Abstract
ObjectiveTo assess in a high-resolution model of thin liver rat slices which viscoelastic parameter at three-dimensional multifrequency MR elastography has the best diagnostic performance for quantifying liver fibrosis.Materials and MethodsThe study was approved by the ethics committee for animal care of our institution. Eight normal rats and 42 rats with carbon tetrachloride induced liver fibrosis were used in the study. The rats were sacrificed, their livers were resected and three-dimensional MR elastography of 5±2 mm liver slices was performed at 7T with mechanical frequencies of 500, 600 and 700 Hz. The complex shear, storage and loss moduli, and the coefficient of the frequency power law were calculated. At histopathology, fibrosis and inflammation were assessed with METAVIR score, fibrosis was further quantified with morphometry. The diagnostic value of the viscoelastic parameters for assessing fibrosis severity was evaluated with simple and multiple linear regressions, receiver operating characteristic analysis and Obuchowski measures.ResultsAt simple regression, the shear, storage and loss moduli were associated with the severity of fibrosis. At multiple regression, the storage modulus at 600 Hz was the only parameter associated with fibrosis severity (r = 0.86, p<0.0001). This parameter had an Obuchowski measure of 0.89+/−0.03. This measure was significantly larger than that of the loss modulus (0.78+/−0.04, p = 0.028), but not than that of the complex shear modulus (0.88+/−0.03, p = 0.84).ConclusionOur high resolution, three-dimensional multifrequency MR elastography study of thin liver slices shows that the storage modulus is the viscoelastic parameter that has the best association with the severity of liver fibrosis. However, its diagnostic performance does not differ significantly from that of the complex shear modulus.
Highlights
Over the past decade, various studies have shown the usefulness of ultrasound and MR elastography for the assessment of the severity of liver fibrosis [1,2,3,4,5,6,7,8,9,10,11,12]
At simple regression, the shear, storage and loss moduli were associated with the severity of fibrosis
Our high resolution, three-dimensional multifrequency MR elastography study of thin liver slices shows that the storage modulus is the viscoelastic parameter that has the best association with the severity of liver fibrosis
Summary
Various studies have shown the usefulness of ultrasound and MR elastography for the assessment of the severity of liver fibrosis [1,2,3,4,5,6,7,8,9,10,11,12]. With multifrequency MR elastography, the exponent of the frequency power law (c), can be calculated and reflects wave scattering related to the architectural organization of the tissue [14]. The usefulness of these different viscoelastic parameters for assessing the severity of fibrosis has not been much explored [10,15,16]
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