U.S. patent application number 14/749592 was filed with the patent office on 2015-12-24 for methods and apparatus for determining information regarding chemical composition using x-ray radiation.
The applicant listed for this patent is Eric H. Silver. Invention is credited to Eric H. Silver.
Application Number | 20150369758 14/749592 |
Document ID | / |
Family ID | 54869392 |
Filed Date | 2015-12-24 |
United States Patent
Application |
20150369758 |
Kind Code |
A1 |
Silver; Eric H. |
December 24, 2015 |
METHODS AND APPARATUS FOR DETERMINING INFORMATION REGARDING
CHEMICAL COMPOSITION USING X-RAY RADIATION
Abstract
According to some aspects, a method is provided comprising
generating first monochromatic x-ray radiation at a first energy,
directing at least some of the first monochromatic x-ray radiation
to irradiate subject matter of interest, detecting at least some of
the first monochromatic x-ray radiation transmitted through the
subject matter of interest, and determining information about a
chemical composition of the subject matter of interest based, at
least in part, on the detected first monochromatic x-ray radiation
and the first energy.
Inventors: |
Silver; Eric H.; (Needham,
MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Silver; Eric H. |
Needham |
MA |
US |
|
|
Family ID: |
54869392 |
Appl. No.: |
14/749592 |
Filed: |
June 24, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62016203 |
Jun 24, 2014 |
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Current U.S.
Class: |
378/53 |
Current CPC
Class: |
G01N 23/083 20130101;
G01N 2223/423 20130101; G01N 2223/405 20130101 |
International
Class: |
G01N 23/083 20060101
G01N023/083 |
Claims
1. A method comprising: generating first monochromatic x-ray
radiation at a first energy; directing at least some of the first
monochromatic x-ray radiation to irradiate subject matter of
interest; detecting at least some of the first monochromatic x-ray
radiation transmitted through the subject matter of interest; and
determining information about a chemical composition of the subject
matter of interest based, at least in part, on the detected first
monochromatic x-ray radiation and the first energy.
2. The method of claim 1, wherein determining information about the
chemical composition of the subject matter of interest includes
computing a first mass absorption coefficient value of the subject
matter of interest based, at least in part, on the detected first
monochromatic x-ray radiation.
3. The method of claim 2, wherein determining information about the
chemical composition of the subject matter of interest includes
using the computed first mass absorption coefficient value of the
subject matter of interest and the first energy to determine that
material is present in the subject matter of interest.
4. The method of claim 3, wherein determining information about the
chemical composition of the subject matter of interest includes
identifying one of a plurality of characteristic curves based, at
least in part, on the computed first mass absorption coefficient
value of the subject matter of interest and the first energy.
5. The method of claim 4, wherein each of the plurality of
characteristic curves represents mass absorption coefficient values
as a function of energy for a respective material, and wherein
identifying one of the plurality of characteristic curves includes
identifying which of the plurality of characteristic curves best
matches the computed first mass absorption coefficient value at the
first energy.
6. The method of claim 1, further comprising: generating second
monochromatic x-ray radiation at a second energy; directing at
least some of the second monochromatic x-ray radiation to irradiate
the subject matter of interest; detecting at least some of the
second monochromatic x-ray radiation transmitted through the
subject matter of interest; and determining information about the
chemical composition of the subject matter of interest based, at
least in part, on the detected second monochromatic x-ray radiation
and the second energy.
7. The method of claim 6, wherein determining information about the
chemical composition of the subject matter of interest comprises:
computing a first mass absorption coefficient value of the subject
matter of interest based, at least in part, on the detected first
monochromatic x-ray radiation; and computing a second mass
absorption coefficient value of the subject matter of interest
based, at least in part, on the detected second monochromatic x-ray
radiation;
8. The method of claim 7, wherein determining information about the
chemical composition of the subject matter of interest includes
using the computed first mass absorption coefficient value and the
first energy, and the computed second mass absorption coefficient
value and the second energy to determine that material is present
in the subject matter of interest.
9. The method of claim 8, wherein determining information about the
chemical composition of the subject matter of interest includes
identifying one of a plurality of characteristic curves based, at
least in part, on the computed first mass absorption coefficient
value and the first energy, and the computed second mass absorption
coefficient value and the second energy.
10. The method of claim 9, wherein each of the plurality of
characteristic curves represents mass absorption coefficient values
as a function of energy for a respective material, and wherein
identifying one of the plurality of characteristic curves includes
identifying which of the plurality of characteristic curves best
matches the computed first mass absorption coefficient value at the
first energy and the computed second mass absorption coefficient
value at the second energy.
11. The method of claim 1, wherein generating the first
monochromatic x-ray radiation comprises: generating broad spectrum
x-ray radiation from an x-ray tube comprising a first target that,
in response to being irradiated by electrons, emits the broad
spectrum x-ray radiation; and directing at least some of the broad
spectrum x-ray radiation to irradiate a second target comprising
material that, in response to the irradiation, emits the first
monochromatic x-ray radiation.
12. The method of claim 6, wherein generating the first
monochromatic x-ray radiation and the second monochromatic x-ray
radiation comprises: generating broad spectrum x-ray radiation from
an x-ray tube comprising a first target that, in response to being
irradiated by electrons, emits the broad spectrum x-ray radiation;
directing at least some of the broad spectrum x-ray radiation to
irradiate a second target comprising material that, in response to
the irradiation, emits the first monochromatic x-ray radiation; and
directing at least some of the broad spectrum x-ray radiation to
irradiate a third target comprising material that, in response to
the irradiation, emits the second monochromatic x-ray
radiation.
13. A system comprising: a monochromatic x-ray radiation source
configured to generate first monochromatic x-ray radiation at a
first energy and to direct at least some of the first monochromatic
x-ray radiation to irradiate subject matter of interest; a detector
array arranged to detect at least some of the first monochromatic
x-ray radiation transmitted through the subject matter of interest;
and at least one processor programmed to determine information
about a chemical composition of the subject matter of interest
based, at least in part, on the detected first monochromatic x-ray
radiation and the first energy.
14. The system of claim 13, wherein the at least one processor is
programmed to compute a first mass absorption coefficient value of
the subject matter of interest based, at least in part, on the
detected first monochromatic x-ray radiation.
15. The system of claim 14, wherein the at least one processor is
programmed to use the computed first mass absorption coefficient
value of the subject matter of interest and the first energy to
determine that material is present in the subject matter of
interest.
16. The system of claim 15, wherein the at least one processor is
programmed to identify one of a plurality of characteristic curves
based, at least in part, on the computed first mass absorption
coefficient value of the subject matter of interest and the first
energy.
17. The system of claim 16, wherein each of the plurality of
characteristic curves represents mass absorption coefficient values
as a function of energy for a respective material, and wherein at
least one processor is programmed to identify which of the
plurality of characteristic curves best matches the computed first
mass absorption coefficient value at the first energy.
18. The system of claim 13, wherein the monochromatic x-ray source
is configured to generate second monochromatic x-ray radiation at a
second energy and direct at least some of the second monochromatic
x-ray radiation to irradiate the subject matter of interest,
wherein the detector array is configured to detect at least some of
the second monochromatic x-ray radiation transmitted through the
subject matter of interest, and wherein the at least one processor
is configured to determine information about the chemical
composition of the subject matter of interest based, at least in
part, on the detected second monochromatic x-ray radiation and the
second energy.
19. The system of claim 18, wherein at least one processor is
programmed to: compute a first mass absorption coefficient value of
the subject matter of interest based, at least in part, on the
detected first monochromatic x-ray radiation; and compute a second
mass absorption coefficient value of the subject matter of interest
based, at least in part, on the detected second monochromatic x-ray
radiation.
20. The system of claim 19, wherein the at least one processor is
programmed to use the computed first mass absorption coefficient
value and the first energy, and the computed second mass absorption
coefficient value and the second energy to determine that material
is present in the subject matter of interest.
21. The system of claim 20, wherein the at least one processor is
programmed to identify one of a plurality of characteristic curves
based, at least in part, on the computed first mass absorption
coefficient value and the first energy, and the computed second
mass absorption coefficient value and the second energy.
22. The system of claim 21, wherein each of the plurality of
characteristic curves represents mass absorption coefficient values
as a function of energy for a respective material, and wherein the
at least one processor is programmed to identify which of the
plurality of characteristic curves best matches the computed first
mass absorption coefficient value at the first energy and the
computed second mass absorption coefficient value at the second
energy.
23. The system of claim 13, wherein monochromatic x-ray radiation
source is configured to: generate broad spectrum x-ray radiation
from an x-ray tube comprising a first target that, in response to
being irradiated by electrons, emits the broad spectrum x-ray
radiation; and direct at least some of the broad spectrum x-ray
radiation to irradiate a second target comprising material that, in
response to the irradiation, emits the first monochromatic x-ray
radiation.
24. The system of claim 18, wherein monochromatic x-ray radiation
source is configured to: generate broad spectrum x-ray radiation
from an x-ray tube comprising a first target that, in response to
being irradiated by electrons, emits the broad spectrum x-ray
radiation; direct at least some of the broad spectrum x-ray
radiation to irradiate a second target comprising material that, in
response to the irradiation, emits the first monochromatic x-ray
radiation; and direct at least some of the broad spectrum x-ray
radiation to irradiate a third target comprising material that, in
response to the irradiation, emits the second monochromatic x-ray
radiation.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(e) of Provisional Application No.: 62/016,203, entitled
"Determining Effective Chemical Composition Using Monochromatic
X-ray Imaging," filed Jun. 24, 2014, which is herein incorporated
by reference in its entirety.
BACKGROUND
[0002] Conventional x-ray systems provide a technique for
non-invasively visualizing internal structure of an object of
interest by exposing the object to relatively high-energy
electromagnetic radiation, commonly referred to as x-rays. X-rays
emitted from a radiation source interact with the object and are
absorbed, scattered and/or diffracted at varying levels by the
internal structures of the object. For example, x-ray radiation is
attenuated according to the various absorption characteristics of
the materials that the x-rays encounter. By measuring the
attenuation of the x-ray radiation that is transmitted through or
otherwise exits the object, information related to the opacity
distribution of the internal structure of the object may be
obtained.
[0003] To perform this type of x-ray process, an x-ray source and
an array of detectors (i.e., one or more detectors) responsive to
x-ray radiation may be arranged about the object. X-rays impinging
on a surface of the detectors cause the respective detector in the
array to, for example, generate an electrical signal proportional
to the intensity of the impinging x-ray radiation. This detector
output can in turn be used to compute information regarding the
opacity distribution of the internal structure of the object, for
example, by reconstructing one or more images from the output of
the detector array.
SUMMARY
[0004] Some embodiments include a method comprising generating
first monochromatic x-ray radiation at a first energy, directing at
least some of the first monochromatic x-ray radiation to irradiate
subject matter of interest, detecting at least some of the first
monochromatic x-ray radiation transmitted through the subject
matter of interest, and determining information about a chemical
composition of the subject matter of interest based, at least in
part, on the detected first monochromatic x-ray radiation and the
first energy.
[0005] Some embodiments include a system comprising a monochromatic
x-ray radiation source configured to generate first monochromatic
x-ray radiation at a first energy and to direct at least some of
the first monochromatic x-ray radiation to irradiate subject matter
of interest, a detector array arranged to detect at least some of
the first monochromatic x-ray radiation transmitted through the
subject matter of interest, and at least one processor programmed
to determine information about a chemical composition of the
subject matter of interest based, at least in part, on the detected
first monochromatic x-ray radiation and the first energy.
BRIEF DESCRIPTION OF DRAWINGS
[0006] Various aspects and embodiments of the application will be
described with reference to the following figures. The figures are
not necessarily drawn to scale.
[0007] FIG. 1 is a schematic of a conventional x-ray tube;
[0008] FIG. 2. illustrates the scenario in which an electron (much
lighter than the nucleus) comes very close to the nucleus and the
electromagnetic interaction causes a deviation of the trajectory
where the electron loses energy and an x-ray photon is emitted and
describes Bremsstralung in its simplest form;
[0009] FIG. 3 illustrates the Bremsstrahlung spectrum produced by a
typical x-ray tube, wherein the lower energy x-rays trying to
escape the target are absorbed causing the characteristic roll over
of the spectrum at low energies;
[0010] FIG. 4 illustrates the physical phenomenon that generates
characteristic line emissions;
[0011] FIG. 5 illustrates the combined spectrum from an x-ray tube
with a molybdenum anode showing the thick target Bremsstrahlung and
the characteristic molybdenum line emission;
[0012] FIG. 6A illustrates the photoelectric effect;
[0013] FIG. 6B illustrates the principle of x-ray fluorescence from
the K-shell;
[0014] FIG. 7 illustrates an x-ray fluorescence spectrum made by
irradiating a target of aluminum (Al) with copper x-rays which were
generated by an x-ray tube with an anode of copper;
[0015] FIG. 8 illustrates the absorption coefficient as a function
of x-ray energy for zirconium, wherein the discontinuous jumps or
edges show how the absorption is enhanced just above the binding
energies of the electrons in zirconium;
[0016] FIG. 9 illustrates a monochromatic x-ray system, in
accordance with some embodiments of the present invention;
[0017] FIG. 10 is a flowchart illustrating a method of determining
information about the chemical composition of subject matter
internal to an object of interest, in accordance with some
embodiments of the present invention;
[0018] FIG. 11 is a diagram of characteristic curves showing the
mass absorption coefficient as a function of x-ray energy for a
number of exemplary substances, in accordance with some
embodiments;
[0019] FIG. 12 illustrates a schematic illustrating relationships
used to compute one or more mass absorption coefficients in
accordance with some embodiments;
[0020] FIG. 13 illustrates the difference between mass absorption
coefficients at different x-ray energies as a function of atomic
weight;
[0021] FIGS. 14A and 14B illustrate the thick target Bremsstrahlung
spectrum generated by the conventional x-ray tube with a rhodium
anode and the Zr K.alpha. and K.beta. x-rays produced by x-ray
fluorescence using the broad band spectrum in FIG. 13A,
respectively; and
[0022] FIG. 15 is a diagram of a computer system on which
techniques described herein may be implemented.
