ARFI(acoustic radiation force impulse) is a new technology that insonates tissues with an acoustic push pulse and detects the degree of deformation of tissue,
thereby enabling real-time measurement of liver stiffness.
Fig. 1: Acoustic radiation force impulse elastography using RFA
References: S2000 diagnostric ultrasound system, Simens, USA
The advantage of ARFI technology over transient elastography is that measurements can be performed with software integrated into a conventional ultrasound examination.
Moreover,
ARFI can be done in patinets with ascites,
such as in this case,
because the region of interest can be set under real time ultrasound guidance,
which is not possible with TE.
Liver elastography using US methods such as TE and ARFI was first developed for the purpose of determing the extent of the fibrosis in chronic liver disease.
Several reports have demonstrated that the diagnostic accuracy of SWV measurement using ARFI was comparable to thaht obtained by TE in the prediction of severe fibrosis and cirrhosis.
Fig. 2: Method:
1.Right lobe of liver through an intercostal space
2.Decubitus position with breath hold
Region of interest:
1.Placed at right lobe, depth of 3-5cm
2.Careful not to include vessels and biliary structures in ROI
Measurement: Among the total of 5 trials for each patients, we excluded maximum and minimun value and calculated the mean value of 3 trials.
References: Department of Radiology, Dong-A university hospital/ Korea 2013
However specificity is impared by cholestasis,
inflammation or edema in or comibned aucte hepatitis.
The mechanism by which acute hepatic injury increases liver stiffness has not yet ben elucidated.
Although liver fibrosis is knwon to be the main factor underlying the increased liver siffness in chronic liver disease,
other histopathological changes were recently reorted to be implied in aucte liver injury.
The histopathological features of acute hepatitis are extensive infiltration with inflammatory lymphocytes along with swelling of hepatocytes and apoptosis without fibrosis.
Fig. 3: Histopatholgic feature in acute hepatitis with underlying chronic hepatitis.
(A) Hematoxylin and eosin stain (×400). The portal region shows lymphocytic infiltration. (B) HSA(×400) shows hepatocystes with inflammatory cells.
References: Department of Radiology, Dong-A univerisyt hospital, Pusan, Korea, 2013
The objective of this study was to evaluate the serial change of shear wave velocites because of the chronic hepatitis or cirrhosis to ultrasound image and biochemical activity.