Medical image processing device, X-ray diagnostic device and program

Abstract

To improve visibility of a device in an X-ray image.SOLUTION: A medical image processing device includes an image acquisition unit and a processing unit. The image acquisition unit acquires X-ray images sequentially collected in a part of a period of a cardiac phase of a subject into which a device is inserted. The processing unit specifies a characteristic region of the device included in a plurality of acquired X-ray images, and executes positioning for a position of a characteristic region in an X-ray image collected after a reference image in the plurality of X-ray images on the basis of a reference position as a position of the characteristic region specified in the reference image included in the plurality of X-ray images as the reference position.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments disclosed in the present specification and drawings relate to a medical image processing apparatus, an X-ray diagnostic apparatus, and a program. [Background technology]

[0002] Intravascular interventional treatment involves inserting devices such as catheters, guidewires, and stents into blood vessels and moving them precisely to the treatment site. The devices are then expanded to mechanically dilate the stenotic area, or the devices are placed inside the body. This treatment requires determining the location where the treatment will be performed and confirming that the treatment has been completed. Doctors typically confirm the procedure and its completion by referring to X-ray images generated and displayed in real time by an X-ray diagnostic device. For example, a guidewire is fitted with two (or sometimes one) X-ray-opaque metal markers to indicate the position of the balloon or stent. The doctor determines the location where the treatment will be performed by referring to the markers displayed on the X-ray image displayed on the monitor. Furthermore, the doctor confirms the completion of the treatment by referring to the device displayed on the X-ray image.

[0003] However, in endovascular interventional treatment of a beating organ such as the heart, the position of the device within the field of view may fluctuate due to factors such as heartbeat, body movement, and breathing. Therefore, when a device is inserted and multiple X-ray images are acquired, the device's position varies from X-ray image to X-ray image, reducing its visibility. To address this issue, a technique is known for detecting two markers in each X-ray image acquired sequentially and displayed on a monitor, and then performing deformation and alignment processing on the X-ray images so that the positions of the two markers in each X-ray image are the same as in previous images, thereby creating a moving image display in which the device appears virtually stationary. Another technique is known for highlighting the device by, for example, averaging multiple X-ray images corrected so that the positions of the two markers are the same. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-118834 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the embodiments disclosed in this specification and the drawings is to improve the visibility of the device in an X-ray image. However, the problem to be solved by the embodiments disclosed in this specification and the drawings is not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems. [Means for solving the problem]

[0006] A medical image processing apparatus according to an embodiment includes an image acquisition unit and a processing unit. The image acquisition unit acquires X-ray images sequentially collected during a portion of a cardiac phase of a subject having a device inserted inside the body. The processing unit identifies a characteristic region of the device included in the acquired X-ray images, and aligns the position of the identified characteristic region in a reference image included in the multiple X-ray images, which is acquired after the reference image, based on the reference position. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a medical image processing apparatus according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing an example of the alignment process and the addition process for an X-ray image depicting a stent. [Figure 3] FIG. 3 is a sequence diagram showing a processing procedure according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of the correspondence relationship between the electrocardiogram waveform and the periodic movement of the heart according to the first embodiment. [Figure 5] FIG. 5 is a diagram showing an example of the correspondence relationship between the irradiation period and pulse irradiation according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing an example of the alignment process and the addition process according to the first embodiment. [Figure 7] FIG. 7 is a diagram showing an example of details of the alignment process according to the first embodiment. [Figure 8] FIG. 8 is a diagram showing an example of details of the alignment process according to the first embodiment. [Figure 9] FIG. 9 is a block diagram showing an example of the configuration of an X-ray diagnostic apparatus according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of a medical image processing apparatus, an X-ray diagnostic apparatus, and a program will be described in detail with reference to the drawings. Note that the medical image processing apparatus, the X-ray diagnostic apparatus, and the program according to the present application are not limited to the embodiments described below.

[0009] (First embodiment) The configuration of a medical image processing apparatus according to the first embodiment will be described. Fig. 1 is a block diagram showing an example of the configuration of a medical image processing apparatus 1 according to the first embodiment. As shown in Fig. 1, the medical image processing apparatus 1 includes a processing circuitry 11, an input interface 12, a display 13, and a storage circuitry 14. The medical image processing apparatus 1 is connected to an X-ray diagnostic apparatus 2 via a network.

[0010] The X-ray diagnostic apparatus 2 includes a processing circuitry 27, and irradiates X-rays under the control of the processing circuitry 27. The X-ray diagnostic apparatus 2 then collects X-ray image data. For example, the X-ray diagnostic apparatus 2 according to the first embodiment collects X-ray image data based on electrocardiogram waveform information. Details of the X-ray diagnostic apparatus 2 will be described later.

[0011] The processing circuitry 11 reads out and executes programs stored in the memory circuitry 14, thereby functioning as an image acquisition function 111, a processing function 112, a corrected image generation function 113, and a display control function 114. The processing circuitry 11 is composed of, for example, a processor. The processing circuitry 11 acquires X-ray image data from the X-ray diagnostic apparatus 2 and performs image processing. The image acquisition function 111 is an example of an image acquisition unit. The processing function 112 is an example of a processing unit. The corrected image generation function 113 is an example of a corrected image generation unit. The display control function 114 is an example of a display control unit.

[0012] The image acquisition function 111 acquires X-ray image data via a network. The processing function 112 performs image processing on the X-ray image data to generate an X-ray image. Furthermore, the processing function 112 stores the generated X-ray image in the memory circuitry 14. The corrected image generation function 113 generates a corrected image based on the X-ray image. The display control function 114 displays various X-ray images on the display 13. Details of the image acquisition function 111, the processing function 112, the corrected image generation function 113, and the display control function 114 will be described later.

[0013] The input interface 12 is composed of an input device that accepts various input operations from a user. The input interface 12 accepts input operations from a user and outputs electrical signals corresponding to the accepted input operations to the processing circuit 11. For example, the input interface 12 may be composed of various buttons such as a mouse, keyboard, and trackball, a touchpad that allows input operations to be performed by touching the operation surface, a touchscreen that integrates a display screen and a touchpad, a non-contact input circuit using an optical sensor, and a voice input circuit. The input interface 12 may also be composed of a tablet terminal or the like that can wirelessly communicate with the device main body. Furthermore, the input interface 12 is not limited to those that have physical operation components such as a mouse and keyboard. For example, an electrical signal processing circuit that receives electrical signals corresponding to input operations from an external input device provided separately from the device and outputs the electrical signals to the processing circuit 11 is also included as an example of the input interface 12.

[0014] The display 13 is configured as a display device that displays various types of information. For example, under the control of the processing circuitry 11, the display 13 displays a GUI (Graphical User Interface), various X-ray images, and the like.

[0015] The memory circuitry 14 is configured, for example, with semiconductor memory elements such as RAM (Random Access Memory) and flash memory, a hard disk, an optical disk, etc., and stores various information, various data, and various programs. The memory circuitry 14 stores, for example, a GUI (Graphical User Interface), X-ray images, X-ray image data, etc. The memory circuitry 14 also stores programs that are executed by the processing circuitry 11 and cause the processing circuitry 11 to function as an image acquisition function 111, a processing function 112, a corrected image generation function 113, and a display control function 114.

[0016] An example of the configuration of the medical image processing device 1 according to this embodiment has been described above. With this configuration, the medical image processing device 1 according to this embodiment makes it possible to improve the visibility of devices in X-ray images. Specifically, the medical image processing device 1 aligns devices based on multiple X-ray images collected during a period when fluctuations in the device due to the subject's heartbeat are small in the X-ray images. As a result, the medical image processing device 1 performs device alignment processing without being affected as much by heartbeat, making it possible to improve the visibility of devices.

[0017] As described above, medical image processing devices can display video images that make devices appear virtually frozen during endovascular interventional treatment. Furthermore, medical image processing devices can also highlight devices by adding together multiple X-ray images that have been aligned using markers. For example, when treating coronary artery stenosis, doctors determine the placement position of a stent by observing fluoroscopic images. However, the radiopacity of the stent is lower than that of the marker, making it difficult to see. Therefore, medical image processing devices can align multiple fluoroscopic images using markers and add them together to highlight the stent, assisting in stent placement.

[0018] However, when highlighting a device, if a medical image processing device performs addition processing without distinguishing between images with large motion blur of the device due to pulsation and images with small motion blur, the device to be highlighted may be depicted unclearly.

