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Objectives: The aim of this study was to develop a deep learning (DL)-based segmentation algorithm for automatic measurement of metabolic parameters of 18F-FDG PET/CT in thymic epithelial tumors (TETs), comparable performance to manual volumes of interest., Patients and Methods: A total of 186 consecutive patients with resectable TETs and preoperative 18F-FDG PET/CT were retrospectively enrolled (145 thymomas, 41 thymic carcinomas). A quasi-3D U-net architecture was trained to resemble ground-truth volumes of interest. Segmentation performance was assessed using the Dice similarity coefficient. Agreements between manual and DL-based automated extraction of SUVmax, metabolic tumor volume (MTV), total lesion glycolysis (TLG), and 63 radiomics features were evaluated via concordance correlation coefficients (CCCs) and linear regression slopes. Diagnostic and prognostic values were compared in terms of area under the receiver operating characteristics curve (AUC) for thymic carcinoma and hazards ratios (HRs) for freedom from recurrence., Results: The mean Dice similarity coefficient was 0.83 ± 0.34. Automatically measured SUVmax (slope, 0.97; CCC, 0.92), MTV (slope, 0.94; CCC, 0.96), and TLG (slope, 0.96; CCC, 0.96) were in good agreement with manual measurements. The mean CCC and slopes were 0.88 ± 0.06 and 0.89 ± 0.05, respectively, for the radiomics parameters. Automatically measured SUVmax, MTV, and TLG showed good diagnostic accuracy for thymic carcinoma (AUCs: SUVmax, 0.95; MTV, 0.85; TLG, 0.87) and significant prognostic value (HRs: SUVmax, 1.31 [95% confidence interval, 1.16-1.48]; MTV, 2.11 [1.09-4.06]; TLG, 1.90 [1.12-3.23]). No significant differences in the AUCs or HRs were found between automatic and manual measurements for any of the metabolic parameters., Conclusions: Our DL-based model provides comparable segmentation performance and metabolic parameter values to manual measurements in TETs., Competing Interests: Conflicts of interest and sources of funding: This work was supported by the National Research Foundation of Korea grant funded by the Korean government (Ministry of Science and ICT; numbers NRF-2020M2D9A1094074 and 2021R1A2C3009056), and by a grant from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute, funded by the Ministry of Health & Welfare, Republic of Korea (HI18C2383). The funders had no role in the conceptualization or design of the study; in the collection, analysis, and interpretation of the data; in the writing of the manuscript; or in the decision to submit the manuscript for publication. The authors declare no competing interests., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: This study investigated diagnostic accuracies of 18F-FDG PET or PET/CT for characterization of histologic type of thymic epithelial tumors (TETs) through a systematic review and meta-analysis., Patients and Methods: The PubMed, Cochrane database, and EMBASE database, from the earliest available date of indexing through August 31, 2020, were searched for studies evaluating diagnostic performance of 18F-FDG PET or PET/CT for characterization of TET. We determined the sensitivities and specificities, calculated positive and negative likelihood ratios (LR+ and LR-), and constructed summary receiver operating characteristic curves., Results: The pooled sensitivity of 18F-FDG PET or PET/CT was 0.89 (95% confidence interval [CI], 0.80-0.95), and the pooled specificity was 0.77 (95% CI, 0.63-0.87) for differentiation between thymic cancer and thymoma. Likelihood ratio syntheses gave an overall positive likelihood ratio (LR+) of 3.9 and negative likelihood ratio (LR-) of 0.14. The pooled diagnostic odds ratio was 28 (95% CI, 13-63). The pooled sensitivity was 0.90 (95% CI, 0.75-0.96), and the pooled specificity was 0.81 (95% CI, 0.68-0.89) for differential diagnosis of a low-risk or high-risk TET. LR+ was 4.7 and LR- was 0.12. The pooled diagnostic odds ratio was 38 (95% CI, 12-121). In meta-regression analysis, no variable was the source of the study heterogeneity., Conclusions: 18F-FDG PET or PET/CT has excellent diagnostic performances for characterization of TET. Further large multicenter studies would be necessary to establish the diagnostic accuracy of 18F-FDG PET or PET/CT for differentiation of histologic type of TET., Competing Interests: Conflicts of interest and sources of funding: none declared., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Mixed epithelial and stromal tumor of the kidney (MESTK) is a rare renal tumor composed of solid and cystic components. Mixed epithelial and stromal tumor of the kidney has no pathognomonic imaging feature. It is difficult to distinguish MESTK from other cystic renal neoplasms using current radiological methods. We report a rare case of MESTK that was diagnosed in a 46-year-old woman with breast cancer. F-FDG PET/CT and contrast-enhanced CT features of MESTK are presented, which could potentially provide useful information in the differential diagnoses of cystic renal neoplasms.

A 59-year-old woman with back pain underwent an F-NaF PET/CT bone scan. Unexpectedly, multiple foci of increased tracer uptake were present in the abdomen and pelvis, which corresponded to the calcified soft tissue masses. The subsequent F-FDG PET/CT not only confirmed increased FDG activity in these partially calcified mass but also revealed abnormal activity in noncalcified lesions. The pathological examination demonstrated that the patient had ovarian cancer.

Endometriosis is a common gynecologic condition of the premenopausal years. However, postmenopausal endometriosis is rare (2.2%) and thought to be related to high level of circulating estrogen, especially in hormonal replacement therapy. We present a case of a 69-year-old postmenopausal woman, previously healthy and on no regular medication, with diffuse peritoneal endometriosis and bilateral ovarian endometrioma mimicking metastatic ovarian carcinoma on FDG PET/CT. Both ovarian endometrioma had low-grade activity, but more strikingly, there was diffuse FDG-avid peritoneal dissemination and gross ascites. Endometriosis should not be totally disregarded as a differential diagnosis even at postmenopausal status.

Purpose: The aim of this study was to investigate the value of morphologic, functional, and metabolic biomarkers acquired concurrently at PET/MRI in patients with thymic epithelial tumors., Patients and Methods: During 1 year, 9 patients with suspected thymic epithelial tumors at contrast-enhanced chest CT were prospectively enrolled and underwent preoperative 18F-FDG PET/MRI. Two chest radiologists prospectively reviewed the CT and MRI scans of PET/MRI in consensus, and 2 nuclear physicians reviewed the PET images. Visual assessment of the tumor morphology, functional biomarkers such as apparent diffusion coefficient from diffusion-weighted images, and metabolic biomarkers (including SUVmax, metabolic tumor volume, total lesion glycolysis, and heterogeneity index) were recorded. All patients underwent operation, and their pathologic reports served as the reference standard., Results: Thymic epithelial tumors were demonstrated in all 9 patients at pathologic examination. Tumor contour (P = 0.012) and shape (P = 0.033) had an association with the World Health Organization subtype, and the presence of septum (P = 0.048) on MRI scans had an association with the Masaoka stage. In terms of functional and metabolic biomarkers, SUVmax (ρ = 0.683, P = 0.042) and SUV/apparent diffusion coefficient (ρ = 0.703, P = 0.035) correlated with the Masaoka stage. Metabolic tumor volume (P = 0.024), heterogeneity index (P = 0.024), and total lesion glycolysis (P = 0.048) were useful for classification between low- and high-risk thymic epithelial tumors., Conclusions: Although limited by the small number of patients enrolled, morphologic, functional, and metabolic biomarkers derived from PET/MRI scans were useful for the stratification of thymic epithelial tumors.

Purpose: The aim of this study was to determine an optimal threshold method for the segmentation of malignant lesions from (18)F-FDG PET/CT images and to evaluate the prognostic value of the total lesion glycolysis in post-surgical patients with epithelial ovarian cancer., Methods: We retrospectively reviewed 47 patients with pathologically proven epithelial ovarian cancer who underwent (18)F-FDG PET/CT imaging after surgery. The follow-up time was 26.6 ± 19.8 months (ranged from 4 to 89 months). For each patient, every lesion was segmented by 2 thresholds with 3D-area growing algorithm, standard uptake value (SUV) 2.5, and background method. The detection rates were compared. The optimal threshold method was then used to calculate whole-body metabolic tumor volume (WBMTV) and whole-body total lesion glycolysis (WBTLG). The prognostic significance of SUV(max), WBMTV, WBTLG, and other pathological variables for overall survival were assessed by Cox proportional hazards regression analysis and Kaplan-Meier survival analysis., Results: A total of 142 metastatic lesions of 47 patients were confirmed by long-term clinical follow-up or pathological findings. The detection rates of the threshold SUV 2.5 and background methods were 37.32% (53/142) and 96.48% (137/142), respectively, which showed significant difference between the 2 methods (P < 0.005). In multivariate analysis, WBTLG, obtained from the background method, was an independent predictive factor associated with the prognosis (HR 1.043, 95% CI 1.01-1.078, P = 0.011), and none of the other factors had statistical association. Survival analysis also showed that the survival time was clearly shortened with WBTLG increasing (P < 0.001)., Conclusions: In this group of post-surgery patients with epithelial ovarian cancer, the background method could segment much more malignant lesions than SUV = 2.5 method, and WBTLG, obtained from this method, could be used as an independent prognostic factor.

