MR elastography for noninvasive assessment of hepatic fibrosis: experience from a tertiary center in Asia

Purpose:

To determine the sensitivity and specificity of MR elastography (MRE) in the staging of hepatic fibrosis (HF) using histopathology as the reference standard in an Asian population.

Materials and Methods:

MRE was performed on 55 patients with chronic liver diseases or biliary diseases and on 5 living related liver donors (48 men and 12 women; mean age, 55.7 years). MRE was performed with modified, phase‐contrast, gradient‐echo sequences, and the mean stiffness values were measured on the elastograms in kilopascals(kPa). Receiver operating characteristic curve analysis was performed to determine the cutoff value and accuracy of MRE for staging HF. Histopathologic staging of HF according to the METAVIR scoring system served as the reference.

Results:

Liver stiffness increased systematically along with the fibrosis stage. With a shear stiffness cutoff value of 3.05 kPa, the predicted sensitivity and specificity for differentiating significant liver fibrosis (≥ F2) from mild fibrosis (F1) were 89.7% and 87.1%, respectively. In addition, MRE was able to discriminate between patients with severe fibrosis (F3) and those with liver cirrhosis (sensitivity, 100%; specificity, 92.2%), with a shear stiffness cutoff value of 5.32 kPa.

Conclusion:

MRE could be a promising, noninvasive technique with excellent diagnostic accuracy for detecting significant HF and liver cirrhosis. J. Magn. Reson. Imaging 2011. © 2011 Wiley Periodicals, 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.     

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.     

MR elastography of the in vivo abdominal aorta: a feasibility study for comparing aortic stiffness between hypertensives and normotensives

Purpose:

To demonstrate feasibility of using MR elastography (MRE) to identify hypertensive changes in the abdominal aorta when compared with normotensives based on the stiffness measurements.

Materials and Methods:

MRE was performed on eight volunteers (four normotensives and four hypertensives) to measure the effective stiffness of the abdominal aorta. MRE wave images are directionally filtered and phase gradient analysis was performed to determine the stiffness of the aorta. Student's t‐test was performed to determine significant difference in stiffness measurements between normotensives and hypertensives.

Results:

The normotensive group demonstrated a mean abdominal aortic stiffness of 3.7 ± 0.8 kPa, while the controlled‐hypertensive demonstrated a mean abdominal aortic stiffness of 9.3 ± 1.9 kPa. MRE effective stiffness of abdominal aorta in hypertensives was significantly greater than that of normotensives with p = 0.02.

Conclusion:

Feasibility of in vivo aortic MRE is demonstrated. Hypertensives have significantly higher aortic stiffness assessed through MRE than normotensives. J. Magn. Reson. Imaging 2012;35:582‐586. © 2011 Wiley Periodicals, Inc.     

Assessment of portal hypertension and high-risk oesophageal varices with liver and spleen three-dimensional multifrequency MR elastography in liver cirrhosis

Objective

To assess the value of the liver and spleen viscoelastic parameters at multifrequency MR elastography to determine the degree of portal hypertension and presence of high-risk oesophageal varices in patients with cirrhosis.

Methods

From January to September 2012, 36 consecutive patients with cirrhosis evaluated for transplantation were prospectively included. All patients underwent hepatic venous pressure gradient (HVPG) measurements and endoscopy to assess oesophageal varices. Multifrequency MR elastography was performed within the liver and spleen. The shear, storage and loss moduli were calculated and compared to the HVPG with Spearman coefficients and multiple regressions. Patients with and without severe portal hypertension and high-risk varices were compared with Mann–Whitney tests, logistic regression and ROC analysis.

Results

The liver storage and loss moduli and the spleen shear, storage and loss moduli correlated with the HVPG. At multiple regression, only the liver and the spleen loss modulus correlated with the HVPG (r = 0.44, p = 0.017, and r = 0.57, p = 0.002, respectively). The spleen loss modulus was the best parameter for identifying patients with severe portal hypertension (p = 0.019, AUROC = 0.81) or high-risk varices (p = 0.042, AUROC = 0.93).

