JP2016223950A - Radiation imaging apparatus, drive method for same, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique effective to improve photon counting precision in a photon counting-type radiation imaging apparatus.SOLUTION: A radiation imaging apparatus provided with a sensor panel where a plurality of sensor units each including a detection element for detecting a radiation are arranged, further comprises: a quantization unit for quantizing a signal value from the detection element of each sensor units; a counting unit for counting counts, per each sensor units, where a first pattern that includes a quantization result by the quantization unit for the signal value of the detection element of the sensor unit and a quantization result by the quantization unit for the signal value of the detection element of another sensor unit around the sensor unit matches a second pattern that is a preset reference pattern; and a read unit for reading a count value of the counting unit.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a radiation imaging apparatus, a driving method thereof, and a program.

  The radiation imaging apparatus includes, for example, a scintillator that converts radiation into light, and a sensor panel in which a plurality of sensor units that detect light (scintillation light) from the scintillator are arranged. In each sensor unit, a signal based on the amount of scintillation light is obtained.

  Some radiation imaging devices are of the photon counting type. In the photon counting type radiation imaging apparatus, each sensor unit measures the number of photons of radiation based on the result of detection of scintillation light. Specifically, photons of scintillation light are generated when radiation photons enter the scintillator, and the number of photons of radiation is measured by detecting the photons of the scintillation light by each sensor unit. According to the photon counting type radiation imaging apparatus, the radiation image is formed based on the number of photons of the measured radiation.

  By the way, the scintillation light can also diffuse in the horizontal direction (direction parallel to the upper surface of the sensor panel) in the scintillator. For this reason, not only the sensor unit corresponding to the incident position of the radiation but also a signal component accompanying detection of the scintillation light may be generated not only in the surrounding sensor units. This causes a reduction in the quality of the radiation image.

Special table 2013-501226 gazette JP 2003-279411 A

  Patent Document 1 discloses a radiation imaging apparatus including a plurality of pixels arranged in a matrix, a counter disposed at the center of each pixel, and another counter disposed between adjacent pixels. . According to Patent Literature 1, it is determined which counter value to increase based on the result of comparing the pixel value of each pixel with the pixel value of another pixel adjacent to that pixel. However, according to this radiation imaging apparatus, when irregular photons of radiation are incident (for example, when two or more photons are incident locally at one time, radiation not being detected such as cosmic rays is incident, etc. ) May not be properly compared.

  Patent Document 2 discloses a radiation imaging apparatus that calculates the center of gravity of a bright spot in a scintillator using luminance data of scintillation light. According to Patent Document 2, since the position of the bright spot in the scintillator is known from the calculation result, the imaging accuracy can be improved. However, according to this radiation imaging apparatus, when the irregular radiation photons are incident, the calculation may not be performed appropriately.

  These cause a decrease in photon count accuracy. Accordingly, an object of the present invention is to provide a technique advantageous for improving the photon count accuracy in a photon counting type radiation imaging apparatus.

  One aspect of the present invention relates to a radiation imaging apparatus, and the radiation imaging apparatus includes a sensor panel in which a plurality of sensor units each including a detection element that detects radiation is arranged, and each sensor A quantization unit that quantizes a signal value from the detection element of the unit, and for each sensor unit, a quantization result by the quantization unit for a signal value of the detection element of the sensor unit and a periphery of the sensor unit A counting unit that counts the number of times that a first pattern that includes a quantization result of the quantization unit for a signal value of the detection element of another sensor unit matches a second pattern that is a preset reference pattern; And a reading unit for reading the count value of the counting unit.

  According to the present invention, photon count accuracy can be improved.

It is a figure which shows the structural example of a radiation imaging device. It is a figure which shows the structural example of each unit for reading a signal from a sensor part. It is a figure which shows the structural example of a sensor part. It is an example of a drive timing chart including an irradiation period and a readout period. It is a figure which shows the example of operation | movement in each sensor part in an irradiation period. It is a figure which shows the example of intensity distribution of a scintillation light. It is a figure which shows the example of the measuring method of a radiation photon. It is a figure which shows the example of operation | movement in each sensor part in a read-out period. It is a figure which shows the example of intensity distribution of a scintillation light. It is a figure which shows the example of the measuring method of a radiation photon. It is a figure which shows the structural example of a sensor part.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. In the respective drawings, the same members or the same components are denoted by the same reference numerals, and redundant descriptions are omitted in the following embodiments.

(First embodiment)
FIG. 1 shows a configuration example of a radiation imaging apparatus 100 (or may be referred to as a “radiation imaging system”) according to the first embodiment. The radiation imaging apparatus 100 includes, for example, an irradiation unit 101 that irradiates a subject such as a patient, an irradiation control unit 102 that controls the irradiation unit 101, an imaging unit 104 that images a subject irradiated with radiation, And a processor 103. Note that the concept of radiation includes, for example, α rays, β rays and the like in addition to X-rays generally used for radiation imaging.

  The imaging unit 104 includes, for example, a scintillator 105 that converts incident radiation into light, and a sensor panel 106. The scintillator 105 is disposed on the side of the radiation surface of the sensor panel 106. In the sensor panel 106, for example, a plurality of sensor units 201 each detecting light from the scintillator 105 (scintillation light) are arranged so as to form a plurality of rows and a plurality of columns. The sensor unit 201 may be referred to as a “pixel”. As will be described in detail later, each sensor unit 201 has a configuration for performing photon counting radiation imaging, and based on the detection result of the scintillation light, radiation photons (hereinafter referred to as “radiation photons”). Measure the number.

