JP2005242369A - Radiation image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a radiation image reader capable of properly coping with the change of a substantial signal range of read image data, which is accompanied with correction. <P>SOLUTION: In the radiation image reader, correction data is generated from read data of a stimulable fluorescent plate (3) having a radiation image recorded therein without a subject (2), and read data is corrected by correction data when a subject image recorded in the stimulable fluorescent plate is read. The radiation image reader is provided with a correction restriction means (24) which restricts correction with correction data so that a dynamic range of image data after correction is within a dynamic range at the time of output. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radiographic image reading apparatus that optically reads radiographic image information, and in particular, read image data in a reading apparatus that needs to accurately reproduce fine grayscale information, such as a reading apparatus that uses a stimulable phosphor. It is related with correction technology.

  FIG. 13 is a diagram illustrating a method of recording an image (for example, a medical diagnostic image) on the photostimulable phosphor plate. X-rays emitted from the X-ray source 100 are focused by the diaphragm 200 and then irradiated to the subject 300. X-rays transmitted through the subject 300 are incident on a stimulable phosphor plate 400 (hereinafter simply referred to as a plate), whereby a latent image of the image of the subject 300 is formed.

  This latent image is imaged by scanning a laser beam to excite the plate, radiating the accumulated latent image energy as fluorescence, condensing the fluorescence with a concentrator, and a photomultiplier tube (photomultiplier). The analog electric signal is detected by a photodetector equipped with a pliers (hereinafter simply referred to as “photomal”), and the obtained analog electric signal is A / D converted and digitized, and then the data is subjected to predetermined signal processing.

  In addition to correction of unevenness (shading) by the condenser and photodetector, the reading image data correction technique for performing higher-accuracy image reproduction includes fading in which the emission intensity of the phosphor is attenuated over time. Correction for is necessary.

  Further, for example, when scanning a light beam using a polygon mirror PG (having A-plane to H-plane as reflection surfaces) as shown in FIG. 14A, as illustrated in FIG. There is a difference in reflectance between the A surface and other surfaces (for example, E surface). As a result, even if the same position of the plate is scanned, the plate is different between the case where the A surface is used and the case where the E surface is used. Therefore, the signal level to be detected differs from the distribution content in the plane. Therefore, it is necessary to perform correction in consideration of the polygon surface to be used.

  Further, as shown in FIG. 14C, there is a two-dimensional sensitivity unevenness (or unevenness due to X-ray unevenness) in the plate. is required.

  A technique is known in which shading correction data, fading correction data, and two-dimensional correction data are obtained from a solid image shot without placing a subject, and read data of an image shot with the subject placed is corrected using these correction data. (For example, refer to Patent Document 1).

Specify each surface of the polygon mirror and the sub-scanning position of the light beam so that this specific relationship is established when creating shading correction data, fading correction data, and two-dimensional correction data, and when correcting using these correction data. A technique for correcting read data in consideration of a polygon surface to be used is known (for example, see Patent Document 2).
JP-A-5-313262 (page 3-4, Fig. 1-4) JP-A-5-313264 (page 3-4, FIG. 1-5)

  Accompanying the correction of the image read data as described above, the substantial signal range of the read image data may change, and the quality of the reproduced image may deteriorate. Therefore, an object of the present invention is to realize a radiation image reading apparatus that can appropriately cope with a change in the substantial signal range of read image data accompanying correction.

  According to a first aspect of the present invention for solving the problem, correction data is created from read data of a photostimulable fluorescent plate in which a radiation image is recorded without a subject, and the subject image recorded on the photostimulable fluorescent plate is read. The radiographic image reading apparatus that corrects the read data with the correction data includes a correction limiting unit that limits correction by the correction data so that the dynamic range of the corrected image data is within the dynamic range at the time of output. The radiation image reading apparatus is characterized.

  In the first invention for solving the problem, the correction limiting means limits the correction data and / or the total correction data for each correction element to optimize the substantial signal range of the read image data by correction. This is preferable.

