KR20190044917A - A method for determining optimal scanning conditions of an X-ray scanning system - Google Patents

Abstract

Disclosed is a method of determining an optimal photography condition for an X-ray system. According to an embodiment of the present invention, the optimal photography condition determining method includes: a step (A10) of obtaining an X-ray image about a dummy; a step (A20) of calculating an exposure dose (σtotal) of a dummy region in the X-ray image by using a functional relation between pixel brightness and an exposure dose; a step (A30) of obtaining a histogram indicating the pixel brightness distribution of an interest region in the X-ray image and calculating a representative value representing variables of the histogram and an index value indicating the measure of dispersion of the histogram; a step (A40) of determining whether a first reference condition requiring the representative value to be no less than a first reference value, a second reference condition requiring the index value to be no less than a second reference value, and a third reference condition requiring the exposure dose (σtotal) to be no more than a third reference value are all satisfied; a step (A50) of repeating the A10 to A40 steps with at least one other photography condition if the first to third reference conditions are not satisfied as a result of the determination; and a step (A60) of determining a photography condition satisfying the first to third reference conditions as an optimal photography condition.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an X-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining optimal imaging conditions for an X-ray imaging system and, more particularly, to a method and apparatus for preventing a Dose Creep problem for a digitally retrofitted X- And a method that can be particularly useful for determining optimal shooting conditions.

The automatic exposure control device (AEC device) provided in the medical X-ray imaging system senses the accumulation amount of X-rays passing through the patient and automatically performs X-ray irradiation when the detected accumulation amount reaches the AEC threshold value Thereby preventing the X-ray from being excessively exposed to the patient and keeping the quality of the X-ray image constant.

In the case of a conventional analog imaging system using an X-ray film, as the tone of the image appearing on the X-ray film becomes darker, it can be judged that the amount of X-rays to be exposed to the patient is large. It is possible to set the AEC threshold value appropriately in such a way that the AEC threshold value is lowered and conversely if the image density is excessively low, the AEC threshold value is raised.

However, in the case of a digital photographing system using an X-ray sensor, a raw X-ray image is subjected to image processing to generate a processed X-ray image having a certain level of tone ray image, it is difficult to appropriately set the AEC threshold value based on the tone of the processed X-ray image.

This problem may be especially noticeable when retrofitting an analogue imaging system using X-ray film to a digital imaging system using an X-ray sensor.

Specifically, in the case of a retrofit X-ray system, the value of the AEC threshold adjusted to the X-ray film needs to be corrected to fit the X-ray sensor, and the processed X-ray image provided to the user (eg photographer) The user can not correct the value of the AEC threshold value appropriately for the digital X-ray sensor based on the tone of the processed X-ray image.

Thus, if the AEC threshold is not set to an appropriate value, a so-called 'Dose Creep' problem may occur in which an amount of X-rays more than necessary for the diagnosis of the patient is exposed to the patient due to the influence of the AEC threshold value exceeding the proper value have.

It has been reported that many X-ray imaging systems that are retrofitted digitally cause doze creep problems.

SUMMARY OF THE INVENTION The present invention has a primary purpose in providing a way to determine optimal shooting conditions for a retrofitted X-ray imaging system to prevent dose creep problems.

(A10) obtaining an X-ray image of a human body model; (A20) calculating an exposure dose? _Total for the model region in the X-ray image using a function relationship between pixel brightness and an exposure dose; (A30) obtaining a histogram showing a pixel brightness distribution of a region of interest in the X-ray image, calculating a representative value representative of the variances of the histogram and an index value indicating a scattering degree of the histogram; (A40) a first reference condition requiring the representative value to be equal to or greater than a first reference value, a second reference condition requiring the index value to be equal to or greater than a second reference value, and a requirement that the exposure dose? _{Total be} equal to or less than a third reference value Determining whether all of the third reference conditions are satisfied; (A50) repeating the steps A10 to A40 under at least one different shooting condition if the first to third reference conditions are not all satisfied; And (A60) determining an optimal photographing condition that satisfies all of the first to third reference conditions. The present invention also provides an optimal photographing condition determining method for an X-ray photographing system.

