Medical image processing apparatus and medical image processing method

Abstract

The present invention provides a medical image processing apparatus and a medical image processing method capable of making the tip of a medical device clear in a tomosynthesis image of a subject into which the medical device is inserted. A medical image processing apparatus that processes a tomosynthesis image generated from a plurality of projection images obtained by photographing a subject at an angle range of less than 180 degrees, characterized by comprising: a storage unit that pre-stores blur data for each coordinate of a photographing space; and a correction unit that corrects the tomosynthesis image using the blur data.

Description

Technical Field

[0001] The present invention relates to a medical image processing apparatus and a medical image processing method for processing medical images obtained by an X-ray tomosynthesis apparatus, and is related to a technique for clarifying the tip of a medical device inserted into a subject. Background Art

[0002] An X-ray tomosynthesis apparatus is an apparatus that generates a tomosynthesis image, which is a tomographic image in a plane parallel to a table, using a plurality of projection images taken from a plurality of directions of a subject. In addition, a three-dimensional image generated from a plurality of tomosynthesis images is used to confirm the three-dimensional configuration of a medical device such as a guide sheath inserted into a subject. On the other hand, an X-ray tomosynthesis apparatus that takes a plurality of projection images has a higher exposure dose than an X-ray fluoroscopic imaging apparatus, and it is desired to suppress the exposure dose.

[0003] In Patent Document 1, the following technique is disclosed: In order to suppress the exposure dose in tomosynthesis imaging, the sizes and positions of a plurality of imaging objects are determined, an angular range in which each imaging object can be separated is calculated, and projection images are obtained within that angular range.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent No. 6502188

[0007] However, in Patent Document 1, insufficient consideration is given to clarifying the tip of a medical device such as a catheter or an endoscope inserted into a subject. In an X-ray tomosynthesis apparatus, the angular range for taking projection images is less than 180 degrees and is limited, so distortion occurs in the generated tomosynthesis image, blurring the tip of the medical device. When the distortion in the tomosynthesis image is large, the three-dimensional configuration of the tip of the medical device cannot be confirmed, which poses an obstacle to treatment and the like. Summary of the Invention

[0008] Therefore, an object of the present invention is to provide a medical image processing apparatus and a medical image processing method that can clarify the tip of a medical device in a tomosynthesis image of a subject into which a medical device is inserted.

[0009] To achieve the above object, the present invention is a medical image processing apparatus that processes a tomosynthesis image generated using a plurality of projection images taken within an angular range less than 180 degrees, and is characterized by including: a storage unit that pre-stores blur data for each coordinate in the imaging space; and a correction unit that corrects the tomosynthesis image using the blur data.

[0010] In addition, the present invention is a medical image processing method for processing a tomosynthesis image generated from a plurality of projection images captured within an angular range less than 180 degrees, characterized by comprising: a reading step of reading blur data for each coordinate of the imaging space; and a correction step of correcting the tomosynthesis image using the blur data.

[0011] Advantages of the Invention

[0012] According to the present invention, there can be provided a medical image processing apparatus and a medical image processing method capable of clarifying the tip of a medical device in a tomosynthesis image of a subject into which the medical device is inserted. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is an overall structural diagram of a medical image processing apparatus.

[0014] Figure 2 is an overall structural diagram of an X-ray tomosynthesis apparatus as an example of a medical image capturing apparatus.

[0015] Figure 3 is a diagram showing an example of the processing flow of Example 1.

[0016] Figure 4 is a diagram showing an example of a table recording blur data for each coordinate of the imaging space.

[0017] Figure 5 is a diagram showing an example of the processing flow of Example 2.

[0018] Figure 6 is a diagram showing an example of a table recording adjustment coefficients for each type of medical device.

[0019] Figure 7 is a diagram showing an example of the display window of Example 2.

[0020] Figure 8 is a diagram showing an example of the relationship between the adjustment coefficient and the contrast.

[0021] Figure 9 is a diagram showing an example of the processing flow of Example 3.

[0022] Figure 10 is a diagram showing an example of the operation window of Example 3.