  Also, in the first invention for solving the problem, the correction limiting means makes the ratio of the number of pixels to be corrected with respect to the total number of pixels equal to or less than a predetermined value to optimize the substantial signal range of the read image data by correction. It is preferable in terms of taking a balance with density unevenness.

  Further, in the first invention for solving the problem, the correction limiting means may be configured such that the product of the number of pixels of the non-correction portion and the density unevenness is equal to or less than a predetermined value so that the substantial signal range of the read image data by correction is appropriate. This is preferable in that the balance between density and density unevenness is appropriate.

  In the first invention for solving the problem, the correction limiting unit may reduce the product of the number of pixels of the non-correction portion, the density unevenness, and the distance from the image end of the non-correction portion to a predetermined value or less. This is preferable in that the balance between the optimization of the substantial signal range of the read image data by the correction and the density unevenness is further appropriated.

  A second invention for solving the problem is to create correction data from read image data of a photostimulable phosphor plate in which a radiation image is recorded without a subject, and subject images recorded on the photostimulable phosphor plate. In the radiation image reading apparatus that corrects the read image data with the correction data at the time of reading, the reading of the photostimulable phosphor plate and the read image data of the photostimulable phosphor plate with a wider dynamic range than at the time of output A radiological image reading apparatus comprising a dynamic range conversion unit that performs correction and outputs a reduced dynamic range during output.

  In the second invention for solving the problem, reading of the photostimulable fluorescent plate recording a radiation image without a subject, reading of the photostimulable fluorescent plate recording a subject image, and reading by the correction data are performed. There is provided resolution conversion means for correcting the image data by increasing the number of density gradation steps corresponding to the expansion of the dynamic range and decreasing the number of density gradation steps corresponding to the reduced dynamic range at the time of output. This is preferable from the viewpoint of preventing a decrease in density resolution accompanying an expansion of the dynamic range.

  According to the first invention for solving the problem, since the correction is limited by the correction limiting means, it is possible to prevent an excessive change in the substantial signal range of the read image data due to the correction.

  According to the second invention for solving the problem, since the reading of the image data when there is no subject and the correction with the correction data are performed in a wide dynamic range, the real signal of the read image data by the correction is obtained. Respond appropriately to changes in range.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram of the radiation image reading apparatus. This apparatus is an example of an embodiment of the present invention. In FIG. 1, a portion surrounded by a broken line is a reading portion of a stimulable phosphor plate (hereinafter referred to as a phosphor plate). The structure of the reading part of this phosphor plate is shown in FIG.

  First, the reading part of the phosphor plate will be described. In FIG. 2, the phosphor plate 3 is fixed to the left side wall and is repeatedly used. The reading unit 90 moves along the guide shaft 71 by driving the ball screw 72 by the sub-scanning motor (stepping motor) 80, and scans the scanning line (light beam) 50 in the sub-scanning direction. Scanning in the main scanning direction is performed by the polygon scanning mechanism 60. The operation of the sub scanning motor 80 is controlled by the sub scanning motor control mechanism 110. The fluorescence is condensed by the condenser 4a and converted into an electric signal by the photomultiplier 4b.

  In FIG. 1, X-rays generated from an X-ray source 1 pass through a subject 2 and enter a phosphor plate 3 to form a latent image. When reading out the latent image, the plate 3 is scanned with a laser beam (by the laser light source 12 and the optical scanning mechanism 13), and the generated fluorescence is condensed by the condenser 4a and photoelectrically converted by the photomultiplier 4b.

  The output signal of the photomultiplier 4 b is amplified by the linear amplifier 6, logarithmically compressed and amplified by the logarithmic amplifier 7, sampled and held by the sample and hold circuit 9, and analog / digital converted by the A / D converter 10.

  The switch 14 serves to switch between a signal path at the time of correction data creation and a signal path at the time of actual image reading, and is switched to the A side at the time of correction data creation and to the B side at the time of image reading.

  The frame memory 15 stores the output data of the A / D converter 10 and the output data of the correcting means described later. The data stored in the frame memory 15 is output to the printer / self-machine 26 and the host CPU (not shown) through the controller 25.

  The timing circuit 11 supplies a timing clock to the sample hold circuit 9, the A / D converter 10, the correction data creating means 17 (described later) and the correction memory 23, respectively. The timing circuit 11 determines a read pixel size at the time of reading in accordance with radiographic image capturing conditions. For example, one read pixel size is selected and set from among three predetermined read pixel sizes of 0.1, 0.15, and 0.2 mm, and reading is performed with the set read pixel size. A timing clock is supplied to the sample-and-hold circuit 9 so as to perform this.

  The correction unit 24 includes a correction (subtraction) circuit 16 that corrects the read image data, a correction data generation unit 17 that generates various correction data for correcting the read image data, and correction data in the main scanning direction. A main scanning correction data memory 18 for storing, a polygon correction data memory 181 for storing correction data in the main scanning direction for each reflection surface of the polygon, a sub scanning correction data memory 19 for storing correction data in the sub scanning direction, and 2 A thinning data memory 20 for storing thinning data for dimension correction, an interpolation data creating means 21 for interpolating the thinning data to create two-dimensional correction data, an adding (and integerizing) means 22, and a correction data calculating means 221 And a correction memory 23 for storing correction data. Such correction means 24 is constituted by, for example, a microprocessor and a memory.

  The correction data for each correction element created by the correction data creation means 17 (real number type data with an accuracy of a bit after the decimal point) is stored in the memories 18, 181, 19, and 20 according to the type. The creation of correction data for each correction element by the correction data creation means 17 will be described later.

  The interpolation data creation means 21 performs linear interpolation based on the two-dimensional data, and creates interpolation data for each pixel. The creation of interpolation data by the interpolation data creation means 21 will be described later.

  Each correction data is added all at once by the addition (integerizing) means 22 and rounded to a whole number by rounding off a bit after the decimal point. The correction data corresponds to each pixel in the correction memory 23 via the correction data calculating means 221. Stored.

  At the time of image reading, correction data corresponding to each pixel is output from the correction memory 23, and the correction circuit 16 subtracts the read image data given through the switch 14 to correct the read image data.

  The correction data creation means 17 creates main scanning correction data, polygon correction data, and sub-scanning correction data with a plurality of read pixel sizes and stores them in the memories 18, 181 and 19, respectively. The interpolation data creating means 21 creates two-dimensional correction data with a plurality of read pixel sizes.

  That is, the memories 18, 181 and 19 store two types of correction data corresponding to images read at a plurality of pixel sizes, for example, two pixel sizes (0.1 mm and 0.2 mm), respectively. . Similarly, the interpolation data creating means 21 creates two types of interpolation data.

  The correction unit 24 selects correction data corresponding to the read pixel size of the radiographic image obtained by photographing the subject from among the correction data corresponding to the plurality of read pixel sizes obtained from the memories 18, 181, 19 and the interpolation data creating unit 21. Select and correct the image signal at the time of reading using the selected correction data.

When correction data is prepared corresponding to the two pixel sizes, there are the following three relationships between the read pixel size and the correction data.
(A) Select and use a pixel with a similar pixel size.
(B) The correction data calculation means 221 calculates and obtains correction data suitable for the actual read pixel size based on the two types of correction data.
(C) For each type of correction data, a pixel size for switching which of two types of correction data to select is set.
Among these methods, the method (c) is particularly effective when the influence of the change in the correction data due to the pixel size is different for each type of correction data. A specific example of this method is as follows.

  In this case, when reading with a pixel size of 0.14 mm, correction data of 0.2 mm is used only for polygon correction data, but correction data of 0.1 mm is used for other correction data.

  Note that information on the read pixel size is supplied from the timing circuit 11 to the adding means 22. Then, the adding means 22 selects correction data corresponding to the pixel size at the time of reading from the correction data in each of the memories 18, 181, 19 and the interpolation data creating means 21 by the above-described methods (a) to (c). Correction data for each pixel is created by addition.

  In this way, the correction data corresponding to the read pixel size is used, and the read value of the photostimulated luminescence intensity is corrected by the correction data, so that a good correction can be performed regardless of the pixel size.