In the step A20, the exposure dose? _Total can be calculated by applying the following integral equation to the model area, and? (I) in the following integral equation represents a function between the exposure dose to the pixel brightness.

The parameters constituting the shooting condition may be a tube voltage, a tube current, and an AEC threshold value.

At this time, the step A50 may include repeating the steps A10 to A40 with one or more shooting conditions that differ only in the tube voltage among the parameters until the first reference condition is satisfied (A51); (A52) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the tube current among the parameters until the second reference condition is satisfied; And (A53) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the AEC threshold value among the parameters until the third reference condition is satisfied.

The parameters constituting the photographing condition may be tube voltage, tube current, and generator operation time.

In this case, the step A50 may include: repeating the steps A10 to A40 with at least one shooting condition that varies only the tube voltage among the parameters until the first reference condition is satisfied; (A56) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the tube current among the parameters until the second reference condition is satisfied; And (A57) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the generator operation time among the parameters until the third reference condition is satisfied.

The representative value may be a median, a mean value, or a mode value, and the indicator value may be a FWHM, a variation, or a standard deviation .

The present invention also relates to a fuel cell system comprising: a generator (110); An X-ray irradiating unit 120 for receiving X-rays from the generator 110 and applying X-rays to the artificial model P; An X-ray sensor 130 for detecting X-rays transmitted through the artificial model P; And a control unit 160 connected to the generator 110 and the X-ray sensor 130. The control unit 160 controls the X-ray imaging system to include: (A10) Obtaining an image; (A20) calculating an exposure dose? _Total for the model region in the X-ray image using a function relationship between pixel brightness and an exposure dose; (A30) obtaining a histogram showing a pixel brightness distribution of a region of interest in the X-ray image, calculating a representative value representative of the variances of the histogram and an index value indicating a scattering degree of the histogram; (A40) a first reference condition requiring the representative value to be equal to or greater than a first reference value, a second reference condition requiring the index value to be equal to or greater than a second reference value, and a requirement that the exposure dose? _{Total be} equal to or less than a third reference value Determining whether all of the third reference conditions are satisfied; (A50) repeating the steps A10 to A40 under at least one different shooting condition if the first to third reference conditions are not all satisfied; And (A60) determining an imaging condition that satisfies all of the first to third reference conditions as an optimal imaging condition.

The control unit 160 can calculate the exposure dose? _Total by applying the following integral equation to the model region, and? (I) in the following integral equation is a function between the exposure dose to the pixel brightness .

The X-ray imaging system senses the total amount of X-rays transmitted through the human body model P, and when the total amount of X-rays reaches the AEC threshold value, the electric power between the generator 110 and the X- And an AEC device 140 that automatically disconnects the connection.

The parameters constituting the shooting condition may be a tube voltage, a tube current, and an AEC threshold value.

At this time, the controller 160 repeats the steps A10 to A40 with one or more shooting conditions that differ only in the tube voltage among the parameters, until the first reference condition is satisfied, when performing step A50 ; (A52) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the tube current among the parameters until the second reference condition is satisfied; And (A53) repeating the steps A10 to A40 in one or more shooting conditions that differ only in the AEC threshold value among the parameters until the third reference condition is satisfied.

The parameters constituting the photographing condition may be tube voltage, tube current, and generator operation time.

At this time, the control unit 160 repeats the steps A10 to A40 with one or more shooting conditions that differ only in the tube voltage among the parameters until the first reference condition is satisfied (A55) when performing the step A50 ; (A56) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the tube current among the parameters until the second reference condition is satisfied; And (A57) repeating the steps A10 to A40 in one or more shooting conditions that differ only in the generator operation time among the parameters until the third reference condition is satisfied.

The representative value may be a median, a mean value, or a mode value, and the indicator value may be a FWHM, a variation, or a standard deviation .

According to the present invention, it is possible to determine optimal imaging conditions for an X-ray imaging system and apply it, so that it is possible to prevent an excessive amount of X-rays from being exposed to a patient at the time of imaging a patient, Deterioration of quality can also be prevented.

