JPS6175966A - Method and device for processing of radiation picture information - Google Patents

Abstract

PURPOSE:To process the picture information at a high speed after a reading process by obtaining a non-sharp mask signal corresponding to an ultra-low space frequency from a pre-read picture signal during a primary reading process. CONSTITUTION:The radiation picture information on a subject is stored in a storable phosphor sheet A. A pre-reading part 100 scans the sheet A, and the digital picture signal is supplied to a control circuit 18 for primary reading as well as to a signal processing circuit 19. The sheet A is irradiated by a laser light 41 at a primary reading part 200, and the stored radiation picture information in read out photo-electrically. This picture information is converted into an original picture signal and supplied to an arithmetic unit 48. In this case, the circuit 19 obtains a non-sharp mask signal corresponding to an ultra- low space frequency from a pre-read picture signal during a primary reading process. Thus the unit 48 can perform an operation to emphasize frequency components higher than said ultra-low space frequency immediately after the primary reading process.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to an image information processing method in a radiographic system used for medical diagnosis and the like, and an apparatus for carrying out the method, and more particularly relates to a method for processing image information in a radiographic system used for medical diagnosis, etc. Accumulate and record image information, then irradiate it with excitation light,
An image information processing method and apparatus in a radiation image information recording and reproducing system that detects stimulated light emitted according to accumulated and recorded image information, reads the image information, converts it into an electrical signal, and reproduces a radiation image from the electrical signal. It is related to.

(Technical Clarity of the Invention and Prior Art) When a certain kind of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, β-rays, electron beams, ultraviolet rays, etc.), part of the energy of this radiation is absorbed by the phosphor. When the energy is accumulated in a phosphor and the phosphor is then irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence in response to the accumulated energy. A phosphor exhibiting such properties is called a stimulable phosphor.

Using this stimulable phosphor, radiation image information of a subject such as a human body is temporarily recorded on a stimulable phosphor sheet (hereinafter referred to as a stimulable phosphor sheet), and the sheet is exposed to excitation light. A radiographic image information recording and reproducing system has been proposed that scans to generate stimulated luminescence, photoelectrically reads the stimulated luminescent light to obtain an image signal, and processes this image signal to obtain a radiographic image of a subject that is suitable for diagnosis. (For example, Japanese Patent Application Laid-open No. 55-i24
No. 29, No. 55-116340, No. 55-16347
No. 2, No. 56-11395, No. 56-104645, etc.).

This system has the very 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 and emitted by excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range. Even if the exposure amount varies considerably, the amount of emitted light is read by the photoelectric conversion means by setting the reading gain to an appropriate value and converted into an electrical signal, and this electrical signal is used to convert the photosensitive material, etc. By outputting a radiation image as a visible image on a recording material or a display device such as a CRT, a radiation image that is not affected by fluctuations in radiation exposure can be obtained.

In addition, according to this system, radiation image information stored and recorded in a stimulable phosphor is converted into an electrical signal and then subjected to appropriate signal processing, and this electrical signal is used to produce recording materials such as photographic light-sensitive materials, CRTs, etc. By outputting a radiographic image as a visible image on a display device, it is possible to obtain a radiographic image with excellent suitability for observation and interpretation (diagnosis).

However, even with the radiographic image information recording and reproducing system as described above, spatial frequency regions important for diagnosis are not clearly shown in the reproduced radiographic images, resulting in low contrast and poor diagnostic suitability. In view of these circumstances, the applicant has already proposed a radiation image information processing method that can improve diagnostic aptitude by emphasizing frequency components above ultra-low spatial frequencies that are effective for diagnosis and increasing contrast. (Japanese Patent Publication No. 55-163472).

