JPH021075A - Treatment of radiation picture - Google Patents

Abstract

PURPOSE:To obtain a reproduced picture having uniform graininess throughout the picture by previously obtaining a main scanning directional graininess distribution, obtaining picture data based on the distribution, and after that executing a prescribed correcting operation for the picture data. CONSTITUTION:Stimulated phosphorescent light 9 while is made incident to a light receiving surface 25a is detected by a lengthy photomultiplier 25, and output analog data are passed through an amplifier 16 and digitized in an A/D converter 17. The data are picture data Sorg obtained from an accumulative fluorescent material sheet 1, in which radiation energy is uniformly accumulated and stored in a memory 18 as data for a correction. An operation part 19 obtains an X directional graininess distribution (ratio gamma) from the data. Next, the radiation picture of an object is stored in the sheet 1, and in the same manner, the picture data are stored in the memory 18. The operation part 19 averages the picture data of the peripheries of respective scanning points on the sheet 1 correspondingly to the respective scanning points, obtains blur masked picture data Sus, and performs an operation S'=1/gamma(Sorg-Sus)+Sus. The picture data S' are sent to a picture display device 20, and the radiation picture is reproduced and displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to image processing of radiographic images, and in particular, the present invention relates to image processing of radiographic images, and in particular reads light carrying radiographic image information with a one-dimensional optical sensor such as a long photo multiplier to generate an image. When obtaining data, the sensitivity of the long photo multiplier differs depending on the position where light enters the long photo multiplier, so the graininess of the reproduced image may differ partially based on the obtained image data. The present invention relates to a radiation image processing method that prevents a reproduced image that is difficult to observe.

(Prior Art) It is practiced in various fields to read a recorded radiation image to obtain image data, perform appropriate image processing on this image data, and then reproduce and record the image. For example, an X-ray image is recorded using an X-ray film with a low gamma value designed to be compatible with later image processing, and the X-ray image is read from the film on which it is recorded and converted into an electrical signal. After converting and performing image processing on this electrical signal (image data), contrast and sharpness can be improved by reproducing it as a visible image in photocopies, etc.

Efforts have been made to obtain reproduced images with good image quality such as graininess (see Japanese Patent Publication No. 81-5193).

The applicant has also proposed radiation (X-rays, α-rays).

When irradiated with β rays, γ rays, electron beams, ultraviolet rays, etc., a part of this radiation energy is accumulated, and then when irradiated with excitation light such as visible light, stimulable fluorescence exhibits stimulated luminescence depending on the accumulated energy. Radiographic image information of a subject such as a human body is partially recorded on a sheet of stimulable phosphor using a stimulable phosphor, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam. The resulting stimulated luminescent light is read photoelectrically to obtain image data, and based on this image data, a radiation image of the subject can be recorded on recording materials such as photographic materials, CRTs, etc. A radiation image recording and reproducing system that outputs visual images has already been proposed (Japanese Unexamined Patent Publication No. 5
No. 5-12429, No. 5B-11395.

No. 55-183472, No. 5B-104845, No. 55-116340, etc. ).

This system has the practical advantage of being able to record images over a much wider range of radiation exposure compared to conventional radiographic systems using silver halide photography. In other words, in a stimulable phosphor, it is recognized that the amount of emitted light that is stimulated to emit light due to excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range.
Therefore, even if the amount of radiation exposure varies considerably due to various imaging conditions, the amount of stimulated luminescence emitted from the stimulable phosphor sheet can be read by the photoelectric conversion means by setting the reading gain to an appropriate value. By converting the radiation image into an electrical signal (image data) and using this image data to output the radiation image as a visible image to a recording material such as a photosensitive material or a display device such as a CRT, it is not affected by fluctuations in radiation exposure. Radiographic images can be obtained.

In the above-mentioned systems, normally a recording body on which a radiation image is recorded is main scanned in a predetermined direction and sub-scanned in a direction approximately perpendicular to the main scanning direction, and the radiation image obtained from each scanning point is It is configured to obtain image data (electrical signals) by detecting light representing an image with an optical sensor.

The optical sensor is a long photomultiplier tube (long photomultiplier tube) that has a light-receiving surface extending along the main scanning line and is arranged close to the recording medium, which has already been proposed by the applicant. pliers) can be used (Japanese Patent Laid-Open No. 82-166
68). By using this long photomultiplier (hereinafter abbreviated as long photomultiplier), there is no need to use a large and complex-shaped light condensing body, which was necessary up until then. It is possible to improve the performance and reduce manufacturing costs.

