Multi-source cone-beam computed tomography

Abstract

Disclosed herein is an apparatus (10), comprising: a first radiation source (12) configured to generate a first divergent radiation beam (11) toward an object (50); a second radiation source (14) configured to generate a second divergent radiation beam (13) toward the object; and an image sensor (9000). The image sensor (9000), the first radiation source (12), and the second radiation source (14) are configured to rotate around the object (50), and the relative positions between the image sensor (9000), the first radiation source (12), and the second radiation source (14) are fixed during the rotation around the object (50). A method of using the apparatus (10) is also disclosed herein.

Description

[Background technology]

[0001] Cone beam computed tomography (CBCT) is a type of computed tomography. CBCT uses a diverging beam of radiation to illuminate the object being imaged and can provide better image accuracy, shorter scan times, and lower doses than conventional CT. CBCT can be used in a variety of applications, such as implantology, orthodontics, plastic surgery, and interventional radiology. [Summary of the invention]

[0002] A device is disclosed herein, comprising: a first radiation source configured to generate a first divergent radiation beam toward an object; a second radiation source configured to generate a second divergent radiation beam toward the object; and an image sensor. The image sensor, the first radiation source, and the second radiation source are configured to rotate around the object, and during the rotation around the object, the relative positions of the image sensor, the first radiation source, and the second radiation source are fixed.

[0003] According to an embodiment, the apparatus further comprises a controller configured to activate and deactivate the first radiation source independently of the second radiation source and configured to activate and deactivate the second radiation source independently of the first radiation source.

[0004] According to an embodiment, the apparatus further comprises a shutter configured to controllably block the first divergent radiation beam from reaching the object and to controllably block the second divergent radiation beam from reaching the object.

[0005] According to an embodiment, the image sensor is configured to capture an image of a portion of the object with the first divergent radiation beam or with the second divergent radiation beam.

[0006] According to an embodiment, the image sensor comprises a collimator having a plurality of radiation transmission regions and a radiation blocking region, the radiation blocking region being configured to block radiation that would otherwise be incident on a dead region of the image sensor, and the radiation transmission region being configured to transmit at least a portion of radiation that would be incident on an active region of the image sensor.

[0007] According to an embodiment, the apparatus further comprises a face mask having a plurality of radiation transmission zones and a radiation blocking zone, wherein the radiation blocking zones are configured to block portions of the first divergent radiation beam that would otherwise be incident on a dead zone of the image sensor through the object, and the radiation transmission zone of the face mask is configured to transmit at least portions of the first divergent radiation beam that would be incident on an active zone of the image sensor.

[0008] According to an embodiment, the image sensor comprises: a plurality of radiation detectors spaced apart from each other. The image sensor is configured to capture an image of a first portion of the object using the radiation detectors and the first divergent radiation beam, and is configured to capture an image of a second portion of the object using the radiation detectors and the second divergent radiation beam. The image sensor is configured to form an image of the object by stitching the image of the first portion and the image of the second portion.

[0009] According to an embodiment, when the image sensor captures an image of a first portion of the object, the first radiation source is in a first position relative to the object, and when the image sensor captures an image of a second portion of the object, the second radiation source is in a second position relative to the object. The first position and the second position are the same.

[0010] According to an embodiment, at least some of the plurality of radiation detectors are arranged in staggered rows.

[0011] According to an embodiment, the sizes of radiation detectors in the same row are consistent. The distance between two adjacent radiation detectors in the same row is greater than the width of one radiation detector in the same row along the extension direction of the row, and less than twice that width.

[0012] According to an embodiment, at least some of the plurality of radiation detectors are rectangular in shape.

[0013] According to an embodiment, at least some of the plurality of radiation detectors are hexagonal in shape.

[0014] According to an embodiment, at least one of the plurality of radiation detectors comprises a radiation absorbing layer and an electronic layer. The radiation absorbing layer comprises an electrode. The electronic layer comprises an electronic system. The electronic system comprises: a first voltage comparator configured to compare the voltage of the electrode with a first threshold, a second voltage comparator configured to compare the voltage with a second threshold, a counter configured to record the number of particles of radiation reaching the radiation absorbing layer; and a controller. The controller is configured to start a time delay from the moment when the first voltage comparator determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold. The controller is configured to activate the second voltage comparator during the time delay. The controller is configured to increase the number recorded by the counter by one if the second voltage comparator determines that the absolute value of the voltage is equal to or exceeds the absolute value of the second threshold.

[0015] According to an embodiment, the electronic system further comprises an integrator electrically connected to the electrode.The integrator is configured to collect charge carriers from the electrode.

[0016] According to an embodiment, the controller is configured to activate the second voltage comparator at the beginning or at the end of the time delay.

[0017] According to an embodiment, the electronic system further comprises a voltmeter. The controller is configured to cause the voltmeter to measure the voltage when the time delay expires.

[0018] According to an embodiment, the controller is configured to determine the energy of the radiated particles based on the value of the voltage measured at the expiration of the time delay.

[0019] According to an embodiment, the controller is configured to connect the electrode to electrical ground.

[0020] According to an embodiment, at the expiration of the time delay, the rate of change of the voltage is substantially zero.

[0021] According to an embodiment, at the expiration of the time delay, the rate of change of the voltage is substantially non-zero.

[0022] A method is disclosed herein, comprising: placing a first radiation source at a relative position relative to an object; directing a first divergent radiation beam from the first radiation source toward the object; using an image sensor to capture an image of a first portion of the object with the first divergent radiation beam; placing a second radiation source at the relative position relative to the object; directing a second divergent radiation beam from the second radiation source toward the object; using the image sensor to capture an image of a second portion of the object with the second divergent radiation beam; forming an image of the object by stitching the image of the first portion and the image of the second portion. The image sensor, the first radiation source, and the second radiation source are configured to rotate around the object. During the rotation, the relative positions between the image sensor, the first radiation source, and the second radiation source are fixed.

[0023] According to an embodiment, when the first radiation source is not in the relative position, the first radiation source is deactivated, and when the second radiation source is not in the relative position, the second radiation source is deactivated.

[0024] According to an embodiment, when the first radiation source is not in the relative position, radiation generated by the first radiation source is blocked from reaching the object; and when the second radiation source is not in the relative position, radiation generated by the second radiation source is blocked from reaching the object.

[0025] According to an embodiment, when the first radiation source is in the relative position, a portion of the first divergent radiation beam that would otherwise pass through the object to be incident on the dead zone of the image sensor is blocked; and when the second radiation source is in the relative position, a portion of the second divergent radiation beam that would otherwise pass through the object to be incident on the dead zone of the image sensor is blocked.