[0019] Furthermore, medical image processing devices may not be able to accurately align devices when the device deforms due to the bending of blood vessels caused by pulsation. For example, medical image processing devices sequentially acquire multiple frames of collected images and align the device by performing image deformation and rotation processing using two markers detected from the previous frame image in chronological order as landmarks. During this process, the markers between frames are aligned, but the shapes of the device located between the two markers are not aligned. Therefore, if the acquired multiple frames of X-ray images include both images in which the device is significantly deformed due to pulsation and images in which the device is not significantly deformed, there is a possibility that parts of the stent or balloon depicted on the X-ray image other than the areas around the markers will be unclear.

[0020] FIG. 2 shows an example of alignment and summation processing for an X-ray image depicting a stent. Using FIG. 2, an outline of alignment processing P1 and summation processing for a stent bent due to pulsation will be described. Here, a medical image processing device performing alignment processing P1 acquires the latest X-ray image data and a predetermined number of X-ray image data acquired earlier from X-ray image data acquired sequentially in chronological order. For example, as shown in FIG. 2, the latest X-ray image data I11 and the X-ray image data I10 acquired earlier are acquired. Then, the X-ray image data I11 is aligned with the markers in alignment processing P1 based on the positions of two markers in the X-ray image data I10. Here, struts, which are the metal mesh portions of the stent, may deform as the blood vessel bends due to pulsation, causing changes in the strut mesh pattern.

[0021] However, as shown in Figure 2, the registration process P1 only performs image deformation on the markers, and does not perform image deformation on parts other than the markers. Then, in the addition process after the registration process P1, the X-ray image data I11 is added to the X-ray image data I10 with the struts still deformed. As a result, the shape and mesh pattern of the stent in the generated post-addition image I20 become unclear, reducing the visibility of the stent to the user.

[0022] Therefore, the medical image processing device 1 of this embodiment identifies the characteristic regions of the devices in X-ray images collected during a period when there is little movement due to pulsation based on electrocardiogram waveform information, and performs registration based on the characteristic regions of the devices. As a result, the medical image processing device 1 displays images in which the devices between frames are registered while suppressing the influence of cardiac pulsation.

[0023] Here, the procedure of processing by the medical image processing apparatus 1 will be described. FIG. 3 is a sequence diagram showing the procedure of processing by the medical image processing apparatus 1 and the X-ray diagnostic apparatus 2 in the first embodiment. First, an overview of each step in the sequence diagram will be described below, and then the details of the processing at each step will be described. Steps S101 to S107 in FIG. 3 are implemented by the processing circuitry 27 of the X-ray diagnostic apparatus 2. Step S111 is implemented by the processing circuitry 11 reading out a program corresponding to the image acquisition function 111 from the storage circuitry 14 and executing it. Steps S112 to S114 are implemented by the processing circuitry 11 reading out a program corresponding to the processing function 112 from the storage circuitry 14 and executing it. Step S115 is implemented by the processing circuitry 11 reading out programs corresponding to the corrected image generation function 113 and the display control function 114 from the storage circuitry 14 and executing them. Step S116 is implemented by the processing circuitry 11 reading out a program corresponding to the display control function 114 from the storage circuitry 14 and executing it. Furthermore, steps S117 to S119 are realized by the processing circuitry 11 reading out a program corresponding to the processing function 112 from the storage circuitry 14 and executing it.

[0024] As shown in FIG. 3, the processing circuitry 27 of the X-ray diagnostic apparatus 2 according to the first embodiment determines an irradiation period for irradiating an object with X-rays (step S101) and collects electrocardiogram waveform information (step S102). Then, the processing circuitry 27 determines whether or not it is irradiation timing based on the electrocardiogram waveform information and the reception status of an X-ray irradiation instruction (e.g., pressing a switch to irradiate X-rays) via the input interface (step S103). If it is not irradiation timing (step S103: No), the processing circuitry 27 returns to step S103. On the other hand, if it is irradiation timing (step S103: Yes), the processing circuitry 27 irradiates the object with X-rays (step S104). Then, the processing circuitry 27 collects X-ray image data (step S105) and transfers the collected X-ray image data to the medical image processing apparatus 1 (step S106). Then, the processing circuitry 27 determines whether the X-ray irradiation instruction has been completed via the input interface (step S107), and if the X-ray irradiation instruction has not been completed (step S107: No), the processing circuitry 27 returns to step S103. On the other hand, if the X-ray irradiation instruction has been completed (step S107: Yes), the processing circuitry 27 ends the processing in the X-ray diagnostic apparatus 2.

[0025] When the X-ray image data is transferred in step S106, the processing circuitry 11 of the medical image processing apparatus 1 according to the first embodiment sequentially acquires the X-ray image data (step S111). The processing circuitry 11 then identifies a feature region of the device in the acquired X-ray image data (step S112) and determines a reference image and a reference position (step S113). The processing circuitry 11 then performs a registration process based on the reference position (step S114) and generates a corrected image (step S115). The processing circuitry 11 then generates added image data based on the corrected image and displays the added image data on the display (step S116). The processing circuitry 11 then determines whether an end operation, which is an instruction to end a series of processes by the operator via the input interface 12, has been received (step S117). If the end operation has not been received (step S117: No), the processing circuitry 11 identifies a feature region of the device in newly acquired new image data (step S118) and performs a registration process (step S114). On the other hand, if the processing circuitry 11 receives an end operation (step S117: Yes), it ends the processing in the medical image processing apparatus 1 (step S119).

[0026] Next, details of processing by the medical image processing apparatus 1 and the X-ray diagnostic apparatus 2 according to the first embodiment will be described. An operator issues an instruction to irradiate X-rays by, for example, pressing a foot switch. When the input interface accepts the instruction to irradiate X-rays, the processing circuitry 27 of the X-ray diagnostic apparatus 2 irradiates X-rays only during a portion of the cardiac phase of the subject based on electrocardiogram waveform information to collect X-ray image data. Then, when the input interface no longer accepts the instruction to irradiate X-rays, the X-ray diagnostic apparatus 2 terminates the X-ray irradiation. Here, the portion of the cardiac phase includes a period in which the subject's heartbeat has relatively little movement. Furthermore, the period in which the electrocardiogram waveform fluctuates relatively little during one heartbeat, such as a period in which the heart's movement is small during ventricular systole and a period in which the heart's movement is small during ventricular diastole.

[0027] The heart contracts and expands during one heartbeat to pump blood. Specifically, during one heartbeat, the atria contract (P wave in the electrocardiogram waveform), followed by the ventricles contract (Q wave, R wave, and S wave). Next, the ventricles expand (T wave). At this time, the ventricular systole corresponds to the period from the peak of the R wave to near the end of the T wave, and the ventricular diastole corresponds to the period from near the end of the T wave to the peak of the next R wave. Here, the heart moves significantly during contraction or expansion, but moves relatively little during ventricular systole and part of ventricular diastole. Therefore, in this embodiment, X-ray image data is acquired during periods when the heart's movement is small during at least one of the ventricular systole and ventricular diastole.

[0028] The image acquisition function of the processing circuitry 27 of the X-ray diagnostic apparatus 2 determines an irradiation period, which is a period during which X-rays are continuously irradiated to a subject multiple times during one heartbeat, based on electrocardiogram waveform information. For example, the image acquisition function determines at least one of the systolic irradiation period and the diastolic irradiation period shown in FIG. 4 as the irradiation period based on electrocardiogram waveform information acquired by the X-ray diagnostic apparatus 2 from an electrocardiograph or the like. The image acquisition function may determine at least one of the systolic irradiation period and the diastolic irradiation period based on a specification from an operator via an input interface, or may determine the period based on preset information. Here, the systolic irradiation period is a period during which cardiac movement is small during ventricular systole. Similarly, the diastolic irradiation period is a period during which cardiac movement is small during ventricular diastole. FIG. 4 is a diagram showing an example of the correspondence between an electrocardiogram waveform and periodic cardiac movement according to the first embodiment.

[0029] Here, electrocardiogram waveform information refers to information regarding electrocardiogram (ECG) waveforms collected in real time from a subject, including the timings at which R waves and T waves occur, as determined by an electrocardiograph. For example, electrocardiogram waveform information is data recording the electrocardiogram waveform and the timings at which R waves and T waves occur (timestamp information). Note that electrocardiogram waveform information does not necessarily have to be information on detected R waves and T waves, and may be, for example, information on detected R waves only. Furthermore, electrocardiogram waveform information may also be information on detected timings at which not only R waves and T waves occur, but also P waves, Q waves, R waves, and S waves occur.

