Objective: To investigate the value of hybrid 18F-FDG PET/MR in patients with ischemic cerebrovascular disease. Methods: A total of 10 healthy volunteers and 17 patients with chronic unilateral internal carotid artery (ICA) or middle cerebral artery (MCA) occlusion underwent hybrid 18F-FDG PET/MR examination. The images were analyzed by two experienced physicians. The mean ADC value (ADCmean), mean standardized uptake value (SUVmean) and the maximum standardized uptake value (SUVmax) were analyzed between left and right brain regions of healthy volunteers. ADCmean, SUVmean and SUVmax of corresponding areas of the cerebral infarction and contralateral corresponding areas, the surrounding areas of the cerebral infarction and contralateral side of patients were also compared. Results: MRI of 10 healthy volunteers showed no abnormal performance. 18F-FDG images were clear and the metabolic distribution of each brain region was symmetrical. ADCmean, SUVmean, SUVmax were not statistically different between the left and right brain regions (all P>0.05). The cerebral infarctions were observed in MRI of 17 patients, and ADCmean, SUVmean and SUVmax significantly reduced on the affected side (all P<0.01), while ADCmean, SUVmean and SUVmax also significantly reduced in the surrounding areas of the cerebral infarction (all P<0.01). Conclusion: Hybrid 18F-FDG PET/MR examination can evaluate patients with chronic ischemic cerebrovascular disease and provide information of brain structure and brain metabolism.

Objective To explore the consistency of time-of-flight (TOF) technology of PET/MRI and PET/CT for max standardized uptake value (SUVmax) of body malignant tumors.Methods A retrospective analysis of TOF-PET/CT and TOF-PET/MR imaging data about twenty patients with body malignant tumors was performed.Patients were divided into two groups (each n=10),including PET/CT first and sequentially PET/MR group and PET/MR first and sequentially PET/CT group.Bland-Altman figure was used to evaluate consistency of SUVmax of malignant lesions between TOF-PET/CT and TOF-PET/MR.Multi-way ANOVA was used to analysis effect of machine type and exam order on SUVmaxof malignant lesions in TOF-PET/CT and TOF-PET/MR.Results SUVmax of malignant lesions in TOF-PET/CT and TOF-PET/MR had good consistency in two groups (PET/CT first and sequentially PET/MR group:Mean difference was 3.06,95％CI was [-7.5,13.6];PET/MR first and sequentially PET/CT group:Mean difference was 3.0,95％CI was [-2.4,8.3]).SUVmax was not influenced by machine type (F=0.005,P=0.95),but exam order (F=46.00,P＜0.001).Conclusion PET/MR and PET/CT with TOF technology have comparative diagnostic value in SUVmaxof body malignant lesions.SUVmax of body malignant lesions increases in delay time,which is not related to machine type,but exam time.

Objective To investigate the relationship between spatial distribution of default mode network and glucose uptake.Methods Nine healthy subjects were scanned with hybrid PET/MR.Resting state MRI (rs-fMRI) and PET data were obtained.Spatial distribution analysis was performed between default mode network and glucose uptake.The relationship between the functional connectivity of default mode network and the distribution of glucose uptake were further analyzed.Results The similar spatial distribution pattern was found between default mode network and glucose uptake.Correlation between functional connectivity and glucose uptake in the default mode network showed that the best correlation coefficient between the values of functional connectivity and relative glucose uptake (rGU) was achieved in the right posterior cingulate cortex (rs =0.833,P＜0.001).Conclusion Hybrid PET/MR is very important to investigate neural mechanism of default mode network.

Objective:To evaluate the value of integrated PET/MR in assessing myocardial viability in ischemic heart disease.Methods:A total of 39 patients (28 males, 11 females; age (60.1±12.0) years) diagnosed with ischemic heart disease in Xuanwu Hospital, Capital Medical University were retrospectively enrolled from September 2020 to December 2021. All patients underwent cardiac 13N-NH 3·H 2O and 18F-FDG PET/MR examinations. Late gadolinium enhancement (LGE) sequence was included in MRI scan. PET and MRI images were analyzed and myocardial viability of each myocardial segment was evaluated according to the American Heart Association (AHA) 17 segment method. The extent of left ventricular infarcted myocardium was measured based on PET and MRI images. Weighted Kappa test was used to evaluate the agreement of PET and MRI in assessing myocardial viability. The extent of infarcted myocardium measured by PET and MRI was compared by paired- t test, and Pearson correlation analysis was used to assess the correlation between them. Results:There was a moderate agreement between PET and MRI in assessing myocardial viability ( Kappa=0.532, P<0.001), with the agreement rate of 69.83%(463/663). There was no significant difference but strong correlation between the extents of infarcted myocardium measured by PET and MRI ((23.89±14.23)% vs (23.55±11.90)%; t=-0.24, P=0.809; r=0.79, P<0.001). In segments with normal perfusion and metabolism on PET, 22.52% (100/444) showed abnormal enhancement on MRI. On the other hand, 39.89% (73/183) of the segments classified as non-viable on MRI showed normal or viable on PET. Conclusion:Integrated PET/MR is able to take full advantage of the complementary nature of PET and MRI, achieving the comprehensive and accurate evaluation of myocardial viability.

