Information processing device, radiation imaging system, information processing method and program

Abstract

To provide a radiographic technique capable of improving the inspection efficiency and improving the measurement accuracy while reducing an exposure dose of a subject.SOLUTION: A radiographic apparatus comprises: a generation unit which generates a radiation; an image acquisition unit which acquires image data according to the incident radiation; a first bone density measurement unit which measures the bone density on the basis of the image data acquired by the image acquisition unit in a first radiation field; and a second bone density measurement unit which measures the bone density on the basis of the image data acquired by the image acquisition unit in a second radiation field narrower than the first radiation field.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] Disclosed Technology teeth, Data Processing Device, Radiography systems, information processing The present invention relates to a method and a program, particularly applicable to the measurement of bone density. Data Processing Regarding technology. [Background technology]

[0002] The number of people suffering from osteoporosis is increasing with the aging of the population. As a diagnostic technique for osteoporosis, bone mineral density measurement by dual energy X-ray absorptiometry (DXA), which uses X-rays of two different energies, is known.

[0003] DXA devices generally perform measurements by switching and scanning X-ray fan beams of different energies at high speed. However, in recent years, new technologies have been developed that allow bone density measurement by DXA using cone beam imaging with a flat panel detector (FPD) consisting of two overlapping X-ray detection layers, and that allow bone density measurement by DXA using a single-layer FPD to take two images with X-rays of different energies.

[0004] Patent Document 1 discloses a technique for measuring bone density by using a narrow-area X-ray image to correct scattered rays from a wide-area X-ray image. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-245117 A Summary of the Invention [Problem to be solved by the invention]

[0006] Bone mineral density measurements are often performed on both the lumbar spine, which is prone to changes over time, and the proximal femur, which is prone to serious damage if fractured. Although the lumbar spine and proximal femur can be imaged simultaneously in a short time using a flat panel detector and X-ray cone beam, the measurement accuracy may decrease due to scattered radiation if a wide radiation field is used.

[0007] The technology disclosed in Patent Document 1 requires four images to be taken while changing the irradiation range and the X-ray irradiation conditions, which has the problem of reducing the efficiency of the examination and increasing the radiation dose to the subject.

[0008] Disclosed Technology The present invention has been developed in consideration of the above-mentioned problems, and is capable of improving the efficiency of examinations and the accuracy of measurements while reducing the radiation dose to examinees. Data Processing The purpose is to provide technology. [Means for solving the problem]

[0009] Disclosed Technology According to one aspect of the Data Processing The device has the following configuration: Data Processing The apparatus includes an image acquisition unit that acquires image data corresponding to incident radiation; Based on the image data acquired by the image acquisition unit in the first irradiation field, 1. Bone density measurement Make a decision stomach Based on image data acquired by the image acquisition unit in a second irradiation field narrower than the first irradiation field, Second Perform a bone density test Image Processing The device is equipped with a Effect of the Invention

[0010] Disclosed Technology According to the method, it is possible to improve the efficiency of examinations and the accuracy of measurements while reducing the radiation dose to examinees. Data Processing We can provide technology. [Brief description of the drawings]

[0011] [Figure 1]1 is a diagram showing an example of the arrangement of a radiation imaging system according to a first embodiment. [Diagram 2] FIG. 4 is a diagram for explaining the flow of processing in an image processing unit according to the first embodiment. [Diagram 3] Schematic diagram of high-energy image, low-energy image, and bone image. [Figure 4] FIG. 4 is a diagram for explaining extraction of a bone region. [Diagram 5] FIG. 13 is a diagram for explaining calculation of a baseline region and a calibration curve. [Figure 6] 4A to 4C are diagrams for explaining an example of setting an irradiation field range in the first embodiment. [Figure 7] FIG. 11 is a view for explaining a processing flow in an image processing unit according to the second embodiment. [Figure 8] FIG. 11 is a view for explaining a processing flow in an image processing unit according to a third embodiment. [Figure 9] 13A to 13C are diagrams for explaining an example of setting an irradiation field range in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0013] (First embodiment) 1 is a diagram showing an example of the arrangement of a radiation imaging system 100 according to a first embodiment of the present invention. The radiation imaging system 100 includes a radiation generating device 104, a radiation source 101, a radiation irradiation field aperture 1001, a radiation grid 1002, an FPD 102 (flat panel radiation detector), and an information processing device 120. The arrangement of the radiation imaging system 100 is also simply referred to as a radiation imaging device. The information processing device 120 processes information based on a radiation image obtained by capturing a subject.

[0014] When the exposure switch is pressed, the radiation generator 104 (generation unit) applies a high voltage pulse to the radiation source 101 to generate radiation, and the radiation source 101 irradiates the subject 103 with radiation. At this time, the radiation irradiation field aperture 1001 narrows the radiation irradiation range to prevent radiation from being irradiated outside the region of interest of the subject 103. This reduces unnecessary exposure and can reduce scattered radiation generated by the subject 103. In addition, it is preferable to use a cross grid for the radiation grid 1002. The cross grid is a grid in which slits are formed in a lattice pattern in both the vertical and horizontal directions, and can reduce scattered radiation more effectively and uniformly than a normal grid. This enables cone beam imaging, which eliminates the need for long-term imaging as with fan beams and slit scans. Although the type of radiation is not particularly limited, X-rays are generally used.

