Method and system for obtaining operating parameters of 3D X-ray acquisition

Abstract

The present invention relates to a method for obtaining operating parameters of an x-ray CBCT imaging device taking into account the acquisition of a set of data of a maxillofacial region of a patient, the method comprising: identifying a first maxillofacial region of interest (ROI1) of the patient; determining the height of a horizontal plane of the patient's first maxillofacial region of interest (ROI1) when the patient is in an occlusal position or biting a patient positioning assembly; acquiring a first set of data relative to the patient's first maxillofacial region of interest (ROI1) including the horizontal plane using x-ray CBCT imaging through a slit-shaped collimator window; and reconstructing axial CBCT slices including the horizontal plane based on the first set of data relative to the patient's first maxillofacial region of interest (ROI1). - displaying reconstructed axial CBCT slices of the patient's maxillofacial first region of interest (ROI1) from the acquired first set of data; - defining at least in part a second region of interest (ROI2) based on an intersection of the displayed reconstructed axial CBCT slices of the patient's maxillofacial first region of interest (ROI1) with ROI1; and - obtaining operating parameters of the x-ray CBCT imaging device based at least on the defined second region of interest (ROI2) in consideration of the acquisition of a second set of data including the defined second region of interest (ROI2). [Selected figure] Figure 3

Description

Technical Field

[0001] The present disclosure generally relates to the field of dental x-ray imaging, and more specifically to the field of x-ray CBCT (Cone Beam Computed Tomography) imaging. More specifically, the present disclosure relates to a method for obtaining operating parameters of an x-ray CBCT imaging device and a system for obtaining operating parameters of x-ray CBCT imaging of a patient's craniofacial region.

Background Art

[0002] Conventional methods and systems for obtaining x-ray images of a patient's craniofacial region via x-ray CBCT imaging very often require irradiating a relatively reduced-sized local area of the patient's entire craniofacial region with x-ray dose for a certain exposure time in order to obtain details regarding important teeth, specific areas, etc. for the dentist.

[0003] Predefined device settings corresponding to an average patient enable reaching the desired local area.

[0004] However, due to variations among patients regarding average predefined settings, re-imaging of the patient may occur, which may lead to an increase in the x-ray dose received by the patient.

[0005] Such systems may have achieved a certain degree of success in their specific application fields, but still, there is a need to improve these methods and systems.

Summary of the Invention

[0006] An object of the present disclosure is to avoid unnecessary x-ray dose to the patient when receiving an x-ray CBCT examination.

[0007] Another object of the present disclosure is to improve the positioning accuracy of the patient's data volume obtained via x-ray CBCT data acquisition while restricting patient dose exposure.

[0008] Yet another object of the present disclosure is to optimize the adjustment of the operating parameters or acquisition parameters of an x-ray CBCT imaging device before subjecting a patient to an x-ray CBCT examination.

[0009] These objects are given by way of example only, and such objects can be illustrative of one or more embodiments of the present invention. Other desirable objects and advantages that can be uniquely achieved by the present invention may occur to or become apparent to those skilled in the art. The present invention is defined by the appended claims.

[0010] According to one aspect of the present disclosure, a method of obtaining operating parameters of an x-ray CBCT imaging device in consideration of obtaining a set of data of a patient's craniofacial region, - identifying a first region of interest ROI1 of the patient's craniofacial region; - determining a height of a horizontal plane of the first region of interest ROI1 of the patient's craniofacial region when the patient is in an occlusion position or when the patient positioning assembly bites; - using x-ray CBCT imaging to obtain a first set of relative data for the first region of interest ROI1 of the patient's craniofacial region including the horizontal plane through a slit-shaped collimator window; - reconstructing an axial CBCT slice including the horizontal plane based on the first set of relative data for the first region of interest ROI1 of the patient's craniofacial region; - displaying the reconstructed axial CBCT slice of the first region of interest ROI1 of the patient's craniofacial region from the first set of acquired data; - at least partially defining a second region of interest ROI2 based on the displayed reconstructed axial CBCT slice of the first region of interest ROI1 of the patient's craniofacial region and the intersection with ROI1; - obtaining the operating parameters of the x-ray CBCT imaging device based at least on the defined second region of interest ROI2, considering obtaining a second set of data including the defined second region of interest ROI2 A method including is provided.

[0011] The method according to an embodiment of the present invention is a novel method that enables reduction of patient exposure to X-rays.

[0012] The method according to an embodiment of the present invention is a novel method that obtains a CBCT slice including a first region of interest ROI1 of the patient's craniofacial region, uses a first X-ray "pre-emission" having an X-ray dose for reconstruction, and enables selection or definition of a more specific area or region of interest by a practitioner. This definition or selection of a more specific area or region of interest enables obtaining of adapted operating parameters or acquisition parameters used for another "emission" or second X-ray CBCT data acquisition.

[0013] Typically, a low dose is used for "pre-emission". Low means a dose that does not exceed 20% of the default or standard dose (obtained using default or standard parameters) used in known x-ray examinations (such as 3D, panorama, etc.), preferably less than 10%, and more preferably less than 5%. The low dose can be used because CBCT slices do not require as many details as default acquisition or conventional acquisition, and the patient should not be overly exposed to x-rays. However, the CBCT slice information must be sufficient to provide morphological information (such as tooth position, tooth geometry, etc.) that enables a dentist to select a more specific area or region of interest. The information contained in the CBCT slice is specific to the patient. Therefore, the use of such information enables a more adapted and / or more accurate definition of a more specific area or region of interest. This form of processing is clearly not based on averaged patient data as in the past. Therefore, the operation parameters or acquisition parameters obtained based on such a more specific area or region of interest of the patient are more reliable and accurate because they represent the patient. The CBCT slice can be a thin slice including ROI1. The slice can have a thickness or height of less than 100 μm or can be an integrated slice having a thickness or height of usually about 2 - 3 mm.

[0014] The patient is preferably in a repeatable position during "pre-emission", which means that for subsequent "emission" or acquisition using the obtained parameters, the patient is in the same or a very close position. In this regard, the setting parameters of the x-ray device for positioning the patient are retained in the memory.

