鼻咽癌靶区及关键组织确定CT与MRI比较可行性研究

目的比较CT与MRI对鼻咽癌靶区及关键组织的确定．优化MRI序列以改善对鼻咽癌靶区及关键组织确定。方法8例未经治疗的鼻咽癌患者采用相同的放射治疗体位，面罩阎定，经CT、MRI扫描后，全部CT／MRI图像经网络传输至Ac—QSIM4．9．2配准，按照解剖边界、信号、密度等采用六点评分方法对CT与各序列MRI图像上的各个病变结构（咽旁间隙、颅底、颅内、椎前组织、脊髓、眼球、脑干）显示按级评分。结果各个解剖结构评分如下，咽旁间隙：CT2．750±0．370，T2WI4．250±0．250，T2W14．500±0．380，化学饱和脂肪抑制（FSPGR）增强T1WI5．625±0．180；椎前组织：CT2．000，T1WI4.125±0．230，T2WI5．000±0．190，化学饱和脂肪抑制（FSPGR）增强T1WI5．375±0．375；颅底：CT2．375±0．625，T1WI3．125±0．515，T2WI2．750±0．590，化学饱和脂肪抑制（FSPGR）增强T1WI4．250±0．725；颅内：CT1．000，T1WI1．375±0．375，T2WI1．875±0．580，化学饱和脂肪抑制（FSPGR）增强T1WI2．125±0．740；脊髓：CT4．125±0．230，T1WI6．000，T2W16．000，化学饱和脂肪抑制（FSPGR）增强TIW16．000；脑干：CT3．500±0.190，T1WI6．000、T2WI6．000，化学饱和脂肪抑制（FSPGR）增强T1WI6．000；眼球：CT5．375±0．180，T1WI6．000，T2WI6．000，化学饱和脂肪抑制（FSPGR）增强T1WI6．000。各结构的MRI图像都比CT有更高评分的趋势。结论与CT相比MRI在鼻咽癌靶区、重要器官的确定上有更大的优势，在MRI各序列中化学饱和脂肪抑制（FSPGR）增强T1WI较其他两种序列有更好的判断能力的趋势。在MRI模拟常规用于鼻咽癌放射治疗前，需要进一步研究来证实该研究结果及探讨其几何畸变、扫描时间等问题。

Comparison study on target volume and risk organ between CT and MRI in nasopharyngeal carcinoma

Objective To evaluate the feasibility of MRI in defining appropriate target volumes and normal organs, and compare MRI sequences with CT in nasopharyngeal carcinoma. Methods The CT and MRI scanning of 8 untreated patients with nasopharyngeal carcinoma were performed in treating position with immobilized mask. All imagings were transferred and registrated at AcQSIM4.9.2 workstation. Imagings in 8 patients with nasopharyngeal carcinoma of 3 MRI sequences （T1WI ,T2WI, contrast T1WI） were compared with their corresponding CT scannings. Segmentation ability of the following structures eg. parapharyngeal space, base of skull, intracranial part, prevertebral tissue, spinal cord, eyeball and brain stem were evaluated by 2 physicians. Six point grading scale based on anatomical definition of the organ boundary and tissue contrast were used to assess. Results The average scores of all structures assessed by each imaging sequences were as follows ：parapharyngeal space CT CT2.750±0.370,T2WI4.250±0.250,T2W14.500±0.380,contrast T1WI 5.625 ± 0.180; base of skull CT 2.375 ± 0.625 ,T1WI 3.125 ±0.515 ,T2WI 2.750 ±0.590,contrast T1 4.250 ± 0.725 ;intracranial part CT 1.000,T1WI 1.375 ± 0.375 ,T2WI 1.875± 0.580,contrast T1WI 2.125 ± 0.740;prevertebral tissue CT 2.000,T1WI 4.125 ± 0.230,T2 WI 5.000 ±0.190,contrast T1WI 5.375 ± 0.375;spinal cord CT 4.125 ± 0.230,% WI 6.000,T2WI 6.000,contrast T1WI 6.000;eyeball CT 5.375 ± 0.180,T1 WI 6.000,T2 WI 6.000,contrast T1WI 6.000;brain stem CT 3.500 ± 0.190,T1WI 6.000,T2WI 6.000,contrast T1WI 6.000. Compared with CT,the average MRI score of each assessed structure was improved ,with a trend for all contrast T1 WI sequences to provide improved segmentation of all structures. Conclusion Compared with CT,it is demonstrated that MRI can provide improved definition of nasoparyngeal carcinoma target volumes and normal tissue,but further study should be done to confirm its benefit and explore the issues of MRI associated distortion and scan time, before MRI performing routinely