Patent Application
20150226685
The subject matter disclosed herein relates to X-ray imaging. More particularly, the subject matter disclosed herein relates to systems and methods for detecting small angular changes in an X-ray beam caused by multiple refractions within an object by use of X-ray beams and selective angular alignment of the X-ray optics.
X-ray imaging has been used in a variety of fields for imaging objects. For example, X-ray imaging has been used extensively in the medical field for non-destructive testing and X-ray computed tomography (CT). Various other types of technology are also being used for medical imaging. For example, diffraction enhanced imaging (DEI) is an X-ray imaging technique that extends the capability of conventional X-ray imaging.
Diffraction enhanced imaging (DEI) is a phase contrast x-ray imaging modality. As with other phase contrast X-ray imaging modalities, DEI's image contrast is, in part, from the refraction of X-rays. In contrast, conventional X-ray imaging techniques measure only X-ray attenuation. DEI utilizes perfect crystal diffraction to convert small angular changes in the X-ray beam, caused by interactions within the imaging field, into large intensity changes in the final image.
The use of a silicon analyzer crystal in the path of the X-ray beam generates additional image contrast from X-ray refraction. DEI utilizes highly collimated X-rays prepared by X-ray diffraction from perfect single-crystal silicon. These collimated X-rays are of single X-ray energy, practically monochromatic, and are used as the beam to image an object.
Objects that have very little absorption contrast may have considerable refraction contrast, thus improving visualization and extending the utility of X-ray imaging. Applications of DEI techniques to biology and materials science have generated significant gains in both contrast and resolution, indicating the potential for use in mainstream medical imaging. An area of medicine where DEI may be particularly effective is in breast imaging for cancer diagnosis, where the diagnostic structures of interest often have low absorption contrast, making them difficult to see. Structures with low absorption contrast, such as the speculations extending from a malignant mass, have high refraction and ultra-small angle scatter contrast. It is desirable to provide a DEI system with the capability to increase both the sensitivity and specificity of X-ray-based breast imaging.
Multiple studies have demonstrated improved image contrast in both medical and industrial applications of DEI. Advantages of DEI systems over conventional X-ray imaging systems in the medical field include a dramatic reduction in patient radiation dose and improved image quality. The dose reduction is due to the ability of DEI systems to function at higher X-ray energies. X-ray absorption is governed by the photoelectric effect, Z2/E3, where Z is the atomic number and E is the photon energy.
A monoenergetic radiograph contains several components that can affect image contrast and resolution: a coherently scattered component IC, an incoherently scattered component II, and a transmitted component. X-rays passing through an object or medium where there are variations in density can be refracted, resulting in an angular deviation. Specifically, deviations in the X-ray range result from variations in pt along the path of the beam, where ρ is the density and t is the thickness. A fraction of the incident photons may also be diffracted by structures within an object, which are generally on the order of milliradians and referred to as small angle scattering. The sum total of these interactions contributed to the recorded intensity in a radiograph IN, which can be represented by the following equation:
I
N
=I
R
+I
D
+I
C
+I
I
System spatial resolution and contrast can be degraded by the contributions of both coherent and incoherent scatter. Anti-scatter grids are often used in medical imaging to reduce the contribution of scatter, but their performance is limited and use of a grid often requires a higher dose to compensate for the loss in intensity.
The DEI technique may utilize a silicon analyzer crystal in the path of the post-object X-ray beam to virtually eliminate the effects of both coherent and incoherent scatter. The narrow angular acceptance window of the silicon analyzer crystal may be referred to as its rocking curve or reflectivity profile, and is on the order of microradians for the X-ray energies used in DEI. The analyzer acts as an exquisitely sensitive angular filter, which can be used to measure both refraction and extinction contrast. Extinction contrast is defined as the loss of intensity from the incident beam due to scattering, which can produce substantial improvements in both contrast and resolution.
The Darwin Width (DW) is used to describe reflectivity curves, and is approximately the Full Width at Half Maximum (FWHM) of the reflectivity curve. Points at −½ DW and +½ DW are points on the curve with a steep slope, producing the greatest change in photon intensity per microradian for a particular analyzer reflection and beam energy. Contrast at the peak of the analyzer crystal rocking curve is dominated by X-ray absorption and multiple refraction (sometimes referred to as extinction), resulting in near scatter-free radiographs. Refraction contrast is highest where the slope of the rocking curve is greatest, at the −½ and +½ DW positions. One DEI based image processing technique uses these points to extract the contrast components of refraction and apparent absorption from these image pairs.
The following paragraph describes of this technique for extracting the contrast components of refraction and apparent absorption from an image pair. When the analyzer crystal is set to an angle representing +/−½ DW for a given reflection and beam energy, the slope of the rocking curve is relatively consistent and can be represented as a two-term Taylor series approximation as represented by the following equation:
If the analyzer crystal is set to the low-angle side of the rocking curve (−½ DW), the resulting image intensity can be represented by the following equation:
The recorded intensity for images acquired with the analyzer crystal set to the high-angle position (+½ DW) can be represented by the following equation:
These equations can be solved for the changes in intensity due to apparent absorption (IR) and the refraction in angle observed in the z direction (ΔθZ) represented by the following equation:
These equations can be applied to the high and low angle images on a pixel-by-pixel basis to separate the two contrast elements into what is known as a DEI apparent absorption and refraction image. However, it is important to note that each of the single point rocking curve images used to generate DEI apparent absorption and refraction images is useful.
Development of a clinical DEI imager may have significance for women's health and medical imaging in general for the following reasons: (1) DEI has been shown to produce very high contrast for the features that are most important to detection and characterization of breast cancer; (2) the physics of DEI allows for imaging at higher x-ray energies than used with absorption alone; and (3) the ability of DEI to generate contrast without the need of photons to be absorbed dramatically reduces ionization, and thus reduces the absorbed dose.
Current DEI and DEI imaging processing techniques are based heavily on conventional imaging theory and rely, at least in part, on X-ray absorption for image generation. Thus, objects imaged using these techniques absorb radiation. Such radiation exposure is undesirable in applications for medical imaging given concerns of dose, and this reasoning places considerable engineering limitations that make clinical and industrial translation challenging. Thus, it is desirable to provide DEI and DEI techniques that produce high quality images and that rely less on absorption but produce images with improved, or at least equivalent, diagnostic quality and feature visualization. In addition, it is desirable to reduce DEI imaging time, which can be affected by the significant reduction of beam flux in DEI monochromators.
Accordingly, in view of desired improvements associated with DEI and DEI systems, there exists a need for improved DEI and DEI systems and related methods for detecting an image of an object.
Systems and methods for detecting a small angular changes in an x-ray beam caused by multiple refractions within an object by use of X-ray beams and selective angular alignment of the x-ray optics.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.
