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Background: The hippocampus (HP) plays a critical role in memory and orientational functions and is functionally heterogeneous along the longitudinal anterior-posterior axis. Although the previous study has reported volumetric atrophy in hippocampal subfields of patients with poststroke dementia (PSD), how the functional connectivity (FC) is altered in these subfields remains unclear., Purpose: To examine the FC changes of the HP subfields in patients with PSD., Study Type: Prospective., Population: Seventeen normal controls, 20 PSD, and 24 nondemented poststroke (PSND) patients., Field Strength/sequence: A 3.0 T/ T1-weighted imaging, resting-state functional and diffusion tensor imaging., Assessment: We first segmented the HP using independent component analysis, and then used granger causality analysis to calculate the directed FCs (dFCs) between the subfields and the whole brain, and compared the dFCs among PSD, PSND, and controls., Statistical Tests: Student's t-test, chi-square test, one-way ANCOVA, multiple regression, support vector machine, multiple comparison correction, and reproducibility analysis. A P value < 0.05 was considered statistically significant., Results: Our results showed HP was functionally divided into HP head , HP body , and HP tail bilaterally along the longitudinal axis. PSD patients showed significant dementia-specific decreases in the inward information flow and increases in the outward information flow associated with the bilateral entire HP/HP head and left HP body (P < 0.05). Moreover, we observed significant correlations (P < 0.05) between the cognition score and the dFCs related to the bilateral entire HP and left HP head in the PSD group. Furthermore, dFCs of the HP and its subfields improved the classification between the PSD and PSND patients (accuracy/sensitivity/specificity: 94%/95%/93%) compared to the clinical and demographic parameters alone., Data Conclusion: These findings suggest that altered transmission and reception of information in the HP. These alternations were specific to individual subfields in PSD patients and may offer insight into the neurophysiological mechanisms underlying PSD., Evidence Level: 1 TECHNICAL EFFICACY: Stage 2., (© 2021 International Society for Magnetic Resonance in Medicine.)

Purpose: To evaluate the pharmacokinetic parameters of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in diagnosing and staging liver fibrosis in rabbits., Materials and Methods: DCE-MRI with gadodiamide (Gd-DTPA-BMA) was performed on a 3.0 Tesla, 60 cm bore MR scanner for rabbits with CCl4 -induced liver fibrosis, and an untreated control group. Fibrosis was staged according to the METAVIR system: control (F0; n = 13), nonadvanced fibrosis (F1-2; n = 15), and advanced fibrosis (F3-4; n = 12). The DCE-MRI parameters K(trans) , kep , Ve , and vp were measured with a dual-input extended Tofts model. Receiver operating characteristic analyses were performed to assess the diagnostic performance of K(trans) , Ve , and vp in staging liver fibrosis., Results: Both K(trans) and Ve decreased with increasing fibrosis stage. K(trans) of the control group was significantly different from that of the overall fibrosis group, nonadvanced group, and advanced group (P < 0.001 for all). Significant differences were found between Ve of the control group and that of the overall fibrosis and advanced groups (P = 0.019 and P = 0.009, respectively). For K(trans) , the areas under the receiver operating characteristic curve (AUROCs) for discriminating the control group from the overall fibrosis and advanced fibrosis groups were 0.909 (95% confidence interval [CI], 0.809-1.000), and 0.936 (95% CI,0.847-1.000), respectively. For discriminating between the control and nonadvanced fibrosis groups, the AUROC of K(trans) was 0.887 (95% CI, 0.762-1.000). The AUROCs of K(trans) were higher than those of Ve and vp for discriminating between the control and overall fibrosis groups, the control and nonadvanced fibrosis groups, and the control and advanced fibrosis groups. Pharmacokinetic parameters were negatively correlated with fibrosis stage (K(trans) , rho = -0.668, P < 0.001; Ve , rho = -0.438, P = 0.005; vp , rho = -0.360, P = 0.023)., Conclusion: Among pharmacokinetic parameters of DCE-MRI in our study, K(trans) was an excellent predictor for differentiating fibrotic livers from normal livers, and differentiating normal livers from nonadvanced or advanced fibrosis livers. J. Magn. Reson. Imaging 2016;44:98-104., (© 2015 Wiley Periodicals, Inc.)

Purpose: To evaluate the possibility of using a variable flip angle (VFA) T1 mapping technique to diagnose liver fibrosis., Materials and Methods: Liver fibrosis was induced in rabbits by repetitive administration of carbon tetrachloride (CCl4 ). T1 -weighted magnetic resonance imaging (MRI) was performed in 29 animals (liver fibrosis, n = 18; control, n = 11) using a series of nonenhanced liver acquisition volume acceleration (LAVA) with VFAs at 3.0T. Hepatic T1 relaxation times were measured via regions of interest, which were correlated with subsequent histologic confirmation. The results of T1 mapping in assessment of liver fibrosis were compared with that of apparent diffusion coefficient (ADC) values., Results: The mean T1 relaxation time of the control group was the lowest (250.07 ± 88.12 msec), followed by the nonadvanced fibrosis group (387.83 ± 166.58 msec) and the advanced fibrosis group (496.90 ± 291.24 msec). T1 relaxation time measurements differed significantly between the liver fibrosis group and control group (P < 0.05), with a trend of increased mean T1 relaxation times as the fibrotic stage increased. Statistically significant differences were observed between the control group and the nonadvanced fibrosis group (P < 0.05), however with much overlap between the less severe stages. In discriminating between the control group and liver fibrosis group, stage F0-1 (control and stage F1) and stage F2-3, stage F0-2 (control and stage F1-2) and stage F3, area under the receiver operating characteristic (ROC) curves were 0.803 (cutoff value 273.01 msec), 0.712 (cutoff value 371.54 msec), and 0.696 (cutoff value 276.99 msec), respectively. No difference was found between T1 relaxation times and ADC values in assessment of liver fibrosis in our study., Conclusion: VFA T1 mapping may become a noninvasive imaging tool for the diagnosis of liver fibrosis., (© 2015 Wiley Periodicals, Inc.)