Tech Notes 元xradia High Contrast for Difficult-to-Image Materials VersaXRM Traditionally,laboratory X-ray systems and X-ray micro tomography(microCT)systems have been widely used as instruments to image metals or bone.However,while they are able to image details in these highly absorbing materials,imaging other types of materials to achieve significant contrast has proven to be difficult. Examples of these"difficult-to image"materials include: Low atomic number (low Z)materials,such as soft tissue and polymers Materials of similar Z indices,such as ceramics sintered from multiple compounds of similar Z indices and fossilized organisms encased in amber Due to its unique system architecture,the Xradia VersaXRMTM family of 3D X-ray 750μm2 microscopes(XRM)provides high contrast for traditionally "difficult-to-image"materials to reveal details that enable visualization and quantification of features. Flower stamen imaged with phase contrast to show cellular composition The VersaXRM contrast advantage is due to: 1.Enhanced Absorption Contrast Detectors:the Xradia detector system consists of multiple proprietary detectors that are each optimized to maximize collection of low energy photons and minimize collection of contrast-reducing high energy photons to achieve superior contrast. 2.Tunable Propagation Phase Contrast:Most microCTs use absorption imaging only,which measures features based on the number of X-ray photons absorbed.Phase contrast,which measures the refraction of X-ray photons by materials, also allows visualization of features that have very low or no contrast in absorption imaging. These unique system features enable the Xradia microscopes to provide superior contrast for a range of materials,such as: Soft Materials Biological Specimens 500μm 250μm 250pm Collagen scaffold with CaP inclusions Pear imaged with absorption contrast- Pear imaged with phase contrast, no visibility of cell walls showing details of cell walls in nomal cells and stone cells Image samples in background (from top to right):carbonate,concrete,network of cerebral vasculature,semiconductor packaging
High Contrast for Difficult-to-Image Materials VersaXRM Tech Notes Traditionally, laboratory X-ray systems and X-ray micro tomography (microCT) systems have been widely used as instruments to image metals or bone. However, while they are able to image details in these highly absorbing materials, imaging other types of materials to achieve significant contrast has proven to be difficult. Examples of these “difficult-to image” materials include: • Low atomic number (low Z) materials, such as soft tissue and polymers • Materials of similar Z indices, such as ceramics sintered from multiple compounds of similar Z indices and fossilized organisms encased in amber Due to its unique system architecture, the Xradia VersaXRM™ family of 3D X-ray microscopes (XRM) provides high contrast for traditionally “difficult-to-image” materials to reveal details that enable visualization and quantification of features. The VersaXRM contrast advantage is due to: 1. Enhanced Absorption Contrast Detectors: the Xradia detector system consists of multiple proprietary detectors that are each optimized to maximize collection of low energy photons and minimize collection of contrast-reducing high energy photons to achieve superior contrast. 2. Tunable Propagation Phase Contrast: Most microCTs use absorption imaging only, which measures features based on the number of X-ray photons absorbed. Phase contrast, which measures the refraction of X-ray photons by materials, also allows visualization of features that have very low or no contrast in absorption imaging. These unique system features enable the Xradia microscopes to provide superior contrast for a range of materials, such as: Soft Materials Biological Specimens Collagen scaffold with CaP inclusions Pear imaged with absorption contrast – no visibility of cell walls Pear imaged with phase contrast, showing details of cell walls in normal cells and stone cells Image samples in background (from top to right): carbonate, concrete, network of cerebral vasculature, semiconductor packaging. Flower stamen imaged with phase contrast to show cellular composition 750 µm 500 µm 250 µm 250 µm
