Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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 λR1 d f 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 z I ( x ) I ( x ) z 0 1 " ( x) 2 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 R 1 R2 Mag R1 z I ( x ) I ( x ) z 0 1 " ( x) 2 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 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 Xray 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?