Patent Application
20230097249
The described embodiments relate to the field of medical devices, in particular, the field of dental navigation systems.
Fiducials-based image-to-jaw registration methods applied in dental instrument guidance systems often require highly repeatable, rigid, coupling of the rigid part holding the fiducials to the jaw. Molding a rigid material to the jaw carries a risk of the rigid material getting “locked” on the jaw due to undercuts and spaces between teeth. Using an elastic material to prevent the locking risk enables an undesirable movement of the part relative to the jaw, putting repeatability at risk. These conflicting requirements can make it challenging to find a repeatable jaw coupling design for registration.
The various embodiments described herein generally relate to systems and methods for providing at least one fixture for an image-based guidance system for determining a registration coordinate mapping that aligns a human jaw with its volumetric CT (computerized X-ray tomography) image. An example kit includes:
the molded shape of the moldable thermoplastic material mates with a surface geometry of at least a portion of the human jaw and the coupling surface region of the channeled tray;
the moldable thermoplastic material is hardenable into an impression part such that when mated to the at least a portion of the human jaw and held within the channel of the channeled tray, the impression part resists displacement relative to the human jaw;
the channeled tray is removable from the impression part;
each channeled trays of the one or more channeled trays is individually repeatedly attachable to the impression part;
when a channeled tray is removed from the impression when the impression part is mated to the at least a portion of the human jaw, the impression part is bendable away from the surface geometry of the at least a portion of the human jaw such that the impression part is removable from, and repeatedly attachable to, the portion of the human jaw;
at least one channeled tray comprises a fiducial region detectable in the volumetric CT image in a fixed spatial relation relative to the coupling surface region; and
at least one channeled tray is pose-trackable by the image guidance system.
In any embodiment, the moldable thermoplastic material may be provided as a sheet less than 4 mm in thickness and 10 g in weight.
In any embodiment, the moldable thermoplastic material may be provided as a sheet less than 2 mm in thickness and 4 g in weight.
In any embodiment, the sheet may become moldable when heated to a temperature in the range of 50-90° C.
In any embodiment, the sheet may be heatable by hot air at an air temperature of about 200° C. for about 1 minute.
In any embodiment, the kit may further comprise a hot air heater for heating the sheet to the temperature in the range of 50-90° C.
In any embodiment, the fiducial region may comprise a plurality of cylindrical fiducials of at least two different diameters
In any embodiment, each channeled tray may comprise a base, a lingual wall and a facial wall, the lingual wall and facial wall extending from the base and spaced from each other so as to be adapted to receive at least one tooth, and wherein the fiducial region comprises a plurality of cylindrical fiducials embedded in the base of at least one of the channeled trays.
In any embodiment, the kit may comprise two optically pose-trackable channeled trays, each having trackable optical markings, wherein the trackable optical markings on each of the two trays may be in substantially different poses relative to the coupling surface region.
In any embodiment, the coupling surface region shared by each channeled tray may be shaped to constrain the motion for removing the tray from the impression part such that when attached to the impression part, the channeled tray remains in a fixed spatial relationship to the impression part when not pulled away from it by a human operator.
In any embodiment, a pose-trackable channeled tray may carry trackable optical markings, and the kit may further comprise calibration data for defining a mapping between a coordinate frame of the trackable optical markings and a coordinate frame of the impression part when the channeled tray is in the fixed spatial relationship to the impression part.
In any embodiment, the coupling surface region may be shaped to prevent full insertion of the impression part into the channel in a channeled tray in an orientation or position other than a single unique one.
In any embodiment, the kit may comprise two channeled trays, wherein one of the two trays may be pose-trackable, and wherein a portion of the channel in the pose-trackable tray may be narrower than the corresponding portion of the channel in the other tray to provide it with increased retention when coupled to an impression part molded by the other tray.
An example method for determining a registration coordinate mapping between a human jaw and a volumetric CT (computerized X-ray tomography) image of that jaw includes:
In any embodiment, the method may further comprise providing calibration data defining a mapping between a coordinate frame of the trackable channeled tray and a coordinate frame of the fiducial region, and wherein determining the registration coordinate mapping between the human jaw and its volumetric CT image may be partly based on the calibration data.