  The processor 103 exchanges signals or data with the imaging unit 104, specifically controls the imaging unit 104 to perform radiation imaging, and receives signals obtained thereby from the imaging unit 104. This signal includes a measurement value of radiation photons. For example, the processor 103 generates image data for displaying a radiation image on a display unit (not shown) such as a display based on the measurement value. The processor 103 may perform a predetermined correction process on the image data. Further, the processor 103 supplies a signal for starting or ending radiation irradiation to the irradiation control unit 102. The processor 103 may also function as a drive unit that drives each of the above-described units and the components constituting the unit while synchronously controlling the units, but the drive unit is arranged separately from the processor 103. May be.

  Note that the configuration of the radiation imaging apparatus 100 is not limited to the above-described example, and other units may have a part of the functions of a unit, or some units may be integrated. You may be comprised so that it may become. For example, although the configuration in which the irradiation control unit 102 and the processor 103 are individually arranged has been illustrated, these may be realized by a single unit.

  FIG. 2 shows a configuration example of each unit on the sensor panel 106. The sensor panel 106 includes, for example, a plurality of sensor units 201, a vertical scanning circuit 202, a horizontal scanning circuit 203, and a column selection circuit 208. Here, for ease of understanding, the configuration in which the sensor units 201 of 3 rows × 3 columns are arranged is illustrated, but actually, the number is larger than this number, for example, about 2800 rows in the example of a 17-inch sensor panel. X About 2800 rows of sensor units 201 can be arranged.

  The vertical scanning circuit 202 forms a sensor driving unit for driving the plurality of sensor units 201, and may be configured by a shift register, for example. Specifically, the vertical scanning circuit 202 drives the operations of the plurality of sensor units 201 in units of rows using the signal lines 205 corresponding to each row. In this example, the signal lines 205 in each row include two signal lines (for example, 205-0R and 205-0B for the first row, 205-1R and 205-1B for the second row, and 205- for the third row. 2R and 205-2B). A signal from the sensor unit 201 is output to the column selection circuit 208 via the corresponding column signal line 204.

  The horizontal scanning circuit 203 and the column selection circuit 208 form a reading unit for reading a signal from each sensor unit 201. Specifically, the horizontal scanning circuit 203 is configured by, for example, a shift register or the like, and controls the column selection circuit 208 using a signal line 207 (207-0 or the like) corresponding to each column, and the sensor unit of the corresponding column. A signal is read from 201. The read signal is horizontally transferred via the output line 206 and output as output data DATA.

FIG. 3 shows a configuration example of the unit sensor unit 201. Here, paying attention to one sensor unit 201, the sensor unit 201 is referred to as “sensor unit 201 ₁ ” in order to distinguish it from the other sensor units 201. Sensor unit 201 ₁ includes, for example, detection element 301, a quantization unit _{U 1} including the monitoring unit 302 and the comparison unit 303, counting unit _{U 2} which includes a determination unit 307 and a memory 304, and an output unit 305.

  The detection element 301 detects the scintillation light from the scintillator 105 that has received radiation, and specifically converts the scintillation light into an electrical signal corresponding to the amount of light. As the detection element 301, a known photoelectric conversion element (eg, a photodiode) may be used.

The quantization unit U ₁ quantizes the light intensity (or a signal value corresponding thereto) detected by the detection element 301. Here, “quantization” includes conversion of the intensity of the light into a numerical value based on a predetermined standard, calculation of a numerical value corresponding to the intensity of the light, and the like, and can be interpreted in a broad sense. Specifically, in the quantization unit U ₁ , the monitor unit 302 monitors the amount of change in potential of the detection element 301. For the monitor unit 302, for example, a differential circuit can be used. The comparison unit 303 compares the result of monitoring by the monitor unit 302 (voltage corresponding to the amount of change in the potential of the detection element 301) with a predetermined reference value (reference voltage), and compares the comparison result with the signal line. Are output to the corresponding signal line.

In this example, two comparison units 303 are provided (303-R and 303-B, respectively). The two comparison units 303-R and 303-B have different reference voltage values. Voltages 306-R and 306-B are provided, respectively. The reference voltages 306-R and 306-B can be commonly supplied to the plurality of sensor units 201. For example, when the voltage corresponding to the amount of change in the potential of the detection element 301 is larger than the reference voltage 306-B, the comparison unit 303-B applies the quantization unit to the corresponding signal line in the signal line group 309. The digital value “1” is output as the output value of U ₁ . On the other hand, the comparison unit 303-B, when the voltage corresponding to the variation in the potential of the detecting element 301 is smaller than the reference voltage 306-B is in the corresponding signal line, as the output value of the quantization unit U ₁ Outputs the digital value “0”.

Here, the group 309 of signal lines, other signal lines for transmitting the output value of the quantization unit _{U 1} of the sensor unit 201 _1, the other sensors 201 of the periphery of the sensor unit 201 ₁ of the quantization unit _{U 1} A signal line for transmitting the output value is included.