[0030] The image collection function reads out and determines the start point S of the determined irradiation period, the end point E of the irradiation period, and the X-ray irradiation interval from a preset. The X-ray irradiation interval is the pulse rate of continuous X-ray irradiation performed between the start point S of the irradiation period and the end point E of the irradiation period. For example, the image collection function determines the irradiation interval by reading out the pulse rate from preset X-ray conditions, etc. Here, a different pulse rate may be set for each irradiation period.

[0031] The presets are set based on the tendency of the cardiac phase, assuming the RR interval, ventricular systole, and ventricular diastole of the subject based on the tendency of the general cardiac phase of the human body. In other words, the presets determine the start point S of the irradiation period and the end point E of the irradiation period based on the possible heart rate variability of the human body, including the general RR interval and the occurrence rate of ventricular contraction and ventricular diastole in one heartbeat.

[0032] However, cardiac phase trends vary from subject to subject. For example, depending on the subject, the proportion of the systolic irradiation period per heartbeat may be higher than the preset, and the proportion of the diastolic irradiation period may be lower than the preset. Also, there is a possibility that the subject's RR interval may be α% longer than the preset RR interval. Therefore, the image acquisition function may compare the irradiation period read from the preset with actual electrocardiogram waveform information and adjust the start point S and end point E of the irradiation period. Specifically, the image acquisition function estimates the period during which the heart's movement is actually small based on the electrocardiogram waveform information and the subject's recent condition, and adjusts the start point S and end point E of the preset irradiation period so that the irradiation period matches the estimated period. Furthermore, the image acquisition function may increase or decrease the number of X-ray irradiations in accordance with the above-mentioned adjustment of the irradiation period.

[0033] FIG. 5 is a diagram showing an example of the correspondence between the irradiation period and pulse irradiation according to the first embodiment. Here, FIG. 5 shows the correspondence between the electrocardiogram waveform, two types of irradiation periods, and pulse irradiation corresponding to each irradiation period. The pulse irradiation corresponding to the systolic irradiation period is (a) systolic pulse irradiation shown in FIG. 5. The image acquisition function determines the start point S1 of the irradiation period corresponding to the first pulse irradiation in the systolic irradiation period, the end point E1 of the irradiation period corresponding to the last pulse irradiation in the systolic irradiation period, and the irradiation interval. For example, in the case of FIG. 5, the start point S1 of the irradiation period is determined based on the preset, and is determined from the time when the immediately preceding R wave is detected by the electrocardiogram waveform information to the time when the T wave is detected. S1 The end point E1 of the irradiation period is determined as 1 second after the T wave is detected based on the preset. E1 The image acquisition function determines the irradiation interval during the systolic irradiation period from the preset and determines the number of X-ray irradiations to be performed between the start point S1 and the end point E1 of the irradiation period. While FIG. 5 shows a case where X-rays are irradiated five times during the systolic irradiation period, the image acquisition function may increase or decrease the number of irradiations by comparing the preset with the most recent condition of the subject and electrocardiogram waveform information and changing the number of irradiations as appropriate.

[0034] Similarly, the pulse irradiation corresponding to the diastolic irradiation period is the diastolic pulse irradiation shown in Fig. 5 (b). The image acquisition function determines the start point S2 of the irradiation period corresponding to the first pulse irradiation in the diastolic irradiation period, the end point E2 of the irradiation period corresponding to the last pulse irradiation in the diastolic irradiation period, and the irradiation interval. For example, in Fig. 5, the start point S2 of the irradiation period is preset to be the time from the detection of the immediately preceding T wave from the electrocardiogram waveform information to the T wave. S2 The end point E2 of the irradiation period is determined to be the next detected R wave. The irradiation interval during the diastolic irradiation period is determined by reading out the preset. Although FIG. 5 shows a case where X-rays are irradiated 10 times during the diastolic irradiation period, the image acquisition function may change the number of irradiations as appropriate depending on the subject's recent condition, electrocardiogram waveform information, and the preset.

[0035] The start and end points of each irradiation period may be preset based on the time elapsed since the electrocardiograph detected the R wave. For example, for (a) systolic pulse irradiation, the start point S1 of the irradiation period may be set to T from the detection of the R wave. S1 The end point E1 of the irradiation period is set to T seconds after the detection of the R wave. E1-R Similarly, for (b) diastolic pulse irradiation, the start point S2 of the irradiation period may be set to T seconds after the detection of the R wave. S2-R The end point E2 of the irradiation period is set to T seconds after the detection of the R wave. E2-R It may be set to seconds later.

[0036] The start and end points of each irradiation period may be preset based on a commonly used period, such as the R-R interval, which refers to the time between R waves. Specifically, the timing of the most recent R wave is defined as 0% of the R-R interval, and the timing of the next R wave is defined as 100% of the R-R interval. In this case, for example, the start point S1 of the irradiation period for (a) systolic pulse irradiation may be set at 7% of the R-R interval, and the end point E1 of the irradiation period may be set at 28% of the R-R interval. Similarly, the start point S2 of the irradiation period for (b) diastolic pulse irradiation may be set at 35% of the R-R interval, and the end point E2 of the irradiation period may be set at 100% of the R-R interval. This allows the image acquisition function to determine the X-ray irradiation period by acquiring the most recent R wave and the R-R interval from electrocardiogram waveform information.

[0037] Although the image acquisition function described above has been described as determining the irradiation period as either the systolic irradiation period or the diastolic irradiation period, the embodiment is not limited thereto. The irradiation period may be determined as both the systolic irradiation period and the diastolic irradiation period. Furthermore, the irradiation period may be a combination of a portion of the systolic irradiation period and a portion of the diastolic irradiation period. For example, there may be cases where the shape of the device changes little between the systolic irradiation period and the diastolic irradiation period. Therefore, the image acquisition function predicts the amount of device movement caused by pulsation during the systolic irradiation period and the diastolic irradiation period based on electrocardiogram waveform information and a preset threshold value. Then, based on the predicted result, the electrocardiogram waveform information, and the irradiation interval, the image acquisition function selects a portion of the systolic irradiation period and a portion of the diastolic irradiation period, and determines the selected combination as the irradiation period. For example, the image acquisition function determines the irradiation period by combining the period from the start of the systolic irradiation period to the occurrence of the T wave and the period from the start of the diastolic irradiation period to the end of the diastolic irradiation period. In addition, the method of predicting the amount of movement of the device is not limited to using the electrocardiogram waveform information described above, and various other methods may be used, such as predicting the amount of movement of the device by collecting X-ray images in advance and calculating the amount of movement of the device.

[0038] Next, as shown in FIG. 3, the image collection function collects electrocardiogram waveform information collected in real time by the electrocardiograph. The image collection function then determines whether it is time for irradiation by determining whether the determined irradiation period is in progress and whether the input interface of the X-ray diagnostic device 2 has received an X-ray irradiation instruction from the operator. For example, if the determined irradiation period is in progress and an X-ray irradiation instruction has been received at the time of this determination, the image collection function controls the X-ray tube and X-ray detector to irradiate X-rays. If the determined irradiation period is not in progress and an X-ray irradiation instruction has been received at the time of this determination, the image collection function controls the X-ray tube and X-ray detector to irradiate X-rays during the next irradiation period. The image collection function then collects X-ray image data based on the X-rays detected by the X-ray detector. The image collection function then transfers the collected X-ray image data to the medical image processing device 1 via a network. If an X-ray irradiation instruction has not been received, the image collection function does not irradiate X-rays even if the current time falls within the irradiation period.

[0039] For example, when irradiating during the diastolic irradiation period, the image acquisition function continues to refer to the electrocardiogram waveform information. If an X-ray irradiation instruction is received outside the diastolic irradiation period, the image acquisition function continues to refer to the electrocardiogram waveform information until a T wave, which triggers the start point S2 of the irradiation period, is detected. When the occurrence of a T wave is detected, the image acquisition function irradiates the subject with X-rays TS2 seconds after the T wave (start point S2 of the irradiation period). The image acquisition function then irradiates pulses at the set irradiation interval A [fps] until the next R wave (end point E2 of the irradiation period). During this time, the image acquisition function sequentially collects and transfers X-ray image data.

[0040] The image acquisition function 111 acquires X-ray image data collected sequentially during a certain period in the cardiac phase of a subject with a device inserted into the body. For example, the image acquisition function 111 sequentially acquires X-ray image data via a network from the X-ray diagnostic apparatus 2. In this way, the image acquisition function 111 acquires X-ray image data collected during a period when cardiac movement is small and in which the device is depicted.

