CN109100775B - Energy spectrum correction method and device for double-layer detector - Google Patents
Energy spectrum correction method and device for double-layer detector Download PDFInfo
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Abstract
The invention discloses an energy spectrum correction method and device of a double-layer detector, which comprises the following steps: determining ray energy spectrum distribution, an energy section threshold value and the upper layer material thickness of a double-layer detector according to the configuration and rated parameters of the double-energy CT, wherein the energy section threshold value divides the ray energy spectrum distribution into a low energy section and a high energy section; determining an average linear attenuation coefficient according to the energy spectrum distribution of the rays and an energy segment threshold; and determining the photo-generated charge amount of the low-energy section according to the photo-generated charge amount of the upper layer material, the photo-generated charge amount of the lower layer material, the average linear attenuation coefficient and the thickness of the upper layer material. The invention can correct the energy spectrum aiming at different double-layer detectors or different types of double-layer detectors, remove the redundant charges generated by the high-energy trailing effect on the upper-layer detector, obtain accurate photo-generated charge quantity and detection result and improve the quality of image reconstruction.
Description
Technical Field
The present invention relates to the field of imaging, and more particularly, to a method and an apparatus for correcting an energy spectrum of a dual-layer detector.
Background
The dual-energy CT (computed tomography) equipment utilizes the attenuation information of X-rays with two different energies in a detected object to perform projection imaging, and can accurately obtain the atomic number and the electron density of the scanned substance by combining a dual-energy reconstruction algorithm, thereby realizing more accurate substance separation and qualitative analysis. At present, the dual-energy CT has been widely applied to the fields of security inspection, medical diagnosis, nondestructive inspection (especially, inspection of solder joint defects of a PCB (printed circuit board), and quality inspection of package of components such as BGA (solder ball array package), CSP (chip size package), etc.). The X-ray detector is a key part of the dual-energy CT accurate imaging, and the accuracy of the CT imaging is directly determined by the capability of the detector for detecting rays with different energies in a distinguishing manner. The double-layer detector is an X-ray energy spectrum detector which is widely applied at present. The double-layer detector is composed of an upper layer and a lower layer of scintillator materials of different types, and each layer of detector only generates excitation action on X-ray photons within a certain energy range. In the double-energy imaging process, the bulb tube emits X rays with certain kVp (kilovolt peak value) continuous energy distribution, an upper detector is firstly excited after the X rays pass through an object, X ray photons in a low-energy area in the X rays are absorbed and photogenerated charges are proportionally released, and a lower detector absorbs part of high-energy photons in the X rays and also releases the photogenerated charges. The photo-generated charge information of each layer can be used for resolving projection data of high and low energy spectral bands and is used for dual-energy imaging.
The high and low energy projection information acquired by the dual-layer detector has strict consistency in time and space, but is due to the "high energy smearing" of the X-rays absorbed in the detector. "high-energy smearing" refers to the phenomenon that X-ray photons within the high-energy band, although primarily concentrated and absorbed in the lower detector, also decay and excite the photo-generated charge (referred to as "redundant charge" for short in this disclosure) as they pass through the upper detector. The high-energy and low-energy projection data of the dual-energy CT imaging are derived from the photo-generated charge amount in each layer of the detector, and the analysis precision of the low-energy section X-ray energy spectrum can be reduced by the absorption of high-energy photons in the upper-layer detector.
Aiming at the problem that in the prior art, due to the high-energy tailing effect, redundant charges are generated in an upper detector, so that the dual-energy CT imaging precision is reduced, no effective solution is provided at present.
Disclosure of Invention
In view of this, an object of the embodiments of the present invention is to provide an energy spectrum correction method and apparatus for a dual-layer detector, which can perform energy spectrum correction for different dual-layer detectors or different types of dual-layer detectors, remove redundant charges generated by a high-energy smearing effect on an upper-layer detector, and obtain accurate photo-generated charge amount and detection result.
