WO2007108346A1 - 放射線画像処理方法、放射線画像処理装置及び放射線画像撮影システム - Google Patents
放射線画像処理方法、放射線画像処理装置及び放射線画像撮影システム Download PDFInfo
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- A—HUMAN NECESSITIES
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- A—HUMAN NECESSITIES
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/50—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications
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- G06T5/92—Dynamic range modification of images or parts thereof based on global image properties
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- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
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- G06T2207/30004—Biomedical image processing
- G06T2207/30061—Lung
- G06T2207/30064—Lung nodule
Definitions
- Radiation image processing method Radiation image processing apparatus, and radiation image capturing system
- the present invention relates to a radiographic image processing method, a radiographic image processing apparatus, and a radiographic image capturing system.
- Patent Document 1 it is easy to visually find a lesion by displaying a low-luminance or high-concentration image with a small amount of X-ray (radiation) transmission! Has been proposed.
- Patent Documents 2 to 4 a technique for using an X-ray image obtained by phase contrast imaging for medical treatment has been developed. According to this technique, the feature of the phase contrast image that emphasizes the boundary between the observation object and the background is used, even if the difference in the X-ray absorption rate between the observation object and the background is small. Can be detected.
- Patent Document 1 Japanese Translation of Special Publication 2005-509472
- Patent Document 2 JP 2001-91479 A
- Patent Document 3 Japanese Patent Laid-Open No. 2001-299733
- Patent Document 4 Japanese Patent Laid-Open No. 2001-311701
- the diameters of asbestos bodies and fiber bundles detected as asbestos are generally as small as 50 m or less, some of which are 10 m or less, and very few.
- detecting asbestos in an optical microscope is very labor and time consuming and very difficult to detect.
- even if X-ray images can be detected because X-ray absorption ability is low due to the fineness, the background of asbestos with little difference in density between the asbestos that is the observation target and the surrounding tissue that is the background. It is difficult to display images so that they can be identified. Even if an image can be obtained, there are many cases where a doctor cannot observe (judgment) due to noise appearing in the background. Thus, there is currently no reliable asbestos detection technology.
- Patent Document 1 The inversion process disclosed in Patent Document 1 is a technique for improving the visibility, but a sufficient difference in shade between the object to be observed and the background cannot be obtained! Therefore, the improvement of visibility is insufficient.
- the present invention provides a radiographic image processing method, a radiographic image processing apparatus, and a radiographic image capturing system that can detect even a minute observation object such as asbestos that has entered a human body. With the goal.
- the present invention makes it possible to provide sufficient contrast even for an observation object that is difficult to achieve contrast with the background. It is also possible to detect such a fine observation object.
- the radiation absorption rate of the observation object when irradiated with 20 keV radiation is not less than 0.0025% and not more than 2.5%.
- gradation processing using a gradation curve with a ⁇ value G of 20 or more and 30 or less is performed on an observation target having a low radiation absorption rate.
- a portion having a large radiation transmission amount has low luminance or low brightness during observation. Is displayed at a high concentration, and a reversal process is performed so that the small amount of radiation transmission region becomes high luminance or low concentration.
- Absorption rate of radiation when irradiated with 20 keV radiation is 0.20025% or more, 2.5
- a radiation image processing method characterized by performing inversion processing so that a large radiation transmission amount region is displayed at a low density or high luminance and a small radiation transmission amount region is displayed at a high concentration or low luminance during observation. .
- the radiographic image processing method according to 1 or 2 above, wherein the radiographic image data is obtained by performing phase contrast imaging.
- Absorption rate of radiation when irradiated with 20 keV radiation is 0.20025% or more, 2.5 A gradation processing means for performing gradation processing using a gradation curve with a ⁇ value G of 20 or more and 30 or less for radiation image data obtained by irradiating a subject with less than%
- a radiation image characterized by having a reversal processing means for performing a reversal process so that a large radiation transmission amount portion is displayed at a low density or high luminance and a small radiation transmission amount portion has a high density or low luminance. Processing equipment.
- a region of interest designating unit that designates a region of interest in the radiographic image data; and gradation processing by the tone processing unit for the radiation image data of the region of interest designated by the region of interest designating unit; 6.