In any embodiment, the method may further comprise determining a selected position in the coordinate frame of the pose-trackable tray, and then using the registration coordinate mapping to map coordinates of the selected position to a corresponding position in the volumetric CT image.
In any embodiment, each channeled tray may define a corresponding channel comprising a base, a lingual wall and a facial wall, the lingual wall and facial wall extending from the base and spaced from each other so as to be adapted to receive at least one tooth; and
In any embodiment, the method may further comprise molding some of the moldable thermoplastic material over nearby surfaces of the human jaw, the nearby surfaces of the human jaw being outside the corresponding channel of the channeled tray.
In any embodiment, providing the moldable thermoplastic material may comprise providing the moldable thermoplastic material as a sheet less than 4 mm in thickness and 10 g in weight
In any embodiment, providing the moldable thermoplastic material may comprise providing the moldable thermoplastic material as a sheet less than 2 mm in thickness and 4 g in weight.
In any embodiment, the method may further comprise before forming the molded shape of the moldable thermoplastic material in the channeled tray, softening the sheet by heating the sheet to a temperature in the range of 50-90° C.
In any embodiment, the method may further comprise before forming the molded shape of the moldable thermoplastic material in the channeled tray, heating the sheet to a temperature in the range of 50-90° C., to soften the sheet, by blowing air at a temperature higher than 100° C. over a surface the sheet.
In any embodiment, each channeled tray may define a corresponding channel comprising a base, a lingual wall and a facial wall, the lingual wall and facial wall extending from the base and spaced from each other so as to be adapted to receive at least one tooth; and,
These and other aspects and features of various embodiments will be described in greater detail below.
Several embodiments will now be described in detail with reference to the drawings, in which:
The drawings, described below, are provided for purposes of illustration, and not of limitation, of the aspects and features of various examples of embodiments described herein. For simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn to scale. The dimensions of some of the elements may be exaggerated relative to other elements for clarity. It will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements or steps.
It will be appreciated that numerous specific details are set forth in order to provide a thorough understanding of the example embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Furthermore, this description and the drawings are not to be considered as limiting the scope of the embodiments described herein in any way, but rather as merely describing the implementation of the various embodiments described herein.
It should be noted that terms of degree such as “substantially”, “about” and “approximately” when used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of the modified term if this deviation would not negate the meaning of the term it modifies.
In addition, as used herein, the wording “and/or” is intended to represent an inclusive-or. That is, “X and/or Y” is intended to mean X or Y or both, for example. As a further example, “X, Y, and/or Z” is intended to mean X or Y or Z or any combination thereof.
It should be noted that the term “coupled” used herein indicates that two elements can be directly coupled to one another or coupled to one another through one or more intermediate elements.
In at least one embodiment, aspects of methods described herein, such as method 1000 described with reference to
In at least one embodiment, the communication component may be a network communication interface. In embodiments in which elements are combined, the communication component may be a software communication interface, such as those for inter-process communication (IPC). In still other embodiments, there may be a combination of communication components implemented as hardware, software, and combination thereof.
Program code may be applied to input data to perform the functions described herein and to generate output information. The output information is applied to one or more output devices, in known fashion.
Each program may be implemented in a high level procedural or object oriented programming and/or scripting language, or both, to communicate with a computer system. However, the programs may be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language. Each such computer program may be stored on a storage media or a device (e.g., ROM, magnetic disk, optical disc) readable by a general or special purpose programmable computer, for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. Embodiments of the system may also be considered to be implemented as a non-transitory computer-readable storage medium, configured with a computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner to perform the functions described herein.
Referring now to
The impression registration system 100 may be used to register a coordinate system of a trackable object 420 rigidly attached jaw 600 with the coordinate system of its CT image 500 to accurately align the anatomical features of the jaw with their appearance in the image. Registering the jaw 600 with the CT image 500 may allow pose-trackable components of the system 100 to be used for providing guidance during the treatment of a patient. The system 100 may be provided as a kit of various components, depending on the desired use of the system 100.