This radiation image information processing method uses an unsharp mask signal Su corresponding to an extremely low spatial frequency at each reading point of a radiation image in the radiation image information recording and reproducing system as described above.
s is calculated, and when the original image signal read from the stimulable phosphor sheet is 3 org and the emphasis coefficient is β, the signal is converted by the calculation S' = Sorg + β (Sorg - Sus), and the above The present invention is characterized in that frequency components higher than extremely low spatial frequencies are emphasized and this signal S' is used for forming the visible image. Note that the emphasis coefficient β may be a constant, or as disclosed in JP-A-56-11038, it may be made smaller in a low-density region where visual sensitivity is high, and increased in a high-density region where visual sensitivity is low. It is also possible to use a function of density in consideration of visual characteristics.

Here, the unsharp mask signal S corresponding to very low spatial frequency
us is an unsharp image (
Hereinafter, this refers to a signal corresponding to the density of each reading point of a "non-sharp mask").

The above-mentioned non-sharp mask can be created by the following various methods.

The first is to store the original image signal at each reading point, read it out together with peripheral data according to the size of the unsharp mask, and calculate the average value (simple average or average value based on various weighted averages) of Sus. This is a method to find.

The second method is to read out the original image signal using a light beam with a small diameter, and if there is still an accumulated image, a light beam with a large diameter that matches the size of the non-sharp mask is used to signal the signal at each reading point. In this method, the signal is averaged together with the surrounding signals and read out.

The third method takes advantage of the fact that the beam diameter of the readout light beam gradually expands due to scattering in the phosphor layer.The original image signal 3org is created using the light emission signal from the incident side of the light beam, and the light beam is A non-sharp mask signal Sus is generated by light emission on the side through which the light is transmitted. In this case, the size of the unsharp mask can be controlled by changing the degree of light scattering of the phosphor layer and by changing the size of the aperture that receives the light.

According to the radiation image information processing method as described above, in the reproduced radiation image, frequency regions important for diagnosis are greatly emphasized, contrast is improved, and diagnostic suitability is improved.

However, in the radiation image information processing method described above, since an unsharp mask is created from the read image signal (original image signal) itself to be processed, it takes time to create the unsharp mask after reading, and therefore the reading There was a problem that post-funeral processing took a long time, or a problem that required special means to make a non-sharp mask.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and does not require time to create a non-sharp mask after reading.
Accordingly, it is an object of the present invention to provide an image information processing method that allows image information processing after reading to be performed at higher speed, and an apparatus for implementing the method.

(Structure of the Invention) The present invention provides a method for reading radiation image information in a radiation image information recording and reproducing system using the stimulable phosphor sheet, for example, in Japanese Patent Laid-Open No. 58-67242,
As shown in Publication No. 8-67243, prior to the reading operation (main reading) to obtain a visible image for observation and interpretation, the accumulation is performed using excitation light of a lower level than the excitation light used in the main reading. This method was developed by focusing on the fact that pre-reading is normally performed to read the accumulated recorded information of a phosphor sheet, and from this pre-read image signal, an unsharp mask signal Sus corresponding to the ultra-low spatial frequency at each reading point is generated. is obtained in advance, and using this unsharp mask signal SUS and the original image signal obtained by the main reading, immediately after the main reading, perform the above-mentioned demonstration 3' = Sorg-1-β (Sorg-Sus). (as mentioned above, β is a constant or variable).

Note that, as shown in the above-mentioned Japanese Patent Laid-Open No. 58-67242, etc., the above-mentioned pre-reading is performed to optimally set the reading conditions (reading gain, recording scale factor, etc.), image processing conditions, etc. in the main reading. However, the fact that the excitation light used for pre-reading is at a lower level than the excitation light used for main reading means that the effective amount of excitation light that the stimulable phosphor sheet receives per unit area during pre-reading is This means that the energy is smaller than that when reading a book. As a method of lowering the level of the excitation light for pre-reading than the excitation light for main reading, there is a method of reducing the output of the excitation light source such as a laser light source, and a method of reducing the excitation light emitted from the light source by N in its optical path.
A method of attenuating with a D filter, AOM, etc., a method of providing a light source for pre-reading and a light source for main reading separately and making the output of the former smaller than the output of the latter, a method of increasing the beam diameter of the excitation light, Examples include a method of increasing the scanning speed of excitation light and a method of increasing the transport speed of the stimulable phosphor sheet.

