Radiation imaging system
阅读说明:本技术 辐射成像系统 (Radiation imaging system ) 是由 丹尼·拉普·延·李 于 2019-07-16 设计创作,主要内容包括:本发明公开了辐射成像系统。一种辐射成像系统包括辐射发射装置和辐射成像装置。所述辐射成像装置具有:带有顶表面和底表面的电绝缘层、在所述电绝缘层的顶表面上的顶电极、电耦接到所述电绝缘层的像素单元的阵列、以及连接到所述像素单元的阵列的晶体管的阵列。(The invention discloses a radiation imaging system. A radiation imaging system includes a radiation emitting device and a radiation imaging device. The radiation imaging apparatus has: the array of transistors includes an electrically insulating layer with a top surface and a bottom surface, a top electrode on the top surface of the electrically insulating layer, an array of pixel cells electrically coupled to the electrically insulating layer, and an array of transistors connected to the array of pixel cells.)
1. A radiation imaging apparatus comprising:
an electrically insulating layer having a top surface and a bottom surface;
a top electrode on the top surface of the electrically insulating layer; and
a plurality of pixel cells electrically coupled to the electrically insulating layer and in direct contact with the bottom surface of the electrically insulating layer.
2. The radiation imaging apparatus as set forth in claim 1, wherein each of the plurality of pixel cells includes a charge collection electrode.
3. The radiation imaging apparatus as defined in claim 2, wherein the charge collection electrode is disposed within the electrically insulating layer at the bottom surface of the electrically insulating layer.
4. The radiation imaging apparatus as claimed in claim 2, wherein each of said plurality of pixel cells further comprises a charge storage capacitor and at least one transistor.
5. The radiation imaging apparatus as claimed in claim 4, wherein the plurality of pixel cells are disposed on the bottom surface of the electrically insulating layer.
6. The radiation imaging apparatus as claimed in claim 4, wherein the transistor is coupled between the charge collection electrode and a charge integrating amplifier.
7. The radiation imaging apparatus as claimed in claim 1, wherein said electrically insulating layer has a thickness of at least 0.1 micrometer.
8. A radiation imaging system, comprising:
a radiation emitting device; and
a radiation imaging apparatus configured to receive radiation from the radiation emitting apparatus and generate an image based on the radiation, the radiation imaging apparatus comprising:
an electrically insulating layer having a top surface and a bottom surface;
a top electrode on the top surface of the electrically insulating layer; and
a plurality of pixel cells electrically coupled to the electrically insulating layer and in direct contact with the bottom surface of the electrically insulating layer.
9. The radiation imaging system of claim 8, wherein each of the plurality of pixel cells includes a charge collection electrode, and
wherein the charge collection electrode is disposed within the electrically insulating layer at the bottom surface of the electrically insulating layer.
10. The radiation imaging system of claim 8, wherein the electrically insulating layer is made of one of parylene, BCB benzocyclobutene, and polyimide film KAPTON.
11. The radiation imaging system as set forth in claim 8, wherein the radiation emitting device is an x-ray emitter.
12. The radiation imaging system of claim 8, wherein the radiation emitting device is a charged particle beam emitter.
13. The radiation imaging system of claim 12, wherein the charged particle beam emitter is a proton beam emitter.
14. The radiation imaging system of claim 13, wherein the radiation imaging device is disposed between the charged particle beam emitter and a patient such that a proton beam is emitted toward the patient after passing through the radiation imaging device.
15. The radiation imaging system as claimed in claim 13, wherein the electrically insulating layer has a thickness of at least about 0.1 microns.
