Ultrasound Physics Instrumentation 1 by bzu20592

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									                                             DIVISION OF
                                           HEALTH SCIENCES



                                    SCHOOL OF HEALTH SCIENCES


    Subject Area:   RADY                              Catalogue Number:       5017



               ULTRASOUND PHYSICS & INSTRUMENTATION 1

Examination Day: Tuesday                              Examination Date: 27th June 2006

                                                      Length of Exam: 2 hours plus 10 minutes reading
Examination Time: 6.30 pm
                                                      time


Examination Venue:         Ridley Convention & Exhibition Centre, Royal Adelaide Showgrounds



                                     Instructions to Candidates




Time allowed: 120 minutes

     Attempt ALL questions
     Answer questions in the examination booklet(s) provided.
     A non-programmable calculator is required for this examination
     ALL calculations must be shown
     Clearly labelled diagrams should be used whenever possible
     ALL symbols have their usual meanings
     Marks for each question are indicated in [ ]

                                         Total Marks: 120
1.    Describe the basic principles behind the formation of a two-dimensional,
      B-mode ultrasound image.                                                 [5]

2.    What determines the acoustic velocity of an ultrasound beam as it passes
      through a given medium?                                                  [2]

3.    Explain why the office-desk toys composed of a row of steel bowls suspended on
      strings are a good analogy for understanding some of the basic principles of
      ultrasound wave propagation.                                               [5]

4.    If the intensity of the beam is increased 5-fold what effect will this have on
      amplitude? Define what is meant by intensity and amplitude.                    [5]

6.    What is the maximum PRF achievable when scanning with a 5cm deep field of
      view (FOV)?                                                          [2]

7.    The dynamic range (DR) of echoes returning to a transducer is 100dB. Express
      this as a ratio of strongest to weakest echo intensities.               [3]

8.    Discuss the factors involved in determining how strong an echo will be after an
      ultrasound pulse is transmitted into the body.                             [4]

9.    A 4MHz ultrasound beam passes through soft tissue that has an acoustic
      attenuation coefficient of 1.2 dB/MHz/cm. It then encounters an interface at a
      depth of 13cm, the acoustic impedance values of the media making up the
      interface are as follows, Z1 = 12 rayls and Z2 = 17 rayls. Determine in dB the
      intensity of an echo returning from this interface relative to the outward pulse.
      Also sketch a diagram that describes what is happening.                      [10]

10.   Describe what is meant by the term Tissue Harmonic Imaging.                      [5]

11.   What is meant by the term Duty Factor?                                           [2]

12.   Discuss how a more directional ultrasound beam (with a longer near field)
      can be produced. Are there any tradeoffs involved?                        [6]

13.   What effect (if any) does the degree of damping offered by the backing
      material have on the sensitivity of an ultrasound transducer?                    [2]

14.   Outline the factors that determine the spatial resolution ability of an
      ultrasound system.                                                               [5]




                                                                                /please turn over

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15.   List the three basic functions of a scan converter.                           [3]

16.   What is the maximum frame rate achievable when using a 10cm deep field of
      view (FOV) containing 200 lines of sight, with 4 focal zones in use? How could
      the frame rate be improved in this setting?                              [5]

17.   Differentiate between the following two electronic focusing techniques; dynamic
      aperture and dynamic receive focusing.                                    [5]

18.   Discuss how multiple focal zones can help improve lateral resolution throughout
      the field of view (FOV).                                                  [5]

19.   The most common numeric notation used in day to day life is decimal notation.
      Why then do computers continue to operate using binary notation?        [2]

20.   Calculate the best theoretical axial resolution possible using 5MHz ultrasound that
      contains 4 cycles/pulse.                                                    [4]

21.   Differentiate between preprocessing and postprocessing. Name three different
      preprocessing and postprocessing functions (i.e. 6 functions in all!)    [6]

23.   When is the acoustic enhancement artefact seen?                               [2]

24.   Why do a dense gallbladder calculus and a focus of bowel gas have a similar
      appearance on ultrasound? How can they be differentiated?                [6]

25.   Discuss how the reverberation artefact is formed. In what areas of the body is this
      and other artefacts generally most prominent?                              [5]

26.   What basic assumption of ultrasound imaging is shown to be incorrect when a
      slice thickness artefact is seen?                                       [3]

27.   Discuss the effect of varying the bit depth of the computer memory on the
      conversion of the analogy signal received into a digital value for storage in
      memory.                                                                       [5]

28.   Explain why a Range Ambiguity artefact occurs.                                [3]

29.   As you move from scanning the liver to the smaller and more superficial gall
      bladder, what is the benefit of reducing the depth of the field of view in contrast to
      just magnifying the gall bladder area with the post-processing zoom control?
                                                                                    [5]

30.   Outline what is meant by the term 4D ultrasound and describe how a 4D
      ultrasound image can be produced.                                     [5]
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