(Problem to be Solved by the Invention) By using the long photomultiplier, it is possible to downsize the device as described above, but the long photomultiplier is a long photomultiplier that extends along the main scanning line. Since it has a light-receiving surface, it has a problem that the sensitivity of the elongated photomultiplier cannot be made uniform depending on the incident position of the light incident on the elongated light-receiving surface.

In other words, for example, the magnitude of the output electrical signal (the value of image data ) will be different. Similar errors also occur due to subtle errors in mounting dimensions when a long photomultiplier is attached to a device. In this case, the sensitivity distribution in the main scanning direction of the long photomultiple is determined in advance, and the amplification factor of the amplifier connected to the long photomultiplex is changed in real time based on this sensitivity distribution, or the amplification factor of the amplifier is changed in real time. By keeping the ratio constant and correcting the values of the image data after obtaining the image data, it is possible to correct unevenness in the sensitivity distribution with respect to the values of the image data.

However, even if the correction is made as described above, the low-sensitivity portions of the long photomultiple result in image data with poor graininess. That is, when an image is reproduced and displayed based on this image data, a region with poor graininess that extends in a band shape in the sub-scanning direction will appear in the reproduced image, corresponding to the region with low sensitivity of the long photomultiple. As a result, the band-shaped portion is reproduced with a coarse and grainy feel, resulting in a decline in the overall image quality performance of the reproduced image.

The present invention improves the image quality performance of the reproduced image by preventing band-like parts with degraded graininess from occurring in the reproduced image even if the light receiving sensitivity is uneven due to the long photomultiple itself or its installation error. The object of the present invention is to provide a radiographic image processing method that allows the following methods to be used.

(Means for Solving the Problems) The radiation image processing method of the present invention performs main scanning in a predetermined direction on a recording medium on which a radiation image is recorded, and sub-scanning in a direction substantially perpendicular to the main scanning direction. , the light representing the radiation image obtained from each scanning point is received by an optical sensor such as a long photo multiplier, MOS sensor, or CCD extending in the main scanning direction to obtain image data, and based on this image data. In a radiation image reading and reproducing system that obtains a reproduced image by scanning a recording medium that is substantially uniformly exposed to the radiation used to record the radiation image, the light obtained from each scanning point is received by the optical sensor. to obtain correction data, and based on this correction data, determine the graininess distribution in the main scanning direction that appears on the reproduced image based on the combination of the radiation and the optical sensor, and record the radiation image. After scanning the recorded recording medium to obtain the above image data, the ratio of the graininess at each point in the main scanning direction to the average graininess in the graininess distribution determined in advance is γ, and the above image data is
rg, and Sus is the blur mask image data obtained by averaging the image data within a predetermined range around each scanning point of the radiation image, corresponding to each scanning point of the radiation image.
When the image data after arithmetic processing is S', S' −−(Sorg −Sus) +Sus ・
...(1) Calculation is performed on the image data obtained from the radiation image according to the formula γ, and the graininess of the reproduced image due to the partially low sensitivity of the optical sensor in the main scanning direction is calculated. This feature is characterized by preventing physical deterioration.

Here, the above-mentioned "light representing a radiographic image obtained from each scanning point" and the above-mentioned "light obtained from each scanning point" include:
This includes stimulated luminescence light emitted from a stimulable phosphor sheet, light transmitted through a photographic film, or light reflected from a photographic film.

Furthermore, the above-mentioned main scanning and sub-scanning include scanning in which the light reception timing of each unit light receiving element arranged in large numbers, such as a CCD, is performed simultaneously.

(Function) The graininess of images reproduced based on image data is determined by the sensitivity (
(including other factors that result in results equivalent to the sensitivity of the optical sensor, such as installation errors of the optical sensor), and the lower the sensitivity, the worse the graininess tends to be. It is also known that the more the high spatial frequency components of a radiation image are emphasized by applying image processing to the image data, the more the graininess of the reproduced image deteriorates when the image is reproduced based on the image data after image processing. It is being

The radiation image processing method of the present invention scans a recording medium that is substantially uniformly exposed to radiation used for recording a radiation image,
The light obtained from each scanning point is received by a light sensor such as a long photomultiplier, a MOS sensor, or a CCD to obtain correction data.
Based on this correction data, the main scanning direction (hereinafter referred to as
This is called the main scanning direction. ) is determined in advance, so after scanning a recording medium on which a radiation image is recorded to obtain image data, image processing is performed on the image data to correct this graininess distribution. I can do it.

