Physics Mock Questions 2012 - 2013 Medical Ultrasound Imperial College: Part A: 1. Which physical Properties govern the speed of propagation of ultrasound in soft tissue? How is the speed of sound used to determine the origin of a reflected / backscattered signal? Why can the incorrect estimation of the speed of sound in tissue lead to an imaging artefact. (5) Part a. Q. 2 Briefly explain the nature of systematic errors in b mode ultrasound distance measurements? Give an example of systematic error that may occur and how this systematic error may be detected. How may random errors be reduced? (6) Q.3. What does the term contrast resolution refer to, why is it important and what control is it most affected by ( illustrate the effect of the control with a diagram). (4) Q:4: what velocity of blood flow would produce a Doppler shift frequency of 4.5 KHz when insinuated with a 5 MHz pulse St an angle of 45? What PRF would be required to detect this Doppler shift frequency without aliasing ? (5) Q.5: explain with aid of a diagram , the statement the transducer has a -3dB band width of 9 to 5 MHz . (2) Q. 6. Discuss how B mode imaging calliper accuracy can be assessed using a test object , critically evaluating any limitations that may arise. (6) Q.7. Explain the term the term slice thickness . What influences the slice thickness ? How may it affect image quality? (4) Q. 8. A 3 MHz transducer emits a pulse of 2.5 cycles. What would the pulse length in soft tissue be ( in units of distance) ? How will the pulse length change qualititively if the pulse passes through bone? Which property of an ultrasound image is governed by the pulse length? (4) Q.9. Explain the term constructive interference. (2). Q.10. Explain the term mechanical index . Why is it of use to the ultrasound operator? (4) Q.11. Explain the process of analogue to analogue to digital conversion. (2). What impact will the size of the of image memory have on the image. Physics mock questions: part B Q12. Discuss the factors that will govern the proportion of ultrasound energy that will be reflected from a smooth ( planer and specular) interface and received back at the transducer (8). Describe which scanner controls the operator may use to optimise the appearance of an echo on the image (3). Critically evaluate how the reflection produced at such an interface may assist or limit the use of ultrasound in diagnosis (3). With the aid of a diagram , explain how (1) a mirror image artefact and (2) a reverberation artefact are produced . Give examples where these may be seen clinically and describe how they may be overcome . Discuss whether a mirror image artefact will affect colour flow imaging and spectral Doppler (11). Q13. Explain the terms axial and lateral resolution. (3). With the aid of a diagram , name the components of a multielement array transducer. (3). What properties of these components will govern the resolution and sensitivity of the transducer, explaining your answer ?(15) how may a test object be used to assess sensitivity / penetration of an ultrasound system? (4) Part B: Q. 14. Describe three methods by which ultrasound image data can be collected for use in 3 D imaging. Explain the ways in which 3 D ultrasound image data can be displayed? Give an example of how 3 D imaging may be used clinically and briefly discuss its limitations (14). Explain the process of tissue harmonic imaging . What are the potential advantages of tissue harmonic imaging ? (11)
Posted on: Thu, 13 Nov 2014 21:10:51 +0000
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