Conclusions

The spleen loss modulus appears to be the best parameter for identifying patients with severe portal hypertension or high-risk varices.

Key points

1. Noninvasive HVPG assessment can be performed with liver and spleen MR elastography 2. The spleen loss modulus enables the detection of high-risk oesophageal varices 3. The spleen loss modulus enables the detection of severe portal hypertension     

Noninvasive Assessment of Hepatic Fibrosis in Patients with Chronic Hepatitis B Viral Infection Using Magnetic Resonance Elastography

Objective

To evaluate the diagnostic performance of magnetic resonance elastography (MRE) for staging hepatic fibrosis in patients with chronic hepatitis B virus (HBV) infection.

Materials and Methods

Patients with chronic HBV infection who were suspected of having focal or diffuse liver diseases (n = 195) and living donor candidates (n = 166) underwent MRE as part of the routine liver MRI examination. We measured liver stiffness (LS) values on quantitative shear stiffness maps. The technical success rate of MRE was then determined. Liver cell necroinflammatory activity and fibrosis were assessed using histopathologic examinations as the reference. Areas under the receiver operating characteristic curve (Az) were calculated in order to predict the liver fibrosis stage.

Results

The technical success rate of MRE was 92.5% (334/361). The causes of technical failure were poor wave propagation (n = 12), severe respiratory motion (n = 3), or the presence of iron deposits in the liver (n = 12). The mean LS values, as measured by MRE, increased significantly along with an increase in the fibrosis stage (r = 0.901, p < 0.001); however, the mean LS values did not increase significantly along with the degree of necroinflammatory activity. The cutoff values of LS for ≥ F1, ≥ F2, ≥ F3, and F4 were 2.45 kPa, 2.69 kPa, 3.0 kPa, and 3.94 kPa, respectively, and with Az values of 0.987-0.988.

Conclusion

MRE has a high technical success rate and excellent diagnostic accuracy for staging hepatic fibrosis in patients with chronic HBV infection.     

Test-retest repeatability of MR elastography for noninvasive liver fibrosis assessment in hepatitis C

Purpose:

To conduct a rigorous evaluation of the repeatability of liver stiffness assessed by MR elastography (MRE) in healthy and hepatitis‐C‐infected subjects.

Materials and Methods:

A biopsy‐correlated repeatability study using four‐slice MRE was conducted in five healthy and four HCV‐infected subjects. Subjects were scanned twice on day 1 and after 7–14 days. Each slice was acquired during a 14‐s breath‐hold with a commercially available acquisition technique (MR‐Touch, GE Healthcare). Results were analyzed by two independent analysts.

Results:

The intraclass correlation coefficient (ICC) was 0.85 (90% confidence interval [CI]: 0.71 to 0.98) for the between‐scan average of maximum stiffness within each slice and 0.88 (90% CI: 0.78 to 0.99) for the average of mean stiffness within each slice for the primary analyst. For both analysts, the average of the mean liver stiffness within each slice was highly reproducible with ICC of 0.93 and 0.94. Within‐subject coefficients of variation ranged from 6.07% to 10.78% for HCV+ and healthy subjects.

Conclusion:

MRE is a highly reproducible modality for assessing liver stiffness in HCV patients and healthy subjects and can discriminate between moderate fibrosis and healthy liver. MRE is a promising modality for noninvasive assessment of liver fibrosis (Clinicaltrials.gov identifier: NCT00896233). J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Decreased brain stiffness in Alzheimer's disease determined by magnetic resonance elastography

Purpose:

To test patient acceptance and reproducibility of the 3D magnetic resonance elastography (MRE) brain exam using a soft vibration source, and to determine if MRE could noninvasively measure a change in the elastic properties of the brain parenchyma due to Alzheimer's disease (AD).

