JP2001022016A - Radiograph information reading method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain addition image data without enlarging circuit scale for filtering processing in a double-sided condensing type radiograph information reading method and its device. SOLUTION: In this reading method, the filtering processing is performed to surface image data D1 by a front surface filtering processing circuit 41a, and the filtering processing is performed to back surface image data D2 by a back surface filtering processing circuit 41b. Next, two image data D1' and D2' to which the filtering processing is performed are inputted in an addition arithmetic circuit 42, where addition arithmetic processing, that is, Da=α×D1'β×D2' is performed to the data D1' and D2' so as to generate the addition image data Da showing the superimposed image. Thereafter, the data Da is inputted in a standardization processing circuit 43, where standardization processing is performed to the data Da. Thus, one standardization processing circuit 43 has only to be provided, so that circuit scale for standardization processing is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for irradiating a stimulable phosphor sheet on which radiation image information is stored with excitation light,
A so-called double-sided condensed radiation image information is obtained in which two image signals are obtained by detecting the stimulated emission light emitted from both sides of the stimulable phosphor sheet, and an added image is obtained using the two image signals. The present invention relates to a reading method and an apparatus.

[0002]

2. Description of the Related Art Conventionally, a radiation image of a subject recorded on a stimulable phosphor sheet is read to obtain image data.
After performing predetermined image processing on this image data, the image is converted to C
Displaying on an image display device such as an RT display or outputting to a film by a printer such as an LP (laser printer) is performed in various fields such as a medical field, and as a device for reading the radiation image, for example, 2. Description of the Related Art A CR (Computed Radiography) device using digital image processing technology in combination with a computer is used.

[0003] Here, the CR device means that 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, the CR device shines in accordance with the accumulated radiation energy. A stimulable phosphor (stimulable phosphor sheet) that emits light is used to temporarily store radiation image information of a subject such as a human body in a sheet form (a stimulable phosphor sheet).
The stimulable phosphor sheet is scanned with excitation light to generate stimulated emission light, and the generated stimulated emission light is photoelectrically read by a photoelectric reading unit such as a photomultiplier to obtain an image signal. In recent years, it means an image recording / reading apparatus, which has been widely used and put into practical use (for example, Japanese Patent Application Laid-Open Nos. 55-12429, 56-11395, 55-163472, 55-163472, and 55-163472 by the present applicant).
56-104645 and 55-116340).

In addition, as a method of photoelectrically reading the stimulated emission light, the applicant of the present application arranges the above-mentioned photoelectric reading means on both sides of the stimulable phosphor sheet so that both sides of the stimulable phosphor sheet or There has been proposed a double-sided condensing type reading method in which excitation light is scanned only on one side and stimulated emission light generated by the excitation light scanning is photoelectrically read from both sides of the stimulable phosphor sheet (for example, see Japanese Patent Application Laid-Open No. H11-157556). Kaisho 55-87970, JP-A-8-11
No. 6435). 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 a stimulable phosphor sheet on which a radiation image is accumulated and recorded on a transparent holder. , And photoelectric reading means are arranged above and below. 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 front side image signal and the back side image signal read from both sides in this way are respectively subjected to an addition operation for each corresponding pixel to obtain an added image signal (superimposed image signal).

When performing the addition operation, a two-dimensional matrix of a predetermined size (for example, 7 × 7; common to both sides) is used for each of the front side image signal and the back side image signal, and weighting coefficients (parameters for the front and rear sides) are separately set. In general, an addition operation is performed on a signal that has been subjected to filter processing (filtering processing) by a mask operation using ()).

According to the added image signal thus obtained, the high-frequency noise, which has been randomly generated in each of the front and back image signals, is smoothed by the addition operation.
Further, since the stimulated emission light is condensed from both sides of the stimulable phosphor sheet, the light condensing efficiency is improved, and the superimposed image displayed based on the added image signal has an S / N ratio. The image is improved and easy to see.

