异率分别为（6.8±1.5）％、（6.3±1.5）％;（2.3±0.4）％、（2.1±0.7）％;基于CT、MR图像勾画腮腺的组间平均体积分别为（34.6±12.1） cm3（左）、（34.3±9.0）cm3（右）;（24.6±7.6）cm3（左）、（23.2±8.1） cm3（右）;对应腮腺体积差异率分别为（18.0±4.8）％、（17.4±4.6）％;（4.7±0.7）％、（5.0±0.6）％.结论 基于MR图像进行腮腺勾画能够得到比CT图像更稳定的重复性和一致性,有利于获得更加客观真实的评价腮腺放射性损伤的剂量-体积计算指标.

Objective To investigate the reproducibility and consistency in contouring parotid gland volume based on computed tomography （CT） and magnetic resonance （MR） images in patients with nasopha- ryngeal carcinoma during radiotherapy. Methods Twenty-seven patients with nasopharyngeal cancer in Shan- dong Cancer Hospital from December 2012 to May 2013 were randomly enrolled and underwent intensified CT and MR imaging before radiotherapy. The parotid gland were contoured with unified standard on both CT and T1-MR images by 11 radiotherapists. Specifically, one radiotherapist sketched the parotid gland on CT and MR images for ten times as intra-group comparison, the other ten were asked to sketch the parotid gland on CT and MR images only once as inter-group comparison. The intra- and inter-group＇s variations of parotid gland volumes were analysed. Results The average volumes of intra-group on CT and MR images were （33.8 ± 9.4） cm3（L）, （33.2±7.6） em3（R） and （24.4±7.6） cm3（L）, （22.5 ±7.4） cm3（R）. As well, for inter-group the average volumes were （34.6 ± 12.1 ） em3 （L） , （34.3 ±9.0） cmz （R） and （24.6 ±7.6） cm3 （L）, （23.2 ±8.1 ） era3（R）, respectively. The volume variable ratios on CT images were （6.8 ± 1.5）% （L）, （6.3 ±1.5）% （R） for intra-group and （18.0±4.8）% （L）, （17.4 ± 4.6）% （R） for inter-group. Similarly, the intra- and inter-group ratios for contouring on MR images reached （2.3 ± 0.4）% （L） , （2.1± 0.7）% （R）and （4.7±0.7）% （L）, （5.0±0.6）% （R）, respectively. Conclusion Parotid gland con- touring based on MR images has a better reproducibility and consistency than that based on CT images. It is beneficial to get a more objective and true indicator to estimate the radiation injury of parotid gland.