Photoacoustic Wave Propagation Simulations Using the FDTD Method with Berenger’s Perfectly Matched Layers
Journal
SPIE International Symposium on Biomedical Optics
Date Issued
2008-01
Author(s)
Abstract
Several photoacoustic (PA) techniques, such as photoacoustic imaging, spectroscopy, and parameter sensing, measure quantities that are closely related to optical absorption, position detection, and laser irradiation parameters. The photoacoustic waves in biomedical applications are usually generated by elastic thermal expansion, which has advantages of nondestructiveness and relatively high conversion efficiency from optical to acoustic energy. Most investigations describe this process using a heuristic approximation, which is invalid when the underlying assumptions are not met. This study developed a numerical solution of the general photoacoustic generation equations involving the heat conduction theorem and the state, continuity, and Navier-Stokes equations in 2.5D axis-symmetric cylindrical coordinates using a finite-difference time-domain (FDTD) scheme. The numerical techniques included staggered grids and Berenger's perfectly matched layers (PMLs), and linear-perturbation analytical solutions were used to validate the simulation results. The numerical results at different detection angles and durations of laser pulses agreed with the theoretical estimates to within an error of 3% in the absolute differences. In addition to accuracy, the flexibility of the FDTD method was demonstrated by simulating a photoacoustic wave in a homogeneous sphere. The performance of Berenger's PMLs was also assessed by comparisons with the traditional first-order Mur's boundary condition. At the edges of the simulation domain, a 10-layer PML medium with polynomial attenuation grading from zero to 5×106 m3/kg/s was designed to reduce the reflection to as low as -60 and -32 dB in the axial and radial directions, respectively. The reflections at the axial and radial boundaries were 32 and 7 dB lower, respectively, for the 10-layer PML absorbing layer than for the first-order Mur's boundary condition.
Subjects
Absorption coefficient; FDTD; Finite-difference time-domain; Photoacoustic signal
SDGs
Other Subjects
Absorption; Absorption spectroscopy; Acoustic waves; Boundary conditions; Convergence of numerical methods; Difference equations; Electromagnetic wave absorption; Energy absorption; Energy conversion; Energy efficiency; Energy resources; Equations of state; Error analysis; Error detection; Finite difference method; Finite difference time domain method; Fluid dynamics; Fluid mechanics; Heat conduction; Imaging techniques; Laser beams; Lasers; Light; Mathematical morphology; Multiphoton processes; Navier Stokes equations; Nonlinear optics; Numerical methods; Optical systems; Optical waveguides; Perturbation techniques; Photoacoustic spectroscopy; Photons; Polynomial approximation; Pulsed laser applications; Pulsed laser deposition; Solutions; Thermal expansion; Thermal spraying; Ultrasonic applications; Ultrasonic imaging; Ultrasonic transmission; Ultrasonics; Waves; (001) parameter; (e ,3e) process; (I ,J) conditions; (R ,S)-symmetric; Acoustic energy (AE); Acousto optics; Analytical solutions; Bio-medical applications; Cylindrical coordinates; Detection angles; FDTD methods; Finite-difference time-domain (FDTD) schemes; first orders; General (CO); Heuristic approximations; High conversion efficiency; laser irradiations; Navier Stokes equations; numerica l results; Numerical - techniques; Numerical solutions; Optical (PET) (OPET); Optical absorption (OA); Perfectly Matched Layer (PML); Perfectly matched layers (PMLs); Photoacoustic (PA) images; Photoacoustic waves; Position detection; simulation domains; simulation results; Staggered grids; thermoacoustics; Photoacoustic effect
Type
conference paper