Characterization of Ultrasound Elevation Beamwidth Artefacts for Brachytherapy Needle Insertion
Ultrasound elevation beamwidth is the out of plane thickness causing image artefacts normally appearing around anechoic areas in the medium. These artefacts could also cause uncertainties in localizing objects (such as a surgical needle) in the ultrasound image slices. This thesis studies the clinic...
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| Language: | en en |
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2011
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| Online Access: | http://hdl.handle.net/1974/6696 |
| Summary: | Ultrasound elevation beamwidth is the out of plane thickness causing image artefacts
normally appearing around anechoic areas in the medium. These artefacts could also
cause uncertainties in localizing objects (such as a surgical needle) in the ultrasound
image slices. This thesis studies the clinical significance of elevation beamwidth artefacts
in needle insertion procedures. A new measurement device was constructed to
measure the transrectal ultrasound elevation beamwidth. The beam profiles of various
lateral and axial distances to the transducer were generated. It is shown that
the ultrasound elevation beamwidth converges to a point within its focal zone close
to the transducer. This means that the transrectal ultrasound images have the best
resolution within the focal zone of the ultrasound close to the transducer. It is also
shown that the ultrasound device settings have a considerable impact on the amount
of beamwidth artefacts. Needle tip localization error was examined for a curvilinear
transrectal ultrasound transducer. Beveled prostate brachytherapy needles were inserted
through all holes of a grid template orthogonal to the axial beam axis. The
effects of device imaging parameters were also investigated on the amount of localization
error. Based on the developed results, it was found that the imaging parameters
of an ultrasound device have direct impact on the amount of object localization error
from 0.5 mm to 4 mm. The smallest localization error occurs laterally close to the center of the grid template, and axially within the beam’s focal zone. Similarly, the
largest localization error occurs laterally around both sides of the grid template, and
axially within the beam’s far field. Using the ultrasound device with appropriate
imaging settings could minimize the effects of these artefacts. We suggest to reduce
the gain setting of the ultrasound device. This will reduce the energies assigned to
the off-axis beams and as a result, the elevation beamwidth artefacts are minimized. === Thesis (Master, Computing) -- Queen's University, 2011-09-01 15:27:43.098 |
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