Numerical modeling for non-invasive imaging using ultrahigh frequency electromagnetic waves

Nondestructive evaluation (NDE) is an important field in industry that has a wide range of applications to guarantee the quality of new products, maintain the safety of working equipment and perform medical diagnosis. In this thesis work, we are presenting two noninvasive NDE imaging techniques, microwave-induced thermoacoustic imaging for breast cancer diagnosis and structured light 3D characterization for gas pipes internal surface reconstruction. Thermoacoustic imaging is an emerging imaging technique that combines both high contrast of microwave imaging and sub-millimeter resolution of ultrasound imaging. This imaging technique is highly affected by acoustic and electrical properties of the imaged target. Other important factors are the properties of the excitation source such as its electric field pattern and pulse duration. This thesis developed a numerical model to simulate the signal generation of near-field microwave-induced thermoacoustic imaging. The study simulates both the electromagnetic interaction of microwaves with the imaged object, as well as the generation of acoustic signals and their propagation from the target to the transducers. The study also investigates the effect of different design parameters that determine the intensity and frequency of generated acoustic signals for imaging. Various parameters are investigated, such as target's electrical properties, microwave frequencies, and the microwave source pulse width. Another major contribution of this thesis work is on data reconstruction for optical NDE methods. Structured light has been widely used to create 3D models of objects. In this thesis, we propose to use this technique to characterize and analyze damage and defects inside natural gas v pipelines. The study aims to develop and implement 3D reconstruction algorithms to characterize the defects and deformations while the data are acquired using the optical sensors developed at CU LEAP group. The study develops a reconstruction algorithm for single laser ring laser ring scanner and evaluates its performance. The.