A comprehensive numerical procedure for high-intensity focused ultrasound ablation of breast tumour on an anatomically realistic breast phantom

Abstract

High-Intensity Focused Ultrasound (HIFU) as a promising and impactful modality for breast tumor ablation, entails the precise focalization of high-intensity ultrasonic waves onto the tumor site, culminating in the generation of extreme heat, thus ablation of malignant tissues. In this paper, a comprehensive three-dimensional (3D) Finite Element Method (FEM)-based numerical procedure is introduced, which provides exceptional capacity for simulating the intricate multiphysics phenomena associated with HIFU. Furthermore, the application of numerical procedures to an anatomically realistic breast phantom (ARBP) has not been explored before. The integrity of the present numerical procedure has been established through rigorous validation, incorporating comparative assessments with previous two-dimensional (2D) simulations and empirical data. For ARBP ablation, the administration of a 0.1 MPa pressure input pulse at a frequency of 1.5 MHz, sustained at the focal point for 10 seconds, manifests an ensuing temperature elevation to 80°C. It is noteworthy that, in contrast, the prior 2D simulation using a 2D phantom geometry reached just 72°C temperature under the identical treatment regimen, underscoring the insufficiency of 2D models, ascribed to their inherent limitations in spatially representing acoustic energy, which compromises their overall effectiveness. To underscore the versatility of this numerical platform, a simulation of a more clinically relevant HIFU therapy procedure has been conducted. This scenario involves the repositioning of the ultrasound focal point to three separate lesions, each spaced at 3 mm intervals, with ultrasound exposure durations of 6 seconds each and a 5-second interval for movement between focal points. This approach resulted in a more uniform high-temperature distribution at different areas of the tumour, leading to the ablation of almost all parts of the tumour, including its verges. In the end, the effects of different abnormal tissue shapes are investigated briefly as well. For solid mass tumors, 67.67% was successfully ablated with one lesion, while rim-enhancing tumors showed only 34.48% ablation and non-mass enhancement tumors exhibited 20.32% ablation, underscoring the need for multiple lesions and tailored treatment plans for more complex cases.

Fig 1. A schematic of the HIFU ablation process for the treatment of a breast tumour.

Fig 2

Computational domain details; (a) 3D visualization of the entire geometry considered; (b) middle cross-section view of the geometry; (c) FCG tissue; (d) transitional tissue; (e) fatty tissue, muscle, and tumour; (f) all tissues within each other as the ARBP; (g) boundary conditions considered in pressure acoustics physics; (h) boundary conditions considered in bioheat transfer physics; (i) considered cut planes that pass through the centre of the tumour.

Fig 3. Grid independency test for each physics.

(a) “pressure acoustics” physics, (b) “bioheat transfer” physics.

Fig 4. Optimum grid generation considered for each physics.

“Pressure acoustics” physics: (a) whole geometry, (b) sliced magnified model. “Bioheat transfer” physics: (c) whole geometry, (d) sliced magnified model.

Fig 5

Validation study results; (a) comparison of the maximum total acoustic pressure obtained from our simulation and Montienthong & Rattanadecho’s simulation; (b) comparison of the maximum sound intensity magnitude obtained from our simulation and Montienthong & Rattanadecho’s simulation; (c) comparison of our simulation and Montienthong & Rattanadecho simulation plots of the temperature distribution in the focal point during the time; (d) comparison between Li et al.’s and our results for the volume of the heated necrotic element induced by HIFU at 2 cm focal depth and acoustic intensity of 25.4E+3 Wcm^-2 in an in-vitro bovine liver.

Fig 6

Total acoustic pressure field, (a) cut plane 1, (b) cut plane 2, (c) cut plane 3, (d). 3D view.

Fig 7

Sound intensity magnitude, (a) cut plane 1, (b) cut plane 2, (c) cut plane 3, (d). 3D view.

Fig 8. Total acoustic pressure distribution along lines passes through the tumour’s centre in different directions.

(a) x-direction, (b) y-direction, (c) z-direction.

Fig 9. Sound intensity magnitude distribution along lines passes through the tumour’s centre in different directions.

(a) x-direction, (b) y-direction, (c) z-direction.

Fig 10

Distribution of temperature after 10 seconds, (a) cut plane 1, (b) cut plane 2, (c) cut plane 3, (d) 3D view.

Fig 11. Temperature distribution after 10 s along lines passes through the tumour’s centre in different directions.

(a) x-direction, (b) y-direction, (c) z-direction.

Fig 12

Distribution of necrotic tissue fraction after 100 s of the ablation process, (a) cut surface 1, (b) cut surface 2, (c) cut surface 3, (d) 3D view.

Fig 13. Fraction of necrotic tissue after 100 s ablation process along lines pass through tumour’s centre in different directions.

(a) x-direction, (b) y-direction, (c) z-direction.

Fig 14. Temperature and fraction of necrotic tissue at the tumour’s centre during ablation time.

(a) Temperature change, (b) fraction of necrotic tissue.

Fig 15

(a-c) sound intensity magnitude in the cut plane 1 during each of the three lesion processes, (d-f) temperate distribution in the cut plane 1 at the end of each lesion process, (g-j) fraction of necrotic tissue distribution in the cut plane 1 at the end of each lesion process and after the whole ablation process.

Fig 16. Temperature and the fraction of necrotic tissue after 6 s, 17 s, 28 s, and 100 s along lines pass through the tumour’s centre in different directions.

(a and b) y-direction, (c and d) x-direction, (e and f) z-direction.

Fig 17

(a & b) Geometries of abnormal tissues: linear non-mass enhancement and rim-enhancing mass, respectively, (c & d) sound intensity magnitude in the cut plane 1 for each of the cases, (e & f) temperate distribution in the cut plane 1 after 10 seconds for each of the cases, (g & h) fraction of necrotic tissue distribution in the cut plane 1 after 100 s ablation process for each of the cases.

Fig 18. 3D distribution of the fraction of necrotic tissue after 100 s of ablation for different tumor types.

(a & b) whole tumor geometry and almost undamaged tissue (fraction of necrotic tissue < 0.7) for the solid mass case. (c & d) Whole tumor geometry and almost undamaged tissue for the rim-enhancing mass case. (e & f) Whole tumor geometry and almost undamaged tissue for the linear non-mass enhancement case.