[0015] When radiation is irradiated from the radiation source 101 to the subject 103, the FPD 102 functions as an image acquisition unit and acquires image data corresponding to the incident radiation. The FPD 102 accumulates electric charges based on an image signal to acquire a radiographic image. The FPD 102 transfers the radiographic image to the information processing device 120.

[0016] The FPD 102 has a radiation detection unit (not shown) equipped with a pixel array for generating a signal corresponding to radiation. The radiation detection unit detects radiation that has passed through the subject 103, and detects an image signal corresponding to the detected radiation. The radiation detection unit includes, for example, a phosphor (scintillator) that converts incident radiation into light, and a photoelectric conversion element that outputs a signal corresponding to the converted light, which are provided for each pixel arranged in an array (two-dimensional area). The photoelectric conversion element of each pixel converts the radiation, which has been converted into visible light by the phosphor, into an electrical signal, and outputs it as an image signal (radiation image).

[0017] The control unit 105 has an image processing unit 109 that processes radiographic images acquired from the FPD 102, and a storage unit 108 that stores the results of the image processing and various programs. The storage unit 108 can store radiographic images output from the control unit 105, images processed by the image processing unit 109, and calculation results of bone density.

[0018] The image processing unit 109 has, as its functional components, a difference image generating unit 110, a bone region extracting unit 111, a bone density calculating unit 112, a bone density determining unit 113, and an irradiation field setting unit 114. The functions of these functional components are configured, for example, by using one or more CPUs (Central Processing Units) and a program read from the storage unit 108. The components of the image processing unit 109 may be configured with integrated circuits or the like as long as they perform similar functions. The internal components of the information processing device 120 can be configured to include a graphics control unit such as a GPU (Graphics Processing Unit), a communication unit such as a network card, an input / output control unit such as a keyboard, a display, or a touch panel, and the like.

[0019] The monitor 106 displays a radiation image (digital image) acquired by the control unit 105 from the FPD 102 and an image processed by the image processing unit 109. The control unit 105 can control the display of the monitor 106. The operation unit 107 can input instructions to the image processing unit 109 and the FPD 102, and accepts input of instructions to the FPD 102 via a user interface (not shown).

[0020] The control unit 105 obtains an image (bone image) showing the distribution of bones of the subject by processing a plurality of radiation images with different energies of radiation irradiated to the subject by an energy subtraction method. In DXA, at least two radiation images taken with different radiation energies are required to generate one subtraction image. In order to obtain different radiation energies, different voltage pulses are applied to the radiation source 101, and radiation of multiple energies is irradiated from the radiation source 101 to the subject 103.

[0021] Alternatively, a radiation detection section (not shown) may be laminated on the FPD 102. In such a laminated type FPD 102, low-energy radiation is detected by passing through the radiation detection section in the upper layer, radiation passing through the radiation detection section in the upper layer is hardened in quality, and high-energy radiation is detected by the radiation detection section in the lower layer. Therefore, a low-energy radiation image can be obtained by the radiation detection section in the upper layer, and a high-energy radiation image can be obtained by the radiation detection section in the lower layer. Since imaging using the laminated type FPD 102 requires only one radiation irradiation, there is an advantage that there is no influence due to the body movement of the subject 103. Note that even in the case of a single-layer type FPD 102, by performing multiple samplings for one radiation irradiation, the FPD 102 can obtain an image due to low-energy radiation (low-energy radiation image) and an image due to high-energy radiation (high-energy radiation image) with one radiation irradiation. Imaging using the FPD 102 may be still image imaging or video imaging.

[0022] Next, the processing in the image processing unit 109 of the first embodiment will be described in detail with reference to the flowchart shown in FIG. 2. In each step shown in FIG. 2, each processing unit (subtraction image generating unit 110, bone region extracting unit 111, bone density calculating unit 112, and irradiation field setting unit 114) that executes the processing of steps S202 to S205 functions as a first bone density measuring unit that measures bone density based on image data acquired by the FPD 102 (image acquiring unit) in the first irradiation field. Also, each processing unit (control unit 105, subtraction image generating unit 110, bone region extracting unit 111, and bone density calculating unit 112) that executes the processing of steps S208 to S211 functions as a second bone density measuring unit that measures bone density based on image data acquired by the FPD 102 (image acquiring unit) in the second irradiation field narrower than the first irradiation field. The second bone density measuring unit is capable of measuring bone density in the second irradiation field based on the bone density measurement value by the first bone density measuring unit and a predetermined threshold value.

[0023] (S201: Check for follow-up observation) In step S201, the control unit 105 judges whether it is the first measurement or the second or subsequent measurement of the same subject, that is, whether it is follow-up observation or not, using the subject information inputted by the operation unit 107. The control unit 105 may make the judgment in cooperation with the hospital information system HIS or the radiology information system RIS, or may make the judgment using information stored in the memory unit 108.