- the radiographic image processing apparatus according to 5, wherein the inversion processing is performed by the inversion processing means.
- a radiographic imaging system comprising the radiographic image processing apparatus according to 5 or 6 above.
- FIG. 1 is a block diagram of an X-ray imaging system according to an embodiment of the present invention.
- FIG. 2 is a diagram showing a configuration of an X-ray imaging apparatus according to an embodiment of the present invention.
- FIG. 3 is a diagram illustrating phase contrast imaging.
- FIG. 4 is a diagram for explaining a phase contrast effect (edge effect).
- FIG. 5 is a diagram showing the relationship between edge strength and blur in the edge effect.
- FIG. 6 is a diagram for explaining a case where blur occurs in the phase contrast effect.
- FIG. 7 is a flowchart showing an example of the flow of image processing executed in the PCR image processing means.
- FIG. 8 is a diagram showing an example of a basic LUT used in the gradation conversion processing according to the present embodiment.
- FIG. 9 is a diagram showing a correspondence relationship between signal values in gradation conversion processing according to the present embodiment.
- FIG. 10 is a diagram for explaining inversion processing.
- FIG. 11 is a diagram showing an example of a display screen in the display device.
- the human body structure is mainly composed of elemental forces such as C, H, 0, and Ca !, while asbestos is mainly composed of elements such as Si, 0, Fe, and Mg.
- elemental forces such as C, H, 0, and Ca !
- asbestos is mainly composed of elements such as Si, 0, Fe, and Mg.
- Asbestos is often inhaled through the mouth and present in the alveoli.
- the alveolar constituent elements are mainly C, H, 0, N, etc.
- the difference is more than 10 times. Therefore, when the same X-ray dose is applied to the human body, the difference in X-ray dose reaching the X-ray detector is large and the contrast (concentration difference) on the X-ray image data is also large.
- the X-ray image data obtained by imaging the chest is set so that the bone, alveolar part, and pulmonary blood vessel part having a large difference in X-ray absorption rate are easily read at the same time.
- the upper tone characteristics are adjusted.
- the diameter of asbestos bodies and fiber bundles detected as asbestos is generally 50 m or less, and some are 10 m or less.
- the difference in the X-ray dose reached between the asbestos and the alveolar tissue, which has a low X-ray absorption rate is relatively small! In the image area, sufficient contrast cannot be obtained.
- the boundary part cannot be identified.
- enlargement imaging is performed by controlling the focal diameter and magnification of the X-ray tube used during imaging.
- the X-ray is highly visible by applying gradation processing and inversion processing, which are image processing unique to digital processing in response to asbestos detection, to digital X-ray image data obtained by enlarging photography. Generate image data.
- Asbestos as an observation object is preferably one having a diameter in the X-ray transmission direction of 0.05 ⁇ m or more and 50 ⁇ m or less. More preferably, they are 0.1 m or more and 50 m or less, More preferably, they are 1 micrometer or more and 10 m or less.
- the lower limit of the diameter is determined according to the resolution of the X-ray detector, and the upper limit of the diameter is the high signal value of the signal of the observation object in the contrast between the observation object and the background on the obtained X-ray image data. It is determined to the extent that it is not saturated on the low signal value side.
- the X-ray absorption rate will be described.
- the X-ray absorptance of the observation object when irradiated with 20 keV X-rays (radiation rays) is set to 0.0025% or more and 2.5% or less.
- the X-ray absorption rate is 0.05% or more and 0.5% or less. More preferably, when SiO, which is the main component of asbestos, has a diameter of 0.05 to 50 m, 20 keV X
- the absorption rate of X-rays can actually be confirmed and approximated by the signal value of the digital X-ray detector.
- a digital X-ray detector is one that has a linear relationship between the incident X-ray dose and the output signal value (for example, a flat panel detector (FPD)).
- FPD flat panel detector
- the X-ray transmission amount T is represented by the following formula (A).
- the X-ray dose penetrating water is 90.5%, that is, the absorption rate is 9.5%, and the X-ray dose penetrating SiO is 99.5%. I.e.
- the absorption rate is 0.5%.
