Optimization of Phase Contrast Imaging Luke Powers Chris Weaver Jonathan Fermo Alfred Luk BME 273, Group 22 03/14/2005

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

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

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 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

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

PC-R Potential Phase Contrast Radiography: Has potential to detect objects that are invisible on conventional radiography Edge enhancements and early detection of breast cancer Monochromatic beam reduces excess radiation dosage to patient

Objectives Build a device that aids in testing PC-R parameters Stage movement & control accurate enough to pick up edges Computer controlled movement of the object and detector

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

Advisors Advisors: Principal Investigator: 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

Machine Shop Work Stepper motor mounts for x and y stages Mounting Rotational Stage on x-y stage

Components

Linear Translation Stage (z) Selected Components Microcontroller Linear Translation Stage (z)

Questions?