X-ray modulator

Abstract

An X-ray modulator for use with an X-ray tube includes an enclosed chamber having a window portion and a side portion in gaseous communication with each other. The enclosed chamber includes chamber walls, wherein the chamber walls of the window portion are thinner than the chamber walls of the side portion. The X-ray modulator further includes a pressure modulation device disposed within the side portion of the enclosed chamber adapted to modulate pressure within the enclosed chamber, and an absorption gas located within the enclosed chamber for absorbing X-ray radiation.

Description

Technical Field

[0001] This invention relates to the field of X-ray imaging, and more specifically, to the field of spectral computed tomography imaging. Background Technology

[0002] Spectroscopic imaging is becoming an increasingly popular imaging method in X-ray computed tomography. Spectroscopic imaging is performed by applying different energy settings (such as different voltages) to the X-ray tube, which results in different X-ray spectra being delivered to the subject. In this way, quantitative image data can be obtained, allowing the scanned object (such as the subject's body) to be broken down into different substances and tissues.

[0003] One method for performing spectral imaging is kVp switching, where two different voltages are alternately applied to the X-ray tube. Rapid kVp switching, which quickly changes the supply voltage to the X-ray tube, is an efficient and inexpensive way to perform spectral imaging. The overall measurement results can be divided into two distinct sine waves, one including measurements obtained using the high-energy spectrum and the other using the low-energy spectrum.

[0004] The quality of spectral CT images can be compromised by suboptimal spectral separation of photons generated at different energy levels (also known as electrical tension). Specifically, at higher energies, a higher proportion of low-energy photons are generated, causing the average photon energy of the high-energy image to become closer to the average photon energy of the low-energy image, thus reducing spectral separation.

[0005] Therefore, a means is needed to reduce the number of low-energy photons incident on the subject during the high-energy imaging phase of spectral imaging methods.

[0006] US Patent Application US2014 / 328453A1 discloses a CT device that includes multiple filter elements comprising gas-filled chambers. Summary of the Invention

[0007] This invention is defined by the claims.

[0008] According to an example of one aspect of the invention, an X-ray modulator is provided for use with an X-ray tube, the X-ray modulator comprising:

[0009] An enclosed chamber having a window portion and a side portion, wherein the window portion is in gas communication with the side portion, and the enclosed chamber includes a chamber wall, wherein the chamber wall of the window portion is thinner than the chamber wall of the side portion.

[0010] A pressure modulation device disposed within a side portion of an enclosed chamber and adapted to modulate the pressure within the enclosed chamber; and

[0011] An absorbing gas, located within an enclosed chamber, is used to absorb X-ray radiation.

[0012] This X-ray modulator provides a method for absorbing unwanted low-energy photons during spectral CT imaging, thereby improving the spectral separation of photons and thus improving the quality of the obtained spectral CT images.

[0013] By providing an absorbent in gaseous form, the high insertion speed required for the absorbent can be achieved without adversely affecting image quality due to the shadows cast by alternative absorbents moving across the field of view.

[0014] In one embodiment, the absorbent gas includes one or more of the following:

[0015] Xenon; and

[0016] Iodine vapor.

[0017] In one embodiment, the X-ray modulator includes a heating element.

[0018] In this way, the pressure within the enclosed chamber can be regulated with greater accuracy.

[0019] In one embodiment, the absorbing gas is iodine vapor, and the X-ray modulator includes a protective material disposed on the chamber wall within an enclosed chamber, and optionally, the protective material is silver.

[0020] In this way, the enclosed chamber is protected from the corrosive effects of iodine.

[0021] In one embodiment, the chamber walls on opposite sides of the enclosed chamber are separated by a given separation distance, wherein the average separation distance at the window portion is less than the average separation distance at the side portion, the side portion having a tapered structure having a minimum separation distance adjacent to the window portion and a maximum separation distance away from the window portion, the minimum separation distance being greater than or equal to the average separation distance at the window portion, and optionally, a pressure modulator is positioned within the side portion in the region with the maximum separation distance.