[0041] The processing function 112 identifies a feature region of a device included in each of the multiple X-ray image data. Specifically, the processing function 112 detects at least one feature of the device depicted in the multiple X-ray image data, and identifies the region of the X-ray image data containing the feature of the device as the feature region of the device. Here, the feature of the device refers to a device that has a relatively high X-ray opacity, such as a marker depicted in the X-ray image. The feature detection method may be a known method, such as template matching using a training image or feature detection based on generation of a high-frequency image containing high-frequency components of the X-ray image data. Alternatively, the feature may be detected based on the operator specifying the feature for at least one of the X-ray image data via the input interface 12. Furthermore, at least one feature is sufficient.

[0042] In identifying a characteristic region of a device, (1) a certain portion of the device is identified on an X-ray image based on the position of a detected feature, and the region of the certain portion or a region nearby the identified portion is identified as a characteristic region, or (2) the region of the detected feature itself or a region nearby the identified portion is identified as a characteristic region. Taking (1) as an example of a case in which a guidewire and a stent having two markers are depicted in multiple acquired X-ray image data, the processing function 112 detects the two markers, which are characteristic features of the device, for each of the multiple X-ray image data. Then, based on the positions of the detected two markers, the processing function 112 detects the guidewire connecting the two markers in the X-ray image data, and identifies the region in which the two markers and the guidewire are depicted, or a region nearby the region, as a characteristic region. In this way, the processing function 112 identifies a characteristic region including the markers, which are characteristic features of the device. Taking (2) as an example of the same case, the processing function 112 detects the two markers, which are characteristic features of the device, for each of the multiple X-ray image data. Then, the processing function 112 specifies the region in which both markers are rendered or its vicinity as a characteristic region, thereby specifying a characteristic region that includes the markers that are characteristic objects.

[0043] Next, the processing function 112 determines one of the multiple X-ray image data sets as reference image data for the alignment process P2. The processing function 112 then determines the position of the feature region in the reference image data as the reference position. Specifically, the processing function 112 determines the X-ray image data acquired first during a certain period of the subject's cardiac phase as the reference image data among the multiple acquired X-ray image data sets. For example, if the multiple X-ray image data sets are image data obtained by sequentially irradiating X-rays starting from the start point S2 of the diastolic irradiation period, the processing function 112 determines the image data acquired by irradiating X-rays at the start point S2 of the irradiation period as the reference image data. For example, the processing function 112 determines the position of the feature region of the device, which is the position of the region including two markers detected from the reference image data, as the reference position.

[0044] Note that the reference image data determined by the processing function 112 is not limited to the X-ray image data collected first during the irradiation period, as described above. For example, the processing function 112 determines an image determined in response to an operation by an operator as the reference image data. Specifically, in response to an X-ray irradiation instruction from the operator (for example, an operation of stepping on a foot switch), the processing function 112 determines the X-ray image data collected by the first irradiation after receiving the X-ray irradiation instruction as the reference image data. Furthermore, the X-ray image data N frames after the X-ray image data collected after receiving the X-ray irradiation instruction may be used as the reference image data. Alternatively, when the operator designates reference image data for multiple X-ray image data, the processing function 112 may designate the designated X-ray image data as the reference image data.

[0045] Alternatively, the processing function 112 may evaluate X-ray image data to determine the reference image data. Specifically, the processing function 112 evaluates the degree of curvature of the shape of each of the feature regions of a plurality of devices based on the shapes of the feature regions. Then, the processing function 112 determines an image in which the device has minimal curvature as the reference image data based on the evaluation result. The degree of curvature of the shape refers to the degree of device curvature between markers. For example, the processing function 112 sets the distance between two markers detected from each of the plurality of X-ray image data as the degree of curvature. Then, the processing function 112 calculates the degree of curvature (the distance between the two markers) for each of the plurality of X-ray image data, and if the degree of curvature is greater than a set threshold, it determines that the device has not been bent and extracts the corresponding X-ray image data. Then, the processing function 112 determines the X-ray image data collected earlier among the X-ray image data in which the degree of curvature is greater than the threshold as the reference image data. The threshold used to evaluate the degree of curvature is not limited to a fixed value, and may be the average value of the distance between the markers. At this time, the processing function 112 evaluates that the bending of the device is small when the difference (deviation) between the calculated bending degree and the average value is small. Specifically, the processing function 112 evaluates that the bending of the device is small for X-ray image data in which the difference between the distance between the markers calculated for each of the multiple X-ray image data and the average value of the distances is small.

[0046] Here, the method for calculating the curvature of a feature region including two markers is not limited to the above-described method of calculating based on the distance between the markers. Specifically, the processing function 112 may calculate the curvature based on the outline of the feature region.

[0047] Then, the processing function 112 aligns the positions of the feature regions in the X-ray image data collected after the reference image data in the plurality of X-ray image data based on the reference positions. Specifically, the processing function 112 executes a deformation process (alignment process P2) for aligning the shapes of the feature regions of the plurality of identified devices by deforming the shapes of the feature regions of the devices in the X-ray image data other than the reference image data to match the shapes of the feature regions of the devices in the reference image data.

[0048] For example, the processing function 112 transforms the image data by rotating, translating, enlarging, or reducing the X-ray image data acquired after the reference image data among the feature regions of the plurality of X-ray image data, thereby aligning the positions of two markers of the image data to be transformed with the positions of two markers of the reference image data.

[0049] The corrected image generation function 113 generates corrected image data from X-ray image data collected after the reference image data based on the alignment process. For example, the corrected image generation function 113 generates corrected image data that is the result of performing the alignment process P2 on multiple X-ray image data. Then, the corrected image generation function 113 stores the generated corrected image data in the memory circuitry 14.

[0050] The display control function 114 displays added image data generated by adding multiple pieces of corrected image data on the display 13. Specifically, the display control function 114 displays added image data generated by weighting and adding multiple pieces of corrected image data on the display 13. Thereafter, the display control function 114 generates added image data using the corrected image data of the set number of frames each time corrected image data is newly generated in chronological order. For example, if the preset number of frames is five, the display control function 114 generates added image data using the corrected image data of the immediately preceding five frames in chronological order, including the newly generated corrected image data, each time corrected image data is sequentially generated. The display control function 114 then displays the added image data on the display 13. As a result, the image displayed on the display 13 becomes an enhanced image of the device, depicting the latest device shape.

[0051] The display control function 114 may also subject the reference image data to the addition process. The weighting coefficients for the addition process described above may be preset. The weighting coefficients may be set using known methods. The addition process is not limited to adding the corrected image data for a set number of frames as described above, but may also be performed by adding new corrected image data to previously created added image data. For example, the display control function 114 may create added image data by adding newly created corrected image data in chronological order to the most recently created added image data.

[0052] With the above configuration, the medical image processing device 1 can process X-ray image data with little deformation of the device by using X-ray image data collected during a period when there is little movement due to pulsation based on electrocardiogram waveform information. As a result, the medical image processing device 1 can generate an image with high visibility of the device even when performing alignment processing such as the above-mentioned alignment processing P1, in which the marker area or its vicinity is used as a feature area (for example, alignment processing using only two markers as landmarks).

[0053] As described above, the medical image processing apparatus 1 can improve the visibility of devices by performing alignment processing on X-ray image data collected during periods when pulsation movement is minimal. However, X-ray image data collected during periods when pulsation movement is minimal may include X-ray image data in which a device such as a stent has been bent. Therefore, the medical image processing apparatus 1 can also perform alignment processing by taking into account the detailed shape of the characteristic region of the device. Below, an example will be described in which the medical image processing apparatus 1 depicts two markers and a guidewire and stent equipped with the markers in multiple X-ray image data.

[0054] The processing function 112 detects two markers, which are characteristic features of the device, for each of the multiple X-ray image data. Then, the processing function 112 detects a guidewire present between the two detected markers for the X-ray image data, using the two detected markers as landmarks. Next, the processing function 112 determines the region including the two markers and the detected guidewire as the characteristic region of the device. Note that the guidewire may be detected using a known method. For example, the guidewire may be detected by image processing that searches for an object with high X-ray opacity in the region near the marker. Furthermore, the processing function 112 may detect not only the marker and guidewire, but also a stent, and detect the region including the marker, guidewire, and stent as the characteristic region of the device.

[0055] Next, the processing function 112 determines reference image data for the alignment process P2 from the acquired multiple X-ray image data. As described above, the reference image data may be X-ray image data initially collected during a certain period in the cardiac phase of the subject, or X-ray image data determined in response to an operation by the operator.