Understanding the Technical Advantage of Xradia Contrast VersaXRM:Advanced Absorption Contrast Absorption contrast,the common imaging modality used by advantages for the absorption imaging modality.In comparison, most X-ray imaging equipment,measures the attenuation of conventional microCT systems use a single large area detector a beam of X-rays through a sample.For absorbing materials, such as a flat panel that must cover the entire range of X-ray this type of contrast is familiar,relatively fast,and easily imaging operating conditions.Because it must be optimized for segmentable for quantification analysis. efficient capture of the system's highest X-ray energies,there are inefficiencies in capturing low energy X-rays.This results in a contrast trade-off for a large variety of low Z materials such as soft tissue,fluids and gels,carbon and glass fibers,polymers. and silicon. Xradia's Matched Set of Contrast Enhanced Detectors The multi-scintillator detector system in the VersaXRM family provides optimized absorption contrast for each resolution setting.This results in superior imaging quality for a wide range The Xradia VersaXRM employs a proprietary detector system of materials that are traditionally considered"difficult to image." comprising a rotating detector turret with selectable magnification Each optimized detector preferentially images within the contrast- and field-of-view pairings,analogous to an optical light micro- forming useful energy band,while minimizing detection of higher scope.In addition to providing different resolutions,each detec- energy X-rays.Higher contrast images can be produced by tor objective also features a matched scintillator that optimizes removing these higher energy photons,which tend to be contrast for that objective.This technology provides unique unattenuated and wash out the contrast in an image. Optimized Spectral Detection Non-optimized Detector(flat panel) Optimized Detector (Xradia) Useful Emax X-ray Energy Energy Band Background An optimized detector maximizes sensitivity to the band in the X-ray spectrum most sensitive to absorption changes in the sample (useful energy band)and minimizes the capture of higher energy X-ray photons that do not cary a signal (background).Most general purpose,non-optimized detectors such as flat panels are configured to detect a wide range of X-ray spectra and therefore capture significant background noise,reducing image contrast
Absorption contrast, the common imaging modality used by most X-ray imaging equipment, measures the attenuation of a beam of X-rays through a sample. For absorbing materials, this type of contrast is familiar, relatively fast, and easily segmentable for quantification analysis. The Xradia VersaXRM employs a proprietary detector system comprising a rotating detector turret with selectable magnification and field-of-view pairings, analogous to an optical light microscope. In addition to providing different resolutions, each detector objective also features a matched scintillator that optimizes contrast for that objective. This technology provides unique advantages for the absorption imaging modality. In comparison, conventional microCT systems use a single large area detector such as a flat panel that must cover the entire range of X-ray imaging operating conditions. Because it must be optimized for efficient capture of the system’s highest X-ray energies, there are inefficiencies in capturing low energy X-rays. This results in a contrast trade-off for a large variety of low Z materials such as soft tissue, fluids and gels, carbon and glass fibers, polymers, and silicon. Xradia’s Matched Set of Contrast Enhanced Detectors The multi-scintillator detector system in the VersaXRM family provides optimized absorption contrast for each resolution setting. This results in superior imaging quality for a wide range of materials that are traditionally considered “difficult to image.” Each optimized detector preferentially images within the contrastforming useful energy band, while minimizing detection of higher energy X-rays. Higher contrast images can be produced by removing these higher energy photons, which tend to be unattenuated and wash out the contrast in an image. Understanding the Technical Advantage of Xradia Contrast An optimized detector maximizes sensitivity to the band in the X-ray spectrum most sensitive to absorption changes in the sample (useful energy band) and minimizes the capture of higher energy X-ray photons that do not carry a signal (background). Most general purpose, non-optimized detectors such as flat panels are configured to detect a wide range of X-ray spectra and therefore capture significant background noise, reducing image contrast. 1 Optimized Spectral Detection VersaXRM: Advanced Absorption Contrast