Further, the present invention can provide an AEC threshold value or a generator operation time together with a tube voltage and a tube current as an optimum imaging condition, so that it is useful for an X-ray imaging system having an AEC device as well as an X- Can be utilized.

1 is a block diagram showing an X-ray imaging system according to a first embodiment of the present invention.
2 is a block diagram showing an X-ray imaging system according to a second embodiment of the present invention.
FIG. 3 is a flowchart illustrating a method of determining an optimum photographing condition according to the first embodiment of the present invention.
FIG. 4 shows an example of an X-ray image of a human body model.
Figure 5 shows an example of a pixel brightness histogram for a region of interest.
FIG. 6 is a flowchart illustrating a method of determining an optimum photographing condition according to a second embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

First Embodiment of X-ray Photography System

An X-ray imaging system 100 according to a first embodiment of the present invention will be described with reference to Fig.

The X-ray imaging system 100 according to the first embodiment includes a generator 110, an X-ray irradiator 120, an X-ray sensor 130, an AEC apparatus 140, and a user interface 150.

The generator 110 supplies the tube voltage and the tube current necessary for X-ray generation to the X-ray irradiator 120. A generator switch 111 is provided between the generator 110 and the X-ray irradiating unit 120 for controlling the supply time of the tube voltage and the tube current.

The X-ray irradiating unit 120 irradiates X-rays toward the X-ray sensor 130. For example, the X-ray irradiating unit 120 includes an X-ray tube 121 and a collimator 122. The X-ray tube 121 receives the tube voltage and tube current from the generator 110 and generates X-rays. The collimator 122 serves to focus the X-rays generated by the X-ray tube 121 toward the X-ray sensor 130. Although not shown, a DAP sensor (Dose Area Product sensor) may be further provided in front of the collimator 122 to detect an X-ray dose.

The X-ray sensor 130 senses X-rays transmitted through the inspected object P and provides a digital signal for X-ray image generation. A grid device may be additionally provided between the X-ray sensor 130 and the inspected object P to block scattered X-rays emitted from the inspected object P.

The AEC device 140 detects the total amount of X-rays accumulated in the X-ray sensor 130 through the inspected object P during the photographing time, and when the total amount reaches the AEC threshold value, OFF state, thereby cutting off the electrical connection between the generator 110 and the X-ray irradiating unit 120. [ By providing such an AEC device 140, it is possible to prevent the X-ray from being excessively irradiated on the inspected object P, while the quality of the X-ray image can be stabilized.

The AEC device 140 includes an ionization chamber 141 disposed to face the X-ray sensor 130, a capacitor 142 connected to the ionization chamber 141, and an Automatic Exposure Control (AEC) 143 connected to the capacitor 142 ).

The ionization chamber 141 is filled with ionizable mononuclear gases such as helium (He) and nitrogen (N), and the mononuclear gases are ionized by the X-ray passing through the subject P to emit electrons . A voltage is generated between both terminals of the capacitor 142 as the discharged electrons move to the capacitor 142. [ The AEC 143 compares the voltage of the capacitor 142 with a predetermined AEC threshold value and turns off the generator switch 111 when the capacitor voltage reaches the AEC threshold value.

The operation of the AEC device 140 described above turns off the generator switch 111 when the total amount of X-rays passing through the inspected object P reaches a predetermined level during shooting, thereby stopping the X-ray imaging.

The X-ray imaging system 100 according to the present embodiment further includes a user interface 150, a control unit 160, and a display 170. [

The user interface 150 is an interface for controlling the system operation of the user. The user interface 150 includes a preset device connected to the generator 110 and the AEC 143, a keyboard and a mouse connected to the controller 160, and the like. The user can set the size of the tube voltage, the size of the tube current, and the size of the AEC threshold value using the preset device, and input commands, data, computer software programs, etc. for the operation of the controller 160 using the keyboard and the mouse can do.

