Aim To investigate the relationships between various clinical variables and the metformin‐induced accumulation of fluorodeoxyglucose (FDG) in the intestine, with distinction between the intestinal wall and lumen, in individuals with type 2 diabetes who were receiving metformin treatment and underwent 18F‐labelled FDG ([18F]FDG) positron emission tomography (PET)‐MRI. Materials and Methods We evaluated intestinal accumulation of [18F]FDG with both subjective (a five‐point visual scale determined by two experienced radiologists) and objective analyses (measurement of the maximum standardized uptake value [SUVmax]) in 26 individuals with type 2 diabetes who were receiving metformin and underwent [18F]FDG PET‐MRI. [18F]FDG accumulation within the intestinal wall was discriminated from that in the lumen on the basis of SUVmax. Results SUVmax for the large intestine was correlated with blood glucose level (BG) and metformin dose, but not with age, body mass index, HbA1c level or estimated glomerular filtration rate (eGFR). SUVmax for the small intestine was not correlated with any of these variables. Visual scale analysis yielded essentially similar results. Metformin dose and eGFR were correlated with SUVmax for the wall and lumen of the large intestine, whereas BG was correlated with that for the wall. Multivariable analysis identified metformin dose as an explanatory factor for SUVmax in the wall and lumen of the large intestine after adjustment for potential confounders including BG and eGFR. Conclusions Metformin dose is an independent determinant of [18F]FDG accumulation in the wall and lumen of the large intestine in individuals treated with this drug.

Positron emission tomography (PET)-computed tomography has revealed that metformin promotes the intestinal accumulation of [ 18 F]fluorodeoxyglucose (FDG), a nonmetabolizable glucose derivative. It has remained unknown, however, whether this accumulation occurs in the wall or intraluminal space of the intestine. We here addressed this question with the use of [ 18 F]FDG PET-MRI, a recently developed imaging method with increased accuracy of registration and high softtissue contrast. RESEARCH DESIGN AND METHODSAmong 244 individuals with type 2 diabetes who underwent PET-MRI, we extracted 24 pairs of subjects matched for age, BMI, and HbA 1c level who were receiving treatment with metformin (metformin group) or were not (control group). We evaluated accumulation of [ 18 F]FDG in different portions of the intestine with both a visual scale and measurement of maximum standardized uptake value (SUV max ), and such accumulation within the intestinal wall or lumen was discriminated on the basis of SUV max . RESULTSSUV max of the jejunum, ileum, and right or left hemicolon was greater in the metformin group than in the control group. [ 18 F]FDG accumulation in the ileum and right or left hemicolon, as assessed with the visual scale, was also greater in the metformin group. SUV max for the intraluminal space of the ileum and right or left hemicolon, but not that for the intestinal wall, was greater in the metformin group than in the control group. CONCLUSIONSMetformin treatment was associated with increased accumulation of [ 18 F]FDG in the intraluminal space of the intestine, suggesting that this drug promotes the transport of glucose from the circulation into stool.

Objectives This study aimed to evaluate the diagnostic performance of the lung zero-echo time (ZTE) sequence in FDG PET/ MRI for detection and differentiation of lung lesions in oncologic patients in comparison with conventional two-point Dixonbased MR imaging. Methods In this single-institution retrospective study approved by the institutional review board, 209 patients with malignancies (97 men and 112 women; age range, 17-89 years; mean age, 66.5 ± 12.9 years) underwent 18 F-FDG PET/MRI between August 2017 and August 2018, with diagnostic Dixon and ZTE under respiratory gating acquired simultaneously with PET. Image analysis was performed for PET/Dixon and PET/ZTE fused images by two readers to assess the detectability and differentiation of lung lesions. The reference standard was pathological findings and/or the data from a chest CT. The detection and differentiation abilities were evaluated for all lesions and subgroups divided by lesion size and maximum standardized uptake value (SUVmax). Results Based on the reference standard, 227 lung lesions were identified in 113 patients. The detectability of PET/ZTE was significantly better than that of PET/Dixon for overall lesions, lesions with a SUVmax less than 3.0 and lesions smaller than 4 mm (p < 0.01). The diagnostic performance of PET/ZTE was significantly better than that of PET/Dixon for overall lesions and lesions smaller than 4 mm (p < 0.01). Conclusions ZTE can improve diagnostic performance in the detection and differentiation of both FDG-avid and non-FDG-avid lung lesions smaller than 4 mm in size, yielding a promising tool to enhance the utility of FDG PET/MRI in oncology patients with lung lesions. Key Points • The detection rate of PET/ZTE for lesions with a SUVmax of less than 1.0 was significantly better than that of PET/Dixon. • The performance for differentiation of PET/ZTE for lesions that were even smaller than 4 mm in size were significantly better than that of PET/Dixon. • Inter-rater agreement of PET/ZTE for the differentiation of lesions less than 4 mm in size was substantial and better than that of PET/Dixon.

Radiation therapy is a useful treatment for tumors and vascular malformations of the central nervous system. Radiation therapy is associated with complications, including leukoencephalopathy, radiation necrosis, vasculopathy, and optic neuropathy. Secondary tumors are also often seen long after radiation therapy. Secondary tumors are often benign tumors, such as hemangiomas and meningiomas, but sometimes malignant gliomas and soft tissue sarcomas emerge. We review the imaging findings of complications that may occur after brain radiation therapy.

<b>OBJECTIVE</b> <p>Positron emission tomography (PET)–computed tomography has revealed that metformin promotes the intestinal accumulation of [¹⁸F]fluorodeoxyglucose (FDG), a nonmetabolizable glucose derivative. It has remained unknown, however, whether this accumulation occurs in the wall or intraluminal space of the intestine. We here addressed this question with the use of [¹⁸F]FDG PET–magnetic resonance imaging (MRI), a recently developed imaging modality with increased accuracy of registration and high soft-tissue contrast.</p> <p><b>RESEARCH DESIGN AND METHODS</b></p> <p>Among 244 individuals with type 2 diabetes who underwent PET-MRI, we extracted 24 pairs of subjects matched for age, BMI, and HbA_1c level who were (metformin group) or were not (control group) receiving treatment with metformin. We evaluated accumulation of [¹⁸F]FDG in different portions of the intestine with both a visual scale and measurement of maximum standardized uptake value (SUV_max), and such accumulation within the intestinal wall or lumen was discriminated on the basis of SUV_max.</p> <p><b>RESULTS</b></p> <p>SUV_max of the jejunum, ileum, and right or left hemicolon was greater in the metformin group than in the control group. [¹⁸F]FDG accumulation in the ileum and right or left hemicolon as assessed with the visual scale was also greater in the metformin group. SUV_max for the intraluminal space of the ileum and right or left hemicolon, but not that for the intestinal wall, was greater in the metformin group than in the control group.</p> <p><b>CONCLUSIONS</b></p> <p>Metformin treatment was associated with increased accumulation of [¹⁸F]FDG in the intraluminal space of the intestine, suggesting that this drug promotes the transport of glucose from the circulation into stool.</p>