Clinical Value Of ¹⁸F-FDG PET/CT For The Evaluation Of Rheumatic Disease

Rheumatic disease（RD）is a group of systemic autoimmune diseases involving multiple systems,based on the pathological changes of chronic inflammation of blood vessels and connective tissue.In recent years,with the development of rheumatology,conventional laboratory and imaging diagnostic methods can no longer meet the clinical needs.¹⁸F-FDG PET/CT can reflect the active state and systemic involvement range of inflammatory diseases in terms of functional imaging,and provides highly sensitive,semi-quantitative imaging at a molecular level,revealing the important pathophysiological processes underlying inflammation.It is increasingly used to diagnose inflammatory diseases such as rheumatic diseases and monitoring these diseases,showing a good application prospect.This retrospective study explored the clinical value of ¹⁸F-FDG PET/CT in evaluating rheumatic diseases such as systemic vasculitis,rheumatoid arthritis,rheumatoid polymyalgia and dermatomyositis,in order to provide more meaningful information for clinical practice.Part ⅠClinical value of ¹⁸F-FDG PET/CT in assessing anti-neutrophil cytoplasmic antibodies-associated vasculitis.Purpose To explore the clinical value of ¹⁸F-FDG PET/CT in assessing anti-neutrophil cytoplasmic antibodies-associated vasculitis（AAV）in systemic vasculitis.Materials and methods Fifteen patients with AAV between January 2013 and January 2018 were retrospectively analyzed.There were 6 patients diagnosed as granulomatosis with polyangitis（GPA）,7 diagnosed as microscopic polyangiitis（MPA）and 2 diagnosed as eosinophilic granulomatosis with polyangiitis（EGPA）.All the patients underwent ¹⁸F-FDG PET/CT scan.The range and image features of the positive lesions were observed and recorded and the maximum standard uptake values(SUV_max)were measured.The relationship between the SUV_max and C-reactive protein（CRP）was analyzed with Pearson correlation.The SUV_max and the number of lesion sites were compared by two-sample t test between the CRP-elevated and CRP-normal patients.Results 56 lesions in the 14 of 15 AAV patients were detected by PET/CT.The positive findings distributed in 15 tissues and organs,including the nasopharynxes（n=9）,lungs（n=9）,kidneys（n=8）,spleens（n=6）,lymph nodes（n=6）,bone marrow（n=4）,skin（n=3）,prostates（n=2）,aortas（n=2）,vertebral soft tissues（n=2）,orbita（n=1）,parotid gland（n=1）,thyroid gland（n=1）,liver（n=1）and pancreas（n=1）.The60.7%（34/56）of lesions were clinically unsuspected occult lesions.GPA lesions mainly invaded the nasopharynxes,lungs and kidneys;MPA lesions mainly invaded the kidneys and spleens;EGPA lesions mainly invaded the nasopharynxes,lymph nodes and bone marrow.There was no significant correlation between the level of CRP and the SUV_max of AAV lesions（r=0.462,P=0.083>0.05）.No differences in the SUV_max were observed between patients with elevated CRP levels and those with normal CRP levels（t=1.451,P=0.170>0.05）.But more lesion sites were observed in patients with elevated CRP（t=3.456,P=0.004<0.05）.Conclusion ¹⁸F-FDG PET/CT shows positive findings in multiple sites in AAV patients,including clinically unsuspected sites.This fingdings suggest that the disease may be more extensive than clinical predictions.This imaging technique may be an useful tool for diagnosis and evaluation of AAV.Part ⅡAnalysis of aortic ¹⁸F-FDG uptake in patients suffering from large vessel vasculitis and anti-neutrophil cytoplasmic antibodies-associated vasculitisPurpose To explore the clinical value of ¹⁸F-FDG PET/CT in assessing the aortic wall involvements of large vessel vasculitis and anti-neutrophil cytoplasmic antibodies-associated vasculitis in systemic vasculitis patients.Materials and methods Retrospectively analysis the clinical information and PET/CT imaging of 15 patients with large vessel vasculitis（LVV）.The FDG uptake of aorta and its branches were assessed.15 patients with antineutrophil cytoplasmic antibody associated vasculitis（AAV）were included as positive controls and 10healthy peoples were used as healthy controls（HC）.PET results were evaluated by visual and semi-quantitative analysis.Aortic ¹⁸F-FDG uptake was blood-normalized by dividing the SUV_max of the aorta by the SUV_mean of the blood pool in the vena cava,known as the TBR_max.The TBR_max of the most diseased aortic segment and the mean TBR_max of the whole aorta were compared among the three groups using one-way ANOVA analysis.And the correlation between the aortic ¹⁸F-FDG uptake and CRP or erythrocyte sedimentation rate（ESR）at the time of scanning was analyzed by Pearson analysis.Results The aortic ¹⁸F-FDG uptake in patients with LVV was mainly grade II（8/15,53.3%）and grade III which was higher than liver uptake（7/15,46.7%）;AAV group was mainly grade II which was similar to liver uptake（11/15,73.3%）;and HC group was mainly grade I which was lower than the level of liver uptake（9/10,90%）.The TBR_max of the most diseased segment and the mean TBR_max were significantly higher in LVV group and AAV group than in HC group（P<0.05）;LVV group was tend to be higher than that of AAV group,but this did not reach statistical significance（P>0.05）.In group AAV,the highest FDG uptake was in abdominal aorta,which was significantly higher than that of ascending aorta and descending aorta wall.But other groups didn’t see this phenomenon.The FDG uptake of the aortic wall showed a good correlation with CRP and ESR（P<0.05）.Conclusion In diagnosing of LVV,¹⁸F-FDG PET/CT not only has important value in the diagnosis and evaluation of LVV,but can accurately detect and judge the presence of macrovascular