Patent ID: 12220266

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of a medical image processing apparatus and a medical image processing method according to the present invention will now be described with reference to the accompanying drawings. It is noted that throughout the following description and the accompanying drawings, like reference signs are used to indicate components/elements having like functional configurations for the purpose of avoiding repeated description.

First Embodiment

FIG.1is a diagram illustrating a hardware configuration of a medical image processing apparatus1. The medical image processing apparatus1includes an arithmetic section2, memory3, a storage device4, and a network adapter5, which are interconnected therebetween through a system bus6such that they can transmit and receive signals. The medical image processing apparatus1is connected to a medical imaging apparatus10and a medical image database11via a network9such that they can transmit and receive signals. Further, the medical image processing apparatus1is connected to a display apparatus7and an input apparatus8. As used herein, the phrase “can transmit and receive signals” expresses a condition in which signals can be electrically or optically sent/transmitted and received among them or from one to another irrespective of wired or wireless connection.

The arithmetic section2controls operation of each element, which specifically is CPU (Central Processing Unit), MPU (Micro Processor Unit), and/or the like. The arithmetic section2loads and executes programs and data required to execute the programs which are stored in the storage device4, into the memory3in order to perform various types of image processing on medical images. The memory3stores the progress of a program and/or arithmetic processing which are executed by the arithmetic section2. The storage device4stores programs executed by the arithmetic section2and data required to execute the programs, which specifically is HDD (Hard Disk Drive), SSD (Solid State Drive), and/or the like. The network adapter5connects the medical image processing apparatus1to the network9such as LAN, telephone lines, the Internet and/or the like. Various data handled by the arithmetic section2may be transmitted to and received from the exterior of the medical image processing apparatus1via the network9such as LAN (Local Area Network).

The display apparatus7displays processing results of the medical image processing apparatus1, and the like, which specifically is a liquid crystal display and/or the like. The input apparatus8is an operation device through which an operator provides operation instructions to the medical image processing apparatus1, which specifically is a keyboard, a mouse, a touch panel, and/or the like. The mouse may be replaced with another pointing device such as a track pad, a track ball, and the like.

The medical imaging apparatus10is an X-ray tomosynthesis apparatus that acquires, for example, a plurality of projection images taken of an object under examination in many directions and generates tomographic images from the plurality of projection images, which will be described later with reference toFIG.2. The medical image database11is a database system that stores the projection images and the tomographic images acquired by the medical imaging apparatus10, correction images obtained by performing image processing on the tomographic images, and the like.

With reference toFIG.2, an overall configuration of an X-ray tomosynthesis apparatus200which is an example of the medical imaging apparatus10is described. InFIG.2, a direction perpendicular to the plane of paper is defined as an X axis, the direction of the long side is defined as a Y axis, and the direction of the short side is defined as a Z axis. The X-ray tomosynthesis apparatus200includes an X-ray source201, an X-ray detector202, a bed204, and a control console205.

The X-ray source201irradiates with X rays the object203under examination laid on the bed204. Upon the X-ray source201being applied with a high voltage depending on imaging conditions set via the control console205, the object203under examination is irradiated with X rays.

The X-ray detector202detects the X rays passing through the object203under examination to measure spatial distribution of the passing X rays. The X-ray detector202is disposed on the opposite side from the X-ray source201, and a plurality of detection elements are two-dimensionally arranged in the ZX plane. A two-dimensional projection image is generated based on a signal measured by the X-ray detector202.

In order to obtain a plurality of projection images taken of the object203under examination in many directions, at least one of the X-ray source201and the X-ray detector202is moved in the Z axis direction. The plurality of projection images thus obtained are used to generate tomosynthesis images which are tomographic images in a plane parallel to the bed204, i.e., in the ZX plane.

The control console205is apparatus for setting imaging conditions, generating tomosynthesis images, and performing display, which is configured with a so-called computer. On the control console205illustrated inFIG.2, a chest tomosynthesis image of the object203under examination is displayed. The control console205may be the medical image processing apparatus1illustrated inFIG.1.

