Analysis Of CT&MRI Findings And Comparison Of MR Fat Suppression Techniques On Ankylosing Spondylitis

Objective:To analyze the CT and MRI manifestations of ankylosing spondylitis and compare the imaging quality of three MRI fat suppression techniques including STIR,SPAIR-T2 WI,and FS-T2 WI sequence.Materials and Methods:A total of 65 patients,both inpatients and outpatients,complying with inclusion and exclusion criteria were incorporated from December 2018 to October 2019 in our hospital.Disease courses,laboratory tests,MRI and CT findings of all patients were collected.The MRI sequence of oblique coronal T1 WI,STIR,FS-T2 WI and SPAIR-T2 WI were performed in 30 patients and the sequence of oblique coronal T1 WI,STIR and oblique axis FS-T2 WI were completed in 35 patients.Initially,CT and MRI manifestations of all included patients were observed individually and then the differences of CT and MRI manifestations in patients with different courses and disease activities and the imaging features of the two techniques of CT and MRI were compared.Next several parameters including the image uniformity(U),fat muscle relative signal-to-noise ratio(SNR),and contrast noise ratio(CNR)and image quality score were studied to make a comparison among these three fat suppression technologies.The measurements and scoring of all ROIs were completed by two radiologists and the average value was obtained after independent evaluation.Statistical analysis was performed using SPSS 25.0 software.Results:1.Imaging findings(1)Common CT and MRI manifestations of ankylosing spondylitis in sacroiliac joints,generally involved bilaterally,include bone erosion,osteophytes,osteosclerosis,bone cystic changes below the articular surface,bone marrow edema,fat deposits,articular cartilage lesions,joint space changes,and ankylosis.Relatively rare manifestations include joint effusion,L5/S1 articular process lesions,hip joint involvement,and swelling of surrounding soft tissues.(2)As for imaging manifestations of AS in sacroiliac joints,there were statistical significances among patients with different disease activities with respects to bone erosion,sub-articular bone cystic changes,joint space changes,bone marrow edema and articular cartilage lesions on MRI(P <0.05)and joint stiffness on CT(P <0.05).The differences in bone erosion,sub-articular bone cystic cysts,bone marrow edema,fat deposition and articular cartilage lesions were statistically significant in patients with different disease courses(P <0.05).Comparison of two patients before and after treatment revealed that MRI could show changes in BME.(3)Compared with CT analysis,the ability of MRI to detect lesions was higher than CT(P<0.05)in general.MRI was better in detecting bone erosion,bone cystic changes under the articular surface,L5 / S1 articular process lesions,and soft tissue swelling(P<0.05);CT was better than MRI in detecting osteophytes(P<0.05);CT and MRI showed no significant difference in detection of joint space changes and joint ankylosis.2.Comparison of MR fat suppression technologies(1)Image uniformity(U):There were statistical differences between he left and right side of U in FS and SPAIR sequence as opposed to STIR sequence of which no statistical differences were found.The U of the three fat suppression sequences on the same side was statistically significant(P<0.05).(2)Relative signal-to-noise ratio(rSNR)and contrast-to-noise ratio(rCNR)of fat and muscle: The differences of rSNR and rCNR in FS and SPAIR sequences were statistically significant(P <0.05),while the differences of rSNR and rCNR in STIR sequences were of no significance.The the differences of rSNR and rCNR of the three fat suppressing sequences on the same side was statistically significant(P<0.05).(3)signal-to-noise ratio,contrast-to-noise ratio and their SPARCC score of bone marrow edema lesions: The differences of SNR and CNR in the three fat-suppressed sequences were statistically significant(P<0.05),but there was no significant difference in SPARCC scores.(4)Subjective scores of image quality: the intrareader and inter-reader reliability appeared prrety good in uniformity of fat suppression and overall image quality scores(ICC:0.816-0.895),good in artifact scores((ICC:0.672-0.725),and excellent in noticeability scores of lesions(ICC:0.912-0.997).The intrareader reliability was prrety good in anatomical structure scores(ICC: 0.851-0.893),in which the intrareader reliability of the STIR and FS sequence was prrety good(ICC: 0.825-0.874)and the intrareader reliability of the SPAIR sequence was excellent(ICC: 0.914).The differences in the scores of the three fat suppression sequences on fat suppression uniformity,artifacts,anatomical structure,lesion noticeability and overall image quality were statistically significant(P <0.05).(5)Scanning orientation: The oblique coronal imaging shows the articular surface and joint space more clearly and distinctly than the oblique axial imaging,but there is no significant difference between them in detecting lesions.Conclusion:1.CT and MRI manifestations of AS in sacroiliac joint are diverse.The diagnostic information detected by MRI is significantly better than CT,which can provide strong evidence for early diagnosis and treatment of AS.2.STIR,FS,and SPAIR sequences can be used for sacroiliac joint scanning of AS,while oblique coronal scanning of STIR sequences is the best.