JP2002148737A - Superposed image forming method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain added images of high image quality of a superposed image former used for a radiation image information reader of a both side beam condensing type. SOLUTION: The bit width N1 of front surface image data D11 and rear surface image data D12 digitalized in an analog-to-digital conversion section 140 and the bit width N3 of added image data D3 outputted from an addition arithmetic section 150 and inputted to a standardization means 400 are equaled to each other and the bit width Ny of data D4 outputted from the standardization means 400 is decreased by one bit. The bit width N2 of the image data is made wider by at least >=2 bits than the bit width N3 of the added image data by bit resolution improving means 151 and 153 (N2>=n3+2). The accurate processing of the bit resolution of the image data input to filter processing means 152 and 154 and adder means 155 to the bit higher by >=2 bits than the bit resolution of the added image data D3 is made possible and the added images of the high quality may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a superimposed image generating method and apparatus used for a double-sided condensing type image information reading apparatus, for example.

[0002]

2. Description of the Related Art When radiation is irradiated, a part of the radiation energy is accumulated, and thereafter, when irradiated with excitation light such as visible light or infrared light, a stimulable light having a photostimulable emission according to the accumulated radiation energy. Using a phosphor (stimulable phosphor), a stimulable phosphor sheet (sheet-shaped stimulable phosphor) on which radiation image information of a subject such as a human body is recorded is scanned with excitation light to emit stimulable light. A CR (Computed Radiography) device that generates light and obtains an image signal by photoelectrically reading the generated photostimulated light by a photoelectric reading unit such as a photomultiplier is widely used as an image information reading device that forms a diagnostic image or the like. However, it is used for diagnosis at medical sites (for example, Japanese Patent Application Laid-Open Nos. 55-12429 and 56-11395 by the present applicant).
No. 55-163472, No. 56-104645, No. 55-116340).

In addition, as a method for photoelectrically reading the stimulated emission light, the present applicant disposes the above-mentioned photoelectric reading means on both sides of the stimulable phosphor sheet, and applies the photoelectric reading means on both sides of the stimulable phosphor sheet. A double-sided condensing reading method has been proposed in which one side is scanned with excitation light, and the stimulated emission light emitted by the scanning of the excitation light is photoelectrically read from both sides of the stimulable phosphor sheet (for example, Japanese Patent Application Laid-Open No. Sho 55-55). -87970, JP-A-8-116435, etc.).

In this double-sided condensing reading method, a stimulable phosphor sheet is formed by laminating a stimulable phosphor on the surface of a transparent support, and the stimulable phosphor sheet has a radiation image accumulated and recorded on a transparent holder. A phosphor sheet is mounted, and photoelectric reading means are arranged above and below the phosphor sheet. That is, the photoelectric reading means arranged above the holder reads the stimulated emission light emitted from the front surface of the stimulable phosphor sheet, and the photoelectric reading means arranged below the holder reads the back side of the stimulable phosphor sheet. The stimulating light emitted from the device is read.

[0005] The image signals (front image signal and back image signal) read from each surface in this manner are added up for each corresponding pixel to obtain an added image signal carrying a superimposed image. According to the added image signal, the high-frequency noise, which has been randomly generated in each of the front and back image signals, is smoothed by the addition operation, and the stimulated emission light is condensed from both surfaces of the stimulable phosphor sheet. Therefore, the light-collecting efficiency is improved, and the superimposed image displayed based on the added image signal has an improved S / N ratio and is easy to view.

[0006] Hereinafter, a CR device that performs the double-sided condensing reading method is referred to as a double-sided condensing type CR device, which scans one surface of a stimulable phosphor sheet with excitation light, and emits light by the excitation light scanning. The device that photoelectrically reads the stimulated emission light from only one side of the stimulable phosphor sheet is a single-sided condensing type CR.
It is called a device.

