Method and system for obtaining operating parameters for 3D X-ray acquisition - Patents.com

Abstract

A method is provided for obtaining operating parameters of an x-ray CBCT imaging device in light of the acquisition of a data set of a patient's maxillofacial region. [Solution] The method includes identifying a first maxillofacial region of interest (ROI1) on a patient, determining the height of the horizontal plane of ROI1 when the patient is in an occlusal position or biting a patient positioning assembly, acquiring a first set of data relative to ROI1 using x-ray CBCT imaging, reconstructing axial CBCT slices based on the first set, displaying the reconstructed axial CBCT slices of ROI1 from the acquired first set of data, defining a second region of interest (ROI2) based on the intersection of the displayed reconstructed axial CBCT slices of ROI1 with ROI1, and obtaining operating parameters based on ROI2 in consideration of acquiring a second set of data including ROI2.

Description

[Technical field]

[0001] The present disclosure relates generally to the field of dental x-ray imaging, and more particularly to the field of x-ray Cone Beam Computed Tomography (CBCT) imaging. More particularly, 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 for x-ray CBCT imaging of a patient's maxillofacial region. [Background technology]

[0002] Conventional methods and systems for obtaining x-ray images of a patient's maxillofacial region via x-ray CBCT imaging very often require irradiating a localized area of ​​reduced size relative to the size of the patient's entire maxillofacial region with an x-ray dose for a certain exposure time in order to obtain details about teeth, specific areas, etc. that are important to the practitioner.

[0003] Predefined device settings corresponding to the average patient make it possible to reach the desired localized area.

[0004] However, variations between patients with respect to the average predefined settings may result in re-imaging, which may lead to an increase in the x-ray dose received by the patient.

[0005] While such systems may have achieved some success in their particular applications, there remains a need for improvements to these methods and systems. Summary of the Invention

[0006] An object of the present disclosure is to avoid unnecessary x-ray dose to patients when undergoing x-ray CBCT examinations.

[0007] Another object of the present disclosure is to improve positioning accuracy of a patient data volume acquired via x-ray CBCT data acquisition while limiting patient dose exposure.

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

[0009] These objectives are given only as illustrative examples, and such objectives may be exemplary of one or more embodiments of the invention. Other desirable objectives and advantages inherently attainable 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, there is provided 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 a patient; - determining the height of a horizontal plane of a first maxillofacial region of interest ROI1 of said patient when said patient is in an occlusal position or bites a patient positioning assembly; acquiring, using x-ray CBCT imaging, through a slit-shaped collimator window, a first set of data relative to a first region of interest (ROI1) of said patient's maxillofacial region comprising a horizontal plane; - reconstructing axial CBCT slices including a horizontal plane based on a first set of data relative to a first maxillofacial region of interest ROI1 of the patient; - displaying reconstructed axial CBCT slices of a first maxillofacial region of interest ROI1 of the patient from the acquired first set of data; - defining a second region of interest ROI2 at least in part based on the displayed reconstructed axial CBCT slices of the patient's maxillofacial first region of interest ROI1 and its intersection with the ROI1; - obtaining operating parameters of the x-ray CBCT imaging device based on at least 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; A method is provided that includes:

[0011] The method according to an embodiment of the present invention is a novel method that allows for reducing patient exposure to x-rays.

[0012] A method according to one embodiment of the present invention is a novel method that uses a first x-ray "pre-fire" having an x-ray dose to acquire and reconstruct a CBCT slice that includes a patient's maxillofacial first region of interest ROI1, allowing the practitioner to select or define a more specific area or region of interest. This definition or selection of the more specific area or region of interest allows for the acquisition of adapted operating or acquisition parameters that are used for another "fire" or second x-ray CBCT data acquisition.

[0013] Typically, a low dose is used for "pre-fire". Low is a dose that is not more than 20%, preferably less than 10%, more preferably less than 5% of the default or standard dose (obtained with default or standard parameters) used for a known x-ray examination (3D, panoramic, etc.). Low doses can be used because the CBCT slices do not require as many details as the default or conventional acquisitions, and the patient should not be overexposed to x-rays. However, the CBCT slice information must be sufficient to provide morphological information (e.g., tooth position, tooth geometry, etc.) that allows the selection of more specific areas or regions of interest by the practitioner. The information contained in the CBCT slices is specific to the patient. Thus, the use of such information allows a more adapted and / or more accurate definition of the more specific areas or regions of interest. This form of processing is obviously not based on averaged patient data as in the past. Thus, the operating or acquisition parameters obtained based on such more specific areas or regions of interest of the patient are more reliable and accurate, since they represent the patient. The CBCT slice can be a thin slice that includes the ROI 1. The slice can be less than 100 μm thick or tall, or it can be an integrated slice over some thickness or height, typically around 2-3 mm.

[0014] The patient is preferably in a repeatable position during the "pre-fire", by which is meant that the patient will be in the same position or a very similar position for subsequent "fires" or acquisitions using the obtained parameters. In this regard, the x-ray machine setting parameters for positioning the patient are held in memory.

