Quantitative Evaluation Of MRI And Preliminary QCT Study Of Early Sacroiliac Arthritis In Axial Spondyloarthritis

Part one Quantitative MRI evaluation of early sacroiliac arthritis in Axial SpondyloarthritisBackgroundSpondyloarthritis（Sp A）is a group of chronic inflammatory rheumatic diseases,which consists of two types:axial spondyloarthritis（axSpA）and peripheral spondyloarthritis.Ax Sp A includes ankylosing spondylitis（AS）and non-radiographic axial Sp A（nr-axSpA）,of which AS is the most common and the classic prototype of axSpA.Magnetic resonance imaging（MRI）is currently the most sensitive imaging technology to detect early sacroiliac arthritis.MRI of the sacroiliac joint has been included in the diagnostic guidelines for spinal arthritis,but there are few reports on the application of combined functional imaging techniques IVIM-DWI and IDEAL-IQ in early axSpA.Therefore,in this study,IVIM-DWI and IDEAL-IQ sequences were used to study the changes of microcirculation perfusion and fat content of sacroiliac joint in the early stage of sacroiliac arthritis of axSpA.ObjectiveTo investigate the quantitative evaluation efficacy of IVIM-DWI and IDEAL-IQ in the quantitative evaluation of sacroiliac joint active inflammation in patients with early axial spondyloarthritis.MethodsA total of 37 patients diagnosed with early sacroiliac joint disease due to low back pain from October 2020 to December 2021 in our hospital（29 patients with AS group and 8patients with nr-axSpA group）were prospectively collected.All patients met the Ankylosing Spondylitis Disease Activity Score（ASDAS,2009）set by Assessment of Spondyloarthritis International Society（ASAS）.In the same period,20 healthy volunteers were recruited,and clinical data,such as age,gender,course of disease,CRP,ESR and other laboratory indicators,were collected.All subjects underwent sacroiliac joint 3.0T MRI,including conventional MRI,IVIM-DWI and IDEAL-IQ functional imaging sequences.According to axSpA classification criteria,the patients were divided into AS group and non-ankylosing spondylitis（NAS）group.Further more,the AS patients were divided into the positive group（n=29）and negative group（n=29）according to the bone marrow edema of sacroiliac joint.The IVIM-DWI and IDEAL-IQ related parameters,such as apparent diffusion coefficient(D_stand),slow apparent diffusion coefficient(D_slow),fast apparent diffusion coefficient(D_fast),pseudo diffusion coefficient（f）and fat fraction（FF）were measured,and reconstruct IVIM-DWI pseudo color image in the AS edema area group,AS non-edema area group,NAS group and control group.One-factor analysis of variance was used to analyze the statistical differences of parameters among the 4groups.The ROC curve was drawn to analyze the diagnostic efficiency of each parameter for early sacroiliac joint lesions.The normality of the data was analyzed using the Shapiro-Wilk test.Spearman correlation coefficient was used to evaluate the correlation between IVIM-DWI parameter values and IDEAL-IQ parameter values.p（27）0.05 was statistically significant.Result（1）Comparison of parameter values in IVIM-DWI and IDEAL-IQ sequences:The D_stand,D_slow,D_fast,f and FF among AS edema area group,AS non-edema area group,NAS group and control group were normal distribution.The mean values of D_stand,D_slow,D_fast,f and FF were[（0.89±0.35）×10^-3mm2/s,（0.95±0.27）×10^-3mm2/s,（98.86±26.94）×10^-3mm2/s,（0.28±0.03）,（38.38±13.99）%]in the group of AS,and were[（0.62±0.13）×10^-3mm2/s,（0.59±0.18）×10^-3mm2/s,（117.65±14.21）×10^-3mm2/s,（0.22±0.03）,（73.90±8.95）%]in AS non-edema area group,and were[（0.61±0.12）×10^-3mm2/s,（0.87±0.22）×10^-3mm2/s,（122.92±12.47）×10^-3mm2/s,（0.26±0.04）,（67.15±8.51）%]in NAS group,and were[（0.59±0.04）×10^-3mm2/s,（0.73±0.17）×10^-3mm2/s,（133.28±5.69）×10^-3mm2/s,（0.25±0.02）,（62.38±8.44）%]in control group.There were significant differences in all parameters among the sacroiliac joint edema of AS group and the non edema of sacroiliac joint of AS group（p<0.05）.The comparison between the two groups showed that the values of D_stand,D_slowand f in the edema area group were higher than those in other groups,and there were significant differences（p<0.05）;The values of D_fastand FF in the edema area group were lower than those in other groups（p<0.05）.