In the above-mentioned method of the present invention, since the unsharp mask is created from the pre-read image signal in parallel with the main reading, the creation of the unsharp mask has already been completed by the time the main reading is finished, so the above calculation is performed immediately after the main reading is finished. be able to. Therefore, according to the present invention, image information processing after main reading (that is, after reading the original image signal) can be performed at high speed, and the overall speed of radiation image information reproduction processing can be increased.

In addition, in the present invention, especially when the beam diameter of the excitation light in the pre-reading is set larger than that in the main reading, the image signal obtained by the pre-reading has a small number of pixels and carries an image that is blurred to some extent. It has become. Therefore, by using this pre-read image signal, the unsharp mask signal Sus can be created in a short time.

The image processing apparatus of the present invention that implements the image information processing method described above includes an excitation light irradiation means for irradiating excitation light onto a stimulable phosphor sheet on which radiation image information is accumulated and recorded; In a radiographic image information fFi reading device having a photodetecting means for photoelectrically reading stimulated luminescence light carrying radiation image information emitted from a phosphor sheet, a pre-reading means for performing the above-mentioned pre-reading is provided, and this a signal processing circuit that obtains an unsharp mask signal Sus corresponding to an ultra-low spatial frequency at each reading point from the pre-read image signal obtained by the pre-read means;
An arithmetic device is provided which performs an arithmetic operation of 10β (Sora - Sus) and outputs the signal S°.

J5 The above-mentioned pre-reading means is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-6724.
It may be provided separately from the main reading means as shown in Publication No. 2, or it may be provided separately from the main reading means as shown in Japanese Patent Application Laid-Open No. 58-67243.
As shown in the above publication, the main reading means may also be used, and the level of the excitation light during pre-reading may be lower than that during main reading by adjusting means.

(Embodiments) Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

The figure shows a radiation image information processing apparatus according to one embodiment of the present invention. Radiation image information of a subject is stored and recorded on the stimulable phosphor sheet A by irradiating the subject with radiation such as X-rays that has passed through the subject. When reading an image, first, while moving the stimulable phosphor sheet A in the pre-reading unit 100 in the direction of the arrow Y for sub-scanning, the laser beam 11 from the laser light source 10 is directed in the X direction by the scanning mirror 12. Main scanning is performed, and the radiation energy accumulated and recorded on the phosphor sheet A is emitted as stimulated luminescence light 13. The stimulated luminescence light 13 enters the inside of the light collecting plate 14 from one end surface of the light collecting plate 14 made by molding a transparent acrylic plate, travels through the light collecting plate 14 through repeated total reflection, and is received by the photomultiplier 15. Ru. The photomultiple 15 outputs a pre-read image signal SP corresponding to the amount of light emitted by the stimulated luminescent light 13, and this pre-read image signal SP is amplified by an amplifier 16, and then converted into a digital image signal SP by an A/D converter 17. ' will be converted to '. This digital image signal SP' is transmitted to a main reading control circuit 18 which will be described in detail later.
and is input to the signal processing circuit 19.

Next, the stimulable phosphor sheet A has a laser light source 40, a scanning mirror 42, a light condensing plate 44, and
, formal 45 is sent to the book reading section 200. In this main reading section 200, the stimulated luminescence light 43 emitted from the stimulable phosphor sheet A by irradiation with the laser beam 41 is input to the photomultiplier 45 and stored and recorded on the stimulable phosphor sheet A. The radiation image information obtained is read out photoelectrically (main reading).

The output of the laser light source 10 for pre-reading is the laser light 11ii for main reading! 40, preferably 10% or less, more preferably 3% or less)
The beam diameter of the laser beam 41 for pre-reading is set larger than the beam diameter of the laser beam 11 for main reading, so that the radiation energy accumulated in the stimulable phosphor sheet A is absorbed into the stimulable phosphor sheet A before the main reading. It is designed to prevent it from being dissipated.

