X-ray imaging apparatus

Abstract

Although it is desirable to perform imaging after knowing the state of respiration during X-ray testing, such imaging has not been carried out in actual medical sites at present. In addition, since the respiration state and information indicating under what respiration state the testing has been performed have not been stored along with a testing image, it had not been clear how much the respiration state has an effect on the test result during imaging. This X-ray imaging apparatus comprises: an X-ray imaging unit; a millimeter wave radar that irradiates a subject; a display unit that displays an X-ray image obtained by the X-ray imaging unit; and a control unit that displays, on the display unit, an output provided by the millimeter wave radar and a shutter time of the X-ray imaging unit. The X-ray imaging apparatus, by recording the state at the time of imaging instead of suppressing the movement of the body of the subject at the time of imaging, increases reproducibility, eliminates an increase in exposure amount due to re-testing, and provides great additional material when interpreting images.

Description

X-ray equipment

[0001] The present invention provides an X-ray imaging apparatus capable of obtaining an X-ray image of a subject that records the respiratory state of the subject when the image was taken.

[0002] X-ray images visualize the inside of a subject's body and are one of the important test results when diagnosing illnesses. That is, doctors determine the condition of organs and other organs shown in the X-ray image, as well as their relationship to other organs. However, it is not always the case that a subject is able to hold their breath and remain still during the scan. X-ray images taken while the subject is breathing cannot be said to accurately depict the patient's condition, as organs move with breathing. As a result, such X-ray images hinder doctors from making accurate judgments.

[0003] Patent Document 1 addresses the problem that conventional imaging methods, in which a diagnostic radiologist or doctor visually checks the patient's peak breathing and starts X-ray imaging when the peak occurs, make it difficult to take X-ray images of newborns, young children, and elderly people who are unable to stop breathing on their own. The document discloses a technology that uses a laser to check the patient's breathing condition, detects the peak point of breathing, and automatically performs imaging.

[0004] Furthermore, Patent Document 2 discloses a technology in which a marker M that appears as a shadow in an X-ray image is embedded in the body, the peak of breathing is detected by the movement of the marker M, and X-ray photography is performed in synchronization with the peak.

[0005] JP 2004-057559 A International Publication No. 2013 / 058055

[0006] The best imaging conditions for chest X-ray imaging are said to be when the diaphragm moves furthest toward the abdomen, at the end of inspiration, and when the diaphragm moves furthest toward the chest, at the end of expiration. The above-mentioned prior art was conceived to enable imaging at the peak point of breathing, even for those who are unable to create the peak point of breathing themselves.

[0007] On the other hand, for those who can create their own peak breathing points, the patient's breathing is stopped during imaging to prevent the effects of bodily movement, breathing, or heartbeat. However, relying on the skill of the radiological technologist or instructions to the patient (usually verbally, such as "Okay, breathe in, then hold your breath") does not allow for stable, highly reproducible X-ray images. Furthermore, in images of patients with poor inhalation close to exhalation, even normal images may show diaphragmatic elevation and cardiac enlargement, which may reduce transparency in the lower lung fields and lead to a misdiagnosis of pneumonia.

[0008] Therefore, in actual practice, it has been pointed out that obtaining X-ray images accompanied by information about the state in which they were taken is more useful when interpreting them than taking images at the peak of breathing.

[0009] Furthermore, in respiratory-gated imaging as shown in the prior art, if there is an erroneous detection due to noise or the like when detecting respiration, a re-examination (re-imaging) is necessary. However, unlike normal photography, X-ray imaging involves exposure to radiation. Therefore, there has been a demand for reliable X-ray imaging while checking the subject's respiratory status in real time.

[0010] The present invention has been conceived in view of the above-mentioned problems, and provides an X-ray imaging device that can display the subject's breathing (waveform) data and the time data when the X-ray was taken in the X-ray image of the subject.

[0011] More specifically, the X-ray imaging device according to the present invention is characterized by having an X-ray imaging unit, a millimeter wave radar that irradiates an object, a display unit that displays an X-ray image from the X-ray imaging unit, and a control unit that displays the output from the millimeter wave radar on the display unit.

[0012] The X-ray imaging device according to the present invention makes it possible to clearly grasp the respiratory state of the subject when an image was taken, so that the doctor's diagnosis is not hindered when interpreting the image. Furthermore, since the respiratory state of the subject can be grasped in real time during imaging, imaging can be performed reliably at the specified timing, reducing the need for reexaminations. As a result, radiation exposure can be reduced.

