Biexponential Analysis of Diffusion-Tensor Imaging of the Brain in Patients with Cirrhosis before and after Liver Transplantation

Abstract

BACKGROUND AND PURPOSE: DTI has shown increased MD of water molecules in the brain of patients with cirrhosis, consistent with low-grade edema. This study further characterizes this edema by using biexponential analysis of DTI data, a technique that may differentiate cytotoxic and vasogenic edema.

Pathogenesis of Hepatic Encephalopathy: Role of Ammonia and Systemic Inflammation

“…These alterations to astrocyte morphology can be seen in the brains of patients with chronic hyperammonaemia due to congenital disorders of the urea cycle enzymes, as well as in various experimental animal models of hyperammonaemia, 41,42 and in astrocyte cultures chronically exposed to hyperammonaemia. 43 Experimental models of CLF in rats have consistently shown no evidence of BBB breakdown, 28,44 however Chavarria and colleagues 45 have recently provided evidence for the presence of both cytotoxic and vasogenic edema in cirrhotic patients awaiting liver transplantation. It has been proposed that low-grade astrocyte swelling, as may be seen in CLF, 46 could have significant functional consequences despite the absence of clinically overt ICH, and impairment of the cross-talk between swollen astrocytes and neurones has also been suggested to alter cerebral function.…”

Assessment of Angiographic Vascularity of Meningiomas with Dynamic Susceptibility Contrast-Enhanced Perfusion-Weighted Imaging and Diffusion Tensor Imaging

“…28 The perfusion-related diffusion can be considered as an incoherent motion caused by random capillary organization, and its contribution to the ADC measurement can be assessed by use of an intravoxel incoherent motion model. 29,30 However, to our knowledge, there is no wellestablished model to evaluate the effect of perfusion on diffusion anisotropy. We speculate that higher perfusion resulted in greater incoherent motion and subsequently lower FA in meningiomas with high angiographic vascularity.…”

Identification of Minimal Hepatic Encephalopathy in Patients with Cirrhosis Based on White Matter Imaging and Bayesian Data Mining

“…The thresholds resulting in best classification result (eg, a threshold of 0.25 SD above the mean MD value or a threshold of 0.75 SD below mean FA value) were chosen and included in the following validation analyses. [7][8][9][10][11] and impaired cerebral structures [12][13][14] have been demonstrated to play an important role in the MHE mechanisms. WM edema, which could be extracellular and/or cytotoxic in origin, [8][9][10] is considered closely associated with a metabolic disorder of ammonia in the brain tissue of patients with MHE.…”

“…Of WM imaging techniques, diffusion tensor imaging, measuring the appropriate metrics such as mean diffusivity (MD), reflecting water movement across cell membranes, and fractional anisotropy (FA), reflecting microstructural in-tegrity of WM, is demonstrated to reveal the neuropathologic processes of MHE through group-level comparison. 8,9,12,14,15,17 To date, however, there is no study using DTI-derived feature maps to discriminate patients with and without MHE in cirrhosis at the individual level; this discrimination remains an important question for clinicians. 6,19 The only related study is the report of Sugimoto et al, 16 which used a DWI-based metric (apparent diffusion coefficient) instead of DTI to classify patients with or without MHE, but in which patients in the intermediate state were excluded; this method obviously results in inadequate assessment.…”

“…Abnormalities in brain white matter, such as low-grade edema [7][8][9][10][11] and structural impairments, [12][13][14] have been well-revealed in MHE by MR imaging. These WM abnormalities are believed to be responsible for poor neurologic performances 12,15,16 and brain dysfunctions 17,18 in MHE and to be associated with HE development, 9,11,16 suggesting that WM imaging may be useful in characterizing potential MHE biomarkers.…”