Referring to
The moldable thermoplastic material 200 is insertable into the tray 300 to mold into a molded shape within the channeled tray. The molded shape of the moldable thermoplastic material 200 mates with a surface geometry of at least a portion of the human jaw 600 and the coupling surface region 342 of the tray 300. The moldable thermoplastic material 200 is then hardenable into an impression part 210 such that when mated to the at least a portion of the human jaw and held within the channel 340 of the tray 300, the impression part 210 resists displacement relative to the human jaw. Resisting displacement relative to the jaw may allow for repeatable measurements to be taken during the registration and the subsequent guidance processes, thereby improving the accuracy of the mapping and subsequent use during treatment.
The moldable plastic material 200 may have sufficient viscosity, when heated, that it does not penetrate deeply into cracks between the teeth of the patient. Excess material 230, as shown in
Once the impression part 210 is formed by hardening, the tray 300 is removable from the impression part 210. Each tray used in the system 100 may be individually repeatably attachable to the impression part 210. When the impression part 210 is mated to the at least a portion of the human jaw, the tray 300 may be removed from the impression part 210 by pulling it away. The impression part 210 is then free to be bent away and removed from the surface geometry of the at least a portion of the human jaw. Thus, the impression part 210 is removable from, and repeatedly attachable to, the portion of the human jaw.
The coupling surface region 342 in each channeled tray 300 may be shaped to constrain the motion for removing the tray 300 from the impression part 210 such that when the tray 300 is attached to the impression part 210, the tray remains in a fixed spatial relationship to the impression part 210 when not pulled away from it by a human operator. In some embodiments, the coupling surface region 342 may be shaped to prevent full insertion of the impression part 210 into the channel 340 in an orientation or position other than a single unique one. In other words, the impression part 210 may only be received by the coupling surface region 342 in a single orientation and/or position. For example, referring to
The shape of the tray 300 may be designed such that the tray 300 is removable from the hardened impression part 210 by pulling the tray 300 away from the impression part 210. The tray's position may be restored relative to the hardened impression part 210 by pushing the tray 300 back onto the impression part 210. When hardened, the impression part 210 may have sufficient elasticity to be bent as needed to release it from the jaw, thereby releasing the impression part 210 from any undercuts. Thus, the impression part 210 may form a molded part that can be removed from the jaw while still providing sufficient rigidity to the tray 300 such that the tray 300 may be used for tracking during treatment.
The moldable thermoplastic material 200 may be provided as a sheet. For example, referring to
The moldable thermoplastic material may be heated to facilitate the molding process. For example, the moldable thermoplastic material 200 may become moldable when heated to a temperature in the range of 50-90° C. The moldable thermoplastic material 200 may be heated by any means, including, but not limited to hot air. For example, the material 200 may be heatable by hot air at an air temperature of about 200° C. for about 1 minute to become moldable. In some embodiments, the system 100 may include a hot air heater 140 for heating the moldable thermoplastic material 200 to the range of 50-90° C. The use of hot air instead of water may increase the speed of heating and reduce mess associated with the heating process.
The moldable plastic material 200 may be any material that is viscous enough when heated to mold to at least a portion of a human jaw. For example, the material may be viscous enough to be pressed around teeth of the patient such that the material molds to the teeth. The moldable plastic material 200 may be, including, but not limited to, a compound based on polycaprolactone and/or a biodegradable polyester such as Rolyan Polyform.
The tray 300 may include a fiducial region 350 detectable in the volumetric CT image in a fixed spatial relation relative to the coupling surface 342. The fiducial region 350 may include one or more fiducials 352 embedded in the base 310 of the tray 300. For example, as shown in
The fiducials 352 may be arranged in a manner that is not rotationally symmetrical. A rotationally asymmetrical arrangement can be used to uniquely define a coordinate frame anchored to the tray 300. As described above, the tray 300 may be uniquely positionally coupled to the impression part 210 when mated to the impression part 210 and may remain anchored during the CT scan.
The fiducials 352 may be made of a material with radiopacity similar to dense bone. For example, the fiducials 352 may be made of an aluminum alloy. In contrast, the tray 300 may be made of a material that has a similar density to soft tissue, such as a thermoplastic. Using different materials may improve the ability of the imaging system to discern the difference between the tray 300 and the fiducials. The different radiopacities of the materials used in the system 100 may also allow for automatic calibration of image values in the CT scan.