Materials and Methods:

MRE exams were performed using an accelerated spin‐echo echo planar imaging (EPI) pulse sequence and stiffness was calculated with a 3D direct inversion algorithm. Reproducibility of the technique was assessed in 10 male volunteers, who each underwent four MRE exams separated into two imaging sessions. The effect of AD on brain stiffness was assessed in 28 volunteers, 7 with probable AD, 14 age‐ and gender‐matched PIB‐negative (Pittsburgh Compound B, a PET amyloid imaging ligand) cognitively normal controls (CN?), and 7 age‐ and gender‐matched PIB‐positive cognitively normal controls (CN+).

Results:

The median stiffness of the 10 volunteers was 3.07 kPa with a range of 0.40 kPa. The median and maximum coefficients of variation for these volunteers were 1.71% and 3.07%. The median stiffness of the 14 CN? subjects was 2.37 kPa (0.44 kPa range) compared to 2.32 kPa (0.49 kPa range) within the CN+ group and 2.20 kPa (0.33 kPa range) within the AD group. A significant difference was found between the three groups (P = 0.0055, Kruskal–Wallis one‐way analysis of variance). Both the CN+ and CN? groups were significantly different from the AD group.

Conclusion:

3D MRE of the brain can be performed reproducibly and demonstrates significantly reduced brain tissue stiffness in patients with AD. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.

     

Development and application of magnetic resonance elastography of the normal and pathological thyroid gland in vivo

Purpose:

To noninvasively assess the shear stiffness of the thyroid gland in vivo in order to determine whether magnetic resonance elastography (MRE) might hold clinical utility in the diagnosis of thyroid disease.

Materials and Methods:

Quantitative parametric images of thyroid stiffness in normal volunteers and patients were produced and quantitative stiffness values measured. Average gland stiffness was determined by region of interest analysis of the parametric images. This technique was used to assess stiffness of the thyroid in normal individuals (n = 12), patients with Hashimoto's thyroiditis (HT; n = 5), and patients with a solitary benign (n = 8) or malignant (n = 2) thyroid nodule.

Results:

Mean shear modulus of normal thyroid glands was 1.9 ± 0.6 kPa at 100 Hz and 1.3 ± 0.5 kPa at 80 Hz, while that of HT glands was 2.8 ± 0.6 kPa and 1.8 ± 0.6 kPa at 80 Hz, respectively (P = 0.004 at 100 Hz). Elastographic parameters could not differentiate benign from malignant thyroid nodules in these small sample sizes.

Conclusion:

We developed a method for the application of MRE to the study of thyroid gland pathology. The results show that the HT gland can be differentiated from normal thyroid. The clinical utility of this imaging modality in the diagnosis and management of thyroid disease awaits further study. J. Magn. Reson. Imaging 2009;30:1151–1154. © 2009 Wiley‐Liss, 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.

     

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.     

Novel technique for MR elastography of the prostate using a modified standard endorectal coil as actuator

Purpose:

To present a novel method for MR elastography (MRE) of the prostate at 3 Tesla using a modified endorectal imaging coil.

Materials and Methods:

A commercial endorectal coil was modified to dynamically generate mechanical stress (contraction and dilation) in a prostate phantom with embedded phantom “lesions” (6 mm diameter) and in a porcine model. Resulting tissue displacements were measured with a motion‐sensitive EPI sequence at actuation frequencies of 50–200 Hz. Maps of shear modulus G were calculated from the measured phase‐difference shear‐wave patterns.

Results:

In the G maps of the phantom, “lesions” were easily discernible against the background. The average G values of regions of interest placed in the “lesion” (8.2 ± 1.9 kPa) were much higher than those in the background (3.6 ± 1.4 kPa) but systematically lower than values reported by the vendor (13.0 ± 1.0 and 6.7 ± 0.7 kPa, respectively). In the porcine model, shear waves could be generated and measured shear moduli were substantially different for muscle (7.1 ± 2.0 kPa), prostate (3.0 ± 1.4 kPa), and bulbourethral gland (5.6 ± 1.9 kPa).

Conclusion:

An endorectal MRE concept is technically feasible. The presented technique will allow for simultaneous MRE and MRI acquisitions using a commercial base device with minor, MR‐conditional modifications. The diagnostic value needs to be determined in further trials. J. Magn. Reson. Imaging 2013;37:1480–1485. © 2012 Wiley Periodicals, Inc.     