16. A method of operating a radiation imaging system, the radiation imaging system comprising: an electrically insulating layer having a top surface and a bottom surface, a top electrode on the top surface of the electrically insulating layer, a plurality of pixel cells electrically coupled to the electrically insulating layer and in direct contact with the bottom surface of the electrically insulating layer, and a transistor connected to each of the plurality of pixel cells, the method comprising:
(1) applying a bias voltage to the top electrode;
(2) receiving charged particles generated based on a beam of radiation directed at the top electrode, wherein the charged particles penetrate the electrically insulating layer and generate a charge signal;
(3) storing the charge signals in storage capacitors such that a plurality of charge signals are stored in a plurality of storage capacitors;
(4) changing the polarity of the gate line bias voltages of the transistors of a row; and
(5) integrating charge from orthogonal data lines, each of the orthogonal data lines connected to a respective storage capacitor among the plurality of storage capacitors.
17. The method of claim 16, wherein step (5) further comprises: the integrated charge is digitized into a value and the value is stored to computer memory.
18. The method of claim 17, wherein the method further comprises:
(6) restoring the polarity of the gate line bias voltage to place the transistors of the row in an "off" state.
19. The method of claim 18, wherein the method further comprises:
(7) the polarity of the gate line bias voltage of the next row is changed to place the transistors in the next row in an "on" state.
20. The method of claim 19, wherein a plurality of charge signals are generated by a plurality of charged particles, the plurality of charge signals being stored in the plurality of storage capacitors, and wherein the method further comprises:
(8) repeating steps (5), (6) and (7) until each charge signal is read out and stored in the computer memory.
21. The method of claim 16, wherein the bias voltage has a magnitude that is no greater than a breakdown voltage of the electrically insulating layer.
22. The method of claim 16, wherein the radiation beam is an x-ray beam.
23. The method of claim 22, wherein the method further comprises: applying the gate line bias voltage to a gate of the transistor prior to receiving the charge signal from the top electrode toward the electrically insulating layer.
24. The method of claim 23, wherein the gate line bias voltage is applied to the gate of the transistor to place the transistor in an "off" state.
25. The method of claim 24, wherein in step (4), the gate line bias voltages of the transistors of the row are reversed in polarity to place all of the transistors in the row in an "on" state.
26. The method of claim 16, wherein the radiation beam is a proton beam.
27. The method of claim 26, further comprising: irradiating a patient with the proton beam after the proton beam passes through the radiation imaging system.
28. The method of claim 26, wherein the electrically insulating layer is at least about 0.1 microns, and wherein the proton beam penetrates through and past the electrically insulating layer.
29. The method of claim 16, wherein the radiation beam is one of an electron beam, a helium ion beam, a carbon ion beam, a heavy ion beam, a muon beam, and a pi-meson beam.
Technical Field
The present invention relates to a radiation imaging system. More particularly, the present invention relates to a radiation imaging system using electrically insulating materials under an applied electric field.
Background
Radiographs have been produced by directly capturing radiographic images as image-wise modulation patterns of electric charges using a radiation-sensitive material layer. The charge is quantified using a regularly arranged array of discrete solid state radiation sensors, depending on the intensity of the incident X-ray radiation, which is generated electrically or optically by the X-ray radiation within the pixelated area.
U.S. patent No.5,319,206 describes a system that employs a layer of photoconductive material to produce an image-level modulated regional distribution of electron-hole pairs that are subsequently converted to corresponding analog pixel (picture element) values by an electro-active device, such as a thin film transistor. U.S. patent No.5,262,649 describes a system that employs a layer of phosphorescent or scintillating material to produce an image-level modulated distribution of photons that are subsequently converted by a photosensitive device (such as an amorphous silicon photodiode) into a corresponding image-level modulated distribution of charge. These solid state systems have the advantage of facilitating repeated exposure to X-ray radiation without consuming and chemically treating the silver halide film.
