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WO2023093748A1 - 口腔锥形束x射线成像系统及其快速定位方法 - Google Patents

口腔锥形束x射线成像系统及其快速定位方法 Download PDF

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Publication number
WO2023093748A1
WO2023093748A1 PCT/CN2022/133641 CN2022133641W WO2023093748A1 WO 2023093748 A1 WO2023093748 A1 WO 2023093748A1 CN 2022133641 W CN2022133641 W CN 2022133641W WO 2023093748 A1 WO2023093748 A1 WO 2023093748A1
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Prior art keywords
oral
mode
imaging
shooting
image
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PCT/CN2022/133641
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English (en)
French (fr)
Inventor
余文锐
蔡云岩
徐燃
刘喆
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余文锐
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Priority claimed from CN202111404653.2A external-priority patent/CN114081524A/zh
Priority claimed from CN202211387129.3A external-priority patent/CN115937410B/zh
Application filed by 余文锐 filed Critical 余文锐
Publication of WO2023093748A1 publication Critical patent/WO2023093748A1/zh
Priority to US18/670,656 priority Critical patent/US20240389963A1/en

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    • A61B6/51—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications for dentistry
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Definitions

  • the present disclosure relates to an oral cone beam X-ray imaging system and a rapid positioning method thereof.
  • Routine oral X-ray imaging includes four methods, namely: oral CT shooting, oral panoramic shooting, head and side view and dental film shooting. Among them, integrating the three functions of oral CT shooting, oral panorama shooting and head side view shooting into one system is the mainstream solution of oral X-ray imaging system at present, which is usually called oral three-in-one system.
  • Oral CT imaging usually adopts 360° circular trajectory scanning, and then performs three-dimensional tomographic reconstruction to obtain oral CT data.
  • 360°rotational scanning process hundreds or even thousands of projections need to be performed, so the exposure time of each projection is very limited, and correspondingly, the X-ray radiation dose corresponding to each projection is limited, so usually a relatively large
  • the short distance from the radiation source to the detector is used to increase the radiation dose received by the detector.
  • the distance from the radiation source to the detector is generally 500-1000mm.
  • the oral panorama shooting adopts the method of fixing the relative position of the radiation source to the detector, and adopts a three-segment arc-shaped splicing trajectory, and the rotation center of the arc is pressed according to Move with certain rules.
  • the corresponding oral panorama also performs hundreds or even thousands of projections during the movement, and then reconstructs it through tomographic principles. Therefore, it also faces the same problem as oral CT that limits the radiation source to the detector due to the radiation dose.
  • Distance the distance from the conventional radiation source to the detector is also 500-1000mm.
  • Front and side views of the head are only two-dimensional direct imaging, and its dose limit is much lower than that of oral CT and panoramic shots of the oral cavity.
  • Shooting requires a sufficiently large distance from the source to the detector, usually above 1700mm.
  • the current mainstream three-in-one technology uses two sets of optical paths to simultaneously realize oral CT shooting, oral panorama shooting and head side view shooting.
  • the distance from the radiation source to the detector of a set of optical paths is 500-1000 mm, which is used to realize oral CT shooting and oral panoramic shooting.
  • Oral CT shooting uses a circular trajectory with a fixed rotation center
  • oral panoramic shooting uses a fixed relative position between the radiation source and the detector, and the oral panoramic shooting is achieved by moving the rotation center during the shooting process.
  • Another set of optical paths multiplexes the source of the previous set of optical paths, and then combines a linear array detector or a large-size (such as 40cm*30cm) flat panel detector, so that the distance from the source to the detector is more than 1700mm, to achieve Head side shot.
  • a linear array detector or a large-size (such as 40cm*30cm) flat panel detector so that the distance from the source to the detector is more than 1700mm, to achieve Head side shot.
  • the existing three-in-one system uses two sets of optical paths to simultaneously realize the functions of oral CT shooting, oral panorama shooting, and cranial lateral view shooting, and the system cost and system complexity are relatively high.
  • the image quality of oral panorama depends on the close correlation between the patient's own dental arch curve and the preset dental arch curve. Although multiple sets of preset dental arch curves can be used, the diversity of individual dental arches determines that this method still cannot Solve the root problem.
  • the positioning process in the oral panorama shooting process is also a relatively cumbersome process.
  • two-dimensional shooting is performed in frontal and lateral views of the head, its clinical needs have high requirements for the positioning of the shooting and strict requirements for the patient's posture.
  • the X-ray source, the left ear hole, and the right ear hole need to be in a straight line, and the head should not be tilted. Usually, it takes several minutes or even more than ten minutes to set up the front and side of the head, which seriously affects the shooting efficiency and patient experience.
  • the present disclosure provides an oral cone-beam X-ray imaging system.
  • the working modes of the system include oral CT shooting mode, oral panorama shooting mode, and skull front and side shooting mode.
  • the system includes: a radiation source configured to The measured object emits cone-beam X-rays; the flat-panel detector is configured to detect the X-rays passing through the measured object; the rotating drive device is configured to rotate the radiation source and the flat-panel detector, or make the measured object The measured object is rotated; the data processing device is configured to receive a working mode instruction to select a working mode control parameter group corresponding to one of the oral CT shooting mode, the oral panorama shooting mode and the head side view shooting mode; and The control device is configured to receive the selected imaging modulus control parameter group, control the rotary drive device, and/or control the radiation source and the flat panel detector to perform imaging and shooting, wherein the radiation The number of source, flat panel detector and rotary drive is one to form a one-way imaging system.
  • the present disclosure also provides a fast positioning method based on an oral cone beam X-ray imaging system, including: starting the fast positioning mode, emitting low-dose X-rays; receiving and reconstructing CT images, and obtaining the current position of the measured object posture; and based on the current posture, the imaging system performs adaptive positioning so as to perform imaging shooting in the oral panorama shooting mode or the head front and side shooting mode.
  • FIG. 1 is a schematic diagram of a cone beam X-ray imaging system according to an embodiment of the present disclosure.
  • FIG. 2 is a schematic diagram of a cone beam X-ray imaging system according to an embodiment of the present disclosure.
  • Fig. 3 is a schematic diagram of working in oral CT shooting mode according to an embodiment of the present disclosure.
  • Fig. 4 is a working schematic diagram of an anteroposterior and lateral skull shooting mode according to an embodiment of the present disclosure.
  • FIG. 5 is a schematic diagram of a data processing device according to an embodiment of the present disclosure.
  • Fig. 6 is a working schematic diagram of the first oral panorama shooting mode according to the embodiment of the present disclosure.
  • FIG. 7 is a schematic diagram of a data processing device according to an embodiment of the present disclosure.
  • FIG. 8 is a schematic diagram of a data processing device according to an embodiment of the present disclosure.
  • Fig. 9 is a working schematic diagram of the second oral panorama shooting mode according to the embodiment of the present disclosure.
  • Fig. 10 is a schematic diagram of determining virtual rotation axis parameters according to an embodiment of the present disclosure.
  • FIG. 11 is a flowchart of a method for generating a panoramic image according to an embodiment of the present disclosure.
  • FIG. 12 is an illustration of a target dental arch curve according to an embodiment of the present disclosure.
  • Fig. 13 is a flowchart of a fast positioning method according to an embodiment of the present disclosure.
  • Fig. 14 is a schematic diagram of radiation source adjustment according to an embodiment of the present disclosure.
  • FIG. 15 is a schematic diagram of a state after adjusting a roll angle according to an embodiment of the present disclosure.
  • Fig. 16 is a schematic diagram of a state after adjusting a yaw angle according to an embodiment of the present disclosure.
  • FIG. 17 is a schematic block diagram of the structure of a data processing device according to an embodiment of the present disclosure.
  • Fig. 1 is a schematic block diagram of the structure of a cone beam X-ray imaging system according to an embodiment of the present disclosure.
  • the cone beam X-ray imaging system 10 can work in an oral CT imaging mode, an oral panorama imaging mode, and an anteroposterior and lateral skull imaging mode.
  • images can be taken according to circular trajectory motion and then three-dimensional reconstruction can be performed for imaging.
  • the oral panorama shooting modes may include a first oral panorama shooting mode or a second oral panorama shooting mode.
  • variable-speed rotational shooting can be performed based on a circular trajectory, and multi-rotation center oral panoramic shooting can be realized through rearrangement processing.
  • the imaging system 10 may also include a fast positioning mode. This fast positioning mode is used for adaptive positioning of the imaging system. For example, in the case of selecting the oral panorama shooting mode or the front and side view shooting mode of the head, first start the fast positioning mode.
  • the shooting trajectory of the oral CT shooting mode is adopted, and the radiation dose of X-rays is lower than that of the oral CT
  • the radiation dose of X-rays in the shooting mode is used to perform adaptive positioning of the imaging system according to the positioning results of the fast positioning mode.
  • an imaging system 10 of the present disclosure may include a radiation source 100 , an X-ray detector 200 , a data processing device 300 , a control device 400 and a rotation driving device.
  • the radiation source 100 is capable of emitting X-ray cone beams to the measured object.
  • the detector 200 detects the X-rays passing through the measured object.
  • the detector 200 may be a flat panel detector, preferably a rectangular flat panel detector or a small flat panel detector.
  • the location of the X-ray shooting can be the head, jaw, oral cavity, etc. of the human body.
  • the rotation driving device may include the first rotation driving device 500 or the second rotation driving device 600 .
  • the rotary drive device includes the first rotary drive device 500
  • the radiation source 100 and the detector 200 can be synchronously driven to move around the measured object (patient) in a circular orbit, and the measured object is fixed.
  • the rotary drive device includes the second rotary drive device 600
  • the measured object can be controlled to rotate, and the radiation source and the detector are fixed.
  • the second rotation driving device 600 drives the rotation device 700 so that the measured object located on the rotation device 700 moves, so that the radiation source 100 and the detector 200 perform imaging and shooting along a circular trajectory.
  • the control device 400 can be used for controlling the first rotary drive device/second rotary drive device and for controlling the imaging of the radiation source and the detector.
  • the rotary drive device only includes the second rotary drive device 600 , that is, controls the rotation of the measured object to perform imaging and shooting.
  • the number of the radiation source 100, the detector 200 and the rotating driving device is one, so that a single-channel imaging system can be formed.
  • the present disclosure adopts the floor-standing structure described in FIG. 2 and includes a second rotary driving device to rotate the measured object.
  • the second rotary driving device can drive a rotating device in the form of a seat to make the measured object sitting on the seat The rotation is performed, but the radiation source 100 and the detector 200 are not rotated.
  • the distance SID between the radiation source 100 and the detector 200 may be 1.5m ⁇ 2.5m.
  • the distance between the radiation source 100 and the rotation axis is expressed as SAD, wherein the difference between SID and SAD is 0.2m-0.4m.
  • the SID is 1.7m
  • the difference between the SID and the SAD is 0.25m.
  • the X-ray imaging system can work in oral CT shooting mode, oral panoramic shooting mode, and head front and side shooting mode.
  • oral panoramic shooting mode and head front and side shooting mode you can first Perform quick positioning mode.
  • Fig. 3 shows a schematic diagram of working in oral CT shooting mode.
  • the measured object can rotate at a constant speed in the oral CT shooting mode.
  • the relative rotational paths of the radiation sources are shown in FIG. 3 by dashed circles. It can be seen from Fig. 3 that since the object to be measured rotates, the radiation source can be set to move in a circular trajectory relative to the object to be measured.
  • Fig. 4 shows a schematic diagram of working in the front and side shooting mode of the head.
  • the front view can be taken at the frontal position of 0°
  • the lateral view can be taken at the lateral position of 90°, where 0° is the angle perpendicular to the coronal plane of the skull, and 90° is the angle from 0° ° Rotate 90° clockwise or counterclockwise.
  • FIG. 5 shows a schematic diagram of a data processing device in the first oral panorama shooting mode.
  • the data processing device 300 may include a mode control unit 3002 , an instruction receiving unit 3020 , and a first panoramic image generating unit 3004 .
  • the command receiving unit 3020 receives an external operation mode.
  • the mode control unit 3002 retrieves a corresponding working mode control parameter set based on the received working mode command.
