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

Abstract

Objectives To determine the diagnostic performance, cutoff values, and optimal drive frequency range for staging hepatic fibrosis using tomoelastography by multifrequency MR elastography of the liver and spleen. Methods This prospective study consecutively enrolled a total of 61 subjects between June 2014 and April 2017: 45 patients with chronic liver disease and proven stage of fibrosis and 16 healthy volunteers. Tomoelastography was performed at 1.5 T using six drive frequencies from 35 to 60 Hz. Cutoff values and AUC were calculated. Shear wave speed (in m/s) of the liver and spleen was assessed separately and in combination as a surrogate of stiffness. Results For compound multifrequency processing of the liver, cutoff and AUC values by fibrosis stage were as follows: F1, 1.52 m/s and 0.89; F2, 1.55 m/s and 0.94; F3, 1.67 m/s and 0.98; and F4, 1.72 m/s and 0.98. Diagnostic performance of the best single drive frequencies (45 Hz, 55 Hz, 60 Hz) was similar (mean AUC = 0.95, respectively). Combined analysis of the liver and spleen slightly improved performance at 60 Hz in F4 patients (mean AUC = 0.97 vs. 0.95, p = 0.03). Full-field-of-view elastograms displayed not only the liver and spleen but also small anatomical structures including the pancreas and major vessels. Conclusion Tomoelastography provides full-field-of-view elastograms with unprecedented detail resolution and excellent diagnostic accuracy for staging hepatic fibrosis. Our analysis of single-frequency tomoelastography suggests that scan time can be further reduced in future studies, making tomoelastography easier to implement in clinical routine. Key Points • Tomoelastography provides full-field-of-view elastograms of the abdomen with unprecedented detail resolution and excellent diagnostic accuracy for staging hepatic fibrosis. • Diagnostic performance of single-frequency tomoelastography at higher frequencies (45 Hz, 55 Hz, 60 Hz) and compound multifrequency processing are equivalent for staging hepatic fibrosis. • Combined assessment of hepatic and splenic stiffness slightly improves diagnostic performance for staging hepatic fibrosis.

Standard‐space atlas of the viscoelastic properties of the human brain

“…Variability between studies of up to 17% of the overall population mean was observed, depending on the region and measure; however, this variability is also likely due to the small populations included in each study (as small as six participants) and differences in their sex distributions. Future investigations may want to fully address the impact of scanner, frequency, and resolution effects, similar to previous studies that have investigated the impact of MR field strength in the brain (Hamhaber et al, 2010) or in how protocol variations can affect baseline measurements in liver MRE (Bohte et al, 2013;Reiter et al, 2020). These technical alternatives to data acquisition will be important aspects to consider in the event of the adoption of brain MRE as a clinical tool within neuroradiology.…”

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

“…For parameter quantification, organ‐specific ROIs were manually drawn based on time‐averaged magnitude MRE (M) images and accounting for whole‐organ boundaries, as illustrated in Figure 2. 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.…”

“…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.…”

Fusing acceleration and saturation techniques with wave amplitude labeling of time‐shifted zeniths MR elastography

“…The applied mechanical vibrations in MRE can be applied at a single frequency or multiple frequencies. The multifrequency approach may allow measurement of parameters that are independent of frequency through viscoelastic modeling or via analysis of the regression line of stiffness and frequency, and achieves elastograms with superior spatial resolution 10‐16 . Furthermore, motion‐encoding gradients (MEG) can be applied in 3 orthogonal directions to obtain more accurate elasticity maps or determine elasticity tensors.…”

“…The multifrequency approach may allow measurement of parameters that are independent of frequency through viscoelastic modeling or via analysis of the regression line of stiffness and frequency, and achieves elastograms with superior spatial resolution. [10][11][12][13][14][15][16] Furthermore, motion-encoding gradients (MEG) can be applied in 3 orthogonal directions to obtain more accurate elasticity maps or determine elasticity tensors. However, despite the increased information provided by these techniques, neither multidirectional nor multifrequency techniques are in routine clinical practice for liver MRE.…”