Abstract: Objective　To compare the differences between PET/CT and integrated PET/MR in the diagnosis of intracranial tumors, and the effects on clinical  therapy strategy. Methods　Thirty-two patients with intracranial tumors detected by sequentially 18F-FDG PET/CT imaging and PET/MR intracranial imaging on the same day were enrolled. Pearson correlation analysis, Bland-Altman analysis and t test were used to compare the maximum standard uptake value (SUVmax) and target area/back ground ratio (T/B) of PET/CT and PET/MR. With reference to the pathological and follow-up results, the χ2 test was used to compare the differences in detection rates of PET/CT and PET/MR. Results　A total of 78 lesions (32 patients) were confirmed by pathology or clinical follow-up including 10 glioma, 11 lymphoma, 55 metastases, 1 meningiomas and 1 pituitary tumor. All lesions were benign. PET/MR found 31 more lesions compared with PET/CT, and there was a significant difference between them (χ2=40.266，P＜0.01). In the 78 lesions, the 18F-FDG uptake of 40 lesions were significantly higher than intracranial parenchyma, with good agreement in SUVmax-MR and SUVmax-CT (r=0.799，P＜0.05). For other 38 lesions with comparable or lower uptake of intracranial parenchymal, PET/MR detected 28 more lesions than PET/CT, and the detection rate was statistically significant (χ2=44.335, P＜0.01). There were 36 lesions with obvious edema found in both examinations (χ2=2.060，P＞0.05), although 3 only found edema with no clear lesions in PET/CT. Among the 42 lesions without edema, 29 more lesions were found in PET/MR, which was significant compared with that of PET/CT (χ2=44.290， P＜0.01). For 62 lesions with Dmax＜3.0 cm, 31 more lesions were detected by PET/MR than PET/CT (χ2=41.338, P＜0.01). Conclusion　The detection rate of integrated PET / MR is significantly higher than that of PET/CT. Sequentially 18F-FDG PET/CT imaging and PET/MR intracranial imaging can obviously make up the deficiency of detection rate of PET/CT for intracranial lesions, guiding clinical selection of treatment options.

Key words: magnetic resonance spectroscopy, tomography, X-Ray computed, positron-emission tomography, fluorodeoxyglucose F18, intracranial tumors, detection rate