As a specific image processing method, for example, the average graininess RAM and the graininess R of each point are determined in advance, and when the ratio γ of these two graininesses is γ-R/RAV, S' m − (Sorg −Sus) 10Sus =
(2) By performing calculations on the image data to obtain the reproduced image according to the formula γ, the reproduced image has uniform graininess over the entire reproduced image regardless of the sensitivity distribution of the optical sensor. can be obtained. Above ('2J
The formula represents changing the ratio of addition of the blur mask image data Sus corresponding to the low spatial frequency of the radiation image and Sorg - Sus corresponding to the high spatial frequency of the radiation image by 1/γ. That is, for the part with average graininess (R = RAV - therefore γ - 1 part), equation (2) becomes S' = Sorg, and γ≠
1, for example, the part of the long photomultiplier with low sensitivity (
In other words, for the part with poor graininess - the part with γ〉1), S org-F corresponding to the high spatial frequency of the radiographic image
By lowering the ratio of s us , the graininess is improved, making it possible to obtain a reproduced image having --like graininess.

The graininess R1RAv can be determined by scanning a recording medium whose entire surface is irradiated with radiation, and receiving the light with an optical sensor to obtain correction data.
Hereinafter, this direction will be referred to as the sub-scanning direction. ) by calculating the rls value of a large number of correction data corresponding to a large number of pixels lined up in
1, and by determining the graininess R1 for each point 1 in the main scanning direction, the graininess R, which is a function of the distance in the main scanning direction, is determined, and the average value of the graininess R1 determined for each point is determined. This average value is determined as the average graininess R^V.

In addition, instead of directly determining the average graininess RAv of the graininess R1 at each point as described above and determining the ratio γ-E, the sensitivity E1 of each point of the AV optical sensor is calculated from the correction data above. and the average sensitivity EAV (as mentioned above, this includes other factors such as the installation error of the optical sensor and other factors that result in the same result as the optical sensor sensitivity and appear in the above correction data), and calculate these sensitivities as E , the ratio γ may be determined according to a formula using EAV.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

First, referring to FIG. 3, the entire apparatus using the present invention will be described.

FIG. 3 is a perspective view showing an example of a radiation image information reading device using the radiation image processing method of the present invention.

This device uses a stimulable phosphor (stimulable phosphor) that, as mentioned above, accumulates a portion of this radiation energy when it is irradiated with radiation, and then exhibits stimulated luminescence in response to the accumulated energy when it is irradiated with excitation light such as visible light. This is a device that uses a fluorescent phosphor.

In an imaging device (not shown), a stimulable phosphor sheet is uniformly irradiated with radiation, and radiation energy is uniformly accumulated over the entire surface of the sheet. The stimulable phosphor sheet 1 in which radiation energy has been uniformly accumulated over its entire surface in this manner is set at a predetermined position in the radiation image reading apparatus shown in FIG.

The stimulable phosphor sheet 1 set in this manner is conveyed (sub-scanning) in the direction of arrow Y by a sheet conveying means 3 such as an endless belt driven by a motor 2.

On the other hand, the excitation light 5 emitted from the laser light source 4 is transmitted to the motor 1.
A rotating polygon mirror 6 that is driven by 3 and rotates at high speed in the direction of the arrow.
After passing through a focusing lens 7 such as an fθ lens, the optical path is changed by a mirror 8 and the sheet 1
, and main scanning is performed in the direction of arrow X, which is substantially perpendicular to the sub-scanning direction (direction of arrow Y). From the part of the sheet 1 irradiated with this excitation light 5, stimulated luminescence light 9 is emitted in an amount corresponding to the accumulated radiation energy, and this stimulated luminescence light 9 is emitted from a long photomultiplier (photoelectron multiplication). (tube) 25 photoelectrically. Light receiving surface 25 of the long photomultiple 25
a extends along the main scanning line IO.

4A and 4B are a partially sectional perspective view and a partially sectional perspective view showing an example of the structure of the long photomultiplier 25 shown in FIG.
It is a sectional view taken in the I-1 direction shown in the figure.