[0056] As described above, the processing function 112 may evaluate the degree of curvature of the shape of each of the device's feature regions based on the shapes of the feature regions of the device, and determine an image with minimal device curvature as the reference image data based on the evaluation results. Here, the identified feature region of the device has a shape that follows the guidewire located between the markers. Based on this, the processing function 112 calculates the degree of curvature of the shape of the feature region by calculating the degree of curvature of the guidewire in the feature region of the device. Note that the processing function 112 may also calculate the degree of curvature of the shape of the feature region of the device based on the outline of the feature region of the device.

[0057] Then, the processing function 112 compares the calculated degree of curvature of the guidewire with a preset threshold value, and determines the X-ray image data in which the guidewire is least bent as the reference image data. Note that the threshold value used for evaluating the degree of curvature is not limited to a fixed value, but may be the average value of the degrees of curvature of the guidewire. In this case, the processing function 112 evaluates that the device is least bent when the difference (deviation) between the calculated degree of curvature and the average value is small. Here, the method for calculating the degree of curvature of the shape of the feature region is not limited to the method for calculating the degree of curvature of the guidewire described above. Specifically, the degree of curvature may be calculated from the distance between two markers. Alternatively, the degree of curvature of the shape of the feature region may be calculated by combining the degree of curvature of the guidewire and the distance between two markers.

[0058] FIG. 6 is a diagram illustrating an example of the alignment process and the addition process according to the first embodiment. An overview of the alignment process P2 and the addition process for a stent bent due to pulsation will be described using FIG. 6. For example, as shown in FIG. 6, the processing function 112 determines X-ray image data I10 from among multiple X-ray image data sets as reference image data I10. Note that X-ray image data I11 is X-ray image data acquired after the X-ray image data I10. In response to this, the processing function 112 executes alignment process P2, which deforms the shape of a feature region formed by two markers and the guidewire in the X-ray image data I11, relative to the shape of a feature region formed by two markers and the guidewire in the reference image data I10. The display control function I14 then executes addition process using the corrected image data generated after the alignment process P2 to generate and display X-ray image data I21. In this embodiment, alignment is performed to deform the shape of the feature region, and therefore the X-ray image data I21 generated by the addition process can improve the visibility of the device, as shown in FIG. 6. Details of the process will be described below.

[0059] Fig. 7 is a diagram showing an example of the details of the alignment process according to the first embodiment. Fig. 7 shows an example of the alignment process P2, which is composed of the alignment process P210 performed on the reference image data I10, the alignment process P211 performed on the X-ray image data I11, and the alignment process P220, and the X-ray image data I21 generated by the subsequent addition process.

[0060] The processing function 112 sets the positions of multiple feature points on the X-ray image data based on the positions of features in the feature regions of the device and the shapes of the feature regions. The processing function 112 sets the positions of the feature points for the feature regions of the multiple X-ray image data, thereby setting multiple feature points that reflect the shapes of the respective feature regions.

[0061] Specifically, the processing function 112 determines the guidewire detected from the X-ray image data as the reference line B0. Furthermore, the processing function 112 sets N feature points at regular intervals on the line segment between the markers on the reference line B0 based on the positions of the two detected markers. The coordinate of the feature point is defined as C. Next, the processing function 112 sets a normal line P to the reference line B0 at the coordinate C. Furthermore, the processing function 112 sets a reference line Bl from the reference line B0 in the positive direction of the normal line P. Similarly, the processing function 112 sets a reference line B2 from the reference line B0 in the negative direction of the normal line P. Note that the reference lines Bl and B2 are set at a regular distance from the reference line B0. Then, the processing function 112 sets a feature point at the intersection of the normal line P and the reference line Bl. Similarly, the processing function 112 calculates the intersection of the normal line P and the reference line B2 and sets it as the feature point. In other words, the processing function 112 sets N feature points on each of the reference lines B1 and B2. In this way, the processing function 112 obtains the shape of the feature region including the marker and the guidewire by setting the positions of ((number of reference lines) × N) feature points.

[0062] For example, as shown in the alignment process P210 in Fig. 7, the processing function 112 sets coordinates C10 and C50 as feature point positions at the positions of the two markers based on the positions of the markers detected with respect to the reference image data I10. The processing function 112 sets three points (coordinates C20, C30, and C40) at equal intervals on the line segment between coordinates C10 and C50 on the reference line B0. In other words, the processing function 112 sets five feature points (N=5) on the reference line B0.

[0063] Furthermore, the processing function 112 sets normal lines P1, P2, P3, P4, and P5 on the coordinates C10 to C50 as normal lines P to the reference line B0 at the coordinate C. Next, the processing function 112 sets the reference line B1 and the reference line B2 at a fixed distance from the reference line B0. Then, for each of the normal lines P1 to P5, the processing function 112 calculates coordinates C11, C21, C31, C41, and C51, which are intersections with the reference line B1, and sets these as feature points. Similarly, the processing function 112 calculates coordinates C12, C22, C32, C42, and C52, which are intersections with the reference line B2, for each of the normal lines P1 to P5, and sets these as feature points. As a result, the processing function 112 sets five feature points for each reference line, for a total of 15 feature points.

[0064] Then, the processing function 112 sets the same number of feature points for the X-ray image data I11. Specifically, the processing function 112 sets a total of 15 feature points by the alignment process P211, as shown in FIG.

[0065] Next, the processing function 112 matches the multiple feature points set in the feature region of the reference image data with the multiple feature points set in the feature region of the X-ray image data other than the reference image data. As a result, the processing function 112 performs a transformation process to deform the shape of the feature region of the device and match the shape of the feature region of the device in the multiple sets of X-ray image data. The transformation process may be performed using a known method for non-rigid registration. Furthermore, the transformation process does not need to strictly match each of the multiple feature points in the X-ray image data other than the reference image data with those in the reference image data, but may instead bring the multiple feature points closer to those in the reference image data than before the process.

[0066] Specifically, as shown in the alignment process P220 in Fig. 7, the processing function 112 performs alignment by moving the coordinates of the 15 feature points set in the X-ray image data I11 to the corresponding coordinates, using the coordinates of the 15 feature points set in the reference image data I10 as references. Then, the processing function 112 deforms the shape of the feature region in the X-ray image data I11 in accordance with the movement of the feature points. For example, as shown in the alignment process P220 in Fig. 7, the coordinates of the feature points in the X-ray image data I11 are moved to the coordinates of the corresponding feature points in the reference image data I10, which are connected by arrows.

[0067] The corrected image generation function 113 generates X-ray image data resulting from performing the alignment process P220 in FIG. 7 on the X-ray image data I11, and sets this as corrected image data I11. Then, the corrected image generation function 113 stores the generated corrected image data I11 in the memory circuitry 14.

[0068] The display control function 114 performs addition processing using corrected image data I11 generated based on the alignment processing P2 performed on the X-ray image data I11, corrected image data generated based on other X-ray image data (not shown) collected after the reference image data, and the reference image data I10. Here, the X-ray image data I21 shown in FIG. 7 is added image data I21 generated using the reference image data I10 and corrected image data I11. The display control function 114 displays the generated added image data on the display 13, and when new added image data is generated, displays the added image data on the display 13.

[0069] As described above, according to the first embodiment, the image acquisition function 111 acquires X-ray images sequentially collected during a portion of the cardiac phase of a subject with a device inserted inside the body. The processing function 112 identifies a characteristic region of the device included in the multiple X-ray images, and aligns the position of the characteristic region in the multiple X-ray images collected after the reference image based on the reference position, using the position of the identified characteristic region in the reference image included in the multiple X-ray images. As a result, the medical image processing apparatus 1 uses multiple frames of X-ray images collected in specific cardiac phases based on the electrocardiogram waveform information of the subject, and can use X-ray images in which device fluctuation between frames is reduced as the target for aligning the characteristic region of the device between frames. As a result, it is possible to display X-ray images in which device fluctuation is further reduced, improving the visibility of the device in the X-ray images.

[0070] Furthermore, according to the first embodiment, the image acquisition function of the X-ray diagnostic apparatus 2 identifies a portion of a cardiac phase based on the electrocardiogram waveform information of the subject, and controls the X-ray tube and the X-ray detector to irradiate X-rays during the identified portion of the cardiac phase and acquire multiple X-ray images. This allows the X-ray diagnostic apparatus 2 to acquire X-ray images during a portion of the cardiac phase based on the electrocardiogram waveform information of the subject, thereby acquiring X-ray images based on the movement of the heart due to the subject's beating. As a result, more accurate alignment processing can be performed, improving the visibility of devices in X-ray images.

