C. David, IEEE Conference, Rome,

C. David, IEEE Conference, Rome, 21.10.2004
Phase Contrast X-Ray Radiography and Tomography Based on a Grating Interferometer C. David, T. Weitkamp, A. Diaz Laboratory for Micro- and Nanotechnology (LMN), Paul Scherrer Institut, Switzerland F. Pfeiffer, M. Stampanoni, J.F. van der Veen Swiss Light Source (SLS), Paul Scherrer Institut, Switzerland LMN SLS C. David, IEEE Conference, Rome,

X-rays for medical imaging
Minimizing the radiation dose is an important issue – especially in mammography low absorption contrast => large dose required to obtain sufficiently good S/N low applied photon energy (Mo anodes) screening submits a large number of healthy patients to radiation dose C. David, IEEE Conference, Rome,

Improving contrast Source Sample Detector C. David, IEEE Conference, Rome,

Improving contrast Source Sample Detector efficiency, size, resolution
C. David, IEEE Conference, Rome,

Improving contrast Source Sample Detector spectrum,
power, coherence efficiency, size, resolution C. David, IEEE Conference, Rome,

Improving contrast Source Sample Detector spectrum, contrast mechanism
power, coherence contrast mechanism efficiency, size, resolution C. David, IEEE Conference, Rome,

Phase contrast vs. amplitude contrast
n = 1 – d + ib x-rays C. David, IEEE Conference, Rome,

n = 1 – d + ib x-rays Example: 20 keV Organic sample (polymer, biological, medical…) 50 mm thickness C. David, IEEE Conference, Rome,

n = 1 – d + ib x-rays Example: 20 keV Organic sample (polymer, biological, medical…) 50 mm thickness  only 0.2 % absorption, but p- phase shift C. David, IEEE Conference, Rome,

n = 1 – d + ib + x-rays Example: 20 keV Organic sample (polymer, biological, medical…) 50 mm thickness  only 0.2 % absorption, but p- phase shift C. David, IEEE Conference, Rome,

n = 1 – d + ib + x-rays Example: 20 keV Organic sample (polymer, biological, medical…) 50 mm thickness  only 0.2 % absorption, but p- phase shift  much higher contrast  less dose required C. David, IEEE Conference, Rome,

Hard x-ray interferometry
detector Object Bonse-Hart Interferometer (since 1965) C. David, IEEE Conference, Rome,

detector Object Bonse-Hart Interferometer (since 1965) Object beam and reference beam are generated by Bragg reflections on thin Si crystals The interference of both beams gives a phase image C. David, IEEE Conference, Rome,

detector Object Bonse-Hart Interferometer (since 1965) optical path length difference needs to be stable to a fraction of a wavelengths picometer stability required cannot be scaled up Object beam and reference beam are generated by Bragg reflections on thin Si crystals The interference of both beams gives a phase image C. David, IEEE Conference, Rome,

Propagation methods – edge contrast

Propagation methods – edge contrast
phase shift greatly enhances contrast of edges can be used to retrieve phase information requires high degree of transverse coherence (i.e. small source size) cannot be scaled up to large fields of view (required detector resolution) C. David, IEEE Conference, Rome,

Grating x-ray interferometry
50 nm C. David, IEEE Conference, Rome,

beam-splitter phase grating s C. David, IEEE Conference, Rome,

beam-splitter phase grating interference pattern s C. David, IEEE Conference, Rome,

beam-splitter phase grating analyzer amplitude grating interference pattern camera C. David, IEEE Conference, Rome,

beam-splitter phase grating interference pattern analyzer amplitude grating Moiré fringes camera C. David, IEEE Conference, Rome,

beam-splitter phase grating analyzer amplitude grating interference pattern camera C. David, IEEE Conference, Rome,

beam-splitter phase grating analyzer amplitude grating interference pattern phase object camera C. David, IEEE Conference, Rome,

beam-splitter phase grating analyzer amplitude grating phase object interference pattern camera C. David, IEEE Conference, Rome,

beam-splitter phase grating analyzer amplitude grating interference pattern phase object camera C. David, IEEE Conference, Rome,

camera beam-splitter phase grating analyzer amplitude grating interference pattern phase object Differential phase contrast imaging! C. David, IEEE Conference, Rome,

The gratings Phase grating (silicon, p = 4 µm) 4 µm 4 µm 4 µm Si-110 wet-etched Depth of structures chosen so that phase shift is π  no zeroth order C. David, IEEE Conference, Rome,

The gratings Phase grating (silicon, p = 4 µm) Absorption grating (Au in silicon, q = 2 µm) 4 µm 4 µm 4 µm 4 µm 4 µm Si-110 wet-etched Depth of structures chosen so that phase shift is π  no zeroth order Au in gaps of Si grating Grown electrochemically Period is half that of the phase grating C. David, IEEE Conference, Rome,

polystyrene spheres Ø 100 and 200 µm Photon energy: 12.4 keV p = 4 µm q = 2 µm BM 5, ESRF, Dec. 2002 C. David, IEEE Conference, Rome,

Interferometric phase contrast
Absorption contrast and edge contrast C. David, IEEE Conference, Rome,

Absorption contrast and edge contrast Differential phase contrast C. David, IEEE Conference, Rome,

