RIU 324 Lecture Notes - Lecture 18: Frame Rate, Yellow Arrow, Medical Ultrasound

• School: GVSU
• Department: Radiation and Imaging - Ultrasound
• Course: RIU 324
• Professor: Angela Malone

Document Summary

Also called duplex since echoes are processed for b-mode (2d) and. Prone to aliasing due to inadequate sampling. Operator defines a location (axis and depth)- sample gate. A train of pulses (8-20) are used to calculate doppler shift (aka ensemble or packet size) Operator must define the angle of incidence and flow. Sample and hold circuit calculates the freq. shift by interrogating the pulse train. Gate location is defined by time delay and duration. Select exact location where velocities are measured. Sample volume (gate) placed and system calculates time of flight to interrogate exact location. Range resolution, range specificity, freedom from range ambiguity artifact. Inaccurate measurement of high velocity signals due to aliasing. Doppler shift frequency determination requires a longer pulse duration that b-mode. Received frequencies are almost the same as transmitted frequencies, detection of small changes requires more sampling time.