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Optimization of Phase Contrast Imaging

Optimization of Phase Contrast Imaging. Luke Powers Chris Weaver Jonathan Fermo Alfred Luk BME 273, Group 22 04/06/2005. Phase-Contrast Radiography. Traditional radiography uses differences in absorption to develop images

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Optimization of Phase Contrast Imaging

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  1. Optimization of Phase Contrast Imaging Luke Powers Chris Weaver Jonathan Fermo Alfred Luk BME 273, Group 22 04/06/2005

  2. 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

  3. 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

  4. 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.

  5. 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

  6. 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

  7. Producing Phase Contrast • 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

  8. 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

  9. 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

  10. Programming • Inputs: • LabView GUI: positions, energy • Outputs: • Time/Date • Image # • Angle and x, y, z positions • Energy Used

  11. Advisors • Advisors: • Frank E. Carroll, M.D. • Gary Shearer • Robert Traeger • Principal Investigator: • Edwin Donnelly, M.D., • Ph.D. from Vanderbilt in Biomedical Engineering

  12. Facilities • W.M. Keck Free Electron Laser Center at Vanderbilt • Vanderbilt BME Department

  13. Resources • Monochromatic X-ray source at FEL • LabVIEW and Virtual Instruments • Stages, controllers, etc… for design construction provided by FEL & outside contractors

  14. Design Schematic -Detector has z-stage movement (1m) -Object has x (6cm), y (5cm), rotational (360 degrees) movement

  15. Components

  16. Selected Components Microcontroller Linear Translation Stage (z)

  17. Questions?

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