Absorption contrast and edge contrast Differential phase contrast Phase contrast Can be integrated to yield projected phase shift of sample  Suited for tomographic reconstruction C. David, IEEE Conference, Rome,

Edge contrast vs. Interferometric contrast
Non-interferometric Absorption and Edge contrast 0.5mm Projection Tomogram C. David, IEEE Conference, Rome,

Edge contrast vs. Interferometric contrast
Non-interferometric Interferometric phase contrast Absorption and Edge contrast Phase gradient Phase 0.5mm Projection Projection Projection ID19, ESRF, June 2004 14.4 keV Tomogram Tomogram C. David, IEEE Conference, Rome,

0.5mm C. David, IEEE Conference, Rome,

0.5 mm 1mm C. David, IEEE Conference, Rome,

Polychromatic radiation

beam-splitter phase grating analyzer amplitude grating phase object camera λ1 interference pattern C. David, IEEE Conference, Rome,

beam-splitter phase grating analyzer amplitude grating phase object camera λ2 λ1 interference pattern C. David, IEEE Conference, Rome,

Pink-beam phase tomography
Beam conditioning: SLS wiggler No monochromator Zr absorption filter 100 µm Camera scintillator YAG: Y absorption edge at 17.0 keV acts as high-pass filter Mean energy E = 17.5 keV Bandwidth ΔE ≈ 1 keV C. David, IEEE Conference, Rome,

Beam conditioning: SLS wiggler No monochromator Zr absorption filter 100 µm Camera scintillator YAG: Y absorption edge at 17.0 keV acts as high-pass filter Mean energy E = 17.5 keV Bandwidth ΔE ≈ 1 keV Sample: Three fibers Polyamide Ø 225 µm Boron Ø 200 µm, core: W Ø 10 µm PBT Ø 190 µm C. David, IEEE Conference, Rome,

Edge contrast Sample: Three fibers Polyamide Ø 225 µm Boron Ø 200 µm, core: W Ø 10 µm PBT Ø 190 µm C. David, IEEE Conference, Rome,

Edge contrast Sample: Three fibers Polyamide Ø 225 µm Boron Ø 200 µm, core: W Ø 10 µm PBT Ø 190 µm Differential phase contrast C. David, IEEE Conference, Rome,

Edge contrast Sample: Three fibers Polyamide Ø 225 µm Boron Ø 200 µm, core: W Ø 10 µm PBT Ø 190 µm Differential phase contrast Phase contrast C. David, IEEE Conference, Rome,

Edge contrast tomogram Edge contrast Sample: Three fibers Polyamide Ø 225 µm Boron Ø 200 µm, core: W Ø 10 µm PBT Ø 190 µm Phase contrast tomogram Differential phase contrast Phase contrast C. David, IEEE Conference, Rome,

Required transverse coherence

camera d C. David, IEEE Conference, Rome,

camera d In our experiments: E = 17.5 keV, => l = 0.07nm d = 28mm, => s = 1mm C. David, IEEE Conference, Rome,

camera d In our experiments: E = 17.5 keV, => l = 0.07nm d = 28mm, => s = 1mm Transverse coherence length c: c = l * p/s p: source distance, e.g. 2m s: source size, e.g. 100mm C. David, IEEE Conference, Rome,

camera d In our experiments: E = 17.5 keV, => l = 0.07nm d = 28mm, => s = 1mm Transverse coherence length c: c = l * p/s = 1.4mm p: source distance, e.g. 2m s: source size, e.g. 100mm C. David, IEEE Conference, Rome,

Summary C. David, IEEE Conference, Rome,

Summary There is a large potential to reduce the x-ray dose in medical imaging by exploiting the phase shifting property of matter rather than the absorption C. David, IEEE Conference, Rome,

Summary There is a large potential to reduce the x-ray dose in medical imaging by exploiting the phase shifting property of matter rather than the absorption Grating interferometry offers advantages compared to other phase imaging methods : C. David, IEEE Conference, Rome,

Summary There is a large potential to reduce the x-ray dose in medical imaging by exploiting the phase shifting property of matter rather than the absorption Grating interferometry offers advantages compared to other phase imaging methods : Robustness Quantitative method Works fine at energies suitable for mammography Requires no temporal and little spatial coherence Has potential to be scaled up to large fields of view C. David, IEEE Conference, Rome,

Acknowledgments Many thanks to: At PSI E. Deckardt F. Glaus B. Haas Y. Hemmerling L. Heyderman M. Lange J. Lehmann D. Meister T. Neiger B. Nöhammer T. Rohbeck At ESRF: P. Cloetens J. Hoszowska E. Ziegler and many others ... Funding: Swiss National Science Foundation European Community C. David, IEEE Conference, Rome,

Postdoc Position available
Acknowledgments Many thanks to: At PSI E. Deckardt F. Glaus B. Haas Y. Hemmerling L. Heyderman M. Lange J. Lehmann D. Meister T. Neiger B. Nöhammer T. Rohbeck At ESRF: P. Cloetens J. Hoszowska E. Ziegler and many others ... Funding: Swiss National Science Foundation European Community Postdoc Position available C. David, IEEE Conference, Rome,

C. David, IEEE Conference, Rome,

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