[0026] According to an embodiment, the image sensor comprises a plurality of radiation detectors spaced apart from each other. Taking an image of a first portion of the object comprises: receiving, with the radiation detectors, a portion of the first divergent radiation beam passing through the object. Taking an image of a second portion of the object comprises: receiving, with the radiation detectors, a portion of a second divergent radiation beam passing through the object.

[0027] According to an embodiment, the image of the first part of the object and the image of the second part of the object have a spatial overlap.

[0028] According to an embodiment, positioning the first radiation source comprises rotating the first radiation source, the second radiation source and the image sensor around the object.

Brief Description of the Drawings

[0029] Figure 1A and Figure 1B Each schematically shows a device according to an embodiment.

[0030] Figure 2 A controller of a device according to an embodiment is schematically shown.

[0031] Figure 3A A cross-sectional view schematically illustrates a radiation detector of an image sensor of an apparatus according to an embodiment.

[0032] Figure 3B A detailed cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0033] Figure 3C An alternative detailed cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0034] Figure 4 It is schematically shown that according to an embodiment, a radiation detector may have a pixel array.

[0035] Figure 5A A top view of a package including a radiation detector and a printed circuit board (PCB) is schematically shown.

[0036] Figure 5B A cross-sectional view of an image sensor is schematically shown. Figure 5A Multiple packages are mounted on another PCB.

[0037] Fig. 6A and Figure 6B A first mask of a device according to an embodiment is schematically shown.

[0038] Figure 6C and Fig.6D A second mask of a device according to an embodiment is schematically shown.

[0039] Figure 7 A collimator of an image sensor according to an embodiment is schematically shown.

[0040] Fig. 8A It is schematically shown that according to an embodiment, an image of an object can be formed by stitching images of multiple different parts of the object.

[0041] Figure 8B It is schematically shown that according to an embodiment, an image of an object can be formed by stitching images of multiple different parts of the object.

[0042] Figure 9A-9C Schematically illustrated is an arrangement of detectors in an image sensor according to some embodiments.

[0043] Fig.10 It is schematically shown that according to an embodiment, the radiation detector is hexagonal.

[0044] Fig.11 Schematically shown is a flow chart of a method for using the device according to an embodiment.

[0045] Fig. 12A and Fig. 12B Each shows: According to an embodiment, Figure 3A , Figure 3B and Figure 3C A diagram of the components of the detector's electronic system.

[0046] Fig.13 Schematically shown are: according to an embodiment, the time variation of the current flowing through the electrode of the diode or electrical contact of the radiation absorbing layer exposed to radiation (upper curve), said current being caused by the charge carriers generated by the radiation particles incident on the radiation absorbing layer, and the time variation of the voltage of the corresponding electrode (lower curve).

[0047] Fig.14 Schematically showing: According to an embodiment, in an electronic system (which is Fig.13 ), the temporal variation of the current flowing through the electrode caused by noise (eg, dark current) and the corresponding temporal variation of the voltage of the electrode (lower curve).

[0048] Fig.15Schematically shown are: according to an embodiment, when the electronic system operates at a higher rate to detect incident radiation particles, the time variation of the current flowing through the electrode of the radiation absorbing layer exposed to the radiation (upper curve), the current caused by the charge carriers generated by the radiation particles incident on the radiation absorbing layer, and the time variation of the voltage of the corresponding electrode (lower curve).

[0049] Fig.16 Schematically showing: According to an embodiment, in an electronic system (which is Fig.15 The temporal variation of the current flowing through the electrode (upper curve) and the corresponding temporal variation of the voltage of the electrode (lower curve) caused by noise (eg, dark current) in the embodiment of the present invention are shown.

[0050] Fig.17 Schematically showing: According to an embodiment, in an electronic system (which is Fig.15 The RST shown in t e The temporal variation of the current flowing through the electrode (upper curve) caused by the charge carriers generated by the series of radiation particles incident on the radiation absorbing layer, and the corresponding temporal variation of the electrode voltage, in the previously terminated operation. [Specific implementation method]

[0051] Figure 1A and Figure 1B Each schematically shows a device 10 according to an embodiment. The device 10 includes a first radiation source 12, a second radiation source 14, and an image sensor 9000. The device 10 may include one or more additional radiation sources. The first radiation source 12 is configured to generate a first divergent radiation beam 11 toward an object 50. The second radiation source 14 is configured to generate a second divergent radiation beam radiation 13 toward the object 50. The image sensor 9000 can capture an image of a portion of the object 50 with the first divergent radiation beam 11 or the second divergent radiation beam 13. The image sensor 9000, the first radiation source 12, and the second radiation source 14 are configured to rotate around the object 50 about one or more axes, and during the rotation around the object 50, the relative positions between the image sensor 9000, the first radiation source 12, and the second radiation source 14 are fixed. For example, the image sensor 9000, the first radiation source 12, and the second radiation source 14 may be mounted on a rigid frame 15.

[0052] According to an embodiment, the first radiation source 12 and the second radiation source 14 may each be a radiation source, or a gamma ray source.The object 50 may be a person or a container.

[0053] Figure 1A and Figure 1B It is shown that: the first radiation source 12, the second radiation source 14, and the image sensor 9000 collectively rotate around the object 50 (the rotation is to such an extent that Figure 1A The first radiation source 12 and Figure 1B The positions of the first radiation source 12, the second radiation source 14, and the image sensor 9000 relative to the object 50 before and after the second radiation source 14 is at the same position relative to the object 50. Figure 1A and Figure 1B In the figure, the image sensor 9000 is at different positions relative to the object 50. Figure 1A In the embodiment of the present invention, the first radiation source 12 is activated and the first divergent radiation beam 11 is directed towards the object 50. Figure 1A The image sensor 9000 in can capture an image of a portion of the object 50 using the first divergent radiation beam 11. Figure 1B The second radiation source 14 is activated and the second divergent radiation beam 13 is directed toward the object 50. Figure 1B The image sensor 9000 may capture an image of another portion of the object 50 using the second divergent radiation beam 13 .

[0054] According to an embodiment, the device 10 may include a shutter 22 as shown in FIG. 1. The shutter 22 may be configured to controllably block the first divergent radiation beam 11 from reaching the object 50, and controllably block the second divergent radiation beam 13 from reaching the object 50. The shutter 22 may have one or more openings. The shutter 22 may have a fixed position relative to the first radiation source 12, the second radiation source 14, and the image sensor 9000. That is, the shutter 22 may rotate relative to the object 50 with the first radiation source 12, the second radiation source 14, and the image sensor 9000.