[0015] According to a possible feature or aspect, - Defining at least partially a second region of interest ROI2 based on the displayed and reconstructed axial CBCT slice of the patient's craniofacial first region of interest ROI1 includes defining the position of the second region of interest ROI2 in the xy plane of the axial slice. Defining the second region of interest ROI2 further includes defining the position (height) of the second region of interest ROI2 along the z-axis perpendicular to the xy plane of the axial slice. Defining the z-axis position of the second region of interest ROI2 is preceded by acquiring a transverse x-ray scout view that includes the first region of interest ROI1 of the patient's craniofacial region, the scout view being usable to position both the height of the horizontal plane of ROI1 and the height and size in the yz plane of ROI2, acquiring an optical image that includes the first region of interest ROI1 of the patient's craniofacial region including landmarks, performing a physical measurement on the first region of interest ROI1 of the patient's craniofacial region using a patient positioning device and including one of The method further includes adjusting the height of the second region of interest ROI2 based on the transverse scout view, the optical image, or the physical measurement performed. The z-axis position of the second region of interest ROI2 is determined in advance. The second region of interest ROI2 has a size selected from a set of predetermined values. Defining the z-axis position of the second region of interest ROI2 is based on determining the height of the horizontal plane of the first region of interest ROI1 of the patient when the patient is in the occlusion position or biting on a patient positioning accessory. Determining the height of the horizontal plane of the first region of interest ROI1 of the patient when the patient is in the occlusion position or biting on a patient positioning accessory is preceded by acquiring a transverse x-ray scout view that includes the first region of interest ROI1 of the patient's craniofacial region, acquiring an optical image that includes the first region of interest ROI1 of the patient's craniofacial region including landmarks, performing a physical measurement on the first region of interest ROI1 of the patient's craniofacial region using a patient positioning device and including one of - The first set of data is acquired while the patient is maintained at a first position via a patient positioning device, said first patient position being defined by a set of setting parameters of the patient positioning device, - The method includes a previous adjustment of the setting parameters of the patient positioning device prior to the acquisition of a second set of data, - The first set of data and the second set of data are temporally separated, - The x-ray CBCT imaging device includes an x-ray source and an x-ray sensor both operable to simultaneously move around the patient's head along a predetermined trajectory, and obtaining the operating parameters of the x-ray CBCT imaging device based on a defined second region of interest ROI2 includes adjusting the trajectories of both the x-ray source and the x-ray sensor based on the defined second region of interest ROI2.

[0016] According to another aspect of the present disclosure, a system for obtaining operating parameters related to x-ray CBCT imaging of a patient's craniofacial region, - An x-ray source and at least one x-ray sensor configured to move around the patient's craniofacial first region of interest ROI1 while irradiating the patient's craniofacial first region of interest ROI1 with a slit-shaped x-ray beam to obtain a first set of data relative to the patient's craniofacial first region of interest ROI1 when the patient is in an occlusion position or biting a patient positioning accessory, wherein the patient's craniofacial first region of interest ROI1 includes a horizontal plane of the patient in the occlusion position or a plane parallel thereto, the x-ray source and at least one x-ray sensor, - Reconstructing an axial CBCT slice including an occlusion plane or a plane parallel thereto based on the first set of data relative to the patient's craniofacial first region of interest ROI1, Displaying a reconstructed axial CBCT slice of the patient's craniofacial first region of interest ROI1 from the first acquired set of data using a view for at least partially defining a second region of interest ROI2 based on the displayed reconstructed axial CBCT slice and an intersection with the latter, Considering the acquisition of a second set of data including a defined second region of interest ROI2, obtain the operating parameters of the x-ray CBCT imaging device based at least on the defined second region of interest ROI2 a processor configured as A system is provided that includes.

[0017] The microprocessor may be configured to perform any of the steps, operations, features, or aspects of the above method.

[0018] According to another aspect of the present disclosure, a computer storage medium having instructions stored therein for causing a computer or microprocessor to execute the method briefly described above is provided.

Brief Description of the Drawings

[0019] The foregoing and other objects, features, and advantages of the present invention will become apparent from the following more particular description of embodiments of the invention shown in the accompanying drawings.

[0020] The elements of the drawings are not necessarily to scale with each other.

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 7

[0022] The following is a detailed description of the preferred embodiments, with reference to the drawings, in which the same reference numerals identify identical elements of the structure in each of the plurality of drawings.

[0023] FIG. 1 shows an embodiment of an x-ray imaging device, specifically an extraoral imaging device 10. The device 10 includes a support structure including a support frame 12 that can be a column.

[0024] The support structure also includes a horizontal mount 14 that can be supported or held by the vertical column 12. The horizontal mount 14 extends away from the vertical column 12 and can be substantially perpendicular thereto. The horizontal mount 14 can move vertically relative to the vertical column 12.

[0025] More specifically, the horizontal mount 14 is fixedly attached to a vertical portion 12a that is slidably attached to a fixed vertical portion 12b. For example, an actuator (not shown in this figure), such as an electric type, disposed behind the vertical column, can be commanded to drive the horizontal mount 14 in a controlled manner for vertical movement.

[0026] The horizontal mount 14 can support the gantry 16. The gantry 16 is movable relative to the support structure, and more specifically relative to the horizontal mount 14. The gantry 16 can be rotatable relative to the horizontal mount 14, more specifically. The gantry 16 can be stationary during the operation of the imaging process, or can be rotatable about the vertical axis of rotation, following one of a plurality of predetermined trajectories according to a selected imaging process. A known mechanism (not shown in this figure) for driving the gantry 16 to a given movement is integrated inside the horizontal mount 14. For example, such a drive mechanism includes a motor for providing a first movement in the xy plane, such as two stepping motors, for example, and a motor for providing a rotational movement about the vertical axis z, such as a brushless motor, for example.

[0027] The gantry 16 supports both the x-ray source 18 and at least one x-ray sensor 20 arranged corresponding to the x-ray source. The x-ray source 18 and at least one x-ray sensor 20 can be arranged facing each other. The gantry 16 can include two opposing downwardly extending arms, that is, a first arm 16a that supports the x-ray source 18 attached thereto, and a second opposing arm 16b that supports at least one x-ray sensor 20 attached thereto.