  • the control device 400 controls the relative rotation process of the object under test, the radiation source 100 and the detector 200 based on the working mode control parameter set retrieved by the mode control unit 3002 , and controls the radiation source 100 and the detector 200 to take pictures.
  • the instruction receiving unit 3020 receives an external command and the mode control unit 3002 controls the shooting in the oral CT shooting mode or the frontal and lateral skull shooting mode.
  • the panoramic image shooting can be realized through the first oral cavity panoramic shooting mode.
  • the measured object is controlled to rotate at a variable speed, as shown in FIG. 6 .
  • the working mode control parameter group includes at least the first oral panorama shooting mode control parameter group.
  • the first panoramic image generating unit 3004 performs the first panoramic image collected by the detector 200 during the relative rotation process (the relative rotation process between the radiation source 100 and the detector 200 and the measured object) controlled based on the first oral panoramic shooting mode control parameter group.
  • the sequence of two-dimensional projection data (that is, including a series of two-dimensional projection images) is rearranged to generate the first panoramic image of the oral cavity, and the relative rotation process controlled by the control parameter group based on the first oral panoramic shooting mode is a variable-speed rotation process .
  • the rearranging process may include: arranging the first sequence of two-dimensional projection data based at least on the position information of each imaging point of the oral cavity. Specifically, the radiation source position corresponding to each imaging point is obtained based on the position information of each imaging point in the oral cavity, and the projection position of each imaging point on the detector is obtained based on the radiation source position corresponding to each imaging point, and the selected
  • the two-dimensional projection data i.e. column data
  • the width of the column data depends on the interval between each imaging point, preferably , the intervals between each imaging point are the same) to obtain the first panoramic image.
  • the angular velocity curve of the variable-speed rotation process is generated based on the characteristic data of the oral cavity (preferably the shape characteristic data of the oral cavity, such as the dental arch curve), so that the rotation time between the adjacent radiation source positions corresponding to each imaging point is equal .
  • FIG. 7 shows a schematic diagram of a data processing device 300 .
  • the data processing device 300 may further include an angular velocity curve generating unit 3006 and a detector effective data position generating unit 3008 .
  • the angular velocity curve generation unit 3006 generates an angular velocity curve based on the selected oral cavity part characteristic data (for example, the selected dental arch curve).
  • the probe effective data position generating unit 3008 generates the probe effective data position based on the selected oral part feature data (for example, the selected dental arch curve).
  • the data processing device 300 may also include a memory.
  • the memory can store a variety of pre-generated dental arch curve data (ie oral cavity feature data).
  • the angular velocity curve generating unit 3006 and the valid detector data position generating unit 3008 respectively generate an angular velocity curve and a valid probe data position based on the dental arch curve data selected by the oral part feature selection command.
  • the first oral panorama shooting mode control parameter group is generated based at least on the angular velocity curve and the effective data position of the detector.
  • the detector 200 collects data at a preset collection rate to obtain a first sequence of two-dimensional projection data.
  • the variable speed rotation process may include at least one circular rotation process.
  • the first panoramic image generating unit 3004 performs the first panoramic image collected by the detector 200 during the relative rotation process (the relative rotation process between the radiation source 100 and the detector 200 and the measured object) controlled based on the first oral panoramic shooting mode control parameter group.
  • the sequence of two-dimensional projection data (that is, including a series of two-dimensional projection images) is rearranged to generate the first panoramic image of more than two rotation centers.
  • the first panoramic images of more than two rotation centers may be obtained by rearranging a series of two-dimensional projection images.
  • the appropriate dental arch curve data can be selected according to the patient's face shape, etc., and the X-ray imaging system generates the angular velocity curve and the effective data position of the detector for shooting according to the dental arch curve data.
  • a circular motion is made around the patient's head (oral area) according to the generated angular velocity.
  • the radiation source 100 emits X-ray cone beams, and the detector 200 collects X-ray projection images at a certain collection rate. Since the X-ray is a cone beam and the detector is a flat-panel detector, the projection line forms a certain angle with the line connecting the center of the radiation source and the detector.
  • the second oral panorama shooting mode may be used as the panorama image mode.
  • a second panoramic image generating unit may be used instead of the first panoramic image generating unit.
  • a second panoramic image generation unit may be further included.
  • the working mode control parameter set may at least include the second oral cavity panoramic shooting mode control parameter set.
  • the second panoramic image generator 3010 performs the second panoramic image acquisition by the detector 200 during the relative rotation process (the relative rotation process between the radiation source 100 and the detector 200 and the measured object) controlled based on the second oral panorama shooting mode control parameter group.
  • the sequence of two-dimensional projection data (ie, including a series of two-dimensional projection images) is interpolated to generate a second panoramic image of the oral cavity.
  • the relative rotation process controlled based on the second oral panorama shooting mode control parameter group is a uniform rotation process.
  • the uniform rotation process includes at least one circular rotation process.
  • the interpolation processing may include: judging whether each radiation source position of the detector in the process of collecting projection data is the radiation source target position calculated based on the position information of each imaging point of the oral cavity; and if a certain radiation source position If it is not the target position of the radiation source, the projection data collected at the radiation source position is weighted based on the position offset.
  • the position offset is the intersection point of the line connecting the radiation source position and the rotation center with the oral cavity and the adjacent imaging point
  • the weighted projection data is superimposed on the projection data corresponding to the adjacent imaging points (after all the projection data are processed, normalization processing is performed).
  • the interpolation processing may include: calculating the target position of the radiation source based on the position information of each imaging point of the oral cavity; , then the projection data of the radiation source target position is obtained based on the projection data collected at the radiation source position adjacent to the radiation source target position and corresponding to the imaging point.
  • the step of obtaining the projection data of the radiation source target position may include: performing linear interpolation on the projection data collected at two or more adjacent radiation source positions corresponding to the imaging point, so as to obtain the projection data of the radiation source target position.
  • the first panoramic shooting mode of the oral cavity with variable speed or the second panoramic shooting mode of the oral cavity at a constant speed can be used.
  • the angular velocity curve of the shooting process can be generated according to the situation of the dental arch curve, and the measured object is made to perform circular motion or partial circular motion according to the angular speed.
  • the measured object can be made to perform a circular motion or a partial circular motion at a constant speed. While moving, the radiation source can emit X-rays, and the detector can collect data at a certain rate, and finally reconstruct to achieve panoramic shooting.
  • the dental arch curve of the object to be measured is determined first, and the virtual rotation axis is determined.
  • the parameters of the virtual rotation axis are determined to reduce the impact of the imaging results of the imaging points on one side of the dental arch curve from the impact of the contralateral bone structure. In addition, they can also be determined to ensure that the imaging rays change continuously without sudden changes during shooting.
  • the contralateral bony structure mentioned above may include contralateral teeth, bones around the teeth, and cervical vertebrae.
  • an appropriate existing dental arch curve can be selected according to the face shape of the measured object, and a suitable dental arch curve can also be generated by measuring the measured object.
  • the virtual rotation axis parameter may be the position of the virtual rotation axis center.
  • the arc center can be used as the virtual rotation axis parameter as an example for illustration.
  • FIG. 10 shows a schematic diagram of determining the center and radius of a virtual rotation axis parameter according to an embodiment of the present disclosure. The case of three arcs is shown in FIG. 10 , but in the present disclosure, it is not limited to three arcs, and can be set according to the situation, for example, it can be four, five, and so on.
  • two reference teeth are selected, namely the first tooth and the second tooth.
  • the two reference teeth can be symmetrical teeth, and the upper jaw teeth or the lower jaw teeth can also be selected.
  • the selected reference teeth are shown in Figure 10 as the two lower canines.
  • the position C1 of the first tooth and the position C2 of the second tooth may be determined by means of laser positioning or the like.
  • the dental arch curve is divided into three arcs, namely the first arc A1, the second arc A2 and the third arc A3.
  • the dental arch opening and closing control angle ⁇ can be the line between the position C1 of the first tooth and the position C2 of the second tooth and the position C1 or C2 and the second tooth
  • the angle between the lines connecting the centers of the two arcs A2 and the dental arch length control coefficient r are determined based on the face shape of the measured object.
  • the linear distance between the center O1 of the first arc A1 and the position C1 of the first tooth is equal to the linear distance between the center O3 of the third arc A3 and the position C2 of the second tooth
  • the first arc A1 The linear distance between the center O1 and the position C1 of the first tooth is equal to the distance between the position C1 of the first tooth and the position C2 of the second tooth multiplied by the dental arch length control coefficient r, that is:
  • r
  • the radius r1 of the first arc A1 , the radius r2 of the second arc A2 and the radius r3 of the third arc A3 can be obtained.
  • the effective position of the detector can be that when imaging a certain imaging point, the radiation source is located at the corresponding position of the radiation source to emit X-rays, and the detector at the effective position of the detector can receive the X-rays and image the imaging point,
  • the effective position can also prevent other imaging points from interfering with the imaging of the certain imaging point (for example, preventing other imaging points from also imaging at the effective position (or causing overlapping imaging)).
  • the effective position is set so that only the certain imaging point can be imaged, while other imaging points cannot be imaged at this position.
  • the intersection point of the extension line and the motion track of the radiation source is the corresponding position of the radiation source corresponding to the imaging point, and Correspondingly, the effective position of the detector corresponding to the corresponding position of the radiation source will be obtained.
  • the radiation source can be rotated around the fixed rotation center OS, and the radiation source emits X-rays during the rotation. Then, according to the calculated relationship between the corresponding position of the radiation source and the effective position of the detector, the X-ray projection data of each imaging point is obtained.
  • the X-ray projection data of an imaging point measured at the effective position of the detector can be one column of data, or more than two columns of data.
  • one column of data it is a column of data measured at the intersection of the line between the imaging point of the extended dental arch curve and the center of the arc where the imaging point is located and the detector, or it can be the data near the column of data More than one column of data.
  • the connecting line between the imaging point C1 and the center O1 of the circle is extended.
  • the intersection of the connection line and the trajectory of the radiation source (dotted circle) is determined as the corresponding position of the radiation source.
  • the position of intersection between the connection line and the detector is determined as the effective position of the detector.
  • the corresponding position of the radiation source and the effective position of the detector of all imaging points can be obtained.
  • at least some of the imaging points in each imaging point form a predetermined angle between the connecting line of the radiation source and the radiation source and the fixed rotation center. And for different imaging points, the predetermined included angle is different.
  • the connecting line between these imaging points and the radiation source and the connecting line between the radiation source and the fixed rotation center may also coincide.
  • the measured object is rotated around the fixed rotation center OS, and the X-ray projection data of the X-ray emitted at the corresponding position of the radiation source corresponding to each imaging point at the effective position of the detector corresponding to each imaging point is obtained respectively.
  • the obtained projection column data is reconstructed to obtain a panoramic image of the oral cavity. For example, the reshooting process is performed for the first oral cavity panoramic shooting mode, and the above-mentioned interpolation processing is performed for the second oral cavity panoramic shooting mode.
  • a method for generating a panoramic image is also provided.
  • Fig. 11 shows a flowchart of a method for generating a panoramic image. As shown in FIG. 11 , the method for generating a panoramic image may include the following steps S102 to S116.
  • a three-dimensional image of the head of the subject to be measured is acquired.
  • the three-dimensional image of the head of the measured object can be reconstructed from the omni-directional two-dimensional projection image of the head of the measured object collected by the cone beam X-ray imaging system.
  • the cone beam X-ray imaging system acquires an omnidirectional two-dimensional projection image of the head of the measured object by performing a complete scan on the head of the measured object.
  • the cone-beam X-ray imaging system uses its own reconstruction geometric parameters to perform three-dimensional reconstruction on the omni-directional two-dimensional projection image of the subject's head to obtain a three-dimensional image of the subject's head.
  • the complete scan may be a 180-degree scan of the head of the measured object, or a 360-degree scan of the head of the measured object.
  • the detector of the cone-beam X-ray imaging system is biased, it needs to perform 360-degree scanning to obtain a full range of two-dimensional projection images.
  • the first cross-sectional image is determined, and the first cross-sectional image is the dental arch layer in the three-dimensional image.
  • the first cross-sectional image may be any cross-sectional image including a complete dental arch in the three-dimensional image.