Tech Notes 入xradia VersaXRM VersaXRM:Unique Propagation Phase Contrast In 1918,Einstein provided the first description of the nature the sample-to-detector distance(R2).Flat panel detectors of of the refractive index for X-rays,showing that phase contrast conventional microCT systems,which typically have detector effects are significant.A century later,most X-ray microscopy pixel sizes on the order of 50-100 um,are unable to capture and nearly all medical imaging remain based on absorption the majority of phase contrast information because the phase contrast,even though phase contrast offers orders of magni- fringe-widths tend to be much smaller than the detector pixel tude improvement in contrast,and provides 103 times more size.In contrast,Xradia X-ray microscope detectors achieve contrast for low Z and soft tissue imaging. pixel sizes down to a third of a micron(0.34 um)and are thus small enough to capture detailed phase information. Phase contrast differs from absorption contrast by measuring the refraction of X-rays rather than the attenuation of X-rays. An illustration of phase contrast as a function of source-sample As an X-ray wave travels through a particular material,the (R1)and sample-detector(R2)distances can be seen in the image refractive index of the material will affect the speed of the below that charts the contrast transfer function(CTF)for imaging propagation,causing a phase shift in the wave that exits the a 1.5 um feature at 40 kV.The red lines in the upper left represent material.Thus a sample composed of several materials of the operational realm of two typical high-end flat panel-based different refractive indices will produce waves of different phases. microCTs,while the black lines represent the optimum operating These waves then interfere at the detector plane,causing range of the medium magnification 4X detector and the high light and dark interference phase fringes(ripples)to appear magnification 20X detector on the Xradia VersaXRM.The grey at the boundaries between separate regions. box indicates the overall operating range of the instrument. Absorption Absorption phase 1000 CTFB1,2,f=1.5m) 100 10 Source 10 100 1000 R1 [mm] -high-end micro-CT flat panel detector .-----Xradia 4X ----X灯adia20X R1 R2 oversampling factor:2 Xradia Phase Contrast Advantage The flat panel system's phase contrast capabilities are severely The Xradia VersaXRM family uniquely enables phase contrast limited due to their large pixel size and requirement for high imaging through a combination of small effective detector pixel geometric magnification(R2>>R1),whereas the Xradia detectors sizes and by providing a flexible range of source and detector provide the ability to tune the phase contrast from practically travel distances.The size of the phase contrast fringe in labor- zero up to an optimal value that highlights interfaces. atory systems is a function of the energy spectrum of the X-rays and the convolution of the source-to-sample distance(R1)and
Tech Notes Understanding the Technical Advantage of Xradia Contrast VersaXRM In 1918, Einstein provided the first description of the nature of the refractive index for X-rays, showing that phase contrast effects are significant. A century later, most X-ray microscopy and nearly all medical imaging remain based on absorption contrast, even though phase contrast offers orders of magnitude improvement in contrast, and provides 10³ times more contrast for low Z and soft tissue imaging. Phase contrast differs from absorption contrast by measuring the refraction of X-rays rather than the attenuation of X-rays. As an X-ray wave travels through a particular material, the refractive index of the material will affect the speed of the propagation, causing a phase shift in the wave that exits the material. Thus a sample composed of several materials of different refractive indices will produce waves of different phases. These waves then interfere at the detector plane, causing light and dark interference phase fringes (ripples) to appear at the boundaries between separate regions. Xradia Phase Contrast Advantage The Xradia VersaXRM family uniquely enables phase contrast imaging through a combination of small effective detector pixel sizes and by providing a flexible range of source and detector travel distances. The size of the phase contrast fringe in laboratory systems is a function of the energy spectrum of the X-rays and the convolution of the source-to-sample distance (R1) and the sample-to-detector distance (R2). Flat panel detectors of conventional microCT systems, which typically have detector pixel sizes on the order of 50-100 μm, are unable to capture the majority of phase contrast information because the phase fringe-widths tend to be much smaller than the detector pixel size. In contrast, Xradia X-ray microscope detectors achieve pixel sizes down to a third of a micron (0.34 μm) and are thus small enough to capture detailed phase information. An illustration of phase contrast as a function of source-sample (R1) and sample-detector (R2) distances can be seen in the image below that charts the contrast transfer function (CTF) for imaging a 1.5 μm feature at 40 kV. The red lines in the upper left represent the operational realm of two typical high-end flat panel-based microCTs, while the black lines represent the optimum operating range of the medium magnification 4X detector and the high magnification 20X detector on the Xradia VersaXRM. The grey box indicates the overall operating range of the instrument. The flat panel system’s phase contrast capabilities are severely limited due to their large pixel size and requirement for high geometric magnification (R2>>R1), whereas the Xradia detectors provide the ability to tune the phase contrast from practically zero up to an optimal value that highlights interfaces. VersaXRM: Unique Propagation Phase Contrast 1 10 100 1000 R1 [mm] 1 10 100 1000 R2 [mm] max min high-end micro-CT flat panel detector Xradia 20X Xradia 4X oversampling factor: 2 CTF (R1, R2, f = 1.5 µm) Absorption Absorption + phase