[0028] The x-ray source 18 includes a conventional collimator (not shown in FIG. 1). The position of the collimator along the vertical axis z and the opening of the slit collimator window can be adjusted so that the collimated x-ray beam irradiates the region of interest in the patient's head or the patient's craniofacial region.

[0029] When activated, the x-ray source 18 emits an x-ray beam, which irradiates the imaging area of the patient's craniofacial region (or the patient's craniofacial region of interest) here before colliding with at least one x-ray sensor 20.

[0030] In this embodiment, the x-ray source 18 and at least one x-ray sensor 20 are configured to move around the craniofacial region of the patient along a predetermined trajectory while irradiating an imaging area of the craniofacial region of the patient.

[0031] In this embodiment, the apparatus 10 is used, as will be understood later, in an x-ray CBCT operation mode, and more specifically, in a CBCT operation mode for obtaining 3D CBCT slices. The apparatus 10 can be considered as an x-ray CBCT imaging apparatus that performs volumetric tomography or computed tomography to obtain 3D images.

[0032] However, the apparatus 10 can also function according to one or more other operation modes or imaging processes, such as panorama, cephalometry, etc.

[0033] The apparatus 10 can also operate according to such different operation modes or only some of those operation modes.

[0034] In this regard, another sensor or other sensors can be used, and the x-rays can accordingly be collimated to irradiate an area of the patient's head as the craniofacial region of interest of the patient (or the entire head of the patient) having a specific shape according to the selected operation mode and the choice of the practitioner.

[0035] At least one x-ray sensor 20 includes a sensor adapted to one of the operation modes of the apparatus. For example, this sensor can be a sensor adapted to perform a CBCT scan, such as a volumetric sensor or a computerized sensor (e.g., rectangular, square shape), or a plurality of sensors of the previous type.

[0036] The support structure can also include a patient positioning accessory support member 22, which is an arm here. The arm 22 is connected to the support frame, more specifically, the vertical column 12. The patient positioning arm 22 is movable relative to the support frame. More specifically, the arm 22 can slide along the vertical column 12 to move up and down when commanded, for example, via a suitable actuator(s) of the electric type. The patient positioning arm 22 extends from an arm support 22a slidably attached relative to a fixed vertical portion 12b. The patient positioning arm 22 extends along the device in a direction substantially corresponding to the extending direction of the horizontal mount 14. The patient positioning arm 22 is here arranged laterally with respect to the device in a relationship substantially parallel to the horizontal mount 14.

[0037] The patient positioning arm 22 serves to position the patient at a given position within the device.

[0038] The patient positioning arm 22 can include one of a plurality of patient positioning accessories disposed generally at or near the free end 22b of the arm. These accessories can also or instead be considered a holding system.

[0039] These patient positioning accessories are capable of positioning the anatomical structure of the patient's head according to different orientations and fixing the patient's head during the examination to reduce all possible movements.

[0040] For each type of specific examination performed by the device according to different operating modes, there is one or more types of patient positioning accessories. The arm 22 is generally configured to handle each of these different types of patient positioning accessories one at a time.

[0041] As shown in FIG. 1, one of these patient positioning accessories, labeled 24, includes two temporary holding members that extend upward from the arm 22 to which they are removably attached. Only one of the temporary holding members is shown, the other being hidden by the arm 16b

[0042] The patient positioning accessory 24 can also include a chin rest 26 that extends upward from the arm 22 to which it is removably attached. The chin rest 26 is disposed between the two temporary holding members for positioning the patient's head for panoramic examination. A standard bite block can be further added to the chin rest. As an alternative, a Frankfort guide bite block can be used for panoramic examination

[0043] Other possible types of patient support accessories can be considered, namely, nasal support for temporal mandibular joint examination with the mouth open and closed, a bitten support for 3D examination (denture type), a forehead support for 3D examination (forehead type), a combination of occlusal support and forehead support, and others

[0044] Furthermore, a seat (not shown in this figure) can be used with respect to the patient according to the type of examination. This arrangement can also help to set the position of the patient and to set the reproducibility of this position with respect to future structural data acquisition. Setting parameters (including the relative position with respect to the seat) that define the position of the patient can be stored in memory even if subsequent data acquisition is not performed on the same device

[0045] As shown in FIG. 1, the handle assembly 34 can be positioned at the free end 22b of the arm, below the arm, in a relationship parallel to the arm. This handle assembly 34 includes two separate vertical handle portions 34a, 34b that the patient can grasp when undergoing an imaging process to remain stationary

[0046] Overall, this handle assembly 34 has a U-shape including a horizontal base portion 34c and two vertical upwardly extending branches 34a, 34b that are fixed to the arm 22. Each branch serves as a vertical handle portion.

[0047] Alternatively, other handle assemblies can be used for handling the arm 22.

[0048] The patient positioning arm 22 can also support a monitor or display assembly 36 that enables the operator of the device to view the images displayed thereon, interact therewith, and drive certain functions of the device.

[0049] FIG. 2 is a schematic diagram of the main functional components or assemblies of a system 40 for obtaining operating parameters used in this embodiment. Some or all of these components or assemblies may or may not be part of the device 10.

[0050] In this embodiment, the system 40 is disposed within the device 10.

[0051] The system 40 includes an acquisition assembly 42 that includes the x-ray source and x-ray sensor of the device of FIG. 1.

[0052] The system 40 includes a control assembly 44 that is connected to the acquisition assembly 42 and configured to control the operation of the acquisition assembly 42 in accordance with the method of the embodiments of the present invention.

[0053] The control assembly 44 is specifically used to enable the operation of the device 10 and its various components / assemblies in a more conventional form, and can also be used to perform, for example, CBCT scans, reconstruct 3D volumes (3D x-ray image data), and perform data acquisitions such as panoramas and cephalometry.