Counting unit U _2, using the output value or the like of the quantization unit U _1, counting the number of radiation photons. Specifically, the count unit _{U 2,} the determining unit 307, from the group 309 of signal lines, the quantization unit _{U 1} of the output value and the other sensor unit 201 of the quantization unit _{U 1} of the sensor unit 201 ₁ output A pattern 310 (first pattern) including values is received. The determination unit 307 is supplied with a preset reference pattern 308 (second pattern). The determination unit 307 determines whether the pattern 310 received from the signal line group 309 matches the reference pattern 308. Determine. The determination unit 307 may be referred to as a collation unit that collates the pattern 310 and the reference pattern 308. If they match each other, the value in the memory 304 is added. That is, the memory 304 holds a measured value of the number of the pattern 310 and the reference pattern 308 matches as a count value of the counting unit U _2. Although details will be described later, the value of the memory 304 indicates the measurement result of the number of radiation photons.

  In this example, two determination units 307 are arranged (referred to as 307-R and 307-B, respectively), and the two determination units 307-R and 307-B have different reference patterns. 308-R and 308-B are supplied respectively. Two memories 304 are arranged so as to correspond to the two determination units 307-R and 307-B (referred to as 304-R and 304-B, respectively). For example, when the pattern 310 received from the signal line group 309 matches the reference pattern 308-B, the determination unit 307-B adds “1” to the value of the memory 304-B. On the other hand, when the pattern 310 and the reference pattern 308-B do not match, the determination unit 307-B keeps the value of the memory 304-B (adds “1” to the value of the memory 304-B). do not do.). Note that the above determination may be performed by a predetermined arithmetic process such as exclusive OR, and the determination units 307-R and 307-B can be configured with relatively simple circuits.

  Two output units 305 are arranged to correspond to the two memories 304-R and 304-B (referred to as 305-R and 305-B, respectively). For example, the output unit 305-B outputs the value from the corresponding memory 304-B via the column signal line 204 based on, for example, a control signal supplied via the signal line 205-0B. The same applies to the output unit 305-R.

According to the above configuration example, in each sensor unit 201, the quantization unit U ₁ quantizes the intensity of light detected by the detection element 301. The counting unit U ₂ is the output value of the quantization unit U _1, else (other sensor portion 201 of the periphery of the sensor unit 201 quantization unit U ₁ belongs) of the quantization unit U ₁ The number of radiation photons is measured based on the output value. A more specific measurement method will be described later.

  FIG. 4 illustrates an outline of a drive timing chart of the radiation imaging apparatus 100, and this example illustrates an aspect in the moving image mode. In the figure, the horizontal axis represents the time axis, and the vertical axis represents the operation of the apparatus 100, the radiation dose (a high level indicates an irradiation state, and a low level indicates a non-irradiation state), and an output. Output data DATA output via line 206 is shown. In the moving image mode, the radiation imaging apparatus 100 alternately performs a measurement operation (first operation) for measuring the number of radiation photons and a read operation (second operation) for reading out a measurement result by the measurement operation. In the period during which the measurement operation is performed, radiation is irradiated (in the figure, this period is indicated as “irradiation period A”), and in the period during which the reading operation is performed, radiation irradiation is stopped (in the figure). (This period is referred to as “reading period B”.) Then, using the measurement result of the number of radiation photons obtained by the reading operation, image data for one frame is generated by the processor 103 (third operation). In the moving image mode, the series of operations may be performed a plurality of times, and the moving image can be reproduced by sequentially outputting the image data for one frame obtained by the series of operations for one time to the display unit. Here, the mode of the moving image mode is illustrated, but the same operation may be performed even in the continuous shooting mode. In the case of the still image mode, the above series of operations may be performed once.

Hereinafter, a method for measuring radiation photons in the irradiation period A will be described with reference to FIGS. Figure 5 is a timing chart for explaining the operation of the sensor unit 201 ₁ in the illumination period A. In the figure, the horizontal axis represents the time axis, and the vertical axis represents the incident radiation photons indicated by arrows, while the output of the monitor unit 302, the outputs of the comparison units 303-R and 303-B, and the memory 304-R. And 304-B.

First, the case where the first radiation photon in the figure enters the scintillator 105 will be described. In response to the incidence of the first radiation photons, the potential of the detection element 301 changes, and the output of the monitor unit 302 changes. In this example, it is assumed that the output of the monitor unit 302 is larger than the reference voltage 306-R and smaller than the reference voltage 306-B. In this case, the output of the comparison unit 303-R is “1”, and the output of the comparison unit 303-B is “0”. Determination unit 307-R, via a group 309 of signal lines, the comparison of with receiving a comparison result of the comparison unit 303-R and 303-B in the sensor unit 201 _1, with other sensors 201 near its The comparison results of the sections 303-R and 303-B are further received.

As described above, the comparison unit compares the result of the 303-R and 303-B of the sensor unit 201 ₁ corresponds to the output value of the quantization unit _{U 1} of the sensor unit 201 _1. Similarly, the comparison unit compares the result of the 303-R and 303-B in the other sensor portion 201 of the peripheral corresponds to the output value of the quantization unit _{U 1} of the other sensor unit 201. Determination unit 307-R in the sensor unit 201 _1, these output values, receiving a pattern 310 described above. The determination unit 307-R compares the pattern 310 with the reference pattern 306-R to determine whether or not they match, and if they match, adds “1” to the value in the memory 304-R. If you don't, don't add. The same applies to the determination unit 307-B. In this example, “1” is added to the value of the memory 304-R and not added to the value of the memory 304-B (the value of the memory 304-R is “1”, and the value of the memory 304-B is It remains “0”).

