Multimodal Quantitative Evaluation Of Lumbar Intervertebral Disc Degeneration And Low Back Pain With Synthetic MRI

Purpose: With the aging of the population,the incidence of lumbar degenerative diseases is increasing.Lumbar intervertebral disc degeneration can cause low back pain and various degrees of dysfunction,causing trouble to daily life,affecting sleep and even leading to disability,which causes a heavy economic burden to society and families.As the most commonly used examination,MRI plays an important role in the diagnosis of lumbar intervertebral disc diseases.However,the diagnoses depend on conventional MR sequences are subjective and more dependent on equipment and doctors,lack of quantitative standards,and can barely indicate the changes inside intervertebral disc.In recent years,several quantitative MRI techniques have proved to be useful for evaluating disc degeneration,especially for early degeneration.But the diagnostic effect varied according to different articles.To get a comprehensive evaluation of disc degeneration,some studies preferred to make multi-quantitative sequences for better diagnosis.However,the time-consuming scanning time prevented the application of multiple quantitative sequences in clinical practice.Therefore,we need a more superior quantitative MRI sequence to optimize both the scanning time and clinical diagnosis.Synthetic MRI is a novel imaging technique that can generate multiple relaxation weighted images as well as quantitative relaxation maps from a single acquisition;by shortening the entire scanning time,it increases clinical feasibility.The quantitative data,including T1,T2 and proton density(PD)values,which represent the physical properties of the tissue are calculated from the raw data.Then,the quantitative data are used to calculate the pixel signal intensities that produce multiple relaxation-weighted images.At present,there was no research on the evaluation of synthetic MRI of lumbar disc degeneration.In the first part of our study,we aimed to investigate the feasibility of synthetic MRI of the lumbar spine by comparing the subjective and objective image quality and the agreement for detection of disorders of lumbar spinal lesions between synthetic and conventional MRI at 3.0T.It can provide a basis for the clinical application of synthetic MRI in lumbar vertebrae.On this basis,the second part of our study investigate the utility and reliability of synthetic MRI for evaluating lumbar intervertebraldisc degeneration in patients with low back pain and to establish a reliable quantitative scale based on the Pfirrmann grade.Furthermore,in the third part,we analyzed the correlation between the multi-quantitative parameters and the clinical scales among the patients with low back pain,and compare the patients with acute and chronic low back pain.It can help explore the mechanism and pathological changes of low back pain and find new methods treatment of acute and chronic low back pain.Methods: In the first part of the study,84 patients were included and scanned by GE Signa Pioneer 3.0T MR.All subjects underwent conventional T1 WI,T2WI,short tau inversion recovery(STIR)sequence and synthetic MRI.Analyses were performed to generate synthetic T1,T2 and STIR sequences using the MRI console with the MRI compilation modules.We made comparisons between the conventional and synthetic sequences:(1)Objective image quality,including signal intensity,noise,signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR);(2)Subjective image quality,including artifact,spatial resolution,contrast,liquid signal intensity and fat suppression;(3)the consistency of disease diagnosis.In the second part of this study,85 patients underwent MR examinations of the lumbar spine including sagittal T2 WI,axial T2 WI and synthetic MRI on GE Signa Pioneer 3.0 T MR.The T1,T2 and PD mappings were generated from the synthetic MRI.For L1-2 to L5-S1,we measured the T1,T2 and PD values of annulus fibrosus and nucleus pulposus and classified each intervertebral disc based on Pfirrmann grade.The following analyses were made:(1)Correlation of age,lumbar segment with Pfirrmann grade and T1,T2 and PD values;(2)Evaluation of T1 T2 and PD values on identifying between each lumbar Pfirrmann grade,separately and comprehensively;(3)Calculate the receiver operating characteristic curve(ROC curve)and get the cut-off values and p values,and then compare the area under curve(AUCs).The third part of this study included 51 patients who were asked the visual analogue scale(VAS)and Oswestry disability index(ODI)scale.They underwent the sagittal T2 WI,sagittal and axial synthetic MRI.All