关键词: 扩散张量成像；磁共振成像；肌骨系统肿瘤；下肢；纤维束示踪成像

Abstract:

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.

Key words: Diffusion tensor imaging； Magnetic resonance imaging； Musculoskeletal tumor； Lower limbs;  Tractography