- the signal value 1000 is obtained by X-rays irradiated on the subject, the signal value 905 is obtained in a place where water exists. A signal value of 995 is obtained where Si 2 O is present. Also, 10 times X where there is no subject
- the X-ray of the subject can be obtained from the signal value obtained using the digital X-ray detector.
- the absorption rate can be obtained, and it can be verified whether or not the conditional force applicable to the present invention.
- the difference between the X-ray absorption rate of the observation object and the background X-ray absorption rate when irradiated with 20 keV X-rays is 0.003% or more and 5% or less, more preferably 0.03% or more and 0.5% or less.
- the absorption difference will be described.
- asbestos is actually covered with human tissue.
- the subject specimen is assumed to have 10 m of SiO in water.
- the transmittance difference D between the observation object and the background is expressed by the following formula (B).
- it can also be defined by the force absorption difference defined by the absorption rate.
- the preferable range of X-ray absorption at 20 keV is 0.003% or more and 5% or less, preferably 0.03% or more and 0.5% or less.
- Sign value difference 4 is obtained as image information as a contrast difference.
- the premise of water only However, if 10 times the X-rays are irradiated and a signal value of “10000” is obtained, SiO exists.
- the signal value 9960 is obtained at the place, and the signal value difference becomes ten times "40".
- the contrast ratio can be obtained if the substance and the thickness of the subject and surrounding parts (diameter, etc. for fibrous materials such as asbestos) are obtained, and then the absorption difference of the subject is obtained from there. It is possible to verify whether the condition is applicable to the present invention.
- the attenuation coefficient of each substance can be obtained even by changing the force X-ray energy defined by the absorptance at 20 keV (for example, SiOke of 30 keV).
- the present invention can cope with imaging using various X-ray energies that are not only applicable to imaging using 20 keV X-rays.
- FIG. 1 is a block diagram showing an X-ray imaging system according to an embodiment of the present invention.
- the control unit 2 is a part that controls the entire system, and according to various setting conditions input by the input means 27, X-ray imaging corresponding to various imaging conditions and X-rays obtained by the X-ray imaging. Image processing is performed on the image data. That is, the control unit 2 has a function as an image processing apparatus according to the present invention.
- Typical examples of the various imaging conditions include normal imaging, in which the subject W and the X-ray detection hand 40 are in close contact, and phase contrast, in which the X-ray detection hand 40 is separated from the subject W and enlarged shooting is performed. There is shooting.
- the subject W is a specimen that is a part of the patient's body (for example, lungs) or a part of the tissue extracted from the patient's physical force, which is assumed to have asbestos to be observed.
- the CPU 11 controls the entire system.
- the image processing unit 12 includes a PCR (Phase Contrast Radiography) image processing unit 13 and a normal image processing unit 14. PCR images
- the processing means 13 processes X-ray image data obtained by phase contrast
- the normal image processing means processes normal X-ray image data, that is, X-ray image data obtained by close-contact imaging.
- Reference numeral 15 denotes imaging information storage means for storing imaging information such as gradation curve data in image processing.
- the output unit 28 outputs the X-ray image data processed in the control unit 2 so that a user such as a doctor can visually observe the image.
- the output unit 28 records an image on an image recording medium such as a film.
- the display means for displaying an image on the display or the communication means is a communication means for transmitting X-ray image data to the outside via a network.
- the X-ray generation source 30 is not limited to the control by the force control unit 2 controlled by the control unit 2. X-ray force radiated from the X-ray source 30 Transmits through the subject W and irradiates the X-ray detector 40. Details of the X-ray generation source 30 will be described later.
- the X-ray detector 40 receives X-rays and outputs an analog signal, and an FPD (Flat Panel Dtector), a detection unit using a stimulable phosphor, or the like is used. Details of the X-ray detector 40 will be described later.
- FPD Full Panel Dtector
- phase contrast imaging is performed as described below.
- the present invention is not limited to phase contrast imaging, and the object W and the X-ray detection unit 40 are not limited to phase contrast imaging. It can be done by processing the image data generated by normal shooting.
- FIG. 2 shows an appearance of the X-ray imaging apparatus 1 in the present embodiment that performs phase contrast imaging.
