TE Enriched Sample (E)

Summary 85 • Tools: piezoelectric transducer (device for both producing and detecting ultrasound) • Emission of ultrasound original shape changing voltage ultrasound emitted – + + – 3. Ultrasound is emitted 1. Voltage is applied across the crystal " crystal changes its shape 2. Voltage is removed " crystal restores its shape through a series of oscillations 3. Ultrasound signals are detected through measuring pd 1. Crystal changes its shape by ultrasound 2. Voltage is developed across the crystal • Detection of ultrasound original shape – + + + + – – + – – – + + + + – – + – – • Types: • A-scan ( a mplitude scan): Amplitude of echoes against time • B-scan ( b rightness scan): Stronger intensity , brighter dots amplitude brightness 1 2 3 4 5 • 2-D B-scan Send out multiple beams of ultrasound over a surface When traces are joined, a planar image is formed. • Choosing frequency ranges for scanning 1. Resolution incident pulse lateral axial reflected pulse s Axial resolution: higher for shorter pulse duration Lateral resolution: higher for higher frequency 2. Penetration: higher frequency suffers higher attenuation • Advantages and limitations: see p. 72 Sample © United Prime Educational Publishing (HK) Limited, Pearson Education Asia Limited 2023 All rights reserved; no part of this publication may be reproduced, photocopied, recorded or otherwise, without the prior written permission of the Publishers.