[0013] Millimeter-wave radar does not require the placement of markers inside the body and is non-invasive, placing less strain on the subject. In addition, because it can detect the body surface through clothing, there is no need to remove clothing to detect breathing and heart rate, which reduces the burden on the subject from the perspective of protecting privacy.

[0014] 1 is a diagram showing the configuration of an X-ray imaging device according to the present invention; FIG. 2 is a diagram showing an example of a body surface image; FIG. 3 is a flow chart showing the processing flow of a control unit; FIG. 4 is a diagram showing the movement of a body surface signal and the display of the shutter time; FIG. 5 is an example of a body surface image when imaging is performed during natural breathing; and FIG. 6 is an example of a body surface image in which the heart rate is displayed together with breathing.

[0015] The X-ray imaging apparatus according to the present invention will be described below with reference to the drawings and examples. Note that the following description exemplifies one embodiment of the present invention and one example, and the present invention is not limited to the following description. The following description can be modified within the scope of the present invention.

[0016] The X-ray imaging device 1 according to the present invention is intended for use with a living body that has breathing and a heartbeat. Therefore, the subject P is not limited to a human. The X-ray imaging device 1 may be a direct, indirect, or digital type.

[0017] 1 shows the configuration of an X-ray imaging device 1 according to the present invention. The X-ray imaging device 1 includes an X-ray imaging unit 10, a millimeter-wave radar unit 20, a control unit 30, an instruction input unit 32, and a display unit 34. The X-ray imaging unit 10 includes an X-ray detection unit 12 and an X-ray irradiation unit 14. The X-ray irradiation unit 14 includes an X-ray tube, an X-ray diaphragm, etc., and irradiates X-rays of a predetermined intensity for a predetermined time in response to an instruction signal Cxs from the control unit 30.

[0018] The X-ray detection unit 12 detects, on a two-dimensional plane, X-rays that are irradiated from the X-ray irradiation unit 14 and pass through the subject P. The X-ray detection unit 12 sends the detected X-ray intensity together with coordinate information of the detection point on the two-dimensional plane to the control unit 30 as an X-ray image signal Sig.

[0019] The millimeter-wave radar unit 20 radiates electromagnetic waves and detects the movement of the body surface of the subject P. The millimeter-wave radar unit 20 includes a synthesizer that generates electromagnetic waves (millimeter waves), an radiating antenna, and a receiving antenna. It may also include a mixer (measuring device) that calculates the change in distance or the movement speed from the millimeter-wave radar unit 20 from the radiated waves and reflected waves.

[0020] In response to an instruction signal Cry from the control unit 30, the millimeter-wave radar unit 20 irradiates radar waves toward the subject P and receives reflected waves from the subject P. A predetermined signal (information related to changes in distance or speed information) is obtained from the obtained reflected waves and irradiated waves, and is transmitted to the control unit 30 as radar data Sry.

[0021] The control unit 30 can suitably be a computer comprising a CPU (Central Processor Unit) and memory 30M. It has an internal clock (not shown) for managing the time. The control unit 30 receives instructions from the user via a signal Sop from an instruction input unit 32. The signal Sop includes a shutter signal Ssht. The control unit 30 also issues instructions to the X-ray imaging unit 10 and the millimeter-wave radar unit 20 (instruction signals Cxs and Cry) and receives signals from each device (X-ray image data Sig and radar data Sry).

[0022] The control unit 30 also generates a display image based on signals (X-ray image data Sig and radar data Sry) from the X-ray imaging unit 10 and the millimeter wave radar unit 20, and sends a corresponding video signal Svd to the display unit .

[0023] More specifically, the control unit 30 generates a video signal Svd40 from the X-ray image data Sig. Furthermore, time-stamped radar data (hereinafter referred to as "time-stamped radar data") TSry is generated as a body surface signal SSB using the radar data Sry and an internal clock. That is, the body surface signal SSB is a signal that represents the change in distance between the millimeter-wave radar unit 20 and the body surface at each time or the speed of movement of the body surface. The control unit 30 generates a video signal Svd42 from the body surface signal SSB. The body surface signal SSB will be described in detail in Figure 2 and subsequent figures.

[0024] When the control unit 30 receives the shutter signal Ssht from the instruction input unit 32, the control unit 30 generates a shutter time marker Dis as the video signal Svd42 based on the current time Tsht. That is, the video signal Svd42 may include the body surface signal SSB and the shutter time marker Dis.

