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  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 (R 1 )  Waves similar enough for interference patterns to form when passing through edges of object

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  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 R 1 +R 2  Size of two images are not equal  Scale images to account for magnification  Most likely shrink I to I abs for division  Poor accuracy will result in production of false edges

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, energy  Outputs:  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

Facilities  W.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?