Accuracy of MR elastography and anatomic MR imaging features in the diagnosis of severe hepatic fibrosis and cirrhosis

Purpose:

To compare the diagnostic accuracy of magnetic resonance imaging elastography (MRE) and anatomic MRI features in the diagnosis of severe hepatic fibrosis and cirrhosis.

Materials and Methods:

Three readers independently assessed presence of morphological changes associated with hepatic fibrosis in 72 patients with liver biopsy including: caudate to right lobe ratios, nodularity, portal venous hypertension (PVH) stigmata, posterior hepatic notch, expanded gallbladder fossa, and right hepatic vein caliber. Three readers measured shear stiffness values using quantitative shear stiffness maps (elastograms). Sensitivity, specificity, and diagnostic accuracy of stiffness values and each morphological feature were calculated. Interreader agreement was summarized using weighted kappa statistics. Intraclass correlation coefficient was used to assess interreader reproducibility of stiffness measurements. Binary logistic regression was used to assess interreader variability for dichotomized stiffness values and each morphological feature.

Results:

Using 5.9 kPa as a cutoff for differentiating F3‐F4 from F0‐2 stages, overall sensitivity, specificity, and diagnostic accuracy for MRE were 85.4%, 88.4%, and 87%, respectively. Overall interreader agreement for stiffness values was substantial, with an insignificant difference (P = 0.74) in the frequency of differentiating F3‐4 from F0‐2 fibrosis. Only hepatic nodularity and PVH stigmata showed moderately high overall accuracy of 69.4% and 72.2%. Interreader agreement was substantial only for PVH stigmata, moderate for C/R m, deep notch, and expanded gallbladder fossa. Only posterior hepatic notch (P = 0.82) showed no significant difference in reader rating.

Conclusion:

MRE is a noninvasive, accurate, and reproducible technique compared with conventional features of detecting severe hepatic fibrosis. J. Magn. Reson. Imaging 2012;35:1356–1364. © 2012 Wiley Periodicals, Inc.     

Repeatability of magnetic resonance elastography for quantification of hepatic stiffness

Purpose:

To determine the sources of variability of MRE hepatic stiffness measurements using healthy volunteers and patients and to calculate the minimum change required for statistical significance. Hepatic stiffness measured with magnetic resonance elastography (MRE) has demonstrated tremendous potential as a noninvasive surrogate of hepatic fibrosis, although the underlying repeatability of MRE for longitudinal tracking of liver disease has not been documented.

Materials and Methods:

MRE stiffness measurements from 20 healthy volunteers and 10 patients were obtained twice on the same day, and repeated 2–4 weeks later for volunteers in this institutional review board‐approved study. A linear mixed effects model was used to estimate the component sources of variability in the data.

Results:

The standard deviation of MRE measurements of the same individual on different days is 11.9% (percent of the measured stiffness) using the same reader and 12.0% using different readers. The standard deviation of the difference between two measurements (i.e., longitudinal change in an individual) is 17.4%; the corresponding 95% confidence interval for zero change is (?27.0%, 37.0%).

Conclusion:

MRE is a repeatable method for quantifying liver stiffness. Using the described MRE technique, changes greater than 37.0% of the smaller measured stiffness value represent meaningful changes in longitudinal liver stiffness measurements. J. Magn. Reson. Imaging 2010;31:725–731. © 2010 Wiley‐Liss, Inc.

     

Measurement of liver stiffness with two imaging techniques: magnetic resonance elastography and ultrasound elastometry

Purpose

To cross‐validate the magnetic resonance elastography (MRE) technique with a clinical device, based on an ultrasound elastometry system called Fibroscan.

Materials and Methods

Ten healthy subjects underwent an MRE and a Fibroscan test. The MRE technique used a round pneumatic driver at 60 Hz to generate shear waves inside the liver. An elastogram representing a map of the liver stiffness was generated allowing for the measurement of the average liver stiffness inside a region of interest. The Fibroscan technique used an ultrasound probe (3.5 MHz) composed of a vibrator that sent low‐frequency (50 Hz) shear waves inside the right liver lobe. The probe acts as an emitter‐receptor that measures the velocity of the waves propagated inside the liver tissue.

Results

The mean shear stiffness measured with the MRE and Fibroscan techniques were 1.95 ± 0.06 kPa and 1.79 ± 0.30 kPa, respectively. A higher standard deviation was found for the same subject with Fibroscan.

Conclusion

This study shows why MRE should be investigated beyond the Fibroscan. The MRE technique provided elasticity of the entire liver, meanwhile the Fibroscan provided values of elasticity locally. J. Magn. Reson. Imaging 2008;28:1287–1292. © 2008 Wiley‐Liss, Inc.     