[0071] Furthermore, according to the first embodiment, some periods in the cardiac phase are periods in which the subject's heartbeat moves relatively little. This allows the medical image processing apparatus 1 to align devices between X-ray images while suppressing the influence of heartbeats, thereby providing images in which the fluctuation of devices in the X-ray images is further reduced. As a result, the visibility of devices in the X-ray images is improved.

[0072] Furthermore, according to the first embodiment, the processing function 112 performs alignment by a deformation process in which, in the feature regions of the identified devices, the shapes of the feature regions of the devices in the images other than the reference image in the multiple X-ray images are deformed to match the shapes of the feature regions of the devices in the reference image included in the multiple X-ray images, thereby aligning the shapes of the feature regions of the multiple devices. This allows the medical image processing apparatus 1 to perform alignment processing between the shapes of the feature regions of the multiple X-ray images, thereby improving the accuracy of the alignment process. As a result, the visibility of the devices in the X-ray images is improved.

[0073] Furthermore, according to the first embodiment, the processing function 112 sets, for feature regions included in multiple X-ray images, multiple feature points that reflect the shapes of the feature regions, and performs deformation processing by matching or bringing multiple feature points set in feature regions of images other than the reference image closer to the multiple feature points set in the feature regions of the reference image. This allows the medical image processing apparatus 1 to align corresponding feature points between multiple X-ray images, thereby enabling highly accurate alignment processing that can accommodate various deformations. As a result, the visibility of devices in X-ray images is improved.

[0074] Furthermore, according to the first embodiment, the processing function 112 detects at least one feature of the device, identifies a region of the X-ray image containing the feature as a feature region of the device, and sets the positions of multiple feature points on the X-ray image based on the position of the feature in the feature region and the shape of the feature region. This allows the medical image processing apparatus 1 to identify the feature region of the device based on the feature, thereby enabling efficient setting of the feature region. Furthermore, because the position of the feature point is set based on the feature and the shape of the feature region, highly accurate alignment of feature points in each of multiple X-ray images can be achieved.

[0075] Furthermore, according to the first embodiment, the corrected image generation function 113 generates a corrected image from an X-ray image acquired after the reference image based on the alignment process. The display control function 114 displays an added image generated by adding together multiple corrected images on the display 13. This allows the medical image processing apparatus 1 to display an enhanced image of the device that has been aligned with high precision, thereby improving the visibility of the device.

[0076] (Variation 1) In the first embodiment described above, the image acquisition function 111 acquires X-ray image data collected by irradiating X-rays multiple times during an irradiation period. However, the embodiment is not limited to this. For example, the image acquisition function 111 may acquire, based on electrocardiogram waveform information, multiple X-ray image data collected by irradiating X-rays during a portion of a cardiac phase from multiple X-ray image data generated sequentially by inserting a device.

[0077] In this case, when the X-ray diagnostic apparatus 2 receives an X-ray irradiation instruction from the operator, it controls the X-ray tube and X-ray detector to irradiate X-rays multiple times at an arbitrary pulse rate. Then, the X-ray diagnostic apparatus 2 generates X-ray image data every time it collects X-rays that have passed through the subject. Furthermore, the X-ray diagnostic apparatus 2 collects the timing at which the passed X-rays are collected. At this time, an electrocardiograph connected to the X-ray diagnostic apparatus 2 collects electrocardiogram waveform information of the subject and transmits it to the X-ray diagnostic apparatus 2. Then, every time it performs X-ray irradiation, the X-ray diagnostic apparatus 2 associates the generated X-ray image data with the collection timing and electrocardiogram waveform information and stores them in a memory circuit (not shown).

[0078] The image acquisition function 111 then receives a designation of a partial period in the cardiac phase of the subject from a preset or an instruction via the input interface 12. The image acquisition function 111 acquires X-ray image data acquired during the designated period from the storage circuit of the X-ray diagnostic apparatus 2. For example, when instructed to acquire X-ray image data corresponding to the diastolic irradiation period shown in FIG. 4, the image acquisition function 111 reads and refers to a record linking the X-ray image data with its acquisition timing and electrocardiogram waveform information from the storage circuit, and acquires the X-ray image data acquired during the diastolic irradiation period. Then, as in the first embodiment described above, the processing function 112 performs alignment processing and addition processing on the acquired multiple X-ray image data.

[0079] As a result, the X-ray irradiation by the X-ray diagnostic apparatus 2 does not need to be controlled based on the cardiac phase corresponding to the electrocardiogram waveform.The medical image processing apparatus 1 can determine the X-ray image data on which to perform the series of alignment processes and addition processes described herein, based on the acquisition timing linked to the acquired X-ray image data and electrocardiogram waveform information.As a result, the medical image processing apparatus 1 can generate a highly accurate display image using X-ray image data with little movement due to pulsation, thereby improving the visibility of devices in the X-ray image.

[0080] (Variation 2) In the first embodiment described above, as in the registration process P2 shown in FIG. 7 , a method for setting multiple feature points that reflect the shape of a feature region of a device is described in which the guidewire is set as one of the reference lines, multiple reference lines are further set around the feature region, and multiple feature points are set on each reference line. However, the embodiment is not limited to this. For example, the processing function 112 may set multiple feature points only on the guidewire based on the positions of markers. FIG. 8 is a diagram showing an example of the details of the registration process according to the first embodiment. Here, in FIG. 8, X-ray image data I11 is X-ray image data acquired after reference image data I10. An example of the registration process P2 performed on the reference image data I10 and the X-ray image data I21 generated by the subsequent addition process is shown.

[0081] The processing function 112 sets N feature points at regular intervals on the line segment between the markers on the guidewire based on the positions of the two markers and the guidewire detected from the X-ray image data. The coordinates of the feature points are denoted as C. For example, as shown in FIG. 8, the processing function 112 sets feature point coordinates C1 and C5 at the positions of the two markers detected for each of the reference image data I10 and the X-ray image data I11. The processing function 112 then sets three points (coordinates C2, C3, and C4) at regular intervals on the line segment between the coordinates C1 and C5 on the guidewire for each of the image data. That is, the processing function 112 sets five feature points (N=5) on the guidewire for each of the image data. The processing function 112 then aligns the X-ray image data I11 by moving the coordinates of the feature points set for the reference image data I10 based on the coordinates of the feature points set for the reference image data I10.

[0082] When performing the alignment process P2 using multiple feature points on the guidewire, there may be cases where the accuracy of the alignment process P2 needs to be further improved. In this case, the processing function 112 evaluates the curvature of the shape of each of the feature regions of the device and excludes the shape of the feature region from the target for deformation processing based on the evaluation result. Specifically, the processing function 112 obtains the curvature of the shape of the feature region of the device by calculating the radius of curvature of an approximation circle that passes through the multiple feature points on the guidewire. The processing function 112 then evaluates the calculated curvature of each of the multiple X-ray image data sets using a preset threshold value and excludes X-ray image data evaluated as having a large curvature from the target for alignment process P2. As a result, the medical image processing device 1 uses X-ray image data in which pulsation movement is smaller than a certain condition, thereby enabling the display of X-ray images with reduced device movement. As a result, the visibility of the device in the X-ray image is improved.

[0083] The preset threshold value may be various values. For example, it may be a fixed value of the curvature radius or the average of the curvature radii of X-ray image data collected in the past. Alternatively, the threshold value may be set to allow an X% increase in the curvature radius relative to the X-ray image data collected one frame before. In this case, the threshold value is, for example, ((curvature radius of the X-ray image data collected one frame before) × X / 100). As a result, if the curvature radius of the evaluation object exceeds the threshold value, the processing function 112 excludes it from being a target for performing the deformation process. Similarly, the threshold value may be set to allow a Y% decrease in the curvature radius relative to the X-ray image data collected one frame before. In this case, the threshold value is, for example, ((curvature radius of the X-ray image data collected one frame before) × (1 − Y / 100)). If the curvature radius of the evaluation object is smaller than the threshold value, the processing function 112 excludes it from being a target for performing the deformation process.

[0084] Furthermore, the method of setting multiple feature points used to evaluate the curvature of the shape of a feature region is not limited to providing them only on the guidewire. Specifically, when multiple reference lines are provided around the feature region as shown in Fig. 7, the processing function 112 may set multiple feature points on each of the reference lines. Then, the processing function 112 may calculate the radius of curvature of an approximation circle that passes through the multiple feature points corresponding to each reference line, thereby more accurately evaluating the curvature of the shape of the feature region.