In view of the above object, an aspect of the embodiments of the present invention provides an energy spectrum correction method for a dual-layer detector, including the following steps:
determining ray energy spectrum distribution, an energy section threshold value and the upper layer material thickness of a double-layer detector according to the configuration and rated parameters of the double-energy CT, wherein the energy section threshold value divides the ray energy spectrum distribution into a low energy section and a high energy section;
determining an average linear attenuation coefficient according to the energy spectrum distribution of the rays and an energy segment threshold;
and determining the photo-generated charge amount of the low-energy section according to the photo-generated charge amount of the upper layer material, the photo-generated charge amount of the lower layer material, the average linear attenuation coefficient and the thickness of the upper layer material.
In some embodiments, the bi-layer detector includes an upper layer of material that absorbs the low energy range radiation and a portion of the high energy range radiation and a lower layer of material that absorbs the remaining portion of the high energy range radiation.
In some embodiments, determining the average linear attenuation coefficient from the radiation energy spectrum distribution and the energy segment threshold comprises:
determining a range interval of a high-energy section, wherein the upper limit of the high-energy section is an energy maximum value determined according to the energy spectrum distribution of the rays, and the lower limit of the high-energy section is an energy section threshold value;
determining linear attenuation coefficients of ray photons with energy of the energy maximum value and the energy range threshold value in the detector, and averaging the linear attenuation coefficients of the ray photons with the energy of the energy maximum value and the energy range threshold value in the detector to determine an average linear attenuation coefficient; or averaging the energy maximum and the energy segment threshold, and determining the average linear attenuation coefficient according to the linear attenuation coefficient of the ray photon with the average energy in the detector.
In some embodiments, determining the amount of photo-generated charge for the low energy segment based on the amount of photo-generated charge for the upper layer material, the amount of photo-generated charge for the lower layer material, the average linear attenuation coefficient, and the thickness of the upper layer material comprises:
acquiring the photo-generated charge quantity of an upper layer material and the photo-generated charge quantity of a lower layer material through actual detection;
determining a charge ratio according to the average linear attenuation coefficient and the thickness of the upper layer material, wherein the charge ratio is the ratio of the charges excited by the rays of the high-energy section in the upper layer material to the charges excited by the rays of the high-energy section in the lower layer material;
and determining the quantity of the photo-generated charges of the low-energy section according to the quantity of the photo-generated charges of the upper layer material, the quantity of the photo-generated charges of the lower layer material and the ratio of the quantity of the charges.
In some embodiments, the ratio of the amount of charge
Photo-generated charge quantity Q of low energy section1＝Q′1-Q′2＝Q′1-kQ2；
Wherein the content of the first and second substances,
is an average linear attenuation coefficient, l isThickness of upper layer Material, Q'1Is the photo-generated charge amount of the upper layer material, Q'2The quantity of photo-generated charge, Q, generated in the superstrate for the rays of the high-energy range2Is the photo-generated charge of the underlying material.
In some embodiments, the radiation used for dual energy CT is X-rays, dual energy CT uses a bulb to emit the X-rays, and the dual layer detector uses at least two different types of scintillator materials to receive the photo-generated charges.
In another aspect of the embodiment of the invention, an energy spectrum correction device of a double-layer detector is also provided, and the method is used.
The invention has the following beneficial technical effects: according to the energy spectrum correction method and device for the double-layer detector, provided by the embodiment of the invention, through the technical scheme that the ray energy spectrum distribution, the energy section threshold value and the upper layer material thickness of the double-layer detector are determined, the average linear attenuation coefficient is determined by using a linear fitting method, and the photo-generated charge amount of a low-energy section is determined, the energy spectrum correction can be carried out on different double-layer detectors or different types of double-layer detectors, redundant charges generated by a high-energy trailing effect on the upper layer detector are removed, the accurate photo-generated charge amount and detection result are obtained, and the quality of image reconstruction is improved.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic flow chart of an energy spectrum calibration method for a double-layer detector according to the present invention;
FIG. 2 is a schematic diagram of an X-ray energy spectrum distribution curve provided by the present invention;
FIG. 3 is a schematic diagram of the structure and the absorption and region of the double-layered detector provided by the present invention for rays of different energy bands;
fig. 4 is a schematic hardware structure diagram of an embodiment of the computer device for executing the energy spectrum correction method of the double-layer detector provided by the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following embodiments of the present invention are described in further detail with reference to the accompanying drawings.
