The first topic discussed in this module is Doppler system testing. In order to perform Doppler testing, specialized testing equipment has been developed including Doppler flow phantoms, string phantoms, and vibrating plate phantoms. We will then discuss image performance testing. As with Doppler, many different imaging phantoms have been designed to test imaging performance including the parameters of detail resolution, contrast resolution, sensitivity, image distortion, and measurement accuracy. In the third part of this module, we learn about statistical test validation. In this section, we learn the statistical parameters used to compare various aspects of a clinical test we want to validate against a gold standard test. This statistical information will also prove very useful for labs undergoing laboratory accreditation.