Nondestructive Testing (NDT) is a generic term designating all methods which may be used to detect flaws and discontinuities in materials, parts and structures or to evaluate the properties of materials, without causing damage to the object. There are a number of different NDT techniques: to name a few, Radiographic Testing (RT), Ultrasonic Testing (UT), Acoustic Emission (AE), Magnetic Particle Testing (MPT), Penetrant Testing (PT), Eddy Current Testing (ECT), Leakage Testing (LT), and Visual Testing (VT). New techniques such as optical methods are also developed to meet the increasingly more strict industrial needs. Besides NDT, terms such as Nondestructive Evaluation (NDE), Nondestructive Inspection (NDI) and Nondestructive Characterization (NDC) are used when appropriate, and they are often exchangeable with each other.