According to one embodiment, a method for detecting an image of an object includes providing a single X-ray source. The method further includes generating a first X-ray beam using the single X-ray source. The method also includes positioning a plurality of monochromator crystals to intercept the first X-ray beam such that a plurality of second X-ray beams each having predetermined energy level, is produced. The method further includes positioning an object in paths of the plurality of second X-ray beams for transmission of the plurality of second X-ray beams through the object and emitting from the object a plurality of transmitted X-ray beams. The method further includes directing the plurality of transmitted X-ray beams at angles of incidence upon a plurality of analyzer crystals, wherein the angles of incidence of the analyzer crystals are independently adjustable. The method further includes detecting an image of the object from each of the X-ray beams diffracted from each analyzer crystal using a plurality of detectors.
According to another embodiment, the plurality of detectors comprise at least one high spatial resolution detector and at least one low spatial resolution detector.
According to another embodiment, the low spatial resolution detector is an energy-resolving detector.
According to another embodiment, further including adjusting the angles of incidence of the analyzer crystals, and detecting a plurality of images of the object during adjustment of the angles of incidence of the analyzer crystals.
According to another embodiment, directing the plurality of transmitted X-ray beams comprises directing the rotation of the analyzer crystals about a propagation direction of the transmitted X-ray beams relative to the analyzer crystal.
According to another embodiment, detecting an image of the object comprises tilting the analyzer crystal out of alignment by a predetermined chi-angle; and the method further includes detecting a plurality of images of the object in sequence for a range of theta-angular positions of the analyzer crystals.
According to another embodiment, further including using the detectors to measure the intensity of the diffracted X-ray beam.
According to another embodiment, further including using the measured intensity of the diffracted X-ray beam to determine the degree of anisotropy in a structure of the object.
According to another embodiment, further including using the measured intensity of the diffracted X-ray beam to determine the orientation direction of structures in the object.
According to another embodiment, measuring the intensity of the diffracted X-ray beam comprises detecting a plurality of intensity measurements for a range of angular positions of the analyzer crystal.
According to another embodiment, the range of angular positions is a range of angles the X-ray source is rotated about the propagation direction of the X-ray beam relative to the analyzer crystals.
According to another embodiment, the range of angular positions is a range of angles the object is rotated about the propagation direction of the X-ray beam relative to the analyzer crystals.
According to another embodiment, further including using the series of intensity measurements to determine the degree of anisotropy in the structure of the object.
According to another embodiment, further including using the series of intensity measurements to determine the orientation direction of the structures in the object.
According to another embodiment, measuring the intensity of the diffracted X-ray beam comprises tilting the crystal analyzer out of alignment by a predetermined angle; and wherein the method further comprises detecting a series of intensity measurements are obtained for a range of angular positions of the analyzer crystal.
According to another embodiment, further including using the plurality of intensity measurements to determine the maximum and minimum reflectivity profile widths.
According to another embodiment, a system for detecting an image of an object includes a single X-ray source configured to generate a first X-ray beam. The system also includes a plurality of monochromator crystals positioned to intercept the first X-ray beam such that a plurality of second X-ray beams each having predetermined energy level, is produced. The system also includes a plurality of analyzer crystals positioned to intercept a plurality of transmitted X-ray beams at an angle of incidence from the object, wherein the plurality of transmitted X-ray beams are emitted from the object positioned in the path of the plurality of second X-ray beams, and wherein the angles of incidence of the analyzer crystals are independently adjustable. The system also includes a plurality of detectors configured to detecting an image of the object from each of the transmitted X-ray beams diffracted from each analyzer crystal.
According to another embodiment, the plurality of detectors comprise at least one high spatial resolution detector and at least one low spatial resolution detector.
According to another embodiment, the low spatial resolution detector is an energy-resolving detector.
According to another embodiment, further includes the plurality of detectors configured to adjust the angles of incidence of the analyzer crystals, and detect a plurality of images of the object during adjustment of the angles of incidence of the analyzer crystals.
According to another embodiment, the analyzer crystals are configured to rotate about a propagation direction of the transmitted X-ray beams relative to the analyzer crystal for directing the angles of incidence of the plurality of transmitted X-ray beams.
According to another embodiment, the system is configured to tilt the analyzer crystal out of alignment by a predetermined chi-angle; and the detectors are further configured to detect a plurality of images of the object in sequence for a range of theta-angular positions of the analyzer crystals.
According to another embodiment, the detectors are further configured to measure the intensity of the diffracted X-ray beam.
According to another embodiment, the detectors are further configured to determine the degree of anisotropy in a structure of the object based on the measured intensity of the diffracted X-ray beam.
According to another embodiment, the detectors are further configured to determine the orientation direction of a structure in the object based on the measured intensity of the diffracted X-ray beam.
According to another embodiment, measuring the intensity of the diffracted X-ray beam comprises detecting a plurality of intensity measurements for a range of angular positions of the analyzer crystal.
According to another embodiment, the range of angular positions is a range of angles the X-ray source is rotated about the propagation direction of the X-ray beam relative to the analyzer crystals.
According to another embodiment, the range of angular positions is a range of angles the object is rotated about the propagation direction of the X-ray beam relative to the analyzer crystals.
According to another embodiment, the detectors are further configured to determine the degree of anisotropy in a structure based on the plurality of intensity measurements.
According to another embodiment, the detectors are further configured to determine the orientation direction of the structure in the object based on the plurality of intensity measurements.
According to another embodiment, measuring the intensity of the diffracted X-ray beam comprises the analyzer crystals further configured to be tilted out of alignment by a predetermined angle; and the detectors are further configured to detect a plurality of intensity measurements for a range of angular positions of the analyzer crystals.
According to another embodiment, the detectors are further configured to determine the maximum and minimum reflectivity profile widths using the plurality of intensity measurements.
The foregoing summary, as well as the following detailed description of various embodiments, is better understood when read in conjunction with the drawings provided herein. For the purposes of illustration, there is shown in the drawings exemplary embodiments; however, the presently disclosed subject matter is not limited to the specific methods and instrumentalities disclosed. In the drawings:
The presently disclosed subject matter is described with specificity to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different steps or elements similar to the ones described in this document, in conjunction with other present or future technologies. Moreover, although the term “step” may be used herein to connote different aspects of methods employed, the term should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except when the order of individual steps is explicitly described.
The subject matter described herein discloses improved diffraction enhanced imaging (DEI) and DEI systems and related methods for detecting images with multiple refractions from an object.
Referring to
Referring to
In the example illustrated by
Referring now to
φ′−φ=Δφ=Δθ Equation 1
Where φ is the Bragg angle for the diffraction peak, φ′ is the new angle with respect to diffraction plane, and Δθ is the change in the θ 300 angle with respect to the Bragg diffraction peak. Thus, DEI is most sensitive to changes in this the angle, θ 300. Conversely, an intrinsic reflectivity profile taken by changing the angle χ 304 of the analyzer crystal 302 could be much wider, since tilting the diffraction plane by the angle χ 304, only changes the angle of the X-ray beam with respect to the diffraction plane by a small amount denoted in Equation 2,
Δφ=φ′−φ=sin−1(sin Ø cos Δχ)−φ Equation 2
where φ and φ′ are as described above and Δχ is the change in the χ 304 angle with respect to the Bragg diffraction peak. Small changes in φ, will require significantly larger changes in χ 304.