[0023] Description of Reference Numerals

[0024] 1: Medical image processing device, 2: Arithmetic unit, 3: Memory, 4: Storage device, 5: Network adapter, 6: System bus, 7: Display device, 8: Input device, 10: Medical image capturing device, 11: Medical image database, 200: X-ray tomosynthesis device, 201: X-ray source, 202: X-ray detector, 203: Object to be detected, 204: Bed, 205: Operation console, 701: Medical device area, 702: Arrow, 1001: Temporal resolution adjustment unit Detailed implementation mode

[0025] Hereinafter, embodiments of the medical image processing device and the medical image processing method according to the present invention will be described with reference to the drawings. In addition, in the following description and drawings, structural elements having the same functional structure are given the same reference numerals and redundant descriptions are omitted.

[0026]

Embodiment 1

[0027] Figure 1 FIG. shows the hardware structure of the medical image processing device 1. The medical image processing device 1 is configured by connecting an arithmetic unit 2, a memory 3, a storage device 4, and a network adapter 5 to a system bus 6 so as to be able to transmit and receive signals. In addition, the medical image processing device 1 is connected to a medical image capturing device 10 and a medical image database 11 via a network 9 so as to be able to transmit and receive signals. Further, a display device 7 and an input device 8 are connected to the medical image processing device 1. Here, the phrase "so as to be able to transmit and receive signals" means a state in which signals can be transmitted and received to and from each other or from one party to the other party electrically or optically, whether wired or wireless.

[0028] The arithmetic unit 2 is a device that controls the operation of each structural element. Specifically, it is a CPU (Central Processing Unit), an MPU (Micro Processor Unit), etc. The arithmetic unit 2 loads the programs stored in the storage device 4 and the data required for program execution into the memory 3 and executes them, thereby performing various image processing operations on medical images. The memory 3 is a device that stores the programs executed by the arithmetic unit 2 and the intermediate results of arithmetic processing. The storage device 4 is a device that stores the programs executed by the arithmetic unit 2 and the data required for program execution. Specifically, it is an HDD (Hard Disk Drive), an SSD (Solid State Drive), etc. The network adapter 5 is used to connect the medical image processing device 1 to a network 9 such as a LAN, a telephone line, or the Internet. Various data processed by the arithmetic unit 2 can be transmitted and received to and from the outside of the medical image processing device 1 via a network 9 such as a LAN (Local Area Network).

[0029] The display device 7 is a device that displays the processing results of the medical image processing device 1, etc., specifically, a liquid crystal display or the like. The input device 8 is an operating device for the operator to give operation instructions to the medical image processing device 1, specifically, a keyboard, a mouse, a touch panel, etc. The mouse may also be other indicating devices such as a touchpad or a trackball.

[0030] The medical image capturing device 10 is, for example, an X-ray tomosynthesis device that captures a subject from multiple directions to obtain multiple projection images and generates a tomographic image from the multiple projection images, as will be described later. The medical image database 11 is a database system that stores projection images, tomographic images, corrected images obtained by performing image processing on the tomographic images, etc., obtained by the medical image capturing device 10. Figure 2 The medical image database 11 is a database system that stores projection images, tomographic images, corrected images obtained by performing image processing on the tomographic images, etc., obtained by the medical image capturing device 10.

[0031] As will be described later. Figure 2 The overall structure of the X-ray tomosynthesis device 200, which is an example of the medical image capturing device 10, will be described. In addition, in Figure 2 the direction perpendicular to the paper surface is set as the X-axis, the longitudinal direction is set as the Y-axis, and the lateral direction is set as the Z-axis. The X-ray tomosynthesis device 200 includes an X-ray source 201, an X-ray detector 202, a table 204, and an operation console 205.

[0032] The X-ray source 201 is a device that irradiates the subject 203 placed on the table 204 with X-rays. When a high voltage corresponding to the imaging conditions set by the operation console 205 is applied to the X-ray source 201, the subject 203 is irradiated with X-rays.