[0022] In this way, the pressure increase within the window section can be amplified, thereby reducing the required pressure increase within the side section. Therefore, the pressure generated by the pressure modulator within the side section can be amplified to the maximum extent within the window section.

[0023] In one embodiment, the pressure modulator includes one or more of the following:

[0024] speaker;

[0025] Transducer elements; and

[0026] Electroactive polymers.

[0027] In one embodiment, the pressure modulator is adapted to modulate pressure over an average pressure range of 1 MPa to 35 MPa, the average pressure being the average pressure within the enclosed chamber.

[0028] In one embodiment, the chamber wall includes:

[0029] The first material at the side portion includes one or more of the following:

[0030] aluminum;

[0031] Titanium; and

[0032] steel;

[0033] The second material at the window portion includes one or more of the following:

[0034] beryllium;

[0035] Boron carbide;

[0036] Boron nitride;

[0037] magnesium;

[0038] Diamonds; and

[0039] aluminum.

[0040] In one embodiment, the X-ray modulator further includes a pump adapted to generate an absorption gas flow between the side portion and the window portion.

[0041] In this way, the temperature of the absorbed gas can be regulated, thereby preventing the gas from overheating under continuous X-ray radiation.

[0042] In one embodiment, the X-ray modulator includes a mechanical resonator structure.

[0043] In this way, the pressure within the enclosed chamber can be further increased without the need for additional active drive hardware.

[0044] In one embodiment, the X-ray modulator includes multiple side portions, each side portion having a pressure modulator.

[0045] In one embodiment, the X-ray modulator has an elliptical cross-section, the cross-section of the side portion is an elliptical ring, and the cross-section of the window portion is an ellipse located within the elliptical ring of the side portion.

[0046] In one embodiment, the X-ray modulator is disposed within a vacuum chamber.

[0047] In this way, the amplitude of the sound generated by the X-ray modulator, as heard by the user, can be reduced.

[0048] According to an example of one aspect of the present invention, a computed tomography (CT) imaging system is provided, comprising:

[0049] An X-ray tube suitable for generating X-ray radiation, the X-ray tube having an emission window for allowing X-ray radiation to pass through;

[0050] The X-ray modulator described above, wherein the window portion of the X-ray modulator is positioned adjacent to the emission window of the X-ray tube, such that the X-ray radiation generated by the X-ray tube passes through the window portion of the X-ray modulator;

[0051] Detectors suitable for detecting X-ray radiation; and

[0052] A processing unit suitable for controlling CT imaging systems.

[0053] In one embodiment, the system is adapted to operate an X-ray tube under a first electrical tension and a second electrical tension, the first electrical tension being higher than the second electrical tension, and a pressure modulator is adapted to modulate the pressure within an enclosed cavity between a first pressure and a second pressure, wherein the first pressure is higher than the second pressure, and the X-ray tube and the pressure modulator are operated such that the first pressure occurs simultaneously with the first electrical tension, and the second pressure occurs simultaneously with the second electrical tension.

[0054] In this way, the optical attenuation characteristics of the absorbing gas, determined by the pressure of the absorbing gas, can be controlled to increase the number of absorbed low-energy photons during the high electrical tension phase (when many low-energy photons are not desired) and decrease photon absorption during the low electrical tension phase (when photon absorption is undesirable).

[0055] These and other aspects of the invention will become apparent and elucidated with reference to the embodiments described below. Attached Figure Description

[0056] To better understand the invention and to more clearly show how to implement it, reference is now made to the accompanying drawings by way of example only, wherein:

[0057] Figure 1 A CT imaging system is schematically illustrated.

[0058] Figure 2 An example of an X-ray modulator according to one aspect of the present invention is shown;

[0059] Figure 3 It shows Figure 2 X-ray modulators and X-ray tubes;

[0060] Figure 4A A three-dimensional representation of an X-ray modulator according to one aspect of the invention is shown; and

[0061] Figure 4B A three-dimensional representation of an X-ray modulator according to another aspect of the present invention is shown. Detailed Implementation

[0062] The present invention will be described with reference to the accompanying drawings.