[0054] The control assembly 44 specifically includes a processor and, perhaps, one or more storage media storing a computer program having instructions to control the system 40 to practice one or more embodiments of the method according to the present invention. When the microprocessor executes the computer program stored in the one or more storage media, the microprocessor is considered to be configured to execute the steps or operations of the embodiment method according to the present invention.

[0055] One aspect of the present invention also targets a computer program product including one or more storage media.

[0056] The one or more storage media can be, for example, magnetic storage media such as magnetic disks (such as floppy disks) or magnetic tapes, optical storage media such as optical disks, optical tapes, or machine-readable bar codes, solid-state electronic storage devices such as random access memory (RAM) or read-only memory (ROM), or any other physical device or medium used to store such a computer program.

[0057] The stored computer program(s) or other stored computer program(s) can also have instructions to control the apparatus 10 to practice more conventional methods such as conventional methods of obtaining 3D volumes.

[0058] The system 40 can also include one or more external storage media 46 that store different volumes of data reconfigured by the apparatus here during an x-ray imaging process, such as a CBCT imaging process. The one or more external storage media 46 can be of the same type as those described above.

[0059] One or more external storage media 46 can store the above computer program(s) for controlling system 40 and / or, more generally, for controlling device 10, instead of one or more storage media specific to control assembly 44.

[0060] System 40 can include a display assembly 48 that can correspond to display assembly 36 of FIG. 1 and that further includes one or more monitors or screens here. Display assembly 48 is connected to control assembly 44.

[0061] Display assembly 48 can automatically or on demand display selected images of a patient's craniofacial region obtained from an x-ray CBCT imaging process performed by device 10.

[0062] The display assembly operates under the control of control assembly 44.

[0063] System 40 can further include a user interface assembly 50 connected to display assembly 48 and control assembly 44. User interface assembly 50 enables a user, such as a practitioner or technician, to interact with display assembly 48 and perhaps control assembly 44 that executes image processing / algorithms to perform various tasks.

[0064] User interface assembly 50 can include one or more interactive devices connected to display assembly 48, such as, but not limited to, a pointing device, such as a computer mouse, joystick, stylus, keypad, touchpad, etc.

[0065] Other types of interactive devices or tools (user interface tools), such as touchscreens, tool icons that can be displayed on the screen or when commanded, can be used instead of or in addition to them.

[0066] Assemblies 44, 46, 48, and 50 can be disposed wholly or partially within the arm 22 of the apparatus 10 or can be disposed relatively remotely with respect to the apparatus (e.g., in the same room or separate rooms or other locations). If the control assembly 44 is not disposed within the apparatus 10, another control assembly can be present within the apparatus to control the acquisition assembly 42 and to control the operation of the apparatus in general. However, the entire description applies equally regardless of the location of the assemblies.

[0067] The above also applies when the assemblies 42, 44, 46, 48, and 50 relate to another x-ray imaging apparatus.

[0068] The method of an embodiment according to the present invention will now be described with reference to FIG. 3 showing the algorithms of the corresponding computer program(s). This algorithm refers to other algorithms that may be shown in other figures and may be part of the same computer program or correspond to other computer programs.

[0069] Regarding its operation, the method of the embodiment can utilize the functional components or assemblies that can be described above in relation to the apparatus 10 of FIG. 1 and FIG. 2. Alternatively, the functional components or assemblies required to execute this method can be the functional components or assemblies of another x-ray imaging apparatus, but these can be made to conform to the configuration of FIG. 2 (not all components of FIG. 2 need to be present).

[0070] The patient is first positioned, for example, in a seated position between the x-ray source 18 and the x-ray sensor 20 of the acquisition assembly 42 within the working space of the apparatus 10. This method begins with an identification step S1 of identifying a first region of interest ROI1 of the patient's craniofacial region, represented as ROI1. The practitioner identifies ROI1 based on predetermined criteria such as the type of examination to be performed on a second region of interest ROI2 of the patient's craniofacial region, the second region of interest ROI2 itself, and the like.

[0071] For example, ROI1 can include the upper and lower jaws, parts of both jaws, only one jaw, or a part of a single jaw, depending on the practitioner's interest.

[0072] This method further includes a height determination step S2. For the execution of this step, the patient bites within a patient positioning member or patient positioning accessory, and then his / her teeth are separated by 2 to 3 millimeters. Such a patient positioning member or patient positioning accessory can be detachably attached to the arm 22. Such a patient positioning member or patient positioning accessory can be a bite block, such as a Frankfurt guide bite block used for panoramic examinations, a standard bite block, a bitten 3D support, and the like.

[0073] FIG. 5 shows the ROI1 identified / selected by the practitioner on a previously acquired lateral scout view LSV (a mere projection of data acquired via lateral x-ray data acquisition) of the patient's craniofacial region. In FIG. 5, the patient's face is also shown as the background. The resulting view can be displayed on the display assembly 48.

[0074] In FIG. 5, the bite block is not shown for clarity.

[0075] In the alternative, the patient's jaws may be in an occlusal position, i.e., the patient's upper and lower jaws may be in contact with each other. The patient's head can be held in place via a chin rest, a forehead support including the chin rest, etc. The identified ROI1 may include the occlusal plane in this alternative arrangement.

[0076] The purpose of this step is to determine the height of the horizontal plane within ROI1. This height is then used for the first x-ray data acquisition, which will be described later.

[0077] This horizontal plane can be the mid-plane of ROI1 or another plane within ROI1.

[0078] Regarding the execution of this step, the patient may be positioned such that their Camper's plane is horizontal.

[0079] Figure 4 shows different forms of determining the height of the horizontal plane.

[0080] The first form is to acquire a lateral scout view of the patient's x-ray via the acquisition assembly 42 operated under the control of the control assembly 44 in FIG. 2 (step S2.1). The position of the scout view relative to the patient's jaws can be assumed to have been previously determined based on a predetermined average value.

[0081] FIG. 5, which has already been mentioned above, schematically shows a lateral scout view of the patient's x-ray acquired in a conventional form. Such a view provides information regarding the positions of the upper and lower jaws here and shows the first region of interest ROI1 of the patient's craniofacial region, which was discussed above and identified by the practitioner. ROI1 shows the upper part of the patient's lower jaw here and extends towards the back of the patient's head. However, the extent of ROI1 can be shorter along the y-axis. In the alternative, ROI1 can be positioned differently relative to the jaws by the practitioner, and its extent may or may not be shorter along the y-axis.