On the other hand, regardless of the single-sided condensing type or the double-sided condensing type, in the process of reading image information recorded on the stimulable phosphor sheet, performing desired image processing, and outputting it as a visible image, At the stage of reading the stimulated emission light to obtain the acquired image data, a wide recording range of the radiation image is read with high resolution, in other words, the data bit width N
1 is read, and the data range corresponding to the desired reading range of the X-ray irradiation amount is converted into data of lower resolution than at the time of reading by using a look-up table or the like with respect to the acquired image data having a wide bit width. In other words, a normalization process for making the bit width Ny smaller than the bit width N1 of the acquired image data (EDR process;
In general, image processing is performed on the processed image data having a small bit width that has been subjected to the standardization processing.

For example, the handling of the bit resolution or bit width of image data in a single-sided condensing type CR device is based on the bit width N of acquired image data before normalization processing.
1 is 11 bits, and the bit width Ny after the normalization processing is 10 bits (N1 = Ny + 1).

On the other hand, in the case of a double-sided condensing type CR device, in order to simplify the circuit configuration, preprocessing for addition operation is performed on each of the acquired image data on each surface, and then addition processing is performed. In general, it is configured to obtain added image data (superimposed image data) before the conversion process and to perform a normalization process on the added image data. In this case, if the same concept of the single-sided condensing type is applied as it is to the handling of the bit width of the image data, the bit width N1 of the acquired image data of each surface is 11 bits, and the bit width N2 after the pre-processing for the addition operation is The bit width N3 from 11 bits, after the addition processing to before the normalization processing is also 11 bits, and the bit width Ny after the normalization processing is 10 bits (N1 = N2 = N3 = Ny + 1).

[0010]

However, in this case, the bit width from read to immediately after the addition operation or immediately before the normalization processing is N1 = N2 = N3, and various bit widths before the addition operation such as the preprocessing for the addition operation are obtained. Data accuracy may decrease in data processing and the like. In addition, since the input and output of the addition operation have the same bit width, overflow may cause so-called digit loss and data accuracy may be reduced. As a result, there arises a problem that the quality of the finally obtained superposed image is deteriorated.

The present invention has been made in view of the above circumstances, and provides a superimposed image having a good S / N and a high image quality by defining a bit width from reading to after addition. It is an object of the present invention to provide a superimposed image generating method and apparatus which can be used.

[0012]

According to the present invention, there is provided a superimposed image generating method for adding two image data for each corresponding pixel to obtain superimposed image data carrying an superimposed image. The addition is performed using two pieces of image data having a bit resolution higher than the desired bit resolution of the added image data by two bits or more to generate added image data having a desired bit resolution. is there.

[0013] In other words, the bit width N2 of the two image data before addition is set to be two times larger than the bit width N3 of the added image data.
The number of bits is made larger than that, that is, N2 ≧ N3 + 2.

Here, to make the bit width N2 of the two pieces of image data before the addition larger than the bit width N3 of the added image data after the addition by two bits or more is, in short, desired (finally required). ) Bit width N of added image data
That is, the addition is performed using data having a bit width wider than 2 by 2 bits, that is, data having a higher resolution than 2 bits, and then adding image data having a desired bit width N2 is output.

In general addition processing, since the data width of input and output is increased by the same bit width or carry, it is necessary to reduce the bit resolution after addition, that is, to reduce the bit width. Instead, it is also possible to use a method of performing a process of reducing the bit resolution of the added image data to a desired bit resolution in the addition process in parallel.

In general, the bit width N1 of the data immediately after reading and the bit width N3 of the superimposed image data after the addition operation are set to be the same. In this case, the addition is performed after the reading. The process of expanding the bit width N2 in the process before the operation by 2 bits or more than the bit width N1 of the acquired image data is performed in advance.

Further, in the superimposed image generating method of the present invention, when a predetermined pre-processing is performed prior to the addition, and the addition is performed using the two image data after the pre-processing, the addition is performed. It is desirable to perform preprocessing on two image data having a bit resolution higher than the desired bit resolution of the image data by at least two bits.

