Accuracy of multiecho magnitude‐based MRI (M‐MRI) for estimation of hepatic proton density fat fraction (PDFF) in children

Abstract

Purpose To assess accuracy of magnitude-based magnetic resonance imaging (M-MRI) in children to estimate hepatic proton density fat fraction (PDFF) using two to six echoes, with magnetic resonance spectroscopy (MRS)-measured PDFF as a reference standard. Materials and Methods This was an IRB-approved, HIPAA-compliant, single-center, cross-sectional, retrospective analysis of data collected prospectively between 2008 and 2013 in children with known or suspected non-alcoholic fatty liver disease (NAFLD). Two hundred and eighty-six children (8 – 20 [mean 14.2 ± 2.5] yrs; 182 boys) underwent same-day MRS and M-MRI. Unenhanced two-dimensional axial spoiled gradient-recalled-echo images at six echo times were obtained at 3T after a single low-flip-angle (10°) excitation with ≥ 120-ms recovery time. Hepatic PDFF was estimated using the first two, three, four, five, and all six echoes. For each number of echoes, accuracy of M-MRI to estimate PDFF was assessed by linear regression with MRS-PDFF as reference standard. Accuracy metrics were regression intercept, slope, average bias, and R2. Results MRS-PDFF ranged from 0.2 – 40.4% (mean 13.1 ± 9.8%). Using three to six echoes, regression intercept, slope, and average bias were 0.46 – 0.96%, 0.99 – 1.01, and 0.57 – 0.89%, respectively. Using two echoes, these values were 2.98%, 0.97, and 2.72%, respectively. R2 ranged 0.98 – 0.99 for all methods. Conclusion Using three to six echoes, M-MRI has high accuracy for hepatic PDFF estimation in children.

Bone marrow fat content is correlated with hepatic fat content in paediatric non-alcoholic fatty liver disease

“…This study was conducted at a single institution, which may limit generalisability, but the large and diverse cohort supports the validity of the present results in children who have known or suspected NAFLD. The present research participants did not have biopsy-confirmed NAFLD; however, a previously validated M-MRI technique [10] was used, which has been shown to correlate well with histological assessment in children with NAFLD [11]. In addition, three different MRI techniques were used to assess biological associations.…”

“…Measuring the thoracic spine would have required patient and coil repositioning, thus adding considerable time to the examination. Although subsequent reports have validated C-MRI to measure hepatic PDFF in children, M-MRI was selected to measure hepatic PDFF because it was the most extensively validated method at the time study was initiated (2010) [10,11]. Additionally, high-resolution anatomical MRI was used to measure abdominal adipose tissue.…”

“…The M-MRI technique has been previously described [10,11]. Images were centred on the liver and acquired in the axial plane with the parameters listed in Table 1.…”

“…Proton density fat fraction (PDFF) is emerging as the standard quantitative magnetic resonance imaging (MRI) biomarker of tissue triglyceride concentration. Advanced MRI techniques were utilised to quantify bone marrow PDFF [9] and hepatic PDFF [10,11] as quantitative biomarkers of fat content in these organs. High-resolution MRI images were to measure abdominal adipose tissue compartments.…”

Quantitative Imaging Biomarkers of NAFLD

“…Thereafter, PDFF has been used in prospective epidemiological and observational studies in patient populations in which liver biopsy is traditionally not indicated, including the type II diabetic population in primary care setting [71] as well as in healthy children and young adults [39, 66, 72]. As the primary end-point in a randomized clinical trial for steatosis-reducing pharmacotherapy, PDFF has proven to be useful as an alternative to biopsy [69, 73, 74] as well as for cross-sectional observational studies [75, 76].…”