KR102563892B1 - Method and Apparatus for Calibrating DOT(Diffuse Optical Tomography) - Google Patents

Abstract

The present invention relates to a method and apparatus for calibrating a diffused optical tomography image, and the calibration method in an apparatus for acquiring a diffused optical tomography image of the present invention includes fixing a calibration phantom having uniform absorption and scattering coefficients to a paddle, Irradiating light to transmit the calibration phantom using a light source, measuring the intensity and phase of light transmitted through the calibration phantom using a photodetector array, and measuring the intensity and phase of light transmitted through the calibration phantom for each location Comparing intensity and phase with reference values of light intensity and phase for each position, respectively, to calculate a sensitivity error for each position of the outputs of the photodetector array.

Description

Optical diffusion tomography calibration method and apparatus {Method and Apparatus for Calibrating DOT (Diffuse Optical Tomography)}

The present invention relates to a diffuse optical tomography (DOT) calibration method and apparatus, and more particularly, to a diffuse optical tomography (DOT) calibration method and apparatus for diagnosing breast cancer.

DBT/DOT (Digital Breast Tomosynthesis/Diffuse Optical Tomography) convergence imaging diagnosis equipment fuses 3D X-ray breast images and 3D diffusion optical images for breast cancer diagnosis to produce functional images that show the active state of lesions in the breast. It is a system that can effectively diagnose breast cancer by providing it at the same time. There are several important core technologies of DBT/DOT convergence imaging diagnostic equipment, but among them, the paddle that compresses and fixes the breast should be convenient not only when taking 3D X-ray images but also when taking 3D diffuse optical images. do.

In particular, in order to obtain a DOT image of a measurement object such as the breast, a fixed paddle that fixes the breast is composed of light sources at regular intervals and detectors at regular intervals. By using an optical switch to sequentially transmit light to each position, signal processing for the same frequency component is enabled. At this time, since different light sources and different detectors are used for each location to obtain a DOT image, the intensity of each light source and the sensitivity of each detector are different even if the intensity of each light source is adjusted and a detector with the same specification is used. appear. Accordingly, a calibration that properly compensates for sensitivity errors of the detectors must be performed by individually measuring a plurality of light sources and detectors.

1 is a diagram for explaining errors in a DOT image according to detection errors of intensity and phase of transmitted light at each detector position in a conventional breast cancer diagnosis apparatus.

First, as shown in FIG. 1, looking at the sensitivity of each detector for a single light source, when incident light from an X-ray light source passes through a medium having a uniform absorption coefficient (μa) and scattering coefficient (μs'), transmitted light The intensity (AMP) of should be the same as a constant distribution curve, such as 10, but is actually detected with a difference from the distribution curve at each position, such as 11. In addition, in the case of the phase (Phase), it should follow a constant distribution curve such as 20 in theory, but in practice, it is detected showing a difference from the distribution curve at each position, such as 21. The reason why the phase difference is not uniform for each detector is because the detector characteristics are not uniform and the lengths of radio frequency (RF) cables for signal processing are different. Therefore, an error in which the intensity and phase of such transmitted light are detected differently for each detector must be appropriately compensated.

In addition, even when a plurality of light sources 51, 52, and 53 are used as shown in FIG. 1, the intensity of each light source is different, and the intensity of the light source at each location is different, so the intensity of the actually measured detector is the same. Even if the detector of the specification is used, there is a problem that is different, such as 30, 31, and 32. In particular, since the detector is connected to an optical fiber for signal processing, there is a problem in that the amount of light transmitted along the optical fiber varies depending on the degree of bending of the optical fiber, resulting in a slight difference in detection each time the system is operated. Accordingly, it is absolutely fixed. There is a problem that calibration is impossible.

Therefore, there is a need for a calibration method that properly compensates for a sensitivity error of a detector simply and effectively in an existing breast cancer diagnosis system.
As related prior literature, Japanese Patent Publication No. 2014-533571 (2014.12.15.), Patent Publication No. 10-2015-0005700 (2015.01.14.), etc. can be referred to.

Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to use a single light source in a breast cancer diagnosis system without using the conventional complicated method of individually measuring and calibrating a plurality of light sources and detectors It is to provide a diffuse optical tomography (DOT) calibration method and apparatus capable of compensating for sensitivity errors of detectors at once as a whole.