[0033] The X-ray detector 202 is a device that measures the spatial distribution of the transmitted X-rays by detecting the X-rays transmitted through the subject 203. The X-ray detector 202 is disposed opposite to the X-ray source 201, and a large number of detection elements are two-dimensionally arranged in the ZX plane. A two-dimensional projection image is generated based on the signals measured by the X-ray detector 202.

[0034] In order to capture the subject 203 from multiple directions to obtain multiple projection images, at least one of the X-ray source 201 and the X-ray detector 202 is moved in the Z-axis direction. The obtained multiple projection images are used in the generation of a tomosynthesis image that is a tomographic image in the ZX plane parallel to the table 204.

[0035] The operation console 205 is a device that performs setting of imaging conditions, generation, and display of a tomosynthesis image, and is composed of a so-called computer. In Figure 2 the tomosynthesis image of the chest of the subject 203 is displayed on the operation console 205 illustrated. The operation console 205 may be Figure 1 the medical image processing device 1 illustrated.

[0036] In the X-ray tomosynthesis apparatus 200, since the angular range for capturing projection images is limited to less than 180 degrees, for example, 20 degrees to 40 degrees, distortion occurs in the generated tomosynthesis image, blurring the front ends of medical devices such as catheters and endoscopes inserted into the subject 203. When the distortion in the tomosynthesis image is large, the three-dimensional configuration of the front end of the medical device cannot be confirmed, which poses an obstacle to treatment and the like. Therefore, in the first embodiment, a process for clarifying the tomosynthesis image is executed.

[0037] Use Figure 3 An example of the process executed in the first embodiment will be described step by step.

[0038] (S301)

[0039] The arithmetic unit 2 acquires a plurality of projection images obtained by photographing the subject 203 from a plurality of directions. The arithmetic unit 2 can receive the projection images captured by the X-ray tomosynthesis apparatus 200, or can read out the projection images previously stored in the storage device 4 or the medical image database 11.

[0040] (S302)

[0041] The arithmetic unit 2 generates a tomosynthesis image using the plurality of projection images acquired in S301.

[0042] (S303)

[0043] The arithmetic unit 2 reads out the blur data for each coordinate in the imaging space. The blur data for each coordinate is, for example, Figure 4 stored in advance in the storage device 4 in the form of a table as shown. In Figure 4 the exemplified table, the blur data is associated with each three-dimensional coordinate. For example, the blur data Blr_111 is associated with the coordinate (x1, y1, z1), Blr_211 is associated with (x2, y1, z1), and Blr_nnn is associated with (xn, yn, zn).

[0044] In addition, the storage device 4 can store an expression for calculating the blur data based on the coordinates in the imaging space. In the case of storing the expression for calculating the blur data, the storage capacity of the storage device 4 can be saved.

[0045] Alternatively, the blur data can also be stored in the storage device 4 as a point spread function (PSF) generated by X-ray simulation or phantom imaging. In phantom imaging, the coordinates of a single point or a microsphere phantom smaller than the pixel size are used.

[0046] (S304)

[0047] The operation unit 2 corrects the tomosynthesis image generated in S302 using the blur data read out in S303. That is, the operation unit 2 functions as a correction unit for correcting the tomosynthesis image. For example, by performing deconvolution on the point spread function of each coordinate in the tomosynthesis image, the blur included in the tomosynthesis image is corrected. The operation unit 2 displays the corrected tomosynthesis image on the display device 7.

[0048] Through the processing flow described above, the blur included in the tomosynthesis image is corrected, so that the tip of the medical device inserted into the subject can be made clear. As a result, it does not pose an obstacle to the treatment using the medical device.

[0049]

Example 2

[0050] In Example 1, it was described that the tomosynthesis image is corrected using the blur data of each coordinate in the imaging space. The correction using the blur data is equivalent to a process of emphasizing high-frequency components, and sometimes white noise etc. included in the tomosynthesis image is emphasized and made obvious. Therefore, in Example 2, in order to suppress the obviousness of white noise etc., a means of limiting the range for correcting the tomosynthesis image is described. In addition, since the hardware configuration of the medical image processing device 1 in Example 2 is the same as that in Example 1, the description thereof is omitted.

