Liver Fibrosis
Figure 2: Relationship Between Liver Stiffness Measurement and Fibrosis Stage
The Turkey–Kramer method
* * *
2.2 2.4 2.6
Masson trichrome stain
1.0 1.2 1.4 1.6 1.8 2.0
* NS **
decrease as hepatic fibrosis develops. Furthermore, diagnoses based on these ADC values have equivalent diagnostic capability as other non-invasive liver fibrosis measurement methods.34,35
MR
elastography, which vibrates biological tissue from outside to generate shear waves and images those shear waves, has been developed by Muthupillai et al.36
reports of correlations with liver fibrosis.37
and there have been subsequent Although similar
non-invasive liver fibrosis measurement is possible with MRI, compared with methods using ultrasonic waves, it is more complex.
(n = 40)
F0-1 (n=8)
F2 (n=12)
*p<0.0001 **p=0.0072
SWV = shear wave velocity.
Figure 3: Receiver Operating Characteristic Curve for the Diagnosis of F4 by ARFI, APRI, Forns’ Index and Platelet Count
1.0 F3 (n=10) F4 (n=10) 0.8 0.6 0.4 0.2
ARFI imaging technology involves the mechanical excitation of tissue using short-duration acoustic pulses (push pulses) in a region of interest (ROI) chosen by the examiner, producing shear waves that spread away from the ROI, perpendicular to the acoustic push pulse, generating localised, micron-scale displacements in the tissue. ARFI imaging was carried out with a curved array at 4.5 MHz for B-mode imaging. The examination was performed in the right lobe of the liver, through the intercostal space, at the same site as TE measurement. An area where liver tissue was <5 cm thick and free of large blood vessels was chosen. The measurement depth was 2 cm below the liver capsule to standardise the examination (see Figure 1). SWV was measured 10 times in succession using ARFI imaging. Mean SWV excluding outliers was used to measure liver stiffness. Relationships between mean SWV measured using ARFI imaging and clinical diagnosis, sex, age, BMI and the results of liver function tests were studied. In addition, the time required to perform ARFI imaging was recorded for all patients. Biochemical tests (i.e. Plt,
T.Bil, albumin [Alb], AST, ALT, GGT, total cholesterol [TC], prothrombin time [PT], HA and type IV collagen [IV-C]) were carried out using routine laboratory methods for all patients on the day of ARFI imaging. APRI and Forns’ index were calculated for each patient from the results of haematological examination and age.13,16,38
Acoustic Radiation Force Impulse Imaging We evaluated the validity, accuracy and flexibility of the ARFI imaging method in CLD. Forty patients provided informed consent and underwent abdominal ultrasound, haematological examination and ARFI imaging between April and December 2009 at Iwate Medical University Hospital. Ten patients had liver cirrhosis and 30 had chronic hepatitis; all patients had HCV infection. Histopathological studies were conducted in all patients. Liver biopsy was performed percutaneously using a 14-G biopsy needle. Histological diagnosis of the liver was made by two highly experienced pathologists. Staging of liver fibrosis was evaluated according to the METAVIR classification.5
Clinical 0 0 0.2 0.4
VTTQ APRI
Forn’s index Platelet count
AUROC 0.915 0.832 0.821 0.778
APRI = aspartate to platelet ratio index; ARFI = acoustic radiation force impulse; AUROC = area under the receiver operating characteristic; VTTQ = virtual touch tissue quantification.
gadolinium and superparamagnetic iron oxide particles are also being developed. It has also been reported that apparent diffusion coefficient (ADC) values obtained using diffusion-weighted MRI
266 0.6 1 – Specificity 0.8 0.1
The mean time required to perform ARFI imaging was 4.9 ± 2.7 minutes, and the actual operation was very easy as well. Mean SWV in all patients was 1.56 ± 0.89 m/s. No significant correlations with sex, age or BMI were observed. Mean SWV in each fibrosis stage was 1.10 ± 0.22 m/s for F0-1, 1.27 ± 0.52 m/s for F2, 1.62 ± 0.79 m/s for F3 and 2.36 ± 1.11 m/s for F4 (see Figure 2). SWV was significantly higher for F4 than for F0-3 (p<0.0001) and for F3 than for F2 (p=0.0072), although no significant difference was observed between groups for F2. A steady stepwise increase in elasticity correlated with staging of liver fibrosis (r=0.9772; p=0.002). SWV correlated significantly with Plt (r=-0.6541; p<0.0001), Alb (r=-0.6541; p<0.0001),
T.Bil (r=0.5712; p=0.0002), AST (r=0.7362; p<0.0001), ALT (r=0.4791; p=0.0017), PT (r=-0.6139; p<0.0001), TC (r=-0.5881; p=0.0002), HA (r=0.5551;
EUROPEAN GASTROENTEROLOGY & HEPATOLOGY REVIEW
diagnostic abilities for F0-3 and F4 were compared for four modalities using receiver operating characteristic (ROC) curves: Forns’ index, APRI, Plt and SWV.
Sensitivity
SWV (m/s)
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