In addition, even if the absorption coefficient and scattering coefficient are not known, if there is a uniform phantom, a diffused optical tomography (DOT) calibration method and device that can compensate for the sensitivity error of each detector by position using a single light source and a single detector is provided. is to do

First, to summarize the features of the present invention, a calibration method in an apparatus for obtaining an optical diffusion tomography image according to an aspect of the present invention for achieving the above object is a paddle for a calibration phantom having uniform absorption and scattering coefficients. fixing to; irradiating light to pass through the calibration phantom using a light source; measuring an intensity and phase of light transmitted through the calibration phantom using a photodetector array; and comparing the intensity and phase of the light transmitted through the calibration phantom for each position with reference values for the intensity and phase of light for each position, respectively, to calculate a sensitivity error for each position of the outputs of the photodetector array.

In the calibration method, after calculating the sensitivity error, the optical diffusion tomography image is obtained by compensating for the sensitivity error with outputs of the photodetector array for an actual measurement object fixed to the paddle. do.

In the step of calculating the sensitivity error, the light intensity reference value and phase reference value for each position may be theoretically pre-calculated for the calibration phantom for which the absorption coefficient and scattering coefficient are known, and stored in a storage means.

Alternatively, when the absorption coefficient and the scattering coefficient are not known, before the step of calculating the sensitivity error, while moving one photodetector for each position, the light source is used to irradiate light to pass through the calibration phantom for the calibration A step of measuring the intensity and phase of light transmitted through the phantom and storing them in a storage unit in advance, and in the step of calculating the sensitivity error, the intensity and phase of the light measured using the one photodetector stored in the storage unit may be used as the intensity reference value and the phase reference value of the light.

And, an apparatus for obtaining an optical diffusion tomography image according to another aspect of the present invention includes a light source; a paddle including a photodetector array on one side and fixing the object; and a control device for controlling operations of the light source and the paddle, wherein the control device fixes a calibration phantom having uniform absorption and scattering coefficients to the paddle, and transmits the calibration phantom using the light source. light is irradiated so as to measure the intensity and phase of the light transmitted through the calibration phantom according to the output signal of the photodetector array, and the intensity and phase of the light transmitted through the calibration phantom for each position are reference values for the intensity of light for each position and a phase reference value, respectively, to calculate a sensitivity error for each position of the outputs of the photodetector array.

After calculating the sensitivity error, the apparatus for acquiring the optical diffusion tomography image compensates for the sensitivity error to outputs of the photodetector array for the actual object to be measured fixed to the paddle to compensate for the optical diffusion tomography image. It is characterized in that for obtaining.

The light intensity reference value and the phase reference value for each position may be theoretically calculated in advance for the calibration phantom for which the absorption coefficient and scattering coefficient are known, and stored in a storage means.

Alternatively, when the control device does not know the absorption coefficient and the scattering coefficient, while moving one photodetector for each position, the control device irradiates light so as to transmit the calibration phantom using the light source to transmit the calibration phantom. The intensity and phase of light may be measured and stored in a storage unit in advance, and the intensity and phase of light measured using the single photodetector stored in the storage unit may be used as reference values for the intensity and phase of light.

According to the optical diffusion tomography (DOT) calibration method and apparatus according to the present invention, optical diffusion is performed using a single light source in a complex breast cancer diagnosis system by using a calibration phantom having uniform absorption and scattering coefficients, even if it is not a conventional complicated method. It is possible to effectively compensate for sensitivity errors of all detectors at once by performing calibration for obtaining a tomographic image (DOT).

In addition, even if the absorption coefficient and the scattering coefficient are not known, if there is a uniform phantom, the sensitivity error of each detector can be compensated for by position simply by using a single light source and a single detector.

1 is a diagram for explaining errors in a DOT image according to detection errors of intensity and phase of transmitted light at each detector position in a conventional breast cancer diagnosis apparatus.
2 is a schematic diagram of a breast cancer diagnosis apparatus for obtaining a DOT image according to an embodiment of the present invention.
3 is a diagram for explaining an example of a DOT calibration method in the breast cancer diagnosis apparatus of the present invention.
4 is a diagram for explaining another example of a DOT calibration method in the breast cancer diagnosis apparatus of the present invention.
5 shows an actual example of a phantom, measurement target, and DOT image applied to the breast cancer diagnosis apparatus of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. At this time, the same components in each drawing are represented by the same reference numerals as possible. In addition, detailed descriptions of already known functions and/or configurations will be omitted. In the following description, parts necessary for understanding operations according to various embodiments will be mainly described, and descriptions of elements that may obscure the gist of the description will be omitted. Also, some elements in the drawings may be exaggerated, omitted, or schematically illustrated. The size of each component does not entirely reflect the actual size, and therefore, the contents described herein are not limited by the relative size or spacing of the components drawn in each drawing.

