Power Doppler Imaging (PDI) is a diagnostic ultrasound technique used to assess blood flow within the body. Although PDI is an industry-standard term, it has several synonyms that mean the same thing. In some cases, different brands of ultrasound machines may use a different synonym for PDI. Some of the synonyms for PDI include "colour Doppler," "energy Doppler," "harmonic imaging," and "velocity Doppler." These terms all refer to the same imaging technology used to assess blood flow and tissue perfusion. While some terms may be more commonly used in certain settings or by particular brands of imaging equipment, all of these synonyms should be understood to refer to the same diagnostic technique.