In the X-ray tomosynthesis apparatus200, the angle range within which projection images are taken is limited to less than 180 degrees, e.g., from 20 degrees to 40 degrees. This causes distortion in a tomosynthesis image to be generated, and the distal end of a medical device inserted into the object203under examination such as a catheter, an endoscope, or the like will be blurred. If the distortion of the tomosynthesis image is large, the three-dimensional location of the distal end of the medical device cannot be identified, which in turn adversely affects treatment and the like. To avoid this, in a first embodiment, the processing flow for producing a clear tomosynthesis image is executed.

With reference toFIG.3, an example processing flow executed in the first embodiment is described for each step.

(S301)

The arithmetic section2acquires a plurality of projection images taken of an object203under examination in many directions. The arithmetic section2may receive projection images taken by the X-ray tomosynthesis apparatus200or may read projection images pre-stored in the storage device4or the medical image database11.

(S302)

The arithmetic section2uses the plurality of projection images acquired at S301to generate a tomosynthesis image.

(S303)

The arithmetic section2reads blur data at individual imaging space coordinates. The blur data at individual coordinates is prestored in the storage device4, for example, in table form as illustrated inFIG.4. In the table illustrated inFIG.4, the blur data is associated individually with three-dimensional coordinates. For example, blur data Blr_111is associated with coordinates (x1, y1, z1), blur data Blr_211is associated with coordinates (x2, y1, z1), and blur data Blr_nnn is associated with coordinates (xn, yn, zn).

The storage device4may also store a mathematical expression for calculating blur data from the imaging space coordinates. If a mathematical expression for calculating blur data is stored, the storage capacity of the storage device4can be saved.

It is noted that the blur data may be stored in the storage device4as Point Spread Functions (PSFs) generated by X-ray simulation or phantom imaging. For phantom imaging, a microspherical phantom of a size less than a comparable size of a pixel or coordinates of a point is used.

(S304)

The arithmetic section2corrects the tomosynthesis image generated in S302, using the blur data read in S303. Stated another way, the arithmetic section2functions as a correction section for correcting tomosynthesis images. For example, by performing the operation of deconvolution of PSFs at individual coordinates with the tomosynthesis image, the blurs included in the tomosynthesis image are corrected. The arithmetic section2causes the display apparatus7to display the corrected tomosynthesis image.

By the processing flow described above, the blurs included in the tomosynthesis image are corrected. This makes it possible to present clearly the distal end of the medical device inserted into the object under examination. As a result, treatment using the medical device cannot be adversely affected.

Second Embodiment

In the first embodiment, the correction of the tomosynthesis image using blur data at individual imaging space coordinates has been described. The correction using blur data corresponds to processing for enhancing high frequency components, and white noise and/or the like included in the tomosynthesis image may be enhanced and become obvious. To avoid this, a description in a second embodiment according to the present invention is given of limiting of the range in which the tomosynthesis image is corrected, in order to suppress the obvious existence of white noise and/or the like. The hardware configuration of medical image processing apparatus1in the second embodiment is identical with that in the first embodiment, and a description is omitted.

With reference toFIG.5, an example processing flow executed in the second embodiment is described for each step.

(S301)

As in the case of the first embodiment, the projection images are acquired.

(S302)

As in the case of the first embodiment, the tomosynthesis image is generated.

(S503)

The arithmetic section2extracts a medical device region from the tomosynthesis image generated in S302, the medical device region being a region of the medical device. Because the materials of the medical devices are known, a region in which the brightness values of the tomosynthesis image fall within a predetermined range may be extracted as a medical device region. Because the shapes of the medical devices are also known, a medical device region may be re-extracted based on shape similarity from the medical device regions which have been extracted based on the brightness values.

The medical device region may be extracted by using a machine learning engine that is generated by learning the tomographic images including the known medical device regions as teacher data. The machine learning engine is configured using, for example, CNN (Convolutional Neural Network). A tomographic image used as teacher data may be a tomosynthesis image or may be an X-ray CT image. However, when an X-ray CT image is used as the teacher data, the X-ray CT image has a higher spatial resolution, so that an improvement in accuracy with which the medical device region is extracted may be achieved.

