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EP-4736120-A1 - DETERMINING REAL-WORLD SIZES OF INTRAORAL FEATURES IN 2D IMAGES OF PATIENT DENTITION

EP4736120A1EP 4736120 A1EP4736120 A1EP 4736120A1EP-4736120-A1

Abstract

Apparatuses and methods for dental image analysis including determining pixel sizes of an image. A pixel size enables conversion of a two-dimension image-based measurement into a 3D measurement. The pixel sizes vary over the image due to differences in distance between the camera taking the image and the object of interest. A three-dimensional model may be registering to the two-dimension image, and the pixel sizes may be identified on a per-object (e.g., per-tooth) basis, per-region basis or at each point in the image. The pixel size scaling may be used to identify features in the image for diagnostic or other dental application purposes.

Inventors

  • GAO, YUN
  • LI, GUOTU
  • SHI, CHAO
  • CRAMER, CHRISTOPHER E.

Assignees

  • Align Technology, Inc.

Dates

Publication Date
20260506
Application Date
20240628

Claims (20)

  1. 1. A method compri sing : registering a two-dimensional (2D) image of a subject’s dentition with a three- dimensional (3D) representation of the subject’s dentition; generating a pixel size scaling for the 2D image of the subject’s dentition using the registered 3D representation, so that for each of one or more regions in the 2D image, the pixel size scaling comprises a scaling factor corresponding to each of the one or more regions indicating a size of the one or more pixels; and outputting the pixel size scaling.
  2. 2. The method of claim 1, further wherein registering comprises determining virtual camera parameters of a virtual camera such that a virtual image of the 3D representation taken with the virtual camera parameters matches the 2D image, and wherein generating the pixel size scaling for the 2D image comprises estimating different pixel size scaling for the one or more regions in the 2D image based on the virtual camera parameters including a ratio of a distance from the camera to the pixel and a distance from the camera to the 2D image.
  3. 3. The method of any of claims 1-2, further wherein the 2D image of the subject’s dentition is segmented to identify individual teeth corresponding to the one or more regions within the 2D image.
  4. 4. The method of any of claims 1-3, further comprising determining a length of a region of the 2D image using the pixel size scaling.
  5. 5. The method of claim 4, wherein determining the length of the region of the 2D image using the pixel size scaling comprises calculating and outputting one or more of: an overbite distance, an underbite distance, a posterior open bite distance, an interproximal spacing, and a distance between a tooth and an aligner.
  6. 6. The method of any of claims 1-5, wherein the size of the one or more pixels are in units of length per pixel. - 41 - SG Docket No.: 14187-74J.600 / 2217.US.WO
  7. 7. The method of any of claims 1-6, further comprising segmenting the 2D image to identify a plurality of individual teeth from the 2D image.
  8. 8. The method of any of claims 1-7, wherein generating the pixel size scaling for the 2D image of the subject’s dentition comprises determining the scaling factor for each visible tooth in the 2D image.
  9. 9. The method of claim 8, wherein at least two of the visible teeth in the 2D image have different pixel sizes.
  10. 10. The method of any of claims 1-9, further comprising selecting the 3D representation from a plurality of treatment plan 3D representations, wherein the selected 3D representation corresponds to a stage of a dental treatment plan that approximates the configuration of the subject’s dentition in the 2D image.
  11. 11. The method of any of claims 1-10, wherein registering comprises estimating a tooth shape based on a plurality of sample tooth shapes, and maximizing a fit of the estimated tooth shape with a corresponding tooth of the 2D image using principal component analysis (PCA).
  12. 12. The method of any of claims 1-10, wherein registering comprises using a dental kinematics simulation framework to simulate a virtual image that matches the 2D image.
  13. 13. The method of any of claims 1-12, wherein generating a pixel size scaling for the 2D image of the subject’s dentition comprises, for each visible tooth, determining a distance between two points on the 3D model, and calculating a ratio of the distance over a number of pixels between corresponding points of the 2D image.
  14. 14. The method of any of claims 1-13, wherein the one or more regions in the 2D image each include a crown center location of a tooth in the 3D model.
  15. 15. The method of any of claims 1-14, wherein outputting the pixel size scaling comprises outputting a data structure representing different pixel sizes for the one or more regions of the 2D image.
  16. 16. A method comprising: - 42 - SG Docket No.: 14187-74J.600 / 2217.US.WO registering a two-dimensional (2D) image of a subject’s dentition with a three- dimensional (3D) representation of the subject’s dentition to determine virtual camera parameters of a virtual camera such that a virtual image of the 3D representation taken with the virtual camera parameters matches the 2D image; generating a pixel size scaling for the 2D image of the subject’s dentition using the registered 3D representation of the subject’s dentition and the virtual camera parameters to estimate a scaling factor, in units of length per pixel, for pixels in the 2D image; and determining a length of a region of the 2D image using the pixel size scaling.
  17. 17. The method of claim 16, wherein generating the pixel size scaling for the 2D image comprises determining a field of pixel sizes across the 2D image.
  18. 18. The method of any of claims 16-17, wherein the virtual camera parameters include a distance between the virtual camera and the 3D representation.
  19. 19. The method of any of claims 16-18, further comprising selecting the 3D representation from a plurality of treatment plan 3D representations, wherein the selected 3D representation corresponds to a stage of a dental treatment plan that approximates the configuration of the subject’s dentition in the 2D image.
  20. 20. The method of any of claims 16-19, wherein registering comprises estimating a tooth shape based on a plurality of sample tooth shapes, and maximizing a fit of the estimated tooth shape with a corresponding tooth of the 2D image using principal component analysis (PCA).