The main reading image signal @S output from the main reading photomultiplier 45 is amplified by an amplifier 46, converted into a digital original image signal 3org by an A/D converter 47, and then input to an arithmetic unit 48.

The above-mentioned main reading control circuit 18 determines the optimum reading gain a and the optimum recording scale factor b based on the image signal SP' which is 1q reduced by the pre-reading.

The reading gain of the main reading amplifier 46 is 11 for main reading.
The reading gain a output by the i11111 circuit 18 is set, and the recording scale factor in the A/D converter 47 is also set to the recording scale factor b output by the main reading control circuit 18. By setting the reading gain and recording scale factor to the optimal values determined from the pre-read image signal SP' in this way, when reproducing radiographic image information as described later, a radiographic image with excellent observation and interpretation suitability is obtained. will now be played.

Further, the signal processing circuit 19 to which the pre-read image signal SP' is input obtains an unsharp mask signal Sus corresponding to a very low spatial frequency from the pre-read image signal SP' while the main reading is being performed. This unsharp mask signal Sus is described in detail in Japanese Patent Application Laid-Open No. 55-163472, and as mentioned above, the image signal SP' at each reading point of pre-reading is stored and the unsharp mask signal Sus is This is determined by reading out data along with peripheral data according to the size of the sharp mask and calculating their average value (simple average value or weighted average value). Here, as mentioned above, the pre-reading is performed using excitation light with a larger beam diameter than the main reading, so the pre-reading image signal SP' carries a somewhat blurred (unsharp) image, and also Since the number of pixels is smaller than in the actual reading, the process of obtaining the unsharp mask signal Sus from the pre-read image signal SP' can be performed at high speed.

The unsharp mask signal Sus is input to the arithmetic unit 48 to which the original image signal 3org is input, as described above. Immediately after the main reading is completed, the rendering device 48 calculates s'=sorg +β (Sora −Sus) “β” from the unsharp mask signal Sus and the original image signal 3org.
is an emphasis coefficient], and the resulting signal S' is sent to an image reproducing device such as a CRT 49, for example. By performing the above calculations and emphasizing frequency components above ultra-low spatial frequencies, in the radiation image reproduced on the CRT 49, the frequency gAlfc, which is important for diagnosis, is greatly emphasized, and the contrast is improved. The diagnostic suitability of the radiographic image is improved. The advantages of the above processing are described in more detail in the aforementioned Japanese Patent Application Laid-Open No. 163472/1983.

Note that in this embodiment, the arithmetic unit 48 includes a coefficient selection section 48a that selects the emphasis coefficient β.

The emphasis coefficient β has an optimum value depending on conditions such as the part of the subject and the image quality. Therefore, when reading radiation image information, the optimum emphasis coefficient β is set in advance by the coefficient selection unit 48a. put. In addition, when reading many pieces of radiation image information of the same type in succession, after setting the emphasis coefficient β that is considered optimal as described above,
It is also possible to change the emphasis coefficient β to a more preferable value by observing the reproduced radiographic image at T49.

In addition, the unsharp mask signal S before being input to the arithmetic unit 48
If it is possible to store each of us and the original image signal S org in the storage means, after a radiation image is reproduced and observed on the CRT 49, the value of the emphasis coefficient β can be changed more preferably by the coefficient selection unit 48a. However, it is also possible to redo the arithmetic processing using this changed emphasis coefficient β and reproduce the JJFA image again.

The image reproducing device that reproduces the radiation image using the signal S' is not limited to the above-mentioned CRT 49, but various other scanning recording devices, thermal recording devices, etc. can be used to obtain a hard copy of the radiation image. It's okay. Note that even when creating a hard copy using a recording device in this way, it is convenient if a monitoring means such as a CRT is provided so that the emphasis coefficient β can be changed to a preferable value while observing the monitor image. It is.

Note that the arithmetic unit 48 receives the original image signal 3 or
In addition to performing the above-described processing on g, image processing such as gradation processing may be performed on the original image signal 3org. Even when performing such image processing, it is possible to obtain the optimum image processing conditions from the prefetched image signal SP' and perform the image processing according to the optimum conditions.