As an example, when an object is placed in the path of the X-ray beam, the object may refract the X-ray beam. The change in angle (resulting from the refraction of the beam) can be broken down into its x- and z-components (
Referring to
Referring to
The amount of angular diffusion of the beam and angular shape of the beam diffusion are a function of the difference in index of refraction between the refracting structures and the bulk matrix in which the structures reside, the energy of the X-ray beam, and the shape and angular orientation of the structures with respect to the X-ray beam. The shape and the angular orientation of the structures and microstructures can be indicative of the strength, porosity, and fracture resistance of the object.
As an example, in young, healthy individuals, the trabeculae in their vertebrae are largely isotropic. In aged, osteoporotic individuals, the trabeculae transition from largely isotropic to largely anisotropic, with the trabeculae aligning with the axis of the spine. Thus, for someone at risk of developing osteoporosis, the degree of anisotropy within the vertebrae can be monitored with this new approach and a fracture risk stratification measure can be implemented with this approach.
Referring now to
Referring to
To implement either of the above cases, it is possible to first align the analyzer and monochromator crystals to be parallel, and then slightly misalign the analyzer crystal's χ-angle by a predetermined amount. The amount of χ-misalignment can be determined by a combination of the size of the pixels and the size-scale over which the multiple refraction signal remains constant. After misaligning χ, and before putting an object in the X-ray beam, a high angular resolution reflectivity profile, R(θ) may be obtained. For each point in the slot x-ray beam, the reflectivity profile may be fit to a curve (for example, a Gaussian), and the peak reflectivity position may be determined. This peak reflectivity as a function of position in the slot beam may serve as a lookup map for the subsequent reflectivity profiles. This approach may yield an accurate measure for the peak θ-position of the reflectivity profile.
As an example of the Case A1700, if a feature of interest is at least 4 pixels wide, χ may be misaligned such that the peak θ-position of the analyzer crystal corresponds to N microradians for pixel one 704, N+0.025 microradians for pixel two 706, N+0.05 microradians for pixel three 708, and N+0.075 microradians for pixel four 710. If images are then obtained for every 0.1 microradians in θ, then the values from each pixel can be used to improve the theta angular resolution to 0.025 microradians. Thus, in this example, Case A1700 provides a factor of 4× improvement in the angular resolution of the DEI system and reduces the error in measuring the width of the reflectivity profile.
As another example, Case A2702 may have a feature of interest that is at least 4 pixels wide, χ may then be misaligned such that the peak θ-position of the analyzer crystal corresponds to N microradians for pixel one 712, N+0.1 microradians for pixel two 714, N+0.2 microradians for pixel three 716, and N+0.3 microradians for pixel four 718. If images are then obtained for every 0.4 microradians in theta, then the full reflectivity profile can be measured using four times fewer analyzer crystal θ-positions than a comparable angular resolution reflectivity profile obtained with an aligned chi-angle. This can reduce the acquisition time for a reflectivity profile by a factor of 4.
Case A1700 and A2702 may also be combined, for example, the feature of interest is 4 pixels wide, the χ could be misaligned such that the peak θ-position of the analyzer crystal corresponds to N microradians for pixel one, N+0.05 microradians for pixel two, N+0.1 microradians for pixel three, and N+0.15 microradians for pixel four. If images are then obtained for every 0.2 microradians in theta, then the full reflectivity profile can be measured with twice the initial (no χ-detuning) angular resolution while still reducing the acquisition time by a factor of 2.
With continued reference to
According to another aspect, the subject matter described herein can include a method for simultaneous acquisition of DEI reflectivity profiles at multiple X-ray energies. For a typical reflectivity profile, the monochromator and analyzer crystal can be set to the correct angle to reflect the X-rays that have the energy of the Kα1 and Kα2 emission lines of the x-ray tube source. While typically only the energies of the Kα1 and Kα2 emission lines are considered, the X-ray optics also can diffract x-rays with energies that correspond to the harmonic diffraction peaks. For example, if the silicon [333] plane of the monochromator/analyzer crystals are angled to diffract the Kα1/2 emission lines of tungsten, then the diffracted beam can also include X-ray with energies corresponding to the [111], [444], [555], etc. diffraction peaks for same angle as the 59.312 keV [333] diffraction peak. Thus, the diffracted x-ray beam can include bremsstrahlung photons of 59.312/3=19.77 keV (corresponding to the [111] diffraction peak), 59.312*4/3=79.083 keV (corresponding to the diffraction peak), and 59.312*5/3=98.853 (corresponding to the [555] diffraction peak). Because the brightness of the X-ray beam at the bremsstrahlung-only X-ray energies is already much lower than the brightness of the X-ray beam at the Kα1 and Kα2 energies, the lower energy (lower order harmonic), in this case just the 19.77 keV, [111] diffraction peak, may be attenuated out of the transmitted beam. The higher-order harmonics have higher energy than the Kα1 and Kα2 beams, and therefore will more readily transmit through the object in the imaging field. If an energy-resolving detector is used to obtain the DEI images, then reflectivity profiles corresponding to each of the [333], and [555] diffraction peaks can simultaneously be measured.
The width of the reflectivity profile is related to the number of refracting structures along the beam path, but the area under the reflectivity profile curve is related to total attenuation of the x-ray beam as it passes through object. If the attenuation of an X-ray beam is measured for two or more x-ray energies, then the object attenuation may be decomposed into a superposition of two attenuating materials (i.e. soft tissue and calcium). Through this decomposition of material, we can determine the amount of each of the attenuating material along the beam path. This is the same principal that is employed in dual-energy X-ray absorptiometry (DXA) for the measurement of bone mineral density.
This system is unique from existing D×A systems because the analyzer crystal absorbs the vast majority of scattered x-rays, which will increase the accuracy of the measurements for each energy. The major advancement over existing technology is that these systems and methods can allow for the simultaneous measurements of DXA and of microstructure along the beam path, thereby providing information both about the chemical composition of the object and information about the structural and microstructural properties of the object.
The reflectivity profile may have clinical utility because the width of the reflectivity profile is proportional to the number of refracting microstructures along the X-ray beam path. This may prove to be a diagnostically important measure for lungs and bone. In lungs, the collapse of alveoli in an injured lung region can lead to a reduced reflectivity profile width. In bone, degradation of microstructure corresponds to fracture risk, so a measure of bone microstructure will improve clinicians' ability to assess fracture risk. Simultaneous DXA and reflectivity profile widths can be important because it can provide information both about the chemical composition of the object and information about the structural and microstructural properties of the object. Beyond clinical utility of this approach, this can be used for industrial inspection or other scenarios in which it may be advantageous to know how much microstructure is present can benefit greatly.
