Background:In IgG4-related diseases (IgG4-RD), usefulness of18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) imaging for detecting the organ involvement of IgG4-RD have been shown and,18FDG PET/CT was more accurate and appeared to be more sensitive as compared to other imaging technics1,2. However, until now, the studies regarding about quantitative analysis of PET/CT imaging in IgG4-RD were few. To avoid unnecessary biopsy and select suitable lesion for biopsy on multi-organ involvement disease such as IgG4-RD, the information which lesion is suspected as disease-involvement lesion in a non-invasive test is important.Objectives:The purpose of this work is to evaluate the usefulness of18FDG-PE/CT imaging in management of IgG4-RD using quantitative analysis of PET/CT imaging.Methods:21 patients with IgG4-RD, in whom PET/CT was undertaken at the time of diagnosis between December 2009 and July 2018, were enrolled. We retrospectively investigated the association between histological findings in which biopsy was performed for diagnosis of IgG4-RD and findings of PET/CT.18FDG uptake was assessed in site of major organ involvement of IgG4-RD which could be differentiated from the normal uptake of background tissue with18FDG-PET/CT. For quantitative analysis, we measured the highest standardized uptake value (SUV) of the pixels within the region of interest (ROI) (SUVmax) and the average SUV within ROI (SUVmean). We also measured SUVmeanof liver as reference tissue. Then, we calculated ratio between SUVmeanof ROI and SUVmean/liver.Results:The age at diagnosis was 64.5 ± 11.9 years, serum IgG4 was 743.8 ± 584.1 mg/dl, and biopsy was performed at 24 sites (Submandibular gland 10, prostate gland 4, pancreas 2, thyroid gland 1, lung 1, retroperitoneum 1, kidney 1). Histological findings were consistent with IgG4RD (positive) at 19 sites.Although SUVmaxat the biopsy site was not correlated with the biopsy results, SUVmeanat the biopsy site were significantly higher in the biopsy-positive group (figure 1). As similar, SUVmean/liver SUVmeanwere also higher in the biopsy-positive group (2.17 vs 1.52, respectively P<0.05). To establish cut-off value of SUVmeanto consider biopsy, A receiver operating characteristics (ROC) curve was constructed. ROC curve analysis indicated SUVmean=4.074 as cut-off value which discriminate IgG4-RD related lesion.Conclusion:Our present study suggested that quantitative analysis of18FDG-PET/CT imaging is useful for selecting the biopsy site in IgG4-related disease.Figure 1.XXXXXReferences:[1]Ebbo M, Grados A, Guedj E, et al. Usefulness of 2-[18F]-fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography for staging and evaluation of treatment response in IgG4-related disease: a retrospective multicenter study. Arthritis Care Res (Hoboken) 2014; 66(1): 86-96.[2]Zhang J, Chen H, Ma Y, et al. Characterizing IgG4-related disease with (1)(8)F-FDG PET/CT: a prospective cohort study. Eur J Nucl Med Mol Imaging 2014; 41(8): 1624-34.Disclosure of Interests:None declared
Discontinuation of metformin to prevent metformin-induced high colonic FDG uptake: is 48 h sufficient?