[0024] When the previous measurement of the same subject has been shifted to bone density measurement by the second bone density measurement unit (S208 to S211), the control unit 105 controls the bone density measurement of the same subject to start from bone density measurement by the second bone density measurement unit. When bone density measurement by the second bone density measurement unit (S208 to S211) has been performed, it is considered that the subject has been judged to be suspected of having osteoporosis. Therefore, the control unit 205 judges that the current examination is for follow-up observation or for evaluating the effectiveness of a drug, and proceeds to step S207 to perform the second bone density measurement. In this case, the control unit 105 controls to start from bone density measurement by the second bone density measurement unit without performing bone density measurement by the first bone density measurement unit (S202 to S205). On the other hand, if this is the first examination, the control unit 205 advances the process to step S202, and performs bone density measurement by the first bone density measurement unit (S202 to S205: first bone density measurement).

[0025] (S202: First shot) In the first imaging in step S202, the irradiation field setting unit 114 sets a first irradiation field capable of imaging a plurality of parts of the subject 103 (for example, L1 to L4 of the lumbar vertebrae and the hip joint 401 at the proximal part of the femur) in the radiation irradiation field aperture 1001. The control unit 105 controls the radiation imaging apparatus to perform imaging in the set first irradiation field. When the exposure switch is pressed, the control unit 105 applies a high voltage pulse (pulse signal) from the radiation generation device 104 to the radiation source 101 to generate radiation. The radiation generation device 104 applies a pulse signal based on a tube voltage to the radiation source 101 to generate a cone beam of radiation. The radiation source 101 irradiates the subject 103 with the cone beam of radiation based on the pulse signal from the radiation generation device 104. The radiation source 101 irradiates the subject 103 with X-rays once at a high voltage V1 (first tube voltage, e.g., 140 kV) and once at a low voltage V2 (second tube voltage, e.g., 80 kV). Note that 140 kV shown as an example of the high voltage V1 and 80 kV shown as an example of the low voltage V2 are merely illustrative values, and the present invention is not limited to these examples, and voltages other than those shown in these examples may also be used. For example, these can be set arbitrarily depending on the part of the subject to be measured, the image the user is about to view, the physique of the subject 103, etc.

[0026] Furthermore, when irradiating X-rays from the radiation source 101, it is desirable to attach an additional filter (not shown) to the radiation exposure field aperture 1001. As the additional filter, for example, a copper plate having a thickness of 0.5 mm can be attached to the radiation exposure field aperture 1001. If low energy components exist in the X-ray spectrum, radiation hardening is likely to occur inside the body of the subject 103, which may be a factor in reducing the accuracy of bone density calculation, but by attaching an additional filter, the low energy side of the X-ray spectrum is cut. This makes it possible to improve the energy separation ability between high-voltage and low-voltage X-rays.

[0027] The FPD 102 generates a high-energy image shown in FIG. 3(a) in high-voltage imaging based on the high voltage V1, and generates a low-energy image shown in FIG. 3(b) in low-voltage imaging based on the low voltage V2.

[0028] In the first measurement, the radiation field aperture 1001 sets the first radiation field with a sufficiently wide radiation field (imaging range) so that both the lumbar vertebrae and the proximal femur can be imaged simultaneously as shown in Figures 3(a) and (b). This allows the bone densities of the clinically important lumbar vertebrae and the proximal femur to be measured simultaneously in one measurement, improving the examination throughput and reducing the burden on the subject 103.

[0029] Furthermore, as described above, if a stack of radiation detection units (not shown) is used inside the FPD 102, a low-energy image as shown in Fig. 3(b) can be obtained from the upper radiation detection unit with one X-ray irradiation, and a high-energy image as shown in Fig. 3(a) can be obtained from the lower radiation detection unit. When X-rays are irradiated from the radiation source 101 at a high voltage V1 (e.g., 140 kV), the margin for radiation quality hardening by the upper radiation detection unit is small and the energy separation ability is reduced, so that the additional filter described above does not need to be attached. An image captured by X-ray irradiation based on the high voltage V1 is called a high-energy image, and an image captured by X-ray irradiation based on the low voltage V2 is called a low-energy image.

[0030] (S203: Bone image generation) In step S203, the difference image generating unit 110 calculates the logarithmic difference between the high-energy image shown in Fig. 3(a) and the low-energy image shown in Fig. 3(b), both captured in S202, to generate a bone image 303 shown in Fig. 3(c). The process of the difference image generating unit 110 will be specifically described below. First, the high-energy image and the low-energy image can be expressed by the following [Equation 1] and [Equation 2].

[0031]

number

[0032]

number

[0033] Here I H is the high-energy image shown in Fig. 3(a), and I L is the low-energy image shown in Fig. 3(b). The captured high-energy and low-energy images show two-dimensional distributions of pixel values.

[0034] Also, I H0 and I L0 are respectively a high energy image and a low energy image when the subject 103 is not present. Here, the subscript H indicates high energy, and the subscript L indicates low energy. Also, the subscript A indicates soft tissue, and the subscript B indicates bone (bone region). μ HA and μ LA are the mass attenuation coefficients of soft tissue at high and low energies, respectively, and μ HB and μ LB are the mass attenuation coefficients of bone at high and low energies, respectively. σ A is the area density of the soft tissue, σ B is the bone area density. The unit of mass attenuation coefficient is cm 2 / g, and the unit of area density is g / cm 2 It is.

[0035] Here, the difference image generating unit 110 adds μ LA / μ HA By multiplying the result by 1 and performing subtraction using the formula (2), a bone image (FIG. 3(c)) is generated as shown in the following formula (3).