DETAILED DESCRIPTION
[0023] As discussed above, conventional x-ray systems can provide
information regarding the structural characteristics of regions
within an object of interest. However, conventional x-ray systems
used to perform, for example, diagnostic imaging do not have the
capability to ascertain information about the chemical composition
of the subject matter through which x-rays are transmitted. This
inability is due in part to the fact that conventional x-ray
systems perform imaging by detecting broad spectrum x-ray radiation
transmitted through an object of interest (i.e., x-ray radiation
containing x-rays having energies across a broad spectrum). For
reasons that are discussed in further detail below, to determine
information about the chemical composition of subject matter
through which x-rays are passed, the energy of transmitted x-rays
typically must be ascertainable. Because the broad spectrum x-ray
radiation utilized by conventional x-ray imaging systems contain
x-rays having energies across a substantially continuous spectrum,
the energy of impinging x-rays would need to be measured to compute
information regarding chemical composition. However, imaging
detector arrays at the scale required cannot measure the energy of
impinging x-rays at the spectral resolution needed to ascertain
information regarding the chemical composition of subject matter of
an object being imaged. Thus, conventional x-ray imaging systems
cannot provide chemical composition information of subject matter
of interest.
[0024] While detectors utilized in spectroscopic devices capable of
analyzing small samples of material may have suitable spectral
resolution, such detectors are not suitable for constructing
relatively large scale arrays of the size needed to image
relatively large objects in-vivo such as the breast, brain, torso
or other portions of the anatomy in medical imaging, or large
structures in various other non-destructive imaging applications.
Thus, to utilize a detector employed in spectroscopic applications,
a single such detector would need to be scanned over the object of
interest, either by rotating and translating the source/detector,
by rotating and translating the object, or if the field of view is
large enough, translating the detector. Such a scanning procedure
is too time consuming to be of practical use, may result in too
high an x-ray dose (e.g., if a pencil beam is not utilized).
[0025] The inventor has appreciated that using monochromatic
radiation allows for the determination of chemical composition of
regions of an object of interest in an in vivo and/or
non-destructive x-ray acquisition process. Specifically, because
the energy of monochromatic x-rays are known and therefore need not
be measured, conventional x-ray detectors can be used (e.g.,
conventional large area detector arrays). In particular, when
monochromatic x-rays are used, detectors capable of detecting the
intensity of x-rays impinging on the detector surface are
sufficient. In this respect, an x-ray acquisition process that is
conventional in some respects (e.g., that uses conventional
detectors), but that uses monochromatic x-ray radiation instead of
broad spectrum radiation, may be used to obtain x-ray information
from which information about chemical composition (as well as the
density distribution) of subject matter internal to an object of
interest may be obtained. In addition, because monochromatic
radiation is used, the x-ray dose to a patient in a medical x-ray
procedure is substantially reduced, as discussed in further detail
below.
[0026] According to some embodiments, monochromatic x-ray radiation
is directed to irradiate an object of interest. At least some
monochromatic x-rays radiation passing through the object is
detected and the detected monochromatic x-rays are used to
determine information about the chemical composition of material
through which the x-rays passed. For example, a measure of one or
more mass absorption coefficients may be computed based on the
detected monochromatic x-rays. The one or more mass absorption
coefficients may be used to identify material present through which
the monochromatic x-rays passed. According to some embodiments, the
material is identified, at least in part, by matching the one or
more mass absorption coefficients to a characteristic curve
associated with the material, as discussed in further detail
below.
[0027] To perform techniques described herein, a source of
monochromatic radiation is needed. Conventional techniques for
producing monochromatic radiation, for example, using Bragg
crystals or a synchrotron, may not be practicable in many
circumstances. For example, Bragg crystals are relatively
inefficient and may not generate monochromatic x-ray radiation at
sufficient intensity in some circumstances. Synchrotron systems are
multi-million dollar facilities that are not widely available as a
result of the high-cost and the need to have a large, specialized
installment. The inventor has developed a relatively low-cost,
table-top method and apparatus for producing tunable monochromatic
x-ray radiation capable of efficiently producing monochromatic
x-ray radiation at desired energies. Examples of such monochromatic
x-ray devices and methods are described in U.S. application Ser.
No. 12/761,724, entitled "Monochromatic X-ray Methods and
Apparatus," filed Apr. 16, 2010 and issued on Dec. 11, 2012 as U.S.
Pat. No. 8,331,534 ('534 patent), which is herein incorporated by
reference in its entirety. Aspects of exemplary monochromatic x-ray
devices suitable for performing techniques described herein are
described in further detail below.
[0028] To produce monochromatic x-ray radiation, a conventional
x-ray tube that generates x-rays over a broad energy range may be
used to irradiate a solid target, which in turn, will emit
monochromatic fluorescent x-rays. The fluorescing target may be
made from a single element or it may be a composite of several
elements. The energies of these fluorescent x-rays are
characteristic of the elemental composition of the target material,
which can be chosen as desired. In this manner, a monochromatic
x-ray device may be provided by, at least in part, combining in
series a target that produces broad spectrum radiation in response
to an incident electron beam, followed by a fluorescing target that
produces monochromatic x-ray in response to incident broad spectrum
radiation. The term "broad spectrum radiation" is used herein to
describe Bremsstralung radiation with or without characteristic
emission lines of the anode material. The principle of operation of
such a device is described in further detail below.
[0029] Thick Target Bremsstrahlung
[0030] In an x-ray tube electrons are liberated from a heated
filament called the cathode and accelerated by a high voltage
(e.g., .about.50 kV) toward a metal target called the anode as
illustrated schematically in FIG. 1. The high energy electrons
interact with the atoms in the anode. Often an electron with energy
E.sub.1 comes close to a nucleus in the target and its trajectory
is altered by the electromagnetic interaction. In this deflection
process, it decelerates toward the nucleus. As it slows to an
energy E.sub.2, it emits an x-ray photon with energy
E.sub.2-E.sub.1. This radiation is called Bremsstrahlung radiation
(braking radiation) and the kinematics are shown in FIG. 2
[0031] The energy of the emitted photon can take any value up to
the maximum energy of the incident electron, E.sub.max. As the
electron is not destroyed it can undergo multiple interactions
until it loses all of its energy or combines with an atom in the
anode. Initial interactions will vary from minor to major energy
changes depending on the actual angle and proximity to the nucleus.
As a result, Bremsstrahlung radiation will have a generally
continuous spectrum, as shown in FIG. 3. The probability of
Bremsstrahlung production is proportional to Z.sup.2, where Z is
the atomic number of the target material, and the efficiency of
production is proportional to Z and the x-ray tube voltage. Note
that low energy Bremsstrahlung x-rays are absorbed by the thick
target anode as they try to escape from deep inside causing the
intensity curve to bend over at the lowest energies, as discussed
in further detail below.
