Study Of ¹⁸F-FDG PET/CT?PET/MR Multimodality Imaging Application Value In Polymyositis-dermatomyositis

Objectives:In recent years,the value of imaging in polymyositis and dermatomyositis has gradually gained attention.MRI scans have been incorporated into the new diagnostic criteria for inflammatory myopathy.¹⁸F-FDG PET/CT examination has also shown preliminary effectiveness in the application of polymyositis-dermatomyositis,but a large sample of systematic research is still lacking,especially the comparative study of PET and MR at the muscle level.This study systematically reviewed the ¹⁸F-FDG PET.CT and PET/MR imaging and clinical data of patients with polymyositis-dermatomyositis in our hospital,and analyzed the distribution characteristics of myositis lesions on ¹⁸F-FDG PET/CT images.The clinical significance of different PET image expression modes of myositis,the relationship between myositis activity and associated tumors and interstitial lung disease,comparison and observation of the characteristics of the same machine fusion PET and MR myositis image changes,and trying to establish a new simple and easy PET The semi-quantitative evaluation index of myositis activity provides scientific basis and research basis for the application of ¹⁸F-FDG PET/CT and PET/MR in polymyositis-dermatomyositis.Methods:1.Imaging data and related clinical data of patients who were diagnosed with polymyositis or dermatomyositis in our hospital from 2010 to 2020 with ¹⁸F-FDG PET/CT examination wear collected and analyzed retrospectively.In addition,the same number of non-myopathic patients with age and gender matching the patient group at the same period were selected as imaging controls.They underwent ¹⁸F-FDG PET/CT for physical examination,or tumor screening because ofincreased tumor markers,or for lung nodules without apparent abnormal FDG uptake.2.The whole body muscles within the conventional PET scanning areaare divided into 14 muscle groups on both sides of 7parts including upper arm,shoulder,neck,chest,waist,hip and thigh.ROI technology of the AW image processing workstation is used to obtain the maximum standard uptake ratio(SUVmax-mus)of each muscle group,and the SUVmax(SUVmax-liv)of the liver and the SUVmax(SUVmax-blo)of the mediastinal blood pool are measured simultaneously.The maximum standard uptake ratio of each muscle group(SUVmax-mus)is divided by the maximum standard uptake ratio(SUVmax-liv)of the liver to obtain the normalized muscle group uptake ratio(SUVmax-mus/SUVmax-liv).3.Take the average of the muscle group uptake ratio of the 14 muscle groups around the body to obtain the average normalized maximum uptake ratio of the muscle group(mean-SUVmax-mus/SUVmax-liv)as a new quantification to evaluate the activity of polymyositis-dermatomyositis index.Correlation analysis was performed with muscle enzyme,a conventional indicator of clinical response myositis activity,to evaluate its efficacy.4.Based on the visual method,the radioactive distribution intensity of each muscle group in the patient group was compared with the mediastinal blood pool and liver radioactive distribution intensity.At the same time,visual observation was performed to determine whether the increase in the radioactive distribution of each muscle group was affected by more than half of the muscle group.Scores are assigned to each muscle group based on the above two factors.Adding the scores of all muscle groups to obtain the muscle FDG metabolic level evaluation total score(T-Score)as a new semi-quantitative index to evaluate the activity of polymyositis-dermatomyositis.Correlation analysis was also performed with muscle enzymes,a conventional indicator of clinical response myositis activity,to evaluate its efficacy.5.Differential analysis of paired data of SUVmax values of bilateral muscle groups at the same site on the PET images of the patient group was performed to evaluate the distribution of lesions shown on patients with polymyositis-dermatomyositis on ¹⁸F-FDG PET/CT symmetry.6.The standardized SUVmax-mus/SUVmax-liv ratio of the patient group and the control group were compared and analyzed to evaluate the affected muscle group sites during myositis.The normalized SUVmax-mus/SUVmax-liv ratio of each muscle group in the patient group is subtracted from the average SUVmax-mus/SUVmax-liv ratio of the corresponding muscle group in the control group to obtain the normalized SUVmax value of the patient group relative to the control group.The increase is recorded as the value of?SUVmax.The differences in?SUVmax between the upper arm,shoulder,neck,chest,waist,hips and thighs of the patient group were compared and analyzed in order to evaluate