JPH01267636A - Radiograph reader - Google Patents

Abstract

PURPOSE:To determine optimum reading conditions from picture signals for prereading by storing many regular reading conditions determined based on the picture signals for prereading obtained from specific prereading conditions and finding optimum regular reading conditions for prereading based on them. CONSTITUTION:The title reader is equipped with a prereading means 1, a reading conditions determining means 2, and a regular reading means 3. A regular reading conditions arithmetic part 2a determines regular reading conditions GQ based on the picture signals for prereading Sp and outputs them to the reading means 3. A storing part 2b stores many regular reading conditions GQ determined in the regular reading conditions arithmetic part 2a, based on each of many picture signals for prereading associated with each of many radiograph for which prereading has been performed by the prereading means 1. A prereading conditions arithmetic part 2c reads out may regular reading conditions GQ stored in the storing part 2b and determines the optimum prereading conditions Gp2 which are outputted to the prereading means 1 in place of specific regular reading conditions Gp1. The optimum regular reading conditions can be thereby determined from the picture signals for prereading.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention involves scanning a stimulable phosphor sheet on which a radiation image is recorded with a light beam to radiate part of the radiation energy accumulated in the sheet. A pre-reading image signal representing the outline of the radiation image is obtained by performing pre-reading in which exhaustion light is emitted and read.Based on this pre-reading image signal, reading conditions for main reading, which will be described later, are determined, and then the sheet is read. Relating to a radiation image reading device that obtains an image signal representing the radiation image by scanning with a light beam having a higher level than the above-mentioned light beam and reading the stimulated luminescence light emitted from the sheet according to the above-mentioned reading conditions. It is something.

(Conventional technology) Radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.)
There are known stimulable phosphors (stimulable phosphors) that accumulate some of this radiation energy when irradiated with light, and then emit stimulated light according to the accumulated energy when irradiated with excitation light such as visible light. There is.

Using this stimulable phosphor, radiation image information of a subject such as a human body is partially recorded on a sheet of stimulable phosphor, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam to make it shine. The resulting stimulated luminescent light is generated and photoelectrically read to obtain an image signal, and based on this image signal, the radiation image of the subject is recorded as a visible image on a recording material such as a photographic light-sensitive material, a CRT, etc. A radiation image recording and reproducing system for outputting radiation images has already been proposed by the present applicant (Japanese Unexamined Patent Application Publication No. 1986-1999).
No. 12429, No. 5B-11395, No. 55-183
No. 472, No. 56-104845, No. 55-1183
No. 40, etc.).

This system has the practical advantage of recording 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 electric signal and using this electric signal to output the radiation image as a visible image to a recording material such as a photographic light-sensitive material or a display device such as a CRT, it is possible to create a radiation image that is not affected by fluctuations in radiation exposure. can be obtained.

In the above system, before reading the stimulated luminescence light emitted from the stimulable phosphor sheet to obtain an image signal, the stimulable phosphor sheet is scanned in advance with a low-level light beam and the sheet is scanned according to pre-reading conditions. Perform pre-reading to read the outline of the radiographic image recorded in the image, analyze the pre-read image signal obtained by this pre-reading to find the optimum main reading conditions for reading this radiographic image1, and then write the above information on the above sheet. There is a system configured to scan by irradiating a pre-read beam with a higher level than the light beam used for pre-reading, and perform main reading to obtain an image signal by reading according to the above-mentioned main reading reading conditions that are optimal for this radiation image ( Japanese Unexamined Patent Publication No. 1983-
No. 67240, No. 5g-67241.

No. 58-67242, etc.).

Here, the single pre-reading condition and the single pre-reading reading condition collectively refer to various conditions that affect the relationship between the amount of stimulated luminescence light and the output of the reading device in each pre-reading single reading. It means the reading gain, scale factor, or the power of the light beam in 'Elc extraction, which determines the relationship between input and output.