The control unit 160 generates an X-ray image from the digital signal provided by the X-ray sensor 130 and displays it on the display unit 170. Here, the X-ray image is a raw image that has not undergone image post-processing or a processed image that has undergone image post-processing.

For example, the control unit 160 may provide a processed image when diagnosing a patient, and may provide a raw image when performing a method described below for determining an optimal photographing condition.

In addition, the controller 160 may control the generator 110 and the AEC 143 to change the sizes of the tube voltage, the tube current, and the AEC threshold value, respectively. The control unit 160 can provide the optimum shooting conditions (tube voltage, tube current, AEC threshold value) obtained as a result of the above method to the user in the same manner as outputting them to the display unit 170 or the preset device have.

Second Embodiment of X-ray Photography System

An X-ray imaging system 200 according to a second embodiment of the present invention will be described with reference to FIG.

Compared with the X-ray imaging system 100 of the first embodiment described above, the X-ray imaging system 200 of the second embodiment differs in that the AEC device 140 is not provided.

Accordingly, in the X-ray imaging system 100 of the first embodiment, the ON-OFF operation of the generator switch 111 is controlled by the AEC apparatus 140, so that the operation time of the generator 110 is determined , In the X-ray imaging system 200 of the second embodiment, the ON duration time of the generator switch 111 is set by the preset device or the control unit 160, so that the operation time of the generator 110 is determined.

The operation time of the generator 110 is equal to the radiation time of the X-ray irradiating unit 121 since the X-ray irradiating unit 121 can irradiate the X-ray when the generator 110 operates I can understand that.

First Embodiment of Optimum Shooting Condition Determination Method

Referring to FIG. 3, a first embodiment of a method (S100) for determining an optimum photographing condition according to the first embodiment of the present invention will be described.

3 is performed by the X-ray imaging system 100 of FIG. 1, the method S100 of FIG. 3 is similar to the method of FIG. The same can be applied to other types of X-ray imaging systems as well.

(1) preparation step (S0):

First, a human body model P to be used in the method of the present embodiment is selected, and one target ROI, which is to find an optimal photographing condition among a plurality of regions of interest (ROI) of the X-ray sensor 130, .

The first reference value R1 _th , the second reference value R2 _th , and the third reference value R3 _th are input to the controller 160. The meaning of these reference values will be described later.

And also inputs the initial photographing conditions to the control unit 160. [ That is, the initial values for the three parameters constituting the shooting condition, namely, the tube voltage (kV), the tube current (mA), and the AEC threshold value (AEC threshold) are input. It is preferable that these initial values are set to values sufficiently higher than those values normally applied at the time of diagnosis.

The input of the reference values and the initial values may be performed through the user interface 150.

(2) X-ray image acquisition (S110):

Next, the human body model P is photographed with the established tube voltage (kV), tube current (mA), and AEC threshold value to obtain an X-ray image of the human body model P.

At this time, the generator 110 provides the tube voltage (kV) and tube current (mA) set in the X-ray irradiator 120 and the AEC 143 of the AEC apparatus 140 sets the voltage of the capacitor 142 When the AEC threshold value is reached, the X-ray irradiation is stopped by switching the generator switch 111 to the OFF state.

The control unit 160 obtains the X-ray image of the human body P using the detection signal provided from the X-ray sensor 130 and displays the X-ray image on the display unit 170.

Note that the X-ray image provided by the controller 160 is a raw image. More specifically, in the case of the patient diagnosis, the control unit 160 provides a processed image through image processing. However, in the course of performing the method of the present embodiment, processed image, but rather a raw image.

(3) the human model (P) received Radiation dose ( σ _total ) (S120):

Next, the control unit 160 calculates the dose (? _Total ) received by the human body (P).

This will be described with reference to FIG. FIG. 4 shows an example of a raw image of a human body P obtained by applying the method of the present embodiment.

As shown in FIG. 4, the X-ray image (original image) of the human body model P is divided into a model region and a background region, and there is a region of interest specified in the model region.