The cylindrical fiducials 352 may have the same diameter or may have at least two different diameters. For example, two diameters may be 1.5 mm and 2.0 mm. The size of the fiducials 352 may vary depending on the use of the system 100. Using fiducials 352 with two or more different diameters may improve the reliability of automatic detection and localization of the fiducials 352 in the CT image, facilitating distinguishing fiducials 352 from one another. As shown in
The system 100 can include a plurality of trays 300. Each tray 300 in the system 100 may be used for the same or different purposes. For example, the system 100 may include at least one pose-trackable tray 400 that is pose-trackable by an image guidance system. The pose-trackable tray 400 may have the same or different structure than the tray 300. Referring to
The pose-trackable tray 400 may be positioned over the impression part 210 to secure the pose-trackable tray 400 to the jaw 600. This coupling between the pose-trackable tray 400 and the jaw 600 may allow for tracking of the jaw during the guidance process. The coordinate mapping between the pose-trackable tray 400 and its respective trackable optical markings 420 and the fiducials 352 present in the CT scan may be pre-calibrated to provide registration without the need for calibration or fiducial localization prior to guidance. This registration may be relatively instantaneous.
The system 100 may include calibration data for defining a mapping between a coordinate frame of the trackable optical markings 420 and a coordinate frame of the impression part when the tray 400 is in the fixed spatial relationship to the impression part.
An example coordinate system may be defined by the centerlines of two co-planar pin fiducials. The intersection point between the centerlines may define the origin. The centerline of the thicker pin (larger diameter) may define the x-axis and the cross product between the centerline vectors may define the z-axis. The y-axis may be defined as the cross product of the x and z-axis vectors.
The system 100 may include a plurality of pose-trackable trays 400 with each tray 400 having trackable optical markings 420 facing the camera when the tray is mounted at different positions along the jaw arch. For example, as shown in
Computing the mapping between the pose-tracking space and the CT space may involve three mappings, as illustrated in
The second mapping 120, between the fiducials 352 and the impression part 210 may be determined by the shape of the tray 300. The tray 300 may be measured once using a specialized jig that couples a trackable marker defining a trackable coordinate system to the impression part 210. The tray 300 may then be mounted to the impression part 210 and the centerlines of the two pin boreholes in the tray 300 in the impression part 210 coordinate system may be measured (as defined by the trackable marker).
The third mapping 130 may be measured for each pose-trackable tray 400 using the specialized jig described above and may be communicated to the navigation system software using an optical tracking marker on the pose-trackable tray 400. Each trackable arm 410 may be individually calibrated during the production process by measuring the mapping between the coordinate system of the trackable optical markings 420 and the coordinate system of the impression part 210. The appropriate calibration information may be retrieved by the navigation software using the trackable optical markings 420 on each trackable arm 410 as a part identifier. The part identifier can be registered prior to mapping so that the navigation software is able to calibrate each trackable arm 410. Pre-calibrating the pose-trackable tray 400 may improve the accuracy of tracking while eliminating the need for the user to perform a time-consuming tracker calibration prior to the guidance process, thereby simplifying and speeding up the guidance process.
In some embodiments, the pose-trackable tray 400 may have a portion of the channel that is narrower than the corresponding portion of the channel in the tray 300 to provide the narrowed channel with increased retention when coupled to the impression part 210 molded by the tray 300.
Method for Determining Registration Coordinate Mapping Between a Human Jaw and a Volumetric CT Image of that Jaw
Referring to
The tray 300 containing the heated moldable plastic material 200 can then be pressed against at least a portion of the jaw 600 of the patient, either by an operator (such as dentist or dental assistant), or by having the patient bite on the tray. As shown, the tray 300 is pressed against approximately three teeth neighbouring the treatment site. The tray 300 may be left for approximately one minute to allow the moldable plastic material 200 to harden into the impression part 210. For example, leaving the previously heated moldable thermoplastic material 200 for one minute allows the material to cool, thereby hardening into the impression part 210. In some embodiments, the moldable material 200 may be hardened by a chemical reaction. For example, the moldable material 200 may be hardened by a chemical reaction.