[0051] Use Figure 5 An example of the processing flow executed in Example 2 will be described step by step.

[0052] (S301)

[0053] Similar to Example 1, a projection image is obtained.

[0054] (S302)

[0055] Similar to Example 1, a tomosynthesis image is generated.

[0056] (S503)

[0057] The operation unit 2 extracts a medical device region, which is a region of the medical device, from the tomosynthesis image generated in S302. Since the material of the medical device is known, a region where the luminance value of the tomosynthesis image is within a given range can be extracted as the medical device region. In addition, since the shape of the medical device is known, the medical device region can be re-extracted from the medical device regions extracted based on the luminance value according to the similarity of the shapes.

[0058] In addition, in the extraction of the medical device region, a machine learning engine generated by learning using tomographic images including known medical device regions as teaching data can be used. The machine learning engine is configured using, for example, a CNN (Convolutional Neural Network). The tomographic images used in the teaching data can be tomosynthesis images or X-ray CT images. Among them, when using X-ray CT images as teaching data, since the spatial resolution of X-ray CT images is higher, the extraction accuracy of the medical device region can be improved.

[0059] In addition, the position of the medical device region extracted from the tomosynthesis image can be corrected based on the region of the medical device extracted from the projection images used in the generation of the tomosynthesis image. The specific process will be described. (1) Extract the region of the medical device from each of the plurality of projection images used in the generation of the tomosynthesis image. (2) Perform a forward projection operation on the medical device region extracted from the tomosynthesis image at the same projection angle as each projection image, thereby obtaining forward projection data obtained by virtually projecting the medical device region. (3) Calculate the difference between the medical device region included in each forward projection data and the region of the medical device extracted from each projection image. (4) If the calculated difference falls within a given range, the process ends. If it does not fall within the given range, after correcting the medical device region in the tomosynthesis image, return to (2) and repeat (3) and (4). That is, the medical device region included in the tomosynthesis image is corrected so that the difference between the forward projection data obtained by performing a forward projection operation on the medical device region extracted from the tomosynthesis image and the region of the medical device extracted from the projection image falls within a given range.

[0060] (S504)

[0061] The operation unit 2 reads the fuzzy data of each coordinate of the medical device region and its peripheral region extracted in S503. The peripheral region of the medical device region refers to a region up to a given number of pixels, for example, 3 pixels, from the boundary of the medical device region.

[0062] (S505)

[0063] The operation unit 2 corrects the tomosynthesis image generated in S302 using the fuzzy data read in S504. That is, the range for correcting the tomosynthesis image is limited to the medical device region and its peripheral region. By limiting the range to be corrected to the medical device region and its peripheral region, the appearance of white noise and the like can be suppressed.

[0064] In addition, the blurring data used for correcting the tomosynthesis image can be adjusted using an adjustment coefficient set corresponding to the type of medical device. Since the X-ray attenuation coefficient varies depending on the type of medical device, the degree of blurring also changes. Therefore, the blurring data can be adjusted corresponding to the type of medical device. The adjustment coefficient for each type of medical device is stored in the storage device 4 in the form of a table as shown in Figure 6 For example, in the table illustrated in Figure 6 , the adjustment coefficient α1 is set for the catheter, α2 for the endoscope, and α3 for the guide sheath. The blurring data is adjusted by multiplying the adjustment coefficient for each type of medical device. By adjusting the blurring data corresponding to the type of medical device inserted into the subject 203, the medical device region becomes clearer.

[0065] The arithmetic unit 2 displays the corrected tomosynthesis image on the display device 7. An example of the display window is shown in Figure 7 In the display window illustrated in Figure 7 , the extracted medical device region 701 is overlapped and displayed on the tomosynthesis image of the chest, and an arrow 702 indicating the traveling direction of the medical device is displayed. The traveling direction of the medical device is calculated based on the tip and the bent portion of the medical device. In addition, the tip and the bent portion of the medical device are obtained by thinning the extracted medical device region 701. Furthermore, the three-dimensional shape of the extracted medical device region can be overlapped and displayed on the three-dimensional image generated from a plurality of tomosynthesis images.