Tech Notes High Contrast for Difficult-to-Image Materials VersaXRM Optimized Architecture Superior Imaging The Xradia VersaXRM family provides superior imaging in both flexible source and detector travel enables the user to optimize absorption imaging mode and propagation-based phase con- the propagation phase contrast effect.This approach enables trast imaging mode.The imaging objectives in the X-ray micro- imaging of features in materials that are traditionally considered scope turret contain scintillators that are optimized by objective "difficult-to-image,"such as soft biological tissues and polymers, to provide the highest absorption contrast.The characteristic or in samples composed of constituents that are of similar small detector pixel sizes of the XRM architecture coupled with absorption contrasts. These include: Porous polymer network: Phase and absorption contrast to obtain a high resolution image for quantification of pore size measurements,wall- thickness measurements,and degree of interconnectivity. 750μm 200u9 Unstained soft tissue: Phase contrast was employed to image unstained cartilage in a mouse knee. Spider: Phase contrast to Absorption Contrast 200um visualize 14-milion year-old fossilized spider bunied in amber. Three phase separation in a Pringles chip: Imaged at high absorption and phase contrast,showing three phases. Chip 500μm Phase Contrast O ▣ For more information on Xradia's Suggested Reading unique technology,please scan here. The projection approximation and edge contrast for X-ray propagation-based phase contrast imaging of a cylindrical edge.KS Morgan,KKW Siu,DM Paganin(2010)Optical Express 18(8):9865-9878. 入xradia Xradia,Inc.4385 Hopyard Road,Pleasanton,CA 94588 下+1.925.701.3600 F:+1.925.730.4952 sales@xradia.com www.xradia.com The VersaXRM family of X. The UltraXRM family of 3D X-ray microscopes indudes the UitraXRM-L200 and UitraXRM-S for laboratory and synchrotron faciities,respectively. TN-P℃-0712
High Contrast for Difficult-to-Image Materials The Xradia VersaXRM family provides superior imaging in both absorption imaging mode and propagation-based phase contrast imaging mode. The imaging objectives in the X-ray microscope turret contain scintillators that are optimized by objective to provide the highest absorption contrast. The characteristic small detector pixel sizes of the XRM architecture coupled with flexible source and detector travel enables the user to optimize the propagation phase contrast effect. This approach enables imaging of features in materials that are traditionally considered “difficult-to-image,” such as soft biological tissues and polymers, or in samples composed of constituents that are of similar absorption contrasts. These include: Suggested Reading The projection approximation and edge contrast for X-ray propagation-based phase contrast imaging of a cylindrical edge. KS Morgan, KKW Siu, DM Paganin (2010) Optical Express 18(8):9865-9878. Tech Notes Xradia, Inc. 4385 Hopyard Road, Pleasanton, CA 94588 T: +1.925.701.3600 F: +1.925.730.4952 sales@xradia.com www.xradia.com Xradia is a registered trademark, and VersaXRM, UltraXRM, MicroXCT, Scout-and-Zoom, Scout-and-Scan, and PhaseEnhanced Optics are trademarks of Xradia, Inc. The VersaXRM family of X-ray microscopes includes the VersaXRM-500, MicroXCT-200 and MicroXCT-400 for 3D X-ray computed tomography. The UltraXRM family of 3D X-ray microscopes includes the UltraXRM-L200 and UltraXRM-S for laboratory and synchrotron facilities, respectively. TN-PC-0712 For more information on Xradia’s unique technology, please scan here. VersaXRM 200 µm Three phase separation in a Pringles chip: Imaged at high absorption and phase contrast, showing three phases. Air Absorption Contrast Phase Contrast Chip Oil 200 µm Unstained soft tissue: Phase contrast was employed to image unstained cartilage in a mouse knee. Porous polymer network: Phase and absorption contrast to obtain a high resolution image for quantification of pore size measurements, wallthickness measurements, and degree of interconnectivity. 750 µm 500 µm Spider: Phase contrast to visualize 14-million year-old fossilized spider buried in amber. Optimized Architecture = Superior Imaging