[0063] It should be understood that while the detailed description and specific embodiments illustrate exemplary models of the apparatus, systems, and methods, they are for illustrative purposes only and not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems, and methods of the present invention will be better understood from the following description, the appended claims, and the accompanying drawings. It should be understood that these drawings are schematic only and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to denote the same or similar parts.

[0064] The present invention provides an X-ray modulator for use with an X-ray tube, comprising an enclosed chamber having a window portion and side portions in gas communication with each other. The enclosed chamber includes chamber walls, wherein the chamber wall of the window portion is thinner than the chamber wall of the side portions.

[0065] The X-ray modulator also includes a pressure modulation device disposed in a side portion of the enclosed chamber, which is adapted to modulate the pressure within the enclosed chamber, and an absorbing gas located within the enclosed chamber for absorbing X-ray radiation.

[0066] A conventional computed tomography (CT) scanner includes an X-ray radiation generator mounted on a rotating gantry, opposite one or more integrating detectors. The X-ray generator rotates around an examination area located between the X-ray generator and the one or more detectors, emitting (typically multi-colored) radiation that passes through the examination area and the subject and / or object positioned within it. The one or more detectors detect the radiation passing through the examination area and generate signals (or projection data) indicative of the examination area and the subject and / or object positioned therein. Projection data refers to the raw detector data and can be used to form a projection sine curve, a visual representation of the projection data captured by the detectors.

[0067] The reconstructor is typically used further to process the projection data and reconstruct a volumetric image of the subject or object. The volumetric image consists of multiple cross-sectional image slices, each generated from the projection data through a tomographic reconstruction process, for example, by applying a filtered backprojection algorithm. The reconstructed image data is essentially an inverse Radon transform of the original projection data.

[0068] Figure 1 System 100 is schematically shown, including imaging system 102, such as a CT scanner configured for spectral (multi-energy) imaging. Imaging system 102 includes a generally fixed gantry 104 and a rotating gantry 106 rotatably supported by the fixed gantry 104 and rotating about a Z-axis around an examination area 108. Subject support 110 (such as an examination table) supports an object or subject within the examination area 108.

[0069] Radiation source 112 (such as an X-ray tube) is rotatably supported by a rotating gantry 106, rotates together with the rotating gantry 106, and emits radiation through the examination area 108. In one example, radiation source 112 comprises a single broad-spectrum X-ray tube. In another example, radiation source 112 comprises a single X-ray tube configured to switch between at least two different emission voltages (e.g., 80 kVp and 140 kVp) during scanning. In yet another example, radiation source 112 comprises two or more X-ray tubes configured to emit radiation with different average spectra. In still another example, radiation source 112 comprises a combination thereof.

[0070] A radiation-sensitive detector array 114 is positioned at an angular arc opposite to a radiation source 112 opposite the examination region 110. The radiation-sensitive detector array 114 detects radiation traversing the examination region 108 and generates an electrical signal (projection data) indicative of it. When the radiation source 112 comprises a single broad-spectrum X-ray tube, the radiation-sensitive detector array 112 includes an energy-resolved detector (e.g., a direct-conversion photon-counting detector, at least two sets of scintillators with different spectral sensitivities (multilayer), etc.). In kVp switching and multi-tube configurations, the detector array 114 may include a single-layer detector, a direct-conversion photon-counting detector, and / or a multilayer detector. A direct-conversion photon-counting detector may include a conversion material such as CdTe, CdZnTe, Si, Ge, GaAs, or other direct-conversion materials. Examples of multilayer detectors include dual-layer detectors, such as those described in U.S. Patent 7,968,853B2, filed April 10, 2006, entitled "Double Decker Detector for Spectral CT".

