Choice of moving target for a string phantom: I. Measurement of filament backscatter characteristics.

Detected back-scattered Doppler signal level was measured from the following filaments: braided silk filaments, nylon and O-ring rubber. The detected signal level fell with time from the point of immersion by 45-85% for the silk filaments and by 50% for the nylon, but did not change for the O-ring rubber. For all of the silk filaments there were strong backscatter peaks at Doppler angles varying from 55-80 degrees for a transmit frequency of 4 MHz. Nylon demonstrated a large peak at 90 degrees, whereas there was no large backscatter peak present for O-ring rubber. The paper concludes that the use of braided filaments for the assessment of the accuracy of Doppler estimated velocity may lead to errors if the angular backscattered peak is very strong. O-ring rubber may be suitable for the testing of Doppler-estimated velocity.