Interaction of X-rays with Matter and Imaging Gocha Khelashvili Assistant Research Professor of Physics Illinois Institute of Technology Research Physicist EXELAR Medical Corporation

The Plan X-ray Interactions with Matter Used at Imaging Energies Photoelectric Effect Coherent Scattering Incoherent Scattering Refraction Small- and Ultra-small Angle Scattering Radiography How does it work? Imaging Parameters and Sources of X-ray contrast Drawbacks of Radiography Diffraction Enhanced Imaging (DEI) How does it work? Imaging Parameters and Sources of X-ray contrast Drawbacks of DEI Multiple Image Radiography (MIR-Planar Mode) How does it work? Sources of X-ray contrast MIR parameters and images MIR Model Based on Discrete Scatterers Multiple scattering series approach and MIR transport equation Solution of MIR transport equation Imaging Parameters Laboratory DEI / MIR Machine Summary

Photoelectric Effect

Thompson (Classical) Scattering

Rayleigh Scattering (Coherent Scattering)

Compton Scattering (Incoherent Scattering)

Effects of Binding Energy in Compton (Incoherent) Scattering

Radiography Setup

Radiography Setup and Imaging Principles Double Crystal Monochromator Si(333) Object Radiology Setup Area Detector Incident X-ray beam Attenuation Law Image Image Contrast

Drawbacks of Radiography Object PixelDetector Pixel Attenuated Beam (by absorption) Incoherently Scattered Beam Image Contrast

DEI Setup and Imaging Principles Area Detector Object Analyzer Crystal Si(333) DEI Setup Incident X-ray beam Double Crystal Monochromator Si(333)

Formation of DE Images Object Pixel Detector Pixel Enhanced Attenuated Beam Incoherently Scattered Beam is Blocked by Crystal

Low Angle Side High Angle Side Analyzer Angle (  radians) Physics of DEI Pisano, Johnston(UNC); Sayers(NCSU); Zhong (BNL); Thomlinson (ESRF); Chapman(IIT) Relative Intensity I/Io Data from NSLS X27

Calculation of DEI Images Low Angle Side High Angle Side Analyzer Angle (  rad) Relative Intensity I/Io

MapConventional DEI Comparison - Conventional and DEI ACR - Phantom

DEI image of ACR phantom - smallest calcifications Data from NSLS X27

ConventionalDEI - AbsorptionDEI - Refraction Cancer in Breast Tissue BNL Sept 1997 Pisano, Johnston(UNC); Sayers(NCSU); Zhong (BNL); Thomlinson (ESRF); Chapman(IIT)

Drawbacks of DEI Object Pixel Detector Pixel

Experimental Evidence of Problems in DEI

Experimental Results

Refraction images Profiles thick paper thin paper no paper Position (pixels) MIR DEI MIR DEI

Generalization to CT Reconstruction

Discrete Scatterer Model Object Voxel Khelashvili, Brankov (IIT), Chapman (U.Sask), Anastasio, Yang (IIT), Zang (BNL), Wernick (IIT)

Multiple Ultra-Small Angle Scattering Radiation Transport Theory Approach

MIR Radiation Transfer Equation

Ultra-Small Angle Approximation

General Solution

Phase Function

Khelashvili, Brankov (IIT), Chapman (U.Sask), Anastasio, Yang (IIT), Zang (BNL), Wernick (IIT)

Plane Wave Solution Khelashvili, Brankov (IIT), Chapman (U.Sask), Anastasio, Yang (IIT), Zang (BNL), Wernick (IIT)

Plane Wave Solution Khelashvili, Brankov (IIT), Chapman (U.Sask), Anastasio, Yang (IIT), Zang (BNL), Wernick (IIT)

Imaging Parameters Khelashvili, Brankov (IIT), Chapman (U.Sask), Anastasio, Yang (IIT), Zang (BNL), Wernick (IIT)

Experimental Conformation Lucite container – wedge shaped. Polymethylmethacrylate (PMMA) microspheres in glycerin. Khelashvili, Brankov (IIT), Chapman (U.Sask), Anastasio, Yang (IIT), Zang (BNL), Wernick (IIT)

Experimental Conformation Khelashvili, Brankov (IIT), Chapman (U.Sask), Anastasio, Yang (IIT), Zang (BNL), Wernick (IIT)

labDEI System Detector Analyzer Pre-mono & Mono X-ray Source Morrison, Nesch, Torres, Khelashvili (IIT), Hasnah (U. Qatar) Chapman (U.Sask)

1cm cartilage bone Lab DEI System tissue images Morrison, Nesch, Torres, Khelashvili, Chapman (IIT) Muehleman (Rush Medical College)

Summary First reliable Theoretical Model of DEI – MIR has been developed. Model can be used to simulate experiments starting from source, through crystals (this was known), through object (was unknown), through analyzer crystal (partially known – dynamical theory of diffraction – but crystal and beam specific calculations need to be done). CT reconstructions – some steps are already taken in this direction – Miles N. Wernick et al “Preliminary study of multiple-image computed tomography” CSRRI (IIT) / Nesch LLC – are developing in-lab research DEI instrument

Acknowledgements Funded by NIH/NIAMS. L.D. Chapman (Anatomy and Cell Biology, University of Saskatchewan, Canada) J. Brankov, M. Wernick, Y. Yang, M. Anastasio (Biomed. Engineering, IIT) T. Morrison and I. Nesch (CSRRI, IIT) C. Muehleman (Department of Anatomy and Cell Biology, Rush Medical College)