[0025] The display unit 34 displays the video signal Svd as an image. More specifically, the video signal Svd 40 is displayed as an X-ray image 40, and the video signal Svd 42 is displayed as a body surface image 42 on the display unit 34. Only one of the video signal Svd 42 and the body surface image 42 may be displayed on the display unit 34.

[0026] The apparatus may also have a display unit 36. The display unit 36 ​​is provided in a position where the operator can see both the subject P and the display unit 36 ​​at the same time, and mainly displays the body surface signal SSB. This is because the operator can operate the shutter while simultaneously viewing the subject P's breathing state and the subject himself.

[0027] The video signal Svd is also recorded in memory 30M. It should be noted that instead of the video signal Svd, the X-ray image data Sig, the time-stamped radar data TSry, and the shutter time Tsht may also be recorded in memory 30M. These signals are referred to as image source data Xsd. This is because the video signal Svd (video signal Svd40 and video signal Svd42) can be reproduced based on these data.

[0028] The present invention can include recording media on which these data are recorded. That is, the present invention includes a recording medium on which X-ray image data Sig of at least a portion of the body of subject P, time-stamped radar data TSry, and shutter time Tsht are recorded. Alternatively, the present invention may be rephrased as a recording medium on which an X-ray image 40 and a body surface image 42 are recorded. Alternatively, the present invention may be rephrased as including a recording medium on which video source data Xsd or a recording medium on which a video signal Svd is recorded.

[0029] The control unit 30 can also read the video signal Svd or the video source signal Xsd of the subject P from the memory 30M and re-display it as the video signal Svd on the display unit 34. The video source signal Xsd and the video signal Svd may be data in different formats, but they may be data in the same format. The video source signal Xsd or the video signal Svd may also be transmitted to an external storage medium such as a USB or via a communication line such as the Internet.

[0030] The display unit 34 displays at least an X-ray image 40 of the subject P captured by the X-ray imaging unit 10 and a body surface image 42 of the subject P captured by the millimeter-wave radar unit 20. The display unit 34 may also display the shutter time Tsht. The X-ray image 40 is an X-ray transmission image of the subject P. FIG. 1 shows that the lungs PL and body PB of the subject P are displayed. The body surface image 42 represents the change in distance from the millimeter-wave radar unit 20 to the body surface of the subject P or the time lapse of the speed of movement of the body surface. In FIG. 1, the body surface image 42 is displayed in a small window at the bottom left of the screen of the display unit 34. The image on the display unit 34 in FIG. 1 shows a state in which X-ray imaging has already been completed.

[0031] When taking an X-ray, the body surface signal SSB is displayed on the display unit 36, and based on the movement of the subject P and the body surface signal SSB on the display unit 36, it is confirmed that the subject P has stopped breathing before taking the X-ray.

[0032] Fig. 2 shows only the body surface image 42. Referring to Fig. 2, the horizontal axis of the body surface image 42 represents time, and the vertical axis represents signal intensity. The body surface signal SSB is displayed on the body surface image 42. This indicates changes in the distance between the millimeter-wave radar unit 20 and the body surface of the subject P (the surface of the back in the case of Fig. 1), and as the intensity increases, the distance between the millimeter-wave radar unit 20 and the body surface decreases. In other words, the intensity increases during inhalation and decreases during exhalation. The period Tsp represents the period during which the subject P inhales and then holds his / her breath. Note that the distance may also be calculated based on the phase of the emitted wave and the reflected wave from the millimeter-wave radar unit.

[0033] A shutter time marker Dis is also displayed on the body surface image 42. The shutter time marker Dis is a marker that indicates the time when the X-ray image 40 was captured. It is generated based on the shutter time Tsht. In this way, the body surface image 42 displays the respiratory state of the subject P and the time Tsht when the X-ray image 40 was captured (here, the shutter time marker Dis is generated based on the time Tsht). Referring again to FIG. 1 , the display unit 34 displays the X-ray image 40 and the body surface image 42 on a single screen, making it clear at what point in the respiratory state of the subject P the X-ray image 40 was captured. The shutter time Tsht may also be displayed simultaneously on the body surface image 42. The shutter time Tsht may also be displayed not only as a time but also as a date (year, month, and day).

[0034] 3 shows the operation flow of the X-ray imaging apparatus 1 according to the present invention. This is the processing flow of the control unit 30. When the X-ray imaging apparatus 1 starts operation (step S100), an end determination is made (step S102). The end determination may be an intentional end by the user or an end by an emergency stop program of the X-ray imaging apparatus 1 itself. If it is to be ended (Y branch in step S102), it is stopped (step S104).