[0032] Characteristic Line Emission
[0033] While most of the electrons slow down and have their
trajectories changed, some will collide with electrons that are
bound by an energy, BE, in their respective orbitals or shells that
surround the nucleus in the target atom. As shown in FIG. 4, these
shells are denoted by K, L, M, N, etc. In the collision between the
incoming electron and the bound electron, the bound electron will
be ejected from the atom if the energy of the incoming electron is
greater than BE of the orbiting electron. For example, the
impacting electron with energy E>BE.sub.K, shown in FIG. 4, will
eject the K-shell electron leaving a vacancy in the K-shell. The
resulting excited and ionized atom will de excite as an electron in
an outer orbit will fill the vacancy. During the de-excitation, an
x-ray is emitted with an energy equal to the difference between the
initial and final energy levels of the electron involved with the
de excitation. Since the energy levels of the orbital shells are
unique to each element on the Periodic Chart, the energy of the
x-ray identifies the element. The energy will be monoenergetic and
the spectrum appears monochromatic rather than a broad continuous
band. Here, monochromatic means that the width in energy of the
emission line is equal to the natural line width associated with
the atomic transition involved. For copper K.alpha. x-rays, the
natural line width is about 4 eV. For Zr K.alpha., Mo K.alpha. and
Pt K.alpha., the line widths are approximately, 5.7 eV, 6.8 eV and
60 eV, respectively. The complete spectrum from an x-ray tube with
a molybdenum target as the anode is shown in FIG. 5. The
characteristic emission lines unique to the atomic energy levels of
molybdenum are shown superimposed on the thick target
Bremsstrahlung.
[0034] X-Ray Absorption and X-Ray Fluorescence
[0035] When an x-ray from an x-ray tube strikes a sample, the x-ray
can either be absorbed by an atom or scattered through the
material. The process in which an x-ray is absorbed by an atom by
transferring all of its energy to an innermost electron is called
the photoelectric effect, as illustrated in FIG. 6A. This occurs
when the incident x-ray has more energy than the binding energy of
the orbital electron it encounters in a collision. In the
interaction the photon ceases to exist imparting all of its energy
to the orbital electron. Most of the x-ray energy is required to
overcome the binding energy of the orbital electron and the
remainder is imparted to the electron upon its ejection leaving a
vacancy in the shell. The ejected free electron is called a
photoelectron. A photoelectric interaction is most likely to occur
when the energy of the incident photon exceeds but is relatively
close to the binding energy of the electron it strikes. As an
example, a photoelectric interaction is more likely to occur for a
K-shell electron with a binding energy of 23.2 keV when the
incident photon is 25 keV than if it were 50 keV. This is because
the photoelectric effect is inversely proportional to approximately
the third power of the x-ray energy.
[0036] The vacancies in the inner shell of the atom present an
unstable condition for the atom. As the atom returns to its stable
condition, electrons from the outer shells are transferred to the
inner shells and in the process emit a characteristic x-ray whose
energy is the difference between the two binding energies of the
corresponding shells as described above in the section of
Characteristic Line Emission. This photon-induced process of x-ray
emission is called x-ray Fluorescence, or XRF. FIG. 6B shows
schematically x-ray fluorescence from the K-shell and a typical
x-ray fluorescence spectrum from a sample of aluminum is shown in
FIG. 7. The characteristic x-rays are labeled with a K to denote
the shell where the original vacancy originated. In addition, alpha
(.alpha.) and beta (.beta.) are used to identify the x-rays that
originated from the transitions of electrons from higher shells.
Hence, a K.alpha. x-ray is produced from a transition of an
electron from the L to the K-shell, and a K.beta. x-ray is produced
from a transition of an electron from the M to a K-shell, etc. It
is important to note that these monoenergetic emission lines do not
sit on top of a background of broad band continuous radiation;
rather, the spectrum is Bremsstrahlung free. As discussed above,
the x-ray tube produces thick target Bremsstrahlung and
characteristic x-rays from the copper in the anode target. But when
the combined spectral emission from the x-ray tube is used to
irradiate the aluminum sample, only the monoenergetic emission
lines, Al K.alpha. and Al K.beta. are produced via x-ray
fluorescence.
[0037] As mentioned above, the probability for x-ray absorption for
a given absorbing element decreases with increasing energy of the
incident photon. However, this fall off is interrupted by a sharp
rise when the x-ray energy is equal to the binding energy of an
electron shell (K, L, M, etc.) in the absorber. This is the lowest
energy at which a vacancy can be created in the particular shell
and is referred to as the edge. FIG. 8 shows the absorption of
Zirconium as a function of x-ray energy. The absorption is defined
on the ordinate axis by its mass attenuation coefficient. The
absorption edges corresponding to the binding energies of the
L-orbitals and the K-orbitals are shown by the discontinuous jumps
at approximately 2.3 keV and 18 keV, respectively. Every element on
the Periodic Chart has a similar curve describing its absorption as
a function of x-ray energy.
[0038] As discussed above, a conventional x-ray tube generates a
thick target broad band Bremsstrahlung spectrum as shown in FIG.
14A. The x-ray tube has a rhodium anode and the two peaks in the
spectrum are rhodium K.alpha. and K.beta. line emission resulting
from the electron excitation in the x ray tube. The spectrum in
FIG. 14B shows the monochromatic Zr K.alpha. and K.beta. x-rays
that are produced via fluorescence when the x-rays in the broad
spectrum radiation irradiate the Zr target. It should be
appreciated that the lines denoted by scattered x-rays are an
artifact of the detectors and not an indication that the radiation
from the fluorescent target is polychromatic, which is
monochromatic.
[0039] FIG. 9 illustrates a schematic of an x-ray apparatus for
generating monochromatic x-rays, in accordance with some
embodiments. An x-ray tube 1 generates thick target Bremsstrahlung
radiation by ohmically heating a filament (b) (which operates as
the cathode) with a voltage (c) (typically 5-6 volts) so that the
filament emits electrons (d). The electrons are accelerated toward
the anode (e) due to the high voltage bias (f) of the anode with
respect to the filament (which is typically at zero or ground
potential). As the electrons are decelerated by the anode, they
generate Bremsstrahlung radiation as shown in FIG. 3 and a
significant amount of ohmic power is dissipated by the anode in the
form of heat. This heat may be conducted from the anode material to
the outside of the vacuum enclosure. Characteristic emission lines
unique to the anode material may also be produced by the electron
bombardment of the anode material provided the voltage is large
enough. The x-ray radiation exits the vacuum enclosure through a
window (g) that is vacuum tight so that the x-rays may be
transmitted with high efficiency (e.g. beryllium).
[0040] It should be appreciated that x-ray tube 1 may be a standard
x-ray tube for generating broad spectrum radiation. For example,
the x-ray tube may be similar to or the same as conventional x-ray
tubes currently being used in medical applications. Accordingly,
some embodiments of the x-ray apparatus described herein are
capable of being manufactured as a relatively low-cost, table-top
solution. As a result, such x-ray apparatus may be suitable for
widespread adoption by medical facilities such as hospitals to
perform monochromatic x-ray diagnostic and/or therapeutic
applications, as described in further detail below.
[0041] The x-ray beam 2 emitted from the x-ray tube irradiates a
fluorescent target 3 which produces monochromatic x-radiation
characteristic of the element (s) in the target in response to the
x-rays incident on the target. The monochromatic x-rays 4 diverge
through an aperture (e.g., a pinhole or slit 5) and pass through
the sample 6 (e.g., target tissue to be imaged or treated, as
discussed in further detail below). For example, since the size of
the spot on the fluorescent target is usually a few millimeters in
diameter, an aperture such as a slit, pinhole or other aperture may
be used to establish a source of monochromatic x-rays originating
from a smaller diameter spot to improve spatial resolution in the
image. The point source of the monochromatic x-rays diverges in the
shape of a cone. These x-rays pass through the sample tissue and
are detected by a detector array, for example, a 2D imaging x-ray
detector. However, if the focal region on the fluorescent target
(spot size) is compact enough, the aperture may be unnecessary.
