Application Of MRI In Forensic Identification Of Vertebral Compression Fractures

Part IThe application of MRI in the assessment of single vertebral compression degreeObjective To explore the difference of compression degree of individual vertebral fracture by different methods in MRI.In order to provide a more accurate evaluation method for judicial identification.Methods MRI data of 293 cases with thoracolumbar spine fresh compression fractures were analyzed retrospectively.The compressed vertebral body in each sample and the two adjacent normal vertebral body above and below were used as the observation group.?1?The median vertebral body anterior height?H_an?,posterior height?H_pn?,upper vertebral body anterior height(H_an-1),and lower vertebral body anterior height(H_an+1)were measured,and the mean height(H'an=H_an-1+H_an+1/2)of upper and lower vertebral bodies were calculated.The degree of vertebral compression was calculated according to four different evaluation method(C₁=H_pn-H_an/H_pn;C₂=H_an-1-H_an/H_an-1;C₃=H_an+1-H_an/H_an+1;C4=H'an-H_an/H'an),Compression uegree above 1/3?including 1/3?is positive.The positive cases obtained by the four methods were compared to see whether there were statistical differences.?2?The three adjacent normal vertebral bodies above the compressed vertebral bodies in the sample were used as the control group.H_an?H_pn?H_an-1?H_an+1were measured,H'an=H_an-1+H_an+1/2 were calculated.Pairwise comparison was made between H_an and the other four groups of data,and consistency test was performed for the groups with no statistical difference?95%confidence interval?.Results?1?Observation group:among the above four evaluation methods,method 3 had the highest positive cases and method 1 had the lowest positive cases,and there was no statistical difference between the results of method 1 and method 4.?2?Control group:through paired t test,there was no statistical difference between H_an and H'an.The consistency test shows that the consistency is good.Conclusion In the case of a single vertebral compression fracture,the original height cannot be directly measured.H'an is the most accurate method to calculate the degree of compression instead of the height of the front edge of the diseased vertebra,which has an important guiding role in the judicial expertise process.Part IIApplication of SNR and CNR values in time inference of traumatic compressive fractureObjective To explore the application value of MRI contrast signal-to-noise ratio?CNR?and signal-to-noise ratio?SNR?in inferring the time of traumatic vertebral compression fracture through comparing the correlation between the injury time of vertebral compression fracture and the change of signal intensity in MRI.Methods 113 MRI images of thoracolumbar vertebral compression fractures were analyzed retrospectively and each sample contained two sequences of FSE TiWI and FS FSE T₂WI.?1?CNR and SNR values between images of FSE TiWI and FS FSE T₂WI in the experimental group were compared.According to the time of injury,113 samples were divided into 4 time groups(group 1:t?7 days;group 2:7 days<t?14 days;group 3:14 days<t?30 days;group 4:t?3 months.In each time group,the diseased vertebra was regarded as the observation group?U?,and the adjacent normal vertebra above the diseased vertebra was regarded as the control group?N?.Measure signal strength in ROI.?1?CNR and SNR values of FSE TiWI and FS FSE T₂WI sequence of U group and N group in four time group were calculated.Whether the differences in CNR and SNR values between the U group and the N group in four time groups were statistically significant were compared.?2?In each time group,the CNR and SNR values between the two sequences of U group were compared to see whether there were statistical differences,and the correlation between the changes of CNR and SNR values in the two sequences and the injury time was analyzed.Results?1?The CNR and SNR values of the vertebral bodies of all 4 time groups in the FSE TiWI sequence and the first 3 time groups in the FS FSE T₂WI sequence were significantly different between the U group and the N group?P<0.05?.?2?In each time group,CNR and SNR values of FSE TiWI and FS FSE T₂WI sequence in U group were statistically different?P<0.05?.The CNR and SNR values in FS FSE T₂WI sequences were higher than those in FSE TiWI sequences in all time groups.The CNR and SNR values of the U group in the FS FSE T₂WI sequence were negatively correlated with the fracture time?r=-0.165,P=0.014;r=-0.149,P=0.032?.In the fourth time group,there was no statistical difference in CNR and SNR values between the U group and the N group in the sequence of FS FSE T₂WI?P=0.079;P=0.219?.Conclusion Signal changes in MRI can reflect the healing process of traumatic vertebral compression fractures.And it can be used to roughly infer the fracture time and has certain guiding significance in the identification process of disability.