[0015] According to a possible feature or aspect, - at least partially defining a second region of interest ROI2 based on a displayed reconstructed axial CBCT slice of a first region of interest ROI1 of the maxillofacial region of the patient, comprising defining a position of the second region of interest ROI2 in an xy-plane of the axial slice; - defining the second region of interest ROI2 further comprises defining a position (height) of the second region of interest ROI2 along a z-axis perpendicular to the xy-plane of the axial slice; The z-axis position of the second region of interest ROI2 is defined in advance by: acquiring a lateral x-ray scout view including a maxillofacial first region of interest (ROI1) of the patient, the scout view being used to locate both the horizontal height of ROI1 and the height and size in the yz plane of ROI2; acquiring an optical image including a first region of interest ROI1 of the patient's maxillofacial region including landmarks; performing physical measurements on a patient's maxillofacial first region of interest (ROI1) using a patient positioning device; one of the following: the method further comprises adjusting a height of the second region of interest (ROI2) based on a lateral scout view, an optical image, or a performed physical measurement; the z-axis position of the second region of interest ROI2 is previously determined; the second region of interest ROI2 has a size selected among a set of predetermined values, - defining a z-axis position of a second region of interest ROI2 based on determining a height of a horizontal plane of a first region of interest ROI1 of said patient's maxillofacial surface when said patient is in an occlusal position or biting a patient positioning accessory, Determining the height of the horizontal plane of the first region of interest ROI1 of the maxillofacial surface of the patient when the patient is in an occlusal position or bites a patient positioning accessory may include, in advance, acquiring a lateral x-ray scout view including a maxillofacial first region of interest (ROI1) of the patient; acquiring an optical image including a first region of interest ROI1 of the patient's maxillofacial region including landmarks; performing physical measurements on a patient's maxillofacial first region of interest (ROI1) using a patient positioning device; one of the following: - a first set of data is acquired while the patient is maintained in 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 including prior to acquisition of the second set of data, adjusting setting parameters of the patient positioning device; - the first set of data and the second set of data are separated over time; -The x-ray CBCT imaging device includes an x-ray source and an x-ray sensor both operable to move simultaneously around the patient's head along a predetermined trajectory, and obtaining operating parameters of the x-ray CBCT imaging device based on the 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, there is provided a system for obtaining operational parameters for x-ray CBCT imaging of a maxillofacial region of a patient, the system comprising: - an x-ray source and at least one x-ray sensor configured to move around a patient's maxillofacial first region of interest ROI1 while irradiating the patient's maxillofacial first region of interest ROI1 with a slit-shaped x-ray beam in order to obtain a first set of data relative to said patient's maxillofacial first region of interest ROI1 when said patient is in an occlusal position or biting a patient positioning accessory, said patient's maxillofacial first region of interest ROI1 including a horizontal plane of the patient in an occlusal position or a plane parallel thereto; - reconstructing axial CBCT slices including an occlusal plane or a plane parallel thereto based on a first set of data relative to a first maxillofacial region of interest ROI1 of the patient; displaying reconstructed axial CBCT slices of the patient's maxillofacial first region of interest ROI1 from the acquired first set of data using a view for at least partially defining a second region of interest ROI2 based on the displayed reconstructed axial CBCT slices and an intersection with the latter; Obtaining operating parameters of the x-ray CBCT imaging device based on at least the second defined region of interest ROI2 in consideration of acquiring a second set of data including the second defined region of interest ROI2. A processor configured as A system is provided comprising:

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

[0018] According to another aspect of the present disclosure, there is provided a computer storage medium having stored therein instructions for causing a computer or microprocessor to carry out the method briefly described above. [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 that are illustrated in the accompanying drawings.

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

[0021] [Figure 1] 1 is an overall schematic perspective view showing an x-ray CBCT imaging apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 1 illustrates the major functional components or assemblies of an x-ray CBCT imaging system in accordance with an embodiment of the present invention. [Diagram 3] FIG. 4 illustrates an algorithm of a method according to an embodiment of the present invention. [Figure 4] 4A to 4C show different processes for carrying out step S1 of FIG. 3. [Diagram 5] Figure 3 shows possible positions of ROI1 and ROI2 in the yz plane on the lateral scout view. [Figure 6A] FIG. 13 shows possible relative positions between ROI1 and the x-ray source. [Figure 6B]FIG. 13 shows an axial view of the reconstructed CBCT slice for ROI2. [Figure 7] FIG. 13 shows example trajectories for both the x-ray source and the x-ray sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Following is a detailed description of the preferred embodiments, reference is made to the drawings in which like reference numerals identify like elements of structure in each of the several drawings.

[0023] 1 illustrates an embodiment of an x-ray imaging device, specifically an extraoral imaging device 10. The device 10 includes a support structure that includes a support frame 12, which may be a column.

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

[0025] More specifically, the horizontal mount 14 is fixedly mounted to a vertical portion 12a which is slidably mounted to a fixed vertical portion 12b. For example, an actuator (not shown in this view), e.g., of an electrical type, located behind the vertical column, can be commanded to drive the horizontal mount 14 in a controlled vertical movement.