[0055] like Figure 2 Schematically, according to an embodiment, the device 10 may include a controller 20. The controller 20 is configured to activate and deactivate the first radiation source 12 in a manner independent of the second radiation source 14, and is configured to activate and deactivate the second radiation source 14 in a manner independent of the first radiation source 12. Here, activating the radiation source may include causing it to generate radiation; deactivating the radiation source may include causing it not to generate radiation. The controller 20 may be electrically connected to the first radiation source 12 and the second radiation source 14. In an example, the controller 20 activates and deactivates the first radiation source 12 and the second radiation source 14 by respectively starting and stopping the supply of power to them.

[0056] The image sensor 9000 may have a plurality of radiation detectors 100. The radiation detectors 100 may be spaced apart from each other. Figure 3AA cross-sectional view of a radiation detector 100 of an image sensor 9000 according to an embodiment is schematically shown. The radiation detector 100 may include a radiation absorption layer 110 and an electronic layer 120 (e.g., an ASIC) for processing or analyzing an electrical signal generated in the radiation absorption layer 110 by incident radiation. In an embodiment, the radiation detector 100 does not include a scintillator. The radiation absorption layer 110 may include a semiconductor material, such as silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof. The semiconductor may have a high mass attenuation coefficient for radiation generated by the radiation source of the device 10.

[0057] As in Figure 3B As shown in the detailed cross-sectional view of the detector 100 in , according to an embodiment, the radiation absorbing layer 110 may include one or more diodes (e.g., pin or pn) formed by one or more discrete regions 114 of a first doping region 111, a second doping region 113. The second doping region 113 may be separated from the first doping region 111 by an intrinsic region 112 (optional). The discrete regions 114 are separated from each other by the first doping region 111 or the intrinsic region 112. The first doping region 111 and the second doping region 113 have opposite types of doping (e.g., region 111 is p-type and region 113 is n-type, or region 111 is n-type and region 113 is p-type). Figure 3B In the example of , each of the discrete regions 114 of the second doped region 113 forms a diode together with the first doped region 111 and the intrinsic region 112 (optional). Figure 3B In the example in FIG. 1 , the radiation absorbing layer 110 has a plurality of diodes having the first doping region 111 as a common electrode. The first doping region 111 may also have discrete portions.

[0058] When a radiation particle strikes the radiation absorbing layer 110 (which includes a diode), the radiation particle may be absorbed and generate one or more carriers through multiple mechanisms. One radiation particle may generate 10 to 100,000 carriers. The carriers may drift toward an electrode of one of the diodes under an electric field. The field may be an external electric field. The electrical contact 119B may include discrete portions, each of which is in electrical contact with the discrete region 114. In an embodiment, the carriers may drift in multiple directions so that the carriers generated by a single radiation particle are not substantially shared by two different discrete regions 114 ("substantially not shared" here means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these carriers flow to one of the discrete regions 114 that is different from the remaining carriers). The carriers generated by the radiation particles incident around the footprint of one of these discrete regions 114 are not substantially shared with another of these discrete regions 114. A pixel 150 associated with a discrete region 114 may be a region surrounding the discrete region 114 in which substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the charge carriers generated by incident radiation particles flow toward the discrete region 114. That is, less than 2%, less than 1%, less than 0.1%, or less than 0.01% of these charge carriers flow outside the pixel.

[0059] As in Figure 3C As shown in an alternative detailed cross-sectional view of radiation detector 100 in FIG. 1 , according to an embodiment, radiation absorbing layer 110 may include a resistor having a semiconductor material (e.g., silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof), but not a diode. The semiconductor may have a high mass attenuation coefficient for radiation generated by a radiation source in device 10.

[0060] When a radiation particle strikes the radiation absorbing layer 110 (which includes a resistor but not a diode), it may be absorbed and generate one or more carriers through multiple mechanisms. A radiation particle may generate 10 to 100,000 carriers. The carriers may drift toward the electrical contacts 119A and 119B under an electric field. The field may be an external electric field. The electrical contact 119B includes discrete portions. In an embodiment, the carriers may drift in multiple directions so that the carriers generated by a single radiation particle are not substantially shared by two different discrete portions of the electrical contact 119B ("substantially not shared" here means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these carriers flow to one of the discrete regions different from the remaining carriers). The carriers generated by the radiation particles incident around the footprint of one of these discrete portions of the electrical contact 119B are not substantially shared with another of these discrete portions of the electrical contact 119B. A pixel 150 associated with a discrete portion of electrical contact 119B may be a region surrounding the discrete portion in which substantially all (greater than 98%, greater than 99.5%, greater than 99.9%, or greater than 99.99%) of the charge carriers generated by incident radiation particles flow toward the discrete portion of electrical contact 119B. That is, less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these charge carriers flow outside of a pixel associated with a discrete portion of electrical contact 119B.

[0061] The electronic layer 120 may include an electronic system 121 suitable for processing or interpreting signals generated by radiation particles incident on the radiation absorption layer 110. The electronic system 121 may include analog circuits, such as filter networks, amplifiers, integrators and comparators, or digital circuits, such as microprocessors and memories. The electronic system 121 may include components shared by pixels or components dedicated to a single pixel. For example, the electronic system 121 may include an amplifier dedicated to each pixel and a microprocessor shared between all pixels. The electronic system 121 may be electrically connected to the pixel through a through hole 131. The space between the through holes may be filled with a filling material 130, which may increase the mechanical stability of the connection of the electronic layer 120 to the radiation absorption layer 110. Other bonding techniques that connect the electronic system 121 to the pixel without using a through hole are possible.

[0062] Figure 4The detector 100 is schematically shown to have an array of pixels 150. The array may be a rectangular array, a honeycomb array, a hexagonal array, or any other suitable array. Each pixel 150 may be configured to detect radiation particles incident thereon, measure the energy of the radiation particles, or both. For example, each pixel 150 may be configured to count the number of radiation particles incident thereon whose energy falls in multiple bins over a period of time. All pixels 150 may be configured to count the number of radiation particles incident thereon in multiple energy bins over the same period of time. Each pixel 150 may have its own analog-to-digital converter (ADC) configured to digitize an analog signal representing the energy of the incident radiation particles into a digital signal. The ADC may have a resolution of 10 bits or more. Each pixel 150 may be configured to measure its dark current, for example before or concurrently with each radiation particle incident thereon. Each pixel 150 may be configured to subtract the contribution of the dark current from the energy of the radiation particles incident thereon. The pixels 150 may be configured to operate in parallel. For example, while one pixel 150 is measuring an incoming radiation particle, another pixel 150 may be waiting for a radiation particle to arrive. The pixels 150 may, but need not be, independently addressable.