- the X-ray imaging apparatus 1 is configured to include an X-ray generation source 30 and an X-ray detector 40, and X irradiated from the X-ray generation source 30 toward the subject W
- the line is detected by the X-ray detector 40, and the output signal is digitally converted by the AD converter 41 to generate digital data of the X-ray image.
- subject W and X-ray source 30, subject W and X-ray detector Zoom in with magnification factor M by adjusting the distance R1 and R2 between 40.
- the X-ray generation source 30 generates X-rays from the focal point and irradiates the subject W, and the size thereof is referred to as a focal diameter D (m).
- a focal diameter D In the X-ray source 30, generally, the larger the focal diameter D, the larger the X-ray dose irradiated within a certain time.
- an X-ray tube having a rotating anode constituting the X-ray generation source 30 As an X-ray tube having a rotating anode constituting the X-ray generation source 30, an Mo tube, an Rh tube, a W tube, or the like is used. However, in phase contrast imaging, the tube has a small focal diameter. A high output X-ray source is desirable. One example of increasing the output is that the electron beam irradiated to the rotating anode (target) hits the same position on the concentric circle of the rotating anode. If you move one by one, you can think of a way.
- the X-ray detector 40 is configured such that its height position can be adjusted according to the imaging region.
- the X-ray detector 40 detects irradiated X-rays.
- a volatile phosphor plate is applied as the X-ray detector 40, the volatile phosphor plate is irradiated with excitation light such as laser light, and the volatile light emitted from the phosphor plate is photoelectrically converted into an image signal.
- a reading unit for conversion is provided in the X-ray detector 40, and the reading unit outputs a read signal.
- the X-ray detector 40 is an FPD
- conversion elements that generate an electric signal according to the incident X-ray dose are arranged in a matrix, and the electric signal is generated directly in the X-ray detector 40.
- FPD When FPD is applied, the electrical signal is AD converted in the FPD and the obtained digital X-ray image data is output to the control unit 2.
- phase contrast imaging by the X-ray imaging apparatus 1 will be described.
- FIG. 3 is a diagram for explaining the outline of phase contrast imaging.
- an X-ray detector 40 is disposed at a position in contact with the subject W (close-contact imaging position in FIG. 3) and irradiated from the X-ray generation source 30. It is configured to receive X-rays and take close contact images.
- the obtained X-ray image data is approximately the same size as the life size (which means the same size as the subject W).
- the X-ray detector 40 is arranged so as to provide a distance between the subject W and the X-ray detector 40.
- X-ray image data hereinafter referred to as “enlarged image data” force S that is enlarged with respect to the life size is obtained by the X-rays irradiated in a shape.
- the X-rays that are bent by passing through the edge of the subject W overlap with the X-ray detector 40 on the X-ray detector 40.
- the X-ray intensity of the overlapped part increases.
- a phenomenon occurs in which the X-ray intensity is weakened in the portion inside the edge of the subject W by the amount of refracted X-rays. Therefore, an edge enhancement function (also called an edge effect) that widens the X-ray intensity difference at the border of the subject W works to obtain highly visible X-ray image data in which the border is sharply depicted. Can do.
- the X-ray generation source 30 is regarded as a point source (that is, the focal point a is a point)
- the X-ray intensity at the edge portion is as shown by the solid line in FIG. E shown in Fig. 5 represents the full width at half maximum for edge emphasis and can be calculated by the following equation (2).
- the full width at half maximum E indicates the distance between the peaks and valleys of the edge.
- Coolidge X-ray tubes also called thermoelectric X-ray tubes
- the focal point diameter D increases to some extent, so it cannot be regarded as an ideal point source.
- the half-width E of edge enhancement is widened and the strength is lowered, resulting in geometrical sharpness. This geometrical sharpness is called blur.
- the X-ray intensity at the edge portion is as shown by a dotted line in FIG.
- the half-width of edge enhancement when blurring occurs is an ideal dotted line due to geometrical sharpness It will be wider than the edge emphasis width E when the source is assumed. If the half-width of the edge emphasis when this blur occurs is EB, EB can be obtained from the following equation (3).
- the distance R2 can be increased from Equation 1, but an increase in the distance R2 will cause an increase in the half-value width EB of the blur.
- the diameter of the object to be photographed is s (m).
