JP3257270B2 - Imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus for radiographic images such as X-ray images used for medical diagnosis and the like.

[0002]

2. Description of the Related Art As an apparatus for obtaining an image of an object using radiation, a radiation flux containing information on a subject from a radiation source is incident on an array-like sensor, and the intensity information is expressed on a screen such as a CRT. There is a radiation imaging device. In addition, in this type of imaging apparatus, a so-called photon counting method has conventionally been adopted in which a pulse signal generated from a sensor due to the incidence of radiation photons is counted, and the counted value is used as image density information.

[0003]

Incidentally, in the radiation detector constituting the array sensor, if the intensity of the incident radiation is high, saturation occurs, and the counting of the number of photons may become impossible. Also, for example, CdT
In solid-state radiation detectors using compound semiconductors such as e, when the intensity of incident radiation is high, the internal charge density increases, polarization effects, etc. occur. The number of pulses may drop sharply.

When the above-mentioned saturation or the like occurs, it becomes impossible to correct the count value for the pixel corresponding to the region where the saturation occurs, and the resulting image becomes very difficult to see. Further, the occurrence of such saturation also causes a reduction in the dynamic range.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an imaging apparatus capable of obtaining a high-quality image having a wide dynamic range without being affected by saturation of a sensor. To provide.

[0006]

In order to achieve the above object, an image pickup apparatus according to the present invention comprises a plurality of sensors S arranged in an array sensor 1 as shown in FIG.
.. of S, an absorber 1a for reducing the amount of photons incident on the sensor S is provided on the incident surface of the sensor at a predetermined position (the sensor constituting the first row L1), and one pixel forming an image is formed. A data processing unit (arithmetic processing unit 4) configured to detect each of the sensors with and without the absorber, and taking in a photon count value based on the output of the sensors S. A comparison means for comparing the photon count value based on the output of the sensor with the absorber with a reference value Th, wherein the data processing means determines whether or not the pixel whose comparison result is equal to or greater than the reference value Th is the sensor with the absorber; It is characterized by outputting only the count value based on the output as pixel data.

[0007]

When the absorber is arranged on the incident surface of the radiation sensor, as shown in the graph of FIG. 2, the intensity of the incident radiation can be reduced to, for example, に 対 し て compared to the case without the absorber. In other words, in the sensor in which the absorber is arranged, although the sensitivity is reduced, the intensity of the incident radiation causing saturation is apparently increased, and the limit incident amount is increased. Therefore, a sensor in which an absorber is arranged can detect a high dose region.

Accordingly, in the present invention, a high-dose area that cannot be detected by a normal sensor (without an absorber) is covered by a sensor with an absorber by detecting one pixel with a sensor with and without an absorber.

That is, as shown in FIG. 2, a dose Xn (including a margin value) close to the limit incident amount at which the sensor without the absorber causes saturation is referred to the number of photons generated when the light enters the sensor with the absorber. Value Th,
This reference value Th is compared with the photon count value based on the output of the sensor with the absorber, and when the comparison result is equal to or greater than the reference value Th, the count value by the sensor with the absorber is adopted as the pixel data to thereby obtain a high dose. Increase the detection range of the area.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of the present invention.

First, an array sensor 1 used in this example
Is a line sensor in which radiation sensors S..S are arranged in four rows and a plurality of columns, and an absorber 1a is formed on the incident surface of the radiation sensors S..S constituting the first row L1.

The absorber 1a is made of a P formed by a semiconductor fine processing technique (such as vapor deposition and photolithography).
With a metal film such as b or Au, the amount of radiation incident on the sensor S can be reduced to about 1/2. However, the radiation intensity is intended for a region (for example, 60 to 140 KV) used in this type of imaging apparatus.

The above array sensor 1 is scanned stepwise at a predetermined pitch (sensor arrangement pitch) in the direction of the arrow in FIG. 1st line L1 to 4th line L4
Of sensors S pass sequentially. Therefore, in this example, one pixel is detected by a total of four sensors.

The output of each sensor S in the array sensor 1 is introduced into a counting circuit 3,... 3 based on a known photon counting system comprising an amplifier, a comparator, a counter, etc., and the counting circuit 3,. The output (count value) of 3 is taken into the arithmetic processing unit 4. A comparison section 5 is connected to the output side of each of the counting circuits 3... 3 connected to the first row L1 of the array sensor 1.