Other components may be used to collimate the x-rays to form a
pencil beam, a fan beam or any other shaped beam, as the aspects of
the invention are not limited in this respect. The x-ray tube,
fluorescent target and, when present, any further mechanism to
focus or shape the monochromatic x-rays, are collectively referred
to herein as the monochromatic x-ray source. The transmitted
monochromatic x-rays are detected by an x-ray detector 7 to produce
an image of the sample.
[0042] For example, the monochromatic x-rays may penetrate the
sample to produce a 2D image. In particular, a detector array may
be arranged to detect the monochromatic x-rays transmitted through
the object (e.g., a 1D or 2D detector array). The detected
transmitted monochromatic x-rays may be used to compute one or more
images, for example, by performing image reconstruction. If a 3D
image is desired, the x-ray source and detector may be rotated
around the object to detect monochromatic x-rays transmitted
through the object at a plurality of different view angles about
the object, or the source may be rotated or arranged at different
angles while the detector remains fixed. Alternatively, the object
may be rotated to obtain the x-ray attenuation data at different
view angles. The x-ray data at the plurality of view angles may be
used to reconstruct one or more images using any suitable computed
tomography or computed tomosynthesis techniques (both referred to
herein as CT). Other mechanisms may be used to actuate relative
rotation or angular displacement between the x-ray source and the
object to obtain x-ray attenuation data from a number of projection
or view angles, as the aspects of the invention are not limited in
this respect. It should be appreciated that some configuration will
require the detector(s) to rotate in concert with the x-ray source
to acquire the attenuation data.
[0043] The inventor has appreciated that it is beneficial to choose
a material for the anode in the x-ray tube that will generate
characteristic emission lines with energies that are larger than
the energies of the monochromatic lines to be generated by the
fluorescent target. This will improve the x-ray yield from the
fluorescent target, but it is not a requirement on the embodiments
of the invention. According to some embodiments, one or more x-ray
lenses may be used to more efficiently collect the broad spectrum
x-ray radiation emitted from the anode and focus the radiation onto
a relatively small spot on the fluorescent target (e.g., the broad
spectrum radiation may be focused on a compact region of the
fluorescent target). For example, a glass capillary optic may be
positioned between the anode and the fluorescent target to collect
and focus the x-ray radiation. Use of one or more lenses may remove
the need for an aperture between the fluorescent target and the
sample. Since the optics will collect a larger amount of the x-rays
emitted by the x-ray tube, the power of the x-ray tube may be
reduced. The decrease in x-ray tube power may allow the apparatus
to be air-cooled instead of water-cooled, further reducing the
complexity and cost of the x-ray apparatus. It should be
appreciated that one or more lens may be positioned between the
fluorescent target and the sample to focus the monochromatic
x-rays, either alone or in combination with optics arranged between
the anode and the fluorescent target.
[0044] According to some embodiments, the x-ray apparatus in FIG. 9
is capable of generating pulsed monochromatic x-ray radiation.
Pulsed x-ray radiation may be advantageous in reducing and/or
eliminating motion artifacts in the resulting images due to motion
of a human subject during radiation exposure. For example, imaging
a beating heart using continuous x-ray radiation may cause blur in
the resulting image(s) as the heart is in different
locations/configurations at different times during the cardiac
cycle. By pulsing the x-ray source, the x-ray radiation may be
synced to the cardiac cycle such that imaging is performed at
approximately the same time during the cardiac cycle to reduce
and/or eliminate motion blur. It should be appreciated that any
portion of the cardiac cycle may be imaged using such techniques.
In addition, the breathing of a subject may result in similar
motion artifacts and pulsing the x-ray source according to a
predetermined exposure schedule may compensate for the motion
caused by the subject's breathing (e.g., imaging may be performed
during the approximate same time of the respiratory cycle). It
should be appreciated that pulsing the radiation may be synced with
other causes of subject motion, as the aspects of the invention are
not limited in this respect.
[0045] According to some embodiments, x-ray pulsing is performed
within the x-ray tube. For example, a timing circuit may be
implemented to electronically open and close the circuit that
generates the electrons flow from the cathode (e.g., filament) to
the anode (target). This timing circuit may be configured to open
and close the circuit according to any desired timing sequence. For
example, the timing circuit may be controlled using a microcomputer
having a clock to open and close the circuit according to a
programmed timing sequence, which may be programmed to generate
pulsed x-ray radiation according to any desired or any number of
desired timing sequences.
[0046] According to some embodiments, x-ray pulsing is performed on
the x-ray radiation itself. For example, a chopper (e.g., a
rotating chopper) may be arranged to alternately block and pass
either the broad spectrum radiation emitted from the first target
and/or the monochromatic radiation emitted from the fluorescent
target to achieve pulsed radiation according to a desired timing
sequence. Dual choppers may be implemented to alternately block and
pass both the broad spectrum radiation and the monochromatic
radiation to achieve pulsed radiation at a desired timing sequence
or at any number of desired timing sequences. It should be
appreciated that other methods of generating pulsed x-ray radiation
may be used, as the aspects of the invention are not limited in
this respect. It should be appreciated that techniques for
electronically pulsing the electron beam may be combined with
techniques for blocking/passing the x-ray radiation, as the aspects
of the invention are not limited for use with any type or
combination of techniques for generating pulsed radiation.
[0047] According to some embodiments, the x-ray system comprises
multiple fluorescent targets so that monochromatic x-rays of
different energies can be produced. Such an x-ray system may be
configurable to select one of the multiple fluorescent targets to
produce monochromatic x-rays at a desired energy level. According
to some embodiments, the fluorescent target utilized may be
selected dynamically so that monochromatic radiation of different
energies may be alternately provided.
[0048] It should be appreciated that there are other ways in which
monochromatic x-rays may be generated that may be suitable for
determining information about chemical composition of subject
matter of interest. For example, while Bragg crystals and
synchrotron systems may have associate drawbacks, these methods of
generating monochromatic x-rays may be suitable in some
circumstances, and the techniques described herein are not limited
for use with any particular method or apparatus for generating
monochromatic radiation.
[0049] Following below are more detailed descriptions of various
concepts related to, and embodiments of, methods and apparatus for
determining information about chemical composition. It should be
appreciated that various aspects of the invention described herein
may be implemented in any of numerous ways. Examples of specific
implementations are provided herein for illustrative purposes only.
In addition, the various aspects of the invention described in the
embodiments below may be used alone or in any combination, and are
not limited to the combinations explicitly described herein.
[0050] FIG. 10 illustrates a method of using monochromatic x-ray
radiation to determine information about the chemical composition
of subject matter of interest through which the monochromatic x-ray
radiation passes, in accordance with some embodiments. In act 1010,
monochromatic x-ray radiation is provided to irradiate an object
having internal subject matter of interest. Monochromatic x-ray
radiation may be generated in any suitable manner. For example,
monochromatic x-ray radiation may be generated by irradiating a
fluorescent target with a broad spectrum source to produce
fluorescent monochromatic radiation in the manner discussed above.