Also, the high level/low level of the destination beam is, respectively.
If the intensity of the light beam irradiated per unit area of the sheet or the intensity of stimulated luminescence light emitted from the sheet depends on the wavelength of the light beam (has a wavelength sensitivity distribution), It refers to the weighted intensity after weighting the intensity of the light beam irradiated per unit area of the sheet by the wavelength sensitivity, and the method of changing the level of the light beam is to use light beams of different wavelengths. methods to use, methods to change the intensity of the light beam itself emitted from a laser light source, methods to change the intensity of the light beam by inserting or removing an ND filter, etc. on the optical path of the light beam, methods to change the beam diameter of the light beam, etc. How to change the scanning density by changing,
Various known methods can be used, such as a method of changing the scanning speed.

(Problem to be Solved by the Invention) In the system that performs the above-mentioned pre-reading, the above-mentioned pre-reading conditions are usually set such that the photographed part of the subject (for example, the head of the human body,
It is defined for each radiographic image classified according to imaging conditions such as chest, abdomen, etc.) and imaging method (normal imaging, contrast imaging, enlarged imaging, etc.). However, even for radiation images that belong to the same classification, the exposure dose etc. differs greatly depending on the facility where the system is installed, and in order to cover all of these, it is difficult to read from fairly weak light to quite strong light. It is set to a wide range of reading conditions that can be used.

After performing pre-reading according to the pre-reading conditions and obtaining a pre-read image signal representing the outline of the radiation image, the stimulated luminescence light required for reproducing and observing a visible image from this pre-reading image signal in the main reading. Find the desired light amount range, determine the reading conditions for the main reading (main reading reading conditions) so that this desired light amount range occupies a predetermined signal range, and use the desired light amount range in the main reading. An image signal with good resolution is obtained by reading the stimulated luminescence light according to the reading conditions, and then image processing such as spatial frequency processing is performed on this image signal, and a visible image is reproduced based on the image signal after image processing. Output.

The pre-reading conditions are set over a fairly wide range as mentioned above, but as mentioned above, even radiographic images belonging to the same classification may differ from the same pre-reading conditions depending on the facility where the system is installed. The desired range in the obtained pre-reading image signal varies considerably, and even within one system, it varies considerably from radiographic image to radiological image, so due to the overlap of these fluctuations, the range of the pre-reading conditions may be exceeded. In such a case, there is a problem that it becomes impossible to determine the optimum actual reading conditions from the pre-read image signal.

In addition, if we try to set pre-reading conditions with a wider range to avoid this problem, it is necessary to use an optical sensor with a wider reading range to receive the stimulated luminescence light in pre-reading. However, it is technically difficult to construct such an optical sensor, and even if it is technically possible, it is expensive.

In view of the above-mentioned problems, the present invention provides a radiographic image reading system that is capable of determining optimal main reading conditions from the pre-read image signal by making the pre-read image signal obtained by pre-reading include a desired range. The purpose is to provide a device.

(Means for Solving the Problems) FIG. 1 is an overall configuration diagram showing clearly the configuration of a radiation image reading device of the present invention.

The radiation image reading apparatus of the present invention includes a reading means 1, a reading condition determining means 2, and a main reading means 3.

The reading means 1 scans a stimulable phosphor sheet on which a radiation image is recorded and a light beam to emit part of the radiation energy stored in the sheet as stimulated luminescence light. A pre-read image signal S representing an outline of the radiation image is obtained by photoelectrically reading according to predetermined pre-reading conditions GPI.

Further, the main reading means 3 scans the sheet with a light beam having a higher level than the light beam used in the pre-reading means 1, and photoelectrically converts the stimulated luminescent light emitted from the sheet according to the main reading conditions G0. The image signal is read to obtain an image signal representing the radiation image.

The image signal obtained in this way is transferred to an image processing device to undergo appropriate image processing as necessary, and is also transferred to an image reproduction device to reproduce and record a visible image based on the normalized image signal. Ru.

Further, the reading condition determining means 2 includes a main reading condition calculating section 2a.
, a storage section 2b, and a prefetch reading condition calculation section 2C.

The main reading reading condition calculating section 2a receives the prereading image signal SP obtained by the prereading means 1, calculates the above mentioned main reading reading condition G0 based on this prereading image signal S, and calculates the main reading reading condition Go.
is output to the book reading means 3.

The storage unit 2b stores a large number of main reading signals obtained by the main reading reading condition calculation unit 2a based on each of the large number of preread image signals corresponding to the large number of radiographic images read in advance by the prereading means 1. It is used to store reading conditions GQ.

The pre-reading reading condition calculation unit 2C reads out a large number of actual reading reading conditions Go stored in the storage unit '2b, and determines the optimum pre-reading reading conditions G and 2 based on these many actual reading reading conditions GQ, This optimal pre-reading reading condition GP2 is output to the pre-reading means 1 in place of the predetermined pre-reading reading condition GPI.

Here, only one predetermined pre-reading reading condition GPI may be determined for all the radiographic images read by the reading means 1, and for each radiographic image read by the reading means 1 for each of the above-mentioned imaging conditions. It may be classified and determined for each classified imaging condition. Optimal prefetch reading conditions GP above
One or more of 2 are submerged so that the target radiation image matches the predetermined pre-reading condition GP+.

(Function) By analyzing the above-mentioned main reading reading conditions, it is possible to determine how to ensure that the desired range during main reading is included in the pre-read image signal even if there are fluctuations due to shooting, etc. If pre-reading is performed under suitable pre-reading reading conditions, it is possible to know whether it is optimal or not.

The radiation image reading device of the present invention includes a prefetch reading condition calculating section 2.
c determines the optimum pre-reading reading condition based on a large number of main reading reading conditions, and replaces this optimum pre-reading reading condition with the predetermined pre-reading reading condition that had been used in the pre-reading means 1 until then. Since the output is to the pre-reading means 1, the pre-reading conditions used by the pre-reading means 1 can be optimized depending on the facility where this radiation image reading device is installed, changes over time, etc. It is possible to obtain a pre-read image signal that is updated and reliably includes a desired range so that the optimum main reading conditions can be determined according to each radiation image.

(Example) Examples of the present invention will be described below.

FIG. 2 is a perspective view showing an embodiment of the radiation image reading device of the present invention. This embodiment is a system using a stimulable phosphor sheet.

The stimulable phosphor sheet 11 on which the radiation image of the subject has been recorded is first scanned with a weak light beam to emit only a portion of the radiation energy accumulated in the sheet 11. It is set at a predetermined position of the pre-reading means 100 which performs pre-reading. The stimulable phosphor sheet 11 set at this predetermined position is moved by the motor 12.
The sheet is transported (sub-scanning) in the direction of arrow Y by a sheet transport means 13 such as an endless belt driven by. On the other hand, a weak light beam 15 emitted from the laser beam [14] is reflected and deflected by a rotating polygon mirror 1B driven by a motor 23 and rotates at high speed in the direction of the arrow, passes through a focusing lens 17 such as an fθ lens, and then is reflected by a mirror 18. Change the optical path and enter the sheet ll in the sub-scanning direction (direction of arrow Y)
The main scan is performed in the direction of the arrow X, which is substantially perpendicular to the main image. This light beam 15
Stimulated luminescent light 19 is emitted from the irradiated portion of the sheet 11 in an amount corresponding to the radiographic image information stored and recorded, and this stimulated luminescent light 19 is guided by a light guide 20 and sent to a photomultiplier. (Photomultiplier tube) 21 detects photoelectrically. The light guide 20 is made by molding a light-guiding material such as an acrylic plate, and is arranged so that the linear entrance end surface 20a extends along the main scanning line on the stimulable phosphor sheet 11. The photomultiplier 21 is attached to the output end surface 20b formed in an annular shape.
The light-receiving surfaces of the two are combined. The stimulated luminescent light 19 that has entered the light guide 20 from the input end face 20a travels through the interior of the light guide 20 by repeating total reflection, and then travels through the light guide 20 through the output end face 20b.
The photomultiplier 21 detects the amount of stimulated luminescence light 19 that represents a radiation image as an electrical signal.

The analog output signal S output from the photomultiplier 21 is amplified by the amplifier 2B and digitized by the A/D converter 27 to obtain a pre-read image signal Sp.

In the above-mentioned pre-reading, the voltage value applied to the photomultiplier 21 and The amplification factor etc. of the amplifier 26 are determined.

