PURPOSE: The utility of 18-fluordesoxyglucose positron emission tomography ([¹⁸F]-FDG-PET) combined with computer tomography or magnetic resonance imaging (MRI) in gastric cancer remains controversial and a rationale for patient selection is desired. This study aims to establish a preclinical patient-derived xenograft (PDX) based [¹⁸F]-FDG-PET/MRI protocol for gastric cancer and compare different PDX models regarding tumor growth and FDG uptake. MATERIALS AND METHODS: Female BALB/c nuu mice were implanted orthotopically and subcutaneously with gastric cancer PDX. [¹⁸F]-FDG-PET/MRI scanning protocol evaluation included different tumor sizes, FDG doses, scanning intervals, and organ-specific uptake. FDG avidity of similar PDX cases were compared between ortho- and heterotopic tumor implantation methods. Microscopic and immunohistochemical investigations were performed to confirm tumor growth and correlate the glycolysis markers glucose transporter 1 (GLUT1) and hexokinase 2 (HK2) with FDG uptake. RESULTS: Organ-specific uptake analysis showed specific FDG avidity of the tumor tissue. Standard scanning protocol was determined to include 150 μCi FDG injection dose and scanning after one hour. Comparison of heterotopic and orthotopic implanted mice revealed a long growth interval for orthotopic models with a high uptake in similar PDX tissues. The H-score of GLUT1 and HK2 expression in tumor cells correlated with the measured maximal standardized uptake value values (GLUT1: Pearson r=0.743, P=0.009; HK2: Pearson r=0.605, P=0.049). CONCLUSIONS This preclinical gastric cancer PDX based [¹⁸F]-FDG-PET/MRI protocol reveals tumor specific FDG uptake and shows correlation to glucose metabolic proteins. Our findings provide a PET/MRI PDX model that can be applicable for translational gastric cancer research.

PURPOSE: Herein, we report characteristics of ¹⁸F–fluorodeoxyglucose (FDG) uptake in abdominal aortic aneurysms (AAAs) during a long-term follow-up. In addition, we investigated the association between FDG uptake and the physician decision to perform an intervention.METHODS: We performed a retrospective review of 42 patients with AAAs who underwent FDG positron emission tomography (PET)/computed tomography (CT). The size of the AAA was measured in serial CT or PET/CT images. The long-term growth rate of AAAs was calculated by linear regression of the size change. Maximal SUV of the AAA (SUV(AAA)) and mean SUV of the blood pool (SUV(Blood)) were measured in PET/CT fusion images. To assess the FDG uptake of AAAs, the target-to-background ratio (TBR) was defined as the ratio of SUV(AAA) to SUV(Blood). We compared FDG uptake of AAAs with the long-term growth rate of AAAs and clinical data.RESULTS: TBR was not significantly different between patients with and without significant growth (1.55 ± 0.20 vs. 1.57 ± 0.14; P = 0.5599).However, in patients with significant growth, TBR exhibited a significant positive correlation with the growth rate (r² = 0.2601, P = 0.0306). TBR also exhibited a significant difference between patients with and without intervention (P = 0.0228).CONCLUSION: FDG uptake of AAA is associated with long-term growth of AAAs in a specified group that exhibits growth. FDG PET/CT may only be effective in predicting the long-term growth of AAAs in specific subgroups of patients. It is also suggested that FDG PET is potentially related to the clinical conditions of AAA patients who need surgical or interventional treatment.
Aortic Aneurysm, Abdominal ; Follow-Up Studies ; Humans ; Linear Models ; Positron-Emission Tomography ; Positron-Emission Tomography and Computed Tomography ; Retrospective Studies

PURPOSE: ⁶⁸Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid-D-Phe1-Tyr3-octreotide (⁶⁸Ga-DOTATOC) is taken up by activated macrophages, which accumulate in active inflammatory lesions. The purpose of this study was to investigate the feasibility of ⁶⁸Ga-DOTATOC PET/CT for assessment of vulnerable plaque, by evaluating correlation between aortic uptake of ⁶⁸Ga-DOTATOC and cardiovascular risk factors.METHODS: Fifty patients with neuroendocrine tumors who underwent ⁶⁸Ga-DOTATOC PET/CT were retrospectively enrolled. The uptakes in the thoracic aorta were measured by two methods: multi-sample region-of-interest (ROI) method and single volume-of-interest (VOI) method. TBRmax-avg, TBRmean-avg, TBRmax-VOI, and TBRmean-VOI were defined by maximum and mean target-to-background ratio (TBR) from the multi-sample ROI method and the single VOI method, respectively.RESULTS: Framinghamrisk score (FRS) exhibited significant correlations with TBRmax-avg and TBRmean-avg, aswell as TBRmax-VOI (r = 0.3389–0.4593, P < 0.05 for all). TBRmax-avg and TBRmax-VOI were significantly higher in high FRS group than in low FRS group (1.48 ± 0.21 vs. 1.70 ± 0.17, P < 0.001 for TBRmax-avg and 1.90 ± 0.33 vs. 2.25 ± 0.36, P = 0.002 for TBRmax-VOI). TBR exhibited high correlations between the two measuring methods (r = 0.9684, P < 0.001 for TBRmean-avg and TBRmean-VOI and r = 0.8681, P < 0.001 for TBRmax-avg and TBRmax-VOI).CONCLUSIONS: ⁶⁸Ga-DOTATOC uptake in the thoracic aorta exhibited a significant correlation with cardiovascular risk factors, which suggests the feasibility of ⁶⁸Ga-DOTATOC PET for vulnerable plaque imaging, with a simple measurement of the single VOI method that is comparable to the multi-sample ROI-based approach.
Aorta, Thoracic ; Atherosclerosis ; Humans ; Macrophages ; Methods ; Neuroendocrine Tumors ; Positron-Emission Tomography and Computed Tomography ; Retrospective Studies ; Risk Factors

PURPOSE: Although ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a standard imaging modality for response evaluation in FDG-avid lymphoma, there is a controversy using FDG PET in indolent lymphoma. The purpose of this study was to investigate the effectiveness of quantitative indexes on FDG PET in response evaluation of the indolent lymphoma.METHODS: Fifty-seven indolent lymphoma patients who completed chemotherapy were retrospectively enrolled. FDG PET/computed tomography (CT) scans were performed at baseline, interim, and end of treatment (EOT). Response was determined by Lugano classification, and progression-free survival (PFS) by follow-up data. Maximumstandardized uptake value (SUV(max)), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured in the single hottest lesion (target A) or five hottest lesions (target B). Their efficacies regarding response evaluation and PFS prediction were evaluated.RESULTS: On EOT PET, SUV(max), and MTVof both targets were well associated with visual analysis. Changes between initial and EOT PET were not significantly different between CR and non-CR groups. On interim PET, SUV(max), and %ΔSUV(max) in both targets were significantly different between CR and non-CR groups. For prediction of PFS, most tested indexes were significant on EOT and interim PET, with SUVmax being the most significant prognostic factor.CONCLUSION: Quantitative indexes of FDG PET are well associated with Lugano classification in indolent lymphoma. SUV(max) measured in the single hottest lesion can be effective in response evaluation and prognosis prediction on interim and EOT PET.
Classification ; Disease-Free Survival ; Drug Therapy ; Follow-Up Studies ; Glycolysis ; Humans ; Lymphoma ; Positron-Emission Tomography ; Prognosis ; Retrospective Studies ; Tumor Burden