Also, the position of the medical device region extracted from the tomosynthesis image may be modified based on the medical device region extracted from the projection images used for generation of the tomosynthesis image. The following is a description of specific steps: (1) a medical device region is extracted from each of the plurality of projection images used to generate the tomosynthesis image; (2) a forward projection operation is performed at a projection angle equal to that of each projection image on the medical device region extracted from the tomosynthesis image, in order to obtain forward projection data in which the medical device region is dummy projected; (3) a difference between the medical device region included in each piece of the forward projection data and the medical device region extracted from each projection image is calculated; and (4) if the calculated difference falls within a predetermined range, the procedure is ended, if it falls out of the predetermined range, the medical device region in the tomosynthesis image is corrected, and then the procedure returns back to step (2) to repeat steps (3) and (4). In short, the medical device region included in the tomosynthesis image is modified such that a difference between the forward projection data obtained by performing the forward projection operation on the medical device region extracted from the tomosynthesis image and the medical device region extracted from the projection images falls within a predetermined range.

(S504)

The arithmetic section2reads the blur data at individual coordinates in the medical device region extracted in S503and its surrounding regions. The regions surrounding the medical device region extend to a predetermined number of pixels, e.g., three pixels from the boundaries of the medical device region.

(S505)

The arithmetic section2corrects the tomosynthesis image generated in S302using the blur data read in S504. Specifically, the range in which the tomosynthesis image is corrected is limited to the medical device region and its surrounding regions. By limiting the correction range to the medical device region and its surrounding regions, the obvious existence of white noise and/or the like is suppressed.

The blur data used to correct the tomosynthesis image may be adjusted using an adjustment coefficient set depending on the type of the medical device. An X-ray attenuation coefficient varies depending on the type of the medical device, and thus the degree of blur also varies. To address this, the blur data may be adjusted depending on the type of the medical device. The adjustment coefficients for each type of medical device are stored in the storage device4, for example, in table form as illustrated inFIG.6. In the table illustrated inFIG.6, an adjustment coefficient α1is set for a catheter, an adjustment coefficient α2is set for an endoscope, and an adjustment coefficient α3is set for a guide sheath. The blur data is adjusted by being multiplied by an adjustment coefficient for each type of a medical device. A clearer media device region is produced by adjusting the blur data depending on the type of the medical device inserted into the object203under examination.

The arithmetic section2causes the display apparatus7to display the corrected tomosynthesis image.FIG.7illustrates an example display window. In the display window illustrated inFIG.7, the extracted medical device region701is superimposed and displayed on the tomosynthesis image of a chest, and an arrow702is also displayed to indicate the direction of movement of the medical device. The direction of movement of the medical device is calculated from the distal end and a bend of the medical device. The distal end and the bend of the medical device are obtained by performing the thinning processing on the medical device region701. A three-dimensional shape of the extracted medical device region may be superimposed and displayed on a three-dimensional image generated from a plurality of tomosynthesis images.

By the processing flow described above, the blurs included in the tomosynthesis image are corrected. This makes it possible to present clearly the distal end of the medical device inserted into the object under examination. Also, because the correction range is limited to the medical device region and its surrounding regions, the obvious existence of white noise and/or the like is suppressed.

Instead of setting a range in which the tomosynthesis image is corrected based on the extracted medical device region, an adjustment coefficient set according to contrast of the tomosynthesis image may be used to adjust blur data, and then the blur data after the adjustment may be used to correct the tomosynthesis image. By adjusting the blur data by using the adjustment coefficient set according to contrast of a tomosynthesis image, the degree of correction is adjusted according to the contrast of the tomosynthesis image.

