RIU 324 Lecture Notes - Lecture 31: Fundamental Frequency, Sound, Rarefaction

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

Document Summary

Harmonic reading: at any time segment, the net signal for a particular element is a combination of the echo-induced signals from well-defined locations (fig 9-26). Contribution are restricted to those locations in which the total path length for the transmit pulse and the returning echo are the same. Since crystals across the array make several measurements of the same spatial point during each transmission, a two-dimensional image of reflectors can be formed. The reconstruction time is short (5-10 milliseconds), and thus high frame rates are now possible (100-200 frames per second). Equation 9-1 shows that the acoustic velocity at each point over the waveform is modulated by the particle velocity. Further, this contribution to wave velocity also depends on the medium via the ratio b/2a. during the compressional phase particle velocity is positive, and the speed of sound increases during this portion of the wave cycle.