In vivo quantification of motion in liver parenchyma and its application in shistosomiasis tissue characterization

摘要

Abstract: Schistosomiasis is a major problem in Egypt, despite anactive control program it is estimated to exist inabout 1/3 of the population. Deposition of lessfunctioning fibrous tissues in the liver is the majorcontributory factor to the hepatic pathology. Fibroustissues consist of a complex array of connective matrixmaterial and a variety of collagen isotopes. As aresult of an increased stromal density (collagencontent), the parenchyma became more ectogenic and lesselastic (hard). In this study we investigated theeffect of cardiac mechanical impulses from the heartand aorta on the kinetics of the liver parenchyma.Under conditions of controlled patient movements andsuspended respiration, a 30 frame per second of 588$MUL 512 ultrasound images (cineloop, 32 pels per cm)are captured from an aTL ultrasound machine thendigitized. The image acquisition is triggered by the Rwave of the ECG of the patient. The motion that has aforced oscillation form in the liver parenchyma isquantified by tracking of small box (20 - 30 pels) in16 directions for all the successive 30 frames. Thetracking was done using block matching techniques (themax correlation between boxes in time, frequencydomains, and the minimum SAD (sum absolute difference)between boxes). The motion is quantified for manyregions at different positions within the liverparenchyma for 80 cases of variable degrees ofschisto., cirrhotic livers, and for normal livers. Thevelocity of the tissue is calculated from thedisplacement (quantified motion), time between frames,and the scan time for the ultrasound scanner. We foundthat the motion in liver parenchyma is small in theorder of very few millimeters, and the attenuation ofthe mechanical wave for one ECG cycle is higher in theschisto. and cirrhotic livers than in the normal ones.Finally quantification of motion in liver parenchymadue to cardiac impulses under controlled limb movementand respiration may be of value in the characterizationof schisto. (elasticity based not scattering based).This value could be used together with the widevarieties of quantitative tissue characterizationparameters for pathology differentiation and fordifferentiating subclasses of cirrhosis as well as thedetermination of the extent of bilharzial affection.!30