[0082] The important horizontal plane of ROI1 can be positioned by the practitioner on the display or determined by calculation. The horizontal plane can be the midplane of ROI1 as already stated above.

[0083] Next, in step S2.2, the height of this horizontal plane is determined based on the known position of the scout view relative to the positioning accessory (here a bite block) of the patient used in the conventional form and the known position of the latter relative to the x-ray device, specifically the arm 22 or any other reference part of the device. It should be noted that the position of the x-ray source relative to the arm is also known.

[0084] Figure 5 shows the z-axis position of the horizontal plane described above by a line denoted as L.

[0085] Two other forms of determining the height of the horizontal plane are shown in Figure 4.

[0086] The second form (step S2.3) prepares to acquire at least one optical image (in the biting position, i.e., occlusion position) of the patient including the first region of interest ROI1 of the patient's craniofacial region including landmarks. The at least one image is more specifically a face image taken by a camera, and the landmarks can be of an anatomical type (e.g., the corner of the mouth landmark or a landmark added to the patient's face. The camera can be positioned on the device 10, for example, on the arm 22, or independently of the device. In Figure 1, an example of the camera 52 is arranged next to the x-ray source 18. Alternatively or in addition, another position of the camera can be selected.

[0087] In an alternative, a horizontal optical image of the patient may be more convenient than a frontal image.

[0088] One or more landmarks are representatives of geometric positions that are known or can be easily known by calculation relative to the tooth roots.

[0089] As a result, the height of the horizontal plane (e.g., the mid-sagittal plane) of ROI1 that can be used for the first x-ray data acquisition can thus be determined by a calculation (step S2.2) based on the position of one or more landmarks.

[0090] The third form (step S2.4) prepares to perform a physical measurement of the patient's (at the biting position, i.e., the occlusal position), more specifically, the first region of interest (ROI1) of the patient's craniofacial region, using a patient positioning device or a patient positioning accessory.

[0091] A patient positioning accessory attached to the arm 22 in FIG. 1, such as a bite block or the like, can be used. The bite block is attached to the arm at a fixed position, and the height of the bite block relative to the arm can be known or measured. The average size (height) of the teeth of a given patient (adult, child, etc.) is also known, which makes it possible to determine the position of the tooth roots and thus the position of the tips of the teeth, i.e., the position of the tooth roots relative to the bite block.

[0092] As a result, the height or position of the horizontal plane of ROI1 relative to the arm can be determined by the above-described measurements and / or calculations.

[0093] In an alternative, a sensor disposed within the bite block or the like can provide appropriate measurement data, and the height or position of the occlusal plane relative to the arm can then be determined therefrom.

[0094] Thereafter, the height of the horizontal plane of ROI1 that can be used for the first x-ray data acquisition can be determined based on the position of the occlusal plane (step S2.2). This previous determination phase aims to determine the height at which the first set of data regarding ROI1 is acquired.

[0095] After the height of the horizontal plane has been determined, the apparatus 10 is set by the control assembly 44 in a configuration that enables the acquisition of a first set of relative data for the ROI1 supplied by step S3 of FIG. 3. The first set of data can correspond to the entire ROI1 or a selected part thereof.

[0096] - First, a set of an x-ray source and an x-ray sensor is commanded by the control assembly 44 to move to the determined height so that the x-ray source is at a height suitable for acquisition, this arrangement making it possible to simply reduce the x-ray dose, - Second, two forms are used to set the apparatus into the acquisition configuration: the x-ray source remains at the same altitude and the x-ray collimator is moved so as to orient the x-ray beam upward towards the determined height of the plane.

[0097] For this first data acquisition, the patient remains in the biting position (or occlusion position) provided in the previous step S2. The patient can also be positioned so that his / her Campers plane is horizontal with respect to step S2.

[0098] The patient is positioned at a position (first position) suitable for this first data acquisition using, for example, a patient positioning device or patient positioning accessory of the apparatus (here, a bite block) and possibly a seat.

[0099] The different setting parameters that define the patient's first position, such as the accessory used, the position of this accessory on the apparatus if multiple position settings are available (e.g., different possible heights of the support), the relative accessory position with respect to the patient (e.g., multiple width values are possible according to the patient's face width), this parameter if the height of the possible seat is adjustable, etc., can be recorded or memorized by the practitioner, together with the view for their reuse in subsequent data acquisitions (e.g., via a user interface assembly to a storage medium).

[0100] ​ For this first data acquisition, the apparatus 10 operates in a CBCT mode under the control of the control assembly 44.

[0101] According to this mode, the x-ray collimator aperture is adjusted as a slit-shaped collimator window to create a slit-shaped x-ray beam focused on the first region of interest (ROI1) of the patient's craniofacial region including the horizontal plane.

[0102] This slit shape is adjusted to cover ROI1 and preferably a thin volume of height.

[0103] The horizontal plane of ROI1 is targeted thanks to the collimator position and the adjustment at the collimator window opening.

[0104] Figure 6A shows two different relative positions between the x-ray source 18 and ROI1 (ROI1 can be replaced by a part of it instead, and the rest of this description applies equally) with different apertures of the x-ray collimator 19. As shown, the x-ray source 18 is aligned with the lower end of the sensor 20. The axis of rotation A of the set consisting of the source and the sensor is also shown. To capture and reconstruct the CBCT slices, the vertical collimator aperture depends on the relative position of the collimator with respect to the source-sensor alignment. The minimum aperture is obtained when the source-sensor axis passes through the collimator. In other words, the midplane of the collimated x-ray beam can be adjusted to obtain the minimum aperture required for slice reconstruction with respect to the collimator.

[0105] Preferably, the source-sensor axis passes through the base of the collimator window and the lower end or boundary of ROI1.

[0106] The x-ray source is operated using a first x-ray dose that can be quantified as a low dose with respect to the x-ray dose used for a subsequent second data acquisition.