[0036]

number

[0037] (S204: Bone region extraction) In step S204, the bone region extraction unit 111 extracts a bone region (ROI) for calculating bone density from a bone image showing the distribution of bones in the subject 103. The simplest method for extracting a bone region is, for example, to have a user select a bone region from a user interface. However, it is troublesome and time-consuming for a user to extract a bone region using a mouse or the like. Furthermore, even for the same subject, different users may extract different bone regions, and even for the same user, if the bone region changes each time, the reproducibility of the calculation accuracy of bone density may decrease.

[0038] Therefore, it is desirable to automatically extract the bone region using segmentation by image processing. The bone region extraction unit 111 can extract the bone region for calculating the bone density from the bone image showing the distribution of bones in the subject 103 using known segmentation techniques such as the Watershed method, graph cut, and graph cut. In addition to the above-mentioned segmentation techniques, the bone region extraction unit 111 can also extract the bone region from the bone image using machine learning techniques such as Unet and PSPnet.

[0039] The bone region extraction unit 111 sets (extracts) a bone region (analysis region) for calculating bone density from a bone image. Fig. 4 is a diagram showing an example of bone region extraction, in which L1 to L4 are extracted as the analysis region of the lumbar vertebrae, and a hip joint 401 is extracted as the analysis region of the proximal femur.

[0040] (S205: Bone density calculation) In step S205, the bone density calculation unit 112 calculates the bone density of the bone region (ROI: FIG. 4) extracted by the bone region extraction unit 111 in step S204. The bone density calculation unit 112 sets a soft tissue region near the bone region, and corrects the pixel values ​​of the bone region based on the pixel values ​​of the soft tissue region. Then, the bone density calculation unit 112 calculates the bone density of the bone region based on the pixel values ​​of the corrected bone region.

[0041] In calculating bone density, the bone density calculation unit 112 sets a soft tissue region near the bone region for which bone density is to be calculated (for example, in the case of the lumbar vertebrae, the region corresponding to L1 to L4 in FIG. 4). Hereinafter, this soft tissue region is also referred to as a baseline region. As shown in FIG. 5(a), the bone density calculation unit 112 sets a baseline region 501 and a baseline region 502 to be only soft tissue so as not to include a bone region and to be located near the bone region for which bone density is to be calculated. The pixel values ​​of the high-energy image (FIG. 3(a)) and the pixel values ​​of the low-energy image (FIG. 3(b)) in the baseline regions 501 and 502 can be expressed by the following formulas [Equation 4] and [Equation 5], respectively. Since the baseline regions 501 and 502 are set so as not to include a bone region, formulas [Equation 4] and [Equation 5] are set so as not to include a bone region, and therefore formulas [Equation 4] and [Equation 5] are set so as not to include a high-energy image (I HA , I HO ), low energy image (I LA , I LO ), mass attenuation coefficient (μ HA , μ LA ), and areal density (σ A )

[0042]

number

[0043]

number

[0044] Here, the bone density calculation unit 112 calculates μ LA / μ HA By multiplying by and performing subtraction from equation (5), we obtain the following equation (6) for the difference between the high-energy image and the low-energy image in the baseline regions 501, 502 (soft tissue).

[0045]

number

[0046] Furthermore, the bone mineral density calculation section 112 calculates the difference between the formula [6] and the formula [3] to obtain the following formula [7].

[0047]

number

[0048] When the unknown subject 103 does not exist in the formula [7], the high energy image I H0 and low energy image I L0 is removed. Also, the left side of the formula [7] is determined by the right side, so that the bone density σ B Hereinafter, the equation (7) is called the bone image after baseline correction.

[0049] Furthermore, the bone density calculation unit 112 calculates the calibration curve 507 in FIG. 5(c) from the calibration phantom 503 in FIG. 5(b), and calculates the pixel values ​​in the bone image after baseline correction using the calibration curve 507 in terms of bone density (g / cm 2 Specifically, convert it as follows:

[0050] The calibration phantom 503 has a first calibration portion 504, a second calibration portion 505, and a third calibration portion 506. The first calibration portion 504, the second calibration portion 505, and the third calibration portion 506 of the calibration phantom 503 each have a bone density of 0.5 g / cm 2 , 1.0g / cm 2 , 1.5g / cm 2 The calibration phantom 503 shown in FIG. 5(b) is photographed under the same conditions as the subject 103, and a bone image after baseline correction according to the formula [7] is generated. This makes it possible to obtain a calibration curve 507 as shown in FIG. 5(c). Here, the calibration curve 507 in FIG. 5(c) shows the relationship between the bone density (vertical axis) and the pixel value (horizontal axis) of the bone image after baseline correction.

[0051] Finally, the bone density calculation unit 112 calculates the pixel values ​​in the baseline-corrected bone image generated based on the imaging of the subject 103 using the calibration curve 507 as bone density (g / cm 2It is preferable to capture the calibration phantom 503 and obtain the calibration curve 507 shown in Fig. 5(b) before the start of an examination for the day, for example.

