Validity Of Measuring Signal Intensity Of Disc And Nucleus Pulposus On Axial Mr To Evaluate Disc Degeneration

PURPOSE:To investigate the validity of measuring signal intensity of nucleus pulposus on axial MR to assess disc degeneration.Methods:Sixty-six people were included in our study.The midsagittal magnetic resonance(MR)images and mid axial MR of each lumbar disc will be selected from 66 subjects' T2W MR images.Image analysis program Spine Explorer was used to obtain mean and standard deviation(SD)of disc signal intensity measurements and average signal intensity of corresponding cerebral fluid(CSF)on midsagittal and midaxial MR images.Disc and nucleus puplosus signal intensity was adjusted by the average signal intensity of corresponding CSF before calculating correlations of disc signal intensity and age on midsagittal and midaxial MR images.Twenty sets of lumbar MRs were randomly selected from the sample pool and measured repeatedly by two authors(CMJ and HXJ)with an interval of two months to examine inter-rater agreement.Results:The inter-rater measurement reliability of sagittal MR images was moderate agreement(ICC=0.63 and 0.73),while the inter-rater measurement reliability of signal intensity on axial MRs was excellent(ICC>0.80).Both the mean and SD of CSF-adjusted disc signal intensiy measurements on mid sagittal MR were found to have higher correlations with age than those on midaxial images of disc and nucleus pulposus(r=-0.50 and-0.67,P<0.001).Additionally,mean CSF-adjusted disc signal intensity associated with age on midaxial MRs of nucleus pulposus(r=-0.41,P<0.01)while not on midaxial MRs of disc(P= 0.319).Furthermore,SD of CSF-adjusted disc signal intensity on midaxial MRs of disc associated with age(r=-0.41,P<0.01)while not on midaxial MRs of nucleus pulposus(P= 0.058).However,for lower lumbar region(L4-S1),signal intensity measurements of both disc and nucleus pulposus on axial MR tended to have no or bad correlations with age.Conclusion:Signal intensity measurements of disc on midsagittal MR reflected the degree of disc degeneration better than that on axial MR.Mean signal intensity of nucleus pulposus and SD of disc signal intensity on axial MRs have moderate correlations with age on upper lumbar region,with excellent inter-rater measurement agreement,and can be used as an ideal measure of disc degeneration.