  Next, a case where the second radiation photon enters the scintillator 105 and the output of the monitor unit 302 changes will be described. In this example, it is assumed that the output of the monitor unit 302 is larger than both the reference voltages 306-R and 306-B. In this case, the outputs of both the comparison units 303-R and 303-B are “1”. Then, each of the determination units 307-R and 307-B performs determination in the same procedure, and as a result, in this example, “1” is added to both values of the memories 304-R and 304-B. (The value of the memory 304-R is “2”, and the value of the memory 304-B is “1”).

  When the third radiation photon is incident on the scintillator 105, the third radiation photon has the same energy as that of the first radiation photon, and the same operation as when the first radiation photon is incident. Is done. As a result, in this example, “1” is added to the value of the memory 304-R and not added to the value of the memory 304-B (the value of the memory 304-R is “3”, and the memory 304-B The value of “1” remains “1”).

Here, for example, if one radiation photons is incident toward the sensor unit 201 _1, it scintillation light generated by the scintillator 105 may be, can diffuse in the horizontal direction (upper surface in parallel direction of the sensor panel 106) .

  FIG. 6A shows an intensity distribution (luminance distribution) of scintillation light when radiation photons with relatively large energy are incident, and a distribution obtained by converting the intensity distribution into a value corresponding to the output of the monitor unit 302. . In the converted distribution, reference voltages 306-R and 306-B are shown for comparison. FIG. 6B shows the case where a radiation photon having a relatively small energy is incident as in FIG.

For FIG. 6 (a), the intensity of light at the center of the sensor portion 201 ₁ in the figure, greater than the value corresponding to the reference voltage 306-B. In the case of FIG. 6A, the intensity of light at another adjacent sensor unit 201 can be larger than a value corresponding to the reference voltage 306-R. On the other hand, in the case of FIG. 6 (b), the intensity of light at the center of the sensor portion 201 ₁ in the figure, than the value corresponding to the large and the reference voltage 306-B than the value corresponding to the reference voltage 306-R small. In the case of FIG. 6B, the light intensity at the other adjacent sensor unit 201 is smaller than the value corresponding to the reference voltage 306-R.

FIG. 7 shows the intensity distribution of the scintillation light in the case of FIG. 6A quantified, and each value is a value quantized by the quantization unit U ₁ described above. Hereinafter, for ease of explanation, it is expressed as “light intensity” (or simply expressed as “intensity” in some cases). Specifically, the intensity of light at the center of the intensity of light at the sensor unit 201 ₁ is shown as "2", the same other sensors 201 that are adjacent in the opposite side direction and the diagonal direction in the drawing "1 ”And the intensity of light at the other sensor unit 201 outside them is indicated as“ 0 ”. These values are given by the comparison results of the comparison units 303-R and 303-B and can be read out from the signal line group 309. More specifically, for example, if the outputs of both the comparison units 303-R and 303-B are “1”, the light intensity is “2”. If the output of the comparison unit 303-R is “1” and the output of the comparison unit 303-B is “0”, the light intensity is “1”. Further, if the outputs of both the comparison units 303-R and 303-B are “0”, the light intensity is set to “0”.

Here, in the center of the sensor portion 201 ₁ of the figure, the determination unit 307 of the counting unit _{U 2} is from the group 309 of signal lines, the light of the sensor unit 201 ₁ intensity and "2", other around the The light intensity of the sensor unit 201 is received. Here, said other sensor unit 201 includes two sensors 201 adjacent the sensor unit 201 ₁ and the row direction, and two sensors 201 adjacent the sensor unit 201 ₁ and the column direction (for both The light intensity is “1”). That is, the determining unit 307, a sensor unit 201 _1, the same receives the intensity of light for a total of five sensors 201 and four sensors 201 that are adjacent to each other in each row and column directions. In this example, the light intensity pattern 310 for the five sensor units 201 matches the reference pattern 308, and the determination unit 307 adds “1” to the value in the memory 304 accordingly.

On the other hand, in the sensor units 201 adjacent to each other in the diagonal direction of the sensor unit 201 ₁ (referred to as “sensor unit 201 ₂ ” for distinction), the determination unit 307 of the count unit U ₂ receives the signal line group 309 from the signal line group 309. the intensity of the light for the sensor unit 201 ₂ "1", receives the intensity of light for other sensor portion 201 of its periphery. Here, the other sensor unit 201 includes _two sensor units 201 adjacent to the sensor unit 2012 in the row direction (one has a light intensity “1” and the other has a light intensity “0”). And _two sensor units 201 adjacent to the sensor unit 2012 in the column direction (one has a light intensity “1” and the other has a light intensity “0”). The sensor unit 201 _2, a pattern 310 of light intensity for these total of five sensors 201, the reference pattern 308 for a mismatch, the determining unit 307 does not add a "1" to the value of the memory 304.

As described above, when one radiation photons is incident toward the sensor unit 201 _1, it scintillation light generated by the scintillator 105 may be, it can diffuse in the horizontal direction. That is, a part of the scintillation light (substantial majority) is while towards the sensor unit 201 _1, a portion of the other of the light, can toward the other sensors 201 of the periphery of the sensor unit 201 _1. As a result, not only the signal from the sensor unit 201 _1, even signals from other sensors 201 may become to have the signal component in response to detection of the scintillation light. Therefore, when these signals are used as part of image data, the quality of the image may be reduced.