On the other hand, irrespective of whether it is a double-sided condensing type or a normal single-sided condensing type, the density, gradation and the like of the image signal acquired by the photoelectric reading means are within a predetermined range. That is, a so-called normalization process (EDR process) is performed.

Here, in the conventional double-sided condensing type reading method, when obtaining the added image signal subjected to the standardization processing, the filter processing is applied to each of the front and back image signals, and the filter processing is performed. By performing the normalization process separately on each of the processed image signals, and performing an addition operation using each of the image signals subjected to the normalization process,
As a result, an added image signal subjected to the normalization processing is obtained.

[0010]

However, when obtaining an added image signal that has been subjected to normalization processing, if the normalization processing is performed separately for each of the front and back sides as described above,
Two circuits for normalization processing are required separately for the front side and the back side, and there is a problem that the circuit scale is increased accordingly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and employs a double-sided condensing type to obtain an added image signal that has been subjected to filter processing and normalization processing. It is an object of the present invention to provide a radiation image information reading method and apparatus capable of reducing the scale.

[0012]

According to the present invention, there is provided a radiation image information reading method for detecting photostimulated light emitted from both sides of a stimulable phosphor sheet on which radiation image information is stored by irradiation with excitation light. A radiographic image information reading method for obtaining two image signals carrying radiographic image information, and obtaining, based on the two image signals, an added image signal subjected to a filtering process and a normalizing process. Filter processing is performed on each of the two image signals, an addition operation is performed using the two image signals that have been subjected to the filter processing to obtain an addition image signal, and then the addition image signal is standardized. This is characterized in that a normalization process is performed. In short, the normalization process is performed after the addition operation.

Further, the radiation image information reading apparatus according to the present invention is an apparatus for realizing the above method, that is, stimulated emission emitted from both sides of a stimulable phosphor sheet on which radiation image information is accumulated and recorded by irradiation of excitation light. Image signal obtaining means for obtaining two image signals carrying radiation image information by detecting light, respectively, and generating an added image signal which has been subjected to a filtering process and a normalizing process based on the two image signals; A radiation image information reading apparatus comprising: an addition image signal generation unit, wherein the addition image signal generation unit performs a filtering process on each of two image signals separately, and the filtering process is performed. An addition operation unit that performs an addition operation using the latter two image signals to obtain an addition image signal, and a normalization processing unit that performs a normalization process on the addition image signal. It is characterized in that the.

[0014]

According to the radiation image information reading method and apparatus of the present invention, after performing an addition operation using two image signals that have been subjected to a filtering process, a normalization process is performed on the added image signal. Thus, it is sufficient to provide one circuit for normalization processing, and as a result, the circuit scale for normalization processing can be reduced.

[0015]

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

FIG. 1 is a schematic diagram of a double-sided condensing type radiation image information reading apparatus according to an embodiment of the present invention. FIG. 2 is a circuit block diagram focusing on signal processing of the radiation image information reading apparatus. FIG. 2 is a circuit block diagram focusing on an added image signal generation unit in a conventional double-sided condensing type radiation image information reading apparatus.

As shown in FIG. 1, in the radiation image information reading apparatus 1, a stimulable phosphor sheet (hereinafter simply referred to as a sheet) 1 is placed on endless belts 9a and 9b which are rotated by a motor (not shown). Be placed.
In a state where the sheet 1 is arranged on the endless belts 9a and 9b, a laser light source 10 for emitting a light beam 11 as excitation light,
1 is a rotary polygon mirror that is driven to rotate by a motor (not shown) to perform main scanning on the sheet 1 and a scanning lens that converges the reflected and deflected light beam 11 on the sheet 1 and scans the sheet 1 at a constant speed. 19 are arranged. Further, above the position where the light beam 11 is scanned, a condensing guide 24a that condenses the photostimulated light emitted from the scanning of the light beam 11 from above is disposed in close proximity, and below the position. The light condensing guide 24b for condensing stimulated emission light from below is arranged perpendicular to the sheet 1. Photomultipliers (photomultiplier tubes) 25a and 25b, which photoelectrically detect stimulated emission light, are connected to the condensing guides 24a and 24b, respectively. In addition, the light collection guides 24a, 2
4b and the photomultipliers 25a and 25b constitute an image signal acquiring unit according to the present invention.

