The combination of MRI with PET would play an important role in clinical staging, diagnosis and treatment of cancer. Hybrid PET/MR provides a high resolution anatomical and metabolic imaging approach to evaluate human brain tumors. Clinically, [18F]-FDGPET is a well-established method and is able to be used to estimate the local cerebral metabolic rate of glucose consumption for patients with brain tumor. MRI shows not only structural but also functional imaging information. Recently, CEST, a molecular MRI technique, has been successfully employed to detect tumors. In previous studies, amide proton transfer-weighted (APTw) [1] and glucoCEST [2,3] MRI were both exploited to detect cancer. Unlike APTw MRI, however, in the clinical practice, it may be a challenge to image glucose hydroxyl groups in patients using glucoCEST MRI due to the rapid exchanging OH protons. The aim of this study was to comprehensively evaluate the glucose metabolism (a standard dose of [18F]-FDGPET) and APTw signal on human brain tumor using Hybrid PET/MR.Seven patients with brain tumor were scanned on a Philips Ingenuity TF PET/MR system. Conventional, APTw, and GlucoCEST MR images were acquired. Besides, a fast-field echo T1w image was acquired for PET attenuation correction (AC). The imaging parameters for CEST were: single short TSE, SENSE factor=2, TR = 3500 ms, TE = 11 ms, matrix = 128*64, FOV = 240*240 mm2, slice thickness = 6 mm. A 250*4 ms and 2 μT RF saturation was used. A protocol with multiple frequency offsets and averages was used for CEST acquisition [4]. MTR asymmetry was calculated at the offset of ± 3.5ppm for APTw and ±1.3ppm for glucoCEST. A 15 minute [18F]-FDG PET data was finally acquired 30 minutes after the injection of 250 MBq [18F]-FDG. The maximum SUV and mean SUV values were measured in tumor and normal tissues.As shown in Table 1, APTw MRI signals were increased in all tumor regions, as identified by the gadolinium-enhanced T1w MR images. For [18F]-FDG studies, four cases demonstrated clearly high uptake in tumor regions, two cases did not have clearly high uptake, and one case showed negative uptake in tumor regions. Figure 1 shows conventional MRI, CEST MRI, and PET/MR images for a 71-year-old man with meningioma. Both gadolinium enhancement and APTw MRI hyperintensity were observed in the lesion and PET/MR demonstrate a high [18F]-FDG uptake. MR and PET/MR images of a 43-year-old woman with glioma are shown in Figure 2. The gadolinium enhancement corresponded to the APTw high signal region, while the PET/MR image demonstrated a decreased [18F]-FDG uptake compared to the contra lateral normal -appearing white matter. As for the CEST effects of glucose at 1.3ppm, there was no lesion contrast for all these tumor cases.To explore the brain tumor microenvironment, multi-modality image techniques are needed in the clinic. Glucose metabolism and functional/molecular MR imaging information, such as gadolinium enhancement and APTw MRI, can assess brain tumors from different viewpoints. Due to the high rate of physiologic glucose metabolism in normal brain tissue, the detection capability of PET in the brain tumor is challenging since the [18F]-FDG PET uptake is only modest in the lesion, similar to or even less than that in normal gray matter [5]. APTw MR imaging can provide complementary physiological information for the exploration of brain tumor. A higher dosage of glucose will be expected in the promising glucoCEST MRI in the brain tumor detection. The hybrid PET/MR can provide comprehensive imaging information and improve clinical diagnosis and therapy evolutions.