JPH07109482B2 - Radiation image information reading method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radiation image information reading method and apparatus for optically reading radiation image information, and more particularly to correction of a read image.

(Background of the Invention) Radiation images such as X-ray images are often used for disease diagnosis. In order to obtain this radiation image, the radiation that has passed through the subject is applied to the phosphor layer (fluorescent screen) to generate visible light, and this visible light is used in the same way as when taking a normal photo. A so-called radiograph is used in which a film coated with a silver salt photosensitive material is irradiated and developed. However, in recent years, a method for obtaining radiation image information without using a radiographic film made of a silver salt photosensitive material has been devised. As such a method, the radiation transmitted through the subject is absorbed by a certain type of phosphor,
Thereafter, by exciting this phosphor with, for example, light or heat energy, the phosphor emits the radiation energy accumulated by the absorption as fluorescence, and the fluorescence is detected and imaged. There is. Specific examples are disclosed in U.S. Pat. No. 3,859,527 and JP-A-55-12144. This shows a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as excitation light, using a radiation image conversion panel in which a stimulable phosphor layer is formed on a support. Then, the photostimulable phosphor layer of this radiation image conversion panel is irradiated with the radiation transmitted through the subject to accumulate the radiation energy corresponding to the radiation transmittance of each part of the subject to form a latent image. By scanning the exhaustive fluorescent material layer with the excitation light, the radiation energy accumulated in each part of the panel is radiated and converted into light, and the intensity of this light is increased by a photomultiplier tube, a photodiode, or the like. A radiation image is obtained by detection with a photoelectric conversion element.

FIG. 9 is an explanatory diagram of image recording on such a stimulable phosphor. In the figure, X-rays emitted from an X-ray source 1 are focused on by a diaphragm 2 and then irradiated on a subject 3. The X-rays that have passed through the subject 3 enter the photostimulable phosphor 4,
A latent image of the image of the subject 3 is formed on the photostimulable phosphor 4.

FIG. 10 is a configuration block diagram showing an example of a conventional radiation image information reading apparatus for reading a radiation image recorded on such a stimulable phosphor. Reference numeral 101 is a semiconductor laser light source for generating excitation light, and the semiconductor laser light source 101 is driven by a laser driver circuit 102 in a pulse form in synchronization with an image clock signal from an image clock generator 125. Pulsed laser beam L generated from semiconductor laser light source 101
B is a monochromatic light filter 103, a mirror 104, a beam shaping optical system 1
It reaches the deflector 107 via 05 and the mirror 106. The deflector 10
A galvanometer mirror 7 driven by a deflector driver 108 deflects the laser beam LB within the scanning region at a constant angle. The deflected laser beam LB receives the fθ lens 10
The radiation image conversion panel (hereinafter referred to as "image conversion panel") 111, which is adjusted to have a constant speed on the scanning line by means of 9 and uses a stimulable phosphor as a radiation image information recording medium through a mirror 110, is indicated by an arrow Scan in the direction of a. The image conversion panel 111 is simultaneously in the sub-scanning direction (direction of arrow b).
Then, the entire surface is scanned. The pulsed stimulated emission emitted from the image conversion panel 111, which is scanned by the laser beam LB, is condensed by the condenser 112, passes through the filter 113 that passes only the wavelength region of the stimulated emission, and a photomultiplier tube. It reaches the photodetector 114 equipped with and is converted into an analog electric signal (image signal).

Reference numeral 115 is a power source for supplying a high voltage to the photodetector 114 (photomultiplier tube). The image signal output as a current from the photodetector 114 is voltage-amplified through the preamplifier 116, and further, a logarithmic amplifier 118 for converting the emission intensity signal into an image density signal, a filter 119, and a signal in synchronization with the image clock signal. After passing through the sample hold circuit (I) 120 that maintains the
It is converted into a digital signal by the converter 121 and sent to an external data processing device via the interface 124.

(Problems to be Solved by the Invention) However, problems with such reading of radiation image information include uneven sensitivity (shading) of radiation and stimulable phosphors and changes with time of stimulable phosphors. However, there has been a correction technique described in Japanese Patent Application Laid-Open No. 60-234643 as a technique for dealing with this problem.

