Application Of Diffusion Tensor Imaging In Assessment Of Anterior Cruciate Ligament And Its Injury

BackgroundAnterior cruciate ligament（ACL）injury was one of the common diseases of knee joint,which could lead to knee joint rotation imbalance,cartilage degeneration and other complications.It was difficult for imaging diagnosis because of the joint swelling and pain in the early stage after injury.Magnetic resonance imaging（MRI）was the main imaging technique for the diagnosis of ACL injuries,there were still many limitations in the diagnosis based on MRI signal intensity,which lead to low accuracy and specificity in the diagnosis of ACL partial tears,the early diagnosis,treatment and prognosis evaluation of ACL injury were seriously affected.ObjectiveDiffusion tensor imaging（DTI）technique were used to measure the fractional anisotropy（FA）values,apparent diffusion coefficient（ADC）values and their correlation in different sites and degrees of ACL and its injury.It was used to evaluate the degree of ACL injury and the surgical effect after its reconstruction,FA values and ADC values before and after ACL reconstruction and follow-up.To provide quantitative diagnostic data and quantitative analysis for ACL injury,to help clinicians made better treatment decisions and prognosis assessment.MethodsThe DTI images of 100 normal knee joints were collected,including 50 male and50 female,47 on the left and 53 on the right.In 100 inpatients with unilateral ACL injury,16 patients with I grade,23 patients with II grade,36 patients with III grade,25 patients with IV grade.Single-bundle autogenous tendon reconstruction was performed in III grade and IV grade inpatients,and 54 cases were followed up.DTI technique were used to scan the knee joint after getting up in the morning,input the image data into the image post processing workstation,and used the software system in the workstation to process the image and generate FA false color images and ADC images,and the FA values and ADC values were measured.The region of interest was set along the ACL and its injury,reconstruction site,fiber tracing imaging based on fiber connections in the region of interest.The regions of interest were set up by 2physicians respectively,and the average values were taken 3 times each.Using SPSS20.0 statistical software to deal with the data,and the difference was statistically significant in P<0.05.Results1.The FA values and ADC values of the upper ends,upper-middle,middle,lower-middle and lower ends of normal ACL were（0.620±0.041）,（0.608±0.050）,（0.595±0.043）,（0.566±0.057）,（0.497±0.051）and（1.067±0.136）×10^-3mm²/s,（1.128±0.134）×10^-3mm²/s,（1.189±0.151）×10^-3mm²/s,（1.456±0.171）×10^-3mm²/s,（1.779±0.204）×10^-3mm²/s respectively,it was statistically significant（P<0.05）.The FA values decreased with the position of ACL from top to bottom,and it was negatively correlated with the position,while ADC values increased and positively correlated with the position.2.The FA values and ADC values of ACL injury and corresponding position of normal ACL were（0.449±0.039）,（0.577±0.064）and（2.564±0.227）×10^-3mm²/s,（1.324±0.160）×10^-3mm²/s respectively,it was statistically significant（P<0.05）.The FA values of ACL injury was lower than that of normal group,the ADC values was higher than that of the normal group.3.The FA values and ADC values of I,II,III and IV grade ACL damaged area were（0.492±0.051）,（0.488±0.049）,（0.412±0.044）,（0.378±0.041）and（2.153±0.182）×10^-3mm²/s,（2.248±0.225）×10^-3mm²/s,（2.740±0.253）×10^-3mm²/s,（2.844±0.327）×10^-3mm²/s respectively,it was statistically significant（P<0.05）.The FA values decreased gradually with the increase of damage degree,which was negatively correlated with the damage degree,the ADC values increased gradually,which was positively correlated with the damage degree.The sensitivity,specificity,accuracy,positive predictive value and negative predictive value of tractography imaging,FA values and ADC values,MRI in the diagnosis of ACL injury were96.00%,85.00%,73.00%and 98.67%,95.00%,91.00%and 98.00%,92.50%,86.50%and 96.00%,85.00%,73.00%and 98.67%,95.00%,91.00%respectively,the differences were statistically significant（P<0.05）,they were tractography imaging,FA values and ADC values,MRI from high to low.4.There was no significant difference in FA values and ADC values between the stable group and unstable group in 1 week after ACL reconstruction（P>0.05）.The sensitivity,specificity,accuracy,positive predictive value and negative predictive value of tractography imaging,FA values and ADC values,MRI in the reconstruction of ACL injury were 98.25%,87.72%,73.68%and 100.00%,75.00%,50.00%and98.36%,86.89%,72.13%and 100.00%,98.04%,95.45%and 80.00%,30.00%,11.76%respectively,it was statistically significant（P<0.05）,they were tractography imaging,FA values and ADC values,MRI from high to low.5.The FA values and ADC values before ACL reconstruction and 1 week,3months after its reconstruction were（0.395±0.047）,（0.541±0.056）,（0.542±0.058）and（2.791±0.336）×10^-3mm²/s,（2.263±0.224）×10^-3mm²/s,（2.028±0.341）×10^-3mm²/s respectively,it was statistically significant（P<0.05）.It was no significant difference in FA between the 1 week and 3 months after reconstruction（P>0.05）,and the ADC values was statistically significant（P<0.05）.6.The FA values and ADC values in 3 months,6 months,1 year after ACL reconstruction and normal group were（0.542±0.058）,（0.595±0.056）,（0.684±0.059）,（0.577±0.064）and（2.028±0.341）×10^-3mm²/s,（1.699±0.175）×10^-3mm²/s,（1.375±0.151）×10^-3mm²/s,（1.324±0.160）×10^-3mm²/s respectively,it was statistically significant（P<0.05）.There was no significant difference in FA values follow-up of 6months after ACL reconstruction compared with the normal group and the ADC values in 1 year follow-up group compared with the normal group（P>0.05）.Conclusion1.The FA value and ADC value of DTI can quantitatively and objectively evaluate the degree of ACL injury and repair,and observe the changes of microstructure,which can provide quantitative diagnostic data and quantitative analysis for clinicians.2.The tractography imaging of DTI can better display the degree of ACL injury and the effect of operation in early stage,it can directly show the change of the space structure and help the clinician to make the best treatment decision and evaluate the prognosis.