  Next, creation of each correction data by the correction data creation means 17 will be described. In order to create correction data, solid imaging is performed by irradiating the phosphor plate 3 with X-rays from the X-ray source 1 without the subject 2. A latent image of the phosphor plate 3 that has been solidly taken is read by a reading system, and image data is stored in the frame memory 15. The correction data is created from this solid image data.

  FIG. 3 shows a configuration of a pixel matrix of image data stored in the frame memory 15. In FIG. 3, the X direction is the main scanning direction and has j columns X1 to Xj. The Y direction is the sub-scanning direction and has m rows Y1 to Ym.

  One row corresponds to one surface of a polygon mirror (hereinafter simply referred to as a polygon). For example, if there are 10 polygons, the same surface corresponds to every 10 rows. 10n + 1 to 10n + 10 are rows corresponding to each surface of the polygon. Note that n = 0, 1, 2, 3,.

(1) Creation of main scanning correction data Average values A1 to Aj of image data are obtained for each column X1 to Xj. Accordingly, when the solid image has density unevenness as shown in FIG. 4A, for example, profiles of average values A1 to Aj as shown in FIG. 4B are obtained. The upper part is cut out from the minimum value of such a profile, and this cut out part (right hatched part A) is set as main scanning correction data S1 to Sj. Such correction data is stored in the main scanning correction data memory 18. The main scanning correction data S1 to Sj correspond to shading correction data.

Further, by reading with different pixel sizes, image data for each column X1 ′ to Xk ′ is obtained, and similarly, correction data S1 ′ to Sk ′ are obtained.
The main scanning correction data S1 to Sj are correction data when the read image data is corrected by subtraction. On the other hand, there is a method of correcting the read image data by addition. In this case, the difference from the maximum value may be used as the correction data as indicated by the left hatched portion B. The same applies to the following correction data, though not described.

(2) Creation of polygon correction data Polygon correction data is created from data obtained by correcting solid image read data with main scanning correction data. Therefore, first, main scanning correction data S1 is subtracted from each image data belonging to the X1 column to perform main scanning correction on the X1 column image data. The same correction is performed on the image data of the X2 to Xj columns, and solid image data (primary corrected image data) subjected to main scanning correction is obtained.

  For this primary corrected image data, an average value B11 of image data belonging to 10n + 1 rows and belonging to column X1 is obtained. Similarly, average values B21 to Bj1 of image data belonging to 10n + 1 rows and belonging to columns X2 to Xj are obtained. Similarly, average values B12 to Bj2, B13 to Bj3,... B110 to Bj10 are obtained for 10n + 2 to 10n + 10 rows.

  If these average value groups B11 to Bj1, B12 to Bj2,... B110 to Bj10 are obtained, for example, as shown in FIG. ... Pj10 are cut out (shaded portions) and used as polygon correction data in the main scanning direction for each surface. The correction data P11 to Pj1, P12 to Pj2,... P110 to Pj10 for each surface are stored in the polygon correction data memory 181.

In the case of different pixel sizes, polygon correction data P11 ′ to Pk1 ′, P12 ′ to Pk2 ′,... P110 ′ to Pk10 ′ are obtained in the same manner using the data of X1 ′ to Xk ′ in (1).
(3) Creation of sub-scan correction data The sub-scan correction data is created from image data obtained by correcting a solid image with main scan correction data and polygon correction data. For this purpose, firstly, the above-mentioned primary correction image data is corrected with polygon correction data P11 to Pj1, P12 to Pj2,... P110 to Pj10 to obtain secondary correction image data.

  The secondary correction image data may be obtained by subtracting the main scanning correction data S1 to Sj and the polygon correction data P11 to Pj1, P12 to Pj2,... P110 to Pj10 from the solid image. As a result, a memory for storing the primary correction image data can be omitted.

  For such secondary corrected image data, average values C1 to Cm of the image data are obtained for each row Y1 to Ym. As a result, for example, profiles of average values C1 to Cm as shown in FIG. 4 (d) are obtained. The upper part is cut out from the minimum value of such a profile, and the cut out part (shaded part) is set as sub-scan correction data T1 to Tm. The sub-scan correction data T1 to Tm correspond to fading correction data. Such correction data is stored in the sub-scan correction data memory 19.

