Purpose

The purpose of this study is to investigate the value of diffusion tensor imaging （DTI）in traumatic tibial nerve injury using 3.0T MR technology.

Introduction

Knee joint injuries are common and often accompanied by tibial nerve damage. Tibial nerve injury is susceptible to misdiagnosis in clinic due to the lack of effective diagnostic method. The regular electrophysiological examination fails to show its diagnostic value on patients with inobvious symptoms and signs. On the other hand, the traditional imaging examination can barely estimate the degree of injuries. The recently developed DTI is a functional magnetic resonance imaging tool, which can non-invasively and quantitatively estimate the degree of nerve damage by using the fractional anisotropy (FA) and average apparent diffusion coefficient (ADC) as indicators. Diffusion tensor tractography (DTT) can explicitly track the fiber arrangements and visually demonstrated the nuronal lesions such as modifications in demyelination levels. Therefore, DTI was introduced in the current study to evaluate its application on traumatic tibial nerve injury.

Materials and Method

The study included a retrospective review for 15 cases of patients diagnosed with tibial nerve injury and another 15 cases of healthy controls, which were divided into injured and control group. All the subjects underwent examinations using a 3.0T MR scanner (GE Signa HDXT) with routine scanning sequence and additional DTI sequence. The applied imaging parameters are as follows: FSE T2WI:TR = 4940 ms, TE = 86.1 ms, FOV = 18 x 18cm, NEX =2, slice-thickness = 3.0 mm, slice-gap = 0 mm;T1WI :TR = 780ms, TE = 12.5ms, FOV = 18 x 18cm, NEX =2, slice-thickness = 4.0 mm, slice-gap = 0.4 mm; DTI:TR = 9750ms, TE = 82.7ms, ETL15,b value=1000,FOV = 22 x 22cm, NEX =2, slice-thickness = 5.0 mm, slice-gap = 0mm,acquisition-matrix = 130 x 128. The MR images were blindly reviewed and analyzed by two independent observers who have 4 and 9 years’ experience of MR diagnosis, respectively. FA and ADC values were derived using the FuncTool on GE AW4.6 workstation. The SPSS17.0 statistical software was used for the data analyses, where P value less than 0.5 was considered as statistically significant. Inter-group difference was investigated for FA value, ADC value and the receiver operating characteristic(ROC)curve between FA and ADC values using t-test. Finally, DTT was applied to track tibial nerve fibers and to assess the trend and morphology of the nerve fibers.

Results

There was a significant difference in FA value between the injured (0.51±0.05)and control (0.58±0.05) groups ( t=-4.509, P<0.05, Table1). Moreover, a significant difference was observed in ADC value between the injured (1.43±0.07x10-3mm²/s )group and control (1.35±0.10x10-3mm²/s ) group (t=2.725, P<0.05, Table 2). The area under ROC curve of FA and ADC were 0.884 and 0.724, respectively. FA has a sensitivity of 0.733 and a specificity 0.934, while ADC has a sensitivity of 0.867 and a specificity 0.600 of ADC (Figure 1). DTI combined DTT can clearly demonstrate the normal or injured tibial nerve fibers (Figure 2,3).

Conclusion

DTI combined DTT is an effective method for the evaluation of the tibial nerve injury in traumatic patients.

Acknowledgements

No acknowledgement found.

References

[1]Chhabra A, Zhao L, Carrino J A, et al. MR Neurography: Advances.[J]. Radiology Research & Practice, 2013, 2013(7):809568-809568.