However, in the technique described in the above publication, the correction data for correcting the read data must be prepared for all the pixels of the stimulable phosphor panel, and therefore the memory capacity for storing the correction data is large. It will increase. In particular,
When a plurality of stimulable phosphor panels are used, the memory capacity increases in proportion to the number of panels, which is not practically preferable.

The present invention has been made in view of such problems, and an object thereof is to perform shading and fading correction with an extremely small memory capacity, and to correct unevenness of radiation and stimulable phosphor, It is to realize a high-quality radiographic image information reading method and apparatus capable of removing the influence of aging.

(Means for Solving Problems) A first invention for solving the above problems is to irradiate a stimulable phosphor with radiation without arranging a subject to obtain first captured image information, Based on the first captured image information,
The first correction data for one line obtained from the information on the line parallel to the main scanning direction of the stimulable phosphor and the information on the line parallel to the sub-scanning direction of the stimulable phosphor 1 are obtained. The second correction data for lines is created for at least one line for each of the correction data, and then,
Place the subject and irradiate the stimulable phosphor with radiation.
Of the second photographed image information, the plurality of lines parallel to the main scanning direction of the second photographed image information are corrected by the correction data of one line in the first correction data, and at the same time, the second photographed image information is acquired. A plurality of lines parallel to the sub-scanning direction of the second
The radiation image information reading method is characterized in that the correction is performed by the correction data of one line in the correction data of 1.

A second aspect of the invention is a radiation image information reading device that irradiates a stimulable phosphor with radiation to obtain captured image information, and performs image processing on the captured information, in a radiation image information reading device without disposing a subject. For one line created by irradiating the stimulable phosphor with radiation to obtain first photographed image information, and based on the information of the line in the main scanning direction of the stimulable phosphor based on the first photographed image information. First storage means in which at least one line of first correction data is stored, and one line created from information of lines in the sub-scanning direction of the stimulable phosphor based on the first captured image information. Second storage means in which at least one line of the second correction data is stored, and a subject is arranged, and second photographing is performed by irradiating the stimulable phosphor with radiation. Third storage means for storing image information A plurality of lines parallel to the main scanning direction of the second captured image information are corrected by the correction data of one line in the first correction data, and at the same time, in the sub scanning direction of the second captured image information. The radiation image information reading apparatus is characterized in that it has a correction calculation means for correcting a plurality of parallel lines with the correction data of one line in the second correction data.

(Operation) Since correction data for shading correction and fading correction are created by obtaining the light emission amount of each pixel on each line parallel to the main scanning direction and the sub-scanning direction and the reference value, an extremely small memory capacity With, it is possible to perform a correction close to the total correction.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a flow chart showing an embodiment of the method of the present invention.

First, the photostimulable phosphor is irradiated with radiation without arranging a subject to obtain first captured image information (step), and the first captured image information is stored in a predetermined memory without correction. It

Next, at least one of the first correction data for the main scanning direction and the second correction data for the sub-scanning direction of the photostimulable phosphor is created based on the first captured image information (step). FIG. 2 is an explanatory diagram showing an example of a method of creating these correction data. In FIG. 9A, P is the first captured image information, x indicates the main scanning direction of the image, and y indicates the sub-scanning direction of the image. It is assumed that 2048 pixels are arranged in the main scanning direction x and 2560 scanning lines are present in the sub scanning direction.

Px indicates the profile in the main scanning direction x, and Py indicates the profile in the sub scanning direction y. Here, the correction data represents the difference between the respective maximum values of the light emission amounts in the profiles Px and Py and the light emission amounts of the respective pixels in the main scanning direction x (in the case of Px) and the sub-scanning direction y (in the case of Py). Try to ask.
As a result, as shown in (b), the difference between the maximum value of the light emission amount on the profile Px and the light emission amount of each pixel in the main scanning direction x is the first with respect to the main scanning direction x of the stimulable phosphor.
It becomes the correction data of and the shading can be corrected. Further, as shown in (c), the difference between the maximum value of the light emission amount on the profile Py and the light emission amount of each pixel in the sub-scanning direction y is the second value with respect to the sub-scanning direction y of the stimulable phosphor.
It becomes the correction data of, and the fading can be corrected.