For different pixel sizes, correction data T1 'to Tn' are similarly obtained using Y1 'to Yn' obtained with different pixel sizes.
(4) Creation of two-dimensional correction data Two-dimensional correction data is created in the following steps (a) and (b).

(A) Creation of thinning correction data Thinning correction data is created from image data obtained by correcting a solid image with main scanning correction data, polygon correction data, and sub-scanning correction data. For this purpose, first, the above-mentioned secondary correction image data is corrected with the sub-scan correction data T1 to Tm to obtain tertiary correction image data.

  The tertiary correction image data is obtained by subtracting the main scanning correction data S1 to Sj, the polygon correction data P11 to Pj1, P12 to Pj2,... P110 to Pj10 and the sub scanning correction data T1 to Tm from the solid image. Also good. As a result, a memory for storing the secondary correction image data can be omitted.

  If the tertiary corrected image data has density unevenness as shown in FIG. 5, for example, thinned-out pixel data is obtained for such image data. That is, as shown in FIG. 6, the image data for the thinned pixels (B1 to B5) is obtained by averaging the data of surrounding N pixels and smoothing. Such calculation of thinned image data is performed in the main scanning direction and the sub-scanning direction.

  Next, with respect to the image data obtained in this way, the portion above the minimum value is set as thinning correction data Up1, Up2, Up3,. And These thinning correction data Up1, Up2, Up3,... Are stored in the thinning data memory 20.

(B) Interpolation of decimation correction data The decimation correction data Up1, Up2, Up3,... Are linearly interpolated by the interpolation data creating means 21 as shown in the lower left of FIG. Correction data Urs is obtained.

For different pixel sizes, similarly, correction data Urs' is obtained from S1 'to Sk', P11 'to Pk1', P12 'to Pk2', ... P110 'to Pk10' and T1 'to Tn'.
According to the study by the present inventor, steep unevenness components are removed by main scanning correction, polygon correction, and sub-scanning correction. Therefore, the thinned-out pixels have a ratio of, for example, one in 5 mm in both the main scanning direction and the sub-scanning direction. It has been found that considerable interpolation accuracy can be maintained to the extent required. Therefore, with respect to all pixel data, the amount of thinned pixel data is about 1/1000 when 175 μm is read. For example, even if all pixels have 5M words, the capacity of the thinned data memory 20 can be 5K words.

  In this way, the correction data is clearly separated for each element, created as main scanning correction data, polygon correction data, sub-scanning correction data, and two-dimensional correction data, and stored in each memory. These correction data are added by the adding means 22, and total correction data is created for each pixel and stored in the correction memory 23.

  Then, when reading the image of the phosphor plate 3 in which the subject 2 is photographed, the switch 14 is turned on to the B side, and the read image data is input to the correction circuit 16, and the correction data in the correction memory 24 is obtained from this input data. Subtract the unevenness correction.

  Since the correction data is generated in the order of main scanning correction data, polygon correction data, sub-scanning correction data, and two-dimensional correction data, accurate correction data for each element can be obtained. Therefore, highly accurate correction can be performed using these correction data.

  Next, the limitation on the correction amount will be described. The limitation on the correction amount will be described by taking the main scanning correction data as an example, but other polygon correction data, sub-scanning correction data, two-dimensional correction data, and total correction data obtained by adding all the correction data are corrected in the same manner. Restrictions are made.

  For example, as a profile (average value) in the main scanning direction of the read data of the solid image, as shown in FIG. 7A, the flat image is almost flat in the most area of the screen, but rapidly decreases at the left end. Is obtained, the main scanning correction data is cut out at the minimum value (level 1) and has a large correction amount as shown in FIG.

  For this reason, when this correction amount is subtracted from the read image data, there arises a disadvantage that the substantial signal range of the image data is narrowed. Therefore, in such a case, the correction data creation means 17 raises the correction amount cut-out position to level 2 and limits the correction amount as shown in FIG.

  In this case, the unevenness of the edge portion of the screen remains uncorrected, but the unevenness is corrected for the area that occupies most of the other screens, which is acceptable in practice. The level 2 value is determined by the allowable size of the uneven area, or the balance between the uneven value and the reduction amount of the actual signal range after correction.