the severely affected sites during myositis.7.The differences in CK,mean-SUVmax-mus/SUVmax-liv,and T-Score between the treatment group and the non-treatment group were compared to evaluate the effect of treatment on PET to determine myositis activity.8.The differences of CK,mean-SUVmax-mus/SUVmax-liv and T-Score between tumor group and non-tumor group were compared to evaluate the relationship between tumor associated probability and myositis activity.To exclude the effects of treatment,the differences in CK,mean-SUVmax-mus/SUVmax-liv,and T-Score between the tumor group and the non-tumor group before treatment were also compared.9.Patients were divided into a diffuse lesion group and a focal lesion group based on the ¹⁸F-FDG PET/CT imaging images of patients with polymyositis-dermatomyositis.The differences of related indicators between the two groups were compared to evaluate the relationship between the different types of disease distribution and the myositis activity,associated malignant tumors,treatment and clinical diagnosis.10.The patients were divided into two groups according to whether they had interstitial pneumonia,and the differences in myositis activity and tumor-associated rate between the two groups were analyzed and compared.11.The SUVmax difference of lung lesions between fast-progressive interstitial pneumonia group and non-fast-progressive interstitial pneumonia group was compared,and the predictive value of lung tissue SUVmax value for the prognosis of lung lesions was evaluated.12.A total of 5 patients with confirmed dermatomyositis underwent PET/MR scans of the proximal thigh.A total of 110 muscles from 11 muscles per leg were included in the analysis.Under the premise of precise positioning of PET and MR image fusion on the same machine,the individual muscles'involvement was determined.Kappa consistency test was used to evaluate the consistency of 110 muscle changes on PET and MR images.13.Correlation analysis was performed between the SUVmax of each muscle and the T2mean(T2mean)and T2max(T2max)measured on the T2mapping sequence to evaluate the difference between PET and MR in the distribution and activity of myositis lesions.14.A preliminary analysis of specific manifestations of lesions with inconsistent PET and MR findings was performed.15.Statistical analysis was performed using SPSS 20.0 software.Measurement data were compared between two groups using t test or Wilcoxon rank sum test;Kruskal-Wallis test was used to compare non-parametric multiple groups;Spearman rank correlation analysis was used to correlate non-normally distributed count data;Kappa was used to agree The consistency test was performed on the involvement of lesions on PET and MR images.All tests were two-way tests.The statistical test level was?=0.05,and the significance level was P<0.05.Results:1.A total of 58 patients met the criteria and were included in the study,including24 males and 34 females.The age range was 20-79 years,and the average age was52.34±14.07 years.Clinical diagnosis of polymyositis was found in 16 cases and dermatomyositis in 42 cases.Among the 58 patients in the control group,24 were male and 34 were female.The age range was 21-80,and the average age was 54.26±12.25years.Among them,there were 27 physical examination patients,13 patients with negative tumor screening results due to increased tumor markers,and 18 patients with pulmonary nodules whose FDG metabolism level was not significantly increased.2.The new quantitative(mean-SUVmax-mus/SUVmax-liv)and semi-quantitative(T-Score)indicators based on PET scan imaging changes for assessment of myositis activity are positively correlated with clinical muscle enzymes.And the correlation between T-Score and muscle enzyme is better than mean-SUVmax-mus/SUVmax-liv.3.The normalized SUVmax values of all muscle groups in the patient group were significantly higher than those in the control group;the?SUVmax values of the hips and shoulders were higher than those of other parts.4.Muscle enzyme(CK),mean-SUVmax-mus/SUVmax-liv,and T-Score were lower in the treatment group than in the non-treatment group,and the differences were significant.5.There were no significant differences in CK,mean-SUVmax-mus/SUVmax-liv,and T-Score between the tumor group and the non-tumor group,and between the tumor group and the non-tumor group before treatment.6.The index of myositis activity in the diffuse lesion group is higher than that in the focal lesion group,and the difference is significant;there is no significant difference in the tumor incidence rate between the diffuse lesion group and the focal lesion group;the proportion of patients after treatment in the focal lesion group