[0035] If the processing continues (N branch of step S102), the processing proceeds to the next step (step S106). In step S106, radar waves are emitted (step S106). Then, a body surface signal SSB obtained from the wave reflected from the subject P is displayed on the display unit 34 (step S108). After the body surface signal SSB is displayed, the process waits for the shutter to shoot the X-ray image 40 (N branch of step S110). While viewing the body surface image 42 displayed on the display unit 34, the operator presses the shutter to shoot the X-ray image 40 (Y branch of step S110 to step S112).

[0036] Figure 4 shows an example of the body surface signal SSB at step S108 in Figure 3. In Figures 4(a) to 4(d), the dashed lines are lines that will be displayed in the future, but are not yet displayed. The black circles are bright spots HP. In this case, in the body surface signal SSB, the bright spot HP moves from left to right on the screen over time, and the vertical axis shows the change in the distance between the millimeter-wave radar unit 20 and the body surface.

[0037] The body surface signal SSB is repeatedly swept from left to right every fixed time Tw. The trajectory of the bright spot HP is easily visible to the operator if it is left as an afterimage. Note that the trajectory of the bright spot HP disappears after each sweep, but the data may be saved.

[0038] In Figure 4(a), the subject P moved from inhalation to exhalation, and the intensity of the bright spot HP decreased. After completely exhaling, the subject moved to inhalation, took a breath, and then stopped breathing (Figure 4(b)).

[0039] The operator recognizes from the movement of the bright spot HP that the subject P has stopped breathing and presses the shutter to capture the X-ray image 40 (Y branch of step S110: FIG. 4(c)). When the shutter is pressed, the X-ray image 40 is captured and the shutter time Tsht is acquired (step S112). After that, the bright spot HP maintains the same intensity for a while, and as the subject exhales, the intensity of the bright spot HP decreases (FIG. 4(d)).

[0040] The X-ray image 40 and body surface image 42 (body surface signal SSB and shutter time marker Dis) are then displayed on the display unit 34 (step S114: see FIG. 1). The radar wave is then stopped (step S116), and the X-ray image 40, body surface signal SSB, and shutter time Tsht are all recorded in the memory 30M (step S118). The process then returns to the end determination (step S102). By repeating the above process, an X-ray image 40 recording the respiratory state of the subject P can be obtained.

[0041] 4, by displaying the respiratory state of the subject P over time on the display unit 36, the operator can visually check the subject P's breathing while performing X-ray imaging. Furthermore, after X-ray imaging, an X-ray image or X-ray photograph in which an X-ray image 40 and a body surface image 42 are simultaneously displayed remains as a record, which helps with interpretation later. In particular, by displaying and recording the body surface signal SSB after the shutter time marker Dis is displayed, it becomes easier to check the respiratory state of the subject P during X-ray imaging after imaging.

[0042] 5 shows an example of the body surface signal SSB and the shutter time marker Dis when the subject P is an elderly person, a newborn baby, an infant, or a small child who is unable to hold their breath. In other words, this is an example of a body surface image 42 when capturing an image of a person breathing naturally.

[0043] The subject P cannot hold his / her breath. Therefore, the operator visually determines when the subject P's inspiration has reached saturation, and then captures the X-ray image 40. However, it is not possible to know whether the subject P's inspiration has ended when the image is captured. As shown in Figure 5, if the shutter is pressed while the body surface signal SSB is displayed, a record is kept of the timing of the subject P's breathing at which the image was captured, which improves reproducibility and aids in image interpretation.

[0044] Furthermore, if the respiratory status at the time of imaging is known, the number of re-examinations can be reduced, which means that the amount of radiation exposure from X-rays can also be reduced. This is useful for newborns, infants, and young children, who are subject to the Bergogne-Tribondeau law.

[0045] As described above, the body surface signal SSB indicates changes in the distance between the millimeter-wave radar unit 20 and the body surface of the subject P. In the series of actions and operations of pressing the shutter based on the display of the body surface signal SSB, it is important that the body surface signal SSB can track the actual movement of the body surface.

[0046] In order to calculate the change in distance or the speed of movement from the irradiated wave and the reflected wave, the millimeter-wave radar unit 20 performs digital filtering on the signal from the reflected wave to suppress the influence of noise, and then performs fast Fourier transform processing to calculate frequency component information. Radar data Sry is calculated based on this frequency component information.