[0066] Since the blurring included in the tomosynthesis image is corrected through the processing flow described above, the tip of the medical device inserted into the subject can be made clear. In addition, since the range to be corrected is limited to the medical device region and its peripheral region, the appearance of white noise and the like can be suppressed.

[0067] Alternatively, instead of setting the range for correcting the tomosynthesis image based on the extracted medical device region, the blurring data can be adjusted using an adjustment coefficient set corresponding to the contrast of the tomosynthesis image, and the adjusted blurring data can be used to correct the tomosynthesis image. By adjusting the blurring data using an adjustment coefficient set corresponding to the contrast of the tomosynthesis image, the degree of correction can be adjusted corresponding to the contrast of the tomosynthesis image.

[0068] Figure 8 An example of the relationship between the adjustment coefficient α and the contrast C is shown in Figure 8In this case, an adjustment coefficient α is illustrated which is minimized when the contrast C is a certain reference value and increases in absolute value corresponding to the contrast C. The blurring data of each coordinate is adjusted by the adjustment coefficient α set by multiplying the contrast C corresponding to the coordinate. That is, the medical device region and its peripheral region can be sharpened without extracting the medical device region.

[0069]

Example 3

[0070] In Example 1 and Example 2, it was described that the tomosynthesis image generated using the acquired projection image is corrected. If the temporal resolution of the corrected tomosynthesis image is insufficient, it may sometimes pose an obstacle to treatment and the like. The so-called temporal resolution means the shooting time required for generating the tomosynthesis image. In addition, on the premise that the X-ray source moves at a constant speed for shooting, the shooting time is proportional to the number of projection images. For a moving medical device, the shorter the shooting time, that is, the fewer the number of projection images, the smaller the position deviation of the medical device on the tomosynthesis image. On the other hand, the longer the shooting time, that is, the more the number of projection images, the greater the position deviation of the medical device on the tomosynthesis image. Therefore, in Example 3, it is described that in order to display a tomosynthesis image with a necessary temporal resolution for the position deviation of the medical device within an allowable range, the projection images used in the generation of the tomosynthesis image are selected. In addition, the hardware structure of the medical image processing apparatus 1 in Example 3 is the same as that in Example 1, so the description thereof is omitted.

[0071] Use Figure 9 An example of the processing flow executed in Example 3 will be described step by step.

[0072] (S901)

[0073] The arithmetic unit 2 sets the temporal resolution. That is, the arithmetic unit 2 functions as a temporal resolution setting unit.

[0074] In setting the temporal resolution, Figure 10 the illustrated operation window can be used. Figure 10 The operation window has a temporal resolution adjustment unit 1001. The temporal resolution adjustment unit 1001 is used when the operator adjusts the temporal resolution and is composed of, for example, a slider and a text box.

[0075] In addition, the arithmetic unit 2 can calculate the speed of the medical device based on the X-ray fluoroscopic image taken before the generation of the tomosynthesis image and set the temporal resolution based on the calculated speed. The greater the speed of the medical device, the higher the temporal resolution is set.

[0076] (S902)

[0077] The arithmetic unit 2 sets the number of projection images used in the generation of the tomosynthesis image based on the time resolution set in S901. The number of projection images is set to be larger when the set time resolution is lower, and smaller when the time resolution is higher.

[0078] (S903)

[0079] The arithmetic unit 2 acquires the projection images of the set number set in S902. The arithmetic unit 2 can give an instruction to the X-ray tomosynthesis apparatus 200 to capture the projection images of the set number, or can read out the projection images of the set number from the projection images previously stored in the storage device 4 or the medical image database 11.

[0080] (S302)

[0081] Similar to Embodiment 1, a tomosynthesis image is generated.

[0082] (S503)

[0083] Similar to Embodiment 2, a medical device region is extracted from the tomosynthesis image.

[0084] (S504)

[0085] Similar to Embodiment 2, the blurring data of each coordinate of the medical device region and its peripheral region is read out.

[0086] (S505)

[0087] Similar to Embodiment 2, the tomosynthesis image is corrected.