Note that the difference between the minimum value of the light emission amount of each profile Px, Py and the light emission amount of each pixel in the main scanning direction x and the sub scanning direction y can be obtained as the first and second correction data. ,
In this case, since the dynamic range of the signal is adjusted to the minimum value and narrowed, it is more preferable to adjust it to the maximum value as described above.

Further, in creating these correction data, if the first correction data is created from the data of only one line, the value of the correction data may differ greatly from the actual value when pulse noise is mixed. Therefore, for example, the first
In the case of the correction data of No. 1, it is more preferable to add photographed image information of a plurality of main scanning lines and then take the average thereof to obtain the first correction data.

Then, the second photographic image information is obtained by arranging a subject and irradiating the photostimulable phosphor with radiation (step), and the second photographic image information is converted into the first correction data and Correction is performed using at least one of the second correction data (step).

In such correction, the data of the corresponding pixel of the first correction data with respect to the light emission amount data of each pixel in the same column of the second captured image information (the same correction amount in the same column)
And the data of the pixels on the corresponding scanning line of the second correction data (the same correction amount on the same scanning line) may be added to the light emission amount data of each pixel on the same scanning line. That is, taking the correction using the first correction data as an example, since the signal (s) is converted into a constant, the image signal (S) becomes (S) = log s. If the signal (s) is 0.7 times as shaded, then (S ′) = log s × 0.7 = log 0.7 + log s = log s−0.15. Therefore, by adding 0.15 as the first correction data to the obtained signal (S '), shading corrected data is obtained. In the case of fading, exactly the same can be done by using the second correction data. Therefore, by adding the first and second correction data for each pixel, it is possible to obtain data in which shading and fading are corrected.

According to such a method, the memory area for storing the correction data may be 2048 + 2560 at the maximum in the case of FIG. 2, and the memory capacity can be reduced.

Further, it is also possible to obtain synthetic correction data for the corresponding pixel in advance from the first correction data and the second correction data, and perform correction for all pixels using this synthetic correction data.

Further, the correction data may be prepared for each of a plurality of pixel columns,
You may prepare for every several scanning line.

Next, the structure of the apparatus for achieving the method of the present invention will be described. With this configuration, shading using the correction data in the reading device,
It has a circuit section for executing fading correction, and has an external data processing device to create correction data.

The reading device does not have a correction circuit system, and an external data processing device creates and corrects correction data.

The reading device has a circuit system that creates correction data and a circuit system that executes correction.

A configuration such as is conceivable.

Here, the case of the above configuration will be described with reference to FIGS. 3 and 4.

FIG. 3 is a block diagram of the main part of the reading device used in the present invention, and FIG. 4 is a block diagram of the main part of the data processing device. The same parts as those in FIGS. 9 and 10 are designated by the same reference numerals. ing. In the figure, a panel 11 containing a stimulable phosphor 4
1 is fixedly arranged in the reader 5. Reference numeral 136 is an interface with the reading device 5, and 122 is image data sent from the reading device 5 to the data processing device 200 at high speed.
A memory for temporarily storing it, 126 is a memory used as a first storage means for storing first photographed image information obtained by irradiating the photostimulable phosphor 4 with radiation without disposing the subject 3. , 127 is a memory used as a second storage means for storing correction data created based on the first captured image information stored in the memory 126, 128
Is a memory used as a third storage means for storing second photographed image information obtained by arranging the subject 3 and irradiating the photostimulable phosphor 4 with radiation. Reference numeral 129 is a magnetic disk used as a mass memory. 130
Is an operation keyboard, 131 is an operation display, and 132 is a controller for controlling the keyboard 130 and the display 131. Reference numeral 133 is a display device for outputting an image, and 134 is a memory for storing image information to be output to the display device 133. 135 is a communication interface for communicating with the outside.
Reference numeral 136 denotes a bus to which each constituent block is connected, which is formed of an address bus, a data bus, and a control bus.