[0107] The first x-ray dose is selected to minimize the patient's x-ray exposure. The x-ray dose depends on the volume of patient data acquired. The volume should preferably be as small as possible with respect to data acquisition and does not need to be of high resolution. This is because the useful information required for the rest of this method resides in the morphological characteristics or data (tooth position, characteristic dimensions, etc.) of the first region of interest in the patient's craniofacial region. Preferably, such information does not require many details within the acquired data. However, the volume is not necessarily thin, and its size depends on the resolution of the image. When the dose has to be lowered, generally a compromise between the size of the volume and the resolution has to be made.

[0108] Typically, the first x-ray dose does not exceed 20% of the second dose used for subsequent second data acquisition.

[0109] Preferably, the first x-ray dose does not exceed 10% of the second dose, and more preferably does not exceed 5% of the second dose.

[0110] For example, the first x-ray dose can be about 4 μSv with respect to the generation of CBCT slices.

[0111] The information required within the data volume (CBCT slices) acquired during this first acquisition is used to properly position the data volume acquired during the subsequent second acquisition.

[0112] Returning to FIG. 3, the third step S3 of acquiring the first set of data (3D volume) is based on the above settings and adjustments. This first acquisition can be regarded as a "pre-shot" to provide useful information for "emission". The exposure time of this pre-shot can be relatively short, for example, about 5 seconds.

[0113] The next step S4 is a reconstruction step of reconstructing CBCT slices based on the first set of acquired data using conventional CBCT data processing techniques (for example, the FDK algorithm).

[0114] The reconstructed CBCT slice includes the horizontal plane of ROI1 and is based on a first set of acquired data for the patient's first craniofacial region of interest (ROI1).

[0115] As an example of the low-resolution of the first acquired data, a voxel size of about 500 μm within the reconstructed CBCT slice can be obtained. For example, the thickness or height of the slice is between 10 voxels and 30 voxels, which corresponds to a range between 1 mm and 15 mm. Preferably, a range between 1 mm and 5 mm can be selected.

[0116] The reconstructed CBCT slice can take a cylindrical shape (other shapes can be used), and the diameter is between 120 mm (for small skull dimensions) and 160 mm. A smaller diameter may be convenient. The CBCT slice can be limited here as a thin slice. In other example embodiments, the acquisition of the entire dental arch can be aimed for.

[0117] This method further includes a display step S5 of displaying, as shown in FIG. 6B (horizontal plane), the axial slices of the reconstructed 3D volume (CBCT slices of the patient's first craniofacial region of interest ROI1) on the display assembly 48 of FIG. 2. If necessary, additional views, such as a sagittal suture view, can also be displayed.

[0118] This method further includes a step S6 of at least partially defining a second region of interest ROI2 based on the reconstructed and displayed axial CBCT slices of the patient's first craniofacial region of interest ROI1.

[0119] The second region of interest ROI2 is defined or selected to intersect the first region of interest ROI1 within the xy plane of the axial slice.

[0120] The second region of interest ROI2 is defined or selected by the practitioner via the user interface assembly or the graphical user interface 50. For example, the practitioner can select the display of a set of menus or icons via activation of a user input tool such as a mouse click, and further select an icon that can be moved to a desired position on the displayed slice by moving the mouse cursor. In this embodiment, since the second volume of data to be acquired later is cylindrical, the icon is here represented by the circle C on FIG. 6B. The circle appearing in this view has the dimensions of the second volume of data to be acquired.

[0121] Furthermore, the second volume of data to be acquired later can take on another shape, and the landmarks or icons that assist in the definition of ROI2 can take on another shape that matches it.

[0122] Returning to FIG. 6B, the position and size of the circle on the displayed axial slice define the second region of interest ROI2 that intersects the first region of interest ROI1 within the xy plane of this figure.

[0123] In FIG. 6B, the circle (ROI2) is positioned within a part of a group of teeth.

[0124] As shown, the position of ROI2 can be adjusted according to the x and y coordinates within the plane of FIG. 6B so as to define a desired position according to the needs of the practitioner (see step S6.1) (see the corresponding up, down, left, and right arrows). Specifically, he / she may need to focus on one tooth or a group of teeth for more accurate data acquisition.

[0125] Note that the size of the circle (here its diameter) can be adjusted if necessary to enlarge or reduce the size of the defined second region of interest ROI2. The size can be changed, for example, by scrolling the mouse wheel. The size of the circle can be changed by selecting a value from a set of predetermined values.

[0126] The size and / or position adjustment described above for ROI2 can be viewed in real time by the practitioner on the display, which allows for further adjustment of the size and / or position if necessary.

[0127] All of the above described for the circle and the mouse equally applies to the operation of other displayed landmarks and user input tools, and both landmarks and user input tools for defining a second region of interest.

[0128] In step S6.2, the position of ROI2 can also be defined or adjusted along the axis z perpendicular to the xy plane of FIG. 6B in order to finish defining the desired position of the second volume of data according to the needs of the practitioner.

[0129] The z-axis position or height of ROI2 (field of view or FOV) can be defined or adjusted based on the transverse scout view. The transverse scout view can advantageously be the transverse scout view (LSV) shown in FIG. 5, which was used in step S2 above to determine the height of the horizontal plane of interest.

[0130] The transverse scout view LSV provides the practitioner with additional morphological information, such as a display of the position and geometry of the teeth in the vertical plane (yz plane). This can help the practitioner to further define the position of ROI2 relative to the craniofacial region, specifically with respect to the z-axis position. Furthermore, the y-axis position of ROI2 can also be better defined or adjusted thanks to the transverse scout view LSV.

[0131] The height or size of ROI2 can be set to a predetermined value and can be changed upon a command by the practitioner to increase or decrease the second volume of the acquired data. The same process as described above for the size of circle C (e.g., the diameter of the circle) can also be applied here to the change in the z-axis position. Note that the practitioner can move back and forth between the view of FIG. 5 and the view of FIG. 6B to manually adjust the x-axis position, y-axis position, and / or z-axis position, and / or the size of ROI2.

[0132] The height or size of ROI2 can be changed by selecting a value from a set of predetermined values.