[0071] The reconstructor 116 receives spectral projection data from the detector array 114 and reconstructs spectral volumetric image data, such as sCCTA image data, high-energy images, low-energy images, photoelectric images, Compton scattering images, iodine images, calcium images, virtual non-contrast images, bone images, soft tissue images, and / or images of other basic substances. The reconstructor 116 can also reconstruct non-spectral volumetric image data, for example, by combining spectral projection data and / or spectral volumetric image data. Generally, the spectral projection data and / or spectral volumetric image data will include data from at least two different energy and / or energy ranges.

[0072] The computing system 118 serves as an operator console. The console 118 includes human-readable output devices (such as a monitor) and input devices (such as a keyboard, mouse, etc.). Software residing on the console 118 allows the operator to interact with and / or operate the scanner 102 via a graphical user interface (GUI) or other means. The console 118 further includes a processor 120 (e.g., a microprocessor, controller, central processing unit, etc.) and a computer-readable storage medium 122, which includes temporary media such as physical storage devices, but excludes non-transitory media. The computer-readable storage medium 122 includes instructions 124 for operating the imaging system. The processor 120 is configured to execute the instructions 124. The processor 120 may also be additionally configured to execute one or more computer-readable instructions carried by a carrier wave, signal, and / or other temporary media. In one variant, the processor 120 and the computer-readable storage medium 122 are part of another computing system (separate from the computing system 118).

[0073] As mentioned above, a common problem in spectroscopic imaging is the suboptimal spectral separation of photons generated at different energies. The inventors have recognized that, in principle, low-energy photons generated during the high-energy imaging phase can be eliminated using an absorber material with approximately 50 atoms. Sufficient photons are generated at the high imaging energies so that the use of such an absorber does not significantly increase scan time or available dose. However, the required insertion velocity of the absorber material in front of the X-ray tube's emission window exceeds 100 m / s, making it difficult to incorporate such an absorber into the X-ray tube.

[0074] Figure 2 An example of an X-ray modulator 200 for use with an X-ray tube is shown.

[0075] The X-ray modulator 200 includes an enclosed chamber 210 having a window portion 220 and a side portion 230. Figure 1In the example shown, the X-ray modulator includes two identical side portions positioned on either side of the window portion. Any number or more side portions can be positioned around the window portion to form an X-ray modulator according to the invention.

[0076] The window section is in gas communication with the side section. In other words, the side section and the window section form a continuous, enclosed chamber.

[0077] The enclosed chamber 210 is defined by a chamber wall 240, wherein the chamber wall of the window portion is thinner than the chamber wall of the side portion. The chamber wall can be made of two different materials, a first material used in the chamber wall of the side portion and a second material used in the chamber wall of the window portion.

[0078] The first material (in the chamber wall 240 of the side portion 230) can be a rigid material, such as aluminum, titanium, steel, and similar materials. The first material does not need to be permeable to X-ray radiation, and can therefore be as thick as reasonably possible to ensure that the movement of the X-ray modulator 200 is minimized when the internal pressure of the X-ray modulator changes during use.

[0079] The second material (in the chamber wall 240 of the window portion 220) needs to be thinner than the first material to be sufficiently transparent to X-rays. Furthermore, the reduced thickness means the second material can be harder than the first material to maintain the integrity of the X-ray modulator under pressure changes within the enclosed chamber 210. The second material can be: beryllium; boron carbide; boron nitride; magnesium; diamond; or aluminum. Additionally, the window portion can be curved and / or have reinforcing ribs to further improve its rigidity.

[0080] The X-ray modulator 200 further includes a pressure modulation device 250 disposed within a side portion 230 of the enclosed chamber 210 and adapted to modulate the pressure within the enclosed chamber. The pressure modulator may be: a loudspeaker; a transducer element, such as a piezoelectric device or a magnetostrictive device; an electroactive polymer; or any suitable means for modulating the pressure within the enclosed chamber. The pressure modulation device should be resistant to the absorbent gas or a mixture of gases within the enclosed chamber.