[0063] The radiation detectors of image sensor 9000 may be arranged in any suitable manner. Figure 5A and Figure 5B An example of an arrangement of radiation detectors in an image sensor 9000 is shown. One or more radiation detectors 100 may be mounted on a printed circuit board (PCB) 400. The term "PCB" used herein is not limited to a specific material. For example, the PCB may include a semiconductor. The radiation detector 100 may be mounted on the PCB 400. For clarity, the wires between the radiation detector 100 and the PCB 400 are not shown. The PCB 400 and the radiation detector 100 mounted thereon may be referred to as a package 200. The PCB 400 may have an area not covered by the radiation detector 100 (e.g., an area for accommodating the bonding wire 410). Each of the radiation detectors 100 may have an effective area 190, which is where the pixel 150 is located. Each of the radiation detectors 100 may have a peripheral area 195 near the edge. The peripheral area 195 has no pixels, and radiation particles incident on the peripheral area 195 are not detected.

[0064] Figure 5BIt is schematically shown that the image sensor 9000 may have a PCB450 system on which a plurality of packages 200 are mounted. The image sensor 9000 may include such a system of one or more PCB450. The electrical connection between the PCB400 in the package 200 and the system PCB450 may be formed by a wire bond 410. In order to accommodate the wire bond 410 on the PCB400, the PCB400 has an area 405 that is not covered by the radiation detector 100. In order to accommodate the wire bond 410 on the system PCB450, there is a gap between the packages 200. The active area 190 of the radiation detector 100 in the image sensor 9000 is collectively referred to as the active area of ​​the image sensor 9000. Other areas of the image sensor 9000, such as the peripheral area 195, the area 405 or the gap between the packages 200, on which the radiation incident cannot be detected by the image sensor 9000, are collectively referred to as the dead area of ​​the image sensor 9000.

[0065] Fig. 6A and Figure 6B It is schematically shown that the device 10 may have a first mask 26. According to an embodiment, the first mask 26 may have a plurality of radiation transmission areas 2602 and a radiation blocking area 2604. Figure 6B It is schematically shown that according to an embodiment, the radiation blocking area 2604 is configured to block a portion of the first divergent radiation beam 11 (otherwise, it will pass through the object 50 and be incident on the dead area 9004 of the image sensor 9000), and the radiation transmission area 2602 is configured to transmit at least a portion of the first divergent radiation beam 11 (which will be incident on the effective area 9002 of the image sensor 9000).

[0066] According to an embodiment, the first mask 26 may be made of a material such as lead. The radiation transmission area 2602 of the first mask 26 may be a plurality of holes. The radiation blocking area of ​​the first mask 26 may be an area other than the holes.

[0067] According to an embodiment, the first mask 26 may be located between the first radiation source 12 and the object 50. The first mask 26 may reduce the radiation dose received by the object 50.

[0068] Figure 6C and Fig.6D It is schematically shown that the device 10 may have a second mask 28. According to an embodiment, the second mask 28 may have a plurality of radiation transmission areas 2802 and a radiation blocking area 2804. Fig.6DIt is schematically shown that, according to an embodiment, the radiation blocking area 2804 is configured to block a portion of the second divergent radiation beam 13 that would otherwise pass through the object 50 and be incident on the dead area 9004 of the image sensor 9000. And the radiation transmission area 2802 is configured to transmit at least a portion of the second divergent radiation beam 13 that would be incident on the active area 9002 of the image sensor 9000.

[0069] According to an embodiment, the second mask 28 may be made of a material such as lead. The radiation transmission area 2802 of the second mask 28 may be a plurality of holes. The radiation blocking area of ​​the second mask 28 may be an area other than the holes.

[0070] According to an embodiment, the second mask 28 may be located between the second radiation source 14 and the object 50. The second mask 28 may reduce the radiation dose that the object 50 receives.

[0071] Figure 7 The image sensor 9000 is schematically shown to include a collimator 2000. According to an embodiment, the collimator 2000 includes a plurality of radiation transmission regions 2002 and a radiation blocking region 2004. The radiation blocking region 2004 substantially blocks radiation that would otherwise be incident on the dead region 9004 of the image sensor 9000, and the radiation transmission region 2002 allows at least part of the radiation incident on the active region 9002 of the image sensor 9000 to pass. The radiation transmission region 2002 may be a hole passing through the collimator 2000, and the remaining portion of the collimator 2000 may function as the radiation blocking region 2004. The collimator may be placed close to the image sensor 9000. The radiation transmission region 2002 may have a slightly different size or position than the active region 9002 of the image sensor 9000.

[0072] like Fig. 8A As shown, when the positions of the image sensor 9000, the first radiation source 12 and the second radiation source 14 are at their respective positions relative to the object 50 (eg Figure 1A ), the image sensor 9000 captures an image 51A of a portion of the object 50 using the first divergent beam 11. The image sensor 9000, the first radiation source 12, and the second radiation source 14 are collectively rotated relative to the object 50 to their respective positions relative to the object 50 (as shown in FIG. Figure 1B ), where the image sensor 9000 uses the second divergent beam 13 to capture an image 51B of another portion of the object 50. The image sensor 9000 forms an image of the object 50 by stitching the image 51A and the image 51B. The images 51A and 51B may partially overlap to facilitate stitching.

[0073] According to an embodiment, the apparatus 10 may comprise more than two radiation sources. Figure 8BThe example of the device 10 having three radiation sources is schematically shown. The image sensor 9000 uses divergent radiation beams from the three radiation sources to capture images 52A, 52B and 52C of three different parts of the object 50 at three different positions A, B and C relative to the object 50, respectively. The image sensor 9000 forms an image of the object 50 by stitching the images 52A, 52B and 52C. The images 52A, 52B and 52C may partially overlap to facilitate stitching. The radiation sources may be staggered, i.e. not arranged in a straight line.

[0074] The radiation detector 100 may be arranged in the image sensor 9000 in various ways. Fig. 9A An arrangement is schematically shown, where the detectors 100 are arranged in staggered rows according to an embodiment. For example, detectors 100A and 100B are in the same row, aligned in the Y direction, and are of the same size; detectors 100C and 100D are in the same row, aligned in the Y direction, and are of the same size. Detectors 100A and 100B are staggered in the X direction relative to detectors 100C and 100D. According to an embodiment, the distance X2 between two adjacent radiation detectors 100A and 100B is greater than the width X1 of one radiation detector in the same row (i.e., the dimension is the X direction, which is the extension direction of the row) and is less than twice the width X1. Detectors 100A and 100E are in the same column, aligned in the X direction, and are of the same size; the distance Y2 between two adjacent radiation detectors 100A and 100E in the same column is less than the width Y1 of one radiation detector in the same column (i.e., the dimension is the Y direction).