  • the first cross-sectional image may be a cross-sectional image including the complete lower dental arch in the three-dimensional image.
  • the first cross-sectional image may also be a cross-sectional image with the clearest dental arch or the most obvious dental arch in the three-dimensional image.
  • the first cross-sectional image may also be a cross-sectional image with the densest dental arch in the three-dimensional image.
  • the cross-sectional image whose Z-axis coordinates in the three-dimensional image corresponds to the position of the dental arch in advance can be used as the first cross-sectional image.
  • the predetermined dental arch position may be the upper alveolar bone position and the lower alveolar bone position.
  • the position of the dental arch can be set in a pre-configured manner based on empirical values.
  • a pre-trained neural network may be used to process the three-dimensional image to determine the first cross-sectional image. For example, part of the cross-sectional images or all the cross-sectional images in the three-dimensional image can be input into the pre-trained neural network, and the neural network outputs the confidence level of each cross-sectional image, which indicates that the cross-sectional image is the first cross-sectional image The probability of , select a cross-sectional image with the highest confidence as the first cross-sectional image, or select an intermediate layer of multiple cross-sectional images with a confidence greater than a predetermined threshold as the first cross-sectional image.
  • the neural network for determining the first cross-sectional image can be trained by using the cross-sectional image marked as the densest dental arch and all the cross-sectional images of the three-dimensional images to which the cross-sectional image belongs.
  • the neural network may be, but not limited to, a convolutional neural network, a feed-forward neural network, or others, and the embodiments of the present disclosure do not limit the architecture and type of the neural network.
  • the clearest layer of the dental arch in the three-dimensional image may also be selected as the first cross-sectional image in response to a user operation. That is, manually select a cross-sectional image with the clearest dental arch in the three-dimensional image as the first cross-sectional image.
  • the first cross-sectional image is processed to obtain a bone-threshold segmented image containing teeth of the measured object.
  • bone threshold segmentation and Gaussian smoothing processing are performed on the first cross-sectional image to obtain a bone threshold segmentation image including teeth of the measured object.
  • substances such as soft tissue and water in the first cross-sectional image can be removed to obtain a bone threshold segmentation image containing only bones and teeth, and Gaussian smoothing is performed on the bone threshold segmentation image,
  • the noise in the bone threshold segmentation image can be removed, so as to obtain a bone threshold segmentation image with higher accuracy and better quality. This improves the quality of the bone thresholded segmented image, which in turn improves the accuracy of the dental arch curve.
  • step S108 the polar coordinates of each pixel in the bone threshold segmentation image in a predetermined polar coordinate system are determined. Specifically, each pixel in the bone threshold segmentation image can be mapped to a predetermined polar coordinate system through the conversion relationship from the rectangular coordinate system to the polar coordinate system, so as to obtain the polar coordinates of the position of each pixel in the bone threshold segmentation image express.
  • the predetermined polar coordinate system may be, but not limited to, a polar coordinate system whose pole is the center of gravity of the bone threshold segmented image.
  • step S110 according to the polar radius of the pixel point in the bone threshold segmented image where the predetermined angle is the polar angle and the pixel value is non-zero, the target polar radius corresponding to each predetermined angle is determined.
  • the predetermined angle includes a plurality of angles between 0° and 360° with intervals of predetermined values. In specific applications, an appropriate predetermined angle can be selected as required.
  • Step S110 may include the following content. Step a1: Determine the first pixel point with the smallest polar diameter and the second pixel point with the largest polar diameter among the non-zero pixel points with the first predetermined angle as the polar angle in the bone threshold segmented image.
  • the pole of the polar coordinate system is used as the starting point to radiate outward.
  • the first pixel with a non-zero value is the first pixel
  • the last pixel with a non-zero value is the first pixel.
  • the first predetermined angle refers to any predetermined angle.
  • Step a2 taking the average value of the polar diameters of the first pixel point and the second pixel point as the target polar diameter of the first predetermined angle. Taking the average polar diameter of the first pixel point and the second pixel point as the target polar diameter, the sampling point can be precisely positioned in the middle area of the tooth. Since the dental arch in the middle area of the tooth is the most obvious and complete, the sampling point is determined in this way. The accuracy of the dental arch curve can be further improved.
  • each predetermined angle and its target polar diameter are used as value pairs to form a sequence of value pairs, and the sequence of value pairs is the sampling point data of the dental arch curve.
  • the sampling point is a point in the predetermined polar coordinate system with a predetermined angle as the polar angle and a target polar radius at the predetermined angle as the polar radius.
  • each value pair in the sequence of value pairs may be arranged according to the corresponding predetermined angle from small to small. For example, if there are 36 pre-selected predetermined angles, the value pair sequence includes 36 value pairs, and each value pair includes the angle value of the predetermined angle and its corresponding target polar radius.
  • step S114 the dental arch curve of the measured object is obtained by fitting the sample point data.
  • the sampling point data can be used to fit the dental arch curve by using a polynomial fitting method.
  • polynomials of degree 5 polynomials of degree 6 and polynomials of degree 8 can be used to fit the dental arch curve.
  • the dental arch curve can be fitted according to the following formula (1):
  • r represents the target polar radius corresponding to the predetermined angle
  • ⁇ represents the predetermined angle
  • a 0 , a 1 , a 2 , a 3 , a 4 , and a 5 are all coefficients.
  • the five numerical pairs in the numerical pair sequence can be substituted into formula (1) to form a system of equations, and the coefficients a 0 , a 1 , a 2 , a 3 in formula (1) can be obtained by solving the system of equations by the least square method,
  • the values of a 4 and a 5 are substituted into formula (1) with the predetermined angle as the variable ⁇ to re-determine the target polar radius corresponding to each predetermined angle, and update the re-determined target polar radius to the sequence of value pairs, and finally use the updated The sequence of value pairs of is to obtain the dental arch curve.
  • a dental arch curve with higher accuracy can be obtained by mapping the bone threshold segmented image to the polar coordinate system and using a polynomial fitting method for fitting.
  • step S116 a panoramic image of the oral cavity of the measured object is obtained by using the dental arch curve.
  • step S116 may include the following steps b1 to b4.
  • each point on the dental arch curve is used to calculate the X-rays passing through the point during shooting, and obtain the projection data of the X-rays on the detector.
  • the radiation source - the corresponding point on the measured object - the projected point on the detector, and the three points are connected into a straight line.
  • step b2 the projection data of the X-rays passing through the point are accumulated according to the weight to obtain the imaging value of the point. In this way, a row of data can be obtained for a dental arch curve.
  • step b3 the dental arch curve is moved up and down in the vertical direction to obtain multiple rows of data, and all the rows are arranged in order to obtain a complete panoramic image of the oral cavity.
  • step S116 may include the following steps c1 to c2.
  • step c1 the target dental arch surface is determined with the dental arch curve as the generatrix and the Z-axis of the three-dimensional image as the guideline. Wherein, the Z axis is perpendicular to the first cross-sectional image.
  • Fig. 12 shows an example diagram of a target dental arch curve. Step c2, unfolding the curved surface of the dental arch to obtain a panoramic image of the oral cavity of the measured object.
  • step S116 various other applicable ways can also be used to obtain the oral panorama image through the dental arch curve.
  • the specific implementation manner of step S116 is not limited in this embodiment of the present disclosure.
  • the embodiment in Fig. 11 obtains the oral panoramic image by combining the above-mentioned embodiment with a more accurate dental arch curve, which can not only realize the real oral panoramic image shooting without increasing the mechanical structure, but also further improve the accuracy of the oral panoramic image , so that the accuracy of the oral panoramic image is closer to the shooting effect of the oral panoramic camera.
  • the image quality of the oral panoramic image is higher than that of the oral panoramic image.
  • it also supports the flexible selection of the cross section, which is convenient for users to adjust the oral panoramic image according to their needs. shape and surface fault location.
  • a CT image and an oral panorama image can be obtained in one scan.
  • the cross-sectional image can be flexibly selected, which is convenient for users to flexibly set the shape of the curved surface and the location of the curved surface fault, precisely specify the shape of the curved surface and the location of the curved surface fault, and reconstruct the panoramic image of the oral cavity multiple times in real time.
  • the actual dental arch of the measured object leads to problems such as the unavailability of oral panoramic images, and can bring more clinical value.
  • the imaging system of the present disclosure can realize three-in-one shooting of oral cavity based on circular trajectory, can realize shooting of CBCT, oral panorama image and front and side view on the circular trajectory X-ray imaging system, and can realize oral panoramic shooting of simulated multi-rotation center, A better fit of the periodontal surface is achieved.
  • the cone-beam X-ray imaging system of the present disclosure can realize real panoramic image shooting of the oral cavity without adding mechanical structures, instead of synthesizing panoramic images with reconstructed data, so the shooting speed is faster, and at the same time, the geometric control during shooting Less demanding.
  • the imaging system disclosed in the present disclosure has only one center of rotation, fewer motion mechanisms, and a simple structure. It only needs one detector and one radiation source.
  • the shooting mode can be to keep the radiation source and detector stationary while the measured object rotates, reducing machine control efficiency. Reducing the offset of the subject's head movement can reduce the ghost probability of the reconstruction result, improve the accuracy and image reading effect, and better assist doctors in judging patient information.
  • the imaging system can realize oral CT shooting mode shooting, oral panorama shooting mode shooting and skull front and side shooting mode shooting.
  • the imaging system can directly shoot the object under test.
  • the imaging system needs to first start the fast positioning mode to shoot, and then perform adaptive positioning of the imaging system according to the positioning results of the fast positioning mode, and then perform the shooting in the oral panoramic shooting mode.
  • adaptive positioning of the imaging system it is necessary to determine the dental arch curve of the measured object, and then perform adaptive positioning based on the determined dental arch curve as described above, and then complete the oral cavity based on the circular trajectory technology. Shooting in panorama mode.
  • the imaging system In the case of shooting in the front and side view of the head, the imaging system needs to first start the fast positioning mode to shoot, and then perform the adaptive positioning of the imaging system according to the positioning results of the fast positioning mode, and then take the head and side view mode shooting.
  • the imaging system may include a position control device 110 .
  • the control device 400 can control the position control device 110 to adjust the height of the radiation source and control the rotation of the rotating device, so as to realize the self-adaptive position of the imaging system.
  • the fast positioning mode uses low-dose X-rays and fast scanning to achieve fast positioning, thereby assisting the confirmation of setup.
  • the fast positioning mode can adopt the same motion trajectory as the oral CT shooting mode.
  • the difference from the oral CT shooting mode is: low X-ray dose, fast rotation speed, small number of projections and large reconstruction pixels.
  • the contour of the measured object can be obtained through the fast positioning mode, and the skull contour and dental arch contour of the measured object can be reconstructed.
  • Reconstruction pixel requirements are not high, radiation dose requirements are not high, and requirements for aliasing artifacts are not high. Therefore, lower radiation dose, fewer shots, faster rotation process, and larger pixels can be used for reconstruction.
  • the oral CT shooting mode uses 600 projection images
  • a single projection image uses an exposure time of 8ms, a rotation period of 30s, and a reconstruction pixel of 0.25mm
  • the fast positioning mode can use 200 projection images, an exposure time of 2ms, and 5s
  • the rotation period is 0.5mm for the reconstruction pixel.
  • a rapid positioning method based on the above imaging system is provided.
  • Fig. 13 shows a flow chart according to the fast positioning method.
  • a fast positioning mode is started, in which fast low-dose shooting is performed.
  • the CT image may be reconstructed by the data processing device, so as to obtain the current pose of the measured object.
  • the X-ray imaging system is positioned adaptively, such as adjusting the height of the radiation source and controlling the rotation of the rotating device.
  • the oral panorama shooting mode is activated for panoramic shooting or the head front and side view shooting mode is started for head front and side shooting, so as to obtain a panoramic image or a head front and side view image.
  • step S202 a step of selecting a photographing mode may also be included. For example, if the user selects an oral panorama photographing mode or a cephalometric and lateral photographing mode, step S202 is executed. However, if the oral CT mode is selected, shooting in the oral CT mode is performed directly.