[0026] The horizontal mount 14 can support a gantry 16. The gantry 16 can be movable relative to the support structure, more specifically relative to the horizontal mount 14. The gantry 16 can be rotatable relative to the horizontal mount 14. The gantry 16 can be stationary during the operation of the imaging process or can be rotatable about a vertical axis of rotation that can follow one of a number of predefined trajectories according to the 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 driving mechanism includes a motor, such as two stepper motors, for example, that provides a first movement in the xy plane, and a motor, such as a brushless motor, that provides a rotational movement about a vertical axis z.

[0027] The gantry 16 supports both an x-ray source 18 and at least one x-ray sensor 20 disposed corresponding to the x-ray source. The x-ray source 18 and the at least one x-ray sensor 20 may be disposed facing one another. The gantry 16 may include two opposing downwardly extending arms, a first arm 16a that supports the x-ray source 18 attached thereto and a second opposing arm 16b that supports the 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 a vertical axis z and the opening of the slit-collimator window can be adjusted such that the collimated x-ray beam irradiates a region of interest on the patient's head or the patient's maxillofacial region.

[0029] When activated, the x-ray source 18 emits an x-ray beam which here irradiates an imaging area of ​​the patient's maxillofacial region (or the patient's maxillofacial region of interest) before impinging on 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 patient's maxillofacial region along a predetermined trajectory while irradiating an imaging area of ​​the patient's maxillofacial region.

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

[0032] However, the apparatus 10 may also function according to one or more other operating modes or imaging processes, such as panoramic, cephalometric, etc.

[0033] The device 10 may also operate according to such different operating modes or only some of these operating modes.

[0034] In this regard, a different sensor or other sensors can be used and the x-rays can be collimated accordingly to irradiate an area of ​​the patient's head as the patient's maxillofacial area of ​​interest having a particular shape (or the patient's entire head) depending on the selected operating mode and the practitioner's preferences.

[0035] The at least one x-ray sensor 20 comprises a sensor adapted for one of the operating modes of the device, for example this sensor can be a sensor adapted to perform a CBCT scan, for example a volumetric sensor or a computerized sensor (for example rectangular, square shape), or a plurality of sensors of the previous type.

[0036] The support structure may also include a patient positioning accessory support member 22, here an arm. The arm 22 is connected to the support frame, more specifically to the vertical post 12. The patient positioning arm 22 is movable relative to the support frame. More specifically, the arm 22 can slide along the vertical post 12 to move up and down when commanded via a suitable actuator(s), for example of the electrical type. The patient positioning arm 22 extends from an arm support 22a that is slidably mounted relative to the fixed vertical part 12b. The patient positioning arm 22 extends along the apparatus in a direction that substantially corresponds to the direction of extension of the horizontal mount 14. The patient positioning arm 22 is here arranged transversely to the apparatus in a substantially parallel relationship with the horizontal mount 14.

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

[0038] The patient positioning arm 22 may include one of a number of patient positioning accessories disposed generally at or adjacent the free end 22b of the arm, which may also or instead be considered a support system.

[0039] These patient positioning accessories make it possible to position the anatomical structures of the patient's head according to different orientations and to fixate the patient's head during the examination in order to reduce any possible movements.

[0040] There are one or more types of patient positioning accessories for each type of specific exam performed by the device according to different modes of operation, and arm 22 is configured to accommodate each of these different types of patient positioning accessories, typically one at a time.

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

[0042] The patient positioning accessory 24 may also include a chin rest 26 extending upwardly from the arm 22 to which it is removably attached. The chin rest 26 is placed between the two temporary retainers to position the patient's head for the panoramic exam. A standard bite block may be further added to the chin rest. Alternatively, a Frankfort guide bite block may be used for the panoramic exam.

[0043] Other possible types of patient support accessories can be considered: nose supports for performing open and closed mouth temporal temporomandibular joint examinations, bite supports for 3D examinations (bridle type), forehead supports for 3D examinations (forehead type), combined bite and forehead supports, etc.

[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 serve to set the patient's position and the reproducibility of this position in future with respect to structural data acquisition. The setting parameters defining the patient's position (including the relative position with respect to the seat) can be stored in memory even if subsequent data acquisitions are not performed on the same device.

[0045] 1, a handle assembly 34 can be positioned beneath and in parallel relationship with the arm at the free end 22b of the arm. The handle assembly 34 includes two perpendicular, separate handle portions 34a, 34b that can be grasped by the patient while undergoing the imaging process in order to remain stationary.

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

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

[0048] The patient positioning arm 22 may also support a monitor or display assembly 36 that allows a practitioner of the device to view and interact with images displayed thereon and to operate certain functions of the device.

[0049] 2 is a schematic diagram of the major 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] System 40 includes an acquisition assembly 42 that includes the x-ray source and x-ray sensor of the apparatus of FIG.

[0052] The system 40 includes a control assembly 44 coupled to the acquisition assembly 42 and configured to control operation of the acquisition assembly 42 in accordance with an embodiment method of the present invention.

[0053] The control assembly 44 may also be used to enable operation of the apparatus 10 and its various components / assemblies in a more conventional manner, in particular to perform CBCT scans, reconstruct 3D volumes (3D x-ray image data), perform panoramic, cephalometric, etc. data acquisition.

