In vivo DTI assessment of hepatic ischemia reperfusion injury in an experimental rat model

Purpose

To investigate hepatic ischemia reperfusion injury (IRI) using diffusion tensor imaging (DTI).

Materials and Methods

Ten Sprague‐Dawley rats were scanned at 7 Tesla (T) with DTI using b‐value of 1000 s/mm² and 6 gradient directions before, 2 h, and 1 day after 30‐min total hepatic IRI. Apparent diffusion coefficient or mean diffusivity (MD), directional diffusivities and fractional anisotropy (FA) were measured. Seven of the animals were also examined with spin‐echo echo‐planar diffusion‐weighted imaging (DWI) with seven b‐values up to 2000 s/mm² to estimate the true diffusion coefficient (D), blood pseudodiffusion coefficient (D*), and perfusion fraction (f) using a bi‐compartmental model.

Results

MD 2 h after IRI (0.77 ± 0.07 × 10^?3 mm²/s) was significantly lower (P < 0.01) than that before (1.03 ± 0.07 × 10^?3 mm²/s) and 1 day after IRI (1.01 ± 0.05 × 10^?3 mm²/s). Meanwhile, FA 2 h after IRI (0.33 ± 0.03) was significantly higher (P < 0.01) than that before (0.21 ± 0.02) and 1 day after IRI (0.20 ± 0.02). The bi‐compartmental model analysis revealed the transient decrease in D, D* and f 2 h after IRI. Liver histology showed the multifocal cell swelling 3 h after IRI and widespread cell necrosis/apoptosis 1 day after IRI. Sinusoidal narrowing and congestion of erythrocytes were also observed 3 h and 1 day after IRI.

Conclusion

DTI can characterize hepatic IRI by detecting the transient change in both MD and FA. J. Magn. Reson. Imaging 2009;30:890–895. © 2009 Wiley‐Liss, Inc.