[0133] In this embodiment, as already described above, the second volume of the acquired data can take the shape of a cylinder whose dimensions can be changed according to the needs of the practitioner.

[0134] Note that the definition of the geometric position of ROI2 sets the position of the center of ROI2.

[0135] Above, it was explained how the z-axis position or height of ROI2 should be defined or adjusted based on the transverse scout view.

[0136] However, more generally, the z-axis position or height of ROI2 can be defined or adjusted based on the determination of the height of the horizontal plane of interest, as described in step S2 above. Specifically, as described in steps S2.3 and S2.4 above, processes other than the transverse scout view, such as the acquisition of optical images or the execution of physical measurements, can be used.

[0137] In an alternative, the z-axis position or height of ROI2 can be defined or adjusted independently of the determination of the height of the plane of interest, as described in step S2 above. The z-axis position or height of ROI2 can be defined or adjusted based on one of the following executed to achieve this goal. - Obtaining a lateral x-ray scout view including the patient's first craniofacial region of interest (ROI1), - Obtaining an optical image including the patient's first craniofacial region of interest (ROI1) including landmarks, - Performing a physical measurement on the patient's first craniofacial region of interest (ROI1) using a patient positioning device.

[0138] The above steps are the same as those described above with respect to steps S2.1, S2.2, S2.3, and S2.4. However, in this alternative embodiment method, the same steps can be performed twice, once for determining the height of the plane of interest and once for defining the z-axis position of ROI2.

[0139] As a variant embodiment, the step of defining or adjusting the z-axis position of ROI2 can be made different from that performed in step S2. For example, step S2 was performed without using a lateral scout view, but a lateral scout view is obtained for use in defining or adjusting the z-axis position of ROI2.

[0140] Note that the height size of ROI2 may extend beyond the height of the CBCT slice (here it is rather thin, for example, about 1 to 15 mm, preferably 1 to 5 mm).

[0141] This method further includes at least step S7 of obtaining operation parameters based on ROI2 defined as such.

[0142] As can be seen above, ROI2 is defined by its x, y, z spatial coordinates that set the spatial or geometric position and size of the center of ROI2. This information on the position and size of ROI2 was thus obtained precisely based on the patient's data, not the averaged patient data. Therefore, this enables the practitioner to adjust the trajectories of both the x-ray source and the x-sensor to obtain a 3D volume (a second set of data including ROI2) based on the position and size of ROI2 thereafter. Note that the trajectory can be based only on the position of ROI2. Both the x-ray source and the x-sensor are operable to move simultaneously around the patient's head along this trajectory. Preferably, the 3D volume corresponds to the volume of data of ROI2. However, other configurations can be considered.

[0143] Through this adjustment, the position of the center of rotation of the set of the x-ray source and the x-sensor can be changed according to the target anatomical structure (e.g., ROI2).

[0144] Examples of possible trajectories of both the x-ray source 18 and the x-sensor 20 are shown in FIG. 7, in which the following notations are used. C Center of rotation of the gantry N Patient dose SP Sagittal plane of the patient T Trajectory followed by the center C V 3D volume reconstructed / acquired through tracing the trajectory T

[0145] In general form, the position and size of ROI2 and the shape of ROI2, which is cylindrical in the example embodiment here, are operating parameters.

[0146] If the 3D volume acquired later does not correspond to ROI2, the operating parameters used during this subsequent acquisition may be different from the above.

[0147] The obtained operating parameters enable determining a plurality of trajectories each of which enables obtaining a desired 3D volume.

[0148] The operation parameters or acquisition parameters obtained in step S7 can then be stored while waiting to be used.

[0149] All operation parameters are obtained based on a defined ROI2 that accurately represents the area of interest of the practitioner without unnecessary details (optimization of the position of the ROI or 3D volume to be acquired later). Thus, the operation parameters obtained are adjusted to the specific needs of the practitioner, minimizing the area of the patient exposed to x-rays as well as the x-ray dose used.

[0150] A few steps (other than the manual steps S1 and S6) can be automatically executed by the control assembly 44 of FIG. 2 in the method of the embodiment of FIG. 3.

[0151] The operation parameters or acquisition parameters obtained in step S7 can be used during a subsequent step S8 of acquiring a second set of data regarding the craniofacial second area of interest (ROI2) of the patient using a second x-ray dose. This second set of data acquired corresponds to the above-mentioned 3D volume of data.

[0152] This acquisition step is performed using an x-ray CBCT imaging device that is not necessarily the device 10. This acquisition step can be temporally separated from the first steps S1 to S7, for example, by several hours, days, months, etc. It is assumed that the craniofacial area of the patient has not changed between the two acquisitions.

[0153] Here, method step S8 includes previous patient positioning steps (see steps S2 and S3 above) before acquiring a second set of data using different recorded or stored setting parameters that define the patient's first position. This previous step prepares to adjust the setting parameters of the x-ray CBCT imaging device, specifically the patient positioning device or patient positioning accessory used in step S3, such that the patient will be positioned at or near the same first position in view of this second data acquisition.

[0154] The obtained motion parameters or acquisition parameters (e.g., trajectory, x-ray dose, etc.) are then used in step S8 to adjust or set the x-ray CBCT imaging device in view of acquiring a 3D volume of data that includes ROI2 relative to the patient's craniofacial region.

[0155] The x-ray dose used for this second data acquisition is higher than the first x-ray dose that generates slices, and the first x-ray dose is 20% or less, preferably 10% or less, more preferably 5% or less of the second x-ray dose.

[0156] For example, the first x-ray dose is 4 μSv and the second x-ray dose is - 200 μSv for a 3D examination with a large field of view (17×13 cm), - 20 μSv for a 3D examination with a 5×5 cm field of view is.

[0157] For example, the duration of the x-ray exposure for the second data acquisition is between 5 seconds and 20 seconds for a 3D examination compared to a duration of about 5 seconds for the first data acquisition.

[0158] For example, the resolution of the image(s) obtained via the second data acquisition is defined by a 100 μm voxel size for a 3D examination compared to a 500 μm voxel size for the first data acquisition.