[0054] The control assembly 44 specifically includes a processor and, possibly, one or more storage media storing a computer program having instructions for controlling the system 40 to practice one or more embodiment methods 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 perform steps or operations of the embodiment methods according to the present invention.

[0055] One aspect of the present invention is also directed to a computer program product that includes one or more storage media.

[0056] The one or more storage media may be, for example, a magnetic storage medium, such as a magnetic disk (such as a floppy disk) or a magnetic tape; an optical storage medium, such as an optical disk, an optical tape, or a machine-readable bar code; a solid-state electronic storage device, such as a random access memory (RAM) or a read-only memory (ROM); or any other physical device or medium used to store such computer programs.

[0057] The stored computer program(s) or other stored computer program(s) may also have instructions to control the apparatus 10 to perform more conventional methods, such as conventional methods of obtaining a 3D volume.

[0058] The system 40 may also include one or more external storage media 46 for storing different volumes of data reconstructed by the device during an x-ray imaging process, here e.g. a CBCT imaging process. The one or more external storage media 46 may be of the same type as described above.

[0059] One or more external storage media 46 may also store, in place of one or more storage media specific to the control assembly 44, the computer program(s) described above for controlling the system 40 and / or, more generally, for controlling the apparatus 10.

[0060] System 40 further includes a display assembly 48, here one or more monitors or screens, which may correspond to display assembly 36 of Figure 1. Display assembly 48 is connected to control assembly 44.

[0061] The display assembly 48 is capable of automatically or on demand displaying selected images of the patient's maxillofacial region obtained from an x-ray CBCT imaging process performed by the apparatus 10 .

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

[0063] The system 40 may further include a user interface assembly 50 connected to the display assembly 48 and the control assembly 44. The user interface assembly 50 allows a user, such as a medical practitioner or technician, to interact with the display assembly 48 and the control assembly 44, possibly executing image processing / algorithms, to perform various tasks.

[0064] The user interface assembly 50 may include one or more interaction devices connected to the display assembly 48, such as, but not limited to, a pointing device, e.g., a computer mouse joystick, a stylet, a keypad, a touchpad, etc.

[0065] Other types of interaction devices or tools (user interface tools), such as a touch screen, tool icons that are displayed on the screen or that may be displayed upon command, may be used instead or in addition.

[0066] Assemblies 44, 46, 48, and 50 may be located, in whole or in part, within arm 22 of device 10 or may be located remotely relative to the device (e.g., within the same room or a different room or at another location). If control assembly 44 is not located within device 10, then a separate control assembly may be present within the device for controlling acquisition assembly 42 and for controlling the operation of the device in a general manner. However, this entire description applies equally regardless of the location of the assemblies.

[0067] The above is also true if the assemblies 42, 44, 46, 48, and 50 relate to other x-ray imaging devices.

[0068] An embodiment method according to the invention will now be described with reference to Fig. 3 which shows an algorithm of the corresponding computer program(s) which makes reference to other algorithms which are shown in other figures and which may be part of the same computer program or which may correspond to other computer programs.

[0069] In its operation, the embodiment method makes use of functional components or assemblies that may be those described above in relation to the apparatus 10 of Figure 1 and Figure 2. Alternatively, the functional components or assemblies required to carry out the method may be those of another x-ray imaging device, but these may conform to the configuration of Figure 2 (although not all components of Figure 2 need to be present).

[0070] A patient is first positioned, for example in a sitting position, in the workspace of the apparatus 10 between the x-ray source 18 and the x-ray sensor 20 of the acquisition assembly 42. The method starts with an identification step S1 in which a first maxillofacial region of interest of the patient is identified, denoted ROI 1. The practitioner identifies ROI 1 based on predefined criteria such as the type of examination to be performed on a second region of interest ROI2 of the patient's maxillofacial region, the second region of interest ROI2 itself, etc.

[0071] For example, ROI1 may include the upper and lower jaws, portions of both jaws, only one jaw, portions of a single jaw, etc., depending on the practitioner's interests.

[0072] The method further comprises a height determination step S2. For the execution of this step, the patient bites in the patient positioning member or patient positioning accessory and his / her teeth are then separated by 2-3 millimeters. Such a patient positioning member or patient positioning accessory can be releasably attached to the arm 22. Such a patient positioning member or patient positioning accessory can be a bite block, e.g. a Frankfurt guide bite block used for panoramic examinations, a standard bite block, a bitten 3D support, etc.

[0073] Figure 5 shows an ROI1 identified / selected by the practitioner on a previously acquired lateral scout view LSV (simply a projection of data acquired via lateral x-ray data acquisition) of the patient's maxillofacial region. In Figure 5, the patient's face is also shown as 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] Alternatively, the patient may be in an occlusal position, i.e., his / her upper and lower jaws are in contact with each other. His / her head may be maintained in position via a chin rest, a forehead support including a 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 in the first x-ray data acquisition, which is described below.

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

[0078] For performance of this step, the patient may be positioned so that his / her Camper's plane is horizontal.

[0079] FIG. 4 shows different ways of determining the height of a horizontal surface.