the discs were classified based on Pfirrmann grade.The T1,T2 and PD values were measured on each disc and bilateral paravertebral muscles.Analyses were made as follows:(1)Comparisons of the clinical data and VAS,ODI between ALBP and CLBP groups;(2)Correlation of VAS and ODI with thequantitative values of discs and paravertebral muscles in ALBP and CLBP groups,respectively;(3)Comparison of the quantitative values between ALBP and CLBP groups.Results: 1.The signal intensity and noise of the synthetic sequences were much higher than those of the conventional sequences;The SNR of spinal canal and fat in synthetic sequences were higher than those in conventional sequences,while the opposite results were found in the vertebral body and disc.The CNRs between the two groups were not significant.For the subjective score,the artifact and spatial resolution of synthetic MRI were lower than those of conventional MRI,especially in STIR images.But the former has better liquid signal intensity and fat suppression.There was no statistical difference in the detection rates of the diseases.2.It showed a negative correlation between age and Pfirrmann grade,PD value of the anterior annulus,T1,T2 and PD values of the nucleus pulposus and the T2 and PD values of the posterior annulus.Except for the T2 value of the anterior annulus,other T1,T2 and PD values of the discs were negatively correlated with Pfirrmann grade.The distribution of lumbar segments varied at all Pfirrmann grades,with the lower lumbar segments(L4-S1)accounting for a greater proportion of the severe degenerated discs.3.The T1,T2 and PD values of nucleus pulposus,the T1 and PD values of posterior annulus fibrosus were the effective parameters in distinguishing between the Pfirrmann grades,separately.In the comprehensive evaluation of these parameters,only the T2 and PD values of the nucleus pulposus were statistically significant.The ROC curves of T2 and PD showed that the AUCs of T2 value between grade II-III and IV-V were higher than those of PD value,while there was no significant difference between grade I-II and III-IV.4.No difference was found in the clinical data and VAS and ODI scales between acute and chronic low back pain groups.The T1 value of anterior annulus fibrosus and the T1 and T2 values of nucleus pulposus in chronic low back pain group were significantly higher than those in acute low back pain group,while the result was opposite for the T2 value of psoas.5.For VAS,it was positively correlated with the Pfirrmann grade in ALBP group and with height in CLBP group.In the respect of ODI,it was positively correlated with BMI in ALBP group,while it was negatively correlated with age and Pfirrmann grade inCLBP group.6.In ALBP group,the VAS was negatively correlated with the cross-sectional area of the psoas major,but positively correlated with the T2 value of the multifidus muscle.The ODI showed a negative correction with the T1,T2 and PD values of nucleus pulposus,and a positive correction with the T2 value of posterior annulus fibrosus.In CLBP group,the VAS was positively correlated with the T1,PD values of posterior annulus fibrosus,while the ODI was positively correlated with the T2 value of posterior annulus fibrosus.Conclusion: 1.Through the subjective and objective evaluation of the image quality of conventional and synthetic MR sequences,it proved that compared with the conventional MR,the synthetic MR provides morphologic sequences with acceptable image quality and a good consistency for detection of spinal lesions.Our study provides a basis for the clinical application of synthetic MRI in lumbar related diseases.2.Our study applied the synthetic MRI to comprehensively explore the age,lumbar segments,Pfirrmann grade,and the T1,T2 the PD values.We found that the synthetic MRI could accurately detect the early changes of lumbar disc degeneration,as well as effectively evaluating the process of disc degeneration,which helped clinical doctors for effective intervention and provide the basis for further unified quantitative standard.3.In our study,the quantitative analysis of young and middle-aged patients with acute and chronic low back pain was conducted by using synthetic MRI.The results showed that there was a correlation between the quantitative values of disc and paraspinal muscles and VAS and ODI scales.These quantitative parameters could be used as effective diagnostic indicators for identification of patients with low back pain.It has a great significance for exploring the pathogenesis and pathological changes of low back pain and selecting optimal treatment of patients with acute and chronic low back pain.