  • step S206 the current dental arch curve of the measured object can be obtained by reconstructing the CT image, so that the X-ray imaging system can adjust itself according to the position required for shooting ( For example, refer to related content such as FIG. 10 ) to complete the positioning.
  • the above-mentioned positioning control device 110 can be used to perform position adjustment, for example, the radiation source is moved in the vertical direction to adjust the radiation source The height, and the rotation of the control rotating device.
  • the CT model is obtained, and the three spatial angles (pitch, yaw, roll) of the measured object relative to the standard pose are calculated by analyzing the data.
  • Pitch is the pitch angle, which is the angle of rotation along the X axis.
  • yaw is the yaw angle, which is the angle of rotation along the Y axis.
  • roll is the roll angle, which is the angle of rotation along the Z axis.
  • the three angle spaces can be fed back to the control device, and the control device controls the position control device to perform self-adaptive position.
  • the measured object can keep still (sitting on the rotating device and keep still), and adjust through the positioning control device.
  • the roll angle can be adjusted to match, then the yaw angle can be adjusted, and finally the final image can be rotated to adjust the pitch angle after the shooting is completed. After the adjustment is completed, shoot in the front and side view of the head.
  • the roll angle of the head of the measured object relative to the standard pose is obtained. Based on the obtained roll angle, the measured object is rotated by the rotating driving device, so that the left and right cranial parts of the measured object are approximately symmetrical, as shown in FIG. 15 .
  • a straight line passing through the center of the skull of the measured object divides the head into a left cranial part and a right cranial part.
  • the left cranial part and the right cranial part will be approximately symmetrical.
  • the head of the subject to be measured is projected along the X-axis direction, the more symmetrical the left and right skull parts are, the clearer the projection is, and the larger the gradient change of the projected image is. Therefore, when the head is rotated by an angle ⁇ ( ⁇ (- ⁇ /2, ⁇ /2)), the angle ⁇ at which the gradient of the forward projection has the smallest change is the roll angle.
  • the yaw angle of the head of the measured object relative to the standard pose is obtained. Based on the obtained roll angle, adaptive positioning can be performed by moving the position of the radiation source. After calculating the yaw angle, get the target coordinate point of the radiation source, and then control the movement of the radiation source so that the three points of the radiation source, the left ear hole and the right ear hole are collinear, as shown in Figure 16.
  • the yaw angle is calculated on the condition that the radiation source, the left ear canal and the right ear canal are collinear. Therefore, before the yaw angle is adjusted, the roll angle is adjusted first, so it can be considered that the Y coordinates of the left and right ear holes are the same or approximately the same. At this point, only the coordinate values of (X, Z) need to be considered.
  • the coordinates of the left ear hole are (X 1 , Y, Z 1 )
  • the coordinates of the right ear hole are (X 2 , Y, Z 2 )
  • the coordinates of the radiation source are (X 3 , Y 3 , Z 3 )
  • the coordinates of the radiation source need to be The distance that the radiation source needs to move in the Y direction is YY 3 .
  • the distance that the radiation source needs to move in the Z direction is The radiation source is moved by obtaining the distance to be moved in the Y direction and the Z direction, so that the radiation source, the left ear hole, and the right ear hole are collinear to complete the adaptive positioning.
  • the angle of the image can be adjusted after the image is taken. For example, the angle of the picture can be rotated based on the tooth parallel to the horizontal plane in the picture.
  • the content described above is the pose confirmation during the lateral view. After the confirmation of the lateral view, the frontal view can be taken according to the adjusted pose of the lateral view.
  • the calculation of the three spatial angles can be realized by the angle calculation unit of the data processing device 300 .
  • the data processing apparatus 300 of the present disclosure may be implemented in the form of computer software architecture, or may be implemented in the form of hardware architecture based on a processing system.
  • FIG. 17 is a schematic block diagram of the structure of a data processing device 300 using a hardware implementation of a processing system according to an embodiment of the present disclosure.
  • the data processing device 300 may include corresponding modules that execute each or several steps in the above flow chart, for example, may include a mode control unit 3002, a first panoramic image generation unit 3004, an angular velocity curve generation unit 3006, and a detector effective data position generation unit 3008 , some or all of the second panoramic image generation unit 3010 , the three-dimensional reconstruction unit 3012 , the anteroposterior and lateral image generation unit 3014 , the CT image generation unit 3016 , and the angle calculation unit 3018 . Therefore, each step or several steps in the above flowcharts may be performed by corresponding modules, and the apparatus may include one or more of these modules.
  • a module may be one or more hardware modules specifically configured to perform the corresponding steps, or be implemented by a processor configured to perform the corresponding steps, or be stored in a computer-readable medium for implementation by the processor, or be implemented by a some combination to achieve.
  • the hardware structure can be implemented using a bus architecture.
  • the bus architecture can include any number of interconnecting buses and bridges, depending on the specific application of the hardware and the overall design constraints.
  • the bus 3100 connects together various circuits including one or more processors 3200, memory 3300 and/or hardware modules.
  • the bus 3100 may also connect various other circuits 1400 such as peripherals, voltage regulators, power management circuits, external antennas, and the like.
  • the bus 3100 may be an Industry Standard Architecture (ISA, Industry Standard Architecture) bus, a Peripheral Component Interconnect (PCI, Peripheral Component) bus, or an Extended Industry Standard Architecture (EISA, Extended Industry Standard Component) bus, etc.
  • ISA Industry Standard Architecture
  • PCI Peripheral Component Interconnect
  • EISA Extended Industry Standard Component
  • the bus can be divided into address bus, data bus, control bus and so on. For ease of representation, only one connection line is used in this figure, but it does not mean that there is only one bus or one type of bus.
  • any process or method descriptions in flowcharts or otherwise described herein may be understood to represent modules, segments or portions of code comprising one or more executable instructions for implementing specific logical functions or steps of the process , and that the scope of preferred embodiments of the present disclosure includes alternative implementations in which functions may be performed out of the order shown or discussed, including substantially concurrent or in reverse order as the functions involved are involved.
  • the processor executes the various methods and processes described above.
  • method embodiments in the present disclosure may be implemented as a software program tangibly embodied on a machine-readable medium, such as memory.
  • part or all of the software program may be loaded and/or installed via memory and/or a communication interface.
  • One or more steps in the methods described above may be performed when a software program is loaded into memory and executed by a processor.
  • the processor may be configured to perform one of the above-mentioned methods in any other suitable manner (for example, by means of firmware).
  • a "readable storage medium” may be any device that can contain, store, communicate, spread or transmit programs for instruction execution systems, devices or devices or use in conjunction with these instruction execution systems, devices or devices. More specific examples (non-exhaustive list) of readable storage media include the following: electrical connection with one or more wires (electronic device), portable computer disk case (magnetic device), random access memory (RAM), Read Only Memory (ROM), Erasable and Editable Read Only Memory (EPROM or Flash Memory), Fiber Optic Devices, and Portable Read Only Memory (CDROM).
  • the readable storage medium may even be paper or other suitable medium on which the program can be printed, since the program can be scanned, for example, by optical scanning of the paper or other medium, followed by editing, interpretation or other suitable means if necessary. processing to obtain programs electronically and store them in memory.
  • various parts of the present disclosure may be realized by hardware, software or a combination thereof.
  • various steps or methods may be implemented by software stored in memory and executed by a suitable instruction execution system.
  • a suitable instruction execution system For example, if implemented in hardware, as in another embodiment, it can be implemented by any one or combination of the following techniques known in the art: Discrete logic circuits, ASICs with suitable combinational logic gates, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.
  • each functional unit in each embodiment of the present disclosure may be integrated into one processing module, each unit may exist separately physically, or two or more units may be integrated into one module.
  • the above-mentioned integrated modules can be implemented in the form of hardware or in the form of software function modules. If the integrated modules are realized in the form of software function modules and sold or used as independent products, they can also be stored in a readable storage medium.
  • the storage medium may be a read-only memory, a magnetic disk or an optical disk, and the like.

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Abstract

一种口腔锥形束X射线成像系统(10)及其快速定位方法，成像系统(10)的工作模式包括口腔CT拍摄模式、口腔全景拍摄模式和头颅正侧位拍摄模式，成像系统(10)包括射源(100)、平板探测器(200)、旋转驱动装置、数据处理装置(300)及控制装置(400)。射源(100)、平板探测器(200)和旋转驱动装置的数量为一个，以便形成单路成像系统。工作模式还包括快速定位模式，以便根据快速定位模式的定位结果来进行成像系统(10)的自适应摆位。快速定位方法中，发射低剂量的X射线；接收及重建CT图像，获取被测对象的当前位姿；及基于当前位姿，成像系统(10)进行自适应摆位，以便进行口腔全景拍摄模式或头颅正侧位拍摄模式的成像拍摄。

Description

口腔锥形束X射线成像系统及其快速定位方法 技术领域
本公开涉及口腔锥形束X射线成像系统及其快速定位方法。
背景技术
常规口腔X射线成像包括四种方式，分别是：口腔CT拍摄、口腔全景拍摄、头颅正侧位拍摄和牙片拍摄。其中将口腔CT拍摄、口腔全景拍摄和头颅正侧位拍摄三种功能集中到一个系统上是目前口腔X射线成像系统的主流方案，通常称之为口腔三合一系统。
口腔CT拍摄通常采用360°的圆轨迹旋转扫描，然后进行三维断层重建获得口腔CT数据。在360°的旋转扫描过程中，需要进行几百个甚至上千个投影，那么每一个投影的曝光时间很有限，相对应的就是每个投影对应的X射线辐射剂量就有限，因此通常采用较短的射源到探测器的距离来提高探测器接受到的辐射剂量，射源到探测器的距离一般采用500～1000mm。
与口腔CT拍摄的360°圆轨迹旋转扫描对应的，口腔全景拍摄则采用射源到探测器的相对位置固定的方式，采用三段弧形拼接的运动轨迹，运动过程中弧形的旋转中心按一定规则移动。相应的口腔全景也是在运动过程中进行几百个甚至上千个投影，然后通过层析原理进行重建，因此其同样面对和口腔CT一样的因为辐射剂量的原因而限制射源到探测器的距离，其常规的射源到探测器的距离也为500～1000mm。
头颅正侧位拍摄仅为二维直接成像，其剂量的限制就远低于口腔CT拍摄和口腔全景拍摄，同时头颅正侧位拍摄为了保障每个位置成像的畸变足够小，因此头颅正侧位拍摄需要射源到探测器的距离足够大，通常在1700mm以上。
鉴于以上原因，目前主流的三合一技术采用两套光路来同时实现口腔CT拍摄、口腔全景拍摄和头颅正侧位拍摄。一套光路的射源到探测器的距离为500～1000mm，用以实现口腔CT拍摄和口腔全景拍摄。口腔CT拍摄采用固定旋转中心的圆轨迹进行拍摄，口腔全景拍摄采用固定射源和探测器的相对位置，通过拍摄过程中移动旋转中心来实现口腔全景拍摄。另外一套光路复用前面一套光路的射源，再组合一个线阵探测器或大尺寸(比如40cm*30cm)的平板探测器，使得射源到探测器的距离在1700mm以上，用以实现头颅正侧位拍摄。
现有的三合一系统采用两套光路来同时实现口腔CT拍摄、口腔全景拍摄、头颅正侧位片拍摄的功能，系统成本及系统复杂性较高。口腔全景的图像质量取决于患者本身的牙弓曲线和预设牙弓曲线的紧密相关程度，虽然可以采用多组预设的牙弓曲线，但是个体牙弓的多样性决定了这种方法依然不能解决根本问题。同时口腔全景拍摄过程中摆位过程也是一个比较繁琐的过程。尽管头颅正侧位拍摄进行二维拍摄，但是其临床需求对拍摄的摆位要求很高，对患者的位姿有严格要求。以常用的侧位片为例，需要X射源、左耳孔、右耳孔在一条直线上，同时头颅不能有倾斜。通常头颅正侧位摆位过程都需要几分钟甚至十分钟以上时间，严重影响拍摄效率和患者体验。
发明内容
本公开提供了一种口腔锥形束X射线成像系统，所述系统的工作模式包括口腔CT拍摄模式、口腔全景拍摄模式和头颅正侧位拍摄模式，所述系统包括：射源，配置为向被测对象发射锥形束X射线；平板探测器，配置为对经过所述被测对象的X射线进行探测；旋转驱动装置，配置为转动所述射源和平板探测器、或者使得所述被测对象进行转动；数据处理装置，配置为接收工作模式指令以选择与所述口腔CT拍摄模式、口腔全景拍摄模式和头颅正侧位拍摄模式中的一种模式对应的 工作模式控制参数组；以及控制装置，配置为接收所选择的成像模数控制参数组，对所述旋转驱动装置进行控制，和/或对所述射源及平板探测器进行控制，以进行成像拍摄，其中，所述射源、平板探测器和旋转驱动装置的数量为一个，以便形成单路成像系统。
本公开还提供了一种基于口腔锥形束X射线成像系统的快速定位方法，包括：启动所述快速定位模式，发射低剂量的X射线；接收及重建CT图像，获取被测对象的当前位姿；以及基于所述当前位姿，所述成像系统进行自适应摆位，以便进行所述口腔全景拍摄模式或所述头颅正侧位拍摄模式的成像拍摄。
附图说明
附图示出了本公开的示例性实施方式，并与其说明一起用于解释本公开的原理，其中包括了这些附图以提供对本公开的进一步理解，并且附图包括在本说明书中并构成本说明书的一部分。
图1是本公开实施方式的锥形束X射线成像系统的示意图。
图2是本公开实施方式的锥形束X射线成像系统的示意图。
图3是本公开实施方式的口腔CT拍摄模式工作示意图。
图4是本公开实施方式的头颅正侧位拍摄模式工作示意图。
图5是本公开实施方式的数据处理装置的示意图。
图6是本公开实施方式的第一口腔全景拍摄模式工作示意图。
图7是本公开实施方式的数据处理装置的示意图。
图8是本公开实施方式的数据处理装置的示意图。
图9是本公开实施方式的第二口腔全景拍摄模式工作示意图。
图10是本公开实施方式的虚拟旋转轴参数确定的示意图。
图11是本公开实施方式的全景图像生成方法的流程图。
图12是本公开实施方式的目标牙弓曲面的示例图。
图13是本公开实施方式的快速定位方法的流程图.