[0075] Fig. 9B Another arrangement according to an embodiment is schematically shown, where the detectors 100 are arranged in a rectangular grid. For example, the detectors 100 may include detectors 100A, 100B, 100E and 100F (as shown in FIG. Fig. 9A ) without Fig. 9A Detector 100C, 100D, 100G or 100H.

[0076] Other arrangements are possible. For example, Fig. 9C In the embodiment, the radiation detector 100 may span the entire width of the image sensor 9000 in the X direction, and the distance Y2 between two adjacent detectors 100 is less than the width Y1 of one radiation detector.

[0077] According to an embodiment, the radiation sources (eg, 12 and 14) and image sensor 9000 may collectively rotate around the object about multiple axes.

[0078] The radiation detector 100 in the image sensor 9000 may have any suitable size and shape. Figure 9A-9C ), at least some of the radiation detectors are rectangular in shape. According to an embodiment, Fig.10 As shown, at least some of the radiation detectors are hexagonal. In such radiation detectors, the radiation detectors and the corresponding aligned collimators may have the same shape.

[0079] Fig.11 A flow chart of a method according to an embodiment is schematically shown. In step 1210, a first radiation source 12 is positioned at a relative position with respect to an object 50. In step 1220, a first divergent radiation beam 11 is directed to the object 50, and in step 1230, the image sensor 9000 uses the first divergent radiation beam to capture an image of a first portion of the object 50. In step 1240, a second radiation source 14 is positioned at the same relative position with respect to the object 50. In step 1250, a second divergent radiation beam 13 is directed to the object 50. In step 1260, the image sensor 9000 uses the second divergent radiation beam to capture an image of a second portion of the object 50. In step 1270, an image of the object 50 is formed by stitching the image of the first portion and the image of the second portion. Since the relative positions between the image sensor 9000, the first radiation source 12 and the second radiation source 14 are fixed, positioning the first radiation source 12 in step 1210 also causes the positioning of the second radiation source 14 and the image sensor 9000, and positioning the second radiation source 14 in step 1240 also causes the positioning of the first radiation source 12 and the image sensor 9000.

[0080] When first radiation source 12 is not in the relative position, radiation generated by first radiation source 12 may be blocked from reaching object 50, and when second radiation source 14 is not in the relative position, radiation generated by second radiation source 14 may be blocked from reaching object 50. For example, shutter 22 may be used to block radiation.

[0081] The first radiation source 12 may remain deactivated when not in the relative position, and the second radiation source 14 may be deactivated when not in the relative position.

[0082] Fig. 12A and Fig. 12B Each of the diagrams shows a component of the electronic system 121 according to an embodiment. The electronic system 121 may include a first voltage comparator 301 , a second voltage comparator 302 , a counter 320 , a switch 305 , a voltmeter 306 , and a controller 310 .

[0083] The first voltage comparator 301 is configured to compare the voltage of the electrode of the diode 300 with a first threshold value. The diode can be a diode formed by the first doped region 111, one of the discrete regions 114 of the second doped region 113 and the intrinsic region 112 (optional). Alternatively, the first voltage comparator 301 is configured to compare the voltage of the electrical contact (e.g., the discrete region of the electrical contact 119B) with a first threshold value. The first voltage comparator 301 can be configured to directly monitor the voltage, or to calculate the voltage by integrating the current flowing through the diode or the electrical contact over a period of time. The first voltage comparator 301 can be controllably activated or deactivated by the controller 310. The first voltage comparator 301 can be a continuous comparator. That is, the first voltage comparator 301 can be configured to be continuously activated and continuously monitor the voltage. The first voltage comparator 301 configured as a continuous comparator reduces the chance that the system 121 misses the signal generated by the incident radiation particles. The first voltage comparator 301 configured as a continuous comparator is particularly suitable when the incident radiation intensity is relatively high. The first voltage comparator 301 can be a clocked comparator, which has the benefit of lower power consumption. The first voltage comparator 301 configured as a clocked comparator can cause the system 121 to miss signals generated by some incident radiation particles. When the incident radiation intensity is low, the chance of missing the incident radiation particles is relatively low because the interval between two consecutive particles is relatively long. Therefore, the first voltage comparator 301 configured as a clocked comparator is particularly suitable when the incident radiation intensity is relatively low. The first threshold value can be 5-10%, 10%-20%, 20-30%, 30-40% or 40-50% of the maximum voltage that an incident radiation particle can generate in a diode or resistor. The maximum voltage may depend on the energy of the incident radiation particle (i.e., the wavelength of the incident radiation), the material of the radiation absorbing layer 110, and other factors. For example, the first threshold value can be 50mV, 100mV, 150mV or 200mV.

[0084] The second voltage comparator 302 is configured to compare the voltage with a second threshold. The second voltage comparator 302 may be configured to monitor the voltage directly, or to calculate the voltage by integrating the current flowing through a diode or an electrical contact over a period of time. The second voltage comparator 302 may be a continuous comparator. The second voltage comparator 302 may be controllably activated or deactivated by the controller 310. When the second voltage comparator 302 is deactivated, the power consumption of the second voltage comparator 302 may be less than 1%, less than 5%, less than 10%, or less than 20% of the power consumption when the second voltage comparator 302 is activated. The absolute value of the second threshold is greater than the absolute value of the first threshold. As used herein, the term "absolute value" or "modulus" |x| of a real number x is a non-negative value of x regardless of its sign. That is, The second threshold value can be 200%-300% of the first threshold value. The second threshold value can be at least 50% of the maximum voltage that an incident radiation particle can generate in a diode or a resistor. For example, the second threshold value can be 100mV, 150mV, 200mV, 250mV or 300mV. The second voltage comparator 302 and the first voltage comparator 301 can be the same component. That is, the system 121 can have a voltage comparator that can compare the voltage with two different threshold values ​​at different times.

[0085] The first voltage comparator 301 or the second voltage comparator 302 may include one or more operational amplifiers or any other suitable circuits. The first voltage comparator 301 or the second voltage comparator 302 may have a high speed to allow the system 121 to operate under high incident radiation flux. However, having a high speed usually comes at the expense of power consumption.

[0086] The counter 320 is configured to record the number of radiation particles reaching the diode or resistor. The counter 320 can be a software component (eg, a number stored in a computer memory) or a hardware component (eg, 4017 IC and 7490 IC).

