The Value Of T2 Star Mapping Imaging Of Sacroiliac Joints In The Assessment Of AS Patients

BACKGROUNDAs the most common seronegative spondyloarthropathy,AS mostly involves people aged 10 to 40 years,especially the peak incidence of age 20 years old.The ratio of male to female is about 5: 1,almostly 100% involving the sacroiliac joints.The patients usually complain of progressively chronic lower back discomfort,pain,and morning stiffness.More than 90 percent of patients with AS express positive for HLA-B27,and CRP and ESR often increases in acute stage.The etiology is unknown and the pathogenesis is often considered to be related to gene,bacterial infection,immunological abnormalities and other factors.The pathological features of AS is a kind of non-specific inflammation,mainly involving the attachment sites.The patients can feel pain and tenderness at the positions of sacroiliac joints,pubic symphysis,spine spinous process,iliac crest,large rotor,ischial tubercle,tibial tubercle and calcaneal nodules in the active stage.The patients with negative expression of HLA-B27 have an older age incidence,milder symptom,fewer family cluster than the positive patients.AS presents chronic progression in early stage,which will lead to spinal bony rigidity later and seriously affecting the quality of life of patients.The sacroiliitis of patients with AS is divided into active and chronic inflammation,the active including bone marrow edema,synovitis,enthesitis,the chronic including cartilage erosion,bone sclerosis,fat deposition,stiffness and so on.The therapeutic drugs of AS includes NSAIDs(nonnon-steroidal anti-inflammatory drugs),DMARD(disease-modifying anti-rheumatic drugs),and TNF-α(tumor necrosis factor-αinhibitor)which have a different effect in the aspects of controlling inflammatory activity,and improving the prognosis.The patients with different condition need different drugs.Therefore,it is necessary to evaluate the patient’s disease activity and chronic inflammatory structure changes objectively,which is helpful to choose drugs reasonablely.At present,the common means used includes patient or clinician assessment and laboratory examination,which subjective or traumatic,is not suitable for long-term review.Compared with traditional X-ray and CT,MRI is considered to be the most sensitive method to diagnose AS,which is also commonly used in the assessment of AS patients.With the development of new MRI technology,quantitative MRI technology which is simple,noninvasive,clear and objective is increasingly applied to the clinical diagnose and treatment.As a quantitative functional imaging technique,T2 / T2 * mapping imaging has been largely studied in the functional cartilage imaging,especially degenerative osteoarthritis.The studies on the T2 * mapping of the sacroiliac articular cartilage are rare in the literature.Zhen Tao et.al have shown that the differenation of subchondral bone marrow T2 value between the early sacroiliac arthritis patients and lower back pain patients contribute to early diagnosis of AS.Therefore,two parts were included in the present study.The first part studied the morphological and molecular changes of the sacroiliac cartilage in patients with AS and the correlation with radiologic grade by the T2* mapping of cartilage;the second part explored the value of T2* values of subchondral bone marrow to the assessment of active sacroiliitis.The part one:The Value of T2*mapping of Sacroiliac Joint Cartilage in the Evaluation of AS Patients ObjectiveTo study the morphological and molecular changes of the sacroiliac cartilage in patients with AS by the T2* mapping of cartilage and the correlation with radiologic grade and CRP、ESR、VAS 、BASFI、BASDAI、SPARCC.Methods94 patients with AS according to 2009 ASAS recommended axial spine arthritis classification criteria from department of rheumatology of our hospital were collected from October 2014 to August 2015.All patients received the examination of sacroiliac joint in the 3.0T Siemens Verio MRI scanners.The scanning sequences included FSET1 WI,FSET2WI,STIR T2 WI at the positon of oblique coronal plane,axial STIR T2 WI and oblique coronal T2* Mapping sequences.All images were conveyed to post-processing software on the workstation of Siemens Syngio via.The pseudo-color images of T2* value of all patients were integrated with the anatomical pattern and the image contrast were manually adjusted to show the clearest sacroiliac articular cartilage.The signal strength,shape and edge of different radiographically-grade cartilages were observed to find the most complete cartilage plane and depict cartilage contours to measure the average T2* value.The ESR,C-reactive protein(CRP),Bath ankylosing spondylitis function index(BASFI),Bath ankylosing spondylitis Activity index(BASDAI),overall patient evaluation(VAS)were collected at the same time(within one week).ResultA total of 94 patients were included in this study.The ration of maleand female were 3.27: 1,age ranging from 16 to 50 years old.The average age is 30±7.85 years old.There were 9 of 188 sacroiliac joints cartilages classified for 0 grade with an average cartilage T2* value of 8.18±1.19,and the cartilage showed smooth and linear high signal with a clear boundary to the surrounding bone marrow;14 for grade I,with an average cartilage T2* value of 12.99 ± 2.81,and cartilage displayed linear high signal with local "small dendritic" bifurcation;21 for grade II,with an average cartilage T2* value of 14.12 ± 3.34,and local "small dendritic" bifurcation of cartilage increased;76 for grade III with an average cartilage T2*value of 14.33 ± 3.97,and the "small dendritic" bifurcation of cartilage was increased and thickened and partial cartilages atrophied and decreased;68 for grade IV,most of the cartilages were disappeared and few left a small amount of cartilage.The T2*value of cartilage increased from grade I to grade III and there were significant differences between both grades except grade I and grade II,grade II and grade III(p<0.05).There were no significant correlations between the average T2*value of the sacroiliac joints cartilage and the ESR,CRP,BASDAI scores,BASFI scores and SPARCC scores in patients with grade 0 ~ Ⅲ.ConclusionT2 star mapping cartilage imaging can not only show the morphology,volume,edge,lack of subtle structure of the sacroiliac articular cartilage of the patients with AS,but also quantitatively reflect the degenerative degree of the sacroiliac articular cartilage which provides a quantitative and objective method that contributes to the comprehensive and objective assessment of the condition of AS patients and of the efficacy and prognosis of the relevant drugs,as well as an effective assessment and detection tool for future treatment of cartilage transplantation for patients with AS.The part two:The value of subchondral medullary T2 star value in evaluating sacroilitis of ASObjectiveTo measure subchondral medullary T2 star value of sacroiliac joins in ankylosing spondylitis and explore its relationship with common MRI manifestatons and SPARCC score and clinical relevance.MethodsCommon sacroiliac joins MR images and T2 star maps were obtained in 41 patients with AS conformed by rheumatological specialist in our hospital.Subchondral medullary T2 star values of sacroiliac facet were measured and the clinical data in the same period(during a week),including SPARCC、ESR、CRP、BASFI、BASDAI、VAS,was cellected.The relationship of medullary T2 star value with clinical data was analyzed with Spearmen correlation analysis.ResultsThere was positive relationship between subchondral medullary T2 star value and BASDAI and VAS(r=0.449 and 0.470,p=0.003 and 0.002,repectively).Other indexes had no significance relationship with medullary T2 star value.ConclusionsSubchondral medullary T2 star value of sacroiliac joins can reflect conditions of sacroiliitis,providing a noninvasive and quantitative tool for disease activity assesement of those patients with AS.