  The allowable size of the uneven area can be defined by the ratio of the number of pixels in the uneven area to the total number of pixels on the screen. That is, the level 2 value is determined so that this ratio does not exceed a predetermined value. According to this, level 2, that is, the correction limit amount can be determined by a relatively simple algorithm.

  In addition, when setting level 2 in consideration of the unevenness value, it is preferable to define a predetermined value for the product of the number of pixels that are not corrected and the unevenness value, and to determine the correction limit amount based on the predetermined value. . As a result, correction can be restricted in consideration of image quality.

  Furthermore, in consideration of the fact that steep unevenness is likely to occur at the edge of the phosphor plate and that unevenness of the edge does not significantly affect image diagnosis, the pixel that is not corrected in consideration of the distance from the edge of the screen. A predetermined value may be set for the product of the number, the unevenness value, and the distance from the edge of the screen, and the correction limit amount may be determined based on the predetermined value.

  As shown in FIG. 8, when unevenness occurs in the substantial part of the screen instead of the edge of the screen, it is not appropriate to define the distance from the edge of the screen. Appropriate values between levels 3 and 4 are adopted depending on.

  Next, dynamic range conversion will be described. FIG. 9A shows an example of a histogram of image data obtained by reading the phosphor plate 3 obtained by photographing the subject 2, and FIG. 9B shows a histogram of output image data obtained by correcting the read image data. Show. Here, an example is shown in which the dynamic range for reading image data is the same as the dynamic range for outputting image data, for example, 0-4095 steps.

  The read image data having a histogram as shown in FIG. 9A has a substantial signal range narrowed as shown in FIG. For this reason, the portion that is over-range at the time of reading (the broken-line portion in FIG. 9A) can be included in the output dynamic range, but this portion is saturated due to the over-range at the time of reading. Information is lost.

  Therefore, in this apparatus, the dynamic range of image data reading is expanded so that the signal recorded on the phosphor plate 3 can be read without saturation. That is, using the A / D converter 10 with high accuracy, for example, by expanding the reading dynamic range to 0-8191 steps, the entire density range of the recording signal is read as shown in FIG. Further, it is preferable to read a solid image for creating correction data in the same dynamic range, but it may be narrow.

  The image data read in this way is corrected with a wide dynamic range. Since the substantial signal range of the output image data is reduced by the correction, the output image data is output in a dynamic range of, for example, 0-4095 steps (FIG. 10B). The conversion of the dynamic range for such output is performed by the controller 25. As a result, the entire density range of the read image data is read without loss, and image data that has been subjected to unevenness correction is output in an appropriate range.

  Next, resolution conversion will be described. When the reading dynamic range is expanded, the resolution for reading image data (density resolution) decreases in inverse proportion. Therefore, the number of bits of the A / D converter 10, that is, the number of bits of the image data is increased in accordance with the expansion of the reading dynamic range to prevent the resolution from being lowered.

  For example, when the reading resolution is increased from 0-4095 steps to 0-8191 steps, the number of bits of the image data is increased from 12 bits to 13 bits. As a result, the density difference can be expressed more finely by the amount of increase in the number of bits, which can counteract the reduction in resolution accompanying the range expansion. FIG. 11A shows this state, and the increase in the density level gradation step due to the increase in the number of bits is indicated by the expansion of the horizontal axis.

  Solid image data for creating correction data is also read in 13 bits. Then, creation of correction data and correction of read image data using the correction data are also performed with a resolution of 13 bits.

  The number of bits of the output image data after correction is reduced to 12 bits, and the density resolution corresponding to the reduction of the dynamic range described above is obtained. Such resolution conversion is performed by the controller 25.

  FIG. 12 shows a block diagram of a mechanism for reading and correcting image data with the above dynamic range conversion and resolution conversion. In FIG. 12, a reading device 500 reads image data with a 3.5-digit dynamic range and 13-bit resolution, and the correction means 600 corrects the read image data with the same dynamic range and resolution. The resolution is converted to a 12-bit resolution by the resolution conversion means 700, and converted to a 3-digit dynamic range by the dynamic range conversion means 800 and output.