[0087] The controller 310 may be a hardware component such as a microcontroller and a microprocessor. The controller 310 is configured to start the time delay from the time when the first voltage comparator 301 determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold (e.g., the absolute value of the voltage increases from below the absolute threshold of the first threshold to a value equal to or exceeding the absolute value of the first threshold). The absolute value is used here because the voltage can be negative or positive, depending on whether the voltage of the cathode or anode of the diode is used or which electrical contact is used. The controller 310 may be configured to keep the second voltage comparator 302, the counter 320, and any other circuits not required for the operation of the first voltage comparator 301 disabled before the time when the first voltage comparator 301 determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold. The time delay may terminate before or after the voltage becomes stable (i.e., the rate of change of the voltage is approximately zero). The phrase "the rate of change of the voltage is approximately zero" means that the time variation of the voltage is less than 0.1% / ns. The phrase "the rate of change of the voltage is approximately non-zero" means that the time variation of the voltage is at least 0.1% / ns.

[0088] The controller 310 may be configured to activate the second voltage comparator during the time delay (including the start and the end). In an embodiment, the controller 310 is configured to activate the second voltage comparator at the start of the time delay. The term "activate" means to cause a component to enter an operating state (e.g., by sending a signal such as a voltage pulse or a logic level, by providing power, etc.). The term "deactivate" means to cause a component to enter a non-operating state (e.g., by sending a signal such as a voltage pulse or a logic level, by cutting off power, etc.). The operating state may have a higher power consumption than the non-operating state (e.g., 10 times higher, 100 times higher, 1000 times higher). The controller 310 itself may be deactivated until the output of the first voltage comparator 301 activates the controller 310 when the absolute value of the voltage equals or exceeds the absolute value of the first threshold.

[0089] If during the time delay the second voltage comparator 302 determines that the absolute value of the voltage equals or exceeds the absolute value of the second threshold, the controller 310 may be configured to cause the number recorded by the counter 320 to be incremented by one.

[0090] The controller 310 may be configured to cause the voltmeter 306 to measure the voltage when the time delay expires. The controller 310 may be configured to connect the electrode to electrical ground so as to reset the voltage and discharge any carriers accumulated on the electrode. In an embodiment, the electrode is connected to electrical ground after the time delay expires. In an embodiment, the electrode is connected to electrical ground for a limited reset period. The controller 310 may connect the electrode to electrical ground by controlling the switch 305. The switch may be a transistor, such as a field effect transistor (FET).

[0091] In an embodiment, system 121 has no analog filter networks (eg, RC networks). In an embodiment, system 121 has no analog circuits.

[0092] The voltmeter 306 may feed the voltage it measures to the controller 310 as an analog or digital signal.

[0093] The system 121 may include an integrator 309 electrically connected to an electrode or electrical contact of the diode 300, wherein the integrator is configured to collect carriers from the electrode. The integrator may include a capacitor in the feedback path of the amplifier. An amplifier so configured is called a capacitive transimpedance amplifier (CTIA). The CTIA has a high dynamic range by preventing the amplifier from saturating and improves the signal-to-noise ratio by limiting the bandwidth in the signal path. The carriers from the electrode are collected for a period of time ("integration period") (e.g., such as during Fig.13 , accumulated on the capacitor during t0 to t1 or t1-t2. After the integration period ends, the capacitor voltage is sampled and then reset by the reset switch. The integrator may include a capacitor directly connected to the electrode.

[0094] Fig.13 Schematically illustrates the time variation of the current flowing through the electrode caused by the carriers generated by the radiation particles incident on the diode or resistor (upper curve) and the corresponding time variation of the voltage of the electrode (lower curve). The voltage can be the integration of the current with respect to time. At time t0, the radiation particles hit the diode or resistor, the carriers begin to be generated in the diode or resistor, the current begins to flow through the electrodes of the diode or resistor, and the absolute value of the voltage of the electrode or electrical contact begins to increase. At time t1, the first voltage comparator 301 determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold value V1, and the controller 310 starts the time delay TD1 and the controller 310 can deactivate the first voltage comparator 301 at the beginning of TD1. If the controller 310 is deactivated before t1, the controller 310 is activated at t1. During TD1, the controller 310 activates the second voltage comparator 302. As used herein, the term "during" the time delay means the beginning and end (i.e., end) and any time in between. For example, the controller 310 can activate the second voltage comparator 302 at the end of TD1. If, during TD1, the second voltage comparator 302 determines that the absolute value of the voltage at time t2 equals or exceeds the absolute value of the second threshold, the controller 310 causes the number recorded by the counter 320 to increase by one. e , all carriers generated by the radiation particles drift out of the radiation absorption layer 110. At time t s , time delay TD1 is terminated. Fig.13 In the example, time t s At time t e That is, TD1 ends after all carriers generated by the radiation particles drift out of the radiation absorption layer 110. The voltage change rate is thus s The controller 310 may be configured to disable the second voltage comparator 302 at the end of TD1 or at t2 or any time in between.

[0095] The controller 310 may be configured to cause the voltmeter 306 to measure the voltage when the time delay TD1 expires. In an embodiment, the controller 310 causes the voltmeter 306 to measure the voltage after the rate of change of the voltage becomes substantially zero after the time delay TD1 expires. The voltage at this moment is proportional to the number of carriers generated by the radiation particle, which is related to the energy of the radiation particle. The controller 310 may be configured to determine the energy of the radiation particle based on the voltage measured by the voltmeter 306. One way to determine the energy is by binning the voltage. The counter 320 may have a sub-counter for each bin. When the controller 310 determines that the energy of the radiation particle falls in the bin, the controller 310 may cause the number recorded in the sub-counter for the bin to increase by one. Therefore, the system 121 may be able to detect the radiation image and may be able to distinguish the radiation particle energy of each radiation particle.

[0096] After TD1 ends, the controller 310 connects the electrode to electrical ground during a reset period RST to allow the carriers accumulated on the electrode to flow to the ground and reset the voltage. After RST, the system 121 is ready to detect another incident radiation particle. The system 121 Fig.13 The rate of incident radiation particles that can be handled in the example of is implicitly limited to 1 / (TD1+RST). If the first voltage comparator 301 is disabled, the controller 310 can activate it at any time before RST terminates. If the controller 310 is disabled, it can be activated before RST terminates.