- the diameter s is the diameter of the circumscribed circle when the object is not a deformed object such as a substantially spherical shape or a substantially cube, and the extension direction of the deformed object (elongated direction) when the object is a deformed object such as a thread-like elongated object.
- the irradiation field power becomes small, and only a part of the subject W can be photographed.
- the distance R3 when the setting of the distance R3 is limited, such as in a photographing room, it is preferable to fix the distance R3 and change the ratio of the distances Rl and R2 within the fixed distance R3.
- R3 3.5 (m) is determined
- the distance R should be in the range of 1 ⁇ R3 ⁇ 4, and the relationship between the magnification ratio M and the visibility of the enlarged image should be observed empirically and experimentally within this range.
- the optimum distances R3, Rl and R2 can be determined.
- the degree of blur B depends largely on the focal diameter D. 0. 0
- increasing the focal spot diameter D increases the degree of blurring, resulting in no edge enhancement. It becomes an image.
- the focal diameter D of the X-ray generation source 30 is used when imaging a small observation object of 0.05 ⁇ s ⁇ 50 m).
- the focal diameter D of the X-ray generation source 30 is used when imaging a small observation object of 0.05 ⁇ s ⁇ 50 m).
- M the enlargement factor
- s the asbestos diameter (m)
- reading is performed with a reading pixel size P satisfying 2P ⁇ s XM + B. That is, at least two pixels are read in the image area of asbestos on the enlarged image data.
- P ⁇ s XM + B depending on the imaging phase at the time of reading, the signal strength of one asbestos image area may be detected across multiple pixels, and the signal intensity of the asbestos area may be impaired.
- the read data for at least one pixel (pixel) within the asbestos diameter is the signal value level corresponding to asbestos regardless of the imaging phase at the time of reading.
- FIG. 7 is a flowchart showing an example of the flow of image processing executed in the PCR image processing means 13.
- the irradiation field is recognized (step S1), and in the irradiation field recognized in step S1, the region of interest (ROI) to be subjected to gradation conversion processing and inversion processing is determined.
- Settings are made (Step S2), and tone conversion processing (Step S3), inversion processing (Step S4), and frequency enhancement processing (Step S2) are performed on the image data corresponding to the region of interest set in Step S2. S5) is executed.
- step S 1 Details of the irradiation field recognition processing in step S 1 shown in FIG. 7 will be described.
- the X-ray image data of the irradiation field area can be used to perform image processing of the part required for diagnosis of the irradiation field area. It will not be done properly.
- X-ray image data Thus, before image processing, irradiation field recognition is performed to discriminate between the irradiation field region and the irradiation field region.
- any method of irradiation field recognition may be employed.
- the enlarged image data is divided into a plurality of small areas, and a dispersion value is obtained for each divided area, and an edge of the irradiation field area is detected based on the obtained dispersion value.
- the irradiation field region may be determined.
- the X-ray dose is almost uniform in the field outside the field, so the dispersion value in that small area is small.
- the reached X-ray dose is large, and the part (outside the irradiation field area) and the object X-ray dose cover by the subject, the part that is somewhat reduced (the irradiation field area) are mixed.
- the dispersion value becomes large. Therefore, assuming that an edge is included in a small area having a variance value greater than a certain value, an area surrounded by such a small area is determined as an irradiation field area.
- step S2 Details of the region-of-interest setting process in step S2 shown in FIG. 7 will be described.
- the recognized irradiation field region determines the X-ray image data level distribution when converting the X-ray image data distribution to a desired level distribution. Is set in the area. By determining a representative value of the X-ray image data force in the region of interest and converting the representative value to a desired level, X-ray image data of a desired level can be obtained.
- This region of interest is not limited to being equal to the irradiation field region.
- an area such as a circle or a rectangle is set at the center of the irradiation field area. It is good also as what to do.
- the circular or rectangular region is set as the diameter of the circle or the length force of one side of the rectangle, for example, “1Z2 to 1Z5” of the long side, short side, or diagonal line of the irradiation field region.
- an arbitrary region of interest may be set by an operation input means (not shown).
- a region of interest corresponding to a predetermined human body structure may be set in the irradiation field region.
- X-ray image data is scanned in the horizontal and vertical directions sequentially. Create a signal value profile.