This long photomultiplier 25 has an electrode structure generally referred to as a Venetian blind type. This long photomultiple 25 has a cylindrical main body 25A, a photocathode 25b is provided along the main body 25A facing the light receiving surface 25a, and a plurality of dynodes 25c are provided below the photocathode 25b. are stacked on top of each other with an insulating member 25d interposed therebetween.
5e constitutes a fixed multiplier 251'. Each of the dynodes 25c has a number of U-shaped notches formed in a single conductive plate, and is formed into a bent blind shape. A shield electrode 25g is fixed with a pin 25e below the multiplier 25r via an insulating member 25d, and an anode 25h is provided within the shield electrode 25g.

These electrodes are electrically connected to each terminal of the terminal group 251 provided at the end of the main body 25A in a one-to-one correspondence.

FIG. 5 shows an example of an electric circuit 50 for driving the long photomultiplier 25 and extracting photoelectric output. Portions corresponding to each portion of the long photomultiple 25 are shown in FIG. 4A.

The same reference numerals as in FIG. 4B are given. A negative high voltage is applied to the photocathode 25b via a negative high voltage application terminal 50a. Further, the negative high voltage applied to the negative high voltage application terminal 50a is applied to each of the dynodes 25c divided by the bleeder resistor group 50b. Further, the shield electrode 25g is grounded, and the anode 25h is grounded via a resistor 50c and is input to one terminal of the amplifier 50d. The other terminal of the amplifier 50d is grounded, and the photoelectrically converted image data is taken out as an electrical signal from the output terminal 50e. Note that the shield electrode 25
g is not necessarily required and may not be provided.

As shown in FIG. 3, the stimulated luminescent light 9 incident on the light-receiving surface 25a is detected by the long photomultiplex 25, and the analog data S1 outputted from the long photomultiplex 25 is transmitted to the amplifier 16 (for example, as shown in FIG. The signal is amplified by an amplifier 50d) shown in FIG. The digital image data S org thus obtained is input to the memory 18 and stored. Here, since the image data Sorg is obtained from the stimulable phosphor sheet 1 in which radiation energy has been accumulated in a manner similar to -, this is referred to as correction data.

- The correction data S org previously stored in the memory 18 is then read out by the calculation unit 19, and the calculation unit 19 calculates the length of the long photomultiplier due to fluctuations in the radiation irradiated to the stimulable phosphor sheet 1. The graininess distribution in the main scanning direction modulated by the sensitivity distribution is obtained as follows.

The above correction data is assumed to be X1j. 1. j is the main scanning direction (the X direction shown in Figure 3) and the sub-scanning direction (the 3rd direction), respectively.
Xlj represents the correction data corresponding to the first pixel in the main scanning direction and the j-th pixel in the sub-scanning direction.

Here, for example, the rms value of the correction data corresponding to pixels arranged in the sub-scanning direction is obtained for each point 1 in the main-scanning direction, and this is calculated based on the graininess R at point 1 in the main-scanning direction.
Set to 1. That is, let it be. Here, XI is the average value of the correction data in the j direction, that is, (m is the number of pixels arranged in the j direction).

The graininess R1 of each point 1 obtained as described above is averaged for 1, and this is defined as the average graininess RAv. That is, (n is the number of pixels arranged in the i direction).

The ratio γ between the graininess R of each point obtained in this way (the graininess R1 of each point 1 is expressed as R as a function of the distance in the main scanning direction) and the average graininess RAV is expressed as γ 1 ... ...(7) Find it as Av. In this way, the graininess distribution (ratio γ) in the main scanning direction is determined. The determined ratio γ is stored in the memory 18.

After the ratio γ is determined as described above, the stimulable phosphor sheet on which the radiation image is recorded is read.

In the above-mentioned imaging device that uniformly irradiates radiation onto a stimulable phosphor sheet, a subject such as a human body is irradiated with radiation and imaged, and a radiation image of this subject is accumulated on the stimulable phosphor sheet. recorded.

The stimulable phosphor sheet 1 that has been photographed is set in a predetermined position of the radiation image reading apparatus shown in FIG.

