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A number of researchers in Korea have tried to set-up the production of radionuclides and develop new radiopharmaceuticals for several decades. Thanks to their 60-year endeavor to advance the field of radiopharmaceutical sciences, now we have a lot of research units and facilities in Korea. Still, there are huge number of issues to be solved in radiopharmaceutical sciences; however, our efforts will be continued to develop new radiopharmaceuticals and to apply the new radiopharmaceuticals into nuclear medicine field., Competing Interests: Conflict of InterestRan Ji Yoo, Yun-Sang Lee, Kyo Chu Lee, Dong Wook Kim, Dong-Yeon Kim, Yearn Seong Choe, and Jae Min Jeong declare no conflict of interests., (© The Author(s), under exclusive licence to Korean Society of Nuclear Medicine 2022.)

Purpose: We developed predictive models using different programming languages and different computing platforms for machine learning (ML) and deep learning (DL) that classify clinical diagnoses in patients with epiphora. We evaluated the diagnostic performance of these models., Methods: Between January 2016 and September 2017, 250 patients with epiphora who underwent dacryocystography (DCG) and lacrimal scintigraphy (LS) were included in the study. We developed five different predictive models using ML tools, Python-based TensorFlow, R, and Microsoft Azure Machine Learning Studio (MAMLS). A total of 27 clinical characteristics and parameters including variables related to epiphora (VE) and variables related to dacryocystography (VDCG) were used as input data. Apart from this, we developed two predictive convolutional neural network (CNN) models for diagnosing LS images. We conducted this study using supervised learning., Results: Among 500 eyes of 250 patients, 59 eyes had anatomical obstruction, 338 eyes had functional obstruction, and the remaining 103 eyes were normal. For the data set that excluded VE and VDCG, the test accuracies in Python-based TensorFlow, R, multiclass logistic regression in MAMLS, multiclass neural network in MAMLS, and nuclear medicine physician were 81.70%, 80.60%, 81.70%, 73.10%, and 80.60%, respectively. The test accuracies of CNN models in three-class classification diagnosis and binary classification diagnosis were 72.00% and 77.42%, respectively., Conclusions: ML-based predictive models using different programming languages and different computing platforms were useful for classifying clinical diagnoses in patients with epiphora and were similar to a clinician's diagnostic ability., Competing Interests: Yong-Jin Park, Ji Hoon Bae, Mu Heon Shin, Seung Hyup Hyun, Young Seok Cho, Yearn Seong Choe, Joon Young Choi, Kyung-Han Lee, Byung-Tae Kim, and Seung Hwan Moon declare that they have no conflict of interest.All procedures performed in studies involving human participants were in accordance with the ethical standards of our institutional review board and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.The institutional review board of our institute approved this retrospective study, and the requirement to obtain informed consent was waived.

Purpose: We investigated the incidence, location, and clinical significance of focal 18 F-FDG uptake of the spinal cord in patients with cancer., Methods: We reviewed the medical records of 22,937 consecutive adult patients with known or suspicious malignancy who underwent 18 F-FDG PET/CT. PET/CT scans with incidental focal spinal cord uptake were selected and retrospectively reviewed to determine the presence, location, number, and maximum standardized uptake value (SUV max ) of any focal hypermetabolic lesions of the spinal cord. In subjects with focal spinal uptake, clinical characteristics and clinical follow-up results, including follow-up PET/CT, were reviewed., Results: Incidental focal spinal cord uptake was observed in 69 of 22,937 adult patients (incidence = 0.3%; M:F = 31:38; age, 55.8 ± 14.7 years). Seventy-eight focal hypermetabolic lesions on spinal cord in the PET/CT scans of the 69 study subjects were analyzed. The most common sites of focal spinal cord uptake were the T12 vertebra (47/78; 60.3%) and L1 vertebra (20/78; 25.6%). Multifocal cord uptake was found in 8 of 69 patients (11.6%). The average SUV max for cord uptake was 2.5 ± 0.5 (range, 1.4∼3.9). There was no clinical or imaging evidence of abnormalities in the spinal cord, both at the time of PET/CT and during clinical follow-up., Conclusions: Although incidental focal 18 F-FDG uptake of the spinal cord is rare in patients with cancer, it may be physiological or benign, but it should not be considered as malignant involvement. Common sites for the uptake were in the T12 and L1 spine levels.