- the lung field shows a higher value than the surrounding organs such as the trachea and thoracic vertebra, so the inflection point is detected in the profile, and the area of the lung field is determined by the position of this inflection point. Is identified. Any method may be applied to detect lung fields and asbestos fibers by pattern matching.
- a histogram of the specified lung field region is created.
- values at predetermined ratios from the maximum value side and the minimum value side are respectively set to the maximum reference value H and the minimum reference value.
- the maximum reference value H and the minimum reference value L are used as reference values for converting the signal value range of the enlarged image immediately after generation into the signal value range (maximum value SH, minimum value SL) in the output image. .
- step S3 Details of the gradation conversion processing in step S3 shown in FIG. 7 will be described.
- the gradation conversion process is a process for adjusting the density and contrast when outputting an image.
- the gradation conversion processing is performed in two stages: (1) normalization processing and (2) conversion processing using a basic LUT (lookup table), so that the desired signal value range and gradation characteristics are finally obtained.
- gradation conversion is performed.
- the gradation characteristic obtained by the screen Z film method is an S-shaped curve as shown in FIG.
- an LUT showing this gradation characteristic is prepared as a basic LUT, individual signal adjustments are performed on the target image by normalization processing, and signal values are converted using this basic LUT. .
- FIG. 9 shows the X-ray amount detected by the image detector 40 (in the case of the stimulable phosphor plate) and the signal value of the X-ray image data finally output in accordance with the X-ray amount. Show the relationship.
- the first quadrant shows the reading characteristics, and it reaches the image detector 40 X
- the relationship between the dose and the read signal value is shown.
- the second quadrant shows the normalization characteristics, and shows the relationship between the read signal value and the normalized signal value (digital signal value) after normalization.
- the third quadrant shows the tone conversion characteristics, and shows the relationship between the normalized signal value and the output density value (digital density signal value) converted by the basic LUT.
- the output density value is a 12-bit resolution from 0 to 4095.
- the range of the output value (size between SH and SL) can be adjusted by changing the slope of the straight line indicating the normality characteristic, and the contrast of the entire image is changed. Can be made. This slope is the ⁇ value.
- the overall output value range can be adjusted (SH-SL movement), thereby changing the density of the entire image. Let this intercept be the S value.
- the density range and contrast of the output image can be adjusted by controlling the slope ⁇ value and intercept S value of the straight line indicating the gradation characteristics as gradation conversion parameters.
- the ⁇ value G is determined by the following equation (4) for obtaining the slope of the gradation characteristic curve in the screen-film method shown in FIG.
- G (D2-D 1) / (logE2-logE 1) ⁇ ⁇ ⁇ ⁇ (4)
- D1 0.25 + Fog
- D2 2.0 + Fog
- Fog 0.2
- El and E2 are the incident X-ray doses corresponding to D2 and Dl, respectively.
- a ⁇ value G of about 2.0 to 3.5 is often used.
- QR the quantization region value
- P2 is the actual X-ray dose of the pixel whose output density is 1.2 in the image after gradation conversion.
- the PI value is uniquely determined by the setting of the quantization region QR value before imaging.
- the above is the content of the normal gradation processing.
- the contrast of the aspect is increased in order to improve the visibility of asbestos by focusing on the low contrast of the output image.
- it is necessary to raise the ⁇ value regardless of the above equation (4).
- the symbol hi represents the X-ray histogram for the lung field where asbestos is present. Asbestos has very low contrast and its signal width is narrow. Therefore, instead of assigning the output density range to the signal width of the entire histogram, it is assigned to a narrow area that is the signal band of the relevant best, and the ⁇ value G is set to 20 or more to improve the contrast of the asbestos image. It is preferable. More preferably, the ⁇ value G is selected from a value in the range of 20-30.
- the ⁇ value G is lower than 20, the difference in density or luminance between the image of the observation object and the background image becomes low, making it difficult to detect the observation object.
- step S4 Details of the reversal processing in step S4 shown in FIG. 7 will be described.
- the inversion process is performed by the image processing means 12 as the inversion processing means.