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

[0081] FIG. 5 already mentioned above shows diagrammatically a conventionally acquired x-ray lateral scout view of a patient. Such a view here shows the patient's maxillofacial first region of interest ROI1 discussed above, identified by the practitioner, providing information on the position of the upper and lower jaws. ROI1 here shows the upper part of the patient's lower jaw and extends towards the back of the patient's head. However, the extent of ROI1 can be shorter along the y-axis. Alternatively, ROI1 can be differently positioned by the practitioner relative to the jaw, and its extent can be shorter or not along the y-axis.

[0082] The critical horizontal plane of ROI1 can be positioned by the practitioner on the display or determined by calculation. The horizontal plane can be the median plane of ROI1, as already mentioned above.

[0083] Then, in step S2.2, the height of this horizontal plane is conventionally determined based on the known position of the scout view relative to the patient positioning accessory used (here a bite block) 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. Note that the position of the x-ray source relative to the arm is also known.

[0084] FIG. 5 illustrates, by a line designated L, the z-axis location of the horizontal plane mentioned above.

[0085] Two other ways of determining the height of a horizontal surface are shown in FIG.

[0086] The second form (step S2.3) prepares to acquire at least one optical image of the patient (in a biting or occlusal position) including the patient's maxillofacial first region of interest ROI1 including landmarks. The at least one image is more specifically a face image taken by a camera, the landmarks can be of anatomical type (e.g. landmarks at the corners of the mouth or landmarks 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 FIG. 1 an example of a camera 52 is placed next to the x-ray source 18. Alternatively or additionally another position of the camera can be chosen.

[0087] Alternatively, a lateral optical image of the patient may be more convenient than a forehead image.

[0088] The landmark or landmarks are representative of geometric locations that are known or can be easily known by calculation relative to the root of the tooth.

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

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

[0091] A patient positioning accessory, such as a bite block or similar, attached to the arm 22 in Figure 1 can be used. The bite block is attached to the arm in a fixed position and the height of the bite block relative to the arm is known or can be measured. The average size (height) of the teeth for a given patient (adult, infant, etc.) is also known and this allows the location of the tooth roots and therefore the tooth tips i.e. the root position relative to the bite block to be determined.

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

[0093] Alternatively, sensors placed in a bite block or similar can provide suitable measurement data from which the height or position of the occlusal plane relative to the arm can then be determined.

[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 at determining the height at which the first set of data for ROI1 is acquired.

[0095] After the elevation of the horizontal plane has been determined, the apparatus 10 is set by the control assembly 44 in a configuration that enables acquisition of a first set of data relative to the ROI1 provided by step S3 of Figure 3. The first set of data may correspond to the entire ROI1 or a selected portion thereof.

[0096] First, the set of x-ray source and x-ray sensor is commanded by the control assembly 44 to move to a determined height so that the x-ray source is at a suitable height for acquisition; this arrangement allows for a simple reduction in x-ray dose; Second, the x-ray source remains at the same elevation and the x-ray collimator is moved to orient the x-ray beam upward toward the determined elevation of the plane. These two forms are used to set the device in the acquisition configuration.

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

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

[0099] The different setting parameters defining the first position of the patient, such as the accessory used, the position of this accessory on the device if multiple position settings are available (e.g. different possible heights of the support), the accessory position relative to the patient (e.g. if multiple width values ​​are possible according to the patient's face width), this parameter if the possible seat heights are adjustable, etc., may be recorded or stored by the practitioner (e.g. in a storage medium via the user interface assembly) along with a view to be used again for subsequent data acquisition.

[0100] For this first data acquisition, the apparatus 10 is in a CBCT mode of operation 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 produce a slit-shaped x-ray beam focused on the patient's maxillofacial first region of interest (ROI1) including the horizontal plane.

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

[0103] The horizontal plane of ROI1 is targeted thanks to adjustments in the collimator position and the collimator window aperture.

[0104] FIG. 6A shows two different relative positions between the x-ray source 18 and the 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 source and sensor set is also shown. To capture and reconstruct CBCT slices, the vertical collimator aperture depends on the position of the collimator relative to the source-sensor alignment. The smallest aperture is obtained when the source-sensor axis passes through the collimator. In other words, the median plane of the collimated x-ray beam can be adjusted with respect to the collimator to obtain the smallest aperture required for slice reconstruction.

[0105] Preferentially, the source-sensor axis passes through the base of the collimator window and the bottom edge or border of ROI1.

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

[0107] The first x-ray dose is selected to minimize the x-ray exposure of the patient. The x-ray dose depends on the volume of the patient data to be acquired. The volume is preferably as small as possible for data acquisition, and does not need to be of high resolution, since the useful information required for the rest of the method resides in the morphological characteristics or data of the patient maxillofacial first region of interest (tooth positions, characteristic dimensions, etc.). Preferably, such information does not require a lot of detail in the acquired data. However, the volume is not necessarily thin, and its size depends on the image resolution. If the dose has to be low, a compromise between the size of the volume and the resolution generally needs to be made.

[0108] Typically, the first x-ray dose is no more than 20% of the second dose used in the subsequent second data acquisition.

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

[0110] For example, the first x-ray dose may be on the order of 4 μSv for the production of a CBCT slice.