FIG.8illustrates an example of the relationship between adjustment coefficients α and contrast C. The adjustment coefficients α are exemplified inFIG.8, which show a lowest value when the contrast C takes a reference value, and increase with the absolute value of the contrast C. The blur data at individual coordinates is adjusted by being multiplied by an adjustment coefficient α set according to the contrast C at the coordinates in question. That is, a clear media device region and clear surrounding regions thereof can be produced without extracting the medical device region.

Third Embodiment

In the first embodiment and the second embodiment, the correction of the tomosynthesis image generated using the acquired projection images has been described. If time resolution of the tomosynthesis image after correction is insufficient, treatment and/or the like may possibly be adversely affected. The time resolution means an exposure time required to generate the tomosynthesis image. In the case of the assumption that the X-ray source moves with constant velocity for exposure, the exposure time is in proportion to the number of projection images. The shorter the exposure time to the moving medical device, stated another way, the fewer the number of projection images, the smaller the misalignment of the medical device on the tomosynthesis image becomes. On the other hand, the longer the exposure time, stated another way, the larger the number of projection images, the larger the misalignment of the medical device on the tomosynthesis image becomes. To address this, a description in a third embodiment according to the present invention is given of selection of projection images to be used to generate a tomosynthesis image in order to display a tomosynthesis image with a time resolution required for misalignment of the medical device within an allowable range. The hardware configuration of the medical image processing apparatus1in the third embodiment is identical with that in the first embodiment, and a description is omitted.

With reference toFIG.9, an example processing flow executed in the third embodiment is described for each step.

(S901)

The arithmetic section2sets a time resolution. Stated another way, the arithmetic section2functions as a time resolution setting section.

An operation window as illustrated inFIG.10may be used to set a time resolution. The operation window inFIG.10has a time resolution adjustment portion1001. The time resolution adjustment portion1001is used by the operator adjusting the time resolution, and includes, for example, a slider bar and/or a text box.

The arithmetic section2may calculate a speed of the medical device from the fluoroscopic X-ray image taken prior to generation of a tomosynthesis image, and then set a time resolution based on the calculated speed. The higher the speed of the medical device, the higher the time resolution is set.

(S902)

Based on the time resolution set in S901, the arithmetic section2sets the number of projection images to be used for generation of a tomosynthesis image. The lower the time resolution set, the larger the number of projection images is set, whereas the higher the time resolution set, the smaller the number of projection images is set.

(S903)

The arithmetic section2acquires the number of projection images set in S902. The arithmetic section2may instruct the X-ray tomosynthesis apparatus200to capture the set number of projection images, or alternatively may read the set number of projection images from among the projection images pre-stored in the storage device4or the medical image database11.

(S302)

As in the case of the first embodiment, the tomosynthesis image is generated.

(S503) As in the case of the second embodiment, a medical device region is extracted from the tomosynthesis image.

(S504)

As in the case of the second embodiment, the blur data at individual coordinates in the medical device region and its surrounding regions is read.

(S505)

As in the case of the second embodiment, the tomosynthesis image is corrected.

By the processing flow described above, the blurs included in the tomosynthesis image are corrected. This makes it possible to present clearly the distal end of the medical device inserted into the object under examination. Also, because the tomosynthesis image is generated by using the projection images selected according to the set time resolution, the tomosynthesis image with a required time resolution is displayed.

The embodiments according to the present invention have been described. It is to be understood that the present invention is not limited to the above embodiments and may be embodied by modifying elements thereof without departing from the spirit or scope of the present invention. Further, a plurality of elements disclosed in the above embodiments may be combined as appropriate. Further, several elements of all the elements described in the above embodiments may be omitted.

REFERENCE SIGNS LIST

1. . . medical image processing apparatus2. . . arithmetic section3. . . memory4. . . storage device5. . . network adaptor6. . . system bus7. . . display apparatus8. . . input apparatus10. . . medical imaging apparatus11. . . medical image database200. . . X-ray tomosynthesis apparatus201. . . X-ray source202. . . X-ray detector203. . . object under examination204. . . bed205. . . control console701. . . medical device region702. . . arrow1001. . . time resolution adjustment portion