（2）Comparison of the diagnostic efficacy of IVIM-DWI and IDEAL-IQ sequences:When the optimal cut-off values of D_stand,D_slow,D_fast,f and FF were 0.74×10^-3mm2/s,0.67×10^-3mm2/s,103.71×10^-3mm2/s,0.27 and 57.71%,the AUCs for predicting sacroiliac joint lesions in patients with early axial spondyloarthritis were 0.77（95%CI:0.65-0.86,p<0.001）,0.81（95%CI:0.70-0.89,p<0.001）,0.78（95%CI:0.67-0.87,p<0.001）,0.64（95%CI:0.52-0.75,p=0.037）and 0.98（95%CI:0.91-0.99,p<0.001）,with the sensitivities of 65.52%,93.10%,55.17%,37.39%and 96.55%,and the specificities of90.48%,61.90%,90.48%,88.10%and 88.10%,respectively.D_stand,D_slow,D_fastand FF had good diagnostic efficiency.The AUCs of D_stand+FF,D_slow+FF,D_fast+FF,f+FF were0.99（95%CI:0.98-1.00,p<0.001）,0.99（95%CI:0.98-1.00,p<0.001）,0.99（95%CI:0.97-1.00,p<0.001）and 0.99（95%CI:0.97-1.00,p<0.001）,with the sensitivities of 93.10%,96.55%,96.55%and 96.55%,and the specificities of 93.10%,93.10%,96.55%and93.10%,respectively,it shows that the combination of IVIM-DWI and IDEAL-IQ sequence has better diagnostic efficiency.（3）Correlation analysis of IVIM-DWI correlation coefficient and IDEAL-IQ FF value in axSpA patients:Spearman correlation analysis showed that D_standand D_slowwere negatively correlated with FF,and the correlation coefficients were-0.460（p=0.000）,-0.440（p=0.000）and-0.331（p=0.005）,respectively.D_fastwas positively correlated with FF,and the correlation coefficients were 0.359（p=0.002）.Conclusion（1）IVIM-DWI could quantitatively reflect the changes of water molecules diffusion and microcirculation perfusion and fat content of early sacroiliac joint axial spondyloarthritis.（2）IDEAL-IQ could quantitatively reflect the changes of fat content of early sacroiliac joint in axial spondyloarthritis.（3）The D_stand,D_slow,D_fastand FF of IVIM-DWI and IDEAL-IQ had good diagnostic efficiency,the combination of IVIM-DWI and IDEAL-IQ sequence was more conducive to the diagnosis and evaluation of early sacroiliac joint axial spondyloarthritis,and can provide effective imaging markers for patients with early sacroiliac arthritis.Part two Preliminary study on QCT of sacroiliac arthritis in Axial SpondyloarthritisBackground Axial spondyloarthritis（axSpA）with typical pathological features of sacroiliitis,spondylitis,discitis and posterior spinal inflammation is a chronic inflammatory disease,leading to bone remodeling,reactive sclerosis and absorption,and new bone formation.The osteoporotic fracture of the sacrum in axSpA characterized by atypical clinical manifestations and easily confused with neoplastic diseases of the sacrum.Currently,there have been few studies on quantitative computed tomography（QCT）measurement of bone mineral density（BMD）in the sacrum of axSpA.This study intended to investigate the changes and the influence factors of sacral BMD in axSpA according to QCT.Purpose The aim of this study is to provide a new technique for sacral BMD assessment and fracture risk prediction in axSpA according to exploring the correlation between BMD of sacrum and lumbar vertebra in axSpA and the influence factors of sacral BMD in axSpA by OCT.Methods83 patients who met the diagnostic criteria of the International Working Group on Evaluation of Spine Arthritis in 2009 were prospectively collected as axSpA group.37 ageand gender-matched healthy volunteers were collected as control group.Clinical data（such as age,gender,and duration of the disease）,C-reactive protein（CRP）,erythrocytesedimentation rate（ESR）and other laboratory indicators were collected.Ax Sp A group and the control group both underwent CT examination of the chest and sacroiliac joint（SIJ）,while axSpA group underwent MRI examination of SIJ.CT images of the chest and SIJ were imported into QCT Pro BMD software to measure BMD of lumbar vertebra（T12-L2）and sacrum（S1-S3）.Vertebral BMD ￡ 80 mg/cm~3 was defined as osteoporosis according to QCT diagnostic guidelines for osteoporosis.The two physicians separately practiced radiographic grade at the sacroiliac joint（SIJ）of patient according to the AS New York standard（0-4 grades）revised in 1984.In case of disagreement,SIJ CT grade was conducted after consultation with a third physician.The differences in age,gender and BMD between the axSpA group and the control group were compared using independentsample