MR elastography of human lung parenchyma: technical development, theoretical modeling and in vivo validation

Purpose:

To develop a novel MR‐based method for visualizing the elastic properties of human lung parenchyma in vivo and to evaluate the ability of this method to resolve differences in parenchymal stiffness at different respiration states in healthy volunteers.

Materials and Methods:

A spin‐echo MR Elastography (MRE) pulse sequence was developed to provide both high shear wave motion sensitivity and short TE for improved visualization of lung parenchyma. The improved motion sensitivity of this approach was modeled and tested with phantom experiments. In vivo testing was then performed on 10 healthy volunteers at the respiratory states of residual volume (RV) and total lung capacity (TLC).

Results:

Shear wave propagation was visualized within the lungs of all volunteers and was processed to provide parenchymal shear stiffness maps for all 10 subjects. Density corrected stiffness values at TLC (1.83 ± 0.22 kPa) were higher than those at the RV (1.14 ± 0.14 kPa) with the difference being statistically significant (P < 0.0001).

Conclusion:

¹H‐based MR elastography can noninvasively measure the shear stiffness of human lung parenchyma in vivo and can quantitate the change in shear stiffness due to respiration. The values obtained were consistent with previously reported in vitro assessments of cadaver lungs. Further work is required to increase the flexibility of the current acquisition and to investigate the clinical potential of lung MRE. J. Magn. Reson. Imaging 2011;33:1351–1361. © 2011 Wiley‐Liss, Inc.     

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.     

Feasibility of quantifying the mechanical properties of lung parenchyma in a small‐animal model using 1H magnetic resonance elastography (MRE)

Purpose

To evaluate the feasibility of spatially resolving the shear modulus of lung parenchyma using conventional ¹H magnetic resonance elastography (MRE) imaging techniques in a small animal model.

Materials and Methods

A 10‐cm diameter transmit‐receive radiofrequency coil was modified to include a specimen stage, an MRE pneumatic drum driver, and needle system. MRE was performed on 10 female Sprague–Dawley rats using a ¹H spin‐echo based MRE imaging sequence with a field of view of 7 cm and slice thickness of 5 mm. Air‐filled lungs were imaged at transpulmonary inflation pressures of 5, 10, and 15 cm H₂O while fluid‐filled lungs were imaged after infusion of 4 mL of normal saline.

Results

The average shear modulus of air‐filled lungs was 0.840 ± 0.0524 kPa, 1.07 ± 0.114 kPa and 1.30 ± 0.118 kPa at 5, 10, and 15 cm H₂O, respectively. Analysis of variance indicated that these population means were statistically significantly different from one another (F‐value = 26.279, P = 0.00004). The shear modulus of the fluid‐filled lungs was 1.65 ± 0.360 kPa.

Conclusion

It is feasible to perform lung MRE in small animals using conventional MR imaging technologies. J. Magn. Reson. Imaging 2009;29:838–845. © 2009 Wiley‐Liss, Inc.     

MR elastography of the liver at 3.0 T in diagnosing liver fibrosis grades; preliminary clinical experience

Objectives

To clarify the usefulness of 3.0-T MR elastography (MRE) in diagnosing the histological grades of liver fibrosis using preliminary clinical data.

Materials and methods

Between November 2012 and March 2014, MRE was applied to all patients who underwent liver MR study at a 3.0-T clinical unit. Among them, those who had pathological evaluation of liver tissue within 3 months from MR examinations were retrospectively recruited, and the liver stiffness measured by MRE was correlated with histological results. Institutional review board approved this study, waiving informed consent.

