¹⁸F-FDG-PET-CT Uptake And Interstitial Lung Disease In Dermatomyositis:A Single Center Retrospective Study

BackgroundInterstitial lung disease?ILD?is a common manifestation of dermatomyositis?DM?.The mortality is high and prognosis is poor,but the current DM-ILD assessment method is limited.The most widely used HRCT is a morphological assessment,which is subjective because of evaluator heterogeneity.So it is urgent to find objective and feasible methods to help assess the disease activity and help predict the prognosis.PET-CT combines imaging and metabolic functional characteristics to reflect overall disease distribution and cellular metabolic activity.Many studies have focused on the relationship between PET-CT-¹⁸F-FDG and idiopathic pulmonary interstitial fibrosis,and the related research to date still lacks in DM-ILD.ObjectivesTo investigate the clinical value of PET-CT-¹⁸F-FDG uptake in DM-ILD assessment and classification.Materials and methodsRetrospectively included 37 patients with DM-ILD who underwent PET-CT examination in our hospital.To collect:1,baseline data;2,inflammation index;3,KL-6;4,pulmonary function test;5,HRCT performance score;6,HRCT-based pathologicalclassification;7,HRCT-basedperformanceclassification;8,immunological typing;9,SUVmax,SUVmean and Volume for PET-CT region of interest.To depict serological,imaging,pulmonary function,KL-6,PET-CT of DM-ILD.To analyze whether abnormal clinical indicators differ in the uptake of ¹⁸F-FDG.To analyze correlation between PET-CT-¹⁸F-FDG uptake and HRCT as well as other clinical values;To study differences of PET-CT-¹⁸F-FDG uptake between different disease subtypes?immunological type,pathological type,HRCT type?;To explore the diagnostic value of PET-CT-¹⁸F-FDG uptake in different disease subtypes by making ROC curves.ResultsThrity-seven DM-ILD patients?57.65±12.65 years old,male/female:14/23 cases?were included.Baseline erythrocyte sedimentation rate was 27.36±18.35mm/h,CRP was 10.72±15.18mg/l,KL-6 was 803.3±743.8 U/ml;86.67%patients had a decrease in PaO₂,1/3 has a decrease in SaO₂;dysfunction in lung diffusion was presented in89.5%patients,dysfunction in restrictive ventilation was presented in 47.4%patients;SUVmax in the region of interest was 3.002±1.344,SUVmean was 2.509±0.6940,and volume was 0.3211±0.5948.Based on charateristic HRCT findings,the most common histological types were NSIP and OP.HRCT honcycombing was not observed.95%patients had ground-glass opacity,62%had grid changes,and 60%had consolidation.The ¹⁸F-FDG uptake parameters of PET-CT have significantly changed when clinical indicators are abnormal:SUVmax was significantly elevated in the CRP abnormal group and PaO₂ abnormal group?P=0.0273,P=0.0249,respectively?;SUVmean was significantly increased in the PaO₂ abnormal group and KL-6abnormal group?P=0.0444,P=0.0043,respectively?;Volume was significantly increased in the CRP abnormal group?P=0.0215?.In terms of erythrocyte sedimentation rate,oxygen saturation,and lung function index,there was no significant difference of ¹⁸F-FDG between the normal and abnormal groups?P>0.05?.The ¹⁸F-FDG uptake parameters of PET-CT were correlated with clinical indicators:SUVmean was positively correlated with KL-6?r=0.418,P=0.0471?,negatively with oxygen partial pressure?r=-0.574,P=0.028?,and positively with the degree of consolidation in HRCT?r=0.4721,P=0.0032?.SUVmax was also positively correlated with the degree of consolidation in HRCT?r=0.5329,P=0.0007?.There was no significant correlation between the uptake parameters of ¹⁸F-FDG and inflammation,lung function,HRCT grinding and grid structure?P>0.05?.As for differences of PET-CT-¹⁸F-FDG uptake in disease subtypes,HRCT consolidation type was significantly different from the GGO type in SUVmax?P=0.012?,SUVmean?P=0.014?,and Volume?P=0.022?.The difference was also significant when compared HRCT consolidation type with the HRCT hybrid type of ground glass and grid structure in SUVmax?P=0.006?,SUVmean?P=0.024?,and Volume?P=0.024?.Compared with NSIP,OP had higher SUVmax?P=0.008?,SUVmean?P=0.006?and Volume?P=0.05?;compared with UIP,OP had higher SUVmax?P=0.014?and SUVmean?P=0.026?;no statistical difference in the immunological types?ARS positive vs ARS negative?of ¹⁸F-FDG uptake.When the optimal SUVmax cutoff value is 3.03 for the diagnosis of OP,the sensitivity was 71.43%,the specificity was 78.26%,and the area under the curve is0.773.When the optimal SUVmean cutoff value of OP was 2.855,the sensitivity was50%and the specificity was 91.3.%,the area under the curve was 0.739;when the optimum cutoff value of the volume was 0.415,the sensitivity of the diagnostic OP was 50%,the specificity was 91.3%,and the area under the curve was 0.730.ConclusionThe SUVmax and SUVmean of PET-CT are related to the clinical indicators of DM-ILD patients;the uptake value of ¹⁸F-FDG can help determine the DM-ILD subtype.