t-test.The differences in BMD between the spine,sacral lateral mass and sacral central region subgroups and between the different SIJ CT grades subgroups were compared by analysis of variance,and the least significant difference method was used for pairwise comparison.To evaluate the correlation between the patients’ BMD of sacrum and spine by Pearson correlation analysis.To evaluate the effects of age,gender,disease course,CRP,and ESR in BMD of sacrum in axSpA using multivariate linear regression analysis.p（27）0.05 was statistically significant.Result（1）32/83（38.6%）and 18/83（21.7%）in the axSpA group respectively met osteopenia and osteoporosis,while 3/37（8.1%）and 0 in the control group.The incidence of osteopenia and osteoporosis in axSpA patients was significantly higher than that in the control group（X~2osteopenia = 4.345,p < 0.05;X~2osteoporosis = 4.540,p < 0.05）.（2）The BMD of T12–L2 and S1–S3 in the axSpA group were[（151 ± 38）mg/cm~3,（153 ±41）mg/cm~3,（150 ± 36）mg/cm~3,（104 ± 42）mg/cm~3,（72 ± 34）mg/cm~3,（82 ± 39）mg/cm~3 ].The BMD of T12–L2 and S1–S1 in the control group were [（167 ± 25）mg/cm~3,（170 ± 25）mg/cm~3,（162 ± 30）mg/cm~3,（131 ± 29）mg/cm~3,（120 ± 9）mg/cm~3,（123 ± 24）mg/cm~3].The BMD of lumbar vertebra and sacrum in the axSpA group were lower than that of the control group（t T12 = 1.994,p < 0.05;t L1 = 2.058,p < 0.05;t L2 =1.288,p < 0.05;t S1 = 3.151,p < 0.05;t S2 = 9.438,p < 0.05;t S3 = 5.297,p < 0.05）.The BMD of lumbar vertebra and sacrum were decreased gradually in the two groups.The BMD of sacral lateral mass in the axSpA group and the control group respectively was lower than the BMD of sacral central region[（55 ± 33）mg/cm~3 vs.（143 ± 44）mg/cm~3,t=-12.371,p < 0.05;(97 ± 17mg/cm~3 vs.（178 ± 31）mg/cm~3,t = 7.373,p < 0.05].The BMD of the lateral mass and central region of the sacrum in the axSpA group respectively was lower than that of the control group（t =-7.618,p < 0.05;t =-3.721,p < 0.05）.The sacral BMD with bone marrow edema area of axSpA was lower than that of the normal area[（105 ± 20）mg/cm~3 vs.（137 ± 36）mg/cm~3,p < 0.05].The BMD of sacrum among the subgroups with different SIJ CT grades showed statistical difference（F = 23.496,p（27）0.05）,and the BMD gradually decreased with the increase of CT grade [ Grade 0:（131± 30）mg/cm~3,Grade 1:（121±14）mg/cm~3,Grade 2:（88 ±26）mg/cm~3,Grade 3:（63 ± 24）mg/cm~3,Grade 4:（54 ± 21）mg/cm~3 ].The results showed that there was no significant difference in BMD between Grade 0 and Grade 1（p = 0.904）,but there were significant differences among the other grades（p（27）0.05）.（3）15/39（38.5%）were complicated with osteopenia and 3/39（7.7%）were complicated with osteoporosis in axSpA within one year.11/26（42.3%）were complicated with osteopenia and 6/26（23.1%）were complicated with osteoporosis in axSpA for one to five years.6/18（33.3%）were complicated with osteopenia and 9/18（50%）were complicated with osteoporosis in axSpA for more than five years.There was no statistical difference in the incidence of osteopenia between the subgroups with different courses of disease（p >0.05）.There was a statistical difference in the incidence of osteoporosis（p < 0.05）,and the result displayed that the incidence of osteoporosis in axSpA patients for more than five years was higher than that within one year.（4）Pearson correlation analysis showed that there was a good correlation between the BMD of the lumbar vertebra and sacrum in the patients with axSpA（r = 0.665,p = 0.001）.The detection rate of abnormal sacral BMD of axSpA detected by QCT was higher than that of lumbar vertebra（65.9% vs.50.6%,X~2 = 0.403,p < 0.05）.（5）The regression model was statistically significant（F = 3.787,p < 0.05,adjusted R2 =0.218）.Multiple linear regression analysis showed that age（t =-2.184,p = 0.034）,course of disease（t =-2.161,p = 0.036）and CRP（t = 2.167,p = 0.036）were the risk factors for sacral BMD of axSpA.Conclusion（1）Osteopenia or even osteoporosis existed in the sacrum and lumbar vertebra of axSpA.The axSpA with a long course of disease（> 5 years）had a higher risk of osteoporosis.（2）There was a moderate positive correlation between the BMD of the lumbar vertebra and sacrum in the patients with axSpA.（3）Age,course of disease and CRP value were the risk factors for osteopenia and osteoporosis in axSpA.