[0052] (S206: Judgment of suspected osteoporosis) In step S206, the bone density determining unit 113 performs osteoporosis determination of the average bone density of the lumbar vertebrae L1 to L4 in FIG. 4 and the bone density of the hip joint 401 of the proximal femur, which are calculated in S205. For example, in the primary osteoporosis diagnostic criteria, osteoporosis is diagnosed by comparison with the YAM value. Here, the YAM value is the average value of bone density of young adults (20 to 44 years old). In the primary osteoporosis diagnostic criteria, when the bone density of the subject is 70 to 80% of the YAM value, the subject is diagnosed as having a decreased bone mass, and when the bone density is 70% or less of the YAM value, the subject is diagnosed as having primary osteoporosis. Based on the primary osteoporosis diagnostic criteria, the bone density determining unit 113 performs osteoporosis determination by comparison of the average bone density of the lumbar vertebrae L1 to L4 and the bone density of the hip joint 401 of the proximal femur with the YAM value.

[0053] In the judgment of S206, when the bone density judgment unit 113 judges (discriminates) that the bone density of each part of the subject 103 is less than 80% of the YAM value (S206-YES), the control unit 105 advances the process to S207 (change of irradiation field) and moves to preparation for the second imaging in S208. The control unit 105 controls the measurement of bone density by the first bone density measurement unit (S202 to S205) and the measurement of bone density by the second bone density measurement unit (S208 to S210). When the measurement value of bone density by the first bone density measurement unit is lower than a predetermined value, the control unit 105 shifts the process to measure bone density by the second bone density measurement unit. Note that when the measurement value of bone density by the first bone density measurement unit is lower than a predetermined value for a plurality of parts, the bone density is measured by the second bone density measurement unit for each part.

[0054] On the other hand, if the bone density determination unit 113 determines in S206 that the bone density of each part of the subject 103 is equal to or greater than the YAM value (S206-NO), the test is terminated as the possibility of osteoporosis is low based on the determination result (discrimination result).

[0055] (S207: Change of irradiation field) In step S206 described above, the irradiation field setting unit 114 sets a second irradiation field for measurement by the second bone density measuring unit based on the measurement result of the bone density by the first bone density measuring unit (S206-YES). That is, when the bone density determining unit 113 determines that there is a suspicion of osteoporosis, the irradiation field setting unit 114 narrows the radiation irradiation field aperture 1001 to change the irradiation field. The irradiation field setting unit 114 sets a first irradiation field capable of imaging multiple parts of the subject in the measurement by the first bone density measuring unit (S202 to S205), and sets a second irradiation field narrower than the first irradiation field and capable of imaging at least some parts of the multiple parts in the measurement by the second bone density measuring unit (S208 to S210). Here, the first irradiation field includes the lumbar spine and the proximal femur as a plurality of parts of the subject 103, and the second irradiation field includes either the lumbar spine or the proximal femur as a portion of the plurality of parts. Since radiation is not irradiated to areas other than the second irradiation field, an increase in the radiation dose of the subject 103 can be suppressed.

[0056] In the first imaging in step S202, the irradiation field setting unit 114 set the first irradiation field in the radiation irradiation field aperture 1001, which is capable of imaging multiple parts of the subject 103 (e.g., L1 to L4 of the lumbar vertebrae and the hip joint 401 proximal to the femur). In this step, the irradiation field setting unit 114 sets the second irradiation field in the radiation irradiation field aperture 1001, which is a narrower irradiation field than the first irradiation field and is capable of imaging at least some of the multiple parts.

[0057] The irradiation field setting unit 114 is capable of setting the second irradiation field by using a trained model regarding the setting of the irradiation field corresponding to the site where the measurement is to be performed by the second bone density measurement unit.

[0058] In step S206 described above, if the bone density determination unit 113 determines that the average value of bone density in the lumbar vertebrae L1 to L4 is a decrease in bone density, in this step, the irradiation field setting unit 114 narrows the irradiation field to include the lumbar vertebrae L1 to L4, which are at least a part of the multiple parts (lumbar vertebrae L1 to L4, and the hip joint 401 at the proximal part of the femur), as shown in Fig. 6(a). That is, the irradiation field setting unit 114 changes the setting of the radiation irradiation field narrower 1001 to narrow the irradiation field to a second irradiation field narrower than the first irradiation field.

[0059] Also, in step S206, if the hip joint 401 in the proximal part of the femur is determined to have a decreased bone density, the irradiation field is narrowed to include only the hip joint 401 as shown in Fig. 6(b). In this step, the irradiation field setting unit 114 narrows the irradiation field to include the hip joint 401, which is at least a part of the multiple parts (lumbar vertebrae L1 to L4, and the hip joint 401 in the proximal part of the femur), as shown in Fig. 6(b). That is, similar to the case of the lumbar vertebrae, the irradiation field setting unit 114 changes the setting of the radiation irradiation field aperture 1001 to narrow the irradiation field to a second irradiation field narrower than the first irradiation field.

[0060] Here, if the radiation irradiation field aperture 1001 can be electrically controlled in conjunction with the radiation imaging system 100, it is possible to automatically narrow the irradiation field by utilizing the result of the bone region extraction in step S204. In addition, when the setting of the irradiation field is changed manually, the control unit 105 can also perform display control so as to display on the monitor 106 an instruction for the user to narrow the irradiation field to a relevant part.