involvement in AAV.It has an irreplaceable advantage for comprehensive evaluation of the inflammatory activity and extent of aortic wall involvement in systemic vasculitis.Part ⅢThe clinical value of ¹⁸F-FDG PET/CT in assessing of rheumatoid arthritisPurpose To evaluate the value of ¹⁸F-FDG PET/CT in evaluating the involvement of large proximal joints and trunk joints of limbs in rheumatoid arthritis（RA）.Materials and methods The clinical information and ¹⁸F-FDG PET/CT imaging of34 clinically diagnosed RA patients were retrospectively analyzed.In the PET/CT features,the involvement of the large proximal joints and trunk joints,the imaging features of the involved joints and ligaments,the SUV_max of the lesions and the extraarticular complications were observed and recorded.Pearson correlation analysis was performed on FDG metabolism and the number of lesions involved with CRP and ESR separately.Pearson correlation analysis was also made between the duration of disease（month）with the FDG uptake and the number of lesion involved.All patients were divided into trunk involvement group and non-trunk involvement group according to the location of joint involvement.In addition,they were divided into rheumatoid active group and non-active group.Two independent t-test samples were used to analyze the joint involvement between the two groups.Results PET/CT imaging was positive in 30 of 34 RA patients（88.24%,30/34）.85lesions were involved,most of which were in the proximal extremity joints,accompanied by the involvement of the sternoclavicular joints,the ligaments around the ischial tubercle and multiple facet joints,interspinous and supraspinous ligaments.The affected joint is mainly manifested as the annular or linear uneven FDG concentration of joint capsule,joint surface,and joint ligament,especially joint capsule,and part of CT showed rough articular surface,swelling of the joint,and decreased density around the joint.Extraarticular complications were found in 33cases,mainly interstitial lung disease,lymphadenitis and malignancy.The FDG uptake of the involved ligament is positively correlated with the inflammatory markers（CRP,r=0.672,P<0.05;ESR,r=0.500,P<0.05）.There was also a significant correlation between the number of involved lesions and CRP（r=0.518,P<0.05）.There was no significant correlation between the duration of the disease（month）and the FDG metabolism of the involved joint ligaments,and the number of lesions involved（r=-0.164,r=-0.124,P>0.05）.The number of involved joint ligaments and the degree of FDG metabolism in the trunk joint involvement group were significantly higher than those in the non-trunk joint involvement group（t=5.585,P<0.05;t=4.271,P<0.05）.The FDG metabolism and the number of involved joints in active group were significantly more than those in inactive group（P<0.05）Conclusion ¹⁸F-FDG PET/CT can show the systemic involvement of the large proximal joints and trunk joints of RA patients more sensitively,and can also show other organ complications,which is conducive to RA comprehensive assessment and disease activity monitoring.Part Ⅳ Clinical value of ¹⁸F-FDG PET/CT in evaluating rheumatic polymyalgia and dermatomyositisPurpose To investigate the value of ¹⁸F-FDG PET/CT in the diagnosis,differential diagnosis and evaluation of rheumatic polymyalgia（PMR）and dermatomyositis（DM）.Materials and methods The clinical data and ¹⁸F-FDG PET/CT imaging of 10patients with clinical diagnosed PMR were retrospectively analysed,simultaneously another 13 cases of DM were selected as positive control group and 10 cases of physical examination as healthy control group.The extent of involvement,imaging features,SUV_max and complications of the lesions were analyzed.The correlation between the SUV_max of the lesions and CPR,ESR was analyzed in PMR and DM group by Pearson correlation.The correlation between the SUV_max of the lesions and CK,CK-MB was analyzed in DM group by Pearson correlation.Pearson correlation analysis was also performed between the number of complications and the patient’s age,course of disease,and SUV_max of muscle and joint lesions.The SUV_max of the lesion among PMR,DM and HC group were compared using one-way ANOVA analysis.Results All 10 patients with rheumatic polymyalgia showed positive PET/CT imaging.They exhibited a distinctive pattern of abnormal ¹⁸F-FDG uptake around the shoulder and hip joints,in the interspinous bursae,trochanteric regions and adjacent to the ischial tuberosities.Most of them are local,nodular metabolism increased focus.No obvious abnormalities were found in the joint morphology.In 13 cases of dermatomyositis,10 cases were positive in PET/CT imaging,mainly with muscular and skin lesions.The manifestations were diffuse and multiple muscular metabolic heterogeneity,especially in the proximal extremities,with multiple hypermetabolic foci in the skin.Patients with DM had more complications than those with PMR.There was no significant correlation between SUV_max and CRP and ESR（P>0.05）.But there was a significant correlation between SUV_max and CK and the number of complications in patients with DM（P<0.05）.In PMR and DM patients,the metabolism of the joint surrounding tissues and body muscles was significantly higher than that in group HC（P<0.05）,but there was no significant difference between PMR and DM group（P>0.05）.Conclusion ¹⁸F-FDG PET/CT can provide some help for the diagnosis and differential diagnosis in PMR and DM.The FDG uptake of the involved muscles in DM patients can reflect the degree of muscle damage.And it is conducive to the discovery of complications and clinical evaluation of such diseases.