Description

DETERMINING REAL-WORLD SIZES OF INTRAORAL FEATURES IN 2D IMAGES OF PATIENT DENTITION CLAIM OF PRIORITY [0001] This patent application claims priority to U.S. provisional patent application no. 63/511,635, titled “PIXEL SIZE ESTIMATION,” and filed on June 30, 2023, herein incorporated by reference in its entirety. INCORPORATION BY REFERENCE [0002] All publications and patent applications mentioned in this specification are herein incorporated by reference in their entirety to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. BACKGROUND [0003] Orthodontic and dental treatments using a series of patient-removable appliances (e.g., “aligners”) have been found to be very useful in treating patients’ teeth. Treatment planning is typically performed in conjunction with the dental professional (e.g., dentist, orthodontist, dental technician, etc.) by generating a model of the patient’s teeth in a final configuration and then dividing the treatment plan into a number of intermediate stages (steps) corresponding to individual appliances that are worn sequentially. This process may be interactive, adjusting the staging and in some cases the final target position, based on constraints on the movement of the teeth and the dental professional’s preferences. Once the final treatment plan is finalized, the series of aligners may be manufactured corresponding to the treatment plan. [0004] Treatment planning and monitoring requires the collection and processing of images of the patient’s teeth. For example, during orthodontic treatment, the dental professional periodically checks to make sure that the patient’s teeth are moving and responding correctly according to the treatment plan. This involves obtaining two- dimensional (2D) images of the patient’s teeth at their current (e.g., mid-treatment) positions and comparing these 2D images with images or models of the teeth in their expected positions at that point of treatment. If the current teeth positions are significantly off track from the expected positions according to the treatment plan, the dental practitioner may decide to have the patient repeat previous treatment steps or to modify the treatment plan - 1 - SG Docket No. 14187-74J.600 / 2217.US.WO altogether. Such assessments may involve determining very small (millimeter scale) differences in the current teeth positions versus expected teeth positions. Current image analysis techniques are not reliably able to resolve such small differences. [0005] What is needed are methods and apparatuses (including software) that can be used to measure very small differences in images of a patient’s teeth, in order to better assess the condition of the patient’s teeth and improve patient treatment and outcomes. SUMMARY OF THE DISCLOSURE [0006] The present disclosure generally relates to the estimation of pixel sizes in relation to image analysis and processing. More particularly, the present disclosure is related to systems, methods, computing device readable media, and devices for more accurately and quickly estimating pixel sizes for dental images used in dental treatment, monitoring, and planning. For example, described herein are methods and apparatuses that provide a framework for accurately estimating pixel sizes of digital images. The estimated pixel sizes may be used as conversion factors for converting pixels (of an image) to real-world measurements (e.g., micrometers, millimeters, etc.), thereby allowing for improved resolution of features in the image compared to conventional image analysis approaches. The methods may involve registering a three-dimensional (3D) model to a two dimensional (2D) image, and estimating pixel sizes in the 2D image on a per-object and/or per-region basis or as a field of different pixel sizes. The estimated pixel sizes may be mapped to points on the 2D image to generate an adjusted (e.g., scaled) 2D image. In any of these methods, the mapping may correct for possible distortions due to the orientation of the camera relative to the object or region, including determining a correction ratio that accounts for camera orientation. [0007] The methods and apparatuses described herein provide a technical solution to the technical problem of taking accurate measurements, particularly for very small dimensions, from one or more images of a subject’s teeth and/or oral cavity. In particular, these methods and apparatuses allow for very precise and rapid scaling of pixel size to actual dimensions, even across multiple images taken at a variety of different locations and orientations. Prior attempts to scale images of patient dentition are less accurate, particularly where parts of the teeth or other intraoral features are partially or fully blocked, for example, if the gingival line is obscured by the lips, if all or some of the teeth are not visible, etc. [0008] In contrast, the methods and apparatuses