Monochromatic radiation may be generated in other ways, such as by
using Bragg crystals or using a synchrotron, though these
techniques may not be suitable for all applications. Any other
suitable method of generating monochromatic radiation may be used,
as the aspects are not limited in this respect.
[0051] In act 1020, monochromatic x-rays transmitted through the
object are detected. As discussed above, conventional detectors
used in x-ray imaging systems are generally suitable and may be
used to obtain x-ray information for determining information about
the chemical composition of subject matter of interest internal to
the object. For example, detector arrays used for CT (either
computed tomography or tomosynthesis) may be used. The detector
array may be a one-dimensional or two-dimensional detector array
and may be rotatable or fixed as desired. For example, the detector
array may be rotatable in conjunction with the x-ray source to
provide monochromatic x-rays and detect transmitted monochromatic
x-ray radiation at different view angles about the object of
interest (e.g., to perform tomography), or the detector array may
remain fixed and the x-ray source arranged at different angles
about the object (e.g., to perform tomosynthesis). Alternatively,
the detector array may be fixed and the object may be rotated to
obtain x-ray information from different view angles. In either
geometry, 2D and/or 3D x-ray information may be obtained. It should
be appreciated that any array of detectors (i.e., one or more
detectors) capable of detecting the intensity of x-rays impinging
on the detector array may be used, as the aspects are not limited
to any particular type or number of detectors or any particular
detector array or detector array geometry.
[0052] In act 1030, information about the chemical composition of
subject matter internal to the object of interest is obtained. For
example, a measure of the atomic weight or effective atomic weight
of subject matter internal to the object of interest may be
computed. A measure of the mass absorption characteristic of
subject matter of interest may be computed to facilitate
identifying an element, compound, molecule and/or tissue type
present in subject matter of interest. In particular, one or more
computed mass absorption characteristics may be obtained and
utilized to identify a characteristic curve corresponding to known
material to ascertain that the known material is present, as
discussed in further detail below. Information about the chemical
composition of subject matter can be any information about the
chemical makeup or composition of the subject matter.
[0053] Aspects of the inventor's insight derive from the fact that
elements on the Periodic chart have unique atomic structure forming
the basis for a normalized mass absorption coefficient, .mu./.rho.,
where .rho. is the density. The product of .mu./.rho. and .rho.
yields the mass absorption coefficient, .mu., whose functional
variation with x-ray energy is also unique. This relationship is
illustrated in FIG. 11 where .mu., with dimensions of cm-1, is
plotted for materials with atomic numbers 6-30 (carbon through
zinc, respectively) with respective atomic weights 12-65.
[0054] In particular, FIG. 11 illustrates characteristic curves
1110a-1110h for zinc, iron, calcium, phosphorus, aluminum oxide,
magnesium, sodium and carbon, respectively. FIG. 11 also
illustrates the energy of monochromatic x-ray emitted from four
different fluorescent targets. In particular, energy 1120a
corresponds to the energy of fluorescent x-rays (K.alpha. x-rays)
emitted from a molybdenum target, energy 1120b corresponds to the
energy of fluorescent x-rays emitted from a palladium target,
energy 1120c corresponds to the energy of fluorescent x-rays
emitted from a silver target, and energy 1120b corresponds to the
energy of fluorescent x-rays emitted from a tin target. The circles
1130a-1130e indicate .mu. values computed using techniques
described herein, as discussed in further detail below. The
characteristic curves of .mu. as a function of x-ray energy can be
viewed as the "signature" for the corresponding material or
substance. It should be appreciated that material comprising a
combination of elements (e.g., compounds, molecules, tissue, tissue
anomalies, etc.) too will exhibit a characteristic curve that can
be used as a signature for the corresponding material. Thus,
characteristic curves of material of interest can be obtained and
utilized to identify when corresponding material is present by
using the monochromatic x-ray techniques described in further
detail below.
[0055] As discussed above, the inventor has appreciated that the
use of monochromatic x-ray radiation permits the energy in the
x-ray radiation to be known a priori, thus eliminating the need to
measure the energy in transmitted x-rays. Because the x-ray energy
is known from the monochromatic x-rays generated, .mu.-values may
be computed as a measure of the mass absorption coefficient of
material using attenuation information provided by detected
monochromatic x-rays transmitted through the material. The computed
.mu.-values can be compared to characteristic curves of material of
interest to identify the closest characteristic curve. According to
some embodiments, a measure of the mass absorption coefficient may
be computed for material through which monochromatic x-ray
radiation has passed and is detected using the following
relationship:
.mu.(E)=-[ln(I.sub.1/I.sub.0)]/L (1).
[0056] FIG. 12 schematically illustrates the relationship of
equation (1). In particular, I.sub.0 is a measure of the intensity
of the monochromatic radiation prior to interaction with the object
being exposed (e.g., the intensity of the x-rays emitted by the
monochromatic x-ray source) and I.sub.1 is the measured intensity
of monochromatic x-rays exiting the object. Thus, I.sub.1/I.sub.0
provides the measured attenuation fraction resulting from the
absorption of x-rays by subject matter internal to the object. In
the expression in equation (1), L is the path length through the
object along a ray between the monochromatic x-ray source and the
respective detector, and E is the known x-ray energy of the
monochromatic x-rays. Thus, a value for .mu. may be determined from
the detected intensity of the monochromatic x-rays transmitted
through the object. This .mu.-value may be compared to
characteristics curves at energy E (i.e., the known energy of the
monochromatic x-rays) to identify the closest characteristic curve
to determine that the material corresponding to the identified
characteristic curve is present.
[0057] FIG. 11 illustrates a number of .mu.-values using the above
described technique. For example, .mu.-value 1130a was computed
from attenuation information obtained by providing monochromatic
x-rays emitted from a silver target to irradiate an object
containing iron. Likewise, .mu.-value 1130b was computed from
attenuation information obtained by providing monochromatic x-rays
emitted from a silver target to irradiate an object containing
aluminum oxide (Al.sub.2O.sub.3). In a similar manner, the other
.mu.-values were similarly obtained using the monochromatic
radiation techniques discussed herein. As shown, the obtained
.mu.-values fall on or close to the characteristic curve for the
corresponding substance such that the correct characteristic curve
can be identified to determine information about the chemical
composition of corresponding regions of an object.
[0058] The inventor has further appreciated that information about
the chemical composition of subject matter of interest may also be
determined when embedded in other material. Take as an example the
circumstance in which a mass inside a larger volume is discovered
during a routine x-ray imaging examination. FIG. 12 schematically
illustrates this scenario where a mass 1215 (which may present as
an elliptical region in a 2-D x-ray image, such as a 2-D x-ray
image of a 3-D x-ray image) is located within a larger region 1210.
To determine information about the chemical composition of the mass
1215, the attenuation fraction I.sub.1/I.sub.0 may be computed in
the manner discussed above. Additionally, the attenuation fraction
I.sub.2/I.sub.0 corresponding to the mass may also be computed in a
similar fashion.