As shown in FIG. 2, the output of the photomultiplier 25a is connected to a log amplifier (logarithmic amplifier) 31a.
The output of the og amplifier 31a is the aliasing filter 32a.
And the output of the aliasing filter 32a is A /
It is connected to the D converter 33a. Similarly, the output of the photomultiplier 25b is connected to the log amplifier 31b,
The output of the amplifier 31b is connected to the aliasing filter 32b, and the output of the aliasing filter 32b is connected to the A / D converter 33b.

The outputs of the A / D converters 33a and 33b are:
It is connected to an addition image signal generation means 40 having a filter processing circuit 41, an addition operation circuit 42 and a normalization processing circuit 43. That is, the output of the A / D converter 33a is connected to the surface filter processing circuit 41a, and the A / D converter 33b
Are connected to the backside filter processing circuit 41b. As is clear from this, the surface filtering circuit 4
The filter processing circuit 41 composed of 1a and the back surface filter processing circuit 41b is considered as a filter processing unit according to the present invention, which performs filter processing separately on two image signals of the front surface and the back surface.

Here, in a conventional double-sided condensing type radiation image information reading apparatus to which the present invention is not applied, as shown in FIG. 3, the output of the surface filter processing circuit 41a is connected to the surface normalization processing circuit 44a. The output of the back side filter processing circuit 41b is connected to the back side normalization processing circuit 44b,
The outputs of the two normalization processing circuits 44a and 44b are connected to the addition operation circuit 42, and a circuit for the normalization processing is required on each of the front surface and the back surface.

On the other hand, in the radiation image information reading apparatus 1 to which the present invention is applied, as shown in FIG. 2, both outputs of the filter processing circuits 41a and 41b are connected to the addition operation circuit 42, and the output of the addition operation section 42 Are connected to the standardization processing circuit 43.

To obtain a radiation image signal using the radiation image information reading apparatus 1, first, a sheet 1 on which a radiation image of a subject is accumulated and recorded is set on an endless belt 9a and conveyed in the direction of arrow Y. (Sub-scanning), and moves to the endless belt 9b side. On the other hand, a light beam 11 emitted from the laser light source 10 is driven by a motor (not shown) and rotates at a high speed in a direction indicated by an arrow.
The main scanning is performed in the direction of arrow X substantially perpendicular to the sub-scanning direction (direction of arrow Y). From the portion of the sheet 1 irradiated with the light beam 11, the stimulated emission light 13a is emitted from the upper side of the sheet 1 and the stimulated emission light is emitted from the lower side of the sheet 1 according to the stored and recorded radiation image information. 13b are respectively emitted.

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 24a, and the incident stimulated emission light 13a travels inside the condensing guide 24a by repeating total reflection. , The photostimulable emission light 13a emitted from the emission end face and received by the photomultiplier 25a 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 24b,
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 25a is supplied to a log amplifier 31a and an aliasing filter 3.
2a, sequentially input to the A / D converter 33a, and finally the electric signal S _A is converted into digital surface image data D1 by the A / D converter 33a, and the surface filter processing circuit 4
1a. Similarly, the electric signal S _B outputted from the photomultiplier 25b, log amplifier 31b, aliasing filter 32b, are sequentially input to the A / D converter 33b, and finally the electric signal S _B is A / D converter The data is converted into digital backside image data D2 by 33b and input to the backside filter processing circuit 41b.