Thereafter, image data S org carrying radiation image information is obtained and stored in the memory 18 in the same way as reading the stimulable phosphor sheet uniformly irradiated with the radiation described above. Thereafter, the image data S is transferred from the memory 18 to the calculation unit 19.
org and the ratio γ determined in advance as described above are read out, and the calculation unit 19 calculates the partial deterioration of the graininess of the reproduced image due to the partially low sensitivity of the long photomultiplier in the main scanning direction. Image processing is performed to prevent this and to obtain uniform graininess over the entire reproduced image. That is, blur mask image data Sus is obtained by averaging image data within a predetermined range around each scanning point corresponding to each scanning point on the stimulable phosphor sheet 1 on which a radiation image has been accumulated and recorded. The image data read from the scanning point is processed by Sorgs, and then the image data is
′, S' −(Sorg −Sus)
+Sus---(8) Calculation is performed according to the formula γ.

The image data S' that has been arithmetic-processed so that the entire surface of the image has uniform graininess (after further image processing is performed if necessary) is displayed on an image display device 20 such as a CRT display. The radiation image is reproduced and displayed based on the image data S'.

FIG. 1 is a diagram showing an example of a function of the ratio γ obtained as described above in the main scanning direction (corresponding to the X direction in FIG. 3).

In this figure, the part A above γ-1 corresponds to a part where the sensitivity of the long photomultiplier is low, and corresponds to a part with poor graininess on the reproduced image when the image is reproduced. Portion B corresponds to a high-sensitivity portion of the long photomultiple, and corresponds to a portion with good graininess on the reproduced image.

Figures 2A to 2C show image data S after calculation processing from image data S org carrying radiation image information obtained after the graininess distribution (ratio γ) in the main scanning direction was determined.
′ as described above, S′ −(Sorg −Sus) +Sus −
(9) A diagram showing an example of a function to be obtained according to the formula of γ.

The obtained original image data S org has various spatial frequency components ranging from low spatial frequencies to high spatial frequencies, as shown for example in FIG. 2A. Since the blur mask image data Sus is obtained by averaging image data within a predetermined range around each scanning point, it has a functional form that emphasizes the low spatial frequency components of the image data Sorg.

FIG. 2B shows an example of a functional form obtained by subtracting the blur mask image data Sus from the image data S org.

In this way, Sorg-Sus uses image data S org
It is a functional form that extracts the high spatial frequency components of .

FIG. 2C shows an example of the functional form of the image data S' after the arithmetic processing.

The image data S' after the calculation process approximates the functional form of the original image data S org, but as shown in equation (9), the high spatial frequency component S org - Sus is 1/γ
Since the part A' (a part with poor graininess) corresponding to A shown in Fig. 1 is modulated by the blur mask image data Sus, the high spatial frequency component is suppressed, and it corresponds to B shown in Fig. 1. The portion B' (a portion with good graininess) has a functional form in which high spatial frequency components are emphasized.

By reproducing and displaying an image based on the image data S' obtained in this manner, a reproduced image having -like graininess over the entire surface can be obtained.

In the above embodiment, a device that receives stimulated luminescence light emitted from a stimulable phosphor sheet using a long photomultiplier was described. It can also be applied to devices that use line films, and can also be applied to devices other than long photomultis, such as MO
It can also be applied to devices using optical sensors such as S sensors and COD.

FIG. 6 is a perspective view of an embodiment of an X-ray image reading device that reads an X-ray image recorded on an X-ray film.

An X-ray film 30 on which an X-ray image has been recorded is set at a predetermined position and is conveyed by a film conveying means 31 in the direction of arrow Y' shown in the figure.

Further, the reading light 33 emitted from the light source 32 which is elongated in the -dimensional direction is converged by the cylindrical lens 34, and irradiates the X-ray film linearly in the X' direction which is substantially perpendicular to the arrow Y' direction. Below the X-ray film 30 irradiated with the reading light 33, the above-mentioned X A MOS sensor 35 is provided in which a large number of solid-state photoelectric conversion elements are arranged in a straight line corresponding to each pixel interval in the X' direction of the line image. This MOS sensor 35 transmits the reading light transmitted through the X-ray film 30 to each pixel interval in the Y' direction of the X-ray image while the X-ray film 30 is transported in the direction of arrow Y' while being irradiated with the reading light 33. The light is received at corresponding predetermined time intervals.

FIG. 7 is a circuit diagram showing an equivalent circuit of the MOS sensor 35.

Signals generated by photocarriers generated when the reading light 33 hits a large number of solid-state photoelectric conversion elements 36 are transferred to capacitors CI (1-1, 2, . . . ) in the solid-state photoelectric conversion elements 36.
・Accumulated in n). The accumulated photocarrier signals are sequentially read out by sequentially opening and closing the switch section 38 controlled by the shift register 37, thereby obtaining a time-series image signal. This image signal is then amplified by the amplifier 39 and output from its output terminal 40.