2 is a schematic diagram of a breast cancer diagnosis apparatus 100 for obtaining a DOT image according to an embodiment of the present invention.

Referring to FIG. 2 , an apparatus for diagnosing breast cancer for obtaining a DOT image according to an embodiment of the present invention 100 includes one or more light sources 60 and a photodetector array 70 on one side of an object (eg, a phantom). , a sample tissue, a measurement object such as a breast), a paddle 65 for fixing, and a control device 69 for controlling the overall operation of the device 100, such as the light source 60 and the paddle 65. can

For example, the paddle 65 may fix an object (eg, a phantom, a sample tissue, or a measurement object such as a breast) between the first plate 62 and the second plate 63 . The object may be compressed between the first plate 62 and the second plate 63, and in the second plate 63, a photodetector array in which a CCD (Charge Coupled Device) is arranged in one dimension or two dimensions. (70) may be provided. The light source 60 generating light (or electromagnetic waves) such as X-rays may be provided outside the paddle 65 or may be provided inside the first plate 62 . The light source 60 may be one or plural.

The controller 69 sets the calibration phantom 80 with a uniform absorption coefficient (μa) and scattering coefficient (μs') to the paddle 65 to compensate for the sensitivity error with respect to the outputs of the photodetector array 70. ), the light source 60 is used to transmit light to pass through the calibration phantom 80, and the intensity and phase of the light transmitted through the calibration phantom 80 according to the output signal of the photodetector array 70 to measure The control device 69 compares the intensity and phase of light transmitted through the calibration phantom 80 for each position of the Guam detectors of the photodetector array 70 with reference values for the intensity and phase of light for each position, respectively, to obtain a photodetector A sensitivity error for each position of the outputs of the array 70 may be calculated.

As described below, the light intensity reference value and the phase reference value for each position as shown in FIG. 3 are theoretically calculated in advance for the calibration phantom 80 for which the absorption coefficient (μa) and the scattering coefficient (μs') are known, and stored in memory. It may be a value previously stored in the storage means.

Alternatively, as shown in FIG. 4, when the absorption coefficient (μa) and the scattering coefficient (μs') are not known, values measured using only one photodetector instead of the photodetector array 70 during light irradiation by the light source 60 It may also be used as the intensity reference value and the phase reference value for each position as described above.

For example, when the absorption coefficient (μa) and the scattering coefficient (μs') are not known, the controller 69 uses the light source 60 while moving one photodetector in the second plate 63 position by position. Then, light is irradiated to pass through the calibration phantom 80, and the intensity and phase of the light transmitted through the calibration phantom 80 are measured and stored in a storage means such as a memory in advance. In this way, since the intensity and phase of light for each position stored in the storage means are measured using the same light source 60 and the same photodetector, they are similar to the theoretical values for each position, and accordingly, this is the control device 69 ), it can be used as the intensity reference value and phase reference value of light as above. To this end, a movable photodetector is mounted in the second plate 63, and the above measurement can be performed while manually or automatically moving the photodetector.

In this way, the intensity and phase of the light transmitted through the calibration phantom 80 for each position of the Guam detectors of the photodetector array 70 are compared with the intensity reference value and the phase reference value for each position, respectively, and the photodetector array ( After calculating the sensitivity error for each position for the outputs of 70), the control device 69 outputs the photodetector array 70 for the actual measurement object fixed to the paddle 65 instead of the phantom 80 for calibration. For , it is possible to obtain an optical diffusion tomography image without a sensitivity error by compensating for the sensitivity error in a method such as subtracting the sensitivity error.

Hereinafter, a method for compensating a sensitivity error for each position with respect to the outputs of the photodetector array 70 will be described in more detail with reference to FIGS. 3 to 5 .

3 is a diagram for explaining an example of a DOT calibration method in the breast cancer diagnosis apparatus 100 of the present invention.

First, with respect to the positional relationship between the light source 60 and the photodetector array 70, theoretically, with respect to the uniform calibration phantom 80 for which the absorption coefficient (μa) and the scattering coefficient (μs') are known, the intensity of light for each position A reference value and a phase reference value are calculated in advance and stored in a storage means such as a memory. In the case of a uniform calibration phantom (80) with known absorption coefficient (μa) and scattering coefficient (μs'), a simple transfer simulation or analytic function is used to determine how light is scattered and transmitted to the photodetector array (70 ) can be theoretically calculated accurately whether it reaches each photodetector (detector).