In this case, generally, the two image data after the pre-processing (processed data) also have a bit resolution higher than the desired bit resolution by two bits or more. What is necessary is just to use it as it is and to perform addition.

On the other hand, when it is not necessary to perform any processing on the data immediately after reading before the addition operation, the bit width of the data immediately after reading is at least two bits larger than the bit width N3 of the added image data after the addition operation. In some cases, the addition may be performed using the data immediately after the reading as it is.

[0020] The superimposed image generating apparatus of the present invention comprises: image data acquiring means for acquiring two image data having a bit resolution higher than a desired bit resolution by at least two bits;
Adding means for receiving two image data, adding the two image data for each corresponding pixel, and superimposing to obtain added image data having a bit resolution higher than the desired bit resolution for carrying an image by two bits or more; And a bit resolution reducing means for reducing the bit resolution of the added image data output from the adding means to the desired bit resolution.

In the superimposed image generating apparatus of the present invention,
A predetermined pre-process is performed on the input image data between the image data acquisition unit and the addition unit, and two processed image data having a bit resolution higher than the desired bit resolution by 2 bits or more are added. The means may be provided with a pre-processing means.

The two image data may be obtained in any way as long as they are used to obtain an image by adding and superimposing. For example, the stimulable emission light emitted from each surface of the stimulable phosphor sheet by scanning the stimulable phosphor sheet with the excitation light is obtained by using the double-sided condensing type CR device, that is, Those obtained by photoelectrically reading can be used. Of course, the present invention is not limited to this, and two image data read separately from each other using a single-sided condensing type CR device may be used.

[0023]

According to the superimposed image generating method and apparatus of the present invention, the addition is performed by using two image data having a bit resolution higher than the desired bit resolution of the added image data by two bits or more. Since the addition image data having the bit resolution of is generated, the finally required data accuracy can be secured in the addition stage. Further, since the bit width on the input side of the addition is made at least two bits larger than the bit width on the output side, even if the least significant bit of the data before the addition includes an error component, the effect can be almost avoided. Thereby, a high-quality added image can be obtained.

The bit width is widened and the amount of signal wiring is increased. However, if a circuit is constituted by a DSP (digital signal processor) or an FPGA (field programmable gate array), hardware resources such as an IC will increase significantly. Since it is not provided, a compact circuit configuration can be adopted.

Also, in the case where a predetermined pre-process is performed prior to the addition and the addition is performed using the two image data subjected to the pre-processing, the required bit resolution of the added image data is also increased by two. If preprocessing is performed on two image data having a bit resolution higher than a bit, data accuracy can be improved even in the preprocessing stage, and finally required data accuracy is secured. be able to.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a configuration example of a double-sided condensing type radiation image information reading apparatus including an addition operation section which is an embodiment of the superimposed image generation apparatus of the present invention, and FIG. A reading unit (scanner unit) that functions as an excitation light scanning unit and an image signal acquiring unit in the information reading device.
FIG. 3 is a schematic diagram showing the configuration of FIG.

As shown in FIG. 2, a reading unit 1 of a double-sided condensing type
, The stimulable phosphor sheet 1 is rotated by a motor (not shown).
b. Above the sheet 1, a laser light source 10 that emits a light beam 11 as excitation light, a rotary polygon mirror 12 that reflects and deflects the light beam 11 and is rotated by a motor (not shown) that scans the sheet 1 in a main direction and a reflection mirror A scanning lens 19 for converging the deflected light beam 11 on the sheet 1 and scanning at a constant speed is provided. Further, above the position where the light beam 11 is scanned, a condensing guide 14a that condenses stimulated emission light emitted by the scanning of the light beam 11 from above is disposed in close proximity, and below the position. The light condensing guide 14b for condensing stimulated emission light from below is arranged perpendicular to the sheet 1. Photomultipliers (photomultiplier tubes) 15a and 15b for photoelectrically detecting stimulated emission light are respectively connected to the light collection guides 14a and 14b. This Photo Mar 15
a and 15b are corresponding logarithmic amplifiers 16a and 16b, respectively.
b.