- the X-ray image data has a so-called negative in which the X-ray transmission amount has a high signal value and the X-ray transmission amount has a low signal value. It is an image Therefore, the inversion process is a negative / positive inversion process. As shown in FIG. 10, the inversion processing is performed for the output DTout, that is, the high DTin in which the negative polarity is inverted with respect to the X-ray image data DTin output after gradation processing in step S3 shown in FIG. The processing is performed so that the low DTout is output and the high DTout is output for the low DTin.
- the gradation curve CV shown in FIG. 8 uses the inverted gradation curve (CV ′) in FIG. 10 which is inverted up and down around the center value ML (204 8 in 12-bit gradation). It is desirable to perform reverse processing.
- the inversion process may be performed simultaneously with the gradation conversion process. That is, by using the inversion gradation curve as shown in FIG. 10 as the gradation curve and performing the inversion gradation processing on the incident X-ray dose in FIG. 8, the gradation processing and the inversion processing can be performed simultaneously. Can do.
- the inversion process is the following process.
- an image of a portion with a low X-ray transmission amount transmitted through the subject W is expressed as a high-density portion or a low-intensity image portion at the time of observation, and an image of a portion with a high X-ray transmission amount is
- the inversion process creates X-ray image data that can be expressed as a low-density or high-intensity image area during observation.
- the discrimination ability in the high density part is generally higher than the discrimination ability in the low density part. Therefore, the reversal processing shown in FIG. 10 ensures that fine observation objects such as asbestos are also found.
- the density of the background (back) becomes low in the film output (the optical density of the film is about 0.5 to 1.5).
- This density area has a smaller slope in the gradation curve of the film than the density area of film density 1.5 to 3.0, and this suppresses background noise during film output to be lower than the high density. it can. Therefore, fine observation objects such as asbestos can be found reliably.
- inversion processing is performed for a so-called positive image in which a portion with a small amount of X-ray transmission has a high signal value and a portion with a large amount of X-ray transmission shows a low signal value.
- inversion processing instead of using the inversion gradation curve as shown in FIG. 10, a file of the international standard DICOM (digital information and communication in medicine) format for digitalization of medical images is used. It can also be realized by changing the attribute value.
- the DICOM format file is defined to show a negative image when the attribute value called “Photometric Interpretation” is “MONOCHROME I” and a positive image when it is “MONO CHROME II”.
- Step 7 If the attribute value “Photometric Interpretation” is set to “MO NOCHROME II” in the reversal processing of S4, X-ray transmission is small in DICOM-compliant display devices and output devices! /, The part has high brightness or low density and large X-ray transmission! Thus, a positive image in which the part has low luminance or high density is output.
- the frequency enhancement processing technique includes a technique for performing unsharp mask processing, a technique for performing multiresolution resolution, and the like.
- the multiple resolution described in JP-A-9-44645 is used.
- a method for performing decomposition will be described as an example.
- X-ray image data is decomposed into signals of a plurality of frequency bands, and signals in a desired frequency band are emphasized among the decomposed signals.
- every other pixel is sampled from the X-ray image data, and a pixel with a signal value “0” is interpolated between the sampled pixels. That is, in the sampled image data obtained by sampling, “0” pixels are inserted every other row and every other row of pixels arranged in a matrix.
- the interpolated interpolated image data is subjected to filter processing using a low pass filter to obtain low resolution image data gl.
- the low-resolution image data gl is obtained by extracting a low-frequency band whose spatial frequency is lower than half that of the original X-ray image data. This is because, by sampling, the size of the X-ray image data is reduced to 1/4 and the pixel having the pixel value “0” is interpolated, so that an image in a frequency band whose spatial frequency is higher than half is lost.
- the low resolution image data g is subtracted from the X-ray image data to obtain the high resolution image data.
- Ta j this
- 1 is an image obtained by extracting an image in a high frequency band whose spatial frequency is higher than half, and is an image showing a frequency band from NZ2 to N in the Nyquist frequency N of the original image.
- the low-resolution image data g is filtered by the low-pass filter described above.
- 2 2 2 2 is an image only in the frequency band NZ4 to NZ2 of the Nyquist frequency N of the original image.
- ⁇ is interpolated between pixels to generate inverse transformed image data gg that is four times as large as low-resolution image data g.
- the inverse transformed image data gg is interpolated between pixels to generate inverse transformed image data gg that is four times as large as low-resolution image data g.