[0088] Since the blurring included in the tomosynthesis image is corrected by the processing flow described above, the tip of the medical device inserted into the subject can be made clear. In addition, since the tomosynthesis image is generated using the projection images selected corresponding to the set time resolution, a tomosynthesis image with the necessary time resolution can be displayed.

[0089] As described above, multiple embodiments of the present invention have been described. In addition, the present invention is not limited to the above embodiments, and structural elements can be deformed and embodied without departing from the gist of the invention. Further, multiple structural elements disclosed in the above embodiments can be appropriately combined. Furthermore, several structural elements can be deleted from all the structural elements shown in the above embodiments.

Claims

1. A medical image processing apparatus that processes a tomosynthesis image generated using a plurality of projection images obtained by photographing a subject into which a medical device is inserted at an angle range less than 180 degrees, characterized in that, Comprising: a storage unit that pre-stores blur data for each coordinate of the imaging space; and a correction unit that corrects the tomosynthesis image using the blur data, wherein the correction unit extracts a medical device area that is an area of the medical device from the tomosynthesis image, sets a correction range in the tomosynthesis image based on the medical device area, adjusts the blur data by multiplying by an adjustment coefficient set corresponding to whether the type of the medical device is a catheter, an endoscope, or a guiding sheath, and corrects the correction range using the adjusted blur data.

2. The medical image processing apparatus according to claim 1, wherein the storage unit stores a table that associates the blur data with each of the coordinates.

3. The medical image processing apparatus according to claim 1, wherein the storage unit stores an expression for calculating the blur data based on the coordinates of the imaging space.

4. The medical image processing apparatus according to claim 1, wherein the blur data for each coordinate stored in the storage unit is a point spread function generated by X-ray simulation or phantom imaging.

5. The medical image processing apparatus according to claim 1, wherein the correction unit calculates the traveling direction of the medical device based on the tip and the bent portion of the medical device obtained by thinning the medical device area.

6. The medical image processing apparatus according to claim 5, wherein the correction unit calculates the three-dimensional shape of the medical device.

7. The medical image processing apparatus according to claim 1, wherein the correction unit uses a machine learning engine generated by learning a tomographic image including a known medical device area as teaching data to extract the medical device area.

8. The medical image processing apparatus according to claim 7, wherein the teaching data includes an X-ray CT image.

9. The medical image processing apparatus according to claim 1, wherein the correction unit corrects the medical device area so that the difference between the forward projection data obtained by performing a forward projection operation on the medical device area and the area of the medical device extracted from the projection image falls within a given range.

10. The medical image processing apparatus according to claim 1, wherein the medical image processing apparatus further comprises: a time resolution setting unit that sets the time resolution of the tomosynthesis image, and the correction unit corrects the tomosynthesis image generated using the number of projection images based on the set time resolution.

11. The medical image processing apparatus according to claim 10, wherein the time resolution setting unit receives the time resolution input in an operation window.

12. The medical image processing apparatus according to claim 11, wherein The time resolution setting unit calculates the speed of the medical device inserted into the subject using an X-ray fluoroscopic image taken before the generation of the tomosynthesis image, and sets the time resolution based on the calculated speed.

13. An X-ray tomosynthesis apparatus that captures a plurality of projection images within an angular range of less than 180 degrees and generates a tomosynthesis image using the projection images, characterized in that it includes the medical image processing device according to claim 1.

14. A medical image processing method that processes a tomosynthesis image generated using a plurality of projection images of a subject into which a medical device has been inserted and taken within an angular range of less than 180 degrees, characterized in that, It includes: a reading step of reading out the blur data for each coordinate of the imaging space; and a correction step of correcting the tomosynthesis image using the blur data, in the correction step, a medical device region that is a region of the medical device is extracted from the tomosynthesis image, a correction range is set in the tomosynthesis image based on the medical device region, the blur data is adjusted by multiplying by an adjustment coefficient set corresponding to whether the type of the medical device is a catheter, an endoscope, or a guide sheath, and the correction range is corrected using the adjusted blur data.

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