图14是本公开实施方式的射源调整示意图。
图15是本公开实施方式的调整滚转角后状态示意图。
图16是本公开实施方式的调整偏航角后状态示意图。
图17是本公开实施方式的数据处理装置的结构示意框图。
具体实施方式
下面结合附图和实施方式对本公开作进一步的详细说明。可以理解的是，此处所描述的具体实施方式仅用于解释相关内容，而非对本公开的限定。另外还需要说明的是，为了便于描述，附图中仅示出了与本公开相关的部分。
需要说明的是，在不冲突的情况下，本公开中的实施方式及实施方式中的特征可以相互组合。下面将参考附图并结合实施方式来详细说明本公开的技术方案。
除非另有说明，否则示出的示例性实施方式/实施例将被理解为提供可以在实践中实施本公开的技术构思的一些方式的各种细节的示例性特征。因此，除非另有说明，否则在不脱离本公开的技术构思的情况下，各种实施方式/实施例的特征可以另外地组合、分离、互换和/或重新布置。
图1是本公开的一个实施方式的锥形束X射线成像系统的结构示意框图。根据本公开的锥形束X射线成像系统10可以工作在口腔CT拍摄模式、口腔全景拍摄模式、以及头颅正侧位拍摄模式。在口腔CT拍摄模式下，可以按照圆轨迹运动来拍摄图像后进行三维重建来进行成像。口腔全景拍摄模式可以包括第一口腔全景拍摄模式或第二口腔全景拍摄模式。在第一口腔全景拍摄模式中，可以基于圆轨迹进行变速转动拍摄，通过重排处理来实现多旋转中心的口腔全景拍摄。在第二口腔全景拍摄模式中，可以基于圆轨迹进行匀速转动拍摄，通过插值处理来实现口腔全景拍摄。在头颅 正侧位拍摄模式下，可以基于圆轨迹运动，得到正位片和侧位片。另外成像系统10还可以包括快速定位模式。该快速定位模式用于成像系统的自适应摆位。例如，在选择口腔全景拍摄模式或头颅正侧位拍摄模式的情况下，首先启动快速定位模式，在该快速定位模式中，采用口腔CT拍摄模式的拍摄轨迹，X射线的辐射剂量低于口腔CT拍摄模式的X射线的辐射剂量，以便根据快速定位模式的定位结果来进行成像系统的自适应摆位。
参考图1，本公开的成像系统10可以包括射源100、X射线探测器200、数据处理装置300、控制装置400和旋转驱动装置。射源100能够向被测对象发射X射线锥形束。探测器200对经过被测对象的X射线进行探测。探测器200可以为平板探测器，优选为矩形平板探测器、小平板探测器。X射线拍摄的位置可以是人体的头部、颌部、口腔部等。旋转驱动装置可以包括第一旋转驱动装置500或第二旋转驱动装置600。在旋转驱动装置包括第一旋转驱动装置500的情况下，可以同步驱动射源100及探测器200一起绕被测对象(患者)进行圆轨迹运动，被测对象固定不动。在旋转驱动装置包括第二旋转驱动装置600的情况下，可以控制被测对象转动，射源和探测器固定不动。第二旋转驱动装置600驱动旋转装置700，使得位于旋转装置700之上的被测对象进行运动，以便使得射源100及探测器200沿着圆轨迹进行成像拍摄。控制装置400可以用于控制第一旋转驱动装置/第二旋转驱动装置、以及用于控制射源和探测器的拍摄。在本公开中，优选地旋转驱动装置仅包括第二旋转驱动装置600，即控制被测对象的转动来进行成像拍摄。
射源100、探测器200和旋转驱动装置的数量均为一个，这样可以构成单路成像系统。本公开采用图2所述的落地式结构，并且包括第二旋转驱动装置使得被测对象进行旋转，例如第二旋转驱动装置可以驱动座椅形式的旋转装置使得坐在座椅上的被测对象进行转动，而射源100和探测器200不进行转动。如图2所示，射源100与探测器200之间的距离SID可以为1.5m～2.5m。射源100与旋转轴之间的距离表示为SAD，其中SID与SAD的差值为0.2m～0.4m。优选地，SID为1.7m，SID与SAD的差值为0.25m。
根据本公开的实施方式，X射线成像系统可以工作在口腔CT拍摄模式、口腔全景拍摄模式、以及头颅正侧位拍摄模式，需要在口腔全景拍摄模式及头颅正侧位拍摄模式拍摄时，可以首先进行快速定位模式。图3示出了口腔CT拍摄模式工作的示意图。其中在口腔CT拍摄模式下被测对象可以进行匀速转动。在图3中以虚线圆框示出了射源的相对转动路径。从图3可以看出，由于被测对象进行转动，因此射源可以设置相对于被测对象在圆周进行圆轨迹运动。图4示出了头颅正侧位拍摄模式工作的示意图。如图4所示，可以在0°的正位位置拍摄正位片，而在90°的侧位位置拍摄侧位片，其中0°为与头颅的冠状面垂直的角度，90°为从0°顺时针或逆时针旋转90°。
对于口腔全景拍摄模式，可以采用第一口腔全景拍摄模式也可以采用第二口腔全景拍摄模式。图5中示出了第一口腔全景拍摄模式的数据处理装置的示意图。如图5所示，数据处理装置300可以包括模式控制部3002、指令接收部3020、和第一全景图像生成部3004。指令接收部3020接收来自外部的工作模式。模式控制部3002基于接收的工作模式指令调取相应的工作模式控制参数组。控制装置400基于模式控制部3002调取的工作模式控制参数组控制被测对象与射源100和探测器200进行相对转动过程，以及控制射源100和探测器200进行拍摄。需要说明的是，在进行口腔CT拍摄模式和头颅正侧位拍摄模式拍摄时，指令接收部3020接收外部指令并且模式控制部3002控制进行口腔CT拍摄模式拍摄或头颅正侧位拍摄模式拍摄。
在图5所示的数据处理装置中，可以通过第一口腔全景拍摄模式来实现全景图像的拍摄。在该第一口腔全景拍摄模式中，被测对象被控制为进行变速转动，如图6 所示。工作模式控制参数组至少包括第一口腔全景拍摄模式控制参数组。第一全景图像生成部3004对基于第一口腔全景拍摄模式控制参数组控制的相对转动过程(射源100和探测器200与被测对象之间的相对转动过程)中探测器200采集的第一序列二维投影数据(即包括一系列的二维投影图像)进行重排处理以生成口腔部位的第一全景图像，基于第一口腔全景拍摄模式控制参数组控制的相对转动过程为变速的转动过程。
重排处理可以包括：至少基于口腔部位的各个成像点的位置信息对第一序列二维投影数据进行排列。具体地，基于口腔部位的每个成像点的位置信息获取每个成像点对应的射源位置，基于每个成像点对应的射源位置获取每个成像点在探测器上的投影位置，以及选取各个成像点在探测器上的投影位置的二维投影数据(即列数据，即对每个成像点选取投影位置的一列投影数据，列数据的宽度取决于各个成像点之间的间隔，优选地，各个成像点之间的间隔相同)进行排列，获得第一全景图像。
变速转动过程的角速度曲线基于口腔部位特征数据(优选为口腔部位形状特征数据，例如牙弓曲线)生成，使得各个成像点对应的各个射源位置中相邻的射源位置之间的转动时间相等。
图7示出了数据处理装置300的示意图。数据处理装置300还可以包括角速度曲线生成部3006及探测器有效数据位置生成部3008。角速度曲线生成部3006基于选定的口腔部位特征数据(例如选定的牙弓曲线)生成角速度曲线。探测器有效数据位置生成部3008基于选定的口腔部位特征数据(例如选定的牙弓曲线)生成探测器有效数据位置。
数据处理装置300还可以包括存储器。存储器可以存储预先生成的多种牙弓曲线数据(即口腔部位特征数据)。角速度曲线生成部3006和探测器有效数据位置生成部3008分别基于口腔部位特征选定指令选定的牙弓曲线数据生成角速度曲线和探测器有效数据位置。作为一个示例，第一口腔全景拍摄模式控制参数组至少基于角速度曲线以及探测器有效数据位置生成。在变速的转动过程中，探测器200以预设的采集速率进行数据采集，以获得第一序列二维投影数据。
上述各个实施方式的锥形束X射线成像系统中，变速的转动过程可以至少包括一个圆周的转动过程。第一全景图像生成部3004对基于第一口腔全景拍摄模式控制参数组控制的相对转动过程(射源100和探测器200与被测对象之间的相对转动过程)中探测器200采集的第一序列二维投影数据(即包括一系列的二维投影图像)进行重排处理以生成两个以上旋转中心的第一全景图像。另外可以通过对一系列二维投影图像进行重排处理，获取两个以上旋转中心的第一全景图像。
可以根据患者的脸型等选择合适的牙弓曲线数据，X射线成像系统根据牙弓曲线数据生成拍摄过程的角速度曲线和探测器有效数据位置以进行拍摄。拍摄时根据生成的角速度绕着患者的头部(口腔部位)做圆周运动。射源100发出X射线锥形束，探测器200按一定采集速率采集X射线投影图。由于X射线为锥形束，探测器为平板探测器，投影线与射源和探测器的中心连线形成一定夹角，通过二维投影数据的重排处理能够实现多旋转中心的口腔全景拍摄效果。
根据本公开的一个实施方式，可以采用第二口腔全景拍摄模式作为全景图像模式。例如在图5的实施例中，可以采用第二全景图像生成部替代第一全景图像生成部。也可以在包括第一全景图像生成部的基础上还包括第二全景图像生成部。在包括第二全景图像生成部的情况下，工作模式控制参数组可以至少包括第二口腔全景拍摄模式控制参数组。第二全景图像生成部3010对基于第二口腔全景拍摄模式控制参数组控制的相对转动过程(射源100和探测器200与被测对象之间的相对转动过程)中探测器200采集的第二序列二维投影数据(即包括一系列的二维投影图像)进行插值处理以生成口腔部位的第二全景图像。例如图9所示，基于第二口腔全景拍摄模式控制参数 组控制的相对转动过程为匀速的转动过程。优选地，匀速的转动过程至少包括一个圆周的转动过程。
作为一个示例，插值处理可以包括：判断探测器在采集投影数据过程中的各个射源位置是否是基于口腔部位的各个成像点的位置信息计算得到的射源目标位置；以及如果某个射源位置不是射源目标位置，则对该射源位置采集的投影数据进行基于位置偏移的加权处理，位置偏移为该射源位置和旋转中心的连线与口腔部位的交点与相邻的成像点之间的位置偏移，将加权处理后的投影数据叠加至相邻的成像点对应的投影数据(对所有投影数据处理完毕之后，进行归一化处理)。
作为另一示例，插值处理可以包括：基于口腔部位的各个成像点的位置信息计算得到射源目标位置；以及，在实际的投影数据采集过程中，如果某个射源目标位置未进行投影数据采集，则基于与该射源目标位置相邻的且对应成像点的射源位置采集的投影数据获得该射源目标位置的投影数据。获得该射源目标位置的投影数据的步骤可以包括：对两个以上相邻的且对应成像点的射源位置采集的投影数据进行线性插值，以获得该射源目标位置的投影数据。
如上所述，对于口腔全景拍摄模式可以采用变速的第一口腔全景拍摄模式或者可以采用匀速的第二口腔全景拍摄模式。
在变速的第一口腔全景拍摄模式，可以根据牙弓曲线的情况来生成拍摄过程的角速度曲线，并且按照该角度速度来使得被测对象进行圆周运动或者部分圆周运动。在匀速的第二口腔全景拍摄模式中，可以按照恒定速度使得被测对象进行圆周运动或者部分圆周运动。在运动的同时，射源可以发射X射线，探测器可以按照一定速率来采集数据，最终重建来实现全景拍摄。