The digitalized pre-read image signal S obtained in this way is manually input to the main reading reading condition calculation section 28 in the reading condition determining means 200. In the main reading reading condition calculating section 28,
Input pre-read image signal SPI: Based on the main reading reading condition G so that an image signal having good resolution can be obtained in the main reading. is required. The obtained actual reading conditions CO are stored in the storage section 2 in the reading condition determining means 200.
9 and is stored therein, and is also sent to book reading means 100'.

In the main reading means 100', a voltage is applied to the photomultiplier 21' and an amplifier 2B according to the input main reading reading condition G0 so as to read the radiation image stored and recorded on the stimulable phosphor sheet with good resolution. ' amplification factor is controlled.

The stimulable phosphor sheet ll' whose pre-reading has been completed is set at a predetermined position in the main reading means 100', and the sheet 1 is irradiated with a light beam 15' which is stronger than the light beam used for the pre-reading.
1' is scanned, and an image signal S having a good resolution is obtained under the main reading reading condition G0 determined as described above.
Since there is a difference between the configuration of 0 and the path, components corresponding to each component of the pre-reading means 100 are indicated by adding a dash to the number used in the pre-reading means 100, and a description thereof will be omitted.

The image signal S0 obtained by being digitized by the A/D converter 27' is sent to the image processing device 300. The image processing device 300 performs appropriate image processing on the image signal SO. The image signal subjected to this image processing is processed by the image reproduction device g! 400, and a radiation image based on this image signal is reproduced and output.

When a large number of stimulable phosphor sheets 11 are read as described above, a large number of book reading means G0 corresponding to each sheet 11 are stored in the storage section 29 of the reading condition determining means 200.
is memorized. Thereafter, this large number of main reading conditions G0 are read out and input to the prefetch reading condition calculating section 30. The pre-reading condition calculating section 30 calculates the pre-reading obtained by the pre-reading means 100 based on a large number of input main reading conditions even if the radiation energy etc. accumulated in the stimulable phosphor sheet 11 changes. In order to obtain the optimal main reading reading condition G0 from the image signal S, the optimal pre-reading reading condition GP2 is set.
is determined and output to the pre-reading means 100' in place of the predetermined pre-reading reading condition GPI that has been used up until then.

In the pre-reading means 100, the input optimal pre-reading reading condition G
According to P2, the voltage applied to the photomultiplier 21 and the amplification factor of the amplifier 26 are determined.

FIG. 3 shows the light intensity of stimulated luminescence light, the pre-read image signal Sps obtained by the reading means, and the pre-read image signal Sps obtained by the main reading means, for explaining an example of how to determine the main reading reading conditions and the pre-reading reading conditions. FIG. 3 is a diagram showing an example of a histogram of the image signal SQ obtained by the image processing.

Here, the light quantity of the stimulated luminescence light emitted by the pre-reading means 100 and the light quantity of the stimulated luminescence light emitted by the main reading means 100' have the same histogram shape, but the light quantities themselves are significantly different. . However, for the sake of simplicity here, the histogram of the amount of stimulated luminescence light emitted in each of the pre-reading means 100 and the main reading means 100' is plotted on the horizontal axis (the logarithm of the amount of light). ) are shifted and superimposed into one.

In FIG. 3, the horizontal axis represents the logarithm value of the amount of stimulated luminescence light (however, the value differs between pre-reading and actual reading) as described above. In addition, the vertical axis (upper) is the value calculated by counting the degree of appearance of this light amount value for each pixel of the stimulable phosphor sheet,
The lower part of the vertical axis is read-ahead.

The pre-read image signal SPr image signal S0 obtained by the actual reading is proportional to the logarithm value of the above-mentioned light amount.

The histogram L of the amount of stimulated luminescence light has three peaks A, B,
C, and the portion corresponding to the necessary radiographic image is the mountain B portion. In other words, the mountains A and C are the part where the radiation is only scattered and the part where the radiation is directly irradiated onto the sheet ttc (see Figure 2) without passing through the object (transmission or reflection), and in order to reproduce and output a visible image. This is an unnecessary part. Mountain B is a necessary part corresponding to the subject.

