3.0T磁共振扩散张量及纤维束示踪成像在下肢骨与软组织肿瘤诊断中的应用价值

目的探讨3.0T高场强磁共振扩散张量成像(DTI)及纤维束示踪成像(FTI)在下肢骨与软组织肿瘤诊断中的价值。方法收集经病理学证实的下肢骨与软组织肿瘤患者23例。治疗前应用西门子MEGNETOM Veriosyngo MR B17机,先行常规MR扫描,然后运用单次激发平面回波DTI扫描,选择20个非线性弥散方向,最后T1WI对比增强扫描。在工作站分析病变的大小、形态、信号特点及与病变周围组织的关系,运用NEURO 3D软件自动生成各向异性指数图,感兴趣区定义肿瘤实质区为T2WI及DWI上高信号,增强扫描明显强化区域,正常肌肉区为周围正常肌肉信号无异常强化区域,分别测量良、恶性肿瘤实质及正常肌肉的部分各向异性(FA值)、表观弥散系数(ADC值)、相对各向异性(RA值)、体积比(VR值)及本征值(λ1)。在融合模式下利用扩散张量纤维束示踪成像(DT-FT)三维重组病变及周围肌肉纤维束成像以观察病变对周边肌肉纤维束的影响。结果良、恶性肿瘤之间的各向异性参数值FA值、RA值及VR值比较,有显著的统计学差异(P<0.05),ADC值、λ1值无统计学差异(P>0.05)。去除良、恶肿瘤区别,纤维组织成分为主肿瘤实质区与其他组织源性肿瘤实质区各向异性FA值、RA值及VR值比较,有更显著的统计学差异(P<0.005)。三维纤维束成像显示,良性肿瘤对肿瘤周边肌纤维束的影响主要表现受压移位。恶性肿瘤对周边肌纤维束的影响主要表现为纤维束向肿瘤集结,纤维束稀疏,走行方向改变、紊乱、中断等。结论 DTI作为一种非侵入性研究骨与软组织肿瘤的功能MR成像技术,结合三维纤维束成像,能分析肿瘤内部结构特征及与周边组织的三维关系,对肌骨系统下肢肿瘤的诊断分析思路及鉴别诊断有重要临床意义。

Application of diffusion tensor and fiber tractography imaging of 3.0 magnetic resonance in the diagnosis of musculoskeletal tumors in lower limbs

Objective To investigate the diagnosis value of diffusion tensor imaging(DTI) and fiber tractography imaging(FTI) in patients with musculoskeletal tumors in lower limbs.Methods A retrospective evaluation was carried out in 23 patients with musculoskeletal tumors in lower limbs.All the patients underwent routine MRI(Siemens MEGNETOM Verio syngo MR B17,Germany) before treatment.Scans were made by multidirectional diffusion weighted imaging(measured in 20 non-collinear directions) and T1 contrast enhanced images.The tumor’s size,shape,signal characteristic and anatomic relation between lesion and its neighbor tissue were observed.Anisotropic parameter maps were automatically shown in NEURO 3D software.Tumor parenchyma was defined as the region of interest(ROI) with high T2,DWI signal intensity and contrast enhancement.Normal muscle fibers were assumed as the normal location of T2 signal intensity without enhancement.FA,ADC,RA,VR,and λ1 maps were calculated and ROI was manually placed over areas of tumor parenchyma and normal muscle fibers.Independent samples group t test was made for statistical analysis with SPSS 19.0 software package.A three-dimensional model of the muscle fibers was created by diffusion tensor fiber tractography(DT-FT) techniques to demonstrate the space relationship of the tumor and adjacent muscle fibers.Results There were significant differences between benign and malignant tumors in FA,RA,VR values(P<0.05) and no differences in ADC and λ1 values(P>0.05).The FA,RA and VR values had significant differences between fibrous tumors and other tumors(P<0.005).FT of muscle fiber tracts showed edema,compression and displacement around benign tumors.The influence of malignant tumors toward adjacent fiber mainly manifested as reduced anisotropy,abnormal orientation,infiltration and disruption.Conclusion As a noninvasive FMRI method for musculoskeletal tumors,DTI combined with FT can better demonstrate the tumor edges,internal conditions,and relation of tumors to the adjacent tissues,and provide assistance in diagnosis and differential diagnosis between benign and malignant tumors in the musculoskeletal system.