Next, the control device 69 fixes the uniform calibration phantom 80, of which the absorption coefficient (μa) and the scattering coefficient (μs') are known, to the paddle 65, and uses the light source 60 for calibration. Light is irradiated so as to transmit through the phantom 80 (110). The controller 69 may measure the intensity and phase of light transmitted through the calibration phantom 80 according to the electrical signal output from the photodetector array 70 .

Accordingly, the control device 69 determines the intensity and phase of the light transmitted through the calibration phantom 80 for each position of the Guam detectors of the photodetector array 70, the intensity reference value and the phase reference value for each position stored in the storage means, and By comparing each, a sensitivity error for each position of the outputs of the photodetector array 70 may be calculated.

In this way, after calculating the sensitivity error for each position of the outputs of the photodetector array 70, the control device 69 instead of the phantom 80 for calibration is fixed to the paddle 65. With respect to the outputs of the photodetector array 70 for the actual object to be measured 90, etc., it is possible to obtain an optical diffusion tomography image without a sensitivity error by subtracting the sensitivity error as described above (120). .

4 is a diagram for explaining another example of a DOT calibration method in the breast cancer diagnosis apparatus of the present invention.

Referring to FIG. 4 , first, the control device 69 controls the uniform calibration phantom 80 of unknown absorption coefficient (μa) and scattering coefficient (μs') to be fixed to the paddle 65.

When the absorption coefficient (μa) and the scattering coefficient (μs') are not known, the value measured using only one photodetector instead of the photodetector array 70 during light irradiation by the light source 60 is the reference value of the intensity of light for each position as above. And it can be used as a phase reference value.

To this end, a movable photodetector is mounted in the second plate 63 and manually moved to the positions of the photodetector array 70, or automatically moved according to the control of the control device 69. While moving the photodetector to the detector positions of the photodetector array 70, the intensity reference value and the phase reference value for each position may be measured (210). In order to manually or automatically move the photodetector, various methods such as a method of moving the photodetector along a predetermined guide rail may be used.

For example, the control device 69 moves one photodetector provided in the second plate 63 to the detector positions of the photodetector array 70 and uses the light source 60 to generate a calibration phantom ( 80), the intensity and phase of the light transmitted through the calibration phantom 80 may be measured and stored in advance in a storage means such as a memory. In this way, since the intensity and phase of light for each position stored in the storage means are measured using the same light source 60 and the same photodetector, they are similar to the theoretical values for each position, and accordingly, this is the control device 69 ) can be used as the intensity reference value and the phase reference value for each detector position of the photodetector array 70.

In this way, after the light intensity reference value and the phase reference value for each detector position of the photodetector array 70 are stored in advance, the absorption coefficient ( A uniform calibration phantom 80 of unknown μa) and scattering coefficient (μs′) is controlled to be fixed (220).

Next, the control device 69 uses the light source 60 to control light to be transmitted through the calibration phantom 80, and the calibration phantom ( 80) can measure the intensity and phase of light transmitted through it. Accordingly, the control device 69 determines the intensity and phase of the light transmitted through the calibration phantom 80 for each position of the Guam detectors of the photodetector array 70, the intensity reference value and the phase reference value for each position stored in the storage means, and By comparing each, a sensitivity error for each position of the outputs of the photodetector array 70 may be calculated.

In this way, after calculating the sensitivity error for each position of the outputs of the photodetector array 70, the control device 69 instead of the phantom 80 for calibration is fixed to the paddle 65. With respect to the outputs of the photodetector array 70 for the actual object to be measured 90, etc., it is possible to obtain an optical diffusion tomography image without a sensitivity error by subtracting the sensitivity error as described above (130). .

5 shows an actual example of a phantom, a measurement target, and a DOT image applied to the breast cancer diagnosis apparatus 100 of the present invention.

As shown in FIG. 5, after fabricating a uniform calibration phantom with unknown absorption coefficient (μa) and scattering coefficient (μs'), calibration was performed in the same way as above, and some defects (eg, grooves or holes, etc.) were made. An optical diffusion tomography image was reconstructed based on the outputs of the photodetector array for the object to be measured. That is, by compensating for the outputs of the photodetector array for the object to be measured by subtracting the detector sensitivity error of the photodetector array of the present invention, clear optical diffusion is obtained without being affected by the sensitivity error, as in the image restoration example of the drawing. It was confirmed that tomography images could be acquired.