Here, when the light intensity is Dmln, the minimum image signal is 5gm
1n is obtained and the light amount is Da+ax, predetermined pre-reading conditions are set so that the maximum image signals S, sax are obtained, that is, along the straight line GPI shown in the figure. At this time, since the frequency between Dgln and Ds shown in the figure is zero, the corresponding pre-read image signal Sp (S'p min =Sps) cannot be obtained. In the end, the range between Ds and Dsax shown in the figure (
The amount of light in the range in which the histogram is drawn with a solid line) is converted into a pre-read image signal Sp in the range sandwiched between SPS and SpHlaX.

When a histogram S of the pre-read image signal S obtained in this way is obtained, this histogram S corresponds to the solid line portion (the portions of peaks A and B) shown in the histogram of the amount of light. Here, in order to find the peak B' corresponding to the peak B of the histogram L of the amount of light, the pre-read image signal S,
The minimum value S.

iln (corresponding to the light 11Dsln), the value of the pre-read image signal S2 is searched in the direction of increasing.
(corresponding to the dot-dashed line), the second rising point a and the next falling point d can be found. The minimum and maximum values of the range between these two points a and b are SP + (point a
), 5P2 (corresponding to dots), only the pre-read image signal SP included in this range E is the desired signal range E that corresponds to the desired light amount range to be read during actual reading. .

After the desired signal range E is determined in this way,
The main reading means 100' (see FIG. 2) reads only the light amount range (desired light amount clause V!I) of stimulated luminescence light during main reading, which corresponds to this desired signal range E. , that is, along the straight line Go shown in the figure, the image signal S
The main reading conditions are determined so that o can be obtained. When the main reading conditions are determined in this way, the main reading means 100' determines the minimum light In D of the desired light amount clause FME'.
s is read as the minimum value SQ+gIn of the image signal SO, and the maximum light amount D2 is read as the maximum value Sgaax.

In this way, the desired light intensity node [E' is read so as to occupy the entire maximum image signal range E', so that
The obtained image signal SQ has the best resolution.

By the way, as described above, even for radiation images belonging to the same classification, the irradiation dose etc. differ greatly depending on the facility where the apparatus is installed. The pre-read reading conditions are set to a wide range that allows reading from fairly weak light to fairly strong light, but this is not always sufficient considering variations in each facility where the device is installed and variations in each radiographic image. The pre-read image signal S does not have a wide range, and the pre-read image signal S does not include the entire desired range, and it may not be possible to determine the optimum main reading conditions from the pre-read image signal S. on the other hand,
After a device is installed in a specific facility and starts operating stably, the variation between radiographic images belonging to the same classification in that device is within a much smaller range than when the facility-by-facility variation is taken into account.

Therefore, based on a large number of main reading conditions corresponding to each of the radiographic images read within a predetermined period after the device was installed, or a large number of main reading conditions corresponding to each of the predetermined number of radiographic images read after the device was installed, , the predetermined prefetch reading conditions used up until then are changed as follows.

The main reading condition CO calculated by the main reading condition calculating section 28 shown in FIG. be remembered. Book reading condition G stored in this way
o is read out together with a large number of stored actual reading conditions that have already been determined by the same procedure, and is input to the pre-reading condition calculating section 30. The pre-reading condition calculation unit 30 determines the optimum pre-reading conditions based on a large number of input main reading conditions so as to be most resistant to various fluctuations such as fluctuations in irradiation dose for a large number of radiation images. GP2 is required.

The straight line GP2 in FIG. 3 shows an example of the optimal pre-reading conditions obtained in this way. That is, when reading ahead in the future, the voltage value applied to the photomultiplier 21 and the amplification factor of the amplifier 26 are adjusted so that the stimulated luminescence light 19 emitted from the sheet 11 (see FIG. 2) is directed along the straight line GP2. is controlled. The straight line GP2 has a wide margin on both the maximum value side and the minimum value side of the desired light amount range (corresponding to mountain B) so as to be able to cope with variations in the irradiation dose of radiation images within the same classification. It is a prefetch reading condition. By performing reading under the optimal pre-reading conditions along this straight line GP2, the light amount range sandwiched between Dmln' and Diax' is read as a pre-read image signal SP sandwiched between 5pain, S, and max. Ru.