Purpose: This study aimed to test the role of combined imaging with 18F-FDG-PET/CT and 111In-octreotide SPECT in characterizing thymic epithelial tumors (TETs)., Methods: We evaluated 20 patients with newly diagnosed TETs who had undergone concomitant 18F-FDG-PET/CT and 111In-octreotide SPECT. Thymic epithelial tumors were classified by World Health Organization (WHO) as low-risk thymomas (5), high-risk thymomas (4), and thymic carcinomas (11, among which 6 neuroendocrine tumors). Patients were staged according to Masaoka system. 18F-FDG-PET/CT was performed and SUV(max) of primary tumors was recorded. 111In-octreotide SPECT of the thorax was performed, and tumor-to-background ratio was determined on the 24-hour coronal sections., Results: All patients showed increased 18F-FDG uptake in mediastinal lesions. SUV(max) were significantly correlated with WHO classification (r = 0.66, P < 0.01) and with Masaoka stage (r = 0.60, P < 0.01). SUV(max) of low-risk thymomas (mean [SD], 2.87 [0.83]) were significantly lower than those of high-risk thymomas (mean [SD], 7.21 [1.73], P < 0.01) and of thymic carcinomas (mean [SD], 9.39 [5.80], P < 0.05), whereas no significant difference was found between high-risk thymomas and thymic carcinomas. SUV(max) of all high-risk thymomas and thymic carcinomas was 4.5 or greater. All primary tumors were detected by In-octreotide SPECT, and tumor-to-background ratios ranged between 1.67 and 10.10. No statistically significant correlation was found between tumor-to-background ratios and WHO classification (r = 0.24, P = 0.36) and Masaoka stages (r = 0.31, P = 0.23). However tumor-to-background ratios of thymic neuroendocrine tumors (mean [SD], 5.71 [3.09]) were significantly higher than those of all other TETs with SUV(max) of 4.5 or greater (mean [SD], 2.41 [0.56]; P < 0.05)., Conclusions: 18F-FDG-PET/CT scan allows to differentiate high-risk epithelial tumors and thymic carcinomas from low-risk thymomas, whereas 111In-octreotide SPECT may identify neuroendocrine tumors among those showing high 18F-FDG uptake.

Objective: This study aimed to evaluate the efficiency of 18F-FDG PET/CT in suspected recurrence of epithelial ovarian cancer, after treatment, comparing outcomes of PET/CT with histological tumor subtype, CA-125 serum levels, and findings of conventional diagnostic imaging modalities (CI)., Methods: Data from 121 women who underwent FDG PET/CT for suspected recurrence of epithelial ovarian cancer after treatment were reviewed retrospectively., Results: Of all patients, 80% had recurrent disease and 20% were disease-free on the final clinical diagnosis. PET/CT showed true-positive findings in 82% of patients, whereas CI demonstrated true-positives in 70% of cases. At the time of PET/CT scanning, only 55 patients had serum CA-125 level greater than 35 U/mL, whereas 52 patients presented with CA-125 levels in a reference range. PET/CT sensitivity (82%) was significantly higher than that of CA-125 (59%), whereas difference in sensitivity between PET/CT and CI (69%) was limited. PET/CT specificity (87%) was significantly better than that of CI (47%), although no difference in specificity between PET/CT and CA-125 (80%) was found. However, no difference in CA-125 serum levels between patients with local tumor relapse and those with distant metastases was found. PET/CT showed the highest positive predictive value (96%) and negative predictive value (55%) when compared with other modalities. In high-grade tumors (n = 66), PET/CT accuracy was 80%, better than that of serum CA-125 (64%) and that of CI (62%). Equally in low-grade ovarian carcinomas (n = 55), PET/CT accuracy (87%) was significantly higher than that of the tumor marker (60%) and also higher than that of CI (70%)., Conclusions: FDG PET/CT was proven to be more efficient than serum CA-125 assay and CI in detecting recurrences of ovarian cancer after treatment. The sensitivity of FDG PET/CT is not influenced by tumor histology. FDG PET/CT should be considered a useful diagnostic tool in the surveillance of patients that received treatment for epithelial ovarian carcinoma.