Assessment of liver ischemia reperfusion injury in mice using hepatic T 2 mapping: Comparison with histopathology.

Background: Liver ischemia reperfusion injury (IRI) occurs during liver surgery or transplantation resulting in an inflammatory response, tissue damage, and functional impairment of the organ.
Purpose: To assess the feasibility of T ₂ mapping for noninvasive quantification of liver edema after partial liver IRI in mice.
Study Type: Prospective, experimental study.
Animal Model: Partial liver IRI was induced in C57BL/6-mice by transient clamping of the left lateral and median liver lobes for 35 (n = 8), 45 (n = 6), 60 (n = 17), or 90 minutes (n = 5). For comparison, healthy C57BL/6-mice were examined as controls (n = 9).
Field Strength/sequence: Functional liver MRI was performed on a 7T scanner using a respiratory-triggered multiecho spin-echo sequence.
Assessment: Healthy control mice and mice with partial liver IRI on day 1 after surgery, and additionally on day 7 in a subgroup with 60 minutes IRI (n = 8) were examined. Maps of T ₂ relaxation time of liver tissue were used to assess distribution, severity of tissue edema (mean T ₂ time), and the percentage of edematous liver tissue.
Statistical Test: One-way analysis of variance (ANOVA) with Tukey's honest significant difference (HSD), paired t-tests, Pearson's test for correlation of MRI parameters with levels of liver enzymes, and histopathology, receiver operating characteristic (ROC) analysis.
Results: Significant tissue edema induced by liver IRI as compared to the control group was detected by increased mean T ₂ times in groups with 60 minutes (P < 0.001) and 90 minutes IRI (P < 0.001). The percentage of edematous liver tissue significantly increased with longer ischemia times (controls 3.4 ± 0.4%, 35 minutes 5.3 ± 0.6%, 45 minutes 23.3 ± 7.6%, 60 minutes 39.7 ± 3.6%, 90 minutes 51.3 ± 4.5%). Mean T ₂ times and the percentage of edematous liver tissue significantly correlated with elevation of liver enzymes (P < 0.001), histological evidence of liver injury (r = 0.80 and r = 0.82, P < 0.001), and neutrophil infiltration (r = 0.70 and r = 0.74, P < 0.001). In the subgroup with follow-up, the severity (P < 0.01) and extent of liver edema decreased significantly over time (P < 0.01).
Data Conclusion: T ₂ mapping allows quantification and follow-up of liver injury in mice.
Level of Evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1586-1594.
(© 2018 International Society for Magnetic Resonance in Medicine.)