  Here, the reading device 500 corresponds to the configuration from the reading unit 90 to the frame memory 15 in FIGS. 1 and 2, and the correction means 600 corresponds to the correction means 24 in FIG. 1, and the resolution conversion means 700 and the dynamic range. The conversion means 800 corresponds to the controller 25 in FIG.

It is a block diagram which shows the structure of the apparatus of an example of embodiment of this invention. It is a figure which shows the structure of the photostimulable phosphor plate reading part in the apparatus of an example of embodiment of this invention. It is a figure which shows the matrix of image data. It is a figure which shows the nonuniformity of a solid image, and the correction data produced from it. It is a figure which shows the two-dimensional nonuniformity of a solid image. It is a figure which shows thinning data and its interpolation data. It is a figure which shows the restriction | limiting of correction data. It is a figure which shows the restriction | limiting of correction data. It is a figure which shows the histogram of image data. It is a figure which shows the histogram of image data. It is a figure which shows the histogram of image data. It is a block diagram of an example of an apparatus of an embodiment of the invention. It is a figure which shows the concept of imaging | photography of a medical diagnostic image using a photostimulable fluorescent substance plate. It is a figure which shows the difference in the read signal by the surface of a polygon mirror, and the two-dimensional nonuniformity in a photostimulable phosphor plate. It is a figure which shows the difference in the shading characteristic by pixel size.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray source 2 Subject 3 Stimulable phosphor plate 4a Condenser 4b Photomultiplier 5 Power supply 6 Linear amplifier 7 Logarithmic amplifier 8 Filter 9 Sampled circuit 10 A / D converter 11 Timing circuit 12 Laser light source 13 Optical scanning mechanism 14 switch 15 frame memory 16 correction means 17 correction data creation means 18 main scanning correction data memory 181 polygon correction data memory 19 sub-scanning correction data memory 20 thinning data memory 21 interpolation data creation means 22 addition means 23 correction memory 24 correction means 25 controller 26 Peripheral devices such as printers and automatic processors

Claims (7)

  Radiation image reading that creates correction data from read data of a photostimulable fluorescent plate that records a radiographic image without a subject, and corrects the read data with the correction data when the subject image recorded on the photostimulable fluorescent plate is read The radiation image reading apparatus according to claim 1, further comprising a correction limiting unit that limits correction by the correction data so that a dynamic range of the corrected image data is within a dynamic range at the time of output.   The radiological image reading apparatus according to claim 1, wherein the correction limiting unit limits correction data and / or total correction data for each correction element.   The radiation image reading apparatus according to claim 1, wherein the correction limiting unit sets a ratio of the number of pixels to be corrected to a predetermined value or less with respect to the total number of pixels.   The radiological image reading apparatus according to claim 1, wherein the correction limiting unit sets a product of the number of pixels of the non-correction portion and density unevenness to a predetermined value or less.   3. The radiographic image reading according to claim 1, wherein the correction limiting unit sets a product of the number of pixels of the non-correction portion, density unevenness, and a distance from the image end of the non-correction portion to a predetermined value or less. apparatus.   Correction data is created from the read image data of the photostimulable phosphor plate on which the radiation image is recorded without a subject, and the read image data is corrected with the correction data when the subject image recorded on the photostimulable phosphor plate is read. In the radiation image reading apparatus, the stimulable phosphor plate is read and the read image data of the stimulable phosphor plate is corrected in a wider dynamic range than the output, and the dynamic range is reduced and output at the time of output. A radiographic image reading apparatus comprising a dynamic range conversion means.   Corresponding to the expansion of the dynamic range, the reading of the photostimulable fluorescent plate recording a radiographic image without a subject, the reading of the photostimulable fluorescent plate recording a subject image, and the correction of the read image data by the correction data 7. The radiographic image reading device according to claim 6, further comprising resolution conversion means that performs the increase in the number of density gradation steps and reduces the number of density gradation steps at the time of output in accordance with the reduced dynamic range. apparatus.

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