Ultrasonic tomography using curved ray paths obtained by wave propagation simulations on a massively parallel computer

摘要

Current ultrasonic tomography methods do not properly handle cases involving large refraction, mode conversion, strong scattering, or finite apertures. To account for these different effects, a method has been developed utilizing a very efficient code to model elastic wave propagation on a massively parallel computer. The computation also determines in a detailed way the ray paths of first arrival acoustic energy through solids even with strong scatterers. By using these fast parallel forward and ray path codes as part of an iterative tomography algorithm (ART), a major improvement is obtained over using straight-line ray paths. In addition, the wave propagation approach permits improved tomographic reconstructions in cases having large changes in the refractive index (10), where traditional ray-tracing methods, based on the geometrical acoustics approximation, become numerically unstable. The entire tomography computation required is immense, but is feasible because the code is highly parallel and is implemented on a parallel supercomputer.