Quality Control of Magnetic Resonance Elastography Using Percent Measurable Liver Volume Estimation

Abstract

Background: Although studies have described factors associated with failed magnetic resonance elastography (MRE), little is known about what factors influence usable elastography data. Purpose: To identify factors that have a negative impact on percent measurable liver volume (pMLV), defined as the proportion of usable liver elastography data relative to the volume of imaged liver in patients undergoing MRE. Study Type: Retrospective. Subjects: A total of 264 patients (n = 132 males, n = 132 females; mean age = 57 years) with suspected or known chronic liver disease underwent MRE paired with a liver protocol MRI. Field strength/Sequence: MRE was performed on a single 1.5 T scanner using a two-dimensional gradient-recalled echo phase-contrast sequence with a passive acoustic driver overlying the right hemiliver. Assessment: Stiffness maps (usable data at 95% confidence) and liver contours on magnitude images of the MRE acquisition were manually traced and used to assess mean stiffness and pMLV. Hepatic fat fraction and R 2 * values were also calculated. The distance from the acoustic wave generator on the skin surface to the liver edge was measured. Two radiologists performed the MR analyses with 50 overlapping cases for inter-reader analysis. Statistical Tests: Linear regression was performed to identify factors significantly associated with pMLV. Intraclass correlation was performed for inter-reader reliability. Results: pMLV was 31% AE 20% (range 0%-86%). Complete MRE failure (i.e. pMLV = 0%) occurred in 10 patients (4%). Multivariate linear regression identified higher hepatic fat fraction, R 2 *, BMI, and driver-to-liver surface distance; male sex; and lower mean liver stiffness was significantly independently associated with lower pMLV. Intraclass correlation for pMLV was 0.96, suggestive of excellent reliability. Data Conclusion: Higher fat fraction, R 2 *, BMI, driver-to-liver surface distance, male sex, and lower mean liver stiffness were associated with lower pMLV. Optimization of image acquisition parameters and driver placement may improve MRE quality, and pMLV likely serves as a diagnostic utility quality control metric. Level of Evidence: 3 Technical Efficacy Stage: 2

Individualized driver amplitude in liver MR elastography: a linear regression study

“…MRE scans of the liver often necessitate multiple trial scans due to varying standards for driver amplitude settings (3)(4)(5)(9)(10)(11)(12). Excessively high driver amplitudes can result in issues such as rib fractures, discomfort during movement, and difficulties in breath-holding, while excessively low driver amplitudes may hinder or weaken shear wave transmission into the liver, consequently diminishing the accuracy of hepatic stiffness measurements.…”

“…Lorton et al (11) conducted a study on liver MRE in pediatric patients and recommended the application of quantitative analysis to determine the appropriate driver amplitude. Initially, our intention was to incorporate three quantitative parameters, namely pMLV, LMVR, and AMVR, based on elastogram with a 95% confidence map to facilitate quality control in liver MRE (3). However, during the Lasso regression analysis, both pMLV and LMVR were identified as non-contributory variables and were subsequently excluded from consideration.…”

“…For an accurate assessment of liver disease, high-quality MRE images are required. These images display regular shear waves crossing through the liver, resulting in the highest percent liver measurable volume (pMLV) (3) and lowest abdominal missing volume ratio (AMVR). However, in practice, the factors that impact shear waves are typically complex.…”

Editorial for “Quality Control of MR Elastography Using Percent Measurable Liver Volume Estimation”

“…In this issue of JMRI, Ballard et al present percent measurable liver volume (pMLV) as a potential metric of MRE quality. 4 Their proposed metric reflects quantification of the measurable area of the liver on the elastograms divided by the total area of the liver imaged at those levels. They define the measurable liver area as all pixels confined to the liver that lie within the ≥95% boundaries of the overlaid confidence map.…”

“…In this issue of JMRI , Ballard et al present percent measurable liver volume (pMLV) as a potential metric of MRE quality 4 . Their proposed metric reflects quantification of the measurable area of the liver on the elastograms divided by the total area of the liver imaged at those levels.…”