Journal reading radiology.ppt

8/10/2019 Journal reading radiology.ppt

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P E M B I M B I N G : D R . A . M U N I R , S P . R A D .

P R E S E N T A N : A N D H I K A H A D I W .

1 1 0 2 0 1 0 0 2 0

F K Y A R S I

K E P A N I T E R A A N K L I N I K B A G I A N I L M UR A D I O L O G I

Ultrasound in Chronic Liver Disease

(J. F. Gerstenmaier & R. N. Gibson)

Journal Reading


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Abstract

Background

With the high prevalence of diffuse liver disease there

is a strong clinical need for noninvasive detection andgrading of fibrosis and steatosis as well as detection of

complications.


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Results

Fibrosis can be detected and staged with reasonable

accuracy using Transient Elastography and AcousticRadiation Force Imaging. Newer elastographytechniques are emerging that are undergoing

validation and may further improve accuracy.

Ultrasound grading of hepatic steatosiscurrently is predominantly qualitative.


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Conclusion

A summary of methods including B-mode,

Doppler, contrast-enhanced ultrasound and various elastography techniques, and their current

performance in assessing the liver, is provided.


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INTRODUCTION

US : major role in the diagnosis and management ofchronic liver diseases

Purpose : to summarise the range of US techniques

now available and to provide some perspectiveontheir current and potential future value,


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The Clinical Challenge Fibrosis andSteatosis Grading and Staging

Hepatic fibrosis is a response to chronic liver injuryand a process that tends to progress to cirrhosis andend-stage liver disease

five stages, e.g. the METAVIR (F0) = normal connective tissue

(F1) = fibrous portal expansion

(F2) = periportal or scanty porto-portal septa

(F3) = fibrous septa with architectural

(F4) = cirrhosis.


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Macrovesicular steatosis of the liver can be gradedS0S3 based on percent of hepatocytes in the biopsyinvolved

S0 : none; S1 is up to 33 %;

S2 is 3366 %;

S3 is >66 %)

The grade of steatosis is one parameter in the stagingfor NASH


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Dixon macrovesicular grading :

grades 04 assigned to

75 %


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Biopsy : gold standard in fibrosis assesment

Weakness :

has a complication rate of approximately 1 % have a high rate of sampling error in patients with

diffuse parenchymal liver diseases

A typical specimen volume taken at core biopsyrepresents only 1/50,000 of liver volume


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Ultrasound Modalities

B mode ultrasound

Fatty Liver Disease

Diffuse fatty infiltration results in increased

echogenicity of the liver when compared to otherorgans such as the renal cortex (Fig. 1).


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Fig. 1 B-mode ultrasound of liver and right kidney. Diffuse

fatty infiltration. The liver is of markedly increased echo

intensity relative to the renal cortex, indicative of severe

steatosis


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Qualitative grading : 0 = normal.

Grade 1 (mild) = diffuse slight increase in fine echoesin the hepatic parenchyma with normal visualisationof the diaphragm and intrahepatic vessel borders.

Grade 2 (moderate) = a moderate diffuse increase infine echoes with slightly impaired visualisation of the

intrahepatic vessels and diaphragm. Grade 3 (marked) = marked increase in fine echoes

with poor or no visualisation of the intrahepaticvessel borders,diaphragm and posterior portion of

the right lobe of the liver


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Effectiveness of steatosis detection can be increasedby quantification of liver brightness. Thesonographic hepatorenal index (SHRI) is based on

comparison between liver and kidney brightness:

An image including both liver and kidney isrequired, typically showing segment 6 of the liver

and the upper pole of the right kidney.


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Regions of interest (ROI) of an appropriate size(>400 pixels) are selected in the liver parenchyma.The SHRI is the mean liver brightness divided by themean renal cortex brightness (Fig. 2).

The authors found that SHRI cutoff points of 1.21,1.28 and 2.15 yielded 100 % sensitivity for the

diagnoses of steatosis greater than 5 %, 25 % and 50%, respectively,with a specificity greater than 70 %.


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In summary, the SHRI appears to be an appealingtechnique for diagnosis and quantification of hepaticsteatosis.


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Doppler ultrasound

Doppler ultrasound can measure hepatic blood flow.In the past, several investigations of the utility ofDoppler ultrasound as a noninvasive method ofassessing the degree of hepatic fibrosis have beenmade


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The main role of Doppler ultrasound is theassessment of portal venous hypertension as acomplication of cirrhosi and hepatofugal flow in theportal vein are both specific signs and have a highpositive predictive value for the presence of portalhypertension


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Recanalisation of the paraumbilical vein as shown byvenous Doppler signal in the ligamentum teres. Thisis sensitive and specific for the presence of portal

venous hypertension


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Contrast-enhanced ultrasound

Contrast-enhanced ultrasound (CEUS) usesmicrobubbles as kinetic tracers. By measuring

vascular transit times and parenchymalenhancement, the severity of liver disease can beassessed. In patients with cirrhosis, the transit timesof microbubbles are shortened


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Elastography

There is a correlation between hepatic parenchymalpathology and liver stiffness. As a surrogate markerof fibrosis and cirrhosis, the measurement of liverstiffness forms the basis of elastography.

Elasticity is the tendency of solid materials to returnto their original shape after being deformed by a

force applied and removed. In elastography, suchforce is coupled with a system that measures thedeformities caused by the force


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Ultrasound elastography techniques :

Transient elastography (FibroScan),

Acoustic radiation force impulse imaging (ARFI),

shear wave mode elastography Strain elastography


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Transient elastography

Based on Hookes law : the force required tocompress or extend a spring is proportional to thedistance compressed or extended

Transient elastography (TE) is the technique usedwith the FibroScan ultrasound unit

The stiffer the tissue is, the higher the speed of waveprogression


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Acoustic force radiation impulse

A 5mm 10mmregion of interest (ROI) cursor isplaced during real-time B-mode scanning. Thetechnique was termed shear wave elastography at apoint (pSWE) given the small size of the ROI cursor

The tissue in the ROI is excited with a short duration(262 s) fixed frequency (2.67 MHz) ultrasound

pulse to displace tissue locally.


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Two-dimensional shear wave elastography

The shear wave elastography (SWE) Aixplorerultrasound system generates shear waves in tissuefrom the acoustic radiation force obtained withfocussed ultrasound pulses.

Serial pulses create plane shear waves that propagatetransversely.

Plane wave imaging is used to determine the speed

of shear waves. Tissue elasticity is related to shear wave velocity and

expressed in kPa


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Range of colours is from red (soft tissue) to blue(hard tissue).

On a frozen image, mean and standard deviation of

tissue stiffness can be displayed within a set ROI


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S i l h ( l i i


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Strain elastography (real-time tissueelastography)

Strain elastography is technically distinct fromtransient elastography, using a conventionalultrasound transducer to collect signals with and

without distortion of tissue

While initially used for the assessment of focallesions in the pancreas, prostate, breast and thyroid,

this method is now also being used for liver fibrosis.


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Conclusion

Conventional B-mode ultrasound remains a valuabletool in first-line screening of patients with chronicliver disease, supplemented by portal venousDoppler studies.

Elastographic methods of TE and ARFI have nowbeen validated for the assessment of fibrosis, other

elastographic technologies are emerging and arelikely to become more widely applied

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