[0159] Although the present invention has been described in detail and may have been described with specific reference to appropriate or presently preferred embodiments, it should be understood that variations and modifications can be made within the spirit and scope of the invention. Accordingly, the presently disclosed embodiments are considered to be illustrative in all respects and not restrictive. The scope of the invention is indicated by the appended claims, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced within the scope of the appended claims.

Claims

1. A method for obtaining operating parameters of an x-ray CBCT imaging device in consideration of obtaining a set of data of a patient's craniofacial region, the method comprising: - identifying a first region of interest (ROI1) in the patient's craniofacial region; - determining the height of a horizontal plane of the first region of interest (ROI1) in the patient's craniofacial region when the patient is in an occlusion position or when the patient positioning assembly is bitten; - using x-ray CBCT imaging to obtain a first set of relative data for the first region of interest (ROI1) in the patient's craniofacial region, including the horizontal plane, through a slit-shaped collimator window; - reconstructing an axial CBCT slice including the horizontal plane based on the first set of relative data for the first region of interest (ROI1) in the patient's craniofacial region; - displaying the reconstructed axial CBCT slice of the first region of interest (ROI1) in the patient's craniofacial region from the first set of acquired data; - at least partially defining a second region of interest (ROI2) to intersect the first region of interest (ROI1) in the patient's craniofacial region within the plane of the displayed and reconstructed axial CBCT slice of the first region of interest (ROI1) in the patient's craniofacial region; - obtaining operating parameters of the x-ray CBCT imaging device based at least on the defined second region of interest (ROI2), considering obtaining a second set of data including the defined second region of interest (ROI2); A method comprising the above steps.

2. The method according to claim 1, wherein at least partially defining the second region of interest (ROI2) based on the displayed and reconstructed axial CBCT slice of the first region of interest (ROI1) in the patient's craniofacial region includes defining the position of the second region of interest (ROI2) in the xy plane of the axial slice.

3. The method according to claim 2, wherein defining the second region of interest (ROI2) further includes defining the position (height) of the second region of interest (ROI2) along the z-axis perpendicular to the xy plane of the axial slice.

4. Defining the z-axis position of the second region of interest (ROI2) is preceded by: - obtaining a transverse x-ray scout view including the first region of interest (ROI1) in the patient's craniofacial region; - obtaining an optical image including the first region of interest (ROI1) in the patient's craniofacial region and including landmarks; - performing a physical measurement on the first craniofacial region of interest (ROI1) of the patient using a patient positioning device; The method according to claim 3, comprising one of the following.

5. The method according to claim 4, further comprising adjusting the height of the second region of interest (ROI2) based on the lateral scout view, the optical image, or the performed physical measurement.

6. The method according to claim 3, wherein the z-axis position of the second region of interest (ROI2) is determined in advance.

7. The method according to any one of claims 1 to 3, wherein the second region of interest (ROI2) has a size selected from a set of predetermined values.

8. Defining the z-axis position of the second region of interest (ROI2) is based on determining the height of the horizontal plane of the first craniofacial region of interest (ROI1) of the patient when the patient is in the occlusion position or biting a patient positioning accessory. The method according to any one of claims 3 to 5.

9. Determining the height of the horizontal plane of the first craniofacial region of interest (ROI1) of the patient when the patient is in the occlusion position or biting a patient positioning accessory is performed in advance by: - obtaining a lateral x-ray scout view including the first craniofacial region of interest (ROI1) of the patient; - obtaining an optical image including the first craniofacial region of interest (ROI1) of the patient, including landmarks; - performing a physical measurement on the first craniofacial region of interest (ROI1) of the patient using a patient positioning device; The method according to any one of claims 1 to 8, comprising one of the following.

10. The first set of data is obtained while the patient is maintained in a first position via a patient positioning device, and the first patient position is defined by a set of setting parameters of the patient positioning device. The method according to any one of claims 1 to 9.

11. The method according to claim 10, including a previous adjustment of the setting parameters of the patient positioning device before obtaining the second set of data.

12. The method according to any one of claims 1 to 11, wherein the first set of data and the second set of data are separated over time.

13. The x-ray CBCT imaging device includes an x-ray source and an x-ray sensor both operable to move simultaneously around a patient's head along a predetermined locus, and obtaining the operating parameters of the x-ray CBCT imaging device based on the defined second region of interest (ROI2) includes adjusting the loci of both the x-ray source and the x-ray sensor based on the defined second region of interest (ROI2). The method according to any one of claims 1 to 12.

14. A system for obtaining operating parameters for x-ray CBCT imaging of a patient's craniofacial region, the system comprising: - An x-ray source and at least one x-ray sensor configured to move around the craniofacial first region of interest (ROI1) of the patient while irradiating the craniofacial first region of interest (ROI1) of the patient with a slit-shaped x-ray beam to obtain a first set of relative data for the craniofacial first region of interest (ROI1) of the patient when the patient is in an occlusion position or biting a patient positioning accessory, wherein the craniofacial first region of interest (ROI1) of the patient includes a horizontal plane, the x-ray source and at least one x-ray sensor; - A microprocessor, Identifying the craniofacial first region of interest (ROI1) of the patient; Determining the height of the horizontal plane of the craniofacial first region of interest (ROI1) of the patient when the patient is in an occlusion position or biting a patient positioning assembly; Reconstructing an axial CBCT slice including the horizontal plane based on a first set of relative data for the craniofacial first region of interest (ROI1) of the patient; Displaying the reconstructed axial CBCT slice of the craniofacial first region of interest (ROI1) of the patient from the first set of acquired data using a view for at least partially defining a second region of interest (ROI2) so as to intersect the craniofacial first region of interest (ROI1) of the patient within the plane of the displayed and reconstructed axial CBCT slice; Obtaining the operating parameters of the x-ray CBCT imaging device based on at least the defined second region of interest (ROI2), taking into account the acquisition of a second set of data including the defined second region of interest (ROI2); A microprocessor configured to perform the above; A system comprising.

15. A computer storage medium storing therein instructions for causing a computer or a microprocessor to execute the method according to any one of claims 1 to 13.

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