It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are used for distinguishing two entities with the same name but different names or different parameters, and it should be noted that "first" and "second" are merely for convenience of description and should not be construed as limitations of the embodiments of the present invention, and they are not described in any more detail in the following embodiments.
In view of the above object, a first aspect of the embodiments of the present invention proposes a first embodiment of a method capable of performing energy spectrum correction for different double-layer detectors or different types of double-layer detectors. Fig. 1 is a schematic flow chart of a first embodiment of the energy spectrum correction method of the double-layer detector provided by the invention.
The energy spectrum correction method of the double-layer detector comprises the following steps:
step S101, determining ray energy spectrum distribution, an energy segment threshold value and the upper layer material thickness of a double-layer detector according to the configuration and rated parameters of the double-energy CT, wherein the energy segment threshold value divides the ray energy spectrum distribution into a low energy segment and a high energy segment;
step S103, determining an average linear attenuation coefficient according to the ray energy spectrum distribution and the energy segment threshold;
and step S105, determining the photo-generated charge amount of the low-energy section according to the photo-generated charge amount of the upper layer material, the photo-generated charge amount of the lower layer material, the average linear attenuation coefficient and the thickness of the upper layer material.
In some embodiments, the bi-layer detector includes an upper layer of material that absorbs the low energy range radiation and a portion of the high energy range radiation and a lower layer of material that absorbs the remaining portion of the high energy range radiation.
The dual-energy CT emits radiation having the same energy spectral distribution as the object to be detected, which is continuous. When a ray passes through an object, a part of energy in the ray is absorbed by the object, and the absorbed spectral line (in terms of photon energy of the ray) is related to the physicochemical properties of the detected object, for example, a photon with a specific energy can jump a specific electron located at a specific orbit in a specific substance to another orbit. The physicochemical properties of the absorbed spectral lines and the detected objects are known in the prior art and/or can be determined by a limited number of experimental measurements and are therefore not further described here.
The embodiment of the invention divides the energy spectrum distribution of the rays into a low energy section and a high energy section. These two segments are essentially referred to as "dual energies" of the dual energy CT. Correspondingly, a double-layer detector is also provided for "dual energy". In an embodiment of the invention, the upper layer material of the bi-layer detector is designed to absorb radiation photons in the low energy band, whereas the lower layer material is designed to absorb radiation photons in the high energy band, in contrast, as shown in fig. 3. The technical problem to be solved by embodiments of the present invention arises from the fact that the radiation photons first pass through the upper layer material and then through the lower layer material, which results in that a part of the radiation photons of the high energy band is absorbed by the upper layer material. The energy spectrum correction provided by the embodiment of the invention approximately estimates and removes redundant charges generated in an upper layer material due to a high-energy tailing effect according to the absorption rule of rays so as to obtain more accurate low-energy spectrum information.
The energy segment threshold divides the ray energy spectral distribution into low energy segments and high energy segments as previously described. Referring to FIG. 2, the energy spectrum interval of the radiation of the embodiment of the present invention is [0, E ]n]The threshold of the energy band is EmThus, the low energy segment interval is [0, E ]m]The high energy interval is [ E ]m,En]. It should be noted, however, that the graph shown in FIG. 2 is merely a schematic representation that may have peaks and valleys, and is not representative of, nor used in a qualitative sense for, the actual absorption line.
In some embodiments, determining the average linear attenuation coefficient from the radiation energy spectrum distribution and the energy segment threshold comprises:
determining a range interval of a high-energy section, wherein the upper limit of the high-energy section is an energy maximum value determined according to the energy spectrum distribution of the rays, and the lower limit of the high-energy section is an energy section threshold value;
determining linear attenuation coefficients of ray photons with energy of the energy maximum value and the energy range threshold value in the detector, and averaging the linear attenuation coefficients of the ray photons with the energy of the energy maximum value and the energy range threshold value in the detector to determine an average linear attenuation coefficient; or averaging the energy maximum and the energy segment threshold, and determining the average linear attenuation coefficient according to the linear attenuation coefficient of the ray photon with the average energy in the detector.