Referring to
Once the CT scan is complete, the tray 300 may be removed from the impression part 210. The impression part 210 may then be removed from the teeth. As described previously, the impression part 210 may be separable from the tray 300 due to the design of the channel 340 to grip the impression part 210 while still allowing it to be removed by the user by pulling it away in a specific direction. Without the constraining tray, the plastic impression part 210 may be flexible enough to be removable from the jaw 600 of the patient even with the presence of undercuts. Once removed, the tray 300 may be disinfected for reuse, and the impression part 210 may be stored, for example, in a bag 150, for future use.
Referring to
Referring to
At 1010, one or more channeled trays 300 are provided. The channeled trays are made of a rigid material that will not substantially deform when subjected to temperatures of about 70 degrees C. A portion of the surface of the channel 340 in each channeled tray 300 defines a coupling surface region 342.
At 1020, a moldable thermoplastic material 200 is provided. Optionally, the moldable thermoplastic material 200 may be softened by heating the material 200 to a temperature in the range of 50-90° C. As described previously, the heating process may use hot air, e.g., air at a temperature higher than 100° C., passing over a surface of the moldable thermoplastic material 200.
At 1030, the moldable thermoplastic material 200 is inserted into the channeled tray. Optionally, inserting the moldable thermoplastic material 200 into the tray 300 may include folding or rolling the material 200 prior to inserting it into the channel 340 of the tray 300. The channeled tray 300 has a fiducial region 350 in a fixed spatial relation relative to the coupling surface region with the boundary of the fiducial region 350 being detectable in a volumetric CT image.
At 1040, a molded shape of the moldable thermoplastic material 200 is formed in the channeled tray 300 to mate with a surface geometry of at least a portion of the human jaw 600 and the coupling surface 342 of the channeled tray 300. For example, the channel 340 in the channeled tray 300 may be sized and shaped such that it is adapted to receive at least one tooth and the molded shape formed by the moldable thermoplastic material 200 may be formed by receiving at least one tooth in the channel 340 of the tray 300. Optionally, some of the moldable thermoplastic material 200 may be molded over nearby surfaces of the human jaw 600 that are outside the corresponding channel 340 of the channeled tray 300.
At 1050, the molded shape of the moldable thermoplastic material 200 is hardened into an impression part 210 such that when mated to the at least a portion of the human jaw 600 and held within a channel 340 of the channeled tray 300, the impression part 210 resists displacement relative to the human jaw 600. The channeled tray 300 is removable from the impression part 210 and each channeled tray 300 is individually repeatedly attachable to the impression part 210. The impression part 210 is removable from, and repeatedly attachable to, the portion of the human jaw 600.
At 1060, a volumetric CT image 500 of a portion of the jaw 600 and the channeled tray 300 coupled to it by the impression part 210 is obtained.
At 1070, the channeled tray 300 is removed from the impression part 210.
At 1080, the impression part 210 is bent away from the surface geometry of the at least a portion of the human jaw 600 to remove the impression part 210 from the human jaw 600.
At 1090, the impression part 210 is again mated with the surface geometry of the at least a portion of the human jaw 600.
In some embodiments, when the CT scan is taken just prior to the dental procedure, impression part 210 may be left on the jaw between the scan and the procedure, removing the need to perform steps 1080 and 1090.
At 1100, a trackable channeled tray 400 that is pose-trackable by the image guidance system is coupled to the impression part 210.
At 1110, a registration coordinate mapping between the human jaw and its volumetric CT image is determined based on a coordinate mapping between a coordinate frame of the pose-trackable tray 400 and a coordinate frame of the fiducial region's appearance in the image. Optionally, calibration data may be provided defining a mapping between a coordinate frame of the pose-trackable tray 400 and a coordinate frame of the fiducial region. Determining the registration coordinate mapping between the human jaw 600 and the volumetric CT image may be at least partly based on the calibration data.
In some embodiments, the method 1000 may further include determining a selected position in the coordinate frame of the pose-trackable tray 400 and using the registration coordinate mapping to map coordinates of the selected position to a corresponding position in the volumetric CT image.
Various embodiments have been described herein by way of example only. Various modification and variations may be made to these example embodiments without departing from the spirit and scope of the invention, which is limited only by the appended claims.
This application claims the benefit of U.S. Provisional Patent Application No. 63/250,273, filed Sep. 30, 2021, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63250273 | Sep 2021 | US |