[0059] The length of the path through mass 1215, illustrated as
.DELTA.x in FIG. 12, may be needed and may be obtained directly
from the x-ray imaging data in which the mass was detected. For
example, the x-ray imaging data may be automatically analyzed to
ascertain the boundary or a dimension of the identified mass from
which .DELTA.x may be determined. Any one or more image processing
techniques may be utilized to identify the boundary of the mass or
any dimension of interest thereof (e.g., .DELTA.x), as the aspects
are not limited in this respect. For example, the boundary and/or
any desired dimension of the mass may be determined based on one or
any combination of techniques including computing edge information,
performing region growing, using deformable models, etc.
Alternatively, an operator such as a radiologist may indicate the
bounds of the identified mass or a desired dimension thereof on the
image itself. This information may be used to determine .DELTA.x.
The boundary of the mass or any desired dimension may be identified
in other ways, such as a combination of automated analysis and
manual input from an operator.
[0060] According to some embodiments, once .DELTA.x has been
obtained (or any pertinent dimension of the embedded mass), a
measure of the mass absorption coefficient may be computed from
attenuation information using the following relationship:
.mu.(E)=[ln A-ln B]/.DELTA.r (2)
[0061] In the expression in equation (2), A=I.sub.1/I.sub.0,
B=I.sub.2/I.sub.0, .DELTA.x is the path length through the embedded
mass and E is the energy of the monochromatic x-rays. The computed
.mu..sub.2 may then be compared to the characteristic curves at
energy E to identify the closest curve, thereby determining
information about the chemical composition of the embedded mass. In
this manner, the chemical composition of a localized region of
interest can be determined. As discussed above, a region of
interest may be identified from one or more acquired x-ray images
(e.g., may be identified by a radiologist). Such x-ray images may
be acquired using conventional broad spectrum techniques, or may be
acquired using monochromatic x-rays using techniques discussed in
the foregoing and described in further detail in the '534 patent
incorporated by reference herein. When monochromatic x-rays are
used for imaging internal structure of an object, the information
needed to determine information about the chemical composition of
subject matter within an object is available using the same x-ray
attenuation information acquired for imaging purposes. In this
respect, a single acquisition procedure allows for both imaging and
evaluating chemical composition, providing a low dose process for
ascertaining varied diagnostic information about subject matter of
interest.
[0062] According to some embodiments, a .mu.-value at a single
energy is determined and compared to characteristic curves to
identify the closest curve. While doing so may be suitable in many
circumstances, the inventor has appreciated that determining
.mu.-values at multiple energies may provide a more discriminating
means of identifying the closet characteristic curve in some
instances. For example, while the computed .mu.-values in FIG. 11
lie closest to the correct curve, x-ray attenuation information
from in-vivo acquisition procedures may be noisy and/or may include
combinations of material so that computed .mu.-values fall
somewhere in between two characteristic curves, with the
possibility that a computed .mu.-value will fall closer to an
incorrect characteristic curve than the correct characteristic
curve. By computing multiple .mu.-values at different respective
energies, multiple .mu.-values can be used together to decrease the
chances that the incorrect characteristic curve is matched. For
example, two .mu.-values provide slope information that may be
useful in better distinguishing between different characteristic
curves. By increasing the number of .mu.-values further, higher
level information and/or more accurate curve matching techniques
may be used to facilitate accurately identifying the correct
characteristic curve.
[0063] Additionally, the exemplary characteristic curves
illustrated in FIG. 11 are non-overlapping. However, characteristic
curves of different materials and/or compound materials may have
overlapping characteristic curves. In such circumstances, it may be
difficult to match a single computed .mu.-value to the correct
characteristic curve when characteristic curves are close together,
cross and/or overlap. However, multiple .mu.-values obtained at
different energy levels may provide discriminating information that
facilitates the identification of the correct characteristic curve.
According to some embodiments, a plurality of .mu.-values computed
at respective different monochromatic x-ray energies are obtained
and used to identify the closest matching characteristic curve to
determine information about the chemical composition of the subject
matter of interest. To do so, the above described techniques may be
repeated using monochromatic x-rays at different respective
energies.
[0064] As discussed above, the energy of monochromatic x-rays may
be changed by using different material for the fluorescent target.
Accordingly, a plurality of .mu.-values may be obtained using a
system that has multiple fluorescent targets. It should be
appreciated that any number of fluorescent targets may be used to
allow for obtaining any number of .mu.-values to facilitate the
identification of the correct characteristic curve. The x-ray
attenuation information at different monochromatic x-ray energies
may be obtained in any manner. For example, the x-ray attenuation
information at different energies may be obtained serially by using
a first fluorescent target to obtain the needed x-ray attenuation
information at a first energy and subsequently using a second
fluorescent target to obtain the needed x-ray attenuation
information at a second energy. Alternatively, x-ray attenuation
information at different energies may be obtained in parallel by
alternating between the first target and the second target in a
time slicing sequence. Other methods of obtaining x-ray attenuation
information at multiple monochromatic x-ray energies may be used,
as the aspects are not limited in this respect.
[0065] According to some embodiments, monochromatic x-rays are
provided at multiple energies simultaneously and a detector array
capable of detecting the energy of impinging x-rays (e.g., a
detector array having suitable spectral resolution for the selected
energies) is utilized to determine the energy of the x-rays
corresponding to one or more computed .mu.-values for use in
comparing to relevant characteristic curves. In this way, a single
acquisition procedure can produce x-ray attenuation information at
any number of x-ray energies to facilitate determining information
about the chemical composition of subject matter of interest using
the techniques described herein, thereby reducing the amount of
time needed and providing a relatively low dose solution to
determining chemical composition information and/or performing
low-dose monochromatic x-ray imaging.
[0066] Multiple .mu.-values may be used in other ways to facilitate
identifying the correct characteristic curve. For example, the
difference of two .mu.-values may provide a more sensitive measure
to match a characteristic curve. FIG. 13 illustrates a diagram of
the difference between the absorption coefficient at two energies
plotted as a function of atomic weight. Three sets of data are
presented; (circles): .mu.(17.5 kev)-.mu.(25 kev),(diamonds):
.mu.(20.2 kev)-.mu.(25 kev), and (triangles): .mu.(22 kev)-.mu.(25
kev). The sensitivity for determining the atomic weight of heavier
elements or compounds increases as the difference in the
monochromatic energies gets larger. Thus, selection of the
monochromatic energies may be selected intelligently to assist in
identifying the presence of particular subject matter of
interest.
[0067] It should be appreciated that characteristic curves may be
generated for any material of interest, including elements,
compounds, molecules, tissue, anomalous tissue such as tumors, etc.
The above described techniques may be used to determine when such
material is present by comparing one or more computed .mu.-values
obtained at one or more x-ray energies to characteristic curves for
the material of interest. According to some embodiments, the one or
more computed .mu.-values are compared to a characteristic curve to
determine whether the respective material is present. For example,
the one or more computed .mu.-values may be compared to a
characteristic curve for tumor material to determine whether tumor
material is present and, if the signatures of benign and malignant
tumors are different, to determine the nature of the tumor. In this
respect, the techniques described herein may be used to avoid
biopsy procedures. As another example, one or more computed
.mu.-values may be used in non-biological applications to detect
the presence of materials (asbestos, radium, rust, etc.) in
structural objects. Thus, it should be appreciated that the
techniques described herein can be used to detect the presence of
any material of interest for which characteristic information
(e.g., a characteristic curve) can be obtained, as the techniques
are not limited for use with any particular application and/or
material.