In systems utilizing photoconductive materials, such as selenium, such as the prior art conventional radiation imaging system 100 shown in fig. 1, a potential is applied to the top electrode 110 to provide an appropriate electric field prior to exposure to image-level modulated X-ray radiation. During exposure to X-ray radiation, electron-hole pairs are generated in the photoconductive layer 190 beneath the dielectric layer 120 in response to the intensity of the image-level modulation pattern of X-ray radiation, and these electron-hole pairs are separated by an applied bias electric field provided by a high voltage power supply. The electron-hole pairs move in opposite directions along the electric field lines toward the opposite surface of the photoconductive layer 190. After X-ray radiation exposure, a charge image is received at the charge collection electrode 130 and stored in the storage capacitor 160 of the
The most popular and technically mature material is amorphous selenium, which has good charge transport properties for both holes and electrons generated by x-rays. However, selenium with atomic number 34 has good x-ray absorption only in the low energy range (typically below 50 KeV). Selenium has a smaller absorption coefficient for higher energy x-rays and therefore a thicker selenium layer is required for adequate x-ray capture. Since the complexity and difficulty of manufacturing good imaging quality amorphous selenium is strongly influenced by selenium thickness, successful x-ray imaging products are limited to lower energy x-ray applications (such as mammography, low energy x-ray crystallography, and low energy non-destructive testing).
For high energy or high intensity x-ray applications, a large number of electron-hole pairs can be generated from each absorbed x-ray photon. When electrons and holes move along an electric field to a charge collection electrode or to a bias electrode, a large number of electrons and/or holes may be trapped in the selenium layer. These trapped charges will alter the local electric field and thus alter the subsequent charge transfer and charge generation efficiency, resulting in shadows of the previous image superimposed on the subsequent image, a phenomenon known as "ghosting". Some image erasing process is typically required to remove these charges and restore the uniform charge conversion characteristics of the selenium layer.
After exposure to the first x-rays, selenium undergoes charge trapping and therefore it suffers from the ghosting effect. Due to these undesirable results, an erase procedure is required to reduce ghosting. K-band radiation from amorphous selenium may also degrade image resolution. Thus, systems that use photoconductive materials between the dielectric layer 120 and the charge collection electrode 130 (such as the prior art shown in FIG. 1) cannot produce high quality (e.g., high resolution) images at the high energy range of x-rays (such as in the range of 100 keV-MeV). In practice, such prior art devices are typically only capable of producing high resolution images over a range up to several tens of keV, such as below 50 keV.
It is therefore desirable to design a radiation imaging system without resolution loss and with minimized ghosting at high radiation energies or high doses.
During radiation therapy using charged particles, the patient is in a high background radiation chamber (there are a large number of background x-rays and gamma rays). In such environments, it is desirable to have a detector that has a high detection efficiency for charged particles, but a low detection efficiency for x-rays or gamma-rays.
One method of radiation therapy is proton therapy, in which a high-energy proton beam is directed at the patient. One advantage of proton therapy in providing therapy is that protons deposit most of their ionizing dose at a specific location within the body and then do not travel further through the body. This effect causes less damage to the tissue surrounding the target. However, since the proton beam does not travel through the body, in proton treatment, protons cannot be detected after passing through the patient, and it is difficult to accurately detect the energy of the proton beam.
There is a need for the physician to know whether the proton beam is irradiated to the desired treatment location and whether the intensity of the proton beam is at the desired level.
Traditionally, it has not been possible to detect or measure proton beams used to treat patients. Instead, a separate proton beam (test beam) is radiated to the detector, and the position and intensity of the beam are detected. A separate proton beam (treatment beam) is irradiated to the patient for treatment.
Fig. 6 provides an example of such a system. As shown in fig. 6, a conventional proton
After the
Disclosure of Invention
A radiation imaging apparatus according to an embodiment of the present invention has: an electrically insulating layer with a top surface and a bottom surface; a top electrode on a top surface of the electrically insulating layer; an array of pixel cells electrically coupled to the electrically insulating layer and in direct contact with a bottom surface of the electrically insulating layer; and an array of transistors connected to the array of pixel cells.