[0097] Fig.14 Schematically showing the use of Fig.13 1 , FIG1 , a time variation of current flowing through an electrode (upper curve) and a corresponding time variation of voltage at the electrode (lower curve) caused by noise (e.g., dark current, background radiation, scattered radiation, fluorescent radiation, shared charge from adjacent pixels) in a system 121 operating in the manner shown in FIG1 . At time t0, the noise begins. If the noise is not large enough to cause the absolute value of the voltage to exceed the absolute value of V1, the controller 310 does not activate the second voltage comparator 302. If at time t1 the noise is large enough to cause the absolute value of the voltage to exceed the absolute value of V1 (determined by the first voltage comparator 301), the controller 310 starts a time delay TD1 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD1. During TD1 (e.g., at the end of TD1), the controller 310 activates the second voltage comparator 302. During TD1, it is unlikely that the noise is large enough to cause the absolute value of the voltage to exceed the absolute value of V2. Therefore, the controller 310 does not cause the number recorded by the counter 320 to increase. At time t e , the noise ends. At time t s , time delay TD1 terminates. The controller 310 may be configured to disable the second voltage comparator 302 when TD1 terminates. If the absolute value of the voltage does not exceed the absolute value of V2 during TD1, the controller 310 may be configured not to cause the voltmeter 306 to measure the voltage. After TD1 terminates, the controller 310 connects the electrode to electrical ground during the reset period RST to allow carriers accumulated on the electrode due to noise to flow to the ground and reset the voltage. Therefore, the system 121 can be very effective in noise suppression.

[0098] Fig.15Schematically illustrates the time variation of the current flowing through the electrode caused by the carriers generated by the radiation particles incident on the diode or resistor when the system 121 is operated at a rate higher than 1 / (TD1+RST) to detect the incident radiation particles (upper curve) and the corresponding time variation of the voltage of the electrode (lower curve). The voltage can be the integration of the current with respect to time. At time t0, the radiation particle hits the diode or resistor, the carriers begin to be generated in the diode or resistor, the current begins to flow through the electrode of the diode or the electrical contact of the resistor, and the absolute value of the voltage of the electrode or electrical contact begins to increase. At time t1, the first voltage comparator 301 determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold value V1, and the controller 310 activates the time delay TD2 that is shorter than the time delay TD1, and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD2. If the controller 310 is deactivated before t1, the controller 310 is activated at t1. During TD2 (for example, at the end of TD2), the controller 310 activates the second voltage comparator 302. If, during TD2, the second voltage comparator 302 determines that the absolute value of the voltage at time t2 is equal to or exceeds the absolute value of the second threshold, the controller 310 causes the number recorded by the counter 320 to increase by one. e , all carriers generated by the radiation particles drift out of the radiation absorption layer 110. At time t h , time delay TD2 is terminated. Fig.15 In the example, time t h At time t e That is, TD2 ends before all carriers generated by the radiation particles drift out of the radiation absorption layer 110. The voltage change rate is thus h The controller 310 may be configured to disable the second voltage comparator 302 at the end of TD2 or at t2 or any time therebetween.

[0099] The controller 310 may be configured to infer the voltage at t from the voltage as a function of time during TD2. e voltage and uses the inferred voltage to determine the energy of the radiated particle.

[0100] After TD2 ends, the controller 310 connects the electrode to electrical ground during a reset period RST to allow carriers accumulated on the electrode to flow to the ground and reset the voltage. e When RST is at t e When the RST is terminated, the rate of change of the voltage after RST may be substantially non-zero because all carriers generated by the radiation particles have not drifted out of the radiation absorbing layer 110. The rate of change of the voltage at t e After that, it becomes almost zero and the voltage at t e After stabilizing to the residual voltage VR. In the embodiment, RST ise or e After that, the voltage change rate after RST can be calculated because all the carriers generated by the radiation particles are e Drifts out of the radiation absorbing layer 110 and is substantially zero. After the RST, the system 121 is ready to detect another incident radiation particle. If the first voltage comparator 301 is disabled, the controller 310 can activate it at any time before the RST is terminated. If the controller 310 is disabled, it can be activated before the RST is terminated.

[0101] Fig.16 Schematically showing the use of Fig.15 1 . The time variation of the current flowing through the electrode (upper curve) and the corresponding time variation of the voltage of the electrode (lower curve) caused by noise (e.g., dark current, background radiation, scattered radiation, fluorescent radiation, shared charge from adjacent pixels) in the system 121 operating in the manner shown in FIG. 1 . At time t0, the noise begins. If the noise is not large enough to cause the absolute value of the voltage to exceed the absolute value of V1, the controller 310 does not activate the second voltage comparator 302. If at time t1 the noise is large enough to cause the absolute value of the voltage to exceed the absolute value of V1 (determined by the first voltage comparator 301), the controller 310 starts the time delay TD2 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD2. During TD2 (e.g., at the end of TD2), the controller 310 activates the second voltage comparator 302. It is unlikely that the noise is large enough to cause the absolute value of the voltage to exceed the absolute value of V2 during TD2. Therefore, the controller 310 does not cause the number recorded by the counter 320 to increase. At time t e , the noise ends. At time t h , the time delay TD2 is terminated. The controller 310 can be configured to disable the second voltage comparator 302 when TD2 is terminated. After TD2 is terminated, the controller 310 connects the electrode to the electrical ground during the reset period RST to allow carriers accumulated on the electrode due to noise to flow to the ground and reset the voltage. Therefore, the system 121 can be very effective in noise suppression.

[0102] Fig.17 Schematically showing the use of Fig.15 The method shown in (where RST is at t e The time variation of the current flowing through the electrode (upper curve) and the corresponding time variation of the electrode voltage (lower curve) caused by carriers generated by a series of radiation particles incident on the diode or resistor in a system 121 operating before (termination before) . The voltage curve caused by the carriers generated by each incident radiation particle is compensated by the residual voltage before the particle. The absolute value of the residual voltage increases successively with each incident particle. When the absolute value of the residual voltage exceeds V1 (see Fig.17), the controller starts the time delay TD2 and the controller 310 may disable the first voltage comparator 301 at the beginning of TD2. If no other radiation particles are incident on the diode or resistor during TD2, the controller connects the electrode to electrical ground during the reset period RST at the end of TD2, thereby resetting the residual voltage. The residual voltage thus does not cause the number recorded by the counter 320 to increase.