According to another aspect, the subject matter described herein can include systems and methods for measuring the orientation direction and the degree of anisotropy in an object with multiple refracting structures. When an object with many structures is placed in the imaging field, the x-ray beam may be angularly diffused by the x-ray beam. The amount of angular diffusion of the beam and angular shape of the beam diffusion are a function of the difference in index of refraction between the refracting structures and the bulk matrix in which the structures reside, the energy of the X-ray beam, and the shape and angular orientation of the structures with respect to the X-ray beam.
Referring to
In Case B1802, if an X-ray beam passes through an array of spheres that differ in index of refraction from the bulk medium, then the X-ray beam will be diffused about its straight-line path. For randomly placed spheres along the beam path, the diffusion can have a Gaussian distribution, centered on the straight-line path and symmetric in angle about the straight-line path.
In Case B2804, if an X-ray beam passes through an array of cylinders that are each randomly aligned (fully isotropic) and differ in index of refraction from the bulk medium, then the X-ray beam will be diffused about its straight-line path, the diffusion may have a Gaussian distribution, centered on the straight-line path and symmetric in angle about the straight-line path.
In Case B3806, if an X-ray beam passes through an array of cylinders that are aligned parallel to one another (fully anisotropic) and differ in index of refraction from the bulk medium, then the x-ray beam will be diffused about its straight-line path, but that angular diffusion may only be non-zero in the plane perpendicular to the axis of the cylinders.
In present disclosure, systems and methods are provided for measuring the anisotropy and preferred angular orientation of structures through selective acquisition of DEI data.
Returning to Case B3806 above, if the object was placed in the DEI X-ray beam such that the aligned axis of the cylinders was along an arbitrary direction in the plane perpendicular to the propagation direction of the center of the X-ray beam, then the measured reflectivity profile of the transmitted DEI beam, Rt(θ), can have a width, W, between a minimum of the intrinsic reflectivity profile width (the angular diffusion is fully misaligned to DEI's direction of sensitivity) and a maximum the convolution of the intrinsic reflectivity profile width with the angular diffusion map in Case B3806 (the angular diffusion direction is aligned to DEI's sensitivity direction).
The next step is to rotate either the object or the DEI system about the center line of the beam propagation direction by an angle, a, and then to measure the reflectivity profile width again. The change in angle can be achieved either by rotating the DEI optical system or by rotating the object in the imaging field. Again, the measured reflectivity profile of the DEI X-ray beam may be between a minimum of the intrinsic reflectivity profile width (the angular diffusion is fully misaligned to DEI's direction of sensitivity) and a maximum the convolution of the intrinsic reflectivity profile width with the angular diffusion map in Case B3806 (
With continued reference to
If W(α) were to be measured as above for Case B1802 and B2804, it would be noted that W is independent of α. For fully isotropic structures, W will not vary as a function of α. Many naturally occurring objects have cylinder-like structures or microstructures that reside on the continuum between Cases B2804 (angular orientation of the structures is fully isotropic) and B3806 (angular orientation of the structures is fully anisotropic). The degree of anisotropy (DA) can be calculated as:
DA has a value of zero, when Wmin=Wmax, to a maximum of one, when Wmax>>Wmin.
For example, there are rod-like trabeculae in trabecular bone, the rods preferentially align along the direction of load on the bone at that location, but the rods are not fully aligned. In this example, the rod-like trabeculae are slightly anisotropic (more similar to Case B2804 than Case B3806), thus W may vary as a function of α, but the maximum reflectivity profile width will be greater than, but not much, much greater than, the minimum measured reflectivity profile width (Wmax is greater than Wmin, but Wmax is not much, much greater than Wmin). In this case, the DA will approach zero as Wmax approaches Wmin.
In this example, in regions where the load on the trabecular bone is uniform, then there is no preferred orientation direction for the trabeculae, and the maximum and minimum widths may be approximately equal, and both may be greater than the intrinsic width (Wmax≅Wmin>Wint). In this case, the DA may be close to zero.
While the above example cases only consider a single width measurement for each angle, α, reflectivity profile width images can be measured for each angle, α. Once the individual images are registered to one another (co-registered), the degree of anisotropy and the orientation direction (the value of α where W(α) is minimized) can be measured on a pixel-by-pixel basis in the image. Thus, with this novel method, the degree of anisotropy and the preferred angular orientation direction can be mapped within an object.
Referring now to
Referring again to
The monochromator crystals MC-1-MC-n can be configured to select a predetermined energy of a portion of X-ray beams XB1 incident thereon. In one example, a monochromator crystal is a silicon [333] monochromator crystal adapted to reject the majority of photons of its respective X-ray beams that do not have a desired energy. For the case of a tungsten X-ray tube, there can be a range of beam energies that are reflected by the silicon monochromator crystal. In this case, the characteristic emission lines of the X-ray beams are 59.13 keV (Kα1) and 57.983 (Kα2), and the Bremsstrahlung radiation that falls within the narrow angular acceptance window of the monochromator crystal. The brightness of the bremsstrahlung radiation is several orders of magnitude less than the two Kα emission lines.
An X-ray beam may be scattered by its respective monochromator crystal in several different directions. Another array of collimators (not shown) may be positioned between the monochromator crystals MC-1-MC-n and the object O for blocking a portion of the X-ray beam that falls outside an angular acceptance window of its corresponding analyzer crystal, one of analyzer crystals AC-1-AC-n. Each collimator can define a slit or hole through which a portion of one of the X-ray beams can pass towards its analyzer crystal for interception by the analyzer crystal.
The analyzer crystals AC-1-AC-n can be rotated for measuring the amount of radiation traveling in a particular direction. The angular reflectivity function of the crystal system is called the intrinsic rocking curve, and this property is used to generate image refraction contrast. If an X-ray photon is deviated towards the peak of the rocking curve, its reflectivity, and thus intensity will increase. If an object feature causes a photon to be deflected down the rocking curve, or away from the peak reflectivity position, it will cause a reduction in intensity.
A sample or object O can be imaged in air or immersed in a coupling medium, such as water. The use of a coupling medium can be used to reduce the index gradient between the air and the object O to be imaged, thus allowing the incident X-rays to pass into the object without experiencing significant refraction at the air-object interface. This is not necessary for most objects, but it is an application of the DEI method and can be used to improve the internal contrast of an object.
