Post on 20-Jan-2016
Optimization of Phase Contrast Imaging
Luke PowersChris Weaver
Jonathan FermoAlfred Luk
BME 273, Group 2204/06/2005
Phase-Contrast Radiography Traditional radiography uses
differences in absorption to develop images
Phase-contrast Radiography (PC-R) uses differences in refraction and diffraction of the x-ray beam as it passes through the object
Results in enhanced edge effects in image compared to those found in absorption images
Objectives
Build a device that aids in testing Phase Contrast Radiography parameters
Computer controlled movement of the object and detector
Maintain high control accuracy in order to pick up edges in tissue
PC-R Potential
Edge Enhancements Has potential to detect objects that are
invisible on conventional radiography due to edge enhancements in images.
Monochromatic Tunable to specific wavelengths Monochromatic beam reduces excess
radiation dosage to patient.
Spatial Coherence
Description of the divergence of a wave Desire a very large spatial coherence (d):
decrease focal spot size (f)
increase source-object distance (R1) Waves similar enough for interference patterns to
form when passing through edges of object
f
λRd
1
Edge Effects
Waves near edges are bent
Waves not touching or passing through are not affected
Edge enhancement seen on film
Angle shift insignificant at close distances
Producing Phase Contrast
)("
21)()( 0 x
zxIxI z
Image has two components: absorption and phase Wavelength is tunable due to monochromatic source Components functions of position Goal is to divide out absorption Absorption component detector touching object
Magnification Effect
Changing R1+R2
Size of two images are not equal Scale images to account for magnification Most likely shrink I to Iabs for division Poor accuracy will result in production of false edges
1
21
R
RRM
ag
)("
21)()( 0 x
zxIxI z
Our Device
Main Uses:
• Optimizing distances for PC imaging of specific objects/tissues
• Produce reproducible images
• Produce no false edge effects
• Images using scattering, defines pixel resolution < 150 microns
Additional Uses:
• Rotational movement for CT images
Programming Inputs:
LabView GUI: positions, energyOutputs:
Time/Date Image # Angle and x, y, z positions Energy Used
Advisors Advisors:
Frank E. Carroll, M.D. Gary Shearer Robert Traeger
Principal Investigator: Edwin Donnelly, M.D., Ph.D. from Vanderbilt in
Biomedical Engineering
FacilitiesW.M. Keck Free
Electron Laser Center at Vanderbilt
Vanderbilt BME Department
Resources Monochromatic X-
ray source at FEL LabVIEW and
Virtual Instruments Stages, controllers,
etc… for design construction provided by FEL & outside contractors
Design Schematic-Detector has z-stage movement (1m)
-Object has x (6cm), y (5cm), rotational (360 degrees) movement
Components
Selected Components
Microcontroller Linear Translation Stage (z)
Questions?