CN112494163A

CN112494163A - Transverse rotation axis positioning and extracting method for mandibular CBCT data

Info

Publication number: CN112494163A
Application number: CN202011356621.5A
Authority: CN
Inventors: 施洁珺
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-11-27
Filing date: 2020-11-27
Publication date: 2021-03-16
Anticipated expiration: 2040-11-27
Also published as: CN112494163B

Abstract

The invention discloses a transverse rotation axis positioning and extracting method of mandibular CBCT data. Collecting CBCT data of a patient in a closed state and a state after the patient bites the insertion sheet, and acquiring the CBCT data of the patient in the open state and the closed state; carrying out registration operation on the closed CBCT data of the patient in the closed state and the opening CBCT data of the patient in the state after the insertion sheet is occluded; positioning the two-sided projection plane; and processing to obtain the moving rotating centers of the jaw bones at the left side and the right side, and connecting to obtain the transverse rotating shaft of the mandible. According to the invention, a more accurate transverse mandible rotating shaft is obtained, the data result more real close to teeth of a patient is obtained, and the convenience and precision of tooth data positioning are improved.

Description

Transverse rotation axis positioning and extracting method for mandibular CBCT data

Technical Field

The invention belongs to a processing method of CBCT data of a tooth mandible in the field of oral cavity digital model processing, and particularly relates to a transverse rotation axis positioning and extracting method of CBCT data of the mandible.

Technical Field

The computer simulation of the movement of the mandible is one of the key technologies for oral correction, and the computer simulation of the movement of the mandible can help to improve the accuracy of oral treatment diagnosis.

When the mandible of a person performs a small opening and closing movement, the mandible rotates only along a transverse rotating shaft, which is also called a hinge shaft.

Traditionally, the measurement of the transverse rotation axis requires the use of professional equipment such as a motion face bow, takes a long time and requires a certain experience of the operator. In practical use, an operator uses an "empirical rotation axis" as the transverse rotation axis, and the transverse rotation axis is determined by determining a position 13mm forward from the tragus on the connection line from the tragus to the outer tip of the patient and forming the left and right side connection lines, but the error of the method is large.

Cone Beam Computed Tomography (CBCT) is an increasingly common imaging technique in orthodontics. The CBCT scanning can accurately display the form and the position relation of the upper jaw and the lower jaw, meets the three-dimensional measurement requirements of teeth and jaws, and has gradually become an important data acquisition means for personalized correction.

Disclosure of Invention

In order to solve the problems in the background art, the invention provides a transverse rotation axis positioning and extracting method of mandibular CBCT data.

The technical scheme of the invention is as follows:

step 1) collecting CBCT data of a patient in a closed state and a post-occlusion state to obtain the CBCT data of the patient in the open state and the closed state, wherein the CBCT data comprises a three-dimensional image, and the post-occlusion state is used as an open state; carrying out registration operation on the patient closed CBCT data CT0 in the closed state and the patient open CBCT data CT1 in the post-occlusion state;

step 2), positioning the bilateral projection plane;

and 3) processing to obtain the moving rotation centers of the jaw bones on the left side and the right side, and connecting to obtain the transverse rotation axis of the mandible.

The step 1) is as follows:

1.1) respectively carrying out three-dimensional reconstruction operation according to the closed CBCT data CT0 and the open CBCT data CT1 to obtain an open mandible model M0 when the patient is open and a closed mandible model M1 when the patient is closed;

1.2) setting four pairs of marking points for maxillary fixation as the marking points at which the open maxilla model M0 and the closed maxilla model M1 overlap;

1.3) calculating transformation matrices [ T, R ] transformed from the closed maxilla model M1 to the open maxilla model M0 based on the relationships between the marked points, T, R respectively representing translation matrices and rotation matrices in the transformation matrices, and updating the closed maxilla model M1 based on the transformation matrices [ T, R ].

The step 2) is as follows:

2.1) constructing an initial sagittal plane P _ init: determining a maxilla nose tip point P-N and a maxillary anterior nose spine point P-Ans, and making an initial sagittal plane P _ init passing through the maxilla nose tip point P-N and the maxillary anterior nose spine point P-Ans, wherein the initial sagittal plane P _ init bisects the maxilla in the open maxilla model M0 and the closed maxilla model M1;

2.2) translating the plane to the left and right sides of the tooth respectively to obtain a left projection plane PL and a right projection plane PR, wherein the left projection plane PL and the right projection plane PR respectively pass through and equally divide the left condyle portion and the right condyle portion; the left projection plane PL and the right projection plane PR constitute a double-sided projection plane.

The step 3) is as follows:

3.1) determining two pairs of marker points, wherein each pair of marker points comprises two feature points, respectively a point Pij on the mandible of the open mandible model M0 and a point Pik on the mandible of the closed mandible model M1; the point Pij and the point Pik are points of the same position in the actual mandible;

3.2) projecting all four points in the two groups of mark points to the projection planes on the two sides respectively to obtain projection points, and projecting all the four points to obtain eight points;

3.3) calculating the position of the left rotation center according to four projection points obtained by projecting the four points onto the left projection plane, and calculating the position of the right rotation center according to four projection points obtained by projecting the four points onto the right projection plane;

and 3.4) connecting the left and right rotating centers to obtain a straight line as a transverse rotating shaft of the mandible.