The "average linear attenuation coefficient" is a processing method for approximating a linear attenuation coefficient to a constant value. It has been determined that the relationship between linear attenuation coefficient and photon energy can be linearly fitted (e.g., using mathematical means such as least squares), i.e., generating an attenuation coefficient-ray energy straight line. In the case of sufficiently short high-energy segments, the corresponding attenuation factor can be determined within a small range or can be directly regarded as a constant value. The embodiment of the invention determines the average linear attenuation coefficient as the fixed value, so that the calculated amount is greatly reduced (hereinafter, the negative exponential function of the linear attenuation coefficient is used for multiple times), and the detection accuracy of the dual-energy CT is not greatly influenced.
It will be appreciated that if linear attenuation is considered as a function, two forms of first calculating attenuation then averaging and first averaging then calculating attenuation are used in embodiments of the invention (i.e. averaging and then calculating attenuation first)
Or
Where μ (·) is the decay function). Under the aforementioned straight line model, both are equivalent, and those skilled in the art can freely take various forms depending on the computational force limitation or the computational device factor. In addition, the average value can be obtainedIncluding various means (arithmetic, geometric, harmonic, logarithmic, etc.) and ratiometric points.
In some embodiments, determining the amount of photo-generated charge for the low energy segment based on the amount of photo-generated charge for the upper layer material, the amount of photo-generated charge for the lower layer material, the average linear attenuation coefficient, and the thickness of the upper layer material comprises:
acquiring the photo-generated charge quantity of an upper layer material and the photo-generated charge quantity of a lower layer material through actual detection;
determining a charge ratio according to the average linear attenuation coefficient and the thickness of the upper layer material, wherein the charge ratio is the ratio of the charges excited by the rays of the high-energy section in the upper layer material to the charges excited by the rays of the high-energy section in the lower layer material;
and determining the quantity of the photo-generated charges of the low-energy section according to the quantity of the photo-generated charges of the upper layer material, the quantity of the photo-generated charges of the lower layer material and the ratio of the quantity of the charges.
It should be understood that the term photogenerated charge refers to the charge (i.e., the overflow charge of the photoelectric effect) generated by the radiation photons (after passing through the object to be measured) after being absorbed by the double-layer detector. The quantity of photo-generated charge is also linear with the absorbed quantity of the ray photon according to the photoelectric effect, and therefore, the quantity of absorbed ray photon can be calculated.
The charge ratio is the ratio of the amount of redundant charge to the amount of photogenerated charge of the underlying material, and is characterized by the proportion of radiation photons in the high-energy band that are absorbed in the overlying and underlying materials. Meanwhile, the charge quantity ratio is also an exponential function of the product of the average linear attenuation coefficient and the thickness of the upper layer material. Therefore, the embodiment of the present invention represents the amount of photo-generated charge of the low energy section in the form of the amount of photo-generated charge of the upper layer material and the amount of photo-generated charge of the lower layer material (both of which are directly measured).
In some embodiments, the ratio of the amount of charge
Photo-generated charge quantity Q of low energy section1＝Q′1-Q′2＝Q′1-kQ2；
Wherein the content of the first and second substances,
is an average linear attenuation coefficient, l is the thickness of the upper layer material, Q'1Is the photo-generated charge amount of the upper layer material, Q'2The quantity of photo-generated charge, Q, generated in the superstrate for the rays of the high-energy range2Is the photo-generated charge of the underlying material.
Then, the absorption spectral line of the detected object can be further estimated according to the photo-generated charge quantity of the low-energy section, and the real physicochemical property of the detected object can be inferred.
In some embodiments, the radiation used for dual energy CT is X-rays, dual energy CT uses a bulb to emit the X-rays, and the dual layer detector uses at least two different types of scintillator materials to receive the photo-generated charges.