Next, when obtaining the added image data Da which has been subjected to the filtering process and the normalizing process, first, in the surface filter processing circuit 41a to which the surface image data D1 has been input, 7 A filter process is performed by a mask operation using a predetermined weighting coefficient while using a × 7 two-dimensional matrix. Similarly, the back side filter processing circuit 41 to which the back side image data D2 is input
In step b, a 7 × 7 two-dimensional matrix is used for the back side image data D2 as in the front side, and a filtering process is performed by a mask operation using a predetermined weighting coefficient. Here, the filter processing is not limited to the above example, and any known processing method may be used.

Since the signal characteristics of the front side image data D1 and the back side image data D2 generally have some differences, different values are used as the weighting coefficients for each side. Therefore, for added image data obtained by performing an addition operation on two data that have not been subjected to the filtering process,
It is difficult to apply the filter processing for both the front side and the back side at once, and conversely, applying the filter processing to the added image data at once causes a problem.

The two image data D1 'and D2' which have been subjected to the filter processing in this manner are added to the addition operation circuit 42.
, And is subjected to the addition arithmetic processing of Da = α × D1 ′ + β × D2 ′ (1) to generate addition image data Da representing a superimposed image.

Next, the added image data Da is input to the normalization processing circuit 43, and is subjected to normalization processing (EDR processing) so that the density, gradation and the like fall within a predetermined range. As the normalization processing here, any normalization processing may be performed as long as linear processing having similar characteristics is performed on both the front surface and the back surface. In this normalization process, it is preferable to use a method of converting input pixel data with reference to a conversion table prepared in advance. Thus, for the added image data Da,
Even if the normalization process for the front surface and the back surface is performed at once, linear processing having the same characteristics can be used for each surface, so that there is no problem unlike the above-described filter processing.

The added image data Db subjected to the normalization processing
Is input to an image processing circuit (not shown) and is subjected to predetermined image processing, and then is input to an image output unit (not shown) such as a CRT display to output a visible image.

As described above in detail, in the method and apparatus for reading radiation image information of the double-sided condensing type according to the present invention, normalization processing is performed on the added image data Da. Whereas the conventional one required two normalization processing circuits 36a and 36b,
By applying the present invention, one standardization processing circuit 43
Only needs to be provided, and the circuit scale for the standardization processing can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a double-sided condensing type radiation image information reading apparatus according to the present invention.

FIG. 2 is a circuit block diagram focusing on signal processing of the radiation image information reading apparatus according to the present invention.

FIG. 3 is a circuit block diagram focusing on an added image signal generating unit in a conventional radiation image information reading apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Radiation image information reading apparatus 10 Laser light source 12 Rotating polygon mirror 19 Scanning lens 24a Condensing guide 24b Condensing guide 25a Photomulti 25b Photomulti 40 Addition image signal generation means 41 Filter processing circuit 41a Surface filter processing circuit 41b Surface filter processing circuit 42 addition arithmetic circuit 43 normalization processing circuit

Claims (2)

[Claims] 1. An image signal carrying radiation image information by detecting stimulated emission light emitted from both sides of a stimulable phosphor sheet on which radiation image information is accumulated and recorded by irradiation of excitation light. A radiographic image information reading method for obtaining an added image signal subjected to a filtering process and a normalization process based on the two image signals, wherein the filtering process is performed on each of the two image signals, A radiation image information reading unit that performs an addition operation using the two image signals subjected to the filter processing to obtain the added image signal, and thereafter performs the normalization process on the added image signal; Method. 2. An image signal carrying radiation image information by detecting stimulated emission light emitted from both sides of a stimulable phosphor sheet on which radiation image information is accumulated and recorded by irradiation of excitation light. A radiation image information reading apparatus, comprising: an image signal acquiring unit that obtains an image signal; and an addition image signal generation unit that generates an addition image signal on which a filtering process and a normalization process are performed based on the two image signals. A filter processing unit configured to perform the filtering process separately on the two image signals,
The image processing apparatus further includes an addition operation unit that performs an addition operation using the two image signals that have been subjected to the filter processing to obtain the added image signal, and a normalization processing unit that performs the normalization processing on the added image signal. A radiation image information reading apparatus, comprising: