Multiparametric functional magnetic resonance imaging for evaluation of hepatic warm ischemia-reperfusion injury in a rabbit model

Magnetic Resonance Diffusion Tensor Imaging Characterize the Hepatic Ischemia-Reperfusion Injury in an Animal Study

BACKGROUND

Hepatic ischemia-reperfusion (I/R) injury is the main cause of morbidity and mortality after hepatectomy; thus, new methods for reducing I/R injury are required. The aim of this study is to evaluate changes in the average apparent diffusion coefficient (ADCavg) and fractional anisotropy (FA) in rabbits with partial hepatic I/R injury with magnetic resonance diffusion tensor imaging (DTI).

METHODS

The left lobe of the rabbit liver underwent 60 minutes of ischemia followed by 0.5, 2, 6, 12, 24, and 48 hours of reperfusion. T2-weighted images (T2WI), T1-weighted images (T1WI), DTI, and contrast-enhanced T1WI were performed; 6 b values were used for DTI on 6 diffusion directions. The serum levels of transaminases and liver histopathology findings were examined.

RESULTS

In the early stage of I/R (0.5 hour), ADCavg decreased significantly and increased sharply to 2 hours, then increased from 6 hours to 48 hours of reperfusion, except for a transient decrease (24 hours). Meanwhile, FA showed almost the opposite trend, drastically increasing during the first 0.5 hour and then slightly decreasing until 48 hours of reperfusion, except for an obvious decrease in the 2-hours group. The serum levels of liver markers and the pathologic scores were sharply increased in the I/R group after reperfusion and correlated with DTI of hepatic tissue after I/R.

CONCLUSIONS

Diffusion tensor imaging is feasible for imaging I/R-induced liver damage and can discriminate isotropic properties of the liver after I/R injury with objective changes in the ADCavg and FA. Diffusion tensor imaging can be a promising novel approach for use in clinical management after liver surgery.

Molecular ultrasound imaging of neutrophil membrane-derived biomimetic microbubbles for quantitative evaluation of hepatic ischemia-reperfusion injury

Rationale: Early diagnosis of hepatic ischemia-reperfusion injury (HIRI), the major cause of early allograft dysfunction or primary non-function, is critical in orthotopic liver transplantation. However, liver biopsy is still the primary method for HIRI evaluation in clinical practice despite its numerous complications and shortcomings such as hemorrhage and inaccuracy. Herein, we aimed to develop a non-invasive, highly accurate, and specific method for detecting HIRI. Methods: We developed a top-down and bottom-up strategy to fabricate neutrophil biomimetic microbubbles (MB_neu). Neutrophil membrane was mixed with liposomes at a defined mass ratio by sonication. The air in the vial was exchanged with perfluoropropane, and then the solution was mechanically vibrated to form MB_neu. Results: MB_neu retained the neutrophil proteins, preferentially targeted inflamed hepatic tissue in a rat model of HIRI, and demonstrated physicochemical properties typical of liposome-based MBs because of its artificial phospholipid content. With MB_neu we can quantitively evaluate the severity of HIRI, which is helpful for early diagnosis and the prediction of outcome. In addition, MB_neu was shown to be safe and showed no immunogenicity. Conclusion: We demonstrated molecular ultrasound imaging of HIRI with MB_neu. This new synthesis strategy may be applied to different clinical scenarios using other cell types in the future.

In vivo multiparametric magnetic resonance imaging study for differentiating the severity of hepatic warm ischemia-reperfusion injury in a rabbit model

OBJECTIVES

To assess the value of multiparametric magnetic resonance imaging including intravoxel incoherent motion (IVIM), diffusion tensor imaging (DTI) and blood oxygen level dependent (BOLD) MRI in differentiating the severity of hepatic warm ischemia-reperfusion injury (WIRI) in a rabbit model.

METHODS

Fifty rabbits were randomly divided into a sham-operation group and four test groups (n = 10 for each group) according to different hepatic warm ischemia times. IVIM, DTI and BOLD MRI were performed on a 3 T MR scanner with 11 b values (0 to 800 s/mm²), 2 b values (0 and 500 s/mm²) on 12 diffusion directions, multiple-echo gradient echo (GRE) sequences (TR/TE, 75/2.57-24.25 ms), respectively. IVIM, DTI and BOLD MRI parameters, hepatic biochemical and histopathological parameters were compared. Pearson and Spearman correlation methods were performed to assess the correlation between these MRI parameters and laboratory parameters. Furthermore, receiver operating characteristic (ROC) curves were compiled to determine diagnostic efficacies.

RESULTS

True diffusion (Dslow), pseudodiffusion (Dfast), perfusion fraction (PF), mean diffusivity (MD) significantly decreased, while R2* significantly increased with prolonged warm ischemia times, and significant differences were found in all of biochemical and histopathological parameters (all P < 0.05). Dslow, PF, and R2* correlated significantly with all of biochemical and histopathological parameters (all |r| = 0.381-0.746, all P < 0.05). ROC analysis showed that the area under the ROC curve (AUC) of IVIM across hepatic WIRI groups was the largest among IVIM, DTI and BOLD.

CONCLUSIONS

Multiparametric MRI may be helpful with characterization of early changes and determination of severity of hepatic WIRI in a rabbit model.

Can Viscoelasticity Measurements Obtained Through Shear-Wave US Elastography be used to Monitor Hepatic Ischemia-Reperfusion Injury and Treatment Response? An Animal Study

This study aimed to investigate whether viscoelasticity measurements can be used to quantitatively analyze and monitor therapy response in hepatic ischemia-reperfusion injury (HIRI). All animals were divided into three groups: a sham operation group (n = 12), an ischemia-reperfusion injury (IRI) group (n = 12) and an andrographolide pre-treatment group (n = 6). To assess the feasibility of using shear-wave velocity (SWV) and shear-wave dispersion (SWD), shear-wave ultrasound elastography was applied onto IRI rats after 4 and 24 h of reperfusion or sham operation (each time point subgroup n = 6). For the verification experiments, six additional rats received andrographolide injection 2 h before IRI and were examined 24 h after reperfusion. The rats were sacrificed for biochemical and histopathological analyses after ultrasound scanning was performed. Compared with the sham group, the IRI group exhibited significantly higher SWD after both 4 and 24 h of reperfusion（10.69 ± 0.69 vs. 15.20 ± 3.23 and 9.01 ± 0.46 vs. 19.35 ± 0.86; p < 0.05). A positive correlation was found between SWD values and Suzuki's score (r = 0.621; p < 0.05). No correlation was found between SWV and Suzuki's score (r = 0.283; p > 0.05), although significant differences were found between the two groups after 24 h of reperfusion. Andrographolide treatment resulted in a significantly decreased SWD (15.24 ± 0.45 vs. 19.35 ± 0.86; p < 0.05), whereas SWV showed no statistically significant difference. This study demonstrated the potential of using viscoelasticity measurements for the diagnosis and therapeutic monitoring of HIRI, and that the use of SWD was significantly more advantageous than SWV.

Progress of intravoxel incoherent motion diffusion-weighted imaging in liver diseases

Traditional magnetic resonance (MR) diffusion-weighted imaging (DWI) uses a single exponential model to obtain the apparent diffusion coefficient to quantitatively reflect the diffusion motion of water molecules in living tissues, but it is affected by blood perfusion. Intravoxel incoherent motion (IVIM)-DWI utilizes a double-exponential model to obtain information on pure water molecule diffusion and microcirculatory perfusion-related diffusion, which compensates for the insufficiency of traditional DWI. In recent years, research on the application of IVIM-DWI in the diagnosis and treatment of hepatic diseases has gradually increased and has achieved considerable progress. This study mainly reviews the basic principles of IVIM-DWI and related research progress in the diagnosis and treatment of hepatic diseases.