[0047] As an example of digital filtering, band-pass filtering using a biquad (BiQuad) filter can be suitably applied. In addition to applying band-pass filtering, this band-pass filtering can also be achieved by appropriately combining high-pass filtering and low-pass filtering to obtain the desired band-pass characteristics. If necessary, band-pass filtering, or high-pass filtering and low-pass filtering, may be performed multiple times. Biquad filters use the same arithmetic processing regardless of the filter function of the band-pass filter, high-pass filter, or low-pass filter. By setting six coefficients related to this arithmetic processing, the filter function and frequency characteristics can be easily changed, making them preferable in that they facilitate adjustments to obtain optimal band-pass filtering. Furthermore, with regard to the frequency characteristics of this band-pass filtering, the respiration frequency is generally in the frequency band of 10 to 15 bpm. Setting the low-pass cutoff frequency to approximately 50 times this frequency shortens the time until the waveform disturbance caused by ringing converges, thereby improving the tracking ability described above.

[0048] From the viewpoint of accuracy, it is preferable that the resolution of the fast Fourier transform process be 1 bpm (beats per minute) or less. In order to increase the resolution, it is desirable to increase the number of data per unit time to obtain a data group to be subjected to the fast Fourier transform process. When generating this data group, it is preferable to generate a data group including dummy data at a certain ratio to the actually acquired data, for example, by assigning dummy data following the actually acquired data. Although this slightly reduces accuracy, it is preferable in that it can improve tracking ability. Note that it is preferable to use a Blackman window as a window function when performing the fast Fourier transform process in order to suppress the influence of harmonics.

[0049] The body surface signal SSB detects a change in the distance between the millimeter wave radar unit 20 and the body surface of the subject P or a movement of the body surface. In this case, it is possible to detect a relatively large movement such as the breathing of the subject P as well as a small movement such as the heart rate.

[0050] 6 shows a body surface signal SSB_B due to respiration and a body surface signal SSB_P due to heartbeat displayed on a body surface image 42. This allows not only the respiratory state but also the heartbeat state to be recorded when capturing an X-ray image 40, which is extremely useful for later interpretation. Furthermore, X-ray imaging can be performed while breathing has stopped, while checking the timing when there is little movement between heartbeats.

[0051] The X-ray imaging apparatus according to the present invention can be suitably used not only as a simple X-ray imaging apparatus, but also for X-ray imaging of a living body with breathing and a heartbeat, such as in a computed tomography apparatus or a radiation therapy apparatus.

[0052] REFERENCE SIGNS LIST 1 X-ray imaging device 10 X-ray imaging unit 12 X-ray detection unit 14 X-ray irradiation unit 20 Millimeter wave radar unit 30 Control unit 30M Memory 32 Instruction input unit 34 Display unit 36 ​​Display unit 40 X-ray image 42 Body surface image P Subject PL Lungs PB Body part Cxs Instruction signal Cry Instruction signal Sry Radar data Sig X-ray image data Sop Signal Ssht Shutter signal Svd Video signal Svd40 Video signal Svd42 Video signal Xsd Video source signal SSB Body surface signal SSB_B Body surface signal (due to breathing) SSB_P Body surface signal (due to heartbeat) Tsht Shutter time Tsht Time Dis Shutter time marker Tsp Period HP Bright spot Tw Fixed time

Claims

1. X-ray imaging unit, A millimeter-wave radar that irradiates the subject, A display unit that displays the X-ray image taken by the aforementioned X-ray imaging unit, An X-ray imaging apparatus having a control unit that displays a body surface signal based on the output of the millimeter-wave radar and a shutter time marker representing the shutter time of the X-ray imaging unit on the display unit.

2. The X-ray imaging apparatus according to claim 1, wherein the output from the millimeter-wave radar represents the respiration of the subject.

3. The X-ray imaging apparatus according to Claim 2, wherein the millimeter-wave radar performs a fast Fourier transform after applying a digital filter to the signal from the reflected wave, and in the bandpass characteristic filtering of the digital filter, the low-pass cutoff frequency is set to about 50 times the frequency band of respiration.

4. The X-ray imaging apparatus according to claim 1, wherein the output from the millimeter-wave radar represents the heart rate of the subject.

5. X-ray images of at least a part of the subject's body, A body surface signal that shows the respiratory state of the subject over time for a certain period of time including the time when the X-ray image was taken, based on the output of the millimeter-wave radar irradiating the subject, the body surface signal after the shutter time marker representing the time of the image was displayed, A recording medium containing X-ray image data.

6. The recording medium according to claim 5, further recording data indicating the heart rate status of the subject over time.