In the model region, relatively bright pixels are relatively more absorbed by the x-rays in the corresponding human body part, and vice versa, while relatively dark pixels are relatively much transmitted by the corresponding x-ray in the human body part . That is, as the X-ray is more exposed in the corresponding part of the human body, the corresponding pixels of the X-ray image appear bright. Thus, the brightness of the image pixels and the dose of radiation have a function relation.

This function relationship can be secured in advance through experiments. When the brightness of each pixel is I and the functional relationship between the pixel brightness and the exposure dose is represented by σ (I), the following integration equation is applied to the model region, The _total dose (σ _total ) received by the human body (P) can be calculated.

(4) brightness distribution histogram and its Median ( MED ) And Full width (FWHM)  Calculation (S130):

Next, the controller 160 obtains a brightness distribution histogram for the ROI, calculates a representative value representative of the brightness variances of the histogram, and an index indicative of the degree of scattering of the histogram And calculates an index value.

In the method of this embodiment, a median is calculated as a representative value, and a full width at half maximum is calculated as an indicator value.

But other representative values and other indicator values may alternatively be applied.

For example, a mean value or a mode value may be applied instead of representative values representing brightness variances, and a variation or a standard deviation may be applied as an indicator value representing a scatter value .

Fig. 5 shows an example of the brightness distribution histogram obtained for the region of interest. In this histogram, the horizontal axis and the vertical axis represent the brightness variance and the pixel frequency, respectively. MED represents the median value, and FWHM represents the full width at half maximum.

(5) Calculated Median ( MED ), Full-width half width ( FWHM ) And The exposure dose (σ _total )this  It is determined whether the reference condition is satisfied (S140):

Next, the control unit 160 determines whether the calculated median value MED, full width at half maximum (FWHM), and exposure dose? _Total satisfy the reference condition.

Specifically, the control unit 160 determines that the first reference condition that the calculated median value MED is equal to or greater than the first reference value R1 _th , and that the calculated FWHM FWHM is equal to or greater than the second reference value R2 _th And a third reference condition that requires that the calculated exposure dose? _{Total be} equal to or less than the third reference value _R3th is satisfied.

The inventor of the present invention has found that the median value MED and the full width at half maximum (FWHM) must be equal to or greater than a certain level in order for the X-ray image to exhibit a good quality. Based on this, the first reference value R2 _th and the second reference value R2 _th are the values presented as the minimum target values of the median value MED and the half full width FWHM.

On the other hand, the third reference value R3 _th is a maximum allowable value of the dose to be received by the patient at the time of patient diagnosis using the X-ray imaging system 100. [

(6) If it is determined that all of the first to third reference conditions Not satisfied  , Steps S110 to S140 are repeated (S150):

As a result of the determination, if the calculated median value MED, full width at half maximum (FWHM), and exposure dose? _Total do not satisfy the first, second, and third reference conditions, If not, the control unit 160 repeats steps S110 to S140 described above.

For example, in this repetitive execution, steps S110 to S140 are performed by applying shooting conditions in which other parameters (tube current, AEC threshold value) are maintained and tube voltage is gradually increased by a predetermined value to find the tube voltage satisfying the first reference condition Repeating steps S110 to S140 by applying shooting conditions in which other parameters (tube voltage, AEC threshold value) are maintained and the tube current is gradually increased by a predetermined value in order to find a tube current satisfying the second reference condition, The process of repeating steps S110 to S140 is repeated by applying imaging conditions in which other parameters (tube voltage, tube current) are maintained and the AEC threshold value is gradually decreased by a predetermined value in order to find an AEC threshold value satisfying the third reference condition And so on.

(7) If it is determined that all of the first to third reference conditions Satisfied  , The optimum shooting condition is determined (S160):

If it is determined that all of the first to third reference conditions are satisfied, the control unit 160 determines the corresponding photographing condition as an optimal photographing condition, and transmits the determined optimum photographing condition to the display unit 170 or the preset device To the user.

Here, the optimal photographing conditions consist of the optimal tube voltage, the optimal tube current, and the optimal AEC threshold value, and the method of this embodiment is ended by outputting optimal values for each of these three parameters.