In one aspect of the present invention, there is provided a radiation imaging system having a radiation emitting device and a radiation imaging device, the radiation imaging device including: the pixel structure includes an electrically insulating layer with a top surface and a bottom surface, a top electrode on the top surface of the electrically insulating layer, an array of pixel cells electrically coupled to the electrically insulating layer and in direct contact with the bottom surface of the electrically insulating layer, and an array of transistors connected to the array of pixel cells. Each of the plurality of pixel cells includes a charge collection electrode disposed on a bottom surface of the electrically insulating layer. Each of the plurality of pixel cells further includes a charge storage capacitor and at least one transistor.
The plurality of pixel cells are electrically coupled to the electrically insulating layer without an x-ray semiconductor. A transistor is coupled between the charge collection electrode and the charge integrating amplifier.
In another aspect of the invention, a method of operating a radiation imaging system having: an electrically insulating layer with a top surface and a bottom surface; a top electrode on a top surface of the electrically insulating layer; an array of pixel cells electrically coupled to the electrically insulating layer and in direct contact with a bottom surface of the electrically insulating layer; and a transistor connected to each of the plurality of pixel units. The method comprises the following steps: applying a bias voltage to the top electrode; receiving a charged particle beam, wherein the charged particle beam penetrates an electrically insulating layer and generates a charge signal; the charge signals are stored in the storage capacitors such that a plurality of charge signals are stored in the plurality of storage capacitors. The method also includes changing the polarity of the gate line bias voltages of the transistors of a row and integrating charge from orthogonal data lines, each of the orthogonal data lines being connected to a respective storage capacitor among a plurality of storage capacitors.
Accordingly, objects, aspects and advantages of the present invention provide a radiation imaging system having: the array of pixel cells includes an electrically insulating layer with a top surface and a bottom surface, a top electrode on the top surface of the electrically insulating layer, an array of pixel cells electrically coupled to the electrically insulating layer without an x-ray semiconductor, and an array of transistors connected to the array of pixel cells.
Other objects, aspects and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature.
Drawings
Features of the present invention will become apparent to those skilled in the art from the following description with reference to the accompanying drawings, in which:
FIG. 1 shows a schematic diagram of a conventional radiation imaging system using Direct Conversion Techniques (DCT);
FIG. 2 shows a schematic view of a radiation imaging system according to an embodiment of the invention;
FIG. 3 shows a schematic diagram of a readout circuit according to one embodiment of the invention;
FIG. 4 shows a flow diagram of a method for operating a radiation imaging system according to an embodiment of the invention;
FIG. 5 illustrates a comparison of an x-ray image obtained from a
figure 6 shows a prior art apparatus for detecting proton beam radiation in a proton beam therapy environment;
FIG. 7 is a proton beam radiation therapy system according to one embodiment;
FIG. 8 is an image of a star target obtained using a Spread Out Bragg Peak (SOBP) proton beam imaging system according to one embodiment of the present invention;
FIG. 9 is a Graphical User Interface (GUI) showing an image of a proton pencil beam obtained using a radiation imaging system of one embodiment of the present invention; and
FIG. 10 is a graph showing the intensities of five proton pencil beams with various position coordinates and beam intensity profiles measured with an imaging system according to one embodiment of the present invention.
Detailed Description
For purposes of simplicity and illustration, the present invention is described by referring primarily to exemplary embodiments thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the present invention.
Embodiments of the present invention provide a radiation imaging system and a method for operating a radiation imaging system. The details of the present disclosure will be explained in more detail with reference to the following examples. Those skilled in the art will readily recognize and understand the embodiments not included herein and omit explanation thereof.
The radiation may be at least one selected from the group consisting of X-rays, gamma rays, and ionizing radiation. Ionizing radiation may include all radiation that penetrates a material and produces light in a scintillation material (scintillation material). For example, the ionizing radiation may include alpha rays, beta rays, proton beams, charged particle beams, neutrons, and the like.