The excitation light scanning means 110 is constituted by the endless belts 9a and 9b, the laser light source 10, the rotary polygon mirror 12, the scanning lens 19 and the like. The image signal acquiring means 130 is constituted by the light collecting guides 14a and 14b, the photomultipliers 15a and 15b, and the logarithmic amplifiers 16a and 16b.

As shown in FIG. 1, the radiation image information reading apparatus 100 includes an excitation light scanning means 110 for scanning the stimulable phosphor sheet 1 with a light beam 11 as excitation light, and the scanning causes each surface of the sheet 1 to be scanned. Stimulated light 13 emitted from
image signal obtaining means 130 for obtaining two image signals by photoelectrically reading a and 13b, an A / D converter 140 for digitizing the two image signals to obtain two image data; An addition operation unit 140 as a superimposed image generating apparatus of the present invention for obtaining superimposed image data D3 by performing an addition operation for each corresponding pixel of two image data, and performing a normalization process on the superimposed image data D3 And a normalization processing means 400 for performing the processing.

In such a configuration, when obtaining a radiation image signal, first, the stimulable phosphor sheet 1 on which the radiation image of the subject is accumulated is recorded by the endless belt 9.
a, 9b are set at predetermined positions. The stimulable phosphor sheet 1 set at this predetermined position is conveyed (sub-scan) in the direction of arrow Y by the endless belts 9a and 9b. On the other hand, the light beam 11 emitted from the laser light source 10
Is reflected and deflected by a rotary polygon mirror 12 driven by a motor (not shown) and rotated at a high speed in the direction of the arrow, enters the sheet 1 and performs main scanning in an arrow X direction substantially perpendicular to the sub-scanning direction (arrow Y direction). Sheet 1 irradiated with this light beam 11
The stimulating light 13a is emitted from the upper side of the sheet 1 and the stimulating light 13b is emitted from the lower side of the sheet 1 in accordance with the radiation image information stored and recorded from the location of.

The stimulated emission light 13a emitted from the upper side of the sheet 1 is incident on the incident end face of the condensing guide 14a, and the incident stimulated emission light 13a travels inside the condensing guide 14a by repeating total reflection. Stimulable emission light 13a emitted from the emission end face and received by the photomultiplier 15a and representing a radiation image
Is converted into an analog electric signal S _A corresponding to the amount of light.
Similarly, photostimulated light 13 emitted from the lower side of sheet 1
b is guided by the condensing guide 14b,
b, photoelectrically detected by an analog electric signal S _B
Is converted to As a result, two image signals carrying a radiation image are obtained.

The electric signal S _A output from the photomultiplier 15a and the electric signal S output from the photomultiplier 15b
_B is input to the corresponding logarithmic amplifiers 16a and 16b, where the electric signal S _A is converted into an image signal S1 and the electric signal S _B is converted into an image signal S2. Hereinafter, an image signal S1 based on the stimulated emission light 13a emitted from the upper side of the sheet 1 is referred to as a front image signal S1, and an image signal S2 based on the stimulated emission light 13b emitted from the lower side of the sheet 1 is referred to as a lower back image. This is called signal S2.

The front side image signal S1 and the back side image signal S2 are
After being input to the A / D conversion unit 140, the addition operation unit 150
And the addition operation is performed by the addition operation unit 150 to obtain the added image data D3 as the operation-completed image signal.

