Tomoelastography for the Evaluation of Pediatric Nonalcoholic Fatty Liver Disease

Abstract

Objectives: Today, nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in children and adults alike. Yet, the noninvasive evaluation of disease severity remains a diagnostic challenge. In this study, we apply multifrequency magnetic resonance elastography (mMRE) for the quantification of liver steatosis and fibrosis in adolescents with NAFLD. Methods: Fifty adolescents (age range, 10-17 years; mean BMI, 33.9 kg/m 2 ; range, 21.4-42.1 kg/m 2 ) with biopsy-proven NAFLD were included in this prospective study. Multifrequency magnetic resonance elastography was performed using external multifrequency vibrations of 30 to 60 Hz and tomoelastography postprocessing, resulting in penetration rate (a) and shear wave speed (c). Hepatic fat fraction was determined using Dixon method. The diagnostic accuracy of mMRE in grading liver steatosis and staging liver fibrosis was assessed by receiver operating characteristic curve analysis. Results: Multifrequency magnetic resonance elastography parameters c and a were independently sensitive to fibrosis and steatosis, respectively, providing area under the receiver operating characteristic values of 0.79 (95% confidence interval [CI], 0.66-0.92), 0.91 (95% CI, 0.83-0.99), and 0.90 (95% CI, 0.80-0.99) for the detection of any (≥F1), moderate (≥F2), and advanced (≥F3) fibrosis, and 0.87 (95% CI, 0.76-0.97) and 0.87 (95% CI, 0.77-0.96) for the detection of moderate (≥S2) and severe (S3) steatosis. Conclusions: One mMRE measurement provides 2 independent parameters with very good diagnostic accuracy in detecting moderate and advanced fibrosis as well as moderate and severe steatosis in pediatric NAFLD.

Diagnostic performance of tomoelastography of the liver and spleen for staging hepatic fibrosis

“…This poor sensitivity of a, as a representation of damping, for staging fibrosis has been shown previously [12,20]. However, an even more pronounced significant correlation of hepatic a with steatosis has been demonstrated recently by a study investigating nonalcoholic fatty liver disease and should be implemented in future studies and data analysis for liver fat quantification [24]. Our results support their finding that hepatic damping increases with steatosis, although the liver fat content in our cohort was substantially lower.…”

Reduction of breathing artifacts in multifrequency magnetic resonance elastography of the abdomen

“…Furthermore, these ROIs were refined by empirical thresholds of 1 m/s for softer organs (liver and pancreas) and 1.5 m/s for stiffer organs (spleen and kidneys), to remove blood vessels that appear enlarged in SWS maps. 24,35 Without motion, both M (MRE magnitude averaged over 96 consecutively acquired image slice blocks) and SWS maps are expected to display sharp edges at tissue interfaces, which is reflected in the Laplacian Δ of the images. Therefore, image sharpness was quantified by computing the variance (σ) of the Laplacian Δ of MRE images as described in Pech-Pacheco et al 36 A Laplacian derivative kernel of size 3 × 3 was applied to both the mean magnitude M (averaged over 96 image slice blocks) and SWS maps.…”

“…Published studies report multifrequency 3D MRE of abdominal organs with up to eight wave dynamics consecutively acquired at up to seven frequencies, resulting in total acquisition times exceeding 5 minutes, during which patients are allowed to breathe freely. [8][9][10]24,25 The same protocol with breath-hold acquisition would exceed 20 minutes. 26 Nevertheless, there are good reasons for multifrequency MRE of abdominal organs, including measurement of viscoelastic dispersion or improved detail resolution.…”

Pediatric Fatty Liver and Obesity: Not Always Justa Matter of Non-Alcoholic Fatty Liver Disease

“…When considering other available imaging modalities which can obtain more accurate quantitative evaluations of fat content, a recent meta-analysis has confirmed the superiority of MRI and MRI spectroscopy (MRS) [61,62]. MR elastography has also been used to accurately assess hepatic fibrosis [63]. However, equipment for these techniques are not present in every hospital and are available mainly in specialized centers.…”