Fig. 2 is a schematic diagram illustrating a
In the
In another embodiment, the pixel cell may include a
In a detector (also referred to as a radiation imaging system 200) according to an embodiment of the present invention, as charged particles traverse the
Fig. 3 shows a schematic diagram of a
As shown in fig. 3, the pixel matrix is arranged in a plurality of rows and a plurality of columns (such as N rows by M columns). Although fig. 3 shows an arrangement of three (3) rows by three (3) columns, other numbers of rows and columns may be used. The gate lines of each row of transistors are connected to each of a plurality of external gate drivers. A data line of each column of transistors orthogonal to the gate line is connected to each of the plurality of charge integrating amplifiers. Before the radiation beam exposure, a bias voltage of a magnitude up to, but not exceeding, the breakdown voltage of the electrical insulator is applied to the
During readout of an image caused by radiation beam exposure, the gate voltage in a ROW (ROW1, ROW2, or ROW3) is changed from negative to positive, allowing the charge stored in each pixel in the ROW to flow through the
In one embodiment, the array of pixel cells is directly coupled to the electrically insulating
In one embodiment according to the invention, the
In an embodiment according to the invention, the radiation beam is a high intensity X-ray beam and the X-ray energy may range anywhere from about 5keV to about 10 MeV. The conductive channel may be formed when the concentration of the plurality of x-ray photons in the pixel is high enough to form a continuous path between the bias electrode and the pixel electrode. In particular, embodiments of the present invention are capable of producing high resolution images using high intensity x-rays having energy levels greater than 50keV (or 50keV-10MeV), which exceeds the range over which prior art devices are capable of producing high resolution images. Furthermore, embodiments of the present invention are capable of producing high resolution images using high intensity x-rays having energy levels of 100keV or greater (or 100keV-10MeV), which energy levels of 100keV or greater (or 100keV-10MeV) significantly exceed the range over which prior art devices are capable of producing high resolution images. However, any particular X-ray energy level may be applied depending on the purpose for which
According to one embodiment, the range of radiation applied to the
In one embodiment, the
In one embodiment, an electrically insulating
In one embodiment, the
The scintillation light of conventional scintillation imaging detectors needs to travel long distances, typically hundreds of microns, before converting the light into electrical charge by means of photodiodes. Along this long optical path, the scintillation light of conventional scintillation imaging detectors may experience scattering inside the scintillation material, resulting in a degradation of image sharpness.
On the other hand, a problem with conventional direct conversion photoconductive materials (such as amorphous selenium) is that some of the charge generated within the photoconductive layer may continue to remain as trapped charge, not only within the photoconductive layer, but also at the planar interface between the surface of the photoconductive layer and the surface of an adjacent layer. These residual charges must be completely eliminated before the next X-ray exposure. Otherwise, an erroneous image pattern associated with the previous radiation pattern may be added to the subsequent radiograph. In the
Fig. 4 shows a flow diagram of a
An embodiment of the following method will now be described with reference to the following flowchart of
In
At
In
In
In
Fig. 5 illustrates a comparison of an x-ray image obtained from a
"detection quantum efficiency" is a measure of how efficient a detection device is. The DQE of
Additionally, in proton therapy, the patient may be in a room with high background radiation (i.e., where there are significant background x-rays and gamma rays). Since DQE of X-rays and gamma rays is low but detection of charged particles is high in the case of the
Fig. 7 shows a radiation therapy system according to an embodiment. In particular, fig. 7 shows a proton beam
In operation, proton particles are accelerated by the
The
In one embodiment,
Fig. 8 is an image of a star target at the location of a
Fig. 9 is an example of a Graphical User Interface (GUI) used in an
Fig. 10 is a diagram showing the intensity profiles and positions of five proton pencil beams 10a, 10b, 10c, 10d, and 10e measured using
While specific reference has been made throughout this disclosure, representative embodiments of the invention may be used in a wide variety of applications, and the foregoing discussion is not intended to, and should not be construed as, limiting, but is provided as an illustrative discussion of various aspects of the invention.
Described and illustrated herein are embodiments of the present invention, along with some variations thereof. The terms, descriptions and figures used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the invention, which is intended to be defined by the following claims and their equivalents, in which all terms are meant in their broadest reasonable sense unless otherwise indicated.
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