As shown in FIG. 1, the addition operation unit 150 here has an A / D converter for the surface of the A / D conversion unit 140.
Bit resolution improving means 151 for converting the surface image data D11 digitized by the D converter 141 into image data D21 having a bit resolution higher than a desired bit resolution by 2 bits or more, and a filter for the image data D21 by a mask operation A filtering means 152 for performing processing and inputting processed surface image data D22 having a bit resolution higher than the desired bit resolution by 2 bits or more to an adding means 155, an A / D converter 14 for the back side
Bit resolution improving means 153 for converting the back side image data D12 digitized by the step 2 into image data D23 having a bit resolution higher than a desired bit resolution by 2 bits or more, and performs a filtering process by a mask operation on the image data D23. A filtering means 154 for inputting the processed image data D24 having a bit resolution higher than the desired bit resolution by 2 bits or more to the adding means 155, and the processed surface image data D22 each having been subjected to a filtering process by a mask operation. Adding means 15 for performing an addition operation using the processed back side image data D24 and outputting added image data D25 having a bit resolution higher than the desired bit resolution by 2 bits or more.
5. Bit resolution reducing means 1 for reducing the bit resolution of the added image data D25 to the desired bit resolution and outputting the added image data D3 having the reduced bit resolution.
56. Bit resolution improving means 151, 15
Reference numeral 3 functions as an image data acquisition unit of the present invention, and filter processing units 152 and 154 function as preprocessing units of the present invention.

The addition means 155 performs an addition operation using the image data which has been subjected to the filter processing by the mask operation as preprocessing of the present invention. As the filter processing by the mask operation, for example, Japanese Patent Laid-Open No. 7-319092
As disclosed in the above publication, any known method such as a process of performing a wavelet transform on an image signal to obtain a coefficient signal for each frequency band may be used. It should be noted that JP-A-7-
In the case of using the method disclosed in No. 319092, the adding means 155 performs the addition operation using the optimal weighting coefficient for each of the front and back surfaces and for each frequency band, as described in the publication. I do.

The added image data D3 obtained by the addition operation unit 150 is output to a normalization processing unit 400 connected at the subsequent stage.
Is input to As the normalization processing in the normalization means 400, for example, as described in Japanese Patent Application Laid-Open No. 2-108175, a data range corresponding to a desired reading range of the X-ray irradiation amount is converted into a certain data range, and bit conversion is performed. A process for making the width Ny smaller than the bit width N1 of the acquired image data is performed. Then, after desired image processing such as frequency emphasis processing and gradation processing is performed, the processed added image data D
4 to output an image.

Next, the handling of the data bit width and the bit resolution in the radiation image information reading apparatus 100 having the above configuration will be described.

In this embodiment, the A / D converter 14
0, the bit width N1 of the front side image data D11 and the back side image data D12,
The bit width N3 of the added image data D3 output from the unit 50 and input to the normalization processing means 400 is made equal, that is, the bit resolution of the front image data D11 and the back image data D12 is made equal to the bit resolution of the added image data D3. , Data D4 output from the normalization processing means 400
Is reduced by one bit, that is, the bit resolution is reduced by one bit. Specifically, N1
= N3 = 11 bits and Ny = 10 bits.

The bit width N2 of the front side image data D22 and the back side image data D24, which are subjected to the filtering process by the filtering sections 152 and 154 of the addition operation section 150, is at least two bits larger than the bit width N3 of the addition image data D3. (N2 ≧ N3 +
2). More specifically, N2 is set to 13 bits or more by the bit resolution improving means 151 and 153 in accordance with N1 = N3 = 11 bits.

Thus, the filtering process and the addition operation are performed with a bit resolution of 13 bits or more.
By handling information with higher definition than in the case of 1 bit, highly accurate processing can be performed. As a result, the added image data 11 is converted to 11
Even if the bit resolution is reduced to the bit resolution, it is possible to obtain an added image with higher image quality than before.

On the other hand, the addition operation unit 150 having such a configuration is used.
Can be composed of, for example, a DSP or an FPGA, so that even if the bit width is increased, the hardware resources do not substantially increase.

