Gd-EOB-DTPA-enhanced MRI T1 mapping for assessment of liver function in rabbit fibrosis model: comparison of hepatobiliary phase images obtained at 10 and 20 min

Quantitative assessment of liver function with hepatocyte fraction: Comparison with T1 relaxation-based indices

PURPOSE

This study aimed to assess the use of hepatocyte fraction in gadoxetic acid-enhanced magnetic resonance imaging (MRI) for quantitatively evaluating the liver function in comparison with T1 relaxation-based indices.

METHODS

This retrospective study included 79 patients with chronic liver disease, who were divided into 2 groups based on the results of the indocyanine green retention test (ICG). All patients underwent a gadoxetic acid-enhanced MRI of the liver. Pre- and post-contrast Look-Locker sequences were used 20 min after gadoxetic acid administration to acquire T1 mapping. Two readers independently identified and measured the MRI parameters [five T1 relaxation-based indices (T1pre, T1post, rrT1, R1post/R1pre and ΔR1) and two hepatocyte fraction indices (HeF and K_Hep)]. An Independent-samples t test was used to compare each parameter for the two groups. Pearson correlation analysis was used to analyze the correction in each parameter and 15-minute ICG retention rate (ICG-R15). Receiver operating characteristic analyses were performed to differentiate the diagnostic performance of each parameter in ICG-R15 ≤ 20 % and ICG-R15 > 20 % groups.

RESULTS

T1pre and T1post were significantly lower in the ICG-R15 ≤ 20 % group than in the ICG-R15 > 20 % group (P < 0.05). rrT1, R1post/R1pre, ΔR1, HeF, and K_Hep were significantly higher in the ICG-R15 ≤ 20 % group than in the ICG-R15 > 20 % group (P < 0.05). The correction coefficients between T1pre, T1post, rrT1, R1post/R1pre, ΔR1, HeF, K_Hep, and ICG-R15 were 0.343, 0.783, -0.833, -0.781, -0.803, -0.819, and -0.832, respectively. The area under the curves (AUCs) of T1pre, T1post, rrT1, R1post/R1pre, ΔR1, HeF, and K_Hep in assessing the ICG-R15＞20 % groups were 0.761, 0.945, 0.912, 0.912, 0.948, 0.945, and 0.950, respectively. K_Hep had the highest AUC, sensitivity, and specificity.

CONCLUSION

Hepatocyte fraction based on gadoxetic acid-enhanced T1-mapping MRI is an efficient diagnostic tool for the quantitative evaluation of liver function.

Combining 18F-FDG PET and Gd-EOB-DTPA-enhanced MRI for staging liver fibrosis

AIM

To evaluate the diagnostic performance of combining ¹⁸F-2-fluoro-2-D-deoxyglucose-positron emission tomography (¹⁸F-FDG PET) and gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) for liver fibrosis staging.

MATERIALS AND METHODS

Male New Zealand white rabbits (n = 48) were treated with carbon tetrachloride (CCl4) to induce liver fibrosis, while control group rabbits (n = 8) received normal saline. The liver tissues of rabbits were histopathologically examined (classified according to the METAVIR classification system) for liver fibrosis staging and real-time polymerase chain reaction (RT-PCR) was used to ensure diagnostic accuracy. Integrated PET/MRI was performed. The mean standardised uptake value (SUV_mean) and relative enhancement (RE) were evaluated for different liver fibrosis stages using a Mann-Whitney U test. The performance of PET/MRI was evaluated by using the receiver operating characteristic curve (ROC) and the area under the ROC curve (AUC).

KEY FINDINGS

In total, 10, 16, and 8 rabbits classified into no fibrosis (F0), mild fibrosis (F1-2), and severe fibrosis (F3-4) categories, respectively. There were significant differences in SUV_mean and RE between F0 and F3-4 and between F1-2 and F3-4 (p < 0.01), but no significance between F0 and F1-2 (p > 0.5). Combined SUV_mean and RE performed well in staging liver fibrosis, with AUC of 0.8 for F0 or greater, 0.744 for F0 or F1-2, 0.945 for F1-2 or F3-4, and 0.962 for F3-4.

SIGNIFICANCE

Combining SUV_mean and RE provides high accuracy for grading liver fibrosis, especially in the differentiation between F1-2 and F3-4. ¹⁸F-FDG and Gd-EOB-DTPA-enhanced PET/MRI could be a non-invasive diagnostic method to guide the selection of clinical treatment options.

Feasibility of T1 mapping with histogram analysis for the diagnosis and staging of liver fibrosis: Preclinical results

PURPOSE

To compare the diagnostic accuracy of parameters derived from the histogram analysis of precontrast, 10-min hepatobiliary phase (HBP) and 20-min HBP T1 maps for staging liver fibrosis (LF).

METHODS

LF was induced in New Zealand white rabbits by subcutaneous injections of carbon tetrachloride for 4-16 weeks (n = 120), and 20 rabbits injected with saline served as controls. Precontrast, 10-min and 20-min HBP modified Look-Locker inversion recovery (MOLLI) T1 mapping was performed. Histogram analysis of T1 maps was performed, and the mean, median, skewness, kurtosis, entropy, inhomogeneity and 10th/25th/75th/90th percentiles of T1_native, T1_10min and T1_20min were derived. Quantitative histogram parameters were compared. For significant parameters, further receiver operating characteristic (ROC) analyses were performed to evaluate the potential diagnostic performance in differentiating LF stages.

RESULTS

Finally, 17, 20, 21, 21 and 20 rabbits were included for the F0, F1, F2, F3, and F4 pathological grades of fibrosis, respectively. The mean/75th of T1_native, entropy of T1_10min and entropy/mean/median/10th of T1_20min demonstrated a significant good correlation with the LF stage (|r| = 0.543-0.866, all P < 0.05). The 75th of T1_native, entropy_10min, and entropy_20min were the three most reliable imaging markers in reflecting the stage of LF. The area under the ROC curve of entropy_20min was larger than that of entropy_10min (P < 0.05 for LF ≥ F2, ≥F3, and ≥ F4) and the 75th of T1_native (P < 0.05 for LF ≥ F2 and ≥ F3) for staging LF.

CONCLUSION

Magnetic resonance histogram analysis of T1 maps, particularly the entropy derived from 20-min HBP T1 mapping, is promising for predicting the LF stage.