In one example, a monochromator crystal is a symmetric crystal which is narrow in one dimension. A symmetric crystal's lattice planes (the atomic layers that contribute to diffracting the X-ray beam) are parallel to the surface of the crystal. A symmetric crystal preserves the vertical height of the corresponding X-ray source in the incoming beam. In comparison, an asymmetric crystal modifies the divergence and size of the incoming beam. In this example of a monochromator crystal being a symmetric crystal, two-dimensional imaging of large imaging fields (e.g., imaging fields of about 25 cm by 20 cm) can be achieved by scanning a sample object and a detector using a symmetric crystal. One exemplary advantage of a symmetric crystal over an asymmetric crystal is that the asymmetric crystal requires a large monochromator crystal to prepare the imaging beam (e.g., selecting and collimating X-rays), imposing a severe limitation on the perfection of the large crystal. Further, the size of an asymmetric crystal increases with increasing X-ray beam energy, thus making it impractical for X-rays of about 59.13 keV. In contrast, for example, a symmetric monochromator crystal used in accordance with the subject matter described herein can utilize 59.13 keV X-rays with a modest sized crystal of about 30 mm in length. An advantage, over single-beam DEI, of the system and methods proposed disclosed herein, with multiple sources, is that this scan range can be greatly reduced, because of much better spatial coverage of the beams (i.e. if you have a required 25 cm scan range, and 10 beams, then the object will only have to be scanned through a range of 2.5 cm).
Referring again to
The electrical signals can be communicated to a computer C for image analysis and display to an operator. The computer C can be configured to generate an absorption image, an image showing refraction effects, and an image depicting ultra-small-angle scattering, the types of which are described in more detail below.
The monochromator crystals can propagate their respective x-ray beams as a horizontally-divergent (
Referring now to
Collimator C2 is positioned in a path of emission lines Kα1 K1 and Kα2 K2. Collimator C2 defines an adjustable slit through which emission lines can be selectively passed towards analyzer crystal AC. In the first operational mode shown in
Referring now to
Further, in one embodiment of using the second mode, the Bremsstrahlung radiation at x-ray energies that are different from the K alpha lines can be captured. Thus, in this embodiment, the system is tunable in x-ray energy and is not limited to the characteristic emission energies. This functionality can be achieved by changing the incident angle of the monochromator crystal and the analyzer crystal. In one example, this functionality can be achieved by changing the incident angle to 11.4 degrees, following the Bragg's law, and replacing the Copper filter with an Aluminum filter. In this example, imaging can occur at 30 keV x-ray energy. X-ray energies lower than the Tungsten emission line energies can be utilized for relatively thin objects.
In one example, the copper filter can be configured to remove about 19 keV bremsstrahlung radiation for reducing or eliminating unwanted crystal reflections and harmonics. Images have the potential to be degraded without this filtering.
The DEI system 900 can include right and left post-analyzer crystal sodium iodide detectors D1 and D2, respectively, and right and left post-monochromator crystal sodium iodide detectors D3 and D4, respectively. Detectors D3 and D4 are used to ensure alignment of the monochromator crystals (MC) and detectors D1 and D2 are used to ensure analyzer crystal (AC) alignment. These detectors are used to measure the intensity of the diffracted X-ray beam being emitted from the monochromator crystal MC, or the analyzer AC. For system alignment, detectors D1 and D2 are placed in the post analyzer crystal AC X-ray beam XB. If the analyzer crystal is not tuned to the desired angle, the intensity measured by the detectors D1 and D2 will show this and the system can be adjusted. The same is true for the detectors in the post-monochromator crystal MC X-ray beam XB. In addition, detectors D1-D4 can be used to measure X-ray beam XB in real time and adjust the analyzer crystal, D1 and D2, chi (angle as measured about the axis along the X-ray beam path) or monochromator crystal chi, D3 and D4. The use of these detectors to set, measure, and adjust the analyzer crystal AC and monochromator crystal MC can be important for successful DEI image acquisition.
Referring now to
Referring now to
The DEI system 1400 shown in
Referring now to
According to one aspect, the subject matter described herein can include a method for detecting an image of an object by providing a plurality of small area sources. A plurality of first X-ray beams can be generated by using the small area sources. A plurality of monochromator crystals can be positioned to intercept the plurality of first X-ray beams such that a plurality of second X-ray beams each having predetermined energy levels is produced. Further, an object to be imaged can be positioned in paths of the second X-ray beams for transmission of the second X-ray beams through the object and emitting from the object a plurality of transmission X-ray beams. The X-ray beams may be directed at angles of incidence upon a plurality of analyzer crystals. Further, an image of the object can be detected based upon beams diffracted from the analyzer crystals. These systems and methods can be advantageous, for example, because they can provide extremely low dose in medical applications, fast scan times, high resolution, and relatively low operation and build costs. Further, for example, these systems can be constructed into a compact unit and be readily usable in clinical and industrial applications. Additional description about these systems and related methods are described in further detail herein.
Referring now to
System 1600 includes a plurality of digital detectors DD-1-DD-n each configured to receive respective, diffracted X-ray beams DXB-1-DXB-n from the analyzer crystal sets AC-1-AC-n. Computer C is operable to receive electrical signals from the digital detectors DD-1-DD-n for generating an image of the object O.
Referring now to
Referring now to
Referring now to
In step 2002, a plurality of first X-ray beams may be generated using the small area sources. For example, the small area sources S of the X-ray tubes XT-1-XT-N shown in
A plurality of monochromator crystals, such as the monochromator crystals MC-1-MC-n shown in
In step 2006, an object can be positioned in the paths of the second X-ray beams for transmission of the second X-ray beams through the object and emission from the object a plurality of transmission X-ray beams. For example, the object O shown in
In step 2008, the transmitted X-ray beam can be directed at angles of incidence upon analyzer crystals. For example, analyzer crystals AC-1-AC-n shown in
In step 2010, an image of object O can be detected from the beams diffracted from the analyzer crystal AC-1-AC-n. For example, detector DD can detect the diffracted beam from the analyzer crystals. The diffracted beams can be detected by one of the following exemplary detectors: a detector configured to digitize a detected image; a radiograph film; and an image plate. In one example, the image of an object can be detected from beam diffracted from analyzer crystals at a peak of a rocking curve of the analyzer crystals and/or near a peak of a rocking curve of the analyzer crystals. The detected image can be processed and presented to a user via a display of a computer.
It is noted that a DEI system, such as the system shown in
In step 2204, the second sides S2 of the monochromator crystals MC1-MC-n are positioned to intercept the second X-ray beams XB2 for producing the third X-ray beams, generally designated XB3. An object O can be positioned in the paths of the third X-ray beams XB3 for transmission of the third X-ray beams XB3 through the object and emission from the object transmission X-ray beams (step 2206).
In step 2208, the transmitted X-ray beams can be directed at angles of incidence upon the analyzer crystals AC1-AC-n. Further, in step 2210, an image of the object can be detected from the diffracted X-ray beams DXB.