In actual patient diagnosis, a user (e.g., photographer) performs X-ray photography on a patient after setting the tube voltage, tube current, and AEC threshold value through a user interface 170 such as a preset device. By applying the determined AEC threshold value, it is possible to prevent the patient from being exposed to the X-ray dose exceeding the maximum allowable value (third reference value: R3 _th ), and to measure the tube voltage and the tube current determined in accordance with the above- By applying the tube current, it is possible to prevent the quality of the X-ray image from dropping below a certain level as the X-ray dose is limited.

The method of the first embodiment has the AEC device 140 and can determine the AEC threshold value for the digital retropitched X-ray imaging system to the digital X It can be particularly useful as a method for calibrating a new value suitable for a line sensor.

Second Embodiment of Optimum Shooting Condition Determination Method

A second embodiment of the optimal photographing condition determination method (S200) according to the second embodiment of the present invention will be described with reference to FIG.

In the following description, the method S200 of FIG. 6 is illustrated as being performed by the X-ray imaging system 200 of FIG. 2, but the method S200 of FIG. 6 may be applied to other types of X- As shown in FIG.

And, the method (S100) of the first embodiment described above is for determining an optimum operating condition consisting of an optimal tube voltage, an optimal tube current and an optimal AEC threshold value, while the method S200 of the second embodiment The optimal tube current, and the optimum generator operation time of generator.

Therefore, in the following description, these differences will be mainly described, and the contents overlapping with the method of the first embodiment will be briefly described.

(1) preparation step (S0):

The human body model P is selected and the target ROI to which the optimum shooting condition is to be searched is specified and the first reference value R1 _th and the second reference value R2 _th and a third reference value R3 _th to the controller 160. [

In the method (S100) of the first embodiment, the initial values of the tube voltage (kV), the tube current (mA), and the AEC threshold value are input as the initial imaging conditions. In the method S200 of the second embodiment, kV), tube current (mA), and initial values of the generator operation time of generator.

The input of the reference values and the initial values may be performed through the user interface 150.

(2) X-ray image acquisition (S210):

Next, the human body model P is photographed with the set tube voltage (kV), the tube current (mA), and the operation time of the generator to obtain an X-ray image of the human model (P).

At this time, the generator 110 provides the tube voltage (kV) and tube current (mA) set in the X-ray irradiator 120, and the controller 160 controls the generator switch 111 when the shooting time corresponding to the set generator operating time has elapsed OFF state, thereby stopping the X-ray irradiation.

The control unit 160 obtains an X-ray image (raw image) of the human body model P using the detection signal provided from the X-ray sensor 130 and displays the obtained X-ray image on the display unit 170.

(3) the human model (P) received Radiation dose ( σ _total ) (S220):

Next, the control unit 160 calculates the dose (? _Total ) received by the human body (P). This step S220 is performed in the same manner as in step S120 of the first embodiment.

(4) brightness distribution histogram and its Median ( MED ) And Full width (FWHM)  Calculation (S230):

Next, the control unit 160 obtains a brightness distribution histogram for the ROI and calculates a median MED and a full width half maximum FWHM of the histogram. This step S230 is performed in the same manner as the step S130 of the first embodiment.

As mentioned in the description of the first embodiment, a mean value or a mode value may be alternatively applied as a representative value representative of the brightness variables instead of the intermediate value, and as an indicator value indicating the scatter value, Alternatively, a full width variation or standard deviation may be applied.

(5) Calculated Median ( MED ), Full-width half width ( FWHM ) And The exposure dose (σ _total )this  It is determined whether the reference condition is satisfied (S240)

Next, the control unit 160 determines whether the calculated median value MED, full width at half maximum (FWHM), and exposure dose? _Total satisfy the reference condition.

This determination process proceeds in the same manner as described in step S140 of the first embodiment. That is, the controller 160 requests the first reference condition that the calculated median value MED be equal to or greater than the first reference value R1 _th , and the calculated FWHM FWHM is greater than or equal to the second reference value R2 _th It is determined whether the second reference condition and the calculated exposure dose? _Total satisfy the third reference condition that requires the third reference value R3 _th or less.