In addition to the above embodiments, the embodiments of the present invention may also be applied to a layered single photon counting type X-ray detector, and the detection accuracy of each layer is improved by removing photo-generated charge data excited by high-energy photons absorbed in other shallow detectors.
It can be seen from the foregoing embodiments that, in the energy spectrum correction method for a double-layered detector provided in the embodiments of the present invention, by determining the radiation energy spectrum distribution, the energy segment threshold, and the upper layer material thickness of the double-layered detector, and using a linear fitting method to determine the average linear attenuation coefficient, the photo-generated charge amount of the low-energy segment is determined, energy spectrum correction can be performed for different double-layered detectors or different types of double-layered detectors, redundant charges generated at the upper layer detector by a high-energy trailing effect are removed, accurate photo-generated charge amount and detection result are obtained, and the quality of image reconstruction is improved.
In view of the above objects, a first aspect of embodiments of the present invention proposes a second embodiment of a method for energy spectrum correction that can be performed for different double-layer detectors or different types of double-layer detectors.
In the embodiment of the invention, the energy range of the ray provided by the emission source of the dual-energy CT is specifically set to be 0keV-14 keV0keV (kilo electron volts), wherein 0keV-80keV is a low energy band X-ray, is absorbed mainly in the upper detector and excites the photo-generated charge Q1(ii) a 80keV-140keV are high energy band X-rays, are absorbed and excited in the underlying detector to a photo-generated charge Q2(ii) a The quantity of photo-generated charge excited in the upper detector by the high-energy-band X-ray photons is Q'2(ii) a The total quantity of photo-generated electric charge excited by the X-ray in the high energy section is Q3(ii) a The thickness of the upper detector scintillator material is l.
The embodiment of the invention defines the average linear attenuation coefficient
To uniformly characterize the average attenuation of the radiation photons in the high energy band in the scintillator detector:
or
The charge quantity ratio k can be expressed as:
Q1can be expressed as:
Q1＝Q′1-Q′2＝Q′1-kQ2
through the steps, Q 'is mixed'1Q 'of'2Is removed, and thus the photogenerated charge information generated by the excitation of the low energy band photons in the upper detector can be accurately obtained.
It can be seen from the foregoing embodiments that, in the energy spectrum correction method for a double-layered detector provided in the embodiments of the present invention, by determining the radiation energy spectrum distribution, the energy segment threshold, and the upper layer material thickness of the double-layered detector, and using a linear fitting method to determine the average linear attenuation coefficient, the photo-generated charge amount of the low-energy segment is determined, energy spectrum correction can be performed for different double-layered detectors or different types of double-layered detectors, redundant charges generated at the upper layer detector by a high-energy trailing effect are removed, accurate photo-generated charge amount and detection result are obtained, and the quality of image reconstruction is improved.
It should be particularly noted that, the steps in the embodiments of the energy spectrum correction method for a dual-layer detector described above can be mutually intersected, replaced, added, and deleted, so that the energy spectrum correction method for a dual-layer detector, which is transformed by these reasonable permutations and combinations, shall also fall within the scope of the present invention, and shall not limit the scope of the present invention to the described embodiments.
In view of the above object, a second aspect of the embodiments of the present invention proposes an embodiment of an apparatus capable of performing energy spectrum correction for different double-layer detectors or different types of double-layer detectors. The energy spectrum correction device of the double-layer detector uses the energy spectrum correction method of the double-layer detector.
It can be seen from the foregoing embodiments that, according to the energy spectrum correction apparatus for a dual-layer detector provided in the embodiments of the present invention, by determining the radiation energy spectrum distribution, the energy segment threshold, and the upper layer material thickness of the dual-layer detector, and using a linear fitting method to determine the average linear attenuation coefficient, the photo-generated charge amount of the low-energy segment is determined, energy spectrum correction can be performed for different dual-layer detectors or different types of dual-layer detectors, redundant charges generated by the upper layer detector due to a high-energy trailing effect are removed, accurate photo-generated charge amount and detection result are obtained, and the quality of image reconstruction is improved.
