TE Enriched Sample (E)

Non-ionizing Medical Imaging 2 74 7. A transducer sends an ultrasound pulse into medium A as shown. medium A boundary 1 boundary 2 medium B medium A transducer 1 cm The table below shows some properties of media A and B . medium density / kg m −3 ultrasound wave speed / m s −1 A 950 1500 B 1050 1600 (a) Briefly explain how a transducer can emit and detect ultrasound. (b) The transducer receives two echoes from boundaries 1 and 2 separately. Find the time lapse between them. (c) Find the intensity reflection coefficients when the ultrasound pulse is incident on boundaries 1 and 2, respectively. 8. An A-scan is performed on an organ. In the CRO trace shown, signals 1 and 2 are due to the echoes received from the front and rear surfaces of the organ, respectively. 1 2 0.02 ms (a) State two factors that determine the intensity of the echoes. (b) What is the thickness of the organ? The ultrasound speed in the organ is 1500 m s −1 . 1.25 × 10 −5 s 0.006 74 0.075 m 9. The photo shows the A-scan of the right eye of a girl. The axial diameter of the eyeball is found to be 20.75 mm. Take the ultrasound speed as 1550 m s −1 . (a) The data for the lens is missing. (i) From the A-scan image, estimate the thickness of the lens. (ii) What is the time lapse between the reception of echoes from the front surface and the back surface of the lens? (b) The photo below shows the A-scan of the left eye of the same girl. In fact, one of the eyes of the girl is short-sighted. Is it the left or the right? Explain briefly. 10. The photo shows a B-scan image of a kidney. (a) There are bright and dark areas in the image. How are they formed? (b) What should be the frequency range of the ultrasound for diagnosing the above organ? (c) Suggest two advantages of using an ultrasound scan to diagnose kidneys. 4 mm 5.16 × 10 −6 s Non-ionizing, inexpensive 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.