[0061] (S208: Second Shooting) In step S208, the control unit 105 controls the radiation imaging apparatus, and when the exposure switch is pressed, a pulse signal is sent from the radiation generating device 104 to the radiation source 101 to generate radiation. In the second imaging in step S208, imaging is performed in the second irradiation field changed in step S207. The second irradiation field is narrower than the first irradiation field used in the first imaging (S202), and the irradiation field is narrowed so as to image at least some of the multiple parts. The processing of the second imaging is similar to the first imaging in S202, except that the irradiation field is narrowed and the imaging target part is one, as shown in Figs. 6(a) and (b), for example, and the details of the imaging are omitted.

[0062] (S209: Bone image generation) In step S209, the difference image generating unit 110 generates a bone image by calculating the logarithmic difference between the high-energy image and the low-energy image captured in S208. The image difference in step S209 is the same as the image difference in S203 except that the irradiation field is narrowed down as shown in Figures 6(a) and 6(b) and the part of the subject to be imaged is one, and the details of the difference process are omitted.

[0063] (S210: Bone region extraction) In step S210, the bone region extraction unit 111 extracts a bone region (ROI) for calculating bone density from the bone image. The bone region extraction process in this step is the same as the bone region extraction process in step S204. Therefore, the bone region extraction unit 111 can directly apply the result of step S204 without extracting a bone region again. That is, the bone region extraction unit 111 can apply the extraction result of the bone region extracted in the measurement of the first bone density measurement unit to the extraction of the bone region in the measurement of the second bone density measurement unit. By using the same bone region as the bone region extracted in step S204, it becomes possible to more accurately grasp the difference (change) between the first bone density measurement in the first shooting and the second bone density measurement in the second shooting.

[0064] On the other hand, there may be cases where the subject 103 moves between the first and second bone density measurements, in which case the bone region may be extracted again.

[0065] According to this embodiment, in a screening test such as an initial consultation or health checkup, first, a first bone density measurement based on a first photograph is performed to simultaneously measure bone density at multiple sites of the subject (e.g., the lumbar spine and proximal femur). If the first bone density measurement determines that osteoporosis is suspected, a second bone density measurement based on a second photograph is performed by narrowing the irradiation field to a specific site, and performing a precise bone density measurement with reduced scattered radiation. This reduces the examination time when measuring the bone density of a large number of subjects such as in a screening test, and improves throughput, thereby reducing the burden on subjects and users.

[0066] Second embodiment In the first embodiment, a case where imaging is performed using two tube voltages (V1, V2) in the first bone density measurement unit and the second bone density measurement unit is described, but in the second embodiment, a configuration is described in which the first bone density measurement unit measures bone density based on image data acquired by the FPD 102 (image acquisition unit) in response to radiation generated at a single tube voltage. The configuration of the radiation imaging system 100 (FIG. 1) is the same as in the first embodiment.

[0067] The processing in the image processing unit 109 of the second embodiment will be described with reference to the flowchart shown in Fig. 7. The processing differs from the processing in the image processing unit 109 of the first embodiment (Fig. 2) in steps S702 and S705, and therefore only the different parts of the processing will be described.

[0068] (S702: First measurement) In the first imaging in step S702, the control unit 105 controls the radiation imaging apparatus to perform imaging in the set first irradiation field. When the exposure switch is pressed, the control unit 105 applies a high voltage pulse (pulse signal) from the radiation generation apparatus 104 to the radiation source 101 to generate radiation. The radiation source 101 irradiates the subject 103 with X-rays based on the pulse signal from the radiation generation apparatus 104. The radiation source 101 irradiates the subject 103 with X-rays based on a single tube voltage (e.g., 140 kV). The tube voltage (e.g., 140 kV) corresponds to the high voltage V1 described in the first embodiment, and the FPD 102 acquires a high energy image based on the tube voltage (high voltage V1). In addition, the bone density is approximately measured by using a method described below in S705.

[0069] As a result, in the first bone density measurement based on the first imaging, imaging is performed with a single tube voltage (high voltage V1), which facilitates control of the radiation generator 104. This makes it possible to measure bone density while performing fluoroscopic imaging for positioning, for example.

[0070] (S705: Bone density calculation) In the first measurement (S702) of the second embodiment, imaging is performed using a single tube voltage, so the bone density calculation unit 112 calculates the bone density of the bone region (ROI: FIG. 4) extracted by the bone region extraction unit 111 in S204 using the following approximate method.

[0071] As described in the first embodiment, the pixel values ​​of the bone region of the high-energy image (FIG. 4) can be expressed by the following formula [8].

[0072]

number

[0073] Moreover, the pixel values ​​of baseline regions 501 and 502 (FIG. 5) made of soft tissue can be expressed by the following formula [9].

[0074]

number

[0075] Here, the area density σ is the volume density ρ multiplied by the tissue thickness d. Therefore, if the thickness of the baseline region and the bone region can be considered to be approximately the same, the approximation of the following formula

[10] holds true.

[0076]

number

[0077] Here, the superscript b represents the baseline region, the subscript A represents soft tissue, and the subscript B represents bone. The approximation of Equation 10 holds when the baseline region and the bone region are close to each other in the human body.

[0078] Therefore, the bone mineral density calculation section 112 substitutes the formula

[10] into the formula [9], performs subtraction from the formula [8], and rearranges it to obtain the following formula

[11] .