According to this configuration example, the count unit _{U 2} of the sensor unit 201 _1, the output value from the quantization unit _{U 1} of the sensor unit 201 ₁ (i.e., a quantization result of the intensity of light at the sensor unit 201 _1. ) And the output value from the quantization unit U ₁ of the other sensor unit 201 around the sensor unit 201 ₁ (that is, the result of quantizing the light intensity at the other sensor unit 201). Receive. Then, the counting unit _{U 2,} determination unit 307 determines whether the pattern 310 and the reference pattern 308 is matched. When the above pattern 310 and a reference pattern 308 is matched, as a radiation photon is incident on the sensor unit 201 _1, "1" is added to the value of the counting unit U ₂ of the memory 304. On the other hand, in the case where the above pattern 310 and a reference pattern 308 do not match, the sensor unit 201 ₁ as radiation photons are not incident, does not change the value of the count unit U ₂ of the memory 304 ( "1 Is not added). Reference pattern 308, i.e., it can be said that the prediction pattern showing the light intensity distribution of the estimated from (diffusion of light from directly above the sensor unit 201 ₁ to the sensor section 201 near its) diffusion of light in the scintillator 105 .

In other words, the sensor unit 201 _1, with the other sensors 201 near its share detection value of the scintillation light. The sensor unit 201 _1, the detection value of the sensor unit 201 ₁ itself and on the basis of the detected value of the other sensor unit 201 of the periphery thereof whether the photons of the radiation to the sensor unit 201 ₁ is incident The determination is made with reference to the reference pattern 308.

In the above example, as the other sensor unit 201, and two sensor portions 201 which are adjacent sensor unit 201 ₁ and the row direction, illustrated and two sensor portions 201 which are adjacent sensor unit 201 ₁ and the column direction. However, said other sensor unit 201 may be one arranged around or near the sensor unit 201 ₁ may be one adjacent to each other in the sensor unit 201 ₁ and the row or column direction, but the other ones But you can. For example, it said other sensor unit 201 may also include adjacent ones in the sensor unit 201 ₁ and the diagonal direction, may include those not adjacent to the sensor unit 201 _1, or a combination thereof It may be a thing. Further, in this embodiment, as the reference pattern 308 is associated with two sensors 201 which are adjacent the sensor unit 201 ₁ and the row direction (a "2". In this example) the value associated with the sensor unit 201 ₁ value (in this example is "1".) and the sensor unit 201 ₁ and the value associated with the two sensors 201 which are adjacent in the column direction (in the present example is "1".), and a total of five Examples that include values. However, the reference pattern 308 is not limited to the pattern of this example, and may include more values.

Further, according to this configuration example, the sensor unit 201 _1, the number of measurement of the radiation photons by the count unit U _2, made for each strength detected by the detecting element 301 light "1" and "2" The Specifically, by using the two comparison units 303-R and 303-B, the intensity is set to “0” when the output of the monitor unit 302 is smaller than the reference voltage 306-R. In this case, the radiation photons are or if it is determined as not incident on the sensor unit 201 _1. Further, when the output is larger than the reference voltage 306-R and smaller than the reference voltage 306-B, the intensity is “1”. In this case, the radiation photons having the energy corresponding to the intensity “1” are detected by the sensor unit 201 _1. What is necessary is just to judge that it injected into. Is the intensity "2" if the output is greater than the reference voltage 306-B, in this case, the radiation photons of energy corresponding to said intensity "2" need be determined that entering the sensor unit 201 ₁ . The counting unit U ₂ is the measurement of the radiation photons can be performed for each of the strength, in other words, the count unit U ₂ is the measurement of the radiation photons may be carried out for each energy of the radiation photons.

This can be done by setting the reference pattern 308 for each intensity. In the configuration of this example, the reference pattern 308-R may be set to correspond to the intensity “1”, and the reference pattern 308-B may be set to correspond to the intensity “2”. The determination unit 307-R that receives the reference pattern 308-R measures the number of radiation photons corresponding to the intensity “1”, and the determination unit 307-B that receives the reference pattern 308-B sets the intensity to “2”. The number of corresponding radiation photons is measured. For example, the reference pattern 308 illustrated in FIG. 7 corresponds to a pattern for measuring that a radiation photon corresponding to the intensity “2” is incident. Thus, the counting unit U _2, it is also possible radiation photons how much energy is identified whether the incident on the sensor unit 201 _1. In addition, although the number of each said units, such as comparison part 303-R and 303-B, was 2 in this example, you may make it 3 or more.

In the above, the method for measuring the number of radiation photons has been described with a focus on _one sensor unit 2011. However, the same applies to each of the other sensor units. ₂ is used to measure the number of radiation photons. And their measurement results (i.e., the count value of the counting unit U ₂₎ is output to the processor 103 by the output unit 305 is used to generate the image data.

In the above-described measurement operation in the irradiation period A, the operation frequency of the sensor unit 201 ₁ (mainly the quantization unit U ₁ and the count unit U ₂ ) and the irradiation amount of the irradiation unit 101 are set one by one. This can be done by setting it to a value that can be measured. For example, the operating frequency of the sensor unit 201 ₁ may be set within a range of a few [MHz] from 10 [kHz] (for example, about 100 [kHz]). For example, the irradiation amount of the irradiation unit 101 may be set as a value when the tube voltage is about 100 [kV] and the tube current is about 10 [mA].