Purpose: 18 F-fluorodeoxyglucose (FDG) PET/CT is useful for staging and evaluating treatment response in patients with diffuse large B-cell lymphoma (DLBCL). A five-point scale model using the mediastinal blood pool (MBP) and liver as references is a recommended method for interpreting treatment response. We evaluated the variability in standardized uptake values (SUVs) of the MBP, liver, and myocardium during chemotherapy in patients with DLBCL., Methods: We analyzed 60 patients with DLBCL who received rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP) treatment and underwent baseline, interim, and final FDG PET/CT scans. The FDG uptakes of lymphoma lesions, MBP, liver, and myocardium were assessed, and changes in the MBP and liver SUV and possible associated factors were evaluated., Results: The SUV of the liver did not change significantly during the chemotherapy. However, the SUV mean of MBP showed a significant change though the difference was small (p = 0.019). SUV mean of MBP and liver at baseline and interim scans was significantly lower in patients with advanced Ann Arbor stage on diagnosis. The SUV mean of the MBP and liver was negatively correlated with the volumetric index of lymphoma lesions in baseline scans (r = -0.547, p < 0.001; r = -0.502, p < 0.001). Positive myocardial FDG uptake was more frequently observed in interim and final scans than in the baseline scan, but there was no significant association between the MBP and liver uptake and myocardial uptake., Conclusions: The SUV of the liver was not significantly changed during R-CHOP chemotherapy in patients with DLBCL, whereas the MBP SUV of the interim scan decreased slightly. However, the SUV of the reference organs may be affected by tumor burden, and this should be considered when assessing follow-up scans. Although myocardial FDG uptake was more frequently observed after R-CHOP chemotherapy, it did not affect the SUV of the MBP and liver., Competing Interests: Soo Jeong Kim, Hyun Kyung Yi, Chae Hong Lim, Young Seok Cho, Joon Young Choi, Yearn Seong Choe, Kyung-Han Lee, Byung-Tae Kim, and Seung-Hwan Moon declare that they have no conflicts of interest. Ethical Statement Our study was performed in compliance with the regulations of our institution and generally accepted guidelines governing such work. Each author participated sufficiently in the work to take responsibility for the content. We confirm that this manuscript is original, is not under simultaneous consideration by another journal, and has not been previously published. There are no financial associations that might cause a conflict of interest.

The incidence of Alzheimer's disease (AD), a progressive neurodegenerative disorder, continues to soar with the rapid growth of the elderly population, thus creating an enormous social and economic burden. Although disease-modifying drugs to treat AD are not yet available, several candidate drugs are in clinical trials. Most of these drugs are expected to be effective at the early stages of the disease, and therefore the early and accurate diagnosis of AD will be a critical factor in efforts to improve the prognosis of patients with AD. This review focuses on lead radioligands developed to date and their preclinical data in order to facilitate the development of tau-specific positron emission tomography radioligands that are of great interest to the scientific community.

Purpose: We investigated the prognostic values of volume-based metabolic parameters by (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET)/computed tomography (CT) in gallbladder carcinoma patients and compared them with other prognostic parameters., Materials and Methods: We enrolled 44 patients, who were initially diagnosed with gallbladder carcinoma and undergoing (18)F-FDG PET/CT. Various metabolic volume-based PET parameters of primary tumors, including maximum and average standardized uptake values (SUVmax, SUVavg), metabolic tumor volume (MTV), and total lesion glycolysis (TLG), were measured in gallbladder carcinoma patients using mediastinal blood pool activity as a threshold SUV for determining the tumor boundaries. Overall survival analysis was performed using the Kaplan-Meier method with PET parameters and other clinical variables. For determining independent prognostic factors, Cox proportional hazards regression analysis was performed., Results: Of the 44 enrolled patients, cancer- or treatment-related death occurred in 30 (68.2 %). The mean clinical follow-up period was 22.2 ± 10.4 m (range, 0.6-35.9 m). Univariate analysis demonstrated that clinical or pathologic TNM stage (P < 0.001), treatment modality (P < 0.001), MTV (cutoff = 135 cm(3), P = 0.001), and TLG (cutoff = 7,090, P < 0.05) were significant prognostic factors. In multivariate analysis, both clinical or pathologic TNM stage [hazard ratio (HR) = 2.019 (I vs II), 21.287 (I vs III), and 24.354 (I vs IV); P = 0.001) and TLG (HR = 2.930; P < 0.05) were independent prognostic factors for predicting overall survival., Conclusions: In gallbladder cancer, TLG of the primary tumor, a volume-based metabolic parameter, is a significant independent prognostic factor for overall survival in conjunction with the clinical or pathological TNM stage.

Purpose: We investigated PET/CT diagnostic criteria for differentiating benign from malignant parotid lesions with focal (18)F-FDG uptake., Methods: The subjects of the study were 272 patients who exhibited focal (18)F-FDG uptake of the parotid gland. Sixty-eight pathologically confirmed parotid lesions from 67 patients were included. The maximum SUV (SUVmax), uptake patterns (homogeneous vs. heterogeneous), size measured by CT, maximum Hounsfield units (HUmax) and margins on CT (well vs. ill defined) of each parotid lesion on PET/CT images were compared with final diagnoses., Results: Thirty-two parotid lesions were histologically proven to be malignant. There were significant differences in uptake patterns (cancer incidence, heterogeneous:homogeneous = 79.2%:29.5%, p < 0.0001) and margins on CT (cancer incidence, ill:well defined = 84.4%:13.3%, p < 0.0001) between benign and malignant lesions. The cancer risks of parotid lesions were 89.5% with heterogeneous uptake and ill-defined margins, 70.6% with heterogeneous uptake or ill-defined margins (no overlap in subjects) and 9.3% with homogeneous uptake and well-defined margins (p < 0.0001). When any lesion with heterogeneous uptake or ill-defined margins was regarded as malignant, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 90.6% (29/32), 80.6% (29/36), 80.6% (29/36), 90.6% (29/32) and 85.6% (58/68), respectively. For predicting malignancy, combined PET/CT criteria showed better sensitivity, NPV and accuracy than PET-only criteria, and had a tendency to have more accurate results than CT-only criteria. There were no significant differences in SUVmax, size or HUmax between benign and malignant lesions., Conclusion: Uptake patterns and margins on CT are useful PET/CT diagnostic criteria for differentiating benign from malignant lesions.