- the obtained image data jk is output as frequency-enhanced X-ray image data.
- the spatial frequency F (lpZmm) necessary for visual recognition of an object having a width A (m) or less must be F ⁇ 500ZA.
- the processed X-ray image data obtained as described above is output from the image processing means 12 via the output means 28 and stored in an image DB (not shown).
- the X-ray image data stored in the image DB is output to a display device (not shown) or output to a film output device in response to a request from the input means 27.
- the optical density of the background of the output film is 0.3 to 1.
- the luminance of the background is preferably 10% to 50% of the maximum luminance of the display device, and more preferably 15% to 30%. Noise can be reduced by using the above optical density or luminance as the background.
- FIG. 11 shows a display screen 5 of the display device.
- the incidental information display area 51 displays patient information such as a patient's name and age, and imaging information such as an imaging date and an imaging site.
- the radiogram interpreter designates a suspected onset area in the patient image display area 52 by using an input means such as the pointer 54, it corresponds to the designated area of the patient taken by phase contrast imaging.
- An enlarged positive image of the specimen collected from the location and subjected to gradation processing and inversion processing according to the present embodiment is displayed in the phase contrast image display area 53.
- the gradation characteristic of the display device is optimized for an enlarged positive image displayed in the phase contrast image display area 53.
- An image of the chest front and side of the chest obtained by normal imaging displayed in the patient image display area 52 is captured by phase contrast imaging, and the gradation processing and inversion processing according to the present embodiment is performed. It may be switched to an enlarged page image.
- the interpreter can understand the patient's illness in the lung field using images obtained by normal imaging, and The cause of the disease can be identified in a short time because the enlarged positive image subjected to the gradation processing and inversion processing according to the present embodiment can be identified only when interpretation of the specimen collected from the lung of the patient is required. Highly accurate interpretation 'diagnosis is possible.
- phase contrast imaging was performed under the following experimental conditions, and visual evaluation was performed on the obtained enlarged image.
- the subject was a 5 mm ( ⁇ m) diameter glass wool affixed to a lmm thick acrylic plate and used as a simulated phantom of asbestos in the excised specimen.
- the X-ray absorption rate of the glass wool part of the asbestos simulated phantom when irradiated with 20 keV X-rays was 0.25%.
- the image detector used was a Regius plate RP-5PM and a Regius cassette RC-110M, which are phosphor plates manufactured by the same company.
- Reading of the enlarged image detected by the above image detector is made by Co-Camino Nortej
- the scanning pixel size is 43.
- the tube voltage of the X-ray tube at the time of imaging was 40 (kVp), and the average X-ray energy at that time was 20 keV.
- the tube current was 1 (mA).
- Shooting was performed in the range of 0 ⁇ R2 ⁇ 3.43 so that the magnification ratio M was 1 ⁇ M ⁇ 50.
- Table 2 below shows the shooting conditions at this time and the measurement results of blur B caused by the conditions. A shooting condition number is assigned to identify each shooting condition. Each of these shooting conditions is such that the degree of visibility improvement due to enlargement, the degree of visibility degradation of asbestos edges due to increased blur, and the degree of edge enhancement effect are different!
- the gradation processing, inversion processing, and frequency enhancement processing were performed on the X-ray image data obtained under the conditions 1 to 7 under the conditions shown in Table 3 below. Then, the X-ray image data subjected to image processing was output by the film output device. For image processing, the ⁇ value G is changed for gradation processing, the presence or absence of inversion processing is changed for inversion processing, and the frequency band to be emphasized is changed for frequency enhancement processing.
- the evaluation criteria for the enlarged image output and formed on the film are as follows. [0140] A: Each fiber can be clearly recognized.
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JP2004209152A (ja) * | 2003-01-08 | 2004-07-29 | Konica Minolta Holdings Inc | X線画像撮影装置 |
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JP2004209152A (ja) * | 2003-01-08 | 2004-07-29 | Konica Minolta Holdings Inc | X線画像撮影装置 |
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JP2017189685A (ja) * | 2017-07-28 | 2017-10-19 | コニカミノルタ株式会社 | 画像処理装置、x線撮影システム及び画像処理方法 |
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