In another example of detecting the image of the object, a first angle image of object can be detected from first diffracted beams emitted from analyzer crystals positioned at a first angular position. The first angle image of the object can be detected at a low rocking curve angle setting of the analyzer crystals. Further, a second angle image of the object can be detected from a second diffracted beam emitted from analyzer crystals positioned at a second angular position. The second angle image of the object can be detected at a high rocking curve angle setting of the analyzer crystals. The first and second angle images can be combined by a computer to derive a refraction image and apparent absorption image. Further, the computer can derive a mass density image of the object from the refraction image. The mass density image can be presented to a user via a display of the computer.
In another embodiment, a DEI system in accordance with the subject matter described herein can include a mismatch crystal design for rejecting particular X-rays emitted by an X-ray tube. In this design, the Kα2 emission line of the X-ray beam can be eliminated at the monochromator. A collimator can be positioned for blocking a portion of an X-ray beam that fall outside an angular acceptance window of a first set of monochromator crystals, such as, for example, one of monochromator crystals MC1-1-MC1-n shown in
The monochromator crystals of the first and second sets can be configured in a mismatch crystal design for rejecting particular X-ray beams emitted by source points, such as small area sources of an X-ray tube. The monochromator crystals can be used to eliminate the Kα2 emission line of the X-ray beam, which can be achieved by utilizing the angular acceptance versus energy for different crystals. In one example, the monochromator crystals can be germanium [333] and silicon [333] monochromator crystals, respectively.
In another example of detecting the image of the object, first angle image of an object can be detected from first diffracted beams emitted from analyzer crystals positioned at first angular positions. The first angle image of an object can be detected at a low rocking curve angle setting of the analyzer crystals. Further, a second angle image of the object can be detected from second diffracted beams emitted from analyzer crystals positioned at second angular positions. The second angle images of the object can be detected at a high rocking curve angle setting of the analyzer crystals. The first and second angle images can be combined by a computer to derive a refraction image. Further, the computer can derive a mass density image of the object from the refraction image. The mass density image can be presented to a user via a display of the computer.
In step 2406, an object O can be positioned in the paths of the second X-ray beams XB2 for transmission of the second X-ray beams XB2 through the object and emission from the object transmission X-ray beams.
In step 2408, the transmitted X-ray beams XB2 can be directed at angles of incidence upon the analyzer crystals AC1-AC-n generating third X-ray beams, XB3. Each analyzer crystal AC1-AC-n may be independently controlled in angles theta and chi. The analyzer crystals AC and third X-ray beams XB3 are divided into two groups: Analyzer crystals AC-H may be angled such that they diffract X-ray beams XB3H, these X-ray beams, XB3H are incident on high spatial resolution detectors DH; and Analyzer crystals ACL may be angled such that they diffract X-ray beams XB3L, these X-ray beams XB3L are incident on low spatial resolution detectors DL. In step 2410A, the analyzer crystals AC-H may be each rotated to the same angle theta TH prior to imaging. The analyzer crystals AC-H may each remain at the angle TH and an image of the object can be detected from the diffracted X-ray beams DXB-H. In step 2410B, the analyzer crystals AC-H may be each rotated to the same angle theta TH prior to imaging. The analyzer crystals AC-L may be cycled through a range of angles TL-1-TL-N, with respect to the Bragg diffraction peak, for each position as the object is scanned. A low spatial resolution image of the object can be detected from the diffracted X-ray beams DXB-L for each analyzer crystal angle TL-1-TL-N.
In step 2412, corresponding pixels from the series of images at analyzer crystal angles TL-1-TL-N can then be used to generate reflectivity profiles for each spatial position of the object. In one example, the reflectivity profile at each point could be fit to a Gaussian and a new image could be generated where each pixel represents the width of the Gaussian at each position in the object. In another example, the sum across all of the images TL-1-TL-N could be calculated for each pixel, and a new image can be generated that represents this sum over the reflectivity profile.
In step 2414, the generated low spatial resolution image(s) (2410B) from the reflectivity profile can be co-registered to the high spatial resolution image (2410A) and the images can be displayed together. In one example, the high spatial resolution image can be displayed in gray-scale and the low spatial resolution can be displayed in color with an opacity of less than 100%.
In another example of detecting the high spatial resolution image of the object, a first angle image of object can be detected from first diffracted beams emitted from analyzer crystals positioned at a first angular position. The first angle image of the object can be detected at a low rocking curve angle setting of the analyzer crystals. Further, a second angle image of the object can be detected from a second diffracted beam emitted from analyzer crystals positioned at a second angular position. The second angle image of the object can be detected at a high rocking curve angle setting of the analyzer crystals. The first and second angle images can be combined by a computer to derive a refraction image and apparent absorption image. Further, the computer can derive a mass density image of the object from the refraction image. The mass density image can be presented to a user via a display of the computer.
In step 2504, an object O can be positioned in the paths of the second X-ray beams XB2 for transmission of the second X-ray beams XB2 through the object and emission from the object transmission X-ray beams.
In step 2506, the transmitted X-ray beams XB2 can be directed at angles of incidence upon the analyzer crystal or crystals AC1-AC-n generating third X-ray beams, XB3. Each analyzer crystal or crystals AC1-AC-n can be independently controlled in angles theta and chi.
In step 2508, for a single analyzer crystal angle, the third x-ray beam XB3 can be detected by an x-ray detector to generate an image of the object.
In step 2510, the analyzer crystal can be rotated about the theta angle by a predetermined amount (e.g., on the order of tenths of microradians to microradians), and another image of the object can be detected. This can be repeated at least twice until a set of reflectivity profile images is generated.
In step 2512, one of either the object or the DEI optical system is rotated about the axis of the beam-propagation direction (
In step 2514, the widths of the reflectivity profile from each pixel in each set of reflectivity profile images can be mathematically determined. In one example, the width is measured by fitting the reflectivity profile to a Gaussian. Once this step is completed, there will be an image of the reflectivity profile width of the object for each object orientation.
In step 2516, images of the reflectivity profile widths can be each rotated, such that the images are co-registered. These set of co-registered images then represent a map of the reflectivity profile width as a function of orientation angle of the object.
In step 2518, the maximum and minimum value of the reflectivity profile width can be found for each location in the object and in the imaging field. As an example, the system may use the plurality of intensity measurements to determine the maximum and minimum reflectivity profile widths.
In step 2520, the maximum and minimum values of the reflectivity profile can be mathematically compared to determine the degree of anisotropy in the microstructures within the object.
Referring to
In step 2704, an object O can be positioned in the paths of the second X-ray beams XB2 for transmission of the second X-ray beams XB2 through the object and emission from the object transmission X-ray beams.
In step 2706, the transmitted X-ray beams XB2 can be directed at angles of incidence upon the analyzer crystal or crystals AC1-AC-n generating third X-ray beams, XB3. Each analyzer crystal or crystals AC1-AC-n be independently controlled in angles theta and chi.
In step 2708, for a single analyzer crystal angle, the third x-ray beam XB3 can be detected by an energy resolving x-ray detector to generate an image of the object. In one example, separate images are detected for each of the X-ray energies corresponding to the [333], [444] and [555] reflections.