In the step 3.3), two groups of mark points and projection points thereof after projection are { a, a ', B' }, and the left rotation center and the right rotation center are obtained according to the following processing modes:

a) calculating a perpendicular bisector L1 between the two points of the mark point A and the projection point A' before and after the first group of mark points are projected;

b) calculating a perpendicular bisector L2 between the two points of the mark point B and the projection point B' before and after the projection of the second group of mark points;

c) and calculating an intersection point O between the perpendicular bisector L1 and the perpendicular bisector L2, namely the rotation center.

The mandible opening and closing device compares the mandible data in the closed state and the mandible data in the two states after the insertion sheet is occluded to obtain the change before and after the mandible opening and closing movement; and comparing the changing positions of the mandible model before and after the opening and closing movement to obtain the central point around which the mandible rotates at two sides, and further connecting the lines to obtain the transverse mandible rotating shaft.

The position of the teeth is related to the motion rule of the upper jaw and the lower jaw, and meanwhile, the relative position of the upper jaw and the lower jaw can be influenced by the movement of the teeth generated by correction.

The invention has the following beneficial effects:

according to the invention, the CBCT data of the patient is added to the mandible movement for processing and evaluation, and the CBCT data of the patient in the closed state and the CBCT data of the patient in the post-occlusion insertion sheet are overlapped by utilizing three-dimensional overlapping, so that a more accurate mandible transverse rotating shaft is obtained by further processing, a more real data result is closer to the teeth of the patient, and the convenience and the precision of tooth data positioning are improved.

Drawings

FIG. 1 is an overall process flow diagram of the present invention;

FIG. 2 is a schematic diagram of an initial sagittal plane P _ init determination;

fig. 3 is a schematic diagram of a method for determining a single-side rotation center.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

The specific embodiment and the implementation process of the invention are as follows:

step 1) collecting CBCT data of a patient in a closed state and a state after the patient bites an insertion piece, and acquiring the CBCT data of the patient in the open state and the closed state; the patient's closed CBCT data CT0 in the closed state and the patient's open CBCT data CT1 in the post-occlusion state are registered.

1.3) calculating transformation matrices [ T, R ] transformed from the closed maxilla model M1 to the open maxilla model M0 based on the relationships between the marked points, T, R respectively representing translation matrices and rotation matrices in the transformation matrices, and updating the closed maxilla model M1 based on the transformation matrices [ T, R ]. The maxilla of the open maxilla model M0 and the closed maxilla model M1 are now in co-registration.

And 2) positioning the two-side projection plane, wherein the left side projection plane is defined as PL, and the right side projection plane is defined as PR.

The method for determining the projection plane comprises the following steps:

2.1) constructing an initial sagittal plane P _ init: determining a maxilla nose tip point P-N and a maxillary anterior nose spine point P-Ans, wherein the two points are shown in FIG. 2, and making an initial sagittal plane P _ init passing through the maxillary nose tip point P-N and the maxillary anterior nose spine point P-Ans, wherein the initial sagittal plane P _ init bisects the maxilla in the open maxilla model M0 and the closed maxilla model M1; bisection may be such that the left and right infraorbital foramen centers are equidistant from the plane P _ init, as shown in fig. 2.

And 3) calculating the moving rotation centers of the jaw bones on the left side and the right side, and connecting the centers to obtain the transverse rotation axis of the mandible.

Method for calculating jaw bone rotation center:

(1) determining two pairs of marker points, wherein each pair of marker points comprises two feature points, respectively a point Pij on the mandible of the open mandible model M0 and a point Pik on the mandible of the closed mandible model M1; the point Pij and the point Pik are points of the same position in the actual mandible;

(2) projecting the points in the two groups of mark points to the bilateral projection planes of the left projection plane PL and the right projection plane PR respectively to obtain points on the corresponding projection planes as projection points, and projecting the points to obtain eight points;

(3) and calculating the positions of the left and right rotation centers according to the four projection points obtained by projecting the four points onto the left projection plane.

As shown in fig. 3, taking two sets of mark points on the right projection plane PR as an example, the names are defined as { a, a ', B' }, where a and a 'are projections of mark points corresponding to the same positions on the front and rear jaws on the right projection plane PR, B and B' are projections of mark points corresponding to the same positions on the front and rear jaws on the right projection plane PR, and the right rotation center is determined by:

a) calculating a perpendicular bisector L1 of A and A';

b) calculating a perpendicular bisector L2 of B and B';

c) the intersection O between L1 and L2 is calculated as the right center of rotation.

Similarly, the left rotation center can also be calculated.

(4) The left and right rotating centers are connected to obtain a straight line Laxis which is the transverse rotating shaft of the mandible.

Claims

1. A method for extracting the lateral rotation axis of CBCT data of mandible is characterized by comprising the following steps:

step 1) collecting CBCT data of a patient in a closed state and a state after the patient bites an insertion piece, and acquiring the CBCT data of the patient in the open state and the closed state; carrying out registration operation on the patient closed CBCT data CT0 in the closed state and the patient open CBCT data CT1 in the post-occlusion state;

step 2), positioning the bilateral projection plane;

2. The method for extracting the lateral rotation axis location of CBCT data of mandible according to claim 1, wherein the step 1) is as follows:

3. The method for extracting CBCT data of mandible according to claim 1, wherein the method comprises the following steps: the step 2) is as follows:

4. The method for extracting CBCT data of mandible according to claim 1, wherein the method comprises the following steps: the step 3) is as follows:

5. The method for extracting CBCT data of mandible according to claim 4, wherein the method comprises the following steps: in the step 3.3), two groups of mark points and projection points thereof after projection are { a, a ', B' }, and the left rotation center and the right rotation center are obtained according to the following processing modes: