CHOICE OF MOVING TARGET FOR A STRING PHANTOM .1. MEASUREMENT OF FILAMENT BACKSCATTER CHARACTERISTICS

Detected back-scattered Doppler signal level was measured from the fol lowing filaments: braided silk filaments, nylon and O-ring rubber. The detected signal level fell with time from the point of immersion by 4 5-85% for the silk filaments and by 50% for the nylon, but did not cha nge for the O-ring rubber. For all of the silk filaments there were st rong backscatter peaks at Doppler angles varying from 55-80 degrees fo r a transmit frequency of 4 MHz. Nylon demonstrated a large peak at 90 degrees, whereas there was no large backscatter peak present for O-ri ng rubber. The paper concludes that the use of braided filaments for t he assessment of the accuracy of Doppler estimated velocity may lead t o errors if the angular backscattered peak is very strong. O-ring rubb er may be suitable for the testing of Doppler-estimated velocity.