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Background: Currently, an advanced imaging method may be necessary for magnetic resonance imaging (MRI) to diagnosis and quantify liver fibrosis (LF). Purpose: To evaluate the feasibility of the multicompartmental restriction spectrum imaging (RSI) model to characterize LF in a mouse model. Methods: Thirty mice with carbon tetrachloride (CCl4)‐induced LF and eight control mice were investigated using multi‐b‐value (ranging from 0 to 2000 s/mm2) diffusion‐weighted imaging (DWI) on a 3T scanner. DWI data were processed using RSI model (2–5 compartments) with the Bayesian Information Criterion (BIC) determining the optimal model. Conventional ADC value and signal fraction of each compartment in the optimal RSI model were compared across groups. Receiver operating characteristics (ROC) curve analysis was performed to determine the diagnosis performances of different parameters, while Spearman correlation analysis was employed to investigate the correlation between different tissue compartments and the stage of LF. Results: According to BIC results, a 4‐compartment RSI model (RSI4) with optimal ADCs of 0.471 × 10−3, 1.653 × 10−3, 9.487 × 10−3, and > 30 × 10−3, was the optimal model to characterize LF. Significant differences in signal contribution fraction of the C1 and C3 compartments were observed between LF and control groups (P = 0.018 and 0.003, respectively). ROC analysis showed that RSI4‐C3 was the most effective single diffusion parameter for characterizing LF (AUC = 0.876, P = 0.003). Furthermore, the combination of ADC values and RSI4‐C3 value increased the diagnosis performance significantly (AUC = 0.894, P = 0.002). Conclusion: The 4‐compartment RSI model has the potential to distinguish LF from the control group based on diffusion parameters. RSI4‐C3 showed the highest diagnostic performance among all the parameters. The combination of ADC and RSI4‐C3 values further improved the discrimination performance. [ABSTRACT FROM AUTHOR]

Background: In experimental animal models, implantation location might influence the heterogeneity and overall development of the tumor, leading to an interpretation bias. Purpose To investigate the effects of implantation location in experimental tumor model using magnetic resonance imaging (MRI) and pathological findings. Study Type: Prospective. Subjects: Forty‐five breast cancer‐bearing mice underwent orthotopic (N = 15) and heterotopic (intrahepatic [N = 15] and subcutaneous [N = 15]) implantation. Field Strength/Sequence: Sequences including: T1‐weighted turbo spin echo sequence, T2‐weighted blade sequence, diffusion‐weighted imaging, pre‐ and post‐contrast T1 mapping, multi‐echo T2 mapping at 3.0 T. Assessment MRI was performed at 7, 14, and 21 days after implantation. Native T1, post‐contrast T1, T2, and apparent diffusion coefficient (ADC) of tumors, the tumor volume and necrosis volume within tumor were obtained. Lymphocyte cells from H&E staining, Ki67‐positive, and CD31‐positive cells from immunohistochemistry were determined. Statistical Tests: One‐way analysis of variance and Spearman's rank correlation were performed. P value <0.05 was considered statistically significant. Results: The tumor volume (intrahepatic vs. orthotopic vs. subcutaneous: 587.50 ± 77.62 mm3 vs. 814.00 ± 43.85 mm3 vs. 956.13 ± 119.22 mm3), necrosis volume within tumor (89.10 ± 26.60 mm3 vs. 292.41 ± 57.92 mm3 vs. 179.91 ± 31.73 mm3, respectively), ADC at day 21 (543.41 ± 42.28 vs. 542.92 ± 99.67 vs. 369.83 ± 42.90, respectively), and post‐contrast T1 at all timepoints (day 7: 442.00 ± 11.52 vs. 435.00 ± 22.90 vs. 394.33 ± 29.95; day 14: 459.00 ± 26.11 vs. 436.83 ± 26.01 vs. 377.00 ± 27.83; day 21: 463.50 ± 23.49 vs. 458.00 ± 34.28 vs. 375.00 ± 30.55) were significantly different between three groups. Necrosis volumes of subcutaneous and intrahepatic tumors were significantly lower than those of orthotopic tumors. The CD31‐positive rate in the intrahepatic implantation was significantly higher than in orthotopic and subcutaneous groups. Necrosis volume (r = −0.71), ADC (r = −0.85), and post‐contrast T1 (r = −0.75) were strongly correlated with vascular invasion index. Data Conclusion: Orthotopic and heterotopic tumors have their unique growth kinetics, necrosis volume, and vascular invasion. Non‐invasive MR quantitative parameters, including ADC and post‐contrast T1, may reflect vascular invasion in mice. Level of Evidence: 1 Technical Efficacy: Stage 3 [ABSTRACT FROM AUTHOR]