In such a configuration, the first photographed image information obtained by irradiating the photostimulable phosphor 4 with radiation without disposing the subject 3 is stored in the memory 126. The first photographed image information stored in the memory 126 is read out by the CPU 123, and is subjected to the arithmetic processing as shown in FIG. 2 described above to perform the above-mentioned first photographed image in the main scanning direction of the photostimulable phosphor 4. Correction data and / or second correction data for the sub-scanning direction. Then, the created correction data is stored in the memory 127.

On the other hand, the second photographed image information obtained by arranging the subject 3 and irradiating the photostimulable phosphor 4 with radiation is stored in the memory.
Stored in 128. After the predetermined data is stored in the memories 126, 127, and 128 in this way, the CPU 123 uses the correction data stored in the memory 127 to correct the second captured image information stored in the memory 128 as described above. Such correction calculation is performed.

With this configuration, shading correction and fading correction can be performed with a relatively small memory capacity.

Further, by performing the shading correction and the fading correction, it is possible to perform a correction close to the whole surface correction with a relatively small memory capacity.

In addition, an X-ray source that is normally used can be used for a series of imaging.

The correction data can be created at any time.

In the above embodiment, the correction data is created and the correction calculation is performed by the CPU 123.
However, the CPU 123 may perform only the correction data generation and a circuit for correction may be provided. Next, FIG. 5 shows a block diagram of a main part of such a configuration example. The same parts as those in FIG. 3 are designated by the same reference numerals. A control circuit 51 is provided in the reading device 5, and the control circuit 51 is provided.
A correction data memory 52 and a correction circuit 53 are connected to 51. An image signal is added to the correction circuit 53, and correction data is added from the correction data memory 52. The control device 6 is connected to the reading device 5 via the control circuit 51.
The control device 6 controls the operation of the reading device 5, and
Create correction data. Although the control device 6 is independently provided outside the reading device 5 in FIG. 5, it may be provided inside the reading device 5. It should be noted that the control device 6 may be considered to be the data processing device shown in FIG. 4 from which the portion for shading and fading correction is removed.

FIG. 6 is a flow chart showing the flow of operation in FIG. When the correction data is created, X-rays are first emitted without arranging the subject (step). The obtained image is output to the control device 6 without correction (step). The control device 6 creates correction data based on the input image (step), and stores the created correction data in the memory 52 (step).

On the other hand, at the time of reading an image, X-rays are emitted from the subject (step), and the image data is output while performing correction using the correction data stored in the memory 52 (step). In this case, for example, a non-volatile memory such as a magnetic disk may be provided in the control device 6, correction data may be stored in advance at an arbitrary time, and may be transmitted to the reading device 5 side when the device is started up.

FIG. 7 is a specific example diagram of a correction circuit for digitally correcting. In FIG. 7, the image data covers 3 digits with 10 bits. On the other hand, the correction data has both 8-bit fading and shading. The reason for using 8 bits is that the memory size becomes large when 10 bits are used, and the fading and shading of the actual image data are not so large as to require the correction data of 10 bits. 8 bits is a quantity that covers the fluctuation of 3/4 digits, which is sufficient for practical use.

By using 8 bits in this manner, including the memory capacity, it is approximately 1/100 of the case of a 10-bit digital circuit configuration.
2 is enough.

In FIG. 7, when creating the correction data, first, "0" is written from the CPU to the correction data memory 52 and the latch 53. Then, the operation for actually reading the image data is started. When reading the image data, a clock corresponding to each pixel or a plurality of pixels is added from the clock generator 54 to the counter 55. The counter 55 is incremented by the clock in synchronization with the horizontal synchronizing signal. At this time, since the correction data read from the correction data memory 52 is "0", the 9-bit adder 56, the 10-bit adder 57, the overflow processing circuit
The data output to the outside via the 58 and the interface 59 becomes image data for creating shading and fading correction data.

In writing the correction data, the CPU receives the correction data sent from the control device and stores it in the correction data memory 52.

Then, when correcting the image data, a clock is applied to the counter 55 from the clock generator 54 and the counter 55 is incremented in the same manner as described above. The latch 53 has
CP when the image data within one scanning period is not read
The fading correction data is read from the correction data memory 52 by the U and set. The correction data may be set once for a plurality of lines.