It should be particularly noted that the above-mentioned embodiment of the energy spectrum correction apparatus for a double-layer detector adopts the embodiment of the energy spectrum correction method for a double-layer detector to specifically describe the working process of each module, and those skilled in the art can easily think that these modules are applied to other embodiments of the energy spectrum correction method for a double-layer detector. Of course, since the steps in the embodiment of the energy spectrum correction method for a dual-layer detector can be mutually intersected, replaced, added, or deleted, the energy spectrum correction device for the dual-layer detector, which is transformed by these reasonable permutations and combinations, shall also fall within the scope of the present invention, and shall not limit the scope of the present invention to the embodiment.
In view of the above object, a third aspect of the embodiments of the present invention proposes an embodiment of a computer device for performing the energy spectrum correction method of a double-layer detector.
The computer device for performing the energy spectrum correction method of the double-layer detector comprises a memory, at least one processor and a computer program stored on the memory and executable on the processor, wherein the processor executes the program to perform any one of the methods.
Fig. 4 is a schematic hardware structure diagram of an embodiment of the computer device for performing the energy spectrum correction method of the double-layer detector according to the present invention.
Taking the computer device shown in fig. 4 as an example, the computer device includes a processor 401 and a memory 402, and may further include: an input device 403 and an output device 404.
The processor 401, the memory 402, the input device 403 and the output device 404 may be connected by a bus or other means, and fig. 4 illustrates an example of a connection by a bus.
The memory 402, which is a non-volatile computer-readable storage medium, may be used to store non-volatile software programs, non-volatile computer-executable programs, and modules, such as program instructions/modules corresponding to the energy spectrum correction method of the dual-layer detector in the embodiments of the present application. The processor 401 executes various functional applications of the server and data processing by running nonvolatile software programs, instructions and modules stored in the memory 402, namely, implements the energy spectrum correction method of the dual-layer probe of the above-described method embodiment.
The memory 402 may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the stored data area may store data created from use of the energy spectrum correction device of the dual layer detector, and the like. Further, the memory 402 may include high speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some embodiments, memory 402 may optionally include memory located remotely from processor 401, which may be connected to local modules via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
The input device 403 may receive input numeric or character information and generate key signal inputs related to user settings and function controls of the energy spectrum correction device of the double-layer detector. The output device 404 may include a display device such as a display screen.
Program instructions/modules corresponding to the energy spectrum correction method of the one or more double-layer detectors are stored in the memory 402 and when executed by the processor 401, perform the energy spectrum correction method of the double-layer detector in any of the above-described method embodiments.
Any of the embodiments of the computer device for performing the method for energy spectrum correction of a two-layer detector may achieve the same or similar effects as any of the corresponding embodiments of the method described above.
Finally, it should be noted that, as will be understood by those skilled in the art, all or part of the processes of the methods of the above embodiments may be implemented by a computer program, which may be stored in a computer-readable storage medium, and when executed, may include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), a Random Access Memory (RAM), or the like. Embodiments of the computer program may achieve the same or similar effects as any of the preceding method embodiments to which it corresponds.
In addition, the apparatuses, devices and the like disclosed in the embodiments of the present invention may be various electronic terminal devices, such as a mobile phone, a Personal Digital Assistant (PDA), a tablet computer (PAD), a smart television and the like, or may be a large terminal device, such as a server and the like, and therefore the scope of protection disclosed in the embodiments of the present invention should not be limited to a specific type of apparatus, device. The client disclosed in the embodiment of the present invention may be applied to any one of the above electronic terminal devices in the form of electronic hardware, computer software, or a combination of both.
Furthermore, the method disclosed according to an embodiment of the present invention may also be implemented as a computer program executed by a CPU, and the computer program may be stored in a computer-readable storage medium. The computer program, when executed by the CPU, performs the above-described functions defined in the method disclosed in the embodiments of the present invention. The above-described method steps and system elements may also be implemented using a controller and a computer-readable storage medium for storing a computer program for causing the controller to implement the functions of the above-described steps or elements.
Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as software or hardware depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosed embodiments of the present invention.
The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with the following components designed to perform the functions described herein: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination of these components. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP, and/or any other such configuration.