[0085] (Second embodiment) In the first embodiment, the medical image processing apparatus 1 detected markers as feature points of the device and identified a feature region of the device based on the detected feature points. Then, the medical image processing apparatus 1 performed a registration process to match the shape of the feature region of the reference image data with the shape of other X-ray image data. However, the embodiment is not limited to this. In the second embodiment, a process by the medical image processing apparatus 1 will be described in which the characteristic shape of a wire-like device is detected, and the region of the characteristic shape or its vicinity is defined as the feature region, and the registered X-ray images are sequentially updated and displayed. The wire-like device is, for example, a catheter or guidewire used in intravascular treatment. Hereinafter, the wire-like device will be referred to as a wire.

[0086] The medical image processing apparatus 1 according to the second embodiment is basically similar in configuration to the medical image processing apparatus 1 shown in Fig. 1, but some of the processing is different. Specifically, the medical image processing apparatus 1 according to the second embodiment is different from the medical image processing apparatus 1 according to the first embodiment in the processing contents of the processing function 112 and the display control function 114. The following description will focus on the differences from the first embodiment.

[0087] The processing function 112 deforms the shape of the wire feature region in the X-ray image data other than the reference image data, which is collected during a period when the movement due to pulsation is small and depicts the wire, to match the shape of the wire feature region in the reference image data. In this way, the processing function 112 executes a deformation process (alignment process P2) that matches the shapes of the wire feature regions.

[0088] The characteristic shape of the wire is, for example, a portion that is depicted as being particularly dark in the guidewire depicted in X-ray image data. Specifically, the distal end of the guidewire may have a structure that allows the surgeon to grasp the position of the tip of the guidewire by using a structure with a larger diameter or a higher density material than the other portions of the guidewire. In this case, X-rays that pass through the distal end of the guidewire are attenuated more than X-rays that pass through the other portions of the guidewire, and are depicted as being dark in the X-ray image data.

[0089] Alternatively, the characteristic shape of the wire may include a portion of the wire that is deformed to conform to the shape of the blood vessel when inserted into the blood vessel. Specifically, a characteristic contour shape may occur in the wire depicted in the X-ray image data. In the second embodiment, the characteristic contour shape is considered to be one of the characteristic shapes of the wire.

[0090] Therefore, the processing function 112 detects the characteristic shape of the wire described above, and defines the region where the shape is depicted or its vicinity as the characteristic region of the device. Then, as in the first embodiment, the processing function 112 aligns the characteristic shape of the wire in the other X-ray image data to match the characteristic region of the device in the reference image data. Note that the method for detecting the characteristic shape of the wire can be realized by a known method, such as extracting a portion of the wire with a large curvature. Furthermore, when multiple guidewires are inserted and depicted in the X-ray image data, the processing function 112 may detect the characteristic shapes of the multiple wires and align them individually.

[0091] The display control function 114 sequentially updates the corrected image data sequentially generated based on the alignment processing and displays it on the display 13. As a result, the display control function 114 sequentially displays X-ray image data with small wire movement in an aligned state, so that the movement of the wire in the X-ray image data can be suppressed and displayed. As a result, the medical image processing apparatus 1 makes it easier to observe wire-like devices, improving the visibility of wire-like devices.

[0092] (Other embodiments) In the first and second embodiments, an example has been described in which image processing according to the present application is performed on X-ray image data collected sequentially during a portion of the cardiac phase of a subject with a device inserted inside the body. However, the embodiments are not limited to this, and the medical image processing apparatus 1 may also perform image processing on X-ray image data generated sequentially for a subject with a device inserted inside the body. Specifically, for X-ray image data collected sequentially regardless of the cardiac phase, the processing function 112 according to other embodiments may identify a feature region of the device included in the X-ray image data, and perform deformation processing and addition processing to match the shape of the feature region of the reference image to the shape of other feature regions.

[0093] As a result, the medical image processing apparatus 1 aligns the shapes of the feature regions in the acquired X-ray image data regardless of whether the X-ray image data is collected in a specific cardiac phase, and can provide an image in which the fluctuation of devices in the X-ray image data is reduced, thereby improving the visibility of devices in the X-ray image data.

[0094] In the first and second embodiments, an example has been described in which a medical image processing apparatus 1 performs image processing according to the present application. However, the embodiments are not limited to this, and an X-ray diagnostic apparatus 2 may perform image processing according to the present application. FIG. 9 is a block diagram showing an example of the configuration of an X-ray diagnostic apparatus 2 according to another embodiment. As shown in FIG. 9, the X-ray diagnostic apparatus 2 is connected to an electrocardiograph 3.

[0095] The X-ray diagnostic apparatus 2 collects X-ray image data from the subject P. For example, when the X-ray diagnostic apparatus 2 receives an X-ray irradiation instruction from an operator via the input interface 28 while a device is inserted into the subject P and a procedure is being performed, the X-ray diagnostic apparatus 2 performs X-ray irradiation and collects X-ray image data. Then, the X-ray diagnostic apparatus 2 performs image processing such as alignment processing and addition processing according to the present application on the X-ray image data, and displays the processed image data on the display 29.

[0096] Here, the X-ray diagnostic apparatus 2 includes an X-ray high voltage device 21, an X-ray tube 22, an X-ray diaphragm 23, a top plate 24, an X-ray detector 25, a C-arm 26, a processing circuit 27, an input interface 28, a display 29, and a memory circuit 30. The X-ray high voltage device 21 generates a high voltage under the control of the processing circuit 27 and applies the high voltage to the X-ray tube 22. The X-ray tube 22 irradiates X-rays toward the subject P placed on the top plate 24 based on the high voltage applied by the X-ray high voltage device 21. The X-ray diaphragm 23 opens and closes diaphragm blades under the control of the processing circuit 27 to form an irradiation range (irradiation field) of the X-rays irradiated from the X-ray tube 22. For example, the diaphragm blades are formed in a flat plate shape using a material such as lead that blocks X-rays. The top plate 24 is a bed on which the subject P rests, and is placed on a couch (not shown).

[0097] The X-ray detector 25 is, for example, an X-ray flat panel detector (FPD) having detecting elements arranged in a matrix. The X-ray detector 25 detects X-rays emitted from the X-ray tube 22 and transmitted through the subject P, and outputs a detection signal corresponding to the detected X-ray dose to the processing circuitry 27. The C-arm 26 holds the X-ray tube 22, the X-ray diaphragm 23, and the X-ray detector 25 so that they face each other across the subject P. The C-arm 26 has a drive mechanism such as a motor and an actuator, and rotates and moves by operating the drive mechanism under the control of the processing circuitry 27, which will be described later. Note that, although FIG. 9 illustrates an example in which the X-ray diagnostic apparatus 2 is a single-plane apparatus, the embodiment is not limited thereto and may be a bi-plane apparatus.

[0098] An input interface 28 according to the other embodiments includes an exposure switch such as a foot switch in addition to the input interface 12 according to the first and second embodiments. The storage circuitry 30 has the same configuration as the medical image processing apparatus 1 according to the first and second embodiments, and stores programs that are executed by the processing circuitry 27 and cause the processing circuitry 27 to perform various functions. Note that the display 29 has the same configuration as the medical image processing apparatus 1 according to the first and second embodiments, and therefore description thereof will be omitted.

[0099] The processing circuitry 27 reads and executes programs stored in the storage circuitry 30, thereby functioning as a control function 271, an image acquisition function 272, a processing function 273, a corrected image generation function 274, and a display control function 275. The processing circuitry 27 is composed of, for example, a processor. The control function 271 supplies control signals to the X-ray high voltage device 21, the X-ray diaphragm 23, the tabletop 24, the X-ray detector 25, and the C-arm 26 to perform X-ray irradiation. The image acquisition function 272 supplies control signals to the X-ray tube 22 and the X-ray detector 25 to control the X-ray irradiation. The image acquisition function 272 generates X-ray image data based on a detection signal detected by the X-ray detector 25, and stores the generated X-ray image data in the storage circuitry 30. The processing function 273, the corrected image generation function 274, and the display control function 275 perform the same processing as the processing function 112, the corrected image generation function 113, and the display control function 114 described in the first and second embodiments, respectively.

[0100] Here, the term "processor" used in the description of the above-mentioned embodiment refers to a circuit such as a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)). Here, instead of storing a program in the memory circuit 14, the program may be directly embedded in the processor circuit. In this case, the processor realizes its function by reading and executing the program embedded in the circuit. Furthermore, each processor in this embodiment is not limited to being configured as a single circuit, but may be configured as a single processor by combining multiple independent circuits to realize its function.

[0101] Here, the program executed by the processor is provided in advance in a read-only memory (ROM) or a storage circuit. The program may be provided by being recorded on a computer-readable, non-transitory storage medium such as a compact disk (CD)-ROM, a flexible disk (FD), a recordable CD-R (CD-R), or a digital versatile disk (DVD) in a format that can be installed or executed on these devices. The program may also be provided or distributed by being stored on a computer connected to a network such as the Internet and downloaded via the network. For example, the program may be composed of modules including the above-described processing functions. In actual hardware, a CPU reads and executes the program from a storage medium such as a ROM, whereby each module is loaded into a main memory device and generated on the main memory device.

[0102] In addition, in the above-described embodiments and modifications, the components of each device shown in the drawings are functional concepts and do not necessarily have to be physically configured as shown. In other words, the specific form of distribution or integration of each device is not limited to that shown in the drawings, and all or part of the devices can be functionally or physically distributed or integrated in any unit depending on various loads, usage conditions, etc. Furthermore, all or any part of the processing functions performed by each device can be realized by a CPU and a program analyzed and executed by the CPU, or can be realized as hardware using wired logic.

[0103] Furthermore, among the processes described in the above-mentioned embodiments and modifications, all or part of the processes described as being performed automatically can be performed manually, or all or part of the processes described as being performed manually can be performed automatically using a known method.In addition, the information including the processing procedures, control procedures, specific names, various data and parameters shown in the above documents and drawings can be changed as desired unless otherwise specified.

[0104] According to at least one of the embodiments described above, it is possible to improve the visibility of the device in an X-ray image.

[0105] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0106] 1 Medical image processing device 2 X-ray diagnostic equipment 111 Image acquisition function 112, 273 processing functions 113, 274 Correction image generation function 114, 275 Display control function 13. Display 22 X-ray tube 25 X-ray detector 272 Image collection function

Claims

1. an image acquisition unit that acquires a plurality of X-ray images sequentially collected during at least one period in which the movement of the subject's heartbeat is relatively small during the cardiac phase of the subject in whose body the device is inserted; a processing unit that identifies a characteristic area of ​​the device included in the acquired multiple X-ray images, and aligns the position of the characteristic area identified in a reference image included in the multiple X-ray images based on the reference position with a position of the characteristic area in an X-ray image collected after the reference image in the multiple X-ray images; A medical image processing device comprising:

2. a corrected image generating unit that generates a corrected image from an X-ray image acquired after the reference image based on the registration process; The medical image processing apparatus according to claim 1 , further comprising: a display control unit that causes a display unit to display an added image generated by adding together the plurality of corrected images.

3. a corrected image generating unit that sequentially generates corrected images from X-ray images acquired after the reference image based on the alignment process; a display control unit that sequentially updates the generated corrected images and displays them on a display unit; The medical image processing apparatus according to claim 1 , further comprising:

4. The medical image processing device according to any one of claims 1 to 3, wherein the image acquisition unit acquires the plurality of X-ray images collected by irradiating X-rays during the one period from the plurality of X-ray images generated sequentially by inserting the device based on electrocardiogram waveform information.

5. The medical image processing device according to any one of claims 1 to 4, wherein the processing unit performs the alignment by a deformation process in which, in the feature regions of the identified plurality of devices, the shapes of the feature regions of the devices in images other than the reference image in the plurality of X-ray images are deformed to match the shapes of the feature regions of the devices in the reference image included in the plurality of X-ray images.

6. 6. The medical image processing apparatus according to claim 5, wherein the processing unit performs the deformation process by setting, for feature regions included in the plurality of X-ray images, a plurality of feature points that reflect the shapes of the feature regions, and by matching or bringing closer together a plurality of feature points set in feature regions of images other than the reference image to the plurality of feature points set in the feature regions of the reference image.

7. 7. The medical image processing apparatus according to claim 6, wherein the processing unit detects at least one feature of the device, identifies a region of the X-ray image containing the feature as a feature region of the device, and sets positions of the plurality of feature points on the X-ray image based on the position of the feature in the feature region and the shape of the feature region.

8. The medical image processing device according to any one of claims 5 to 7, wherein the processing unit evaluates the degree of curvature of the shapes of the feature regions of each of a plurality of devices, and excludes the shapes of the feature regions from the targets for performing the deformation processing depending on the evaluation results.

9. The medical image processing device according to any one of claims 1 to 8, wherein the processing unit defines the first image collected during a certain period in the cardiac phase among the plurality of X-ray images acquired by the image acquisition unit as the reference image.

10. 9. The medical image processing apparatus according to claim 1, wherein the processing unit determines an image determined in response to an operation by an operator as the reference image.

11. The medical image processing device according to any one of claims 1 to 8, wherein the processing unit evaluates the degree of curvature of each shape based on the shape of a characteristic region of a plurality of devices, and determines an image with a small degree of curvature of the device as the reference image based on the evaluation results.

12. A medical image processing device described in any one of claims 1 to 11, wherein the image acquisition unit acquires multiple X-ray images collected by irradiating X-rays during at least one period in the cardiac phase that is adjusted based on information about the subject.

13. an image acquisition unit that acquires X-ray images sequentially during at least one period in which the movement of the subject's heartbeat is relatively small during the cardiac phase of the subject in whose body the device is inserted; a processing unit that identifies each of the feature regions of the device included in the acquired multiple X-ray images, and executes a deformation process for matching the shapes of the feature regions of the multiple identified device in the multiple device feature regions by deforming the shapes of the feature regions of the device in images other than the reference image in the multiple X-ray images to the shapes of the feature regions of the device in the reference image included in the multiple X-ray images; a display control unit that adds, to the reference image, a plurality of transformed images generated from images other than the reference image based on the transformation processing, and displays the generated added image on a display unit; A medical image processing device comprising:

14. an X-ray tube for irradiating X-rays onto a subject during at least one period in which the movement of the subject's heartbeat is relatively small during a cardiac phase of the subject having a device inserted inside the body; an X-ray detector that detects X-rays that have passed through the subject; an image acquisition unit that controls the X-ray tube and the X-ray detector to acquire an X-ray image based on the X-rays detected by the X-ray detector; a processing unit that identifies a characteristic area of ​​the device included in a plurality of X-ray images collected during the one period, and uses a position of the characteristic area identified in a reference image included in the plurality of X-ray images as a reference position, and aligns a position of the characteristic area in an X-ray image collected after the reference image in the plurality of X-ray images based on the reference position; An X-ray diagnostic apparatus comprising:

15. 15. The X-ray diagnostic apparatus according to claim 14, wherein the image acquisition unit identifies at least one period in the cardiac phase based on electrocardiogram waveform information of the subject, and controls the X-ray tube and the X-ray detector to irradiate X-rays during the identified one period and acquire the plurality of X-ray images.

16. an X-ray tube configured to irradiate X-rays during at least one period in which the movement of the subject's heartbeat is relatively small during the cardiac phase of the subject having the device inserted inside the body; an X-ray detector that detects X-rays that have passed through the subject; an image acquisition unit that acquires sequentially created X-ray images based on the detected X-rays; a processing unit that identifies each of the feature regions of the device included in the plurality of X-ray images collected during the one period, and executes a deformation process for matching the shapes of the feature regions of the plurality of devices by deforming the shapes of the feature regions of the device in images other than the reference image included in the plurality of X-ray images in the identified feature regions of the device. a display control unit that adds, to the reference image, a plurality of transformed images generated from images other than the reference image based on the transformation processing, and displays the generated added image on a display unit; An X-ray diagnostic apparatus comprising:

17. a method for identifying a characteristic area of ​​the device included in a plurality of X-ray images collected sequentially during at least one period in which the movement of the heartbeat of the subject is relatively small in a cardiac phase of the subject in which the device is inserted into the body; and using the position of the characteristic area identified in a reference image included in the plurality of X-ray images as a reference position, aligning the position of the characteristic area in an X-ray image collected after the reference image in the plurality of X-ray images based on the reference position; A program that causes a computer to execute each process.

18. a method for identifying a characteristic region of a device included in a plurality of X-ray images sequentially collected during at least one period in which the movement of the subject's heartbeat is relatively small, in which a device is inserted into the body of the subject; and performing a deformation process for matching the shapes of the characteristic regions of the device included in the plurality of X-ray images by deforming the shape of the characteristic region of the device included in the plurality of X-ray images other than the reference image to the shape of the characteristic region of the device included in the plurality of X-ray images; adding a plurality of transformed images generated from images other than the reference image based on the transformation processing to the reference image, and displaying the generated added image on a display unit; A program that causes a computer to execute each process.

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