Evaluation of an iterative reconstruction method for quantitativeelastography

Abstract

This paper describes an inverse reconstruction technique based on a modifiedNewton Raphson iterative scheme and the finite element method, which has beendeveloped for computing the spatial distribution of Young's modulus fromwithin soft tissues. Computer simulations were conducted to determine therelative merits of reconstructing tissue elasticity using knowledge of(a) known displacement boundary conditions (DBC), and (b) known stressboundary conditions (SBC). The results demonstrated that computing Young'smodulus using knowledge of SBC allows accurate quantification of Young'smodulus. However, the quality of the images produced using this reconstructionapproach was dependent on the Young's modulus distribution assumed at thestart of the reconstruction procedure. Computing Young's modulus from knownDBC provided relative estimates of tissue elasticity which, despite thedisadvantage of not being able to accurately quantify Young's modulus, formedimages that were generally superior in quality to those produced using theknown SBC, and were not affected by the trial solution. The results of preliminary experiments on phantoms demonstrated thatthis reconstruction technique is capable in practice of improving the fidelityof tissue elasticity images, reducing the artefacts otherwise present instrain images, and recovering Young's modulus images that possess excellentspatial and contrast resolution.