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

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

[0113] The next step S4 is a reconstruction step in which CBCT slices are reconstructed based on the acquired first set of data using conventional CBCT data processing techniques (eg, FDK algorithms).

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

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

[0116] The reconstructed CBCT slices may have the shape of a cylinder (although other shapes can be used) with a diameter between 120 mm (for small skull dimensions) and 160 mm. Smaller diameters may be convenient. The CBCT slices may be limited here as thin slices. In other example embodiments, the acquisition of the entire dental arch may be aimed for.

[0117] The method further comprises a display step S5 of displaying an axial slice of the reconstructed 3D volume (a CBCT slice of the patient's maxillofacial first region of interest ROI1) as shown in Fig. 6B (horizontal plane) on the display assembly 48 of Fig. 2. If required, additional views, such as a sagittal view, can also be displayed.

[0118] The method further comprises 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 maxillofacial first region of interest ROI1.

[0119] A second region of interest ROI2 is defined or selected to intersect the first region of interest ROI1 in 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 graphical user interface 50. For example, the practitioner selects the display of a menu or set of icons via activation of a user input tool such as a mouse click and further selects an icon which can be moved to a desired position on the displayed slice thanks to a movement of the mouse cursor. Since in this embodiment the second volume of data to be acquired later is cylindrical, the icon is here represented by a circle C on Fig. 6B. The circle appearing in this view has the dimensions of the second volume of data to be acquired.

[0121] Additionally, the second volume of data acquired later may take on a different shape, and the landmarks or icons that help define ROI2 may take on a different shape to match.

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

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

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

[0125] Please note that the size of the circle (here its diameter) can be adjusted if necessary to increase or decrease the size of the second region of interest ROI2 defined. The size can be changed, for example, by scrolling the mouse wheel. The size of the circle can be changed by selecting a value within a set of predefined values.

[0126] The above described size and / or position adjustments of ROI2 can be viewed by the practitioner in real time on the display, allowing him to further adjust the size and / or position if necessary.

[0127] Everything described above with respect to the circle and mouse applies equally to other displayed landmarks and user input tools, as well as the operation of both landmarks and user input tools to define the second region of interest.

[0128] In step S6.2, the position of ROI2 may also be defined or adjusted according to an axis z perpendicular to the xy plane of FIG. 6B to complete the definition of the desired location of the second volume of data according to the practitioner's needs.

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

[0130] The lateral scout view LSV provides the practitioner with additional morphological information, such as an indication of the tooth position and its geometry in the vertical plane (yz-plane). This can help the practitioner to further define the position of ROI2 relative to the maxillofacial region, specifically with regard to its z-axis position. Furthermore, the y-axis position of ROI2 can also be better defined or adjusted thanks to the lateral scout view LSV.

[0131] The height or height size of ROI2 can be a predetermined value and can be changed upon command by the practitioner to increase or decrease the second volume of acquired data. The same process described above with respect to the size of circle C (e.g., the diameter of the circle) can be applied here to changing the z-axis position. Note that the practitioner can go back and forth between the views of Figures 5 and 6B to manually adjust the x-axis, y-axis, and / or z-axis position of ROI2 and / or its size.

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

[0133] In this embodiment, as already mentioned above, the second volume of acquired data may take the shape of a cylinder whose dimensions may be varied 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 we explained how to define or adjust the z-axis position or height of ROI2 based on the lateral scout view.

[0136] More generally, however, the z-axis location or height of ROI2 may be defined or adjusted based on a determination of the height of the horizontal plane of interest, as described above in step S2. Specifically, processes other than a lateral scout view may be used, such as acquiring optical images or taking physical measurements, as described above in steps S2.3 and S2.4.

[0137] Alternatively, the z-axis location or height of ROI2 may be defined or adjusted independently of the determination of the height of the plane of interest described above in step S2. The z-axis location or height of ROI2 may be defined or adjusted based on one of the following, which are performed to achieve this goal: acquiring a lateral x-ray scout view including a first maxillofacial region of interest (ROI1) of the patient; - acquiring an optical image including a first maxillofacial region of interest (ROI1) of the patient including landmarks; - performing physical measurements on a patient's maxillofacial first 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, but 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] In an alternative embodiment, the step of defining or adjusting the z-axis position of ROI2 may be different from that performed in step S2, for example, step S2 may be performed without using a lateral scout view, but a lateral scout view is acquired for use in defining or adjusting the z-axis position of ROI2.

[0140] Please note that the height size of the ROI2 may extend beyond the height of the CBCT slice (which here is rather thin, for example around 1-15 mm, preferably 1-5 mm).

[0141] The method further comprises at least a step S7 of obtaining operational parameters based on the ROI2 so defined.

[0142] As can be seen above, ROI2 is defined by its x, y, z spatial coordinates, which set the spatial or geometrical location and size of the center of ROI2. This location and size information of ROI2 was so precisely obtained based on the patient's data, not on averaged patient's data. This therefore allows the practitioner to adjust the trajectory of both the x-ray source and the x-sensor to subsequently acquire a 3D volume (a second set of data including ROI2) based on the location and size of ROI2. Note that the trajectory can be based only on the location 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 envisaged.