In one or more exemplary designs, the functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk, blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, of embodiments of the invention is limited to these examples; within the idea of an embodiment of the invention, also technical features in the above embodiment or in different embodiments may be combined and there are many other variations of the different aspects of an embodiment of the invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, substitutions, improvements, and the like that may be made without departing from the spirit and principles of the embodiments of the present invention are intended to be included within the scope of the embodiments of the present invention.
Claims (9)
1. A method for correcting an energy spectrum of a double-layer detector is characterized by comprising the following steps:
determining ray energy spectrum distribution, an energy segment threshold and upper layer material thickness of a double-layer detector according to configuration and rated parameters of the double-energy CT, wherein the energy segment threshold divides the ray energy spectrum distribution into a low energy segment and a high energy segment;
determining an average linear attenuation coefficient according to the ray energy spectrum distribution and the energy segment threshold;
determining the photo-generated charge amount of the low-energy section according to the photo-generated charge amount of the upper layer material, the photo-generated charge amount of the lower layer material, the average linear attenuation coefficient and the thickness of the upper layer material, and specifically comprising the following steps:
acquiring the photo-generated charge amount of the upper layer material and the photo-generated charge amount of the lower layer material through actual detection;
determining a charge quantity ratio according to the average linear attenuation coefficient and the thickness of the upper layer material, wherein the charge quantity ratio is the ratio of the charges excited by the rays of the high-energy section in the upper layer material to the charges excited by the rays of the high-energy section in the lower layer material;
determining the amount of photo-generated charge of the low energy segment from the amount of photo-generated charge of the upper layer material, the amount of photo-generated charge of the lower layer material, and the charge amount ratio.
2. The method of claim 1, wherein the bi-layer detector comprises the upper layer of material that absorbs the low energy band rays and a portion of the high energy band rays and a lower layer of material that absorbs the remaining portion of the high energy band rays.
3. The method of claim 1, wherein determining an average linear attenuation coefficient from the ray energy spectral distribution and the energy bin threshold comprises:
determining a range interval of the high energy segment, wherein an upper limit of the high energy segment is an energy maximum determined from the ray energy spectral distribution, and a lower limit of the high energy segment is the energy segment threshold;
determining linear attenuation coefficients of the ray photons with the energy of the energy maxima and the energy band thresholds in the detector, and averaging the linear attenuation coefficients of the ray photons with the energy of the energy maxima and the energy band thresholds in the detector to determine the average linear attenuation coefficient.
4. The method of claim 1, wherein determining an average linear attenuation coefficient from the ray energy spectral distribution and the energy bin threshold comprises:
determining a range interval of the high energy segment, wherein an upper limit of the high energy segment is an energy maximum determined from the ray energy spectral distribution, and a lower limit of the high energy segment is the energy segment threshold;
averaging the energy maxima and the energy bin thresholds and determining the average linear attenuation coefficient from the linear attenuation coefficient in the detector for the ray photons having the energy of the average.
5. The method of claim 1, wherein the charge ratio value
Wherein the content of the first and second substances,
is the average linear attenuation coefficient, l is the thickness of the upper layer material, Q'2The quantity of photo-generated charge, Q, generated in the upper layer material for the rays of the high energy band2The photo-generated charge amount of the underlying material.
6. The method of claim 5, wherein the low energy segment has a photo-generated charge Q1＝Q′1-Q′2＝Q′1-kQ2；
Wherein, Q'1Is the photo-generated charge amount, Q 'of the upper layer material'2The quantity of photo-generated charge, Q, generated in the upper layer material for the rays of the high energy band2The photo-generated charge amount of the underlying material.
7. The method of claim 1, wherein the radiation used in the dual energy CT is X-rays and the dual layer detector uses at least two different types of scintillator materials to receive the photo-generated charges.
8. The method of claim 7, wherein the dual energy CT uses a bulb to emit the X-rays.
9. An energy spectrum correction arrangement of a layered detector, characterized in that the energy spectrum correction arrangement is configured to perform an energy spectrum correction using the method according to any of claims 1-8.
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