Objective To track superparamagnetic iron oxide (SPIO)-labeled pancreatic islet cells in rats using 3.0T magnetic resonance imaging (MRI), and to detect the survival and rejection of grafts after transplantation. Methods Twenty male Wistar rats and 5 male Lewis rats were included in the study. SPIO-labeled pancreatic islet cells were tracked using a GE 3.0T Signa Excite MRI scanner with an animal coil. The images of SPIO-labeled islet cells in rats after transplantation were compared with those of the unlabeled ones. FSE T2WI sequence and GRE T2*WI sequence were used for the detection. The sensitivity of images for detection of grafts was also compared. SPIO-labeled pancreatic islet cells isolated from Wistar and Lewis rats were transplanted into the liver of Wistar rats. Afterwards, the survival and rejection of islet cells were observed sequentially in these two growps. The rats in the syngeneic group were sacrificed 3 months post-transplantation, while the rats in the allogeneic group were sacrificed 3 weeks post-transplantation. MRI of the grafts were correlated with the pathological results. Results SPIO-labeled pancreatic islet cells were seen on MRI as distinct homogenous, hypointense spots in the liver. GRE T2*WI were more sensitive to the detection of SPIO-labeled islet cells than FSE T2WI. The relative count of hypointense spots in the syngeneic group were (90.03±9.52)%, (92.87±18.21)% and (86.25±24.81)%, respectively at 1 week, 2 weeks and 3 weeks after transplantation, while the relative count in the allogeneic group were (41.40±15.41)%, (33.41±14.01)% and (23.58±16.78)%, respectively. The difference between these counts was statistically significant (P<0.01). Iron particles were detected only in the SPIO-labeled cells. Three months post-transplantation, the grafts were found well-preserved in the liver of the rats of the syngeneic group, while only a few grafts were found in that of the allogeneic group. Conclusions MRI can be used to track SPIO-labeled islet cells in vivo, and has significant value in detecting the survival and rejection of grafts after transplantation in rats.

Objective To evaluate the role of local gyrification index (LGI) in the early diagnosis of Alzheimer disease(AD). Methods Thirty‐five amnestic‐type mild cognitive impairment patients (aMCI group), 34 mild AD patients (mild AD group) and 33 healthy volunteers (normal control group) were studied. All patients underwent high resolution MRI examination and mini‐mental state examination (MMSE). Using surface‐based morphometry, the FreeSurfer was employed to access LGI of vertex over every participant′s whole cortical surface, then we calculated the mean LGI (mLGI) of each subject′s left and right hemisphere separately. Taking age, gender and educational year as covariance, analysis of covariance was used to compare the difference of mLGI of left and right brain among 3 groups, then Bonferroni was done between every two groups. Analysis of covariance was applied to compare the difference of LGI of every participant among 3 groups, and Monte Carlo method was employed to perform multiple comparison corrections. The correlations between the MMSE scores and LGIs of the three groups were analyzed. Results Compared with normal control group(left 3.03±0.12,right 3.02±0.13), the mLGI of hemispheres in mild AD group(left 2.94±0.11,right 2.93±0.10) decreased respectively(P<0.05). The difference of mLGI of hemispheres between aMCI group(left 2.96 ± 0.10, right 2.96 ± 0.09) and normal control group had no statistical significance(P>0.05). The difference of mLGI of hemispheres between aMCI group and mild AD group also had no statistical significance(P>0.05). The aMCI group showed decrease of LGI in some brain regions located at the right temporal lobe, bilateral frontal and parietal lobe compared with the normal control group. While compared with aMCI group, decreased LGIs was presented in some brain regions located at bilateral temporal, occipital, frontal lobe and the right parietal lobe of mild AD group. There was a positive correlation between MMSE scores and LGIs of some brain regions in the bilateral temporal, occipital lobe, the left frontal lobe and the right parietal lobe in the three groups. Conclusion LGI is conductive in the early diagnosis of AD and can serve as an imaging marker for monitoring disease progresses.