In step 2710, the analyzer crystal is rotated about the theta angle by a predetermined amount (e.g., on the order of tenths of microradians to microradians), and another set of energy-resolved images of the object are detected. In one example, a set of reflectivity profile images can be generated for each of the X-ray energies corresponding to the [333], [444], and [555] reflections.
In step 2712, the sum of all of the values across the reflectivity profiles and the widths of the reflectivity profiles from each pixel in each set of reflectivity profile images for each X-ray energy can be mathematically determined. Once this step can be completed, there may be an image of the sum over the reflectivity profile for each energy of the X-ray beam and an image of the reflectivity profile width for each energy of the X-ray beam. In one example, the sum over the reflectivity profiles and reflectivity profiles widths for the X-ray energies corresponding to the [333], [444] and [555] reflections may be separately determined.
In step 2714, the sum over the reflectivity profiles for each energy may be used to quantify the differential absorption at the different X-ray energies through dual-energy X-ray absorptiometry. In one example, the amount of mineral content in the object can be quantified.
In step 2804, an object O can be positioned in the paths of the second X-ray beams XB2 for transmission of the second X-ray beams XB2 through the object and emission from the object transmission X-ray beams.
In step 2806, the transmitted X-ray beams XB2 can be directed at angles of incidence upon the analyzer crystal or crystals AC1-AC-n generating third X-ray beams, XB3. Each analyzer crystal or crystals AC1-AC-n can be independently controlled in angles theta and chi.
In step 2808, the analyzer crystal or crystals AC1-AC-n may be tilted in angle chi by a predetermined angle with respect to the peak reflectivity angle (in chi).
In step 2810, for a single theta angle for each analyzer crystal, the third x-ray beam XB3 can be detected by an x-ray detector to generate an image of the object.
In step 2812, the analyzer crystal can be rotated about the theta angle by a predetermined amount (typically on the order of tenths of microradians to microradians), and detect images of the object. This can be repeated at least twice until sets of reflectivity profile images are generated for the X-ray beam.
In step 2814, the sum of all of the values across the reflectivity profiles and the widths of the reflectivity profiles from each pixel in each set of reflectivity profile images can be mathematically determined. In one example, the width is measured by fitting the reflectivity profile to a Gaussian. Once this step is completed, there will be an image of the sum over the reflectivity profile of the X-ray beam and an image of the reflectivity profile width of the X-ray beam. In another example, steps 2806 to 2814 may be executed with no object in the X-ray beam in order to determine the theta angle of the peak reflectivity as a function of position in the chi-angle-detuned X-ray beam. With this map of relative theta-angle-variations across the object-free X-ray beam, the individual pixels in the reflectivity profile images of the object can then be remapped to the corresponding theta-angle position.
In accordance with embodiments, the subject matter described herein can include a method for acquiring high speed and/or high angular resolution DEI reflectivity profiles. In DEI, the diffraction properties of perfect silicon crystals can be exploited to convert small deviations in the angle of the X-ray beam (on the order of tenths of microradians) caused by refraction from structures along the X-ray beam path into intensity differences in an image. A DEI system has at minimum 1 monochromator crystal, which monochromates and collimates the X-ray beam, and at minimum 1 analyzer crystal. The X-ray beam at the sample/patient location is a slot X-ray beam. Typically, prior to obtaining a DEI image, the diffraction planes of the monochromator and analyzer crystals are made parallel within about 0.1 microradians. This alignment may require that both the analyzer crystal's theta- and chi-angles to be aligned (angles defined in
In accordance with the present disclosure, the DEI system can be configured such that a DEI optical system or an array of DEI optical systems will intercept the divergent X-ray beam from the X-ray source. The beam emerging from each individual optics systems within the array can then be incident upon either a high-spatial resolution detector or an energy-resolving, low-spatial resolution (˜1 mm̂2 pixels) detector. The DEI optical systems for both the high-spatial resolution and low-spatial resolution portions of the X-ray beam can be operated independently of one another; the angular position of the analyzer crystal for the high-spatial resolution portion of the beam is independent of the analyzer crystal position for the low-spatial resolution portion of the beam. For the beam that is incident upon the high-spatial resolution detector, the small pixel size of the detector can allow for detailed imaging of anatomical information or of structural information for structures of about 50 microns or larger. For the portion of the X-ray beam that is incident on the low-spatial resolution detector, the large pixel area and high-efficiency of the photon counting detector can allow for the high-speed measurement of the reflectivity profile, which can give detailed information about microstructural features (features smaller than about 100 microns) in the imaging field. The data from the two types of images can then be superimposed to combine structural/anatomical and microstructural information about the imaging object.
The reflectivity profile may have clinical utility because the width of the reflectivity profile is proportional to the number of refracting microstructures along the X-ray beam path. Simultaneous acquisition of high-spatial resolution structural/anatomical information and microstructural information can greatly improve clinicians' ability to diagnose and localize injuries or disease, especially those in the lung or bone. Beyond clinical utility of this approach, this could be used for industrial inspection. Any scenario in which it's advantageous to simultaneously reveal structural and microstructure information could benefit greatly.
According to another aspect, the subject matter described herein can include a system comprising an X-ray generation device configured to generate a plurality of first X-ray beams. The system can include monochromator crystals including first and second sides. The first sides of the monochromator crystals are positioned in predetermined positions to directly intercept the plurality of first X-ray beams for generating a plurality of second X-ray beams. The second sides of the monochromator crystals are positioned to intercept the plurality of second X-ray beams such that a plurality of third X-ray beams is produced for transmission through an object. A plurality of analyzer crystals are positioned to intercept transmitted X-ray beams at angles of incidence of the analyzer crystals. An image detector can be configured to detect an image of the object from beams diffracted from the analyzer crystals. An image of the object may be detected based upon beams diffracted from the analyzer crystals. These systems and methods can be advantageous, for example, because they can provide extremely low dose in medical applications, fast scan times, high resolution, and relatively low operation and build costs. Further, for example, these systems can be constructed into a compact unit and be readily usable in clinical and industrial applications. Additional description about these systems and related methods are described in further detail herein.
An image processing technique using DEI in accordance with the subject matter described herein can use images acquired at symmetric points of the rocking curve to generate apparent absorption and refraction images of an object. A DEI apparent absorption image is similar to a conventional radiograph image, but exhibits much greater contrast owing to scatter rejection. DEI refraction images can depict the magnitude of small beam deflections caused by large-scale refractive-index features (features of a size at or greater than the system resolution). A DEI extinction image is generated at points on the rocking curve where the primary mechanism of contrast is due to photons that have been scattered by an object on the order of microradians. Another DEI based imaging processing technique may be referred to as Multiple Image Radiography (MIR) which uses multiple points on the rocking curve to generate quantitative images representing an object's X-ray absorption, refraction, and ultra-small angle scatter. Systems and methods can generate images at any point on the analyzer rocking curve, and can thus be used to generate: (1) single image DEI at any analyzer position; (2) DEI apparent absorption and refraction images; and (3) mass density images. The ability to generate the raw image data required for these processes and any other DEI based processing technique are useful for all DEI based processing techniques. In addition, systems and methods described herein are amenable for use in computed tomography, and can provide the raw data for use in any DEI-based computed tomography algorithm.