Results

There were 70 patients who met the inclusion criteria. Liver stiffness showed significant correlation with the pathological grades of liver fibrosis (rho?=?0.89, p?<?0.0001, Spearman’s rank correlation). Areas under the receiver operating characteristic curve were 0.93, 0.95, 0.99 and 0.95 for fibrosis score greater than or equal to F1, F2, F3 and F4, with cut-off values of 3.13, 3.85, 4.28 and 5.38 kPa, respectively. Multivariate analysis suggested that grades of necroinflammation also affected liver stiffness, but to a significantly lesser degree as compared to fibrosis.

Conclusions

3.0-T clinical MRE was suggested to be sufficiently useful in assessing the grades of liver fibrosis.

Key Points

? MR elastography may help clinicians assess patients with chronic liver diseases ? Usefulness of 3.0-T MR elastography has rarely been reported ? Measured liver stiffness correlated well with the histological grades of liver fibrosis ? Measured liver stiffness was also affected by necroinflammation, but to a lesser degree ? 3.0-T MRE could be a non-invasive alternative to liver biopsy

     

In vivo validation of 4D flow MRI for assessing the hemodynamics of portal hypertension

Purpose:

To implement and validate in vivo radial 4D flow MRI for quantification of blood flow in the hepatic arterial, portal venous, and splanchnic vasculature of healthy volunteers and patients with portal hypertension.

Materials and Methods:

Seventeen patients with portal hypertension and seven subjects with no liver disease were included in this Health Insurance Portability and Accountability Act (HIPAA)‐compliant and Institutional Review Board (IRB)‐approved study. Exams were conducted at 3T using a 32‐channel body coil with large volumetric coverage and 1.4 mm isotropic true spatial resolution. Using postprocessing software, cut‐planes orthogonal to vessels were used to quantify flow (L/min) in the hepatic and splanchnic vasculature.

Results:

Flow quantification was successful in all cases. Portal vein and supraceliac aorta flow demonstrated high variability among patients. Measurements were validated indirectly using internal consistency at three different locations within the portal vein (error = 4.2 ± 3.9%) and conservation of mass at the portal confluence (error = 5.9 ± 2.5%) and portal bifurcation (error = 5.8 ± 3.1%).

Conclusion:

This work demonstrates the feasibility of radial 4D flow MRI to quantify flow in the hepatic and splanchnic vasculature. Flow results agreed well with data reported in the literature, and conservation of mass provided indirect validation of flow quantification. Flow in patients with portal hypertensions demonstrated high variability, with patterns and magnitude consistent with the hyperdynamic state that commonly occurs in portal hypertension. J. Magn. Reson. Imaging 2013;37:1100–1108. © 2012 Wiley Periodicals, Inc.     

Magnetic resonance elastography for the detection and staging of liver fibrosis in chronic hepatitis B

Objectives

We measured the accuracy of magnetic resonance elastography (MRE) for the detection and staging of liver fibrosis in chronic hepatitis B (CHB) and compared it with serum fibrosis markers.

Methods

Prospective comparison of MRE and routine serum fibrosis markers, namely serum alanine aminotransferase (ALT), serum aspartate aminotransferase (AST), ALT/AST ratio (AAR), AST to platelet ratio index (APRI) and prothrombin index (PI), was performed in 63 consecutive CHB patients who underwent MRE and histological confirmation of liver fibrosis within a 6-month interval. Diagnostic performance of MRE and serum markers for staging fibrosis (≥F1), significant fibrosis (≥F2), advanced fibrosis (≥F3) and cirrhosis (F4) was compared.

Results

The study group comprised 63 patients (19 female; mean age?±?SD, 50?±?11.9 years). MRE (ρ?=?0.94, P?<?0.0001), APRI (ρ?=?0.42, P?=?0.0006), PI (ρ?=?0.42, P?=?0.0006) and AST (ρ?=?0.28, P?=?0.028) results correlated significantly with fibrosis stage. MRE was significantly more accurate than serum fibrosis markers for the detection of significant fibrosis (0.99 vs. 0.55–0.73) and cirrhosis (0.98 vs. 0.53–0.77). Sensitivity, specificity, positive predictive and negative predictive values for MRE for significant fibrosis and cirrhosis were 97.4 %, 100 %, 100 % and 96 %, and 100 %, 95.2 %, 91.3 % and 100 %, respectively.