[0081] The X-ray modulator 200 further includes an absorbing gas located within an enclosed chamber 210 for absorbing X-ray radiation, particularly absorbing low-energy photons generated during high-energy imaging periods.

[0082] By using gas as the absorbent, the problem of rapid absorbent insertion is solved because the gas flow rate can reach the order of the speed of sound. Furthermore, due to the gradual increase in pressure, the shadows cast by the absorbent moving across the field of view do not adversely affect image quality.

[0083] As described above, at least two electrical tensions are generated at the X-ray tube for spectral CT imaging. At lower electrical tensions, due to the lower efficiency of the X-ray tube at low tensions, it is desirable to absorb as few photons as possible; however, at higher electrical tensions, a large number of unwanted low-energy photons need to be absorbed. Therefore, the optical attenuation of the absorbing gas needs to be controlled based on the electrical tension of the X-ray tube. As discussed below, the optical attenuation of the absorbing gas is determined by the density of the absorbing gas, which in turn is determined by the gas's pressure and temperature.

[0084] Therefore, under lower electrical tension, the pressure modulation device can be operated to keep the pressure in the enclosed cavity as low as possible, while under higher electrical tension, the pressure modulation device can be operated to make the pressure reach the desired level to absorb low-energy photons.

[0085] Since gas pressure cannot change at an infinite rate, this means that pressure changes within the enclosed chamber will be sinusoidal in nature. Therefore, pressure changes can correspond to voltage changes within the X-ray tube, with lower pressures occurring during periods of lower electrical tension and higher pressures during periods of higher electrical tension.

[0086] In practice, the time ratio between low and high electrical tension is not 1:1 to achieve optimal spectral separation while maintaining sufficient X-ray flux from the X-ray tube to complete image formation within the desired time. However, when the time ratio is close to 1:1, pressure variation is the simplest approach. By varying the average pressure within the X-ray modulator, as well as the pressure amplitude, the optimal conditions for the entire imaging system can be brought closer to a 1:1 time ratio operation. In this case, the entire system can utilize a simple single-frequency resonance, which is advantageous because it reduces the drive power requirements of the pressure modulation device.

[0087] In other words, during spectral imaging, the CT imaging system can be adapted to operate the X-ray tube under a first electrical tension and a second electrical tension, wherein the first electrical tension is higher than the second electrical tension.

[0088] Furthermore, the pressure modulator can be adapted to modulate the pressure within the enclosed chamber between a first pressure and a second pressure, wherein the first pressure is higher than the second pressure.

[0089] The system can operate the X-ray tube and pressure modulator so that the first pressure and the first electric tension occur simultaneously, and the second pressure and the second electric tension occur simultaneously.

[0090] If a 1:1 time ratio cannot be achieved between the two electrical tensions, the X-ray modulator can be designed to operate at multi-frequency resonance. The desired pressure wave can be decomposed into a Fourier series, the first two to ten components of which can be generated by the pressure modulation device. The X-ray modulator can resonate at or near the harmonics of the Fourier series.

[0091] The optical attenuation of the absorbing gas is determined by its density, which in turn is determined by its pressure and temperature. This is theoretically proven below; however, it should be noted that the following paragraphs neglect the partially adiabatic properties of the absorbing gas due to pressure changes. In practice, X-ray modulators operate at frequencies between 1 kHz and 5 kHz, and heat exchange with the environment surrounding the X-ray modulator is minimal. Therefore, the behavior of the absorbing gas can be approximated as isothermal; however, in reality, the gas will exhibit behavior somewhere between adiabatic and isothermal. To provide a simplified explanation of the behavior of the absorbing gas within the enclosed chamber, isothermal behavior will be assumed in the following explanation.

