Liver T1 relaxation time of the 'normal liver' in healthy Asians: measurement with MOLLI and B1-corrected VFA methods at 3T.

OBJECTIVES: Liver T1 is a potential magnetic resonance imaging biomarker for liver diseases. This study aimed to determine the T1 relaxation time of the normal liver (PDFF<5%) in healthy Asian volunteers using modified look-locker inversion recovery (MOLLI) and B1 inhomogeneity-corrected variable flip angle (B1-corrected VFA). METHODS: 60 healthy Asian volunteers without focal or diffuse liver disease underwent a liver scan at 3T magnetic resonance. Proton density fat fraction (PDFF) and liver stiffness measurements were applied for the quantification of liver fat and fibrosis. T1 mapping was performed with MOLLI and B1-corrected VFA sequences. Bland-Altman, linear regression, Student t-test, and one-way analysis of variance were used for statistical analysis. RESULTS: The mean T1 relaxation times of the whole liver were 901 ± 34 ms by MOLLI, and 948 ± 29 ms by B1-corrected VFA in healthy volunteers. There was a strong correlation (r = 0.86, p < 0.0001) for liver T1 between two T1 mapping methods. There were significant differences between the right and left lobes in liver T1 relaxation times using both methods (p < 0.05). Gender and Asian ethnic disparities had no impact on liver T1 relaxation times. CONCLUSION: T1 relaxation times of the normal liver (PDFF<5%) in healthy volunteers were established by MOLLI and B1-corrected VFA T1 mapping methods at 3T. It may provide suitable and robust baseline values for the assessment of liver diseases. ADVANCES IN KNOWLEDGE: Gender and Asian ethnic disparities do not impact liver T1 relaxation time measurements.

Chronic kidney disease: pathological and functional assessment with diffusion tensor imaging at 3T MR.

OBJECTIVE: Our objective was to evaluate pathological and functional changes in chronic kidney disease (CKD) using diffusion tensor imaging (DTI) at 3 T. METHODS: There were fifty-one patients with CKD who required biopsy and 19 healthy volunteers who were examined using DTI at 3 T. The mean values of fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) were obtained from the renal parenchyma (cortex and medulla). Correlations between imaging results and the estimated glomerular filtration rate (eGFR), as well as pathological damage (glomerular lesion and tubulointerstitial injury), were evaluated. RESULTS: The renal cortical FA was significantly lower than the medullary in both normal and affected kidneys (p < 0.001). The parenchymal FA was significantly lower in patients than healthy controls, regardless of whether eGFR was reduced. There were positive correlations between eGFR and FA (cortex, r = 0.689, p = 0.000; and medulla, r = 0.696, p = 0.000), and between eGFR and ADC (cortex, r = 0.310, p = 0.017; and medulla, r = 0.356, p = 0.010). Negative correlations were found between FA and the glomerular lesion (cortex, r = -0.499, p = 0.000; and medulla, r = -0.530, p = 0.000), and between FA and tubulointerstitial injury (cortex, r = -0.631, p = 0.000; and medulla, r = -0.724, p = 0.000). CONCLUSION: DTI is valuable for noninvasive assessment of renal function and pathology in patients with CKD. A decrease in FA could identify the glomerular lesions, tubulointerstitial injuries, and eGFR.