Compared with the diffuse lesion group,the difference was significant;the rate of patients diagnosed with myositis in the diffuse lesion group was higher than that of the focal lesion group,and the difference was significant.7.There was no significant difference in myositis activity and tumor-associated rate between the patients with and without interstitial pneumonia.8.The SUVmax value of the affected lung tissues in the fast-progressive interstitial lung disease group was significantly higher than that in the non-fast-progressive interstitial lung disease group,and the difference was significant.9.Using the muscle as the evaluation unit,the Kappa consistency test of PET and MR image performance during myositis showed that the two have good consistency,with a Kappa coefficient of 0.747,P<0.001.10.There is a good correlation between the SUVmax value of the PET quantitative index and the T2 mean(T2mean)and T2 maximum(T2max)of the MR quantitative index of each muscle,P<0.01.11.A total of 13 muscles have differences.The 5 muscles have high PET metabolism,but the T2 high signal in the MR image is not obvious;the 2muscles MR image have a significant change in T2 high signal but the PET metabolism is not significantly increased;both have positive changes but There are 6 obvious differences in the location and range of the distribution.The main manifestation is that MR shows a significant signal of edema in the myometrium and fascia,but PET shows that the muscle itself is mainly metabolized.Conclusions:1.The new quantitative(mean-SUVmax-mus/SUVmax-liv)and semi-quantitative(T-Score)indicators for evaluation of myositis activity based on changes in PET scan imagingcan be used for the evaluation of clinical myositis activity.In particular,the semi-quantitative indicator T-Score based on visual evaluation does not need to rely on the cumbersome multi-site SUVmax measurement of image processing workstations,and has better correlation with muscle enzymes,which can provide a more convenient method for clinical evaluation of myositis activity.2.In myositis,all muscle groups showed an increase in SUVmax value,suggesting all muscles can be affected during myositis.Hip and shoulder involvement is higher than other parts.3.Treatment will reduce the value of various indicators of PET for evaluation of myositis activity,so the effects of treatment factors need to be considered in PET evaluation of myositis activity.4.The incidence of tumors in patients with polymyositis-dermatomyositis is not related to myositis activity.5.The index of myositis activity in the diffuse lesion group is higher than that in the focal lesion group,suggesting that the diffuse lesion group is usually heavier than those with focal distribution;the probability of tumor concomitantness is independent of the type of myositis lesion distribution on PET images;focal lesions The proportion of patients in the group after treatment was higher than that in the diffuse lesion group,suggesting that treatment may cause the distribution of myositis lesions to change from diffuse to focal;patients with myositis are more inclined to diffuse lesions than those with dermatomyositis.Sexual lesions are more common in patients with dermatomyositis.6.The presence of interstitial pneumonia has nothing to do with the severity of myositis and the incidence of tumors.7.Patients with polymyositis and dermatomyositis combined with interstitial lung disease with a higher SUVmax value of lung lesions have a poor prognosis,and need to be actively treated with intervention therapy to avoid respiratory failure.8.The analysis of PET and MR for the first time on the basis of accurate positioning of PET and MR images obtained by PET/MR scanning on the same machine,shows that PET and MR have good consistency in showing the extent and degree of muscle involvement in patients with dermatomyositis.9.There is a good correlation between the quantitative index of PET SUVmax and the quantitative index of MR T2mapping sequence T2mean and T2max.It also shows that PET and MR have the same results in the distribution of myositis lesions and evaluation of inflammatory activity in most locations.10.PET and MR inconsistency can be manifested as high PET metabolism and no increase in MR signal,or it can be manifested as a significant increase in MR signal without significant increase in PET metabolism.The difference in the distribution of PET and MR is mainly manifested by the obvious edema and high-signal signals in sarcolemma and fascia,but PET shows increased muscle metabolism.This may be related to the different PET and MR imaging mechanisms and the main stage of myositis in different pathological changes.