The need to examine materials and system components without compromising their integrity has spurred the development of nondestructive evaluation (NDE) techniques. NDE can range from a simple visual inspection of a surface to the measurement of physical properties of materials. The most prominent methods of NDE currently in use include ultrasonic testing, eddy current examination, x-ray radiography, neutron radiography, magnetic flux leakage testing, and liquid penetrant testing. Many of these fields are well developed in terms of their abilities to detect and characterize flaws within a sample. When nondestructive testing (NDT) was first introduced, the practice consisted of comparison between signals and standards. The standards were generated from a defined set of machined samples incorporated with desired flaws. The testing method was applied to these samples to yield reference signals. Thus when NDT was applied to a component, the resulting signal was compared to the reference signals to determine whether this component was acceptable in a go - no go sense. This type of testing was just a comparison of signals to set points. There was little extraction of the flaw information present in the signal, and the NDT personnel performing the testing often did not understand the physics underlying the generation of the signals.