[0103] While various aspects and embodiments are disclosed herein, other aspects and embodiments will become apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

1. A computer tomography device, comprising: a first radiation source configured to generate a first divergent radiation beam directed toward the object; a second radiation source configured to generate a second divergent radiation beam directed toward the object; an image sensor including a plurality of radiation detectors spaced apart from one another; wherein the image sensor, the first radiation source, and the second radiation source are configured to rotate around the object, and the relative positions of the image sensor, the first radiation source, and the second radiation source are fixed during the rotation around the object, wherein the image sensor is configured to capture an image of a first portion of an object using the radiation detector and the first divergent radiation beam, and is configured to capture an image of a second portion of the object using the radiation detector and the second divergent radiation beam, the first portion and the second portion being different; wherein the image sensor is configured to form an image of the object by stitching the image of the first portion and the image of the second portion, wherein the first radiation source is in a first position relative to the object when the image sensor captures an image of the first portion of the object, and the second radiation source is in a second position relative to the object when the image sensor captures an image of the second portion of the object; Wherein the first position and the second position are the same.

2. The computed tomography apparatus of claim 1 , further comprising a controller configured to activate and deactivate the first radiation source independently of the second radiation source, and configured to activate and deactivate the second radiation source independently of the first radiation source.

3. The computer tomography apparatus of claim 1, further comprising a shutter configured to controllably block the first divergent radiation beam from reaching the object and controllably block the second divergent radiation beam from reaching the object.

4. The computer tomography apparatus of claim 1, wherein the image sensor is configured to capture an image of a portion of the object using the first divergent radiation beam or using the second divergent radiation beam.

5. The computer tomography apparatus of claim 1, wherein the image sensor comprises a collimator having a plurality of radiation transmission regions and a radiation blocking region; wherein the radiation blocking region is configured to block radiation that would otherwise be incident on a dead area of ​​the image sensor, and the radiation transmitting region is configured to transmit at least a portion of the radiation that would otherwise be incident on an active area of ​​the image sensor, 6. The computer tomography apparatus of claim 1, further comprising a mask having a plurality of radiation transmission zones and a radiation blocking zone; The radiation blocking area is configured to block a portion of the first divergent radiation beam that would otherwise pass through the object and be incident on a dead zone of the image sensor, and the radiation transmission area is configured to transmit at least a portion of the first divergent radiation beam that would be incident on an effective area of ​​the image sensor.

7. The computer tomography apparatus of claim 1, wherein at least some of the plurality of radiation detectors are arranged in staggered rows.

8. The computed tomography apparatus of claim 1 , wherein the sizes of radiation detectors in the same row are consistent; wherein the distance between two adjacent radiation detectors in the same row is greater than the width of a radiation detector in the same row along the row extension direction, and less than twice that width.

9. The computer tomography apparatus of claim 1, wherein at least some of the plurality of radiation detectors are rectangular in shape.

10. The computer tomography apparatus of claim 1, wherein at least some of the plurality of radiation detectors are hexagonal in shape.

11. The computer tomography apparatus of claim 1, wherein at least one of the plurality of radiation detectors comprises a radiation absorbing layer and an electronic layer; wherein the radiation absorbing layer comprises an electrode; wherein the electronic layer comprises an electronic system; The electronic system comprises: a first voltage comparator configured to compare the voltage of the electrode with a first threshold, a second voltage comparator configured to compare the voltage to a second threshold, a counter configured to record the number of radiation particles reaching the radiation absorbing layer, and Controller; wherein the controller is configured to start the time delay from the moment when the first voltage comparator determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold; wherein the controller is configured to activate the second voltage comparator during the time delay; Wherein the controller is configured to cause the number recorded by the counter to be incremented by one if the second voltage comparator determines that the absolute value of the voltage is equal to or exceeds the absolute value of a second threshold.

12. The computed tomography apparatus of claim 11, wherein the electronic system further comprises an integrator electrically connected to the electrode, wherein the integrator is configured to collect charge carriers from the electrode. 13 . The computer tomography apparatus of claim 11 , wherein the controller is configured to activate the second voltage comparator at the beginning or the end of the time delay.

14. The computerized tomography apparatus of claim 11, wherein the electronic system further comprises a voltmeter, wherein the controller is configured to cause the voltmeter to measure the voltage when the time delay expires.

15. The computer tomography apparatus of claim 11, wherein the controller is configured to determine the energy of the radiation particles based on the value of the voltage measured at the end of the time delay.

16. The computed tomography apparatus of claim 11, wherein the controller is configured to connect the electrode to electrical ground.

17. The computerized tomography apparatus of claim 11, wherein the rate of change of the voltage is substantially zero when the time delay expires.

18. The computerized tomography apparatus of claim 11, wherein the rate of change of the voltage is substantially non-zero when the time delay expires.

19. A computer tomography method, comprising: positioning a first radiation source at a relative position with respect to the object; directing a first divergent radiation beam from the first radiation source toward the object; capturing an image of a first portion of the object using the first divergent radiation beam using an image sensor; positioning a second radiation source at said relative position with respect to said object; directing a second divergent radiation beam from the second radiation source toward the object; capturing, using the image sensor, an image of a second portion of the object using the second divergent radiation beam, the first portion and the second portion being different; forming an image of the object by stitching the image of the first portion and the image of the second portion; wherein the image sensor, the first radiation source, and the second radiation source are configured to rotate around the object, and the relative positions between the image sensor, the first radiation source, and the second radiation source are fixed during the rotation around the object, wherein the first radiation source is in a first position relative to the object when the image sensor captures an image of the first portion of the object, and the second radiation source is in a second position relative to the object when the image sensor captures an image of the second portion of the object; Wherein the first position and the second position are the same.

20. The computer tomography method of claim 19, wherein: The first radiation source is deactivated when the first radiation source is not in the relative position, and the second radiation source is deactivated when the second radiation source is not in the relative position.

21. The computer tomography method of claim 19, wherein: Radiation generated by the first radiation source is prevented from reaching the object when the first radiation source is not in the relative position, and radiation generated by the second radiation source is prevented from reaching the object when the second radiation source is not in the relative position.

22. The computed tomography method of claim 19, wherein a portion of the first divergent radiation beam that would otherwise pass through the object to be incident on a dead zone of the image sensor is blocked when the first radiation source is in the relative position, and a portion of the second divergent radiation beam that would otherwise pass through the object to be incident on the dead zone of the image sensor is blocked when the second radiation source is in the relative position.

23. The computer tomography method of claim 19, wherein the image sensor comprises a plurality of radiation detectors spaced apart from one another; wherein capturing an image of a first portion of the object comprises receiving, with the radiation detector, a portion of the first divergent radiation beam that passes through the object; Wherein capturing an image of a second portion of the object comprises receiving, with the radiation detector, a portion of the second divergent radiation beam that passes through the object.

24. The computer tomography method of claim 19, wherein the first partial image of the object and the second partial image of the object have a spatial overlap.

25. The computed tomography method of claim 19, wherein positioning the first radiation source comprises rotating the first radiation source, the second radiation source, and the image sensor around the object.

Images