(6) If it is determined that all of the first to third reference conditions Not satisfied  , Steps S210 through S240 are repeated (S250):

As a result of the determination, if the calculated median value MED, full width at half maximum (FWHM), and exposure dose? _Total do not satisfy the first, second, and third reference conditions, If not, the controller 160 repeats steps S210 through S240 described above.

For example, in this repetitive execution, steps S210 to S240 are performed by applying shooting conditions in which other parameters (tube current, generator operation time) are maintained and tube voltage is gradually increased by a predetermined value in order to find a tube voltage satisfying the first reference condition Repeating steps S210 to S240 by applying shooting conditions in which other parameters (tube voltage and generator operation time) are maintained and tube currents are gradually increased by a predetermined value in order to find a tube current satisfying the second reference condition, The process of repeating steps S210 to S240 is repeated by applying the shooting conditions in which other parameters (tube voltage, tube current) are maintained and the generator operating time is gradually decreased by a predetermined value in order to find the generator operating time satisfying the third reference condition And so on.

(7) If it is determined that all of the first to third reference conditions Satisfied  , The optimum shooting condition is determined (S260)

If it is determined that all of the first to third reference conditions are satisfied, the control unit 160 determines the corresponding photographing condition as an optimal photographing condition and transmits the determined optimum photographing condition to the display unit 170 or the preset device (Not shown) to the user.

Here, the optimum shooting conditions consist of the optimal tube voltage, the optimum tube current, and the generator operation time, and the method of this embodiment is ended by outputting optimal values for each of these three parameters.

At the time of actual patient diagnosis, the user (e.g., photographer) performs X-ray photography for the patient after setting the tube voltage, the tube current, and the generator operation time through the user interface 170 such as the preset device. It is possible to prevent the X-ray dose exceeding the maximum allowable value (third reference value: _R3th ) from being exposed to the patient by applying the determined generator operation time, and also to prevent the tube voltage and the tube current or the tube voltage and the tube voltage determined in accordance with the above- By applying the tube current, it is possible to prevent the quality of the X-ray image from dropping below a certain level as the X-ray dose is limited.

The method of the second embodiment can determine the generator operation time for the digital retropitched X-ray imaging system without the AEC apparatus 140 and the digital X It can be particularly useful as a method for calibrating a new value suitable for a line sensor.

100: X-ray irradiator
120: X-ray irradiator
130: X-ray sensor
141: ionization chamber
P: sample

Claims (15)

(A10) obtaining an X-ray image of a human body model;
(A20) calculating an exposure dose? _Total for the model region in the X-ray image using a function relationship between pixel brightness and an exposure dose;
(A30) obtaining a histogram showing a pixel brightness distribution of a region of interest in the X-ray image, calculating a representative value representative of the variances of the histogram and an index value indicating a scattering degree of the histogram;
(A40) a first reference condition requiring the representative value to be equal to or greater than a first reference value, a second reference condition requiring the index value to be equal to or greater than a second reference value, and a requirement that the exposure dose? _{Total be} equal to or less than a third reference value Determining whether all of the third reference conditions are satisfied;
(A50) repeating the steps A10 to A40 under at least one different shooting condition if the first to third reference conditions are not all satisfied; And
(A60) determining an optimum photographing condition as a photographing condition satisfying all of the first to third reference conditions;
Optimal imaging conditions for X - ray imaging systems.
The method according to claim 1,
In step A20, the exposure dose? _Total is calculated by applying the following integral equation to the model area, and? (I) in the following integral equation is a function between the exposure dose to pixel brightness,