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

[0144] Examples of possible trajectories of both the x-ray source 18 and the x-sensor 20 are shown in FIG. 7, where the following notation is used: C Gantry rotation center N Patient dose Sagittal plane of SP patient T The trajectory of center C V 3D volume reconstructed / obtained via drawing a trajectory T

[0145] In general terms, the position and size of ROI2 as well as the shape of ROI2, which in the example embodiment is a cylinder, are operational parameters.

[0146] If a subsequently acquired 3D volume does not correspond to ROI2, the operating parameters used during this subsequent acquisition may differ from those described above.

[0147] The obtained motion parameters make it possible to determine multiple trajectories, each of which makes it possible to obtain the desired 3D volume.

[0148] The operational or acquisition parameters obtained in step S7 may then be stored waiting to be used.

[0149] All operating parameters are obtained based on a defined ROI2 that accurately represents the practitioner's region of interest without unnecessary details (subsequent optimization of the position of the acquired ROI or 3D volume). The operating parameters obtained are thus tailored to the specific needs of the practitioner, reducing as much as possible the area of ​​the patient exposed to x-rays as well as the x-ray dose used.

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

[0151] The operating or acquisition parameters obtained in step S7 may be used during a subsequent step S8 of acquiring a second set of data relating to and including a second maxillofacial region of interest (ROI2) of the patient using a second x-ray dose, this second set of acquired data corresponding to said 3D volume of data.

[0152] This acquisition step is performed using an x-ray CBCT imaging device, not necessarily device 10. This acquisition step may be separated in time from the first steps S1 to S7, for example by hours, days, months, etc. It is assumed that the patient's maxillofacial region has not been altered between the two acquisitions.

[0153] Here, method step S8 includes a previous patient positioning step (see steps S2 and S3 above) prior to acquiring a second set of data using different recorded or stored setting parameters defining the first position of the patient. This previous step prepares for adjusting setting parameters of the x-ray CBCT imaging apparatus, and in particular the patient positioning device or patient positioning accessory used in step S3, so that the patient is positioned at or near the same first position in view of this second data acquisition.

[0154] The obtained operating 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 to allow for the acquisition of a 3D volume of data including ROI2 relative to the patient's maxillofacial region.

[0155] The x-ray dose used for this second data acquisition is higher than the first x-ray dose generating the slice, and the first x-ray dose is no more than 20%, preferably no more than 10%, and more preferably no more than 5% of the second x-ray dose.

[0156] For example, the first x-ray dose is 4 μSv and the second x-ray dose is - 200μSv for 3D inspection with a wide field of view (17×13cm), - 20μSv for 3D inspection with a 5x5cm field of view It is.

[0157] For example, the duration of the x-ray exposure for the second data acquisition may be between 5 and 20 seconds for the 3D inspection, compared to approximately 5 seconds duration for the first data acquisition.

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

[0159] Although the present invention may have been described in detail and with particular reference to suitable or presently preferred embodiments, it is to be understood that variations and modifications can be effected within the spirit and scope of the invention. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restrictive. The scope of the present 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 therein.

Claims

1. 1. A method for obtaining operational parameters for an x-ray CBCT imaging device in view of acquiring a set of data for 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 a first maxillofacial region of interest (ROI1) of the patient when the patient is in an occlusal position or biting a patient positioning accessory; acquiring a first set of data for a first maxillofacial region of interest (ROI1) of the patient, the first set of data including the horizontal plane, using x-ray CBCT imaging through a slit-shaped collimator window, the first set of acquired data comprising a first set of x-ray images obtained at different angular positions relative to the first maxillofacial region of interest (ROI1) of the patient; reconstructing axial CBCT slices comprising the horizontal plane based on the first set of data for a first maxillofacial region of interest (ROI1) of the patient; displaying reconstructed axial CBCT slices of a first maxillofacial region of interest (ROI1) of the patient from the first set of acquired data; - at least partially defining a second region of interest (ROI2) based on the displayed and reconstructed axial CBCT slices of the patient's maxillofacial first region of interest (ROI1) and intersecting the reconstructed axial CBCT slices of the patient's maxillofacial first region of interest (ROI1); obtaining operational parameters for the x-ray CBCT imaging device based on at least a second defined region of interest (ROI2) in view of acquiring a second set of data including the second defined region of interest (ROI2); A method comprising:

2. 2. The method of claim 1, wherein the step of at least partially defining the second region of interest (ROI2) further comprises defining a position of the second region of interest (ROI2) within an xy plane of the axial CBCT slice.

3. 3. The method of claim 2, wherein the step of at least partially defining the second region of interest (ROI2) further comprises defining a position of the second region of interest (ROI2) along a z-axis (height) that is perpendicular to an xy-plane of the axial CBCT slice.

4. The step of defining the z-axis position of the second region of interest (ROI2) may include, in advance, acquiring a lateral x-ray scout view comprising a maxillofacial first region of interest (ROI1) of said patient; or acquiring an optical image comprising a first maxillofacial region of interest (ROI1) of said patient, said region of interest including landmarks; or performing physical measurements on a first maxillofacial region of interest (ROI1) of said patient using a patient positioning device; The method of claim 3 , comprising:

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

6. The method of claim 3 , wherein the z-axis location of the second region of interest (ROI2) is pre-determined.

7. The method of claim 1 , wherein the second region of interest (ROI2) has a size selected from a set of pre-determined values.