Further, in the above-mentioned actual flI mode, the pre-reading section 100 and the main reading section 200 are provided separately, but as shown in, for example, Japanese Patent Application Laid-open No. 58-67243 and No. 58-67244, the pre-reading section 100 and the main reading section 200 are provided separately. The stimulable phosphor sheet is also used as the main reading section, and the stimulable phosphor sheet after pre-reading is returned to the reading section again by the sheet transport means for main reading, and the excitation light level at the pre-reading is adjusted to the level at the main reading using an appropriate adjustment means. It may be set lower than the excitation light level.

(Effects of the Invention) As described in detail above, according to the present invention, a radiographic image with excellent diagnostic suitability can be obtained by emphasizing frequency components higher than ultra-low spatial frequencies. Since a non-sharp mask signal is formed from the pre-read image signal in parallel, the above-mentioned emphasis processing can be performed immediately after the actual reading, and it is possible to speed up the radiation image information reproduction processing.

Furthermore, in the present invention, it is possible to speed up the process of obtaining a non-sharp mask, especially when the beam diameter of the excitation light in pre-reading is set larger than the beam diameter of the excitation light in main reading.

[Brief explanation of the drawing]

The figure is a schematic diagram showing an embodiment of the present invention. 10, 40... Laser light source 11.41... Laser light 12.42... Scanning mirror 13.43...
Stimulated luminescence light 15.45...Photomaru 16.46
...Amplifier 18...Control circuit for main reading 19...
Signal processing circuit 48... Arithmetic device 10080. Pre-reading section 200... Main reading section A.
...Storage phosphor sheet Sus...Non-sharp mask signal 3org...Original image signal β...Enhancement coefficient

Claims (5)

[Claims] (1) A stimulable phosphor sheet on which radiation image information is stored and recorded is irradiated with excitation light, and the stimulated luminescent light emitted from the stimulable phosphor sheet is photoelectrically read to obtain an electrical signal. In a radiographic image information reading method for reproducing radiographic images as visible images based on In addition, from the pre-read image signal obtained by this pre-read, a non-sharp mask signal Sus corresponding to the ultra-low spatial frequency at each reading point is obtained. When the original image signal read out from the stimulable phosphor sheet by the main reading is Sorg and the emphasis coefficient is β, the calculation S'=Sorg+β(Sorg-Sus) is performed to obtain the super A radiation image information processing method characterized by emphasizing frequency components higher than a low spatial frequency and outputting the signal S' for forming the visible image. (2) The radiation image information processing method according to claim 1, wherein the beam diameter of the excitation light used for the pre-reading is larger than the beam diameter of the excitation light used for the main reading. (3) excitation light irradiation means for irradiating excitation light onto a stimulable phosphor sheet on which radiation image information is accumulated and recorded; In a radiation image information reading device having a photodetection means for photoelectrically reading exhaustion light, prior to main reading to obtain a visible image for observation and interpretation, excitation light of a lower level than the excitation light used in this main reading is used. A look-ahead means is provided for reading the accumulated record information of the stimulable phosphor sheet using a look-ahead means, and a look-ahead image signal obtained by the look-ahead means corresponds to an extremely low spatial frequency at each reading point. The unsharp mask signal Su
When the original image signal read out by the main reading is Sorg and the emphasis coefficient is β, the signal processing circuit that calculates s performs the calculation S'=Sorg+β(Sorg-Sus), and the signal S' is 1. A radiation image information processing device including a calculation device for outputting information. (4) The radiation image information processing apparatus according to claim 3, wherein the beam diameter of the excitation light used for the pre-reading is larger than the beam diameter of the excitation light used for the main reading. (5) A patent claim characterized in that the arithmetic device is connected to a monitor means for reproducing a radiographic image using an output signal thereof, and further includes a coefficient selection unit that selects a value of the emphasis coefficient β. The radiation image information processing device according to the range 3 or 4.