Optimal imaging conditions for X - ray imaging systems.
The method according to claim 1,
Wherein the parameters constituting the photographing condition include a tube voltage, a tube current, and an AEC threshold value,
Optimal imaging conditions for X - ray imaging systems.
The method of claim 3,
In step A50,
(A51) repeating the steps A10 to A40 with at least one shooting condition that varies only the tube voltage among the parameters until the first reference condition is satisfied;
(A52) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the tube current among the parameters until the second reference condition is satisfied; And
(A53) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the AEC threshold value among the parameters until the third reference condition is satisfied;
Optimal imaging conditions for X - ray imaging systems.
The method according to claim 1,
Wherein the parameters constituting the photographing condition include a tube voltage, a tube current, and a generator operation time,
Optimal imaging conditions for X - ray imaging systems.
6. The method of claim 5,
In step A50,
(A55) repeating the steps A10 to A40 with at least one shooting condition that varies only the tube voltage among the parameters until the first reference condition is satisfied;
(A56) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the tube current among the parameters until the second reference condition is satisfied; And
(A57) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the generator operation time among the parameters until the third reference condition is satisfied;
Optimal imaging conditions for X - ray imaging systems.
The method according to claim 1,
The representative value is a median, a mean value, or a mode value,
Wherein the indicator value is a full width half maximum (FWHM), variation, or standard deviation,
Optimal imaging conditions for X - ray imaging systems.
A generator 110;
An X-ray irradiating unit 120 for receiving X-rays from the generator 110 and applying X-rays to the artificial model P;
An X-ray sensor 130 for detecting X-rays transmitted through the artificial model P; And
And a control unit (160) connected to the generator (110) and the X-ray sensor (130)
The control unit 160,
(A10) obtaining an X-ray image of the human body (P);
(A20) calculating an exposure dose? _Total for the model region in the X-ray image using a function relationship between pixel brightness and an exposure dose;
(A30) obtaining a histogram showing a pixel brightness distribution of a region of interest in the X-ray image, calculating a representative value representative of the variances of the histogram and an index value indicating a scattering degree of the histogram;
(A40) a first reference condition requiring the representative value to be equal to or greater than a first reference value, a second reference condition requiring the index value to be equal to or greater than a second reference value, and a requirement that the exposure dose? _{Total be} equal to or less than a third reference value Determining whether all of the third reference conditions are satisfied;
(A50) repeating the steps A10 to A40 under at least one different shooting condition if the first to third reference conditions are not all satisfied; And
(A60) determining an optimum photographing condition as a photographing condition satisfying all of the first to third reference conditions;
X-ray system.
9. The method of claim 8,
The control unit 160 calculates the exposure dose? _Total by applying the following integral equation to the model region, and? (I) in the following integral formula represents a function between the exposure dose to the pixel brightness,

X-ray system.
9. The method of claim 8,
The AEC 110 detects the total amount of X-rays transmitted through the human body P and automatically cuts off the electrical connection between the generator 110 and the X-ray irradiating unit 120 when the total amount of X-rays reaches the AEC threshold value Further comprising a device (140)
X-ray system.
11. The method of claim 10,
Wherein the parameters constituting the photographing condition include a tube voltage, a tube current, and an AEC threshold value,
X-ray system.
12. The method of claim 11,
When the control unit 160 performs step A50,
(A51) repeating the steps A10 to A40 with at least one shooting condition that varies only the tube voltage among the parameters until the first reference condition is satisfied;
(A52) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the tube current among the parameters until the second reference condition is satisfied; And
(A53) repeating the steps A10 to A40 in one or more shooting conditions that differ only in the AEC threshold value among the parameters until the third reference condition is satisfied;
X-ray system.
9. The method of claim 8,
Wherein the parameters constituting the photographing condition include a tube voltage, a tube current, and a generator operation time,
X-ray system.
14. The method of claim 13,
When the control unit 160 performs step A50,
(A55) repeating the steps A10 to A40 with at least one shooting condition that varies only the tube voltage among the parameters until the first reference condition is satisfied;
(A56) repeating the steps A10 to A40 with one or more shooting conditions that differ only in the tube current among the parameters until the second reference condition is satisfied; And
(A57) repeating the steps A10 to A40 in one or more shooting conditions that differ only in the generator operation time among the parameters until the third reference condition is satisfied;
X-ray system.
9. The method of claim 8,
The representative value is a median, a mean value, or a mode value,
Wherein the indicator value is a full width half maximum (FWHM), variation, or standard deviation,
X-ray system.

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