Conclusion

MRE is an accurate non-invasive technique for the detection and staging of liver fibrosis in CHB.

Key Points

? Magnetic resonance elastography is accurate for liver fibrosis detection and staging. ? MR elastography is more accurate than serum tests for staging liver fibrosis. ? MR elastography can potentially replace liver biopsy in chronic hepatitis B.     

Cisterna chyli in patients with portal hypertension: evaluation with MR imaging

Purpose:

To evaluate the difference in the caliber of cisterna chyli between patients with and without portal hypertension on magnetic resonance imaging (MRI) and to assess the alteration of the caliber of cisterna chyli related to contraction waves during serial T2‐weighted MRI.

Materials and Methods:

This study included 177 patients with and without portal hypertension who underwent two sets of T2‐weighted MRI. MR images were evaluated for the visibility of cisterna chyli, the difference in the diameter of cisterna chyli between two patients groups, and the alteration in the diameter of cisterna chyli during serial T2‐weighted MRI.

Results:

The mean maximal diameter of cisterna chyli in patients with portal hypertension (4.97 ± 1.87 mm, range; 2.5–13.1 mm) was significantly larger (P < 0.001) than that in patients without portal hypertension (3.37 ± 1.25 mm, range; 1.5–6.8 mm). In 132 patients with visible cisterna chyli and portal hypertension, 25 (19%) patients had a positive caliber change of cisterna chyli of more than 2 mm between two sets of T2‐weighted MR images.

Conclusion:

The dilatation of cisterna chyli can be demonstrated at MRI in patients with portal hypertension. Additionally, the positive caliber change of cisterna chyli related to contraction waves was observed in subsets of patients during serial T2‐weighted MRI. J. Magn. Reson. Imaging 2012;35:624‐628. © 2011 Wiley Periodicals, Inc.     

Non-invasive evaluation of liver fibrosis: a comparison of ultrasound-based transient elastography and MR elastography in patients with viral hepatitis B and C

Objective

To compare the diagnostic accuracy of TE and MRE and establish cutoff levels and diagnostic strategies for both techniques, enabling selection of patients for liver biopsy.

Methods

One hundred three patients with chronic hepatitis B or C and liver biopsy were prospectively included. Areas under curves (AUROC) were compared for TE and MRE for METAVIR fibrosis grade?≥?F2 and ≥F3. We defined cutoff values for selection of patients with F0–F1 (sensitivity >95 %) and for significant fibrosis F2–F4 (specificity >95 %).

Results

Following exclusions, 85 patients were analysed (65 CHB, 19 CHC, 1 co-infected). Fibrosis stages were F0 (n?=?3), F1 (n?=?53), F2 (n?=?15), F3 (n?=?8) and F4 (n?=?6). TE and MRE accuracy were comparable [AUROC_TE?≥?F2: 0.914 (95 % CI: 0.857–0.972) vs. AUROC_MRE?≥?F2: 0.909 (0.840–0.977), P?=?0.89; AUROC_TE?≥?F3: 0.895 (0.816–0.974) vs. AUROC_MRE?≥?F3: 0.928 (0.874–0.982), P?=?0.42]. Cutoff values of <5.2 and ≥8.9 kPa (TE) and <1.66 and ≥2.18 kPa (MRE) diagnosed 64 % and 66 % of patients correctly as F0–F1 or F2–F4. A conditional strategy in inconclusive test results increased diagnostic yield to 80 %.

Conclusion

TE and MRE have comparable accuracy for detecting significant fibrosis, which was reliably detected or excluded in two-thirds of patients. A conditional strategy further increased diagnostic yield to 80 %.

Key Points

? Both ultrasound-based transient elastography and magnetic resonance elastography can assess hepatic fibrosis. ? Both have comparable accuracy for detecting liver fibrosis in viral hepatitis. ? The individual techniques reliably detect or exclude significant liver fibrosis in 66 %. ? A conditional strategy for inconclusive findings increases the number of correct diagnoses.