第一口腔全景拍摄模式或第二口腔全景拍摄模式中，首先确定被测对象的牙弓曲线，以及确定虚拟旋转轴。虚拟旋转轴参数确定为减少牙弓曲线一侧的成像点的成像结果受到对侧骨质结构的影响，此外还可以确定为保证成像射线在拍摄中变化连续无突变。上面所述的对侧骨质结构可以包括对侧的牙齿，牙齿周围的骨头及颈椎等。
在确定牙弓曲线的过程中，可以根据被测对象的脸型来选择合适的已有牙弓曲线，也可以通过对被测对象进行测量来生成合适的牙弓曲线。
虚拟旋转轴参数可以为虚拟旋转轴心的位置。本领域的技术人员根据图10可以理解，虚拟旋转轴的数量可以为多个，例如可以为三个或者以上。可以采用圆弧圆心作为虚拟旋转轴参数为例进行说明。在图10示出了根据本公开的一个实施例的确定虚拟旋转轴参数的圆心及半径的示意图。在图10中示出了三段圆弧的情况，但是在本公开中并不限于三段圆弧，可以根据情况来进行设定，例如可以为四段、五段等。
首先，选择两颗参考牙齿，分别为第一牙齿和第二牙齿，该两颗参考牙齿可以为对称的牙齿，另外也可以选择上颚牙齿也可以选择下颚牙齿。在图10中示出了所选的参考牙齿为两颗下犬牙。并且可以通过激光定位等方式来确定第一牙齿的位置C1和第二牙齿的位置C2。基于第一牙齿和第二牙齿将牙弓曲线分为三段圆弧，分别为第一圆弧A1、第二圆弧A2和第三圆弧A3。基于被测对象的脸型指定牙弓开合控制角度θ，其中牙弓开合控制角度θ可以为第一牙齿的位置C1和第二牙齿的位置C2之间的连线与位置C1或C2与第二圆弧A2的圆心之间的连线之间的角度，同时基于被测对象的脸型来确定牙弓长度控制系数r。从而得到第一圆弧A1的圆心O1、第二圆弧A2的圆心O2和第三圆弧A3的圆心O3。其中，第一圆弧A1的圆心O1与第一牙齿的位置C1之间的直线距离等于第三圆弧A3的圆心O3与第二牙齿的位置C2之间的直线距离，第一圆弧A1的圆心O1与第一牙齿的位置C1之间的直线距离等于第一牙齿的位置C1和第二牙齿的位置C2之间的距离乘以牙弓长度控制系数r，也就是： |O1C1|＝|O3C2|＝r|C1C2|。同时可以获得第一圆弧A1的半径r1、第二圆弧A2的半径r2和第三圆弧A3的半径r3。
计算牙弓曲线的每个成像点所对应的射源对应位置与探测器有效位置。其中探测器有效位置可以是当对某个成像点进行成像时，射源位于射源对应位置发射X射线，探测器有效位置处的探测器可以接收到X射线，并且对该成像点进行成像，通过该有效位置还可以避免其他成像点对该某个成像点的成像造成干扰(例如避免其他成像点也在该有效位置成像(或造成成像重合))。该有效位置设置成仅能对该某个成像点成像，而其他成像点则在该位置不能成像。
在计算过程中，延长牙弓曲线的成像点与该成像点所在圆弧的圆心之间的连线，延长线与射源的运动轨迹的交点为该成像点所对应的射源对应位置，并且相应地将会得到射源对应位置所对应的探测器有效位置。为了得到整个口腔牙齿的照片，可以绕着固定旋转中心OS旋转射源，并且射源在旋转的过程中发射X射线。然后根据所计算的射源对应位置和探测器有效位置的关系，得到每个成像点的X射线投影数据。其中探测器有效位置测得的一个成像点的X射线投影数据可以为一列数据，也可以为两列以上数据。其中一列数据的情况下，就是延长牙弓曲线的成像点与该成像点所在圆弧的圆心之间的连线与探测器的交点处所测得的一列数据，也可以为该一列数据附近的一列以上的数据。
对于图10中标出的成像点C1，因为其处于第一圆弧A1，因此延长成像点C1与圆心O1之间的连接线。该连接线与射源运动轨迹(虚线圆)的交点则确定为射源对应位置。该连接线与探测器的交点位置则确定为探测器有效位置。通过相同的原理，可以得到所有成像点的射源对应位置和探测器有效位置。此外每个成像点中的至少一部分成像点与射源的连接线、和射源与固定旋转中心的连接线成预定夹角。并且对于不同的成像点，预定夹角是不同的。另外对于一部分成像点，这些成像点与射源的连接线、和射源与固定旋转中心的连接线也可以是重合。
绕固定旋转中心OS旋转被测对象，分别获取每个成像点所对应的射源对应位置处所发射的X射线在每个成像点所对应的探测器有效位置的X射线投影数据。在探测器有效位置获得一列或两列以上的投影列数据来作为对应成像点的X射线投影数据。在获得每个成像点的投影列数据之后，将所获得的投影列数据进行重建来得到口腔全景图像。例如对于第一口腔全景拍摄模式进行重拍处理，对于第二口腔全景拍摄模式进行上述的插值处理。
根据本公开的另一实施例，还提供了一种全景图像生成方法。图11示出了全景图像生成方法的流程图。如图11所示，全景图像生成方法可以包括以下步骤S102～步骤S116。
在步骤S102中，获取被测对象的头部的三维图像。被测对象的头部的三维图像可以通过锥形束X射线成像系统采集的被测对象的头部的全方位二维投影图像来重建得到。锥形束X射线成像系统通过对被测对象的头部执行完整扫描采集被测对象的头部的全方位二维投影图像。锥形束X射线成像系统利用自身的重建几何参数对被测对象头部的全方位二维投影图像进行三维重建从而获得被测对象头部的三维图像。其中，完整扫描可以是被测对象头部的180度扫描，也可以是被测对象头部的360度扫描。通常在锥形束X射线成像系统的探测器偏置时需要执行360度扫描才可获得全方位的二维投影图像。
在步骤S104中，确定第一横断面图像，第一横断面图像为三维图像中的牙弓层。第一横断面图像可以是三维图像中包含完整牙弓的任意一张断面图像。第一横断面图像可以是三维图像中包含完整下牙弓的一张断面图像。第一横断面图像也可以是三维图像中牙弓最清晰或牙弓最明显的一张断面图像。第一横断面图像还可以是三维图像中牙弓最密集的一张断面图像。作为一个示例，可以以三维图像中Z轴坐 标对应预先牙弓位置的横断面图像作为第一横断面图像。例如，预定牙弓位置可以为上牙槽骨位置、下牙槽骨位置。例如具体应用中，牙弓位置可以取经验值，通过预先配置的方式进行设定。
在步骤S104中，可以利用预训练的神经网络对三维图像进行处理以确定第一横断面图像。例如，可以将三维图像中的部分横断面图像或者全部的横断面图像输入预训练的神经网络中，神经网络输出各横断面图像的置信度，该置信度表示横断面图像为第一横断面图像的概率，选择置信度最高的一张横断面图像作为第一横断面图像，或者选择置信度大于预定阈值的多张横断面图像的中间层作为第一横断面。
用于确定第一横断面图像的神经网络可以利用标记为牙弓最密集的横断面图像和该横断面图像所属三维图像的所有横断面图像作为样本来训练得到。神经网络可以是但不限于卷积神经网络、前馈神经网络或其他，对于神经网络的架构及其类型，本公开实施例不作限制。
另外在步骤S104中，还可响应于用户操作选定三维图像中牙弓最清晰的一层作为第一横断面图像。即人工选出三维图像中牙弓最清晰的一张断面图像作为第一横断面图像。
在步骤S106中，对第一横断面图像进行处理以获得包含被测对象的牙齿的骨阈值分割图像。具体地，对第一横断面图像执行骨阈值分割和高斯平滑处理，以获得包含被测对象的牙齿的骨阈值分割图像。通过对第一横断面图像执行骨阈值分割，可以将第一横断面图像中的软组织和水等物质去除，获得仅包含骨骼和牙齿的骨阈值分割图像，对骨阈值分割图像执行高斯平滑处理，可以将骨阈值分割图像中的噪声去除，从而获得准确性更高、质量更好的骨阈值分割图像。这样可以提高骨阈值分割图像的质量，进而提高牙弓曲线的准确性。
在步骤S108中，确定骨阈值分割图像中各个像素点在预定极坐标系中的极坐标。具体地，可以通过直角坐标系到极坐标系的转换关系将骨阈值分割图像中的每个像素点映射到预定极坐标系中，从而获得骨阈值分割图像中每个像素点的位置的极坐标表示。例如，预定极坐标系可以是但不限于以骨阈值分割图像的重心为极点的极坐标系。
在步骤S110中，根据骨阈值分割图像中以预定角度为极角且像素值非零的像素点的极径，确定每个预定角度对应的目标极径。预定角度包括0度～360度之间间隔预定值的多个角度。具体应用中，可以根据需要选择合适的预定角度。步骤S110可以包括以下内容。步骤a1，确定骨阈值分割图像中以第一预定角度为极角的像素值非零的像素点中极径最小的第一像素点和极径最大的第二像素点。在第一预定角度的极轴上以极坐标系的极点为起点向外辐射，第一个像素值非零的像素点即为第一像素点，最后一个像素值非零的像素点即为第二像素点。由于骨阈值分割图像中除骨骼和牙齿之外的其他部分的像素值均默认为零，属于牙齿的像素点的像素值非零，因此，通过此方式，可以查找到牙齿的最前端像素点和最后端像素点(即，第一像素点和第二像素点)，从而准确定位牙齿区域。其中，第一预定角度是指任意一个预定角度。步骤a2，以第一像素点和第二像素点的极径平均值作为第一预定角度的目标极径。以第一像素点和第二像素点的极径平均值作为目标极径，可以将采样点精准定位在牙齿中间区域，由于牙齿中间区域的牙弓最为明显和完整，因此，这样确定采样点，可以进一步提高牙弓曲线的准确性。
在步骤S112中，以每个预定角度及其目标极径为数值对形成数值对序列，数值对序列为牙弓曲线的采样点数据。其中，采样点为预定极坐标系中以预定角度为极角、以预定角度的目标极径为极径的点。
一些实施方式中，数值对序列中的各个数值对可以按照相应预定角度从小到排列。例如，若预先选定的预定角度为36个，数值对序列则包含36个数值对，每个数值对包括预定角度的角度值及其对应目标极径。
在步骤S114中，利用采样点数据拟合得到被测对象的牙弓曲线。一些实施方式中，可以利用采样点数据采用多项式拟合方式拟合得到牙弓曲线。例如，可以使用5次多项式、6次多项式、8次多项式来实现牙弓曲线的拟合。
以5次多项式为例，可以根据下式(1)拟合牙弓曲线：
r＝a 0+a 1θ+a 2θ 2+a 3θ 3+a 4θ 4+a 5θ 5       (1)
其中，r表示预定角度对应的目标极径，θ表示预定角度，a 0，a 1，a 2，a 3，a 4，a 5均为系数。
具体地，可以将数值对序列中的5个数值对代入式(1)形成方程组，通过最小二乘法求解该方程组得到式(1)中系数a 0，a 1，a 2，a 3，a 4，a 5的取值，以预定角度为变量θ代入式(1)重新确定各个预定角度对应的目标极径，并将重新确定的目标极径更新到数值对序列中，最后利用更新后的数值对序列获得牙弓曲线。
通过将骨阈值分割图像映射到极坐标系，采用多项式拟合方式进行拟合，可以获得准确性更高的牙弓曲线。