  FIG. 8 shows an example of the operation of the sensor unit 201 in the readout period B as an example of a method for reading out the measurement result obtained by the above-described measurement method. In the figure, the horizontal axis represents the time axis, and the vertical axis represents the waveform of the control signal propagating through the signal line 205 (205-0R, etc.) and the signal line 207 (207-0, etc.) described with reference to FIG. , And output data DATA propagating through the output line 206. In the readout period B, the signals on the signal lines 205-0R, 205-0B, 205-1R, 205-1B, 205-2R, and 205-2B are activated in order. Further, the respective signals on the signal lines 207-0, 207-1 and 207-2 are sequentially activated while the respective signals are activated.

For example, first, the signal on the signal line 205-0R is activated, and the signals on the signal lines 207-0, 207-1, and 207-2 are activated in the meantime. As a result, the value of the memory 304 -R in each sensor unit 201 in the first row is read out by the output unit 305 -R through the column signal line 204, and the first column and the first column through the output line 206. The data are output in the order of the second column and the third column, respectively. Thereafter, in the same manner, the signal on the signal line 205-0B is activated, and the signals on the signal lines 207-0, 207-1, and 207-2 are sequentially activated in the meantime. As a result, the value of the memory 304-B in each sensor unit 201 in the first row is read out by the output unit 305-B via the column signal line 204, and the first column, the first column through the output line 206. The data are output in the order of the second column and the third column, respectively. Thus, reading the count value of the counting unit U ₂ in the respective sensor portions 201 of the first row is completed. Thereafter, in the same manner as the read for the first row, the read count value of the counting unit U ₂ in the second row and the sensor portion 201 of the third row are made sequentially. Thus, the reading of the count value of the counting unit U ₂ for all of the sensor unit 201 is completed.

The processor 103 generates an image data of one frame by using the thus read count value of the counting unit U ₂ (i.e., the number of measurement results of the radiation photons). As described above, since the number of radiation photons can be measured for each energy of the radiation photons, the radiation image based on the image data is displayed with a color corresponding to the energy level. May be displayed on the display unit.

  As described above, according to the present embodiment, even when light is detected by the detection element 301 of the sensor unit 201, radiation photons are incident on the sensor unit 201 when the pattern 310 and the reference pattern 308 do not match. Do not count the number of radiation photons as if not. Therefore, for example, when irregular radiation photons are incident, erroneous measurement of radiation photons that can be caused by the radiation radiation can be prevented. Note that when irregular radiation photons are incident, for example, when two or more photons are incident locally at one time, a type of radiation different from the radiation to be detected (for example, cosmic rays) may be used. ) Is incident on the detection element 301 (without being converted into light by the scintillator 105). Therefore, according to the present embodiment, the photon count accuracy can be improved. This is particularly effective when the incident radiation has a relatively large energy or when the amount of scintillation light diffused in the horizontal direction is large.

  Note that the irregular radiation photons can be measured by adding a pattern for detecting the irregular radiation photons to the reference pattern 308. In addition to this, another comparison unit 303 for detecting the irregular radiation photons may be added to the sensor unit 201.

(Second Embodiment)
A second embodiment will be described with reference to FIGS. In the first embodiment described above, the case where the scintillation light generated according to the incidence of radiation photons is uniformly diffused in the horizontal direction is exemplified. However, some radiation photons, for example, change their traveling direction when passing through the subject and enter obliquely with respect to the upper surface of the sensor panel 106. In this case, the diffusion direction of the scintillation light can be biased. This embodiment is different from the first embodiment described above in that the incident angle of radiation photons is specified based on the deviation in the diffusion direction of the scintillation light.

  FIG. 9A shows the intensity distribution of the scintillation light when the radiation photons are incident on the upper surface of the sensor panel 106 obliquely (in the direction from the upper left to the lower right in the figure), and the intensity distribution of the monitor 302 The distribution converted into a value corresponding to the output is shown. FIG. 9B shows a case where radiation photons are incident in a direction crossing the direction of the example of FIG. 9A (in the direction from the upper right to the lower left in the figure). According to FIGS. 9A and 9B, when the scintillation light is incident obliquely, the diffusion amount of the scintillation light in the direction parallel to the incident direction is larger than the diffusion amount of the scintillation light in the direction intersecting with the incident direction. Can be.

FIG. 10 shows the intensity distribution of scintillation light in the case of FIG. In this example, the intensity of light at the other sensor unit 201 adjacent to the sensor unit 2011 in _one side in the opposite direction is indicated as “0”, which is the same as the example of the first embodiment (see FIG. 7). Different.

Each sensor unit 201, counting unit U ₂ is checked by a procedure similar to that in the first embodiment, whether the corresponding pattern 310 and a reference pattern 308 is matched. Here, in this example, a plurality of reference patterns 308 are prepared (respectively 308 _{1 to} 308 ₅ ), and the plurality of reference patterns 308 _{1 to} 308 ₅ respectively correspond to the deviation in the diffusion direction of the scintillation light. . For example, in this example, the pattern 308 ₁ (which is the same pattern as in the first embodiment) corresponds to the case where there is no bias in the scintillation light diffusion direction. Pattern 308 ₂ corresponds to the case of the polarizing Riga row direction. Pattern 308 ₃該偏Ri corresponds to the case in the column direction. Pattern 308 ₄該偏Ri corresponds to the case of one of the diagonal directions. Pattern 308 ₅該偏Ri corresponds to the case of the other diagonal direction.

For example, for the sensor unit 201 _1, pattern 310 in order to match the pattern 308 ₅ out of a plurality of reference patterns 308 adds "1" to the value of the memory 304. In this case, the count unit U ₂ may further include a specifying unit configured to specify the direction of incidence of the scintillation light, the specific unit, or matches one pattern 310 of the plurality of reference patterns 308 The incident direction may be specified based on the information. Then, information indicating the direction of incidence is the identified may be read together with the count value of the counting unit U _2. The processor 103 generates an image data of one frame with the incident direction, which is the count value and the specific counting unit U ₂ which is read out the.

Note that the sensor unit 201 _2, pattern 310, because it does not match any of the plurality of reference patterns 308, not by adding "1" to the value of the memory 304.

  According to the present embodiment, the same effect as that of the first embodiment can be obtained, and the incident angle of the radiation photon can be specified, and the information of the subject is three-dimensionally based on the specified incident angle. The radiation image can be displayed in 3D.

(Third embodiment)
The radiation photon measurement method according to the first to second embodiments described above uses the quantization unit U ₁ and the count unit U ₂ , but these functions are performed on a program or software in the processor 103, for example. It may be realized with. That is, the sensor unit 201 is configured by a circuit for outputting a signal corresponding to the amount of scintillation light, and the intensity of the light is quantized and the number of radiation photons is measured outside the sensor unit 201. Also good.

  FIG. 11 shows a configuration example of the sensor unit 201 ′ according to the third embodiment. In addition to the detection element 301, the sensor unit 201 'includes, for example, a reset unit 510, a signal amplification unit 520, a light sensitivity selection unit 530, a clamp unit 540, a first sampling unit 550, and a second sampling unit 560. The reset unit 510 includes a transistor M1, and resets the potential of the detection element 301 by turning on the transistor M1. Signal amplifier 520 includes transistors M2-M3 connected to a current source. By making the transistor M2 conductive, the transistor M3 performs a source follower operation, whereby a signal corresponding to the amount of charge generated in the detection element 301 is amplified.

  Photosensitivity selection unit 530 includes transistors M4 to M7 and capacitors C4 to C5. For example, when the transistor M4 is turned on, the capacitor C4 is connected to the gate of the transistor M3, and when the transistor M6 is turned on, the transistor M7 performs a source follower operation. Thereby, the signal amplification factor of the signal according to the charge amount generated in the detection element 301 can be changed. Further, by making the transistor M5 conductive, the capacitor C4 is connected to the gate of the transistor M3, and the signal amplification factor can be further changed.

  Clamp unit 540 includes transistors M8 to M10 and a capacitor C1. The output from the signal amplifying unit 520 when the detection element 301 is reset is supplied to one terminal n1 of the capacitor C1, and the other terminal n2 of the capacitor C1 is supplied with power by turning on the transistor M8. Voltage is supplied. Thereby, the voltage when the detection element 301 is reset is clamped as a noise component between the terminals n1 and n2. After that, the transistor M8 is turned off and the transistor M9 is turned on, so that the transistor M10 performs a source follower operation. A signal corresponding to a change in voltage at the terminal n2 due to detection of light by the detection element 301 is amplified by the source follower operation of the transistor M10 and output to the sampling unit 550 or 560.

  The sampling unit 550 includes transistors M11 to M13, a capacitor C2, and an analog switch SW2, and samples a signal (S signal) corresponding to the amount of light detected by the detection element 301. Specifically, the signal from the clamp unit 540 can be sampled and held in the capacitor C2 by controlling the transistor M11. The signal is amplified by the transistor M12 that performs the source follower operation, and is output to the column signal line 204 via the analog switch SW2. Note that the transistor M13 can be disposed, for example, in an electrical path between the capacitor C2 and the capacitor C2 of another sensor unit around the sensor unit 201 '. By making the transistor M13 conductive, it is possible to obtain an average of the S signal of the sensor unit 201 ′ and the S signals of other sensor units in the vicinity thereof, and the difference in noise components between them. Can be relaxed. The sampling unit 560 may sample a signal (N signal) corresponding to the noise component and have the same configuration as the sampling unit 550.

Since the value of the signal read from each sensor unit 201 ′ as described above indicates the intensity of the light detected by the detection element 301, the processor 103 determines whether each sensor unit 201 is based on the value of the signal. 'About the light intensity can be quantized. That is, the processor 103 can achieve the function of the quantization unit U ₁ described above. Further, the processor 103 can acquire the above-described pattern 310 based on the quantization result, determine whether the pattern 310 and the reference pattern 308 match, and count the number of times of matching. That is, the processor 103 may perform the functions of the aforementioned counter U _2.

Note that the sensor unit 201 ′ illustrated in the present embodiment is not limited to the configuration example of FIG. 11, and other configurations for detecting radiation may be employed. For example, the sensor unit may be provided with the function of the quantization unit U ₁ and the processor 103 may have the function of the counter unit U ₂ .

As described above, according to the present embodiment, radiation photons are measured by realizing the functions of the quantization unit U ₁ and the counter unit U ₂ outside the sensor unit while using a sensor unit having a known configuration. The same effect as the first embodiment can be obtained.

(Other)
In the above, some preferred embodiments have been illustrated, but it goes without saying that the present invention is not limited to these examples, and some of the examples may be modified without departing from the gist of the present invention. May be. In the above example, the so-called “indirect conversion type” configuration in which the radiation is converted into light by the scintillator 105 and the light is converted into an electric signal by the detection element 301 has been referred to. Further, the present invention may be applied to a so-called “direct conversion type” configuration that converts an electrical signal.

  The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in the computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

100: Radiation imaging device, 105: Scintillator, 106: Sensor panel, 201: Sensor unit, 301: Detection element, U ₁ : Quantization unit, U ₂ : Count unit, 308: Second pattern (reference pattern), 310: First pattern.

Claims (16)

A radiation imaging apparatus including a sensor panel in which a plurality of sensor units each including a detection element that detects radiation is arranged,
A quantization unit that quantizes a signal value from the detection element of each sensor unit;
For each sensor unit, the quantization result by the quantization unit for the signal value of the detection element of the sensor unit and the quantization unit for the signal value of the detection element of another sensor unit around the sensor unit A count unit that counts the number of times that the first pattern including the quantization result matches the second pattern that is a preset reference pattern;
A radiation imaging apparatus, further comprising: a reading unit that reads a count value of the counting unit. The quantization unit and the counter unit are arranged in each of the plurality of sensor units, and the count unit of each sensor unit includes an output value from the quantization unit of the sensor unit and a periphery of the sensor unit. The number of times that the first pattern and the second pattern coincide with each other is counted using the pattern including the output value from the quantization unit of another sensor unit as the first pattern. The radiation imaging apparatus described. Further comprising a scintillator disposed on the radiation side of the sensor panel;
The radiation imaging apparatus according to claim 1, wherein the detection element detects light from the scintillator. The quantization unit includes a monitor unit that monitors a change amount of the potential of the detection element, and a comparison unit that compares a magnitude relationship between the monitored change amount and each of two or more reference values. The radiation imaging apparatus according to any one of claims 1 to 3. The counting unit includes a determination unit that determines whether the first pattern and the second pattern match, and a memory that stores the number of times when the first pattern and the second pattern match. The radiation imaging apparatus according to claim 1, wherein the radiation imaging apparatus includes: In the counting by the counting unit for each sensor unit, when the first pattern and the second pattern coincide with each other, the determination unit includes the sensor unit and other sensor units in the vicinity thereof. The radiation imaging apparatus according to claim 5, wherein it is determined that radiation photons are incident on the part. The counting unit is
Receiving a plurality of the second patterns;
The radiation imaging apparatus according to any one of claims 1 to 6, wherein counting is performed when the first pattern matches one of the plurality of second patterns. The radiation imaging apparatus according to claim 7, wherein the counting unit counts the number of times of coincidence for each of the plurality of second patterns. The counting unit includes a specifying unit that specifies an incident direction of photons of radiation based on which one of the plurality of second patterns matches the first pattern. The reading unit includes the specified incident The radiation imaging apparatus according to claim 7 or 8, wherein information indicating a direction is further read. The plurality of sensor units are arranged to form a plurality of rows and a plurality of columns,
The first pattern used by the counting unit is:
Quantization result by the quantization unit for the signal value of the detection element of each sensor unit;
Quantization results by the quantization unit for the signal values of the detection elements of the two sensor units adjacent to the sensor unit in the row direction,
Quantization results by the quantization unit for the signal values of the detection elements of the two sensor units adjacent in the column direction to the sensor unit,
The radiation imaging apparatus according to claim 1, wherein the radiation imaging apparatus includes: The plurality of sensor units are arranged to form a plurality of rows and a plurality of columns,
The first pattern used by the counting unit is:
Quantization result by the quantization unit for the signal value of the detection element of each sensor unit;
Quantization results by the quantization unit for the signal values of the detection elements of the eight sensor units arranged to surround the sensor unit around the sensor unit;
The radiation imaging apparatus according to claim 1, wherein the radiation imaging apparatus includes: The radiation imaging apparatus according to any one of claims 1 to 11, further comprising a processor that generates image data based on a count value of the count unit read by the reading unit. The processor is
A first operation of performing the quantization by the quantization unit and the counting by the counting unit for each sensor unit;
The radiation imaging apparatus according to claim 12, wherein a second operation of generating image data for one frame based on a count value of the counting unit obtained in the first operation is performed. The radiation imaging apparatus according to claim 13, wherein the processor reproduces a moving image by performing a series of operations including the first operation and the second operation a plurality of times. A method for driving a radiation imaging apparatus including a sensor panel in which a plurality of sensor units each including a detection element that detects radiation is arranged,
The method for driving the radiation imaging apparatus includes:
Quantizing a signal value from the detection element of each sensor unit;
For each sensor unit, a first pattern including the quantization result for the signal value of the detection element of the sensor unit and the quantization result for the signal value of the detection element of another sensor unit around the sensor unit Counting the number of times the second pattern, which is a preset reference pattern, matches,
Reading a count value for each sensor unit obtained in the counting step;
A method for driving a radiation imaging apparatus, comprising: A program causing a computer to execute each step according to claim 15.