[0068] An illustrative implementation of a computer system 1500
that may be used to implement one or more of the techniques
described herein is shown in FIG. 15. For example, a computer
system 1500 may be used to implement any one or more of the
techniques described in connection with the method illustrated in
FIG. 10. Computer system 1500 may include one or more processors
1510 and one or more non-transitory computer-readable storage media
(e.g., memory 1520 and one or more non-volatile storage media
1530). The processor 1510 may control writing data to and reading
data from the memory 1520 and the non-volatile storage device 1530
in any suitable manner, as the aspects of the invention described
herein are not limited in this respect. Processor 1510, for
example, may be a processor on a mobile device, a personal
computer, a server, an embedded system, etc., that can connect to,
or that is part of, an x-ray system (e.g., the x-ray system
illustrated in FIG. 9).
[0069] To perform functionality and/or techniques described herein,
the processor 1510 may execute one or more instructions stored in
one or more computer-readable storage media (e.g., the memory 1520,
storage media, etc.), which may serve as non-transitory
computer-readable storage media storing instructions for execution
by processor 1510. Computer system 1500 may also include any other
processor, controller or control unit needed to route data, perform
computations, perform I/O functionality, etc. For example, computer
system 1500 may include any number and type of input functionality
to receive data and/or may include any number and type of output
functionality to provide data, and may include control apparatus to
perform I/O functionality.
[0070] In connection with performing techniques described herein
(e.g., determining information about the chemical composition of
subject matter of interest, performing x-ray imaging, or both), one
or more programs configured to receive x-ray information as input,
process the input or otherwise execute functionality described
herein may be stored on one or more computer-readable storage media
of computer system 1500. In particular, some portions of a system
configured to determine information about the chemical composition
of subject matter and/or to reconstruct one or more x-ray images
may be implemented as instructions stored on one or more
computer-readable storage media. Processor 1510 may execute any one
or combination of such programs that are available to the processor
by being stored locally on computer system 1500 or accessible over
a network. Any other software, programs or instructions described
herein may also be stored and executed by computer system 1500.
Computer system 1500 may represent the computer system on an x-ray
imaging device and/or may represent a computer system connected to
an x-ray imaging device, for example, via one or more networks.
Computer system 1500 may be implemented as a standalone computer,
server, part of a distributed computing system configured to
communicate with one or more other computers connected to a
network, etc.
[0071] The terms "program" or "software" are used herein in a
generic sense to refer to any type of computer code or set of
processor-executable instructions that can be employed to program a
computer or other processor to implement various aspects of
embodiments as discussed above. Additionally, it should be
appreciated that according to one aspect, one or more computer
programs that when executed perform methods of the disclosure
provided herein need not reside on a single computer or processor,
but may be distributed in a modular fashion among different
computers or processors to implement various aspects of the
disclosure provided herein.
[0072] Processor-executable instructions may be in many forms, such
as program modules, executed by one or more computers or other
devices. Generally, program modules include routines, programs,
objects, components, data structures, etc. that perform particular
tasks or implement particular abstract data types. Typically, the
functionality of the program modules may be combined or distributed
as desired in various embodiments.
[0073] Also, data structures may be stored in one or more
non-transitory computer-readable storage media in any suitable
form. For simplicity of illustration, data structures may be shown
to have fields that are related through location in the data
structure. Such relationships may likewise be achieved by assigning
storage for the fields with locations in a non-transitory
computer-readable medium that convey relationship between the
fields. However, any suitable mechanism may be used to establish
relationships among information in fields of a data structure,
including through the use of pointers, tags or other mechanisms
that establish relationships among data elements
[0074] The above-described embodiments of the present invention can
be implemented in any of numerous ways, and the examples described
herein are not limiting. In addition, various aspects of the
present invention may be used alone, in combination, or in a
variety of arrangements not specifically discussed in the
embodiments described in the foregoing and is therefore not limited
in its application to the details and arrangement of components set
forth in the foregoing description or illustrated in the
drawings.
[0075] Also, various inventive concepts may be embodied as one or
more processes, of which multiple examples have been provided. The
acts performed as part of each process may be ordered in any
suitable way. Accordingly, embodiments may be constructed in which
acts are performed in an order different than illustrated, which
may include performing some acts concurrently, even though shown as
sequential acts in illustrative embodiments.
[0076] All definitions, as defined and used herein, should be
understood to control over dictionary definitions, and/or ordinary
meanings of the defined terms.
[0077] As used herein in the specification and in the claims, the
phrase "at least one," in reference to a list of one or more
elements, should be understood to mean at least one element
selected from any one or more of the elements in the list of
elements, but not necessarily including at least one of each and
every element specifically listed within the list of elements and
not excluding any combinations of elements in the list of elements.
This definition also allows that elements may optionally be present
other than the elements specifically identified within the list of
elements to which the phrase "at least one" refers, whether related
or unrelated to those elements specifically identified. Thus, as a
non-limiting example, "at least one of A and B" (or, equivalently,
"at least one of A or B," or, equivalently "at least one of A
and/or B") can refer, in one embodiment, to at least one,
optionally including more than one, A, with no B present (and
optionally including elements other than B); in another embodiment,
to at least one, optionally including more than one, B, with no A
present (and optionally including elements other than A); in yet
another embodiment, to at least one, optionally including more than
one, A, and at least one, optionally including more than one, B
(and optionally including other elements); etc.
[0078] The phrase "and/or," as used herein in the specification and
in the claims, should be understood to mean "either or both" of the
elements so conjoined, i.e., elements that are conjunctively
present in some cases and disjunctively present in other cases.
Multiple elements listed with "and/or" should be construed in the
same fashion, i.e., "one or more" of the elements so conjoined.
Other elements may optionally be present other than the elements
specifically identified by the "and/or" clause, whether related or
unrelated to those elements specifically identified. Thus, as a
non-limiting example, a reference to "A and/or B", when used in
conjunction with open-ended language such as "comprising" can
refer, in one embodiment, to A only (optionally including elements
other than B); in another embodiment, to B only (optionally
including elements other than A); in yet another embodiment, to
both A and B (optionally including other elements); etc.
[0079] Use of ordinal terms such as "first," "second," "third,"
etc., in the claims to modify a claim element does not by itself
connote any priority, precedence, or order of one claim element
over another or the temporal order in which acts of a method are
performed. Such terms are used merely as labels to distinguish one
claim element having a certain name from another element having a
same name (but for use of the ordinal term).
[0080] The phraseology and terminology used herein is for the
purpose of description and should not be regarded as limiting. The
use of "including," "comprising," "having," "containing",
"involving", and variations thereof, is meant to encompass the
items listed thereafter and additional items.
[0081] Having described several embodiments of the techniques
described herein in detail, various modifications, and improvements
will readily occur to those skilled in the art. Such modifications
and improvements are intended to be within the spirit and scope of
the disclosure. Accordingly, the foregoing description is by way of
example only, and is not intended as limiting. The techniques are
limited only as defined by the following claims and the equivalents
thereto.
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