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Research Papers

Thermal Assessment of Ablation Limit of Subsurface Tumor During Focused Ultrasound and Laser Heating

[+] Author and Article Information
Arka Bhowmik

School of Mechanical,
Materials, and Energy Engineering,
Indian Institute of Technology Ropar,
Rupnagar, Punjab 140001, India
e-mail: arkabhowmik@yahoo.co.uk

Ramjee Repaka

School of Mechanical, Materials,
and Energy Engineering,
Indian Institute of Technology Ropar,
Rupnagar, Punjab 140001, India
e-mail: ramjee.repaka@gmail.com

Subhash C. Mishra

Department of Mechanical Engineering,
Indian Institute of Technology Guwahati,
Guwahati, Assam 781039, India
e-mail: scm_iitg@yahoo.com

Kunal Mitra

Department of Biomedical Engineering,
Florida Institute of Technology,
Melbourne, FL 32901-6975
e-mail: kmitra@fit.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received April 30, 2014; final manuscript received January 18, 2015; published online November 11, 2015. Assoc. Editor: Chakravarthy Balaji.

J. Thermal Sci. Eng. Appl 8(1), 011012 (Nov 11, 2015) (12 pages) Paper No: TSEA-14-1105; doi: 10.1115/1.4030731 History: Received April 30, 2014

Theoretical study on the thermal assessment of two types of tumor ablation techniques, viz., focused laser for ablating skin lesion and focused high-frequency ultrasound for ablating breast tumor has been presented in this article. Estimation of temperature rise and the induced thermal damage in the skin using laser heating have been done by integrating the bioheat transfer, the laser-light attenuation, and the thermal damage models. Further, ultrasound heating of deep seated tumor within the breast has been implemented to estimate the temperature rise and the induced thermal damage by combining the bioheat transfer, the vascularized, the pressure wave, and the thermal damage models. The theoretical models for skin, breast, and blood vessels have been constructed based on the anatomical details, thermophysical, optical, and acoustic properties available in the literature. The study indicates that the focused ultrasound heating can selectively raise the temperature of the tissue above the ablation limit sparing the surrounding healthy ones and imposes sufficient thermal damage to the entire tumor volume in a relatively short exposure time and longer cooling period. Whereas the laser-based heating would lead to collateral damage of the surrounding tissues and demands longer exposure time in order to achieve complete heating of the tumor volume. Heating of tumor at a uniform rate is a major issue in both the cases, and in the course of heating, the entire tumor volume in certain regions may experience irregular necrosis rate and char formation. Based on the comprehensive modeling efforts, the study further suggests two important thermal ablation criteria for complete and uniform heating of tumor volume at relatively short exposure time.

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Figures

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Fig. 1

Schematic diagrams: (a) working principle of laser/ultrasound ablation, (b) focused laser ablation of skin tumor, and (c) focused ultrasound ablation of breast tumor

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Fig. 2

(a) Mesh convergence plot and (b) solver convergence plots for laser ablation of skin model

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Fig. 3

Mesh and solver convergence plots for ultrasound ablation of breast model: (a) mesh and (b) solver convergence plots for acoustic solver, (c) mesh and (d) solver convergence plots for blood flow solver, and (e) mesh and (f) solver convergence plots for bioheat solver

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Fig. 4

(a) Transient thermal response of human skin and cancerous tumor, variation of temperature along (b) axial direction and (c) radial direction, the variation of (d) thermal damage (Ω) and (e) CETD (s) with necrosis time (τ), for focused C-W laser power (=1.5 J s−1), D0 = 1.2 mm, DFD = 0.02, mm, and FD = 0.2 mm

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Fig. 5

(a) Transient thermal response of human skin and cancerous tumor; the variation of temperature along (b) axial direction and (c) radial direction; the variation of (d) thermal damage (Ω) and (e) CETD with necrosis time (τ), for pulse laser having power P (=12 J s−1), pulse width (tp = 2.5 ms), number of pulses (N = 133), D0 = 1.2 mm, DFD = 0.02 mm, and focused at FD (FD = 0.2 mm)

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Fig. 6

(a) Thermal profile at different times (viz., t = 0.008 s, 0.02 s, 1.0 s, and 20 s) for focused C-W laser having power, P ( = 1.5 J s−1), spot diameter, D0 = 1.2 mm at z = 0, and spot diameter, DFD = 0.02 mm at FD = 0.2 mm, (b) thermal profile at different times (viz., t = 0.008 s, 0.02 s, 1.0 s, and 2.0 s) for focused pulse laser having power, P (=12 J s−1), pulse width, tp (=2.5 ms), number of pulses, N (=133), spot diameter at z = 0, D0 (= 1.2 mm), and spot diameter at FD = 0.2 mm, DFD (=0.02 mm)

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Fig. 7

Comparison between the measured temperature [38] and predicted temperature (from FEM simulation) at the core of the fibroadenoma lesion (having diameter dl = 0.7 cm) within the breast due to focused streaming frequency of 1.5 MHz and sonication duration of 10 s

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Fig. 8

Acoustic and thermal response of breast with malignant lesion for 1.5 MHz streaming frequency and 10 s sonication. The variation of absolute pressure in (a) axial direction and (b) radial direction; (c) schematic diagram representing different measurement locations; variation of breast temperature profiles at different locations (d) with time, (e) along the axial direction, (f) along the radial direction, and (g) variation of thermal damage (Ω) quantity of tumor with necrosis time (τ).

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Fig. 9

(a) Blood velocity and pressure fluctuation with time for three cardiac cycles denoted by 1, 2, and 3, (b) fully developed velocity profile at different locations of blood vessel, and (c) velocity and pressure magnitude plots of blood within the vessel

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Fig. 10

Acoustic and thermal field within the breast for 1.5 MHz streaming frequency and 10 s sonication time. (a) Absolute pressure within the breast without vessel, (b) absolute pressure within the breast with vessel, temperature, and induced damage field due to acoustic heating of vascularized breast tumor at (c) t = 5 s, (d) t = 10 s, (e) t = 20 s, and (f) t = 100 s.

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