Objective:To explore the accuracy of 18F-fluorodeoxyglucose (FDG) PET/MR in preoperative localization of refractory epilepsy patients with conventional MRI negative. Methods:From August 2016 to December 2018, 57 refractory epilepsy patients (36 males, 21 females, age (24.0±10.3) years) with conventional MRI negative who underwent surgery in Xuanwu Hospital were retrospectively enrolled. All patients received interictal 18F-FDG PET/MR before surgery and the epileptogenic foci were determined by using visual and semi-quantitative methods. Patients were followed up for 1 year and the surgical outcome was evaluated according to Engel classification. The sensitivity, specificity and accuracy of 18F-FDG PET/MR in locating epileptogenic foci were calculated according to surgical resection and followed-up results as the " gold standard" . Results:Of 57 patients, 51(89.5%, 51/57) showed single or multiple hypo-metabolism focus on 18F-FDG PET/MR, and 6(10.5%, 6/57) showed no abnormal metabolism changes. The microstructure abnormality was found in 18 patients (31.6%, 18/57) on 18F-FDG PET/MR images. Follow-up results were obtained from 46 patients, and 84.8%(39/46) with seizure improvement (Engel Ⅰ-Ⅲ). The sensitivity, specificity and accuracy of 18F-FDG PET/MR in preoperative localization of epileptic foci was 90.0%(27/30), 3/16 and 65.2%(30/46), respectively. Conclusion:18F-FDG PET/MR is helpful for the detection of epileptic foci in patients with MRI-negative refractory epilepsy, and can provide reliable information for further surgical treatment.

Objective To investigate the correlation between left ventricular dysfunction and cogni-tive impairment in patients with ischemic heart disease(IHD),and explore the potential patho-genesis of cognitive impairment in IHD patients.Methods Fifty IHD patients who underwent hybrid cardiac PET/MR in our hospital from September 2020 to December 2022 were retrospec-tively enrolled in this study.According to their Montreal cognitive assessment(MoCA)scores,they were categorized into a cognitively normal group(21 cases,MoCA score ≥26)and a cogni-tively declining group(29 cases,MoCA score＜26).All patients received 13N-NH3·H2O myocar-dial perfusion imaging and 18F-FDG cardiac PET/MR to evaluate cardiac function and obtain car-diac imaging parameters.Spearman correlation analysis was applied to analyze the correlation between cardiac PET/MR parameters and MoCA scores.General linear model analysis was applied to analyze the correlation between MoCA scores and cardiac PET/MR parameters after adjusting for co variates.Results Compared with the cognitively normal group,the patients in the cognitively declining group had significantly lower stroke volume[56.95(47.51,77.64)ml vs 82.66(73.88,92.92)ml,P=0.001],stroke volume index[34.07(28.93,43.20)ml/m2 vs 44.28(38.06,49.49)ml/m2,P=0.008],cardiac output[3.92(3.18,5.34)L/min vs 5.13(4.58,5.67)L/min,P=0.007],and cardiac index[(2.42±0.68)L/(min·m2)vs(2.78±0.39)L/(min·m2),P=0.021].Spearman correlation analysis revealed that MoCA score was positively correlated with stroke volume(r=0.497,P=0.001),stroke volume index(r=0.365,P=0.009)and cardiac output(r=0.361,P=0.010).After adjusting for sex,age,education level and vascular risk factors,MoCA score re-mained positively correlated with stroke volume(r=0.497,P=0.003).Conclusion Systemic hy-poperfusion in IHD patients may be one of the mechanisms leading to cognitive impairment.

One patient with gallbladder mass had transient jaundice and was diagnosed with gallbladder carcinoma by abdominal ultrasonography， contrast-enhanced CT， MRCP， and PET-CT. Surgical exploration showed enlarged gallbladder and a mass in the neck of the gallbladder pressing against the hilum of the liver， with no manifestation of tumor invasion， and there were no signs of liver metastasis. Only cholecystectomy was performed for the patient. The pathological diagnosis was tubular adenoma of the gallbladder without carcinogenesis. This case is characterized by a large gallbladder tumor， without marginal infiltration on imaging or malignant transformation based on pathology.