[0092] The ideal gas equation is appropriate in this case because the absorbent gas is held within the enclosed chamber, and the ideal gas equation is given below:

[0093] PV = nRT (1)

[0094] Where: P is the pressure within the enclosed chamber; V is the volume of the enclosed chamber; n is the number of moles of the absorbent gas present in the enclosed chamber; R is the ideal gas constant; and T is the temperature of the absorbent gas.

[0095] The optical attenuation of matter is described by the Beer-Lamber law. For a physical material containing a single attenuating species with uniform concentration along the optical path, the Beer-Lamber law can be written as:

[0096] A=εcl (2)

[0097] Where: A is the optical attenuation number; ε is the molar attenuation coefficient of the absorbing gas; c is the concentration of the absorbing gas in the enclosed cavity; and l is the optical path length through the absorbing gas.

[0098] The concentration c of the absorbed gas is given by the following formula:

[0099]

[0100] By replacing 'c' in formula (2) with formula (3) and rearranging the equations, we obtain the following relationship:

[0101]

[0102] By replacing V in formula (1) with formula (4) and rearranging the equations, we obtain the following relationship:

[0103]

[0104] Therefore, the amount of light attenuation caused by the absorbing gas is determined by the pressure of the absorbing gas. As mentioned above, the formula provided describes the behavior of the absorbing gas under isothermal approximation. In practice, to accurately control the behavior of the absorbing gas, changes in temperature and heat transfer will need to be considered.

[0105] A suitable gas for absorption is xenon, or a mixture of xenon and other gases (such as nitrogen), which achieves the desired optical attenuation at, for example, a pressure of 10 MPa with an optical path length of only one to a few millimeters. The average pressure within the enclosed chamber can be in the range of 10 MPa, with a peak pressure reaching 35 MPa and a minimum pressure approximately 1 MPa, ranging from 1 MPa to 35 MPa. The pressure ratio between the peak and minimum pressure points within the window portion can be at least 1.5 and can be greater than 3. To achieve the desired pressure, the pressure modulation device (which can be an electrodynamic loudspeaker) can operate at frequencies in the 3 kHz range. The pressure modulation device can operate at frequencies that match the harmonics of the kVp switching frequency. The X-ray modulator can be enclosed in an additional vacuum chamber to provide acoustic isolation.

[0106] Alternative absorber gas materials can be iodine vapor. In this case, to prevent damage to the X-ray modulator due to exposure to corrosive iodine, the X-ray modulator can include a protective material, such as silver, disposed on the chamber wall within the enclosed chamber. Furthermore, if iodine is used, a heating mechanism can be incorporated into the X-ray modulator to maintain the desired average pressure within the enclosed chamber. Iodine vapor can be used in combination with other gases, such as nitrogen, xenon, etc.

[0107] As described above, the pressure modulation device may include a loudspeaker; however, a conventional loudspeaker may not be able to raise the pressure within the enclosed chamber to 10 MPa. To achieve the desired pressure within the enclosed chamber, the X-ray modulator can generate resonance at the desired operating frequency of the frequency modulation device, for example, up to 5 kHz. The operating frequency of the frequency modulation device can also be synchronized with the frequency of the CT gantry rotation. Furthermore, the X-ray modulator can generate multiple resonances to accommodate different CT gantry rotations.

[0108] In addition, the X-ray modulator 200 may have a horn structure that amplifies the pressure wave generated by the pressure modulation device 250 toward the window portion 220.

[0109] In other words, the chamber walls on opposite sides of the enclosed chamber 210 are separated by a given separation distance, wherein the average separation distance D at the window portion 220 is... w Less than the average separation distance D at the lateral portion 230 s The side portion has a tapered or flared structure, with a minimum separation distance D at the position of the adjacent window portion. smin And the maximum separation distance D is located in the part farthest from the window. smax The minimum separation distance is greater than or equal to the average separation distance of the window portion. Since the pressure modulation device 250 is positioned within the side portion in the region with the maximum separation distance, the pressure wave generated within this region will be constrained as the separation distance between the chamber walls decreases. Therefore, an increase in pressure within the side portion will result in a proportionally larger increase in pressure within the window portion.