8. 4. The method of claim 3, wherein defining the z-axis position of the second region of interest (ROI2) is based on determining the height of the horizontal plane of the patient's maxillofacial first region of interest (ROI1) when the patient is in the bite position or biting a patient positioning accessory.

9. The step of determining the height of the horizontal plane of the maxillofacial first region of interest (ROI1) of the patient when the patient is in an occlusal position or bites a patient positioning accessory may include, in advance, acquiring a lateral x-ray scout view comprising a maxillofacial first region of interest (ROI1) of said patient; or acquiring an optical image comprising a first maxillofacial region of interest (ROI1) of said patient, said region of interest including landmarks; or performing physical measurements on a first maxillofacial region of interest (ROI1) of said patient using a patient positioning device; The method of claim 1 , comprising:

10. 2. The method of claim 1, wherein the first set of data is acquired while the patient is maintained in a first position via a patient positioning device, the first position being defined by a set of setting parameters for the patient positioning device.

11. The method of claim 10, further comprising prior adjustment of setting parameters of the patient positioning device before acquiring the second set of data.

12. The method of claim 1 , wherein the first set of data and the second set of data are separated in time.

13. 2. The method of claim 1, wherein the x-ray CBCT imaging device comprises an x-ray source and an x-ray sensor both operable to move simultaneously around the patient's head along a predetermined trajectory, and obtaining operating parameters for the x-ray CBCT imaging device based on the defined second region of interest (ROI2) comprises adjusting trajectories for both the x-ray source and the x-ray sensor based on the defined second region of interest (ROI2).

14. acquiring a second set of data comprising a second set of x-ray images acquired at a different angular position, the second set of x-ray images including the defined second region of interest (ROI2); for a second maxillofacial region of interest (ROI2) of the patient, reconstructing a 3D CBCT image including the defined second region of interest (ROI2) based on the second set of data; The method of claim 1 further comprising:

15. The method of claim 14 , wherein the 3D CBCT image has a higher resolution than the axial CBCT slices.

16. The method of claim 1, wherein the x-ray CBCT imaging device comprises an x-ray source and an x-ray sensor both operable to move simultaneously around the patient's head along a predetermined trajectory, and the method further comprises adjusting the position of a vertical slit-shaped collimator so that a horizontal axis between the x-ray source and the x-ray sensor intersects the slit.

17. The method of claim 16, further comprising a step of adjusting the slit-shaped collimator so that the slit opening has a minimum vertical width required to encompass the patient's maxillofacial first region of interest (ROI1).

18. 1. A system for obtaining operational parameters for x-ray CBCT imaging of a maxillofacial region of a patient, the system comprising: an x-ray source and at least one x-ray sensor configured to move around a maxillofacial first region of interest (ROI1) of the patient while irradiating the patient's maxillofacial first region of interest (ROI1) with a slit-shaped x-ray beam to acquire a first set of data for the patient's maxillofacial first region of interest (ROI1) when the patient is in an occlusal position or biting a patient positioning accessory, the x-ray source and at least one x-ray sensor configured to move around a maxillofacial first region of interest (ROI1) of the patient while irradiating the patient's maxillofacial first region of interest (ROI1) with a slit-shaped x-ray beam to acquire a first set of data for the patient's maxillofacial first region of interest (ROI1), the first set of acquired data comprising a first set of x-ray images including the horizontal plane obtained at different angular positions with respect to the patient's maxillofacial first region of interest (ROI1); 1. A microprocessor comprising: reconstructing axial CBCT slices comprising the horizontal plane based on the first set of data for a first maxillofacial region of interest (ROI1) of the patient; displaying reconstructed axial CBCT slices of the patient's maxillofacial first region of interest (ROI1) from the first set of acquired data using a view based on the displayed and reconstructed axial CBCT slices and for at least partially defining a second region of interest (ROI2) that intersects with the reconstructed axial CBCT slices of the patient's maxillofacial first region of interest (ROI1); and acquiring a second set of data including a defined second region of interest (ROI2); and obtaining operational parameters for the x-ray CBCT imaging device based on at least said defined second region of interest (ROI2). A microprocessor configured to A system comprising:

19. 20. The system of claim 18, wherein the obtained operating parameters for the x-ray CBCT imaging device based on the defined second region of interest (ROI2) comprise adjusted trajectories for both the x-ray source and the x-ray sensor based on the defined second region of interest (ROI2).

20. The system described in claim 18, wherein the microprocessor is further configured to adjust a position of the slit-shaped x-ray beam in a vertical direction so that at least a portion of the x-ray source is parallel to the horizontal plane.

21. The system described in claim 20, wherein the microprocessor is further configured to adjust a collimator that shapes the slit-shaped x-ray beam so that the slit-shaped x-ray beam has a minimum vertical spread required to encompass the patient's first maxillofacial region of interest (ROI1).

22. 13. A computer storage medium having stored therein instructions for causing a computer or microprocessor to perform the method of claim 1.

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