Abstract
Therapeutic ultrasound is a promising non-invasive method for inducing various beneficial biological effects in the human body. In cancer treatment applications, high-power ultrasound is focused at a target tissue volume to ablate the malignant tumour. The success of the procedure depends on the ability to accurately focus ultrasound and destroy the target tissue volume through coagulative necrosis whilst preserving the surrounding healthy tissue. Patient-specific treatment planning strategies are therefore being developed to increase the efficacy of such therapies, while reducing any damage to healthy tissue. These strategies require to use high-performance computing methods to solve ultrasound wave propagation in the body quickly and accurately. For realistic clinical scenarios, all numerical methods which employ volumetric meshes require several hours or days to solve the full-wave propagation on a computer cluster. The boundary element method (BEM) is an efficient approach for modelling the wave field because only the boundaries of the hard and soft tissue regions require discretisation. This paper presents a multiple-domain BEM formulation with a novel preconditioner for solving the Helmholtz transmission problem (HTP). This new formulation is efficient at high-frequencies and where high-contrast materials are present. Numerical experiments are performed to solve the HTP in multiple domains comprising: (i) human ribs, an idealised abdominal fat layer and liver tissue, (ii) a human kidney with a perinephric fat layer, exposed to the acoustic field generated by a high-intensity focused ultrasound (HIFU) array transducer. The time required to solve the equations associated with these problems on a single workstation is of the order of minutes. These results demonstrate the great potential of this new BEM formulation for accurately and quickly solving ultrasound wave propagation problems in large anatomical domains which is essential for developing treatment planning strategies.
Highlights
High-intensity focused ultrasound (HIFU) therapy is a procedure which uses high-intensity ultrasound to thermally ablate a localised region of diseased tissue, leaving the surrounding healthy tissue intact
The number of surface elements required by boundary element method (BEM) to represent the wave propagation is of (k2) which results in the memory footprint of (k4), as Galerkin discretisation of the boundary integral operators results in dense matrices
The results presented here are calculated for an incident field generated by a HIFU array transducer
Summary
High-intensity focused ultrasound (HIFU) therapy is a procedure which uses high-intensity ultrasound to thermally ablate a localised region of diseased tissue, leaving the surrounding healthy tissue intact. We present a new fast multiple-domain transmission BEM model to compute both the scattered and transmitted ultrasonic fields in softtissue and bone This formulation employs a novel preconditioner which is developed for high-frequency high-contrast problems. The scattered field was calculated for the following computational domains: i) an idealised layer of abdominal fat, human ribs and liver tissue, and ii) a human kidney model and a perinephric fat layer, see Section 3 In both scenarios, the incident field is generated by a spherical section array transducer operating at the frequency of 1MHz. the suitability and limitations of this BEM scheme for use in HIFU treatment planning are discussed
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