[0110] In addition, the X-ray modulator may include a mechanical resonator structure. The mechanical resonator structure can be adapted to tune the X-ray modulator's resonance to a desired frequency. Alternatively, or in addition to a mechanical resonator structure, resonance tuning can also be achieved by changing the temperature of the surrounding chamber, for example, by means of a heating element, especially if the temperature change introduces a light gas such as water vapor through evaporation.

[0111] During use, the average pressure within the enclosed chamber is brought to a suitable value to achieve the desired optical attenuation. For example, if the separation distance D of the window portion... w A width of 1 mm and a pressure of approximately 10 MPa may be appropriate. However, if a larger separation distance is provided within the window portion 220, the pressure can be reduced because this provides a larger optical path length for radiation to pass through, the optical path length depending on the light attenuation, as shown in Equation (5) above.

[0112] Figure 3 It shows Figure 2 The X-ray modulator 200 and X-ray tube 300 shown are illustrated.

[0113] X-ray radiation 310 generated in the X-ray tube 300 passes through the window portion of the X-ray modulator 200. As described above, when X-rays are generated at higher energy levels during spectral imaging operation, unwanted low-energy photons are also generated and leave the X-ray tube. When the radiation from the X-ray tube passes through the window portion of the X-ray modulator 200, the low-energy photons are absorbed by the absorbing gas in the enclosed chamber of the X-ray modulator, thereby generating modulated X-rays 320 that consist only of or primarily consist of high-energy photons. In this way, the spectral separation between low and high energies is increased, thereby improving the quality of the spectral image.

[0114] The window portion of the X-ray modulator 200 can withstand a high heat flux from the X-ray tube 300 (specifically, the X-ray anode within the tube). Therefore, the X-ray modulator may include means to facilitate cooling of the absorbent gas. For example, to facilitate cooling, the absorbent gas can be controlled by a steady flow through the window portion of the X-ray modulator, for example, by a pump that delivers the absorbent gas between the side portions of the X-ray modulator, thereby resulting in an absorbent gas flow through the window portion.

[0115] Figure 4A A three-dimensional representation of an X-ray modulator 400 according to one aspect of the present invention is shown.

[0116] exist Figure 4A In the example shown, the X-ray modulator 400 includes a window portion 410 and a single side portion 420.

[0117] Figure 4B A partial three-dimensional representation of an X-ray modulator 430 according to another aspect of the present invention is shown.

[0118] exist Figure 4B In the example shown, the X-ray modulator 430 has an elliptical cross-section (half of which is shown) and includes an elliptical window portion 440 located within an elliptical ring-shaped side portion 450 surrounding the window portion. Figure 4B The annular shape of the X-ray modulator shown helps the enclosed chamber achieve the desired wave pressure. Pressure waves generated within the side portions of the annular X-ray modulator and traveling towards the window portion are concentrated as they approach the center of the ring, thereby increasing the amplitude of the pressure waves. This is especially true for X-ray modulators having multiple pressure modulation devices positioned within the side portions of the modulator to surround the outer ring.

[0119] By studying the accompanying drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments when carrying out the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality.

[0120] The fact that certain measures are described only in different dependent claims does not mean that a combination of these measures cannot be used to exert an advantage.

[0121] If the word “suitable” is used in the claims or description, it should be noted that the word “suitable” is intended to be equivalent to the word “configured as”.

[0122] No reference numerals in the claims should be construed as limiting the scope.

Claims

1. An X-ray modulator (200) for use with an X-ray tube, said X-ray modulator comprising: An enclosed chamber (210) having a window portion (220) and a side portion (230), wherein the window portion is in gas communication with the side portion, and the enclosed chamber includes a chamber wall (240), wherein the chamber wall of the window portion is thinner than the chamber wall of the side portion; A pressure modulator (250) is disposed within the side portion of the enclosed chamber and is adapted to modulate the pressure within the enclosed chamber. and An absorbing gas, located within the enclosed cavity, is used to absorb X-ray radiation.

