Rationale and Objectives
Magnetic resonance elastography (MRE) can noninvasively measure the stiffness of liver tissue and display this information in anatomic maps. Magnetic resonance imaging (MRI) guidance has not previously been used to biopsy segments of heterogeneous stiffness identified on MRE. Dedicated study of MRE in post–liver transplant patients is also limited. In this study, the ability of real-time MRI to guide biopsies of segments of the liver with different MRE stiffness values in the same post-transplant patient was assessed.
Materials and Methods
MRE was performed in 9 consecutive posttransplant patients with history of hepatitis C. Segments of highest and lower stiffness on MRE served as targets for subsequent real-time MRI-guided biopsy using T2-weighted imaging. The ability of MRI-guided biopsy to successfully obtain tissue specimens was assessed. The Wilcoxon signed-rank test was used to compare mean stiffness differences for highest and lower MRE stiffness segments, with α = 0.05.
Results
MRI guidance allowed successful sampling of liver tissue for all (18/18) biopsies. There was a statistically significant difference in mean MRE stiffness values between highest (4.61 ± 1.99 kPa) and lower stiffness (3.03 ± 1.75 kPa) ( P = .0039) segments biopsied in the 9 posttransplant patients.
Conclusion
Real-time MRI can guide biopsy in patients after liver transplantation based on MRE stiffness values. This study supports the use of MRI guidance to sample tissue based on functional information.
Hepatitis C virus (HCV) infection afflicts an estimated 123 million people worldwide and is the leading indication for liver transplantation in the United States . Posttransplant recurrence of HCV is virtually universal . Although more than 25% of HCV-positive patients develop fibrosis and ultimately cirrhosis within 5 years of transplant, it is unknown which specific patients will progress . Posttransplant patients undergo recurrent liver biopsies because HCV therapy is reserved for biopsy-proven recurrence . Sampling error is a major limitation of biopsies because of the heterogeneity of early fibrosis and the small amount of tissue obtained per biopsy (0.002% of the overall liver volume) . The use of imaging guidance to target the stiffest segments of liver is one potential solution to this limitation but requires a method that can simultaneously identify the local liver stiffness and guide needle placement.
Magnetic resonance imaging (MRI) guidance can be used to biopsy liver lesions with diagnostic yields similar to computed tomography (CT) and ultrasound (US) guidance methods . MRI guidance has not previously been used to biopsy focal segments of heterogeneous stiffness identified on magnetic resonance elastography (MRE). MRE, pioneered by Dr. Richard Ehman , has emerged as a powerful method to noninvasively measure the liver’s stiffness, which in turn correlates with the presence of generalized liver fibrosis in patients with chronic liver disease . Such information is displayed as color-coded, quantitative stiffness maps. Because higher stiffness readings are associated with increased fibrosis, stiffness maps enable distinction between normal and fibrotic livers. A cutoff value of 2.93 kPa for mean liver stiffness is 98% sensitive and 99% specific to distinguish normal from fibrotic livers in patients without liver transplants . There is emerging data on MRE in posttransplant patients, a high-risk population that stands to benefit greatly from the technique . Furthermore, it is unclear whether MRI-guidance can be used to biopsy regions of heterogeneous liver stiffness seen in posttransplant patients.
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Materials and methods
Clinical Setting and Patients
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MRI Unit
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MRE
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MRE Analysis
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MRI-Guided Biopsy Technique
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Liver Pathology Analysis
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Data and Statistical Analysis
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Results
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Table 1
Patient Demographics, MRE Findings, Fibrosis Score, and Inflammation Score
Patient Age Sex Overall MRE Stiffness (kPa) Couinaud Liver Segment Segmental MRE Stiffness (kPa) Fibrosis Score (METAVIR Scale) Inflammation Score (Graded From 0–4) 1 55 Female 2.34 8 1.83 F0 1 1 4 2.85 F0 1 2 65 Female 2.34 7 2.30 F0 1 2 4 4.20 F0 1 3 54 Male 2.22 8 1.55 F0 1 3 4 2.96 F0 1 4 59 Male 2.96 8 3.35 F0 1 4 4 7.35 F0 1 5 60 Male 6.80 4 7.30 F0 0 5 8 7.60 F0 0 6 58 Male 2.00 8 1.73 F0 1 6 4 2.07 F0 1 7 42 Male 3.40 5 3.46 F0 1 7 4 5.24 F0 1 8 54 Male 3.01 5 2.67 F0 0 8 4 5.69 F0 0 9 59 Male 3.20 5 3.11 F0 0 9 4 3.52 F0 0
MRE, magnetic resonance elastography.
Table 2
Preprocedural Liver Function Tests
Test Mean and Range AST (U/L) 45.9 (16–74) ALT (U/L) 46.6 (13–97) Total bilirubin (g/dL) 1.24 (0.6–3.3) Alkaline phosphatase (U/L) 89.3 (43–141) Albumin (g/dL) 3.97 (3.5–4.3) Platelets (k/μL) 155 (79–225) INR 0.978 (0.9–1.1)
ALT, alanine aminotransferase; AST, aspartate aminotransferase; INR, international normalized ratio.
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Discussion
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Acknowledgments
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