[0079]

number

[0080] When the subject 103, which is an unknown in the formula [8], does not exist, the high-energy image I H0 is removed, and an approximate baseline-corrected bone image can be obtained. Actual bone density (g / cm 2 The conversion is the same as in the first embodiment, and the bone mineral density calculation unit 112 converts pixel values ​​in the bone image after baseline correction into bone mineral density g / cm using the calibration phantom 503 in FIG. 5(b) and the calibration curve 507 in FIG. 5(c). 2 Convert to.

[0081] According to this embodiment, an approximate bone density measurement can be performed by performing a first bone density measurement using a single tube voltage. Then, for a site determined to be suspected of osteoporosis in the first bone density measurement, a precise bone density measurement using two or more tube voltages is performed in the second bone density measurement by the processing of steps S207 to S211. This allows, for example, positioning to be performed while observing bone density in a moving image in a diagnostic device capable of capturing moving images such as an X-ray TV, and a seamless transition to a precise second bone density measurement can be made.

[0082] When the second bone density measurement unit measures bone density (S207 to S211), the second bone density measurement unit measures bone density based on image data acquired by FPD 102 (image acquisition unit) according to radiation generated by multiple tube voltages including a single tube voltage. That is, the second bone density measurement unit measures bone density using image data acquired by the bone density measurement by the first bone density measurement unit and image data acquired by FPD 102 (image acquisition unit) at a tube voltage different from the single tube voltage. By using the image data acquired by the bone density measurement by the first bone density measurement unit in the bone density measurement by the second bone density measurement unit, an increase in radiation exposure dose in the subject 103 can be suppressed, and by performing measurement using image data of multiple tube voltages, it is possible to perform bone density measurement with high accuracy.

[0083] Third embodiment In the first embodiment, a configuration has been described in which a first bone density measurement based on a first imaging is performed to simultaneously perform bone density measurements of multiple sites of the subject 103, and if the first bone density measurement determines that osteoporosis is suspected, a second bone density measurement based on a second imaging narrows the irradiation field to a specific site to perform a precise bone density measurement with reduced scattered radiation. In the third embodiment, a configuration will be described in which the irradiation field setting unit 114 sets multiple irradiation fields when the second bone density measurement unit performs the second bone density measurement based on the second imaging. The configuration of the radiation imaging system 100 (FIG. 1) is the same as that of the first embodiment.

[0084] The processing in the image processing unit 109 of the third embodiment will be described with reference to the flowchart shown in Fig. 8. The processing different from the processing in the image processing unit 109 of the first embodiment (Fig. 2) is step S807, so only the different part of the processing will be described.

[0085] In step S206 of the first bone density measurement, if the bone density determining unit 113 determines that osteoporosis is suspected (S206-YES), the irradiation field setting unit 114 narrows the radiation irradiation field aperture 1001 to change the irradiation field (S207). The irradiation field setting unit 114 sets a plurality of irradiation fields. The bone density measurement unit of this embodiment measures bone density in the plurality of irradiation fields set by the irradiation field setting unit 114 based on image data acquired by the FPD 102 (image acquisition unit).

[0086] The multiple radiation fields include each part of the subject where bone density is to be measured, and radiation is not irradiated to areas other than the multiple radiation fields.

[0087] Here, the first irradiation field set in the first imaging (S202) is a single irradiation field with an imaging range secured so that multiple parts can be imaged simultaneously. In this step, the irradiation field setting unit 114 changes the setting of the radiation irradiation field aperture 1001 so as to separate the single first irradiation field into multiple irradiation fields corresponding to the positions of multiple parts of the subject 103 (for example, L1 to L4 of the lumbar vertebrae, and the hip joint 401 at the proximal part of the femur). FIG. 9 is a diagram for explaining an example of setting the irradiation field range in the third embodiment. As shown in FIG. 9, the irradiation field setting unit 114 changes the setting of the radiation irradiation field aperture 1001 to separate the first irradiation field (single irradiation field) into an irradiation field 901 corresponding to the lumbar vertebrae (L1 to L4) and an irradiation field 902 corresponding to the hip joint 401 at the proximal part of the femur.

[0088] In step S208, imaging is performed in the second irradiation field changed in step S207. The control unit 105 controls the radiation imaging apparatus, and when the exposure switch is pressed, a pulse signal is sent from the radiation generation device 104 to the radiation source 101 to generate radiation, and both the lumbar vertebrae (L1 to L4) and the hip joint 401 in the proximal part of the femur are imaged simultaneously.

[0089] Then, in S211, the bone density calculation section 112 simultaneously calculates the bone density of the multiple bone regions (ROI: FIG. 4) extracted by the bone region extraction section 111 in step S210.

[0090] According to this embodiment, by setting multiple irradiation fields in the second bone density measurement based on the second imaging, it is possible to simultaneously measure the bone density of multiple sites and perform highly accurate bone density measurement with reduced scattered radiation. For example, the lumbar spine is a site where the efficacy of a drug is easily determined, and the proximal femur is a site where a fracture is likely to lead to bedriddenness, and is of high clinical importance, so this embodiment is effective when measuring both sites at the same time and performing highly accurate bone density measurement with reduced scattered radiation.