2. The X-ray modulator (200) according to claim 1, wherein, The absorbent gas includes one or more of the following: Xenon; and Iodine vapor.

3. The X-ray modulator (200) according to any one of claims 1 to 2, wherein, The X-ray modulator includes a heating element.

4. The X-ray modulator (200) according to any one of claims 1 to 2, wherein, The absorbing gas is iodine vapor, and the X-ray modulator includes a protective material disposed on the chamber wall (240) within the enclosed chamber, and optionally, the protective material is silver.

5. The X-ray modulator (200) according to any one of claims 1 to 2, wherein, The chamber walls on opposite sides of the enclosed chamber (210) are separated by a given separation distance, wherein the average separation distance (D) at the window portion is... w The distance is less than the average separation distance at the side portion (230), which has a tapered structure and a minimum separation distance (D) at a position adjacent to the window portion (220). smin And has the maximum separation distance (D) at a position farthest from the window portion. smax The minimum separation distance is greater than or equal to the average separation distance at the window portion, and optionally, the pressure modulator (250) is positioned within the side portion (230) with the maximum separation distance (D). smax Within the area of ​​).

6. The X-ray modulator (200) according to any one of claims 1 to 2, wherein, The pressure modulator (250) includes one or more of the following: speaker; Transducer elements; and Electroactive polymers.

7. The X-ray modulator (200) according to any one of claims 1 to 2, wherein, The pressure modulator (250) is adapted to modulate the pressure within an average pressure range of 1 MPa to 35 MPa, the average pressure being the average pressure within the enclosed chamber.

8. The X-ray modulator (200) according to any one of claims 1 to 2, wherein, The chamber wall (240) includes: The first material at the side portion (230) comprises one or more of the following: aluminum; Titanium; and steel; The second material at the window portion (220) comprises one or more of the following: beryllium; Boron carbide; Boron nitride; magnesium; Diamonds; and aluminum.

9. The X-ray modulator (200) according to any one of claims 1 to 2, wherein, The X-ray modulator further includes a pump adapted to generate an absorption gas flow between the side portion (230) and the window portion (220).

10. The X-ray modulator (200) according to any one of claims 1 to 2, wherein, The X-ray modulator includes a mechanical resonator structure.

11. The X-ray modulator (200) according to any one of claims 1 to 2, wherein, The X-ray modulator includes multiple side sections, each side section having a pressure modulator.

12. The X-ray modulator (200) according to any one of claims 1 to 2, wherein, The X-ray modulator has an elliptical cross-section, the cross-section of the side portion is an elliptical ring, and the cross-section of the window portion is an ellipse located within the elliptical ring of the side portion.

13. The X-ray modulator (200) according to any one of claims 1 to 2, wherein, The X-ray modulator is placed in a vacuum chamber.

14. A computed tomography (CT) imaging system, comprising: An X-ray tube (300) suitable for generating X-ray radiation, the X-ray tube having an emission window for allowing the X-ray radiation to pass through; The X-ray modulator (200) according to any one of claims 1 to 2, wherein the window portion of the X-ray modulator is positioned adjacent to the emission window of the X-ray tube, such that the X-ray radiation generated by the X-ray tube passes through the window portion of the X-ray modulator; Detectors suitable for detecting X-ray radiation; and A processing unit suitable for controlling the CT imaging system.

15. The CT imaging system according to claim 14, wherein, The system is adapted to operate the X-ray tube under a first electrical tension and a second electrical tension, the first electrical tension being higher than the second electrical tension, and the pressure modulator is adapted to modulate the pressure within the enclosed cavity between a first pressure and a second pressure, wherein the first pressure is higher than the second pressure, and the X-ray tube and the pressure modulator are operated such that the first pressure and the first electrical tension occur simultaneously, and the second pressure and the second electrical tension occur simultaneously.

Images