In the above description, the filtering process and the addition operation are performed by using two image data (bit width 13 bit or more in the previous example) having a bit resolution higher by 2 bits or more than the bit resolution (bit width 11 bit in the previous example) of the added image data. ), But as long as such handling of the bit resolution or bit width is maintained as described above, for example, when no normalization processing is provided, or addition with the A / D conversion unit 140 is performed. A similar method can be adopted when a means for performing other processing is provided between the arithmetic unit 150 and the processing unit 150.

The bit width N1 of the front side image data D11 and the back side image data D12 is equal to the bit width N3 of the added image data D3.
1> N3. In this case, N1 is 13
Above, the A / D converter 140 substantially functions as the image data acquisition unit of the present invention.
The bit resolution improving means 151 and 153 may not be provided.

Further, as shown in FIG. 3, if addition processing section 150 has a configuration in which filter processing means 152 and 154 are removed, even when addition processing is performed without performing filter processing as preprocessing, The handling of the bit resolution or the bit width in the addition operation can be performed as described above, and similarly to the above-described embodiment, it is possible to obtain a higher-quality added image than in the related art.

In the above embodiment, the processed surface image data D22 having a bit resolution of 13 bits or more is used.
And directly adding the processed back side image data D24
5, but as shown in FIG. 4, both image data D22,
This does not exclude a configuration in which the bit resolution of D24 is once reduced to 11 bits, and then the resolution is increased to N2 (13 bits or more) by the bit resolution improving unit 158 before the image data is input to the adding unit 155. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of the configuration of a double-sided condensing type radiation image information reading apparatus including an addition operation section as a superimposed image generating apparatus according to the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of a reading unit of the radiation image information reading apparatus.

FIG. 3 is a diagram illustrating an example of a modification of an addition operation unit;

FIG. 4 is a diagram showing another example of a modification of the addition operation unit.

[Explanation of symbols]

 Reference Signs List 1 reading unit 100 superimposed image generating device 110 excitation light scanning unit 130 image signal acquisition unit 140 A / D conversion unit 150 addition operation unit 151 bit resolution improvement unit 152 filter processing unit 153 bit resolution improvement unit 154 filter processing unit 155 addition unit 156 bit resolution reduction means 400 standardization processing means

Claims (5)

[Claims] 1. A superimposed image generating method for adding two image data for each corresponding pixel to obtain superimposed image data carrying an superimposed image, wherein the bit resolution of the superimposed image data is set to be 2 or more than a desired bit resolution.
A superimposed image generation method, wherein the addition is performed using the two image data having a bit resolution higher than a bit, and the addition image data having the desired bit resolution is generated. 2. The superimposed image generating method according to claim 1, wherein a predetermined pre-processing is performed prior to the addition, and the addition is performed using the two image data subjected to the pre-processing. A superimposed image generating method, wherein the preprocessing is performed on two image data having a bit resolution higher than a desired bit resolution of the added image data by two bits or more. 3. An image data acquisition means for acquiring two image data having a bit resolution higher than a desired bit resolution by two bits or more, and a pixel corresponding to the input two image data and corresponding to the two image data. Adding means for obtaining added image data having a bit resolution higher by 2 bits or more than the desired bit resolution for carrying a superimposed image by adding the superimposed image, and the bit resolution of the added image data output from the adding means, A superimposed image generating apparatus comprising: a bit resolution reducing unit configured to reduce the bit resolution to a desired bit resolution. 4. A process in which a predetermined pre-process is performed on input image data between the image data acquiring unit and the adding unit, and a bit resolution higher by 2 bits or more than the desired bit resolution is provided. 4. A superimposed image generating apparatus according to claim 3, further comprising a pre-processing means for inputting the two already processed image data to said adding means. 5. The two image data are obtained by scanning a stimulable phosphor sheet with excitation light to photoelectrically read stimulated emission light emitted from each surface of the stimulable phosphor sheet. 5. A superimposed image generating apparatus according to claim 3, wherein