Magnetic resonance elastography in the liver at 3 Tesla using a second harmonic approach

Magnetic resonance elastography (MRE) using mechanical stimulation has demonstrated diagnostic value and clinical promise in breast, liver, and kidney at 1.5 Tesla (T). However, MRE at 1.5T suffers from long imaging times and would benefit from greater signal‐to‐noise for more robust postprocessing. We present an MRE sequence modified for liver imaging at 3.0T. To avoid artifacts in the phase images, the sequence maintains a short TE by using a second harmonic approach, including stronger motion encoding gradients, shorter radio frequency pulses and an echo‐planar readout. Scan time was decreased by a factor of ～2 relative to 1.5T by using an EPI readout and a higher density sampling of the phase waveform was used to calculate shear stiffness and viscosity. Localized (small region of interest) and global (whole‐liver region of interest) measurements in normal healthy subjects compared very favorably with previously published results at 1.5T. There was no significant difference between global and localized measures. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Diffusion weighted MRI and transient elastography assessment of liver fibrosis in hepatitis C patients: Validity of non invasive imaging techniques

Objective

Treatment for hepatitis C infection and monitoring of progression were based on degree of fibrosis, which were traditionally diagnosed by liver biopsy but it has many limitations. We aim to evaluate noninvasive imaging methods, so-called diffusion-weighted MRI (DW MRI) and transient elastography [(TE), fibroscan] in diagnosing liver fibrosis in hepatitis C (HCV) patients.

Patients

The Study included 102 hepatitis C patients (62 male) with mean age of 38 ± 5. For all patients liver biopsy was done followed by DW MRI and TE. METAVIR classification system was used for staging liver fibrosis. Data obtained were collected and results of DW MRI and TE were compared with those of histopathology. The diagnostic performance of ADC and TE was determined using areas under receiver operating characteristic (AUROC) curves for significant fibrosis ?F3.

Results

Measuring ADC at different b-values had a significant negative correlation with stage of fibrosis P = 0.001, the best negative correlation at b-value of 700 mm²/s. TE had a significant positive correlation with stage of fibrosis P = 0.005. Both examination showed a significant difference between fibrosis stage <F3 and stages ?F3 with P < 0.00 for ADC measure at each b-value and TE respectively.

Conclusion

This study suggests that DW MRI and TE had favorable comparable results with liver biopsy for the diagnosis of significant liver fibrosis.     

Cross-validation of MR elastography and ultrasound transient elastography in liver stiffness measurement: discrepancy in the results of cirrhotic liver

Purpose:

To evaluate individual differences in liver stiffness measurement using both MR elastography (MRE) and ultrasound transient elastography (UTE) in patients with chronic liver disease.

Materials and Methods:

This study included 80 patients with chronic liver disease who underwent both UTE and MRE. MRE and UTE were performed using a pneumatic driver (60 Hz) and an ultrasound probe with a vibrator (50 Hz), respectively. Liver stiffness data measured using the two techniques (μ_UTE and μ_MRE) were compared with respect to shear modulus. The patients were subdivided into four quartiles on the basis of average of the μ_UTE and μ_MRE values for each patient.

Results:

The analysis of the 4 quartile groups revealed that μ_UTE was significantly higher than μ_MRE in the two most stiff liver groups: μ_UTE versus μ_MRE, 7.5 (1.2) versus 6.0 (0.72) kPa for the group with [μ_UTE + μ_MRE]/2 of 5.6–8.0 kPa; 15.1(4.2) versus 6.7 (1.4) kPa for the group with >8.0 kPa. However, in the least stiff liver group (i.e., the group with [μ_UTE + μ_MRE]/2 < 3.2 kPa), μ_UTE was significantly lower than μ_MRE.

Conclusion:

The shear modulus measured by UTE and MRE are not equivalent, especially in patients with stiff livers. J. Magn. Reson. Imaging 2012;35:607‐610. © 2011 Wiley Periodicals, Inc.     