The output analog image signal is sampled and converted into a digital image signal, and then, based on this image signal, sensitivity variations, etc. of each solid-state photoelectric conversion element of the MOS sensor 35 are determined in the same manner as in the above-mentioned embodiment. According to
Image processing is performed to prevent partial deterioration of graininess of the reproduced image due to partially low sensitivity of the MOS sensor 35 in the X' direction (main scanning direction) in which the MOS sensor 35 extends. In this embodiment, instead of the MOS sensor 35, CCD, CP D (Charg
Needless to say, it is possible to use a method such as e Prlming Devlce). Furthermore, in reading the X-ray film, it is of course possible to scan the film two-dimensionally with a light beam in the same way as reading the stimulable phosphor sheet described above. Further, in the above embodiment, the light transmitted through the X-ray film 30 is received, but it is of course possible to be configured so that the light reflected from the X-ray film 30 is received.

As described above, the radiation image processing method of the present invention performs main scanning in a predetermined direction on a recording medium on which a radiation image has been recorded, and sub-scans in a direction substantially perpendicular to the main scanning direction, and processes data from each scanning point. It can be widely applied to general radiographic image reading and reproducing systems in which image data is obtained by receiving light representing the obtained radiographic image by a photosensor extending in the main scanning direction, and a reproduced image is obtained based on this image data. .

(Effects of the Invention) The radiographic image processing method of the present invention calculates the graininess distribution (ratio γ) in advance, scans the recording body on which the radiographic image is recorded, obtains image data S org, and then calculates S' −(Sorg −3us) +Sus −
Since the calculation is performed according to the formula of (to)γ, even if the sensitivity of the optical sensor is uneven in the main scanning direction, the entire reproduced image will have −-like graininess, and the image quality of the reproduced image will deteriorate. can be improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of a function of the ratio γ in the main scanning direction, and Figs. 2A to 2C are examples of functional forms during arithmetic processing of image data carrying radiographic image information. 3 is a perspective view showing an example of a radiation image information reading device using the radiation image processing method of the present invention, and FIG. 4A is a
A partially cross-sectional perspective view showing the structure of a long photomultiplex, FIG. 4B is a sectional view taken in the 1-1 direction of FIG. 4A, and FIG. 6 is a perspective view of an embodiment of an X-ray image reading device that reads an X-ray image recorded on an X-ray film, and FIG. 7 is an equivalent circuit of a MOS sensor. FIG. 1...Stormable phosphor sheet 3...Sheet transport means 6...Rotating polygon mirror 16...Amplifier 18...Memory 20...Image display device 25a...Light receiving surface 35... MOS sensor 50... Electric circuit for long photomultiplier 2.13... Motor 4... Laser 9... Stimulated luminescence light 17... A/D converter 19... Arithmetic unit 25.・Long photomulti 30...X-ray film Figure 3 Figure b b

Claims (1)

[Scope of Claims] The radiographic image obtained from each scanning point by main scanning in a predetermined direction and sub-scanning in a direction substantially perpendicular to the main scanning direction on a recording medium on which a radiographic image has been recorded. A radiation image reading and reproducing system that obtains image data by receiving light representing the radiation with the optical sensor extending in the main scanning direction and reproduces a reproduced image based on the image data, the radiation used to record the radiation image. A recording medium that has been exposed substantially uniformly to light is scanned, and the light obtained from each scanning point is received by the optical sensor to obtain correction data, and based on this correction data, the radiation and the optical sensor are The graininess distribution in the main scanning direction that appears on the reproduced image is determined based on the combination of Let γ be the ratio of the graininess of each point in the main scanning direction to the average graininess in the gender distribution, let Sorg be the image data, and let Sorg be the ratio of graininess at each point in the main scanning direction to the average graininess in the gender distribution, When the blur mask image data obtained by averaging the image data within a predetermined range is Sus, and the image data after calculation processing is S', S'=1/γ(Sorg-Sus
)+Sus, the image data obtained from the radiation image is subjected to calculations, and the granularity of the reproduced image due to the partially low sensitivity of the optical sensor in the main scanning direction is calculated. A radiation image processing method characterized by preventing deterioration.