The comparing unit 5 compares the count value output from the counting circuit 3 with a reference value Th, which will be described later, and when the count value becomes equal to or greater than the reference value Th, generates a signal indicating that fact. 4

When the result of comparison by the comparing section 5 is equal to or smaller than the reference value Th, the arithmetic processing section 4 sets the value of the
Calculations such as addition are performed using count values based on the outputs of the four sensors S in the rows L1 to L4, and the calculated values are output as pixel data of one pixel. However, 1
The count value based on the output of the sensor S in the line L1 is corrected using the degree of attenuation of the dose by the absorber 1a. On the other hand, when the comparison result is equal to or greater than the reference value Th,
Only the count value based on the output of the sensor S in the first row L1 of the array sensor 1 is configured to be output as pixel data, and the pixel data output from the arithmetic processing unit 4 is an image for each pixel. The data is sequentially stored in the memory 6. Then, an image based on the content stored in the image memory 6 is displayed on the display device 7.

Here, the reference value Th set in the comparison unit 5
Is a sensor S (2) without an absorber as shown in FIG.
The dose Xn close to the limit incident dose at which the lines L2 to L4) cause saturation is given by the sensor S with the absorber.
The number of photons generated when the light is incident on (first line L1). If a high-intensity region where the sensor S without the absorber causes saturation is present in the region to be imaged, the pixel in that region is used. As the data, the count value based on the output of the sensor S of the second row L2 to the fourth row L4 of the array sensor 1 is not adopted, and the sensor S of the first row L1 is used.
Only the count value based on the output of (1) will be adopted.

Therefore, in the embodiment of the present invention, the absorber 1
The sensor S for high counting in which a is formed and the sensor for low counting without an absorber can be selectively used for each pixel, whereby, for example, a high transmission dose such as an image background or an edge of an imaging target is high. The portion can be detected by a high-count sensor, and the inside of the imaging target can be detected by a low-count sensor. as a result,
An image with a wide dynamic range without influence of saturation can be obtained.

In the above embodiment, only the sensor S constituting the first row L1 of the array sensor 1 has the absorber 1
a, but in addition to this, for example, FIG.
As shown in FIG. 2B, an absorber 1a 'or 1a "having a film thickness varying from row to row is formed on the array sensor 1 so as to cover the second row L2 or the third row L3 of the array sensor 1. In this case, it is possible to selectively use three or more types of counting sensors of low, medium, and high for each pixel of the image.

In the above example, the array sensor 1 has four rows and a plurality of columns, but the number of rows is arbitrary, and the present invention can be implemented as long as the line sensor has at least two rows. Further, the present invention is applicable not only to an apparatus that obtains an image by scanning a line sensor, but also to an imaging apparatus that obtains an image using a surface sensor array. The embodiment will be described with reference to FIG.

First, the surface sensor array 11 has a large number of radiation sensors S,... S arranged in a matrix, and is used while being fixed to a radiation source (not shown). This surface sensor array 11 has four sensors S...
S constitutes one pixel P of the image, and among the four sensors S, an absorber 11a equivalent to the previous embodiment is provided on the incident surface of one of the sensors S (the hatched sensor in the figure).
Are formed.

In this embodiment, pixel data is obtained by the same arithmetic processing as in the previous embodiment. That is, the count value based on the output of the sensor S forming the absorber 11a is compared with the reference value Th, and for the pixel P whose comparison result is equal to or more than the reference value Th, the count value based on the output of the sensor S having the absorber is provided. Are used as pixel data. When the comparison result is equal to or less than the reference value Th, 1
Pixel data is calculated from count values based on the outputs of the four sensors S constituting the pixel P.

In this example, the number of sensors constituting one pixel P is four, but the number is arbitrary and the present invention can be implemented if one pixel is constituted by at least two sensors. is there.

FIG. 5 is a diagram showing the configuration of another embodiment of the present invention. What is notable in this embodiment is that imaging is performed with the absorber 101a disposed above the array sensor 101.

The absorber 101a has a structure in which the array sensor 101 can be moved in the row direction by an adjustment mechanism (not shown). In the state shown in FIG. The sensor S constituting the second row L2 is arranged at a position covering the incident surface of the sensor SS. The absorber 101a is scanned stepwise by the scanning means 102 in the direction of the arrow in FIG.