The pre-read image signal S, which has been pre-read according to the predetermined pre-read reading condition GPI described above, has a desired signal range E.
(corresponding to LLIB'), but as a whole it is closer to the S, +Iax side, and if the light amount changes in the direction of increasing further, there is a high possibility that it will exceed 5 plaX.

When the pre-read image signal sp is obtained according to the optimum pre-read signal GF2 obtained as above, 5 pat opening and 5 pla
The desired signal range is located approximately in the center of the range sandwiched between X and X, and the pre-read signal GP2 has the strongest reading condition against various fluctuations.

As mentioned above, optimization of the pre-reading conditions may be performed only once after installing the device to suit the facility where the device is installed, but is not limited to this. Requested by: c! The reading may be performed each time one sheet 11 is read based on a large number of stored reading conditions, or every predetermined number of sheets 11,
Alternatively, it may be performed every predetermined period.

Further, the entire radiographic image to be pre-read by the pre-reading means 100 may be pre-read under one pre-read reading condition, and the radiographic image may be classified according to the imaging conditions such as the imaging part of the subject and the imaging method. One prefetch reading condition may be determined for each classification.

Furthermore, some radiological images may include images that were taken under incorrect imaging conditions.

In this case, prefetching conditions may be required that are quite different from the prefetching conditions used up until then.
If a prefetch reading condition is determined that deviates by more than a certain value, it may be ignored.

(Effects of the Invention) As described above in detail, the radiation image reading device of the present invention obtains main reading conditions based on a preread image signal obtained by a predetermined preread reading condition in the prereading means, Since a large number of main reading reading conditions are stored and the optimum pre-reading conditions are determined based on these many main reading reading conditions, the pre-reading image signal obtained by pre-reading includes the desired range. Therefore, the optimum main reading conditions can be determined from the pre-read image signal.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram for clearly showing the configuration of the radiation image reading device of the present invention, and FIG. 2 is an example of the radiation image reading device of the present invention.
FIG. 3 is a perspective view showing an example of an apparatus using a stimulable phosphor sheet. FIG. 3 is a diagram showing an example of a histogram of the pre-read image signal SP% obtained by the reading means and the image signal S0 obtained by i% by the main reading means. 1.100... Pre-reading means 2, 200... Reading condition determining means 2a, 28... Main reading reading condition calculation section 2b, 29... Storage section 2c, 30... Pre-reading reading condition calculation Part 3.100'...Main reading means ii, +t'...Stormable phosphor sheet 14.14
'... Laser light source 19.19 '... Stimulated luminescent light 21.21 '... Photo multiplier 28.2
6'...Amplifier 27.27'...A/D converter 300...Image processing device 400...Image reproduction device Fig. 1 Fig. 3

Claims (1)

[Claims] (1) A stimulable phosphor sheet on which a radiation image has been recorded is scanned with a light beam to emit part of the radiation energy accumulated in the sheet as stimulated luminescent light, and this stimulated luminescent light is directed to a predetermined destination. a pre-reading means for photoelectrically reading according to reading conditions to obtain a pre-read image signal representing an outline of the radiation image; scanning the sheet with a light beam having a higher level than the light beam to detect the emission of radiation emitted from the sheet; a main reading means for photoelectrically reading the emitted light according to main reading reading conditions to obtain an image signal representing the radiation image; and a main reading means for obtaining an image signal representing the radiation image; and the main reading reading condition is determined based on the preread image signal, and A main reading condition calculation section outputs this main reading reading condition to the main reading means, and stores a large number of the main reading conditions corresponding to each of the radiation images obtained by the main reading condition calculation section. a memory section to
A large number of the main reading reading conditions stored in this storage section are read out, the optimum pre-reading reading conditions are determined based on the large number of main reading reading conditions, and the optimum pre-reading reading conditions are applied to the predetermined pre-reading conditions. 1. A radiation image reading apparatus comprising a reading condition determining means comprising a pre-reading reading condition calculating section which outputs an output to the pre-reading means in place of the reading condition.