Assessment of liver viscoelasticity using multifrequency MR elastography

MR elastography (MRE) allows the noninvasive assessment of the viscoelastic properties of human organs based on the organ response to oscillatory shear stress. Shear waves of a given frequency are mechanically introduced and the propagation is imaged by applying motion‐sensitive gradients. An experiment was set up that introduces multifrequency shear waves combined with broadband motion sensitization to extend the dynamic range of MRE from one given frequency to, in this study, four different frequencies. With this approach, multiple wave images corresponding to the four driving frequencies are simultaneously acquired and can be evaluated with regard to the dispersion of the complex modulus over the respective frequency. A viscoelastic model based on two shear moduli and one viscosity parameter was used to reproduce the experimental wave speed and wave damping dispersion. The technique was applied in eight healthy volunteers and eight patients with biopsy‐proven high‐grade liver fibrosis (grade 3–4). Fibrotic liver had a significantly higher (P < 0.01) viscosity (14.4 ± 6.6 Pa · s) and elastic moduli (2.91 ± 0.84 kPa; 4.83 ± 1.77 kPa) than the viscosity (7.3 ± 2.3 Pa · s) and elastic moduli (1.16 ± 0.28 kPa; 1.97 ± 0.30 kPa) of normal volunteers. Multifrequency MRE is well suited for the noninvasive differentiation of normal and fibrotic liver as it allows the measurement of rheologic material properties. Magn Reson Med 60:373–379, 2008. © 2008 Wiley‐Liss, Inc.     

Cross‐validation of magnetic resonance elastography and ultrasound‐based transient elastography: A preliminary phantom study

Purpose:

To cross‐validate two recent noninvasive elastographic techniques, ultrasound‐based transient elastography (UTE) and magnetic resonance elastography (MRE). As potential alternatives to liver biopsy, UTE and MRE are undergoing clinical investigations for liver fibrosis diagnosis and liver disease management around the world. These two techniques use tissue stiffness as a marker for disease state and it is important to do a cross‐validation study of both elastographic techniques to determine the consistency with which the two techniques can measure the mechanical properties of materials.

Materials and Methods:

In this study, 19 well‐characterized phantoms with a range of stiffness values were measured by two clinical devices (a Fibroscan and an MRE system based respectively on the UTE and MRE techniques) successively with the operators double‐blinded.

Results:

Statistical analysis showed that the correlation coefficient was r² = 0.93 between MRE and UTE, and there was no evidence of a systematic difference between them within the range of stiffnesses examined.

Conclusion:

These two noninvasive methods, MRE and UTE, provide clinicians with important new options for improving patient care regarding liver diseases in terms of the diagnosis, prognosis, and monitoring of fibrosis progression, as well for evaluating the efficacy of treatment. J. Magn. Reson. Imaging 2009;30:1145–1150. © 2009 Wiley‐Liss, Inc.     

Diffusion-weighted MRI versus transient elastography in quantification of liver fibrosis in patients with chronic cholestatic liver diseases

Purpose

To evaluate the diagnostic value of diffusion-weighted magnetic resonance imaging (DWMRI) and transient elastography (TE) in quantification of liver fibrosis in patients with chronic cholestatic liver diseases.

Materials and methods

Forty-five patients underwent DWMRI, TE, and liver biopsy for staging of liver fibrosis. Apparent diffusion coefficient (ADC) was calculated for six locations in the liver for combination of five diffusion sensitivity values b = 0, 50, 200, 400 and 800 s/mm². A receiver operating characteristic (ROC) analysis was performed to determine the diagnostic performance of DWMRI and TE. Segmental ADC variations were evaluated by means of coefficient of variation.

Results

The mean ADCs (×10⁻³ mm²/s; b = 0–800 s/mm²) were significantly different at stage F1 versus F ≥ 2 (p < 0.05) and F2 versus F4. However, no significant difference was found between F2 and F3. For prediction of F ≥ 2 and F ≥ 3 areas under the ROC curves were 0.868 and 0.906 for DWMRI, and 0.966 and 0.960 for TE, respectively. The sensitivity and specificity were 90.9% and 89.3% for F ≥ 2 (ADC ≤ 1.65), and 92.3% and 92.1% for F ≥ 3 (ADC ≤ 1.63). Segmental ADC variation was lowest for F4 (CV = 9.54 ± 6.3%).

Conclusion

DWMRI and TE could be used for assessment of liver fibrosis with TE having higher diagnostic accuracy and DWMRI providing insight into liver fibrosis distribution.     

Myocardial fibrosis of left ventricle: magnetic resonance imaging in noncompaction

This report describes a 24-year-old female with left ventricular noncompaction. Cardiovascular magnetic resonance (CMR) imaging demonstrated the characteristic features of noncompaction. We were also able to noninvasively document the presence and extent of myocardial fibrosis depicted on myocardial delayed enhancement (MDE). Magnetic resonance imaging can be performed simply and give much information about the morphologic and tissue characteristics of left ventricular wall in noncompaction. In particular, MDE imaging is useful to demonstrate the associated myocardial scaring that may result in heart failure and arrhythmia.