The correction can be performed by executing such a procedure.

FIG. 8 is a specific example diagram of a correction circuit that performs correction in analog mode. According to the configuration of FIG. 8, the 9-bit correction data is added to the D / A converter 60 and converted into an analog signal, which is then added to the logarithmically converted image signal by the adder 61 to perform A / D conversion. The device 62 converts it into a 10-bit digital signal and outputs it.

In the above description, the case where the first and second correction data are mainly used has been described, but it is also effective to perform the correction using only one of the correction data.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to correct shading and fading that can correct the unevenness of radiation and stimulable phosphors and remove the influence of aging with an extremely small memory capacity. A radiation image information reading method and apparatus capable of performing correction can be realized.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the method of the present invention,
FIG. 2 is an explanatory diagram of a method of creating correction data, FIGS. 3 and 4
FIG. 5 is a block diagram of the main part of the device of the present invention, FIG. 5 is a block diagram of the main part of another embodiment of the device of the present invention, FIG. 6 is a flowchart showing the flow of the operation of FIG. 5, FIG. FIG. 8 is a specific example of the correction circuit, FIG. 9 is an explanatory view of image recording on the stimulable phosphor, and FIG. 10 is a conventional configuration example. 4 ... Photostimulable fluorescer, 5 ... Reading device 6 ... Control device, 101 ... Laser light source 111 ... Image conversion panel, 114 ... Photodetector 120 ... Sample hold circuit 121 ... A / D converter, 123 …… CPU 126,127,128 …… Memory

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Haruo Karasawa 1 Sakura-cho, Hino-shi, Tokyo Photograph of Konishi Roku Photo Co., Ltd. Judge General Manager Judge Katsunori Ishii Kazuhiro Kosuge Hiroshi Ohara (56) Reference References JP-A-60-234643 (JP, A) JP-A-61-1878 (JP, A)

Claims (4)

[Claims] 1. A method of irradiating a stimulable phosphor with radiation without arranging a subject to obtain first photographed image information, and based on the first photographed image information, the main of the stimulable phosphor is measured. The first correction data for one line obtained from the information of the line parallel to the scanning direction and the second correction data for the one line obtained from the information of the line parallel to the sub-scanning direction of the stimulable phosphor.
Correction data of at least one line is created for each of the correction data, and then a subject is placed and the photostimulable phosphor is irradiated with radiation to obtain second photographed image information. A plurality of lines of the photographed image information parallel to the main scanning direction are corrected by the correction data of one line in the first correction data, and at the same time, a plurality of lines of the second photographed image information parallel to the sub scanning direction are corrected. The radiation image information reading method is characterized in that the correction is carried out with the correction data of one line in the second correction data. 2. Information of a plurality of lines in the main scanning direction of the first photographed image information is added and an average thereof is obtained,
The radiation image information reading method according to claim 1, wherein the first correction data for one line is created. 3. Information of a plurality of lines in the sub-scanning direction of the first photographed image information is added and the average thereof is obtained,
The radiation image information reading method according to claim 1 or 2, wherein the second correction data for the one line is created. 4. A radiation image information reading apparatus for irradiating a stimulable phosphor with radiation to obtain photographed image information and performing image processing on the photographed information, wherein the stimulable fluorescence is obtained without disposing a subject. The first photographic image information is obtained by irradiating the body with radiation, and first one line portion is created based on the information of the line in the main scanning direction of the stimulable phosphor based on the first photographic image information. First storage means for storing at least one line of correction data, and a line for one line created from information on a line in the sub-scanning direction of the stimulable phosphor based on the first captured image information. Second storage means in which at least one line of correction data of No. 2 is stored, and a second photographed image information obtained from the stimulable phosphor by arranging a subject and irradiating the stimulable phosphor with radiation. Third storage means for storing A plurality of lines parallel to the main scanning direction of the second captured image information are corrected by the correction data of one line in the first correction data, and at the same time, parallel to the sub scanning direction of the second captured image information. A radiation image information reading device, comprising: a correction calculation unit for correcting a plurality of lines with the correction data of one line in the second correction data.