Also in this example, as in the embodiment shown in FIG. 1, the output of each sensor S of the array-like sensor 101 is introduced into a counting circuit 103, respectively. The output of 103 is taken into the arithmetic processing unit 104. The output (count value) of the counting circuit 103 connected to the first row L1 of the array sensor 1 among these counting circuits is compared with the reference value Th by the comparing unit 105.
Based on the comparison result, the arithmetic processing unit 104 obtains and outputs pixel data by an operation equivalent to the above.

However, in this example, the absorber 101a
, The attenuation of the radiation incident on the sensor S in the first row L1 can be adjusted, so that the reference value Th set in the comparison unit 105 is changed according to the adjustment amount of the attenuation.
In addition, the absorber 101a is connected to the sensor S on the second line L2 and thereafter.
In this case, the count value based on the sensor output is corrected using the dose attenuation by the absorber 101a.

The absorber 101 used in this example
Since a is a single product and requires a certain degree of strength, Cu or the like is suitable as a material. Also, the absorber 101
When a is made of Cu and the thickness is about 0.4 mm,
For example, it has been confirmed at present that radiation having an intensity of about 140 KV can be attenuated to about 50%.

Furthermore, in this example, the wedge-shaped absorber 1
Although 01a is used, the shape is arbitrary, and for example, the present invention can be implemented even with a flat plate. However, using a wedge-shaped absorber is advantageous in the following points.

That is, by making the absorber a wedge shape and a tip portion having a blade shape as shown in FIG. 5, the tip of the absorber is exactly aligned with the boundary line between the sensor rows at the time of alignment with the array sensor 101. Even if it does not do so, there is almost no effect on the amount of radiation incident on the sensors on both sides of the boundary, so that the position adjustment of the absorber is simplified, and the limit incident amount that causes saturation by changing the position of the absorber This is advantageous in that it can be adjusted arbitrarily and smoothly.

Here, comparing the embodiment of FIG. 1 with the embodiment of FIG. 5, in the structure of FIG. 1, the absorber 1a is formed directly on the incident surface of the sensor S by the semiconductor processing technique. 1a, the position accuracy with respect to each sensor is high and the film thickness is uniform, so that the detection accuracy is excellent. In addition, since the absorber 1a is formed on the array sensor 1 itself, the array sensor 1 There is an advantage that no displacement occurs between the motor and the absorber 1a. On the other hand, in the structure of FIG. 5, in addition to the point that the limit incident amount that causes saturation can be arbitrarily adjusted as described above,
There is an advantage that an existing one can be used as 1.

The present invention is not limited to a radiation imaging apparatus,
The present invention is also applicable to an imaging device that counts photons of light and obtains an image based on the count value.

[0033]

As described above, according to the image pickup apparatus of the present invention, an absorber is provided in a sensor at a predetermined position of the array sensor, and one pixel for forming an image is formed by the sensor with or without the absorber. For each pixel detected and the photon count value based on the output of the sensor with the absorber becomes equal to or more than the reference value, the count value obtained by the sensor with the absorber is used as the pixel data. The high count area that cannot be detected by the sensor (without absorber) can be covered by the sensor with absorber. As a result, a high-quality image with a wide dynamic range without influence of saturation can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of the present invention.

FIG. 3 is a diagram showing a modified example of an absorber formed in the array sensor 1 according to the embodiment of the present invention.

FIG. 4 is an explanatory view of another embodiment of the present invention, showing the structure of the surface sensor array 11.

FIG. 5 is a configuration diagram of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Array sensor S * S radiation sensor 1a Absorber 2 Scanning means 3 * 3 Counting circuit 4 Arithmetic processing part 5 Comparison part 6 Image memory 7 Display device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01T 1/06 G01T 1/20 G01T 1/24 G01T 7/00

Claims (1)

(57) [Claims] 1. A method for detecting radiation or light containing information on a subject using an array sensor in which sensors that generate pulse-like electric signals in response to incidence of photons of radiation or light are arranged one-dimensionally or two-dimensionally. Then, in a device that obtains a photon count value of each pixel from the detection result and obtains an image in which the count value is used as a pixel density, among a plurality of sensors arranged in the array-like sensor, a sensor at a predetermined position is incident. On the surface, an absorber for reducing the amount of photons incident on the sensor is provided, and one pixel forming an image is configured to be detected by each of the sensors with and without the absorber. Data processing means for taking the photon count value based on the output, and comparison means for comparing the photon count value based on the sensor output with the absorber with a reference value. An image pickup apparatus characterized in that the data processing means outputs, as pixel data, only a count value based on the output of the sensor provided with the absorber for a pixel whose comparison result is equal to or greater than a reference value.