ABSTRACT
Bernoulli formula d. Duplex typically combines a Doppler image with A-mode
imaging e. Using the Doppler equation shows that the reflected frequency
is proportional to the speed of a moving interface
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22. performed with a
single transmit/receive probe c. The spectral trace only provides information on direction and
mean velocity of flow d. A colour mapped Doppler image provides more accurate velocity
data than spectral imaging e. Power Doppler is more sensitive in identifying flow than colour
Doppler
23. Quality assurance in ultrasound: a. Ultrasound probe resolution can be tested by scanning a frame
of wires immersed in a liquid b. A faulty transducer element in a linear array probe is
not noticeable in the image since there are over 100 other functioning elements
c. The Doppler function may be calibrated using a Leeds test object
d. Ultrasound can be tested using gelatine based phantoms e. Mechanical Index (MI) describes the manoeuvrability of the
beam with a phased array
24. Image quality in ultrasound: a. Axial resolution is improved with lower frequency ultrasound b. Lateral resolution is best in the focal zone c. Phantoms for testing resolution consist of a solid Perspex box
with a variety of copper rods of different diameters running through them
d. Quality assurance requires that distance measurements are accurate to 0.2%
e. Tissue mimicking phantoms can be used to assess greyscale
25. Ultrasound resolution: a. Axial (depth) resolution in ultrasound is better than lateral
resolution b. Axial resolution is proportional to the wavelength of the sound c. Lateral resolution is the ability to distinguish two
objects perpendicular to the direction of the wave d. The lateral resolution is approximately equal to the beam width
at the depth of the objects e. Lateral resolution for ultrasound focused at 5 cm depth would
be in the region of 1 mm
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26. of the Ionising
b. Time averaged intensity should nowhere exceed 100 mW/cm2
and total energy should not exceed 50 J/cm2
c. The intensity of the ultrasound beam at the focal region averaged over the course of the examination is approximately 10 mW/cm2
d. The power of an ultrasound probe may be measured with a force balance used to assess the sound pressure
e. The Thermal Index (TI) is the ratio of the power output divided by the power required to raise the temperature of the tissue by 18C
27. Safety in ultrasound: a. The British Medical Ultrasound Society (BMUS) produces
safety guidelines for the use of diagnostic ultrasound b. It is bad practice to hold the probe stationary for extended
periods of time while it is transmitting ultrasound c. Pulsed Doppler is used routinely in eye examination d. An MI . 0.7 indicates a potential risk of cavitation e. With a TI of 1.0, fetal scanning should be limited to 30 min
28. Guidelines for the use of ultrasound: a. MI should not be greater than 0.7 if a contrast medium is used b. MI . 0.3 should not be used in non-diagnostic fetal ultrasound
scans c. MI . 0.3 should not be used in fetal ultrasound scans d. According to BMUS guidelines, the abdomen of a pyrexial adult
patient (388C) can safely be scanned for up to 45 min at a TI of 3 e. Ionising Radiation (Medical Exposure) Regulations (IR(ME)R)
state that justification of ultrasound requests must only be made by a registered medical practitioner
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1a. True 3 MHz might be used on an abdominal probe, 15 MHz for examining an eye.
