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Factors influencing superimposition error of 3D cephalometric landmarks by plane orientation method using 4 reference points: 4 point superimposition error regression model.

Hwang JJ, Kim KD, Park H, Park CS, Jeong HG - PLoS ONE (2014)

Bottom Line: Another 15 reference cephalometric points were also determined three times in the same image.Therefore, in order to reduce the reorientation error, accuracy of all landmarks including the reference points is important.Construction of the regression model using reference points of greater precision is required for the clinical application of this model.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral and Maxillofacial Radiology, Dental Hospital of Yonsei University of College of Dentistry, Seoul, Korea.

ABSTRACT
Superimposition has been used as a method to evaluate the changes of orthodontic or orthopedic treatment in the dental field. With the introduction of cone beam CT (CBCT), evaluating 3 dimensional changes after treatment became possible by superimposition. 4 point plane orientation is one of the simplest ways to achieve superimposition of 3 dimensional images. To find factors influencing superimposition error of cephalometric landmarks by 4 point plane orientation method and to evaluate the reproducibility of cephalometric landmarks for analyzing superimposition error, 20 patients were analyzed who had normal skeletal and occlusal relationship and took CBCT for diagnosis of temporomandibular disorder. The nasion, sella turcica, basion and midpoint between the left and the right most posterior point of the lesser wing of sphenoidal bone were used to define a three-dimensional (3D) anatomical reference co-ordinate system. Another 15 reference cephalometric points were also determined three times in the same image. Reorientation error of each landmark could be explained substantially (23%) by linear regression model, which consists of 3 factors describing position of each landmark towards reference axes and locating error. 4 point plane orientation system may produce an amount of reorientation error that may vary according to the perpendicular distance between the landmark and the x-axis; the reorientation error also increases as the locating error and shift of reference axes viewed from each landmark increases. Therefore, in order to reduce the reorientation error, accuracy of all landmarks including the reference points is important. Construction of the regression model using reference points of greater precision is required for the clinical application of this model.

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Related in: MedlinePlus

MLWS as a new starting point.x, y and z axis each represent reoriented transverse, anteroposterior and vertical axis.
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pone-0110665-g004: MLWS as a new starting point.x, y and z axis each represent reoriented transverse, anteroposterior and vertical axis.

Mentions: Four reference landmarks out of total 19 landmarks were used to define a 3D reference co-ordinate system. Using four landmarks as the setting point is one of the simplest way of plane reorientation which can be readily applicable in the clinic. The nasion (Na), sella turcica (S) and basion (Ba) were selected for axes determination. The orientation of y (anteroposterior) axis was parallel to the line which passes through Na and S. Z (vertical) axis was parallel to the line which is orthogonal to y axis and passes through Ba. (Figure 3) Orientation of x(transverse) axis was orthogonal to the y and z axis. And MLWS was set to a new starting point of the reoriented Cartesian co-ordinate system.(Figure 4).


Factors influencing superimposition error of 3D cephalometric landmarks by plane orientation method using 4 reference points: 4 point superimposition error regression model.

Hwang JJ, Kim KD, Park H, Park CS, Jeong HG - PLoS ONE (2014)

MLWS as a new starting point.x, y and z axis each represent reoriented transverse, anteroposterior and vertical axis.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4220943&req=5

pone-0110665-g004: MLWS as a new starting point.x, y and z axis each represent reoriented transverse, anteroposterior and vertical axis.
Mentions: Four reference landmarks out of total 19 landmarks were used to define a 3D reference co-ordinate system. Using four landmarks as the setting point is one of the simplest way of plane reorientation which can be readily applicable in the clinic. The nasion (Na), sella turcica (S) and basion (Ba) were selected for axes determination. The orientation of y (anteroposterior) axis was parallel to the line which passes through Na and S. Z (vertical) axis was parallel to the line which is orthogonal to y axis and passes through Ba. (Figure 3) Orientation of x(transverse) axis was orthogonal to the y and z axis. And MLWS was set to a new starting point of the reoriented Cartesian co-ordinate system.(Figure 4).

Bottom Line: Another 15 reference cephalometric points were also determined three times in the same image.Therefore, in order to reduce the reorientation error, accuracy of all landmarks including the reference points is important.Construction of the regression model using reference points of greater precision is required for the clinical application of this model.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral and Maxillofacial Radiology, Dental Hospital of Yonsei University of College of Dentistry, Seoul, Korea.

ABSTRACT
Superimposition has been used as a method to evaluate the changes of orthodontic or orthopedic treatment in the dental field. With the introduction of cone beam CT (CBCT), evaluating 3 dimensional changes after treatment became possible by superimposition. 4 point plane orientation is one of the simplest ways to achieve superimposition of 3 dimensional images. To find factors influencing superimposition error of cephalometric landmarks by 4 point plane orientation method and to evaluate the reproducibility of cephalometric landmarks for analyzing superimposition error, 20 patients were analyzed who had normal skeletal and occlusal relationship and took CBCT for diagnosis of temporomandibular disorder. The nasion, sella turcica, basion and midpoint between the left and the right most posterior point of the lesser wing of sphenoidal bone were used to define a three-dimensional (3D) anatomical reference co-ordinate system. Another 15 reference cephalometric points were also determined three times in the same image. Reorientation error of each landmark could be explained substantially (23%) by linear regression model, which consists of 3 factors describing position of each landmark towards reference axes and locating error. 4 point plane orientation system may produce an amount of reorientation error that may vary according to the perpendicular distance between the landmark and the x-axis; the reorientation error also increases as the locating error and shift of reference axes viewed from each landmark increases. Therefore, in order to reduce the reorientation error, accuracy of all landmarks including the reference points is important. Construction of the regression model using reference points of greater precision is required for the clinical application of this model.

Show MeSH
Related in: MedlinePlus