As understood, a small area source may refer to any source capable of generating X-ray beams from a small area in space. For example, an X-ray tube may include multiple small area sources for emitting X-ray beams from multiple points. The small area sources may be within the same X-ray tube source. Alternatively or in addition to being a part of a system as disclosed herein, multiple X-ray tube sources may each provide one or more small area sources and be used together for generating multiple X-ray beams.
Approaches to DEI or analyzer-based imaging as described herein can use large X-ray beams at a sample or object location to image the object without the need to scan the X-ray beam. These large area X-ray beams can be generated through the use of asymmetric crystals, an X-ray line source, or a combination of the two. As with the techniques and systems presented herein, the other techniques may require a high-power X-ray tube source operating at a peak voltage well above the Kα1 emission energy of their respective source in order to generate sufficient Kα1 flux for a small imaging time. The high energy X-rays generated by the high peak voltage will be readily scattered by the monochromator crystals, and this scattered radiation dose delivered to the object to be imaged. Stated in another way, there will be a “line-of-sight” between the scatter locations on the monochromator crystals and the object to be imaged over which there cannot be significant radiation shielding to stop the scattered radiation from reaching the object to be imaged. This contribution of scattered radiation to the radiation dose delivered to the object to be imaged can be overcome through the use of a multiple small-vertical height X-ray beam system, which can be created through the use of an array of small area X-ray beams. Any radiation that does not propagate along the narrow beam path can be filtered out by high-Z shielding, and therefore only a minimal amount of scattered radiation will reach the object to be imaged.
The systems and methods in accordance with the subject matter described herein can be applied to a variety of medical applications. As set forth above, the systems and methods described herein can be applied for breast imaging. Further, for example, the systems and methods described herein can be applied to cartilage imaging, neuroimaging, cardiac imaging, vascular imaging (with and without contrast), pulmonary (lung) imaging, bone imaging, genitourinary imaging, gastrointestinal imaging, soft tissue imaging in general, hematopoietic system imaging, and endocrine system imaging. In addition to image time and dose, a major advancement of using higher energy X-rays may be the thickness of the object that can be imaged. For applications such as breast imaging, the system described allows for imaging full thickness breast tissue with a clinically realistic imaging time. The same can be said for other regions of the body, such as the head, neck, extremities, abdomen, and pelvis. Without the limitations of X-ray absorption, utilization of DEI with higher energy X-rays dramatically increases the penetration ability of X-rays. For soft tissue, only a small portion of the X-ray photons incident on the object may be absorbed, which greatly increases efficiency of emitted photons from the X-ray tube reaching the detector.
With respect to pulmonary imaging, DEI techniques as described herein can produce excellent contrast in the lungs and can be used heavily for diagnosing pulmonary conditions such as pneumonia. Fluid collections in the lungs generate a marked density gradient that could be detected easily with DEI. The density gradient, characteristics of the surrounding tissue, and geometric differences between normal lung tissue and tissue with a tumor can be large, producing good contrast. Further, DEI techniques described herein can be applied to lung cancer screening and diagnosis. The high angular resolutions of the reflectivity profile may reveal microstructural information about the lungs including the degree to which the alveoli are aerated.
With respect to bone imaging, DEI techniques as described herein can produce an excellent image of bone in general. For the high spatial resolution structural imaging, the high refraction and extinction contrast of DEI can be especially useful for visualizing fractures and lesions within the bone. The high angular resolution images from the reflectivity profile reveals properties of the bone microstructure that can be indicative of microarchitectural deterioration of the bone.
Further, the systems and methods in accordance with the subject matter described herein can be applied to a variety of inspection and industrial applications. For example, the systems and methods can be applied for meat inspection, such as poultry inspection. For example, the systems and methods can be used for viewing sharp bones, feathers, and other low contrast objects in meats that required screening and/or removal. The systems and methods described herein can be applied for such screening.
The systems and methods described herein can also be applied for manufacture inspection. For example, the systems and methods can be used for inspecting welds, such as in aircraft production. DEI techniques as described herein can be used to inspect key structural parts that undergo heavy wear and tear, such as jet turbine blades. Further, for example, the systems and methods described herein can be used for inspecting circuit boards and other electronics. In another example, the systems and methods described herein can be used for tire inspection, such as the inspection of steel belts and tread integrity.
Further, the systems and methods in accordance with the subject matter described herein can be used for security screening purposes. For example, the systems and methods can be used for screening at airports and seaports. DEI techniques as described herein can be used for screening for plastic and low absorption contrast objects, such as plastic knives, composite guns difficult to detect with conventional X-ray, and plastic explosives. For imaging larger objects, such as for airport baggage inspection, the distance between the X-ray tube and detector can be increased to allow beam divergence. A larger analyzer crystal may be necessary to accommodate a larger fan beam.
The device described provides a mechanism that can be translated into a computed tomography imaging system, or DEI-CT. A DEI-CT system, resembling a third generation conventional computed tomography system, may use the same apparatus but modified for rotation around a central point. Alternatively, the system could remain stationary and the object, sample, or patient could be rotated in the beam. A DEI-CT system of this design would produce images representing X-ray absorption, refraction, and ultra-small angle scatter rejection (extinction), but they would be resolved in three dimensions.
The various techniques described herein may be implemented with hardware or software or, where appropriate, with a combination of both. Thus, the methods and apparatus of the disclosed embodiments, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other machine-readable storage medium, wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the subject matter disclosed herein. In the case of program code execution on programmable computers, the computer will generally include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device and at least one output device. One or more programs are preferably implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the program(s) can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and combined with hardware implementations.
The described methods and apparatus may also be embodied in the form of program code that is transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via any other form of transmission, wherein, when the program code is received and loaded into and executed by a machine, such as an EPROM, a gate array, a programmable logic device (PLD), a client computer, a video recorder or the like, the machine becomes an apparatus for practicing the subject matter disclosed herein. When implemented on a general-purpose processor, the program code combines with the processor to provide a unique apparatus that operates to perform the processing of the presently disclosed subject matter.
While the embodiments have been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function without deviating therefrom. Therefore, the disclosed embodiments should not be limited to any single embodiment, but rather should be construed in breadth and scope in accordance with the appended claims.
This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/939,087, filed Feb. 12, 2014 and titled SYSTEMS AND METHODS FOR QUANTIFYING MULTIPLE REFRACTIONS WITH DIFFRACTION ENHANCED IMAGING; the content of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61939087 | Feb 2014 | US |