As described above, by obtaining a diffused optical tomography image after calibration through the apparatus 100 for acquiring a diffused optical tomography (DOT) according to the present invention, even if the absorption coefficient and scattering coefficient are uniform without the conventional complicated method, calibration Using the phantom, it is possible to compensate sensitivity errors of all detectors at once by performing calibration for DOT acquisition using a single light source in a complex breast cancer diagnosis system. In addition, even if the absorption coefficient and the scattering coefficient are not known, if there is a uniform phantom, the sensitivity error of each detector can be compensated for by position simply by using a single light source and a single detector.

As described above, the present invention has been described by specific details such as specific components and limited embodiments and drawings, but these are provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. , Those skilled in the art in the field to which the present invention belongs will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the spirit of the present invention should not be limited to the described embodiments, and all technical ideas having modifications equivalent or equivalent to these claims as well as the claims to be described later are included in the scope of the present invention. should be interpreted as

light source(60)
Photodetector Array (70)
Paddle (65)
Controller(69)

Claims (8)

In the calibration method using a control device in a breast cancer diagnosis device for obtaining an optical diffusion tomography image,
Controlling, by the controller, fixing the phantom for calibration to the paddle;
irradiating, in the controller, light to pass through the calibration phantom using a light source;
measuring the intensity and phase of light transmitted through the calibration phantom using a photodetector array including photodetectors disposed at different distances from the light source in the control device; and
Comparing, in the controller, the intensity and phase of the light transmitted through the calibration phantom for each position with reference values for the intensity and phase of light for each position, respectively, to calculate a sensitivity error for each position of the outputs of the photodetectors.
Calibration method including. According to claim 1,
After calculating the sensitivity error, the controller compensates the sensitivity error for the outputs of the photodetectors for the actual measurement object fixed to the paddle to obtain the optical diffusion tomography image. Calibration method. According to claim 1,
In the step of calculating the sensitivity error,
The calibration method, characterized in that the light intensity reference value and phase reference value for each position are theoretically calculated in advance for the calibration phantom of which absorption coefficient and scattering coefficient are known and stored in advance in a storage means. According to claim 1,
When the absorption coefficient and the scattering coefficient are not known, before the step of calculating the sensitivity error, while moving one photodetector by the position, irradiating light so as to transmit the calibration phantom using the light source to transmit the calibration phantom Measuring the intensity and phase of one light and storing them in advance in a storage means;
In the step of calculating the sensitivity error, the intensity and phase of the light measured using the one photodetector stored in the storage means are used as the intensity reference value and the phase reference value of the light. light source;
a paddle including a photodetector array on one side and fixing the object; and
A control device for controlling the operation of the light source and the paddle,
The photodetector array includes photodetectors disposed at different distances from the light source;
After fixing the calibration phantom to the paddle, the control device irradiates light to pass through the calibration phantom using the light source, and determines the intensity of the light transmitted through the calibration phantom according to the output signals of the photodetectors. measure the phase,
The intensity and phase of the light transmitted through the calibration phantom for each position are compared with the intensity reference value and the phase reference value for each position, respectively, to calculate a sensitivity error for each position of the outputs of the photodetectors, obtaining an optical diffusion tomography image A breast cancer diagnosis device for According to claim 5,
After calculating the sensitivity error, the optical diffusion tomography image characterized in that for obtaining the optical diffusion tomography image by compensating for the sensitivity error to the outputs of the photodetectors for the actual measurement object fixed to the paddle A breast cancer diagnosis device for obtaining. According to claim 5,
The light intensity reference value and the phase reference value for each position are theoretically calculated in advance for the calibration phantom of which the absorption coefficient and the scattering coefficient are known, and are pre-stored in a storage means. According to claim 5,
When the absorption coefficient and the scattering coefficient are not known, the control device irradiates light to transmit the calibration phantom using the light source while moving one photodetector for each position, and determines the intensity and intensity of the light transmitted through the calibration phantom. The phase is measured and stored in advance in a storage means;
The apparatus for diagnosing breast cancer for obtaining an optical diffusion tomography image, characterized in that the intensity and phase of the light measured by the one photodetector stored in the storage means are used as reference values for the intensity and phase of the light.