[0091] <Other embodiments> The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0092] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0093] 10: Radiography system (radiography device), 101: Radiation source, 102: FPD (flat panel radiation detector), 104: radiation generator, 105: control unit, 106: monitor (display device), 108: storage unit, 110: difference image generating unit, 111: bone region extracting unit, 112: bone density calculating unit, 113: bone density determining unit, 114: irradiation field setting unit, 116: display control unit, 120: Information processing device

Claims

1. an image acquisition unit that acquires image data according to the incident radiation; an image processing unit that performs a first bone density measurement based on image data acquired by the image acquisition unit in a first irradiation field, and performs a second bone density measurement based on image data acquired by the image acquisition unit in a second irradiation field narrower than the first irradiation field; An information processing device comprising:

2. Further comprising an irradiation field setting unit for setting an irradiation field of the radiation, The irradiation field setting unit is In the first bone density measurement, the first radiation field capable of imaging a plurality of parts of the subject is set; The information processing device according to claim 1 , wherein the second bone density measurement sets a second radiation field that is narrower than the first radiation field and capable of imaging at least a portion of the multiple regions.

3. The information processing device according to claim 2 , wherein the first irradiation field includes the lumbar vertebrae and the proximal femur as the plurality of regions, and the second irradiation field includes either the lumbar vertebrae or the proximal femur as the portion of the region.

4. The information processing apparatus according to claim 2 , wherein the irradiation field setting unit sets the second irradiation field using a trained model regarding setting of an irradiation field corresponding to a site where the second bone density measurement is performed.

5. The information processing apparatus according to claim 2 , wherein the irradiation field setting unit sets the second irradiation field based on a result of the first bone density measurement.

6. The information processing apparatus according to claim 2 , wherein the radiation is not irradiated onto an area other than the second radiation field.

7. The information processing apparatus according to claim 2 , further comprising a control unit that controls the image processing unit so as to execute the first bone density measurement and the second bone density measurement.

8. The information processing apparatus according to claim 7 , wherein the control unit, when a value measured by the first bone density measurement is lower than a predetermined value, shifts processing to perform the second bone density measurement.

9. The information processing apparatus according to claim 1 , wherein the image processing unit performs the second bone density measurement using the second radiation field based on a result of the first bone density measurement.

10. The information processing apparatus according to claim 1 , wherein the image processing unit performs the second bone density measurement using the second radiation field based on a measurement value from the first bone density measurement and a predetermined threshold value.

11. The information processing apparatus according to claim 8 , wherein the image processing unit determines whether or not to omit the first bone density measurement using the first radiation field, and performs the second bone density measurement using the second radiation field depending on a result of the determination.

12. The image processing unit includes: a generating unit that generates a bone image showing a distribution of bones by a difference between image data corresponding to the radiation of the first tube voltage and image data corresponding to the radiation of the second tube voltage; an extraction unit that extracts a bone region in the bone image for which bone density is to be calculated; a calculation unit for calculating a bone density of the bone region, The calculation unit sets a soft tissue region in the vicinity of the bone region, correcting pixel values ​​of the bone region based on pixel values ​​of the soft tissue region; The information processing apparatus according to claim 11 , wherein a bone density of the bone region is calculated based on the corrected pixel values ​​of the bone region.

13. The information processing device according to claim 12 , wherein the extraction unit applies an extraction result of the bone region extracted in the first bone density measurement to extraction of the bone region in the second bone density measurement.

14. In the first bone density measurement, the first bone density measurement is performed based on image data acquired by the image acquisition unit in response to radiation generated at a single tube voltage, 12. The information processing device according to claim 2, wherein the second bone density measurement is performed based on image data acquired by the image acquisition unit in response to radiation generated by a plurality of tube voltages including the single tube voltage.

15. An information processing device as described in claim 12, wherein the second bone density measurement is performed using the image data acquired in the first bone density measurement and image data acquired by the image acquisition unit at a tube voltage different from a single tube voltage.

16. An information processing device comprising: an image processing unit that performs a first bone density measurement based on a first radiation image corresponding to a first radiation field, and performs a second bone density measurement based on a second radiation image corresponding to a second radiation field narrower than the first radiation field.

17. A radiation detection device for detecting radiation; An information processing device according to claim 1 , which processes image data acquired from the radiation detection device; A radiation imaging system comprising:

18. Further comprising a generating unit that generates the radiation, 18. The radiography system according to claim 17, wherein the generating unit generates a cone beam of radiation by applying a pulse signal based on a tube voltage to a radiation source.

19. Further comprising a generating unit that generates the radiation, The radiation imaging system according to claim 17 , wherein the generation unit generates the radiation based on a first tube voltage and the radiation based on a second tube voltage lower than the first tube voltage.

20. An information processing method of an information processing device having an image acquisition unit that acquires image data corresponding to incident radiation, a first step of performing a first bone density measurement based on image data acquired by the image acquisition unit in a first irradiation field; a second step of performing a second bone density measurement based on image data acquired by the image acquisition unit in a second irradiation field narrower than the first irradiation field; An information processing method for performing the above.

21. An information processing method for performing a first bone density measurement based on a first radiation image corresponding to a first radiation field, and performing a second bone density measurement based on a second radiation image corresponding to a second radiation field narrower than the first radiation field.

22. A program for causing a computer to function as each unit of the information processing device according to any one of claims 1 to 16.

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