在步骤S116中，利用牙弓曲线获得被测对象的口腔全景图像。具体而言，步骤S116可以包括如下步骤b1～步骤b4。步骤b1，以牙弓曲线上每个点，计算拍摄中经过该点的X射线，并获取X射线在探测器上的投影数据。其中，射源-被测对象上的对应点-探测器上投影点，三点连成一条直线。步骤b2，将经过该点的X射线的投影数据按权重累加，得到该点的成像值，按照这样的方式，一条牙弓曲线可得一行数据。步骤b3，将牙弓曲线在垂直方向上下移动，得到多行数据，按顺序排列所有行，得到完整的口腔全景图像。
一些实施方式中，步骤S116可以包括如下步骤c1～步骤c2。步骤c1，以牙弓曲线为母线、以三维图像的Z轴为准线确定目标牙弓曲面。其中，Z轴垂直于第一横断面图像。图12示出了目标牙弓曲面的示例图。步骤c2，展开牙弓曲面展开以获得被测对象的口腔全景图像。
此外，步骤S116中还可以采用其他各种可适用的方式通过牙弓曲线来获得口腔全景图像。对于步骤S116的具体实现方式，本公开实施例不作限制。
图11的实施例通过更准确的牙弓曲线结合上述实施方式来获得口腔全景图像，不仅可以在不增加机械结构的情况下实现真正的口腔全景图像拍摄，而且能够进一步提高口腔全景图像的准确性，使得口腔全景图像的准确性更接近口腔全景机的拍摄效果，口腔全景图像的图像质量高于口腔全景机的全景图像质量，同时还支持横断面的灵活选择，方便用户根据需要调整口腔全景图像的形状和曲面断层位置。通过图11的实施例，可以一次扫描得到CT图像和口腔全景图像。并且横断面图像可灵活选择，便于用户灵活设置曲面形状和曲面断层位置、精准指定曲面形状和曲面断层位置、多次实时重建口腔全景图像，不仅可以有效避免因预先设置的扫描轨迹无法适配于被测对象实际牙弓而导致口腔全景图像不可用等问题，而且可以带来更多临床使用价值。
本公开的成像系统能够实现基于圆轨迹的口腔三合一拍摄，能够实现在圆轨迹X射线成像系统上拍摄CBCT，口腔全景图像和正侧位片，并且能够实现模拟多旋转中心的口腔全景拍摄，实现牙周面更好的拟合。本公开的锥形束X射线成像系统可以在不增加机械结构的情况下实现真正的口腔全景图像拍摄，而不是重建后的数据合成全景图像，因此拍摄速度更快，同时对拍摄时的几何控制要求更低。
本公开的成像系统只有一个旋转中心，运动机构少、结构简单，只需要一个探测器和一个射源，拍摄模式可以是保持射源和探测器不动，被测对象旋转，减少机器控 制效能，减少被测对象头部移动的偏移量，可以减少重建结果的重影概率，提高精度和阅片效果，更好地辅助医生对患者信息的判断。
本领域的技术人员应当理解，根据本公开的成像系统可以实现口腔CT拍摄模式拍摄、口腔全景拍摄模式拍摄以及头颅正侧位拍摄模式拍摄。在选择了CT模式拍摄的情况下，成像系统可以直接对被测对象进行拍摄。在选择了口腔全景拍摄模式拍摄的情况下，成像系统需要首先启动快速定位模式来进行拍摄，根据快速定位模式的定位结果来进行成像系统的自适应摆位，然后进行口腔全景拍摄模式拍摄。在进行成像系统的自适应摆位的过程中，需要确定被测对象的牙弓曲线，然后基于所确定的牙弓曲线如上面描述的方式进行自适应摆位，然后基于圆轨迹技术来完成口腔全景拍摄模式拍摄。
在选择了头颅正侧位拍摄模式拍摄的情况下，成像系统需要首先启动快速定位模式来进行拍摄，根据快速定位模式的定位结果来进行成像系统的自适应摆位，然后进行头颅正侧位拍摄模式拍摄。如图1所示，成像系统可以包括摆位控制装置110。控制装置400可以控制该摆位控制装置110，以便调节射源的高度以及控制旋转装置转动，从而实现成像系统的自适应摆位。
快速定位模式采用低剂量X射线以及快速扫描的方式来实现快速定位，从而辅助摆位的确认。快速定位模式可以采用口腔CT拍摄模式相同的运动轨迹。与口腔CT拍摄模式的不同之处在于：X射线剂量低、旋转速度快、投影数量少以及重建像素大。通过快速定位模式可以得到被测对象的轮廓，重建出被测对象的头颅轮廓及牙弓轮廓，在图像空间分辨率和对比度分辨率方面并没有太高的要求。重建像素要求不高，辐射剂量要求不高，对混叠伪影的要求不高。因此可以采用更低的辐射剂量、更少的拍摄张数、更快的旋转过程、更大像素来进行重建。例如口腔CT拍摄模式如果采用600个投影图像，单张投影图像采用8ms的曝光时间，30s的旋转周期，0.25mm的重建像素，那么快速定位模式可以采用200个投影图像，2ms的曝光时间，5s的旋转周期，0.5mm的重建像素。
根据本公开的进一步的实施方式，提供了基于上述成像系统的快速定位方法。图13示出了根据该快速定位方法的流程图。
在步骤S202中，启动快速定位模式，在该快速定位模式中，进行快速低剂量的拍摄。在步骤S204中，可以通过数据处理装置对CT图像进行重建，以便获取被测对象的当前位姿。在步骤S206中，X射线成像系统自适应摆位，例如调节射源的高度以及控制旋转装置转动。在步骤S208中，启动口腔全景拍摄模式进行全景拍摄或者启动头颅正侧位拍摄模式进行头颅正侧位拍摄，从而得到全景图像或者头颅正侧位图像。
此外，在步骤S202之前，还可以包括选择拍摄模式的步骤，例如如果用户选择了口腔全景拍摄模式或者头颅正侧位拍摄模式，则执行步骤S202。但是如果选择了口腔CT模式，则直接进行口腔CT模式的拍摄。
在根据口腔全景拍摄模式启动快速定位模式的情况下，可以在步骤S206中，可以通过重建CT图像来获取被测对象的当前牙弓曲线，从而根据拍摄需要的位置，X射线成像系统自行调节(例如参见图10等的相关内容)，以完成摆位。
在根据头颅正侧位拍摄模式启动快速定位模式的情况下，可以在步骤S206中，可以通过上述的摆位控制装置110进行摆位调整，例如使得射源在竖直方向进行运动来调整射源的高度、以及控制旋转装置转动。在对CT图像进行重建之后得到CT模型，分析数据计算出被测对象相对于标准位姿的三个空间角度(pitch，yaw，roll)。pitch为俯仰角，即沿着X轴旋转的角度。yaw为偏航角，即沿着Y轴旋转的角度。roll为滚转角，即沿着Z轴旋转的角度。将三个角度空间可以反馈至控制装置，并且控制装置控制摆位控制装置来进行自适应摆位。在自适应摆位的过程中，被测对象可 以保持不动(坐在旋转装置上保持不动)，通过摆位控制装置来进行调整。首先可以调整滚转角以进行匹配，然后可以调整偏航角，最后拍摄完成后进行最后图像的旋转来实现俯仰角的调整。调整完成之后再进行头颅正侧位拍摄模式拍摄。
对快速定位模式得到的CT图像进行重建后，得到被测对象的头颅相对于标准位姿的滚转角。基于得到的滚转角，通过旋转驱动装置转动被测对象，使得被测对象的左头颅部分和右头颅部分近似对称，如图15所示。通过被测对象的头颅中心的直线将头颅分为左头颅部分和右头颅部分，被测对象处于正确的位姿时，左头颅部分和右头颅部分将近似对称。在计算滚转角的过程中，将被测对象的头部沿着X轴方向进行投影，左头颅部分和右头颅部分越对称，投影越清晰，投影图像的梯度变化就越大。所以将头颅转动角度α(α∈(-π/2，π/2))，得到的前向投影梯度变化最小的角度α，即为滚转角。
对快速定位模式得到的CT图像进行重建后，得到被测对象的头颅相对于标准位姿的偏航角。基于得到的滚转角，可以通过移动射源的位置来进行自适应摆位。计算偏航角之后，得到射源的目标坐标点，然后通过控制射源移动，从而使得射源、左耳孔、右耳孔三点共线，如图16所示。
以射源、左耳孔和右耳孔共线为条件来计算偏航角。因此在偏航角调整之前，首先调整了滚转角，因此可以认为左耳孔和右耳孔的Y坐标是相同或者近似相同的。此时只需要考虑(X，Z)的坐标值。假设左耳孔坐标为(X 1,Y,Z 1)，右耳孔坐标为(X 2,Y,Z 2)，射源坐标为(X 3,Y 3,Z 3)，为了让射源、左耳孔、右耳孔三点共线，则射源坐标需要为
Figure PCTCN2022133641-appb-000001
射源在Y方向需要移动的距离为Y-Y 3。射源在在Z方向需要移动的距离为
Figure PCTCN2022133641-appb-000002
通过得到在Y方向和Z方向需要移动的距离来对射源进行移动，使得射源、左耳孔、右耳孔共线，来完成自适应摆位。
因为俯仰角对正侧位片的图像质量不产生影响，可以在拍摄完成之后调整图片的角度。例如可以以图像中牙齿平行于水平面为基准，来旋转图片的角度。
上面描述的内容为侧位片拍摄时的位姿确认，在侧位片位姿确认完成之后，正位片的拍摄可以根据侧位片调整后的位姿来进行拍摄即可。
在本公开中，三个空间角度的计算可以通过数据处理装置300的角度计算部来实现。
本公开的数据处理装置300可以通过计算机软件架构的形式实现，也可以通过基于处理系统的硬件架构实现。图17是本公开的一个实施方式的采用处理系统的硬件实现方式的数据处理装置300的结构示意框图。该数据处理装置300可以包括执行上述流程图中各个或几个步骤的相应模块，例如可以包括模式控制部3002、第一全景图像生成部3004、角速度曲线生成部3006、探测器有效数据位置生成部3008、第二全景图像生成部3010、三维重建部3012、正侧位图像生成部3014、CT图像生成部3016、角度计算部3018中的几个或全部。因此，可以由相应模块执行上述流程图中的每个步骤或几个步骤，并且该装置可以包括这些模块中的一个或多个模块。模块可以是专门被配置为执行相应步骤的一个或多个硬件模块、或者由被配置为执行相应步骤的处理器来实现、或者存储在计算机可读介质内用于由处理器来实现、或者通过某种组合来实现。
该硬件结构可以利用总线架构来实现。总线架构可以包括任何数量的互连总线和桥接器，这取决于硬件的特定应用和总体设计约束。总线3100将包括一个或多个处理器3200、存储器3300和/或硬件模块的各种电路连接到一起。总线3100还可以将诸如外围设备、电压调节器、功率管理电路、外部天线等的各种其他电路1400连接。
总线3100可以是工业标准体系结构(ISA，Industry Standard Architecture)总线、外部设备互连(PCI，Peripheral Component)总线或扩展工业标准体系结构(EISA，Extended Industry Standard Component)总线等。总线可以分为地址总线、数据总线、控制总线等。为便于表示，该图中仅用一条连接线表示，但并不表示仅有一根总线或一种类型的总线。
流程图中或在此以其他方式描述的任何过程或方法描述可以被理解为，表示包括一个或更多个用于实现特定逻辑功能或过程的步骤的可执行指令的代码的模块、片段或部分，并且本公开的优选实施方式的范围包括另外的实现，其中可以不按所示出或讨论的顺序，包括根据所涉及的功能按基本同时的方式或按相反的顺序，来执行功能。处理器执行上文所描述的各个方法和处理。例如，本公开中的方法实施方式可以被实现为软件程序，其被有形地包含于机器可读介质，例如存储器。在一些实施方式中，软件程序的部分或者全部可以经由存储器和/或通信接口而被载入和/或安装。当软件程序加载到存储器并由处理器执行时，可以执行上文描述的方法中的一个或多个步骤。备选地，在其他实施方式中，处理器可以通过其他任何适当的方式(例如，借助于固件)而被配置为执行上述方法之一。
