In-Plane Resolution of a Benchtop Thermoacoustic Tomography System - Effects of Electric Field Polarization
Mentor 1
Sarah Patch
Location
Union Wisconsin Room
Start Date
24-4-2015 10:30 AM
End Date
24-4-2015 11:45 AM
Description
Purpose: To investigate quantify in-plane resolution of a benchtop thermoacoustic tomography system that irradiates with very high frequency (VHF) electromagnetic pulses. A wire phantom sensitive to electric field polarization was used to determine best- and worst-case resolution. Methods: In order to determine the system’s resolution, cross-wires were used to sense the generated signal in the electric field. A wire phantom made of mutually perpendicular wires with cross wires horizontal was suspended from the stepper motor and inside a test bed where an electromagnetic field is generated. The cross-wires were attached to either end of a signal generating, 180 micron copper wire vertical. Greatest signal was generated when the wires were oriented correctly: cross-wires facing opposite directions (a view from the top would show cross with a perfect 90 degrees angle. Weakest signal, or no signal –in theory- was collected when the cross-wires were not in the right orientation relative to the electric field polarization. To determine the effect of orientation on the generated signal, each scan was done twice: X-units away from isocenter; and X-units away from isocenter, but rotated 90 degrees. To see how much the distance from isocenter impacts the collected signal, 9 different scans were done. First scan was done at isocenter, then the wire phantom was moved 4 times ~3.0 mm farther out. A scan is done after each repositioning the wire and rotating it 0 degrees, and another is done at the same distance with a 90 degrees rotation. In a full scan, the wire goes in a 360 degrees rotation, the equivalent of 200 steps (each step is 1.8 degrees). A TCT projection is saved after each one-step rotation resulting in 200 projections in each TCT sinogram. At one point during the rotation, the wire is perfectly aligned with the magnetic field and that is when the greatest signal is collected. At another, the orientation of the cross-wires is totally out of the magnetic field and therefore, in theory, no signal is collected.
In-Plane Resolution of a Benchtop Thermoacoustic Tomography System - Effects of Electric Field Polarization
Union Wisconsin Room
Purpose: To investigate quantify in-plane resolution of a benchtop thermoacoustic tomography system that irradiates with very high frequency (VHF) electromagnetic pulses. A wire phantom sensitive to electric field polarization was used to determine best- and worst-case resolution. Methods: In order to determine the system’s resolution, cross-wires were used to sense the generated signal in the electric field. A wire phantom made of mutually perpendicular wires with cross wires horizontal was suspended from the stepper motor and inside a test bed where an electromagnetic field is generated. The cross-wires were attached to either end of a signal generating, 180 micron copper wire vertical. Greatest signal was generated when the wires were oriented correctly: cross-wires facing opposite directions (a view from the top would show cross with a perfect 90 degrees angle. Weakest signal, or no signal –in theory- was collected when the cross-wires were not in the right orientation relative to the electric field polarization. To determine the effect of orientation on the generated signal, each scan was done twice: X-units away from isocenter; and X-units away from isocenter, but rotated 90 degrees. To see how much the distance from isocenter impacts the collected signal, 9 different scans were done. First scan was done at isocenter, then the wire phantom was moved 4 times ~3.0 mm farther out. A scan is done after each repositioning the wire and rotating it 0 degrees, and another is done at the same distance with a 90 degrees rotation. In a full scan, the wire goes in a 360 degrees rotation, the equivalent of 200 steps (each step is 1.8 degrees). A TCT projection is saved after each one-step rotation resulting in 200 projections in each TCT sinogram. At one point during the rotation, the wire is perfectly aligned with the magnetic field and that is when the greatest signal is collected. At another, the orientation of the cross-wires is totally out of the magnetic field and therefore, in theory, no signal is collected.