在流程图中表示或在此以其他方式描述的逻辑和/或步骤，可以具体实现在任何可读存储介质中，以供指令执行系统、装置或设备(如基于计算机的系统、包括处理器的系统或其他可以从指令执行系统、装置或设备取指令并执行指令的系统)使用，或结合这些指令执行系统、装置或设备而使用。
就本说明书而言，“可读存储介质”可以是任何可以包含、存储、通信、传播或传输程序以供指令执行系统、装置或设备或结合这些指令执行系统、装置或设备而使用的装置。可读存储介质的更具体的示例(非穷尽性列表)包括以下：具有一个或多个布线的电连接部(电子装置)，便携式计算机盘盒(磁装置)，随机存取存储器(RAM)，只读存储器(ROM)，可擦除可编辑只读存储器(EPROM或闪速存储器)，光纤装置，以及便携式只读存储器(CDROM)。另外，可读存储介质甚至可以是可在其上打印程序的纸或其他合适的介质，因为可以例如通过对纸或其他介质进行光学扫描，接着进行编辑、解译或必要时以其他合适方式进行处理来以电子方式获得程序，然后将其存储在存储器中。
应当理解，本公开的各部分可以用硬件、软件或它们的组合来实现。在上述实施方式中，多个步骤或方法可以用存储在存储器中且由合适的指令执行系统执行的软件来实现。例如，如果用硬件来实现，和在另一实施方式中一样，可用本领域公知的下列技术中的任一项或他们的组合来实现：具有用于对数据信号实现逻辑功能的逻辑门电路的离散逻辑电路，具有合适的组合逻辑门电路的专用集成电路，可编程门阵列(PGA)，现场可编程门阵列(FPGA)等。
本技术领域的普通技术人员可以理解实现上述实施方式方法的全部或部分步骤是可以通过程序来指令相关的硬件完成，程序可以存储于一种可读存储介质中，该程序在执行时，包括方法实施方式的步骤之一或其组合。
此外，在本公开各个实施方式中的各功能单元可以集成在一个处理模块中，也可以是各个单元单独物理存在，也可以两个或两个以上单元集成在一个模块中。上述集成的模块既可以采用硬件的形式实现，也可以采用软件功能模块的形式实现。集成的模块如果以软件功能模块的形式实现并作为独立的产品销售或使用时，也可以存储在一个可读存储介质中。存储介质可以是只读存储器，磁盘或光盘等。
本领域的技术人员应当理解，上述实施方式仅仅是为了清楚地说明本公开，而并非是对本公开的范围进行限定。对于所属领域的技术人员而言，在上述公开的基础上还可以做出其它变化或变型，并且这些变化或变型仍处于本公开的范围内。

Claims (20)

  1. 一种口腔锥形束X射线成像系统，其特征在于，所述系统的工作模式包括口腔CT拍摄模式、口腔全景拍摄模式和头颅正侧位拍摄模式，所述系统包括：
    射源，配置为向被测对象发射锥形束X射线；
    平板探测器，配置为对经过所述被测对象的X射线进行探测；
    旋转驱动装置，配置为转动所述射源和平板探测器、或者控制旋转装置使得所述被测对象进行转动；
    数据处理装置，配置为接收工作模式指令以选择与所述口腔CT拍摄模式、口腔全景拍摄模式和头颅正侧位拍摄模式中的一种模式对应的工作模式控制参数组；以及
    控制装置，配置为接收所选择的成像模数控制参数组，对所述旋转驱动装置进行控制，以及对所述射源及平板探测器进行控制，以进行成像拍摄，
    其中，所述射源、平板探测器和旋转驱动装置的数量为一个，以形成单路成像系统。
  2. 如权利要求1所述的系统，其特征在于，所述工作模式还包括快速定位模式，并且所述数据处理装置配置为根据接收的工作模式指令来选择所述快速定位模式，在所述快速定位模式中，采用所述口腔CT拍摄模式的拍摄轨迹，X射线的辐射剂量低于所述口腔CT拍摄模式的X射线的辐射剂量，以便根据所述快速定位模式的定位结果来进行所述成像系统的自适应摆位。
  3. 如权利要求2所述的系统，其特征在于，在所述快速定位模式中，所述旋转驱动装置控制的转动速度快于所述口腔CT拍摄模式的转动速度，和/或所述快速定位模式的重建像素大于所述口腔CT拍摄模式的重建像素。
  4. 如权利要求2所述的系统，其特征在于，所述系统还包括摆位控制装置，根据所述定位结果，所述摆位控制装置根据所述快速定位模式的拍摄图像计算得到的滚转角和偏航角来调节所述射源的高度以及控制旋转装置转动，以便实现所述自适应摆位。
  5. 如权利要求1所述的系统，其特征在于，所述射源与所述平板探测器之间的距离SID为1.5m～2.5m，所述距离SID和所述射源与旋转轴之间的距离SAD的差值为0.2m～0.4m。
  6. 如权利要求5所述的系统，其特征在于，所述距离SID为1.7m，且所述距离SID与所述距离SAD的差值为0.25m。
  7. 如权利要求1所述的系统，其特征在于，所述旋转驱动装置使得所述被测对象进行转动，以便相对于转动的被测对象，所述射源和探测器绕固定旋转中心沿着圆轨迹进行成像拍摄。
  8. 如权利要求7所述的系统，其特征在于，
    所述口腔全景拍摄模式包括第一口腔全景拍摄模式，在所述第一口腔全景拍摄模式中，所述被测对象被转动，使得所述成像拍摄为沿着所述圆轨迹的变速转动拍摄；和/或
    所述口腔全景拍摄模式包括第二口腔全景拍摄模式，在所述第二口腔全景拍摄模式中，所述被测对象被转动，使得所述成像拍摄为沿着所述圆轨迹的匀速转动拍摄。
  9. 如权利要求8所述的系统，其特征在于，
    在所述第一口腔全景拍摄模式中，通过所述探测器采集一系列二维投影数据，并且通过所述数据处理装置对一系列二维投影数据进行重排处理来生成第一全景图像；
    在所述第二口腔全景拍摄模式中通过所述探测器采集一系列二维投影数据，并且通过所述数据处理装置对一系列二维投影数据进行插值处理来生成第二全景图像。
  10. 如权利要求4所述的系统，其特征在于，选择所述口腔全景拍摄模式且进行所述自适应摆位之后，所述数据处理装置得到被测对象的牙弓曲线和确定虚拟旋转轴参数，基于所述虚拟旋转轴参数，计算牙弓曲线的每个成像点所对应的射源对应位置与探测器有效位置，所述旋转驱动装置转动所述被测对象，以便在沿着所述圆轨迹进行成像拍摄过程中，分别获取每个成像点所对应的所述射源对应位置处所发射的X射线在所述每个成像点所对应的所述探测器有效位置的X射线投影数据，所述数据处理装置将所述每个成像点所对应的X射线投影数据进行处理，以便得到口腔全景图像。
  11. 如权利要求10所述的系统，其特征在于，所述数据处理装置配置为：
    获取所述被测对象的被测部位的三维图像；
    确定第一横断面图像，所述第一横断面图像为所述三维图像中的牙弓层；
    对所述第一横断面图像进行处理以获得包含被测对象的牙齿的骨阈值分割图像；
    确定骨阈值分割图像中各个像素点在预定极坐标系中的极坐标；
    根据骨阈值分割图像中以预定角度为极角且像素值非零的像素点的极径，确定每个预定角度对应的目标极径；
    以每个预定角度及其目标极径为数值对形成数值对序列，所述数值对序列为牙弓曲线的采样点数据；以及
    利用采样点数据拟合得到被测对象的牙弓曲线。
  12. 如权利要求10所述的系统，其特征在于，所述数据处理装置配置为：
    以所述牙弓曲线上每个成像点，计算拍摄中经过该成像点的X射线，并获取所述X射线在探测器上的投影数据；
    将经过该成像点的X射线的投影数据按权重累加，得到该成像点的成像值，一条牙弓曲线得到一行数据；以及
    将所述牙弓曲线在垂直方向上下移动，得到多行数据，按顺序排列所述多行数据，得到完整的口腔全景图像。
  13. 如权利要求11所述的系统，其特征在于，所述数据处理装置配置为：以三维图像中Z轴坐标对应预定牙弓位置的横断面图像作为所述第一横断面图像；或者利用预训练的神经网络对所述三维图像进行处理以确定所述第一横断面图像。
  14. 如权利要求11所述的系统，其特征在于，所述数据处理装置配置为：对 第一横断面图像执行骨阈值分割和高斯平滑处理，以获得包含被测对象的牙齿的骨阈值分割图像。
  15. 如权利要求11所述的系统，其特征在于，所述数据处理装置配置为：确定骨阈值分割图像中以第一预定角度为极角的像素值非零的像素点中极径最小的第一像素点和极径最大的第二像素点；以所述第一像素点和所述第二像素点的极径平均值作为所述第一预定角度的目标极径。
  16. 一种基于如权利要求2所述的系统的快速定位方法，其特征在于，包括：
    启动所述快速定位模式，发射低剂量的X射线；
    接收及重建CT图像，获取被测对象的当前位姿；以及
    基于所述当前位姿，所述成像系统进行自适应摆位，以便进行所述口腔全景拍摄模式或所述头颅正侧位拍摄模式的成像拍摄。
  17. 如权利要求16所述的快速定位方法，其特征在于，在所述快速定位模式中，所述旋转驱动装置控制的转动速度快于所述口腔CT拍摄模式的转动速度，和/或所述快速定位模式的重建像素大于所述口腔CT拍摄模式的重建像素。
  18. 如权利要求16所述的快速定位方法，其特征在于，当需要选择所述口腔全景拍摄模式进行成像拍摄而启动所述快速定位模式的情况下，对所述CT图像进行重建，以获得所述被测对象的当前牙弓曲线，以便根据所述当前牙弓曲线和拍摄所需位姿，来进行所述成像系统的自适应摆位。
  19. 如权利要求16所述的快速定位方法，其特征在于，当需要选择所述头颅正侧位拍摄模式进行成像拍摄而启动所述快速定位模式的情况下，对所述CT图像进行重建，得到所述被测对象的头颅相对于标准位姿的偏航角和/或滚转角，通过调整所述偏航角和/或滚转角来进行所述成像系统的自适应摆位。
  20. 如权利要求19所述的快速定位方法，其特征在于，
    基于得到的所述滚转角，通过所述旋转驱动装置转动被测对象，使得所述被测对象的左头颅部分和右头颅部分对称，其中通过所述被测对象的头颅中心的直线将头颅分为所述左头颅部分和所述右头颅部分称；和/或
    基于得到的所述偏航角，调整所述射源的位置，以便使得所述射源、被测对象的左耳孔、被测对象的右耳孔共线。
PCT/CN2022/133641 2021-11-24 2022-11-23 口腔锥形束x射线成像系统及其快速定位方法 WO2023093748A1 (zh)

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