A New Method For The Establishment Of Three-dimensional Cephalometric Analysis Of Craniofacial Anatomical Markers And Its Application

In clinical work,the important basis for doctors to develop treatment plans for patients with craniofacial deformity is to accurately and fully analyze the patient's condition.The cephalometric analysis is a clinical analysis method proposed by Broadbent on the X-ray film in 1931^[1],which is mainly used for the diagnosis and analysis of the relationship between the soft and hard tissue deformity of the craniomaxillofacial region.Once applied,this technique becomes an important method for measuring the malformation of the soft and hard tissues of the craniofacial region.However,the two-dimensional cephalometric measurement exists:1.The head position difference is large when the X-ray film is irradiated between individuals;2.The left-sided symmetrical anatomical structure image is not highly overlapped;3.The image scale-up magnification distortion is obvious,which is clinically the accuracy and stability of the doctor's analysis of the diagnosis has a greater impact.Since the results of the two-dimensional analysis are not able to completely and accurately reflect the deformity relationship between the anatomical structures,it is easy to cause deviations in the diagnosis and treatment planning.The CT-based 3D reconstructed image can fully reproduce the patient's anatomy and truly and objectively display the relationship of deformed features.Therefore,it is of great significance to introduce 3D cephalometric measurement in the diagnosis and analysis of craniofacial deformity.The definition and analysis method of anatomical landmarks in traditional two-dimensional cephalometric measurement is not fully applicable to three-dimensional cephalometric measurement.At present,there is no unified definition method for anatomical landmarks in three-dimensional cephalometric measurement of craniomaxillofacial:because of subjective factors the influence of 3D cephalometric measurement results is large,which limits its application in the diagnosis and analysis of craniofacial deformity.This study intends to establish a new method for locating the cranial and maxillofacial anatomical landmarks in three-dimensional cephalometric measurement,and to compare the stability and accuracy of the method with the conventional manual direct-point method.The application provides a theoretical basis.Objective?1?Initially establish a new method for locating the anatomical landmarks of the cranial and maxillofacial regions during 3D cephalometric measurement;?2?Compare the results of the new method with conventional direct fixation methods to demonstrate the new fixed-point method Stability?reliability?;?3?The accuracy?validity?of the new fixed-point method is demonstrated by comparing the new method with the measurement results of the conventional direct-point method.Through the above research,theoretical support is provided for introducing the new method into the cephalometric analysis work.Methods1.First,establish a CT three-dimensional reconstruction data model of craniomaxillofacial hard tissue,write a script in the software,use the"centroid"function to select the fitting region to locate the relevant anatomical landmarks,and initially establish a new three-dimensional cephalometric measurement.The method of anatomical landmark positioning.2.3 observers used the selection of the fitting area to generate the centroid?experimental group?and the conventional fixed point?control group?at intervals of 0 months,1 month,and 2 months,in 20 cases of skull 3D data model.Positional measurements of 26 soft tissue anatomical landmarks and 19 hard tissue anatomical landmarks were performed,and intra-observer reliability Intra-class correlation coefficients?ICC?and inter-observer correlation coefficients were used.?inter-observer reliability Intra-class correlation coefficients,ICC?,to evaluate the reliability and stability of the new fixed-point method.At the same time,the mixed effect model is used to analyze the influence of two different factors of“observer”and“time”on the research results.3.The coordinate values of the anatomical landmarks collected by the above experiments are experimental data.After observing the observer and the time effect,only the effects of different observation methods are considered.A paired sample t test was used to perform statistical analysis on the two sets of data to evaluate the accuracy of the new fixed-point method.Results1.For the first time,a positioning method that automatically generates a centroid to represent an anatomical landmark by a computer software selection fitting region is successfully established,and can be observed using this method.2.The results of ICC showed:?1?Experimental group:43 anatomical landmarks among45 anatomical landmarks.The ICC analysis values??were?0.9 in the observer and the observer,and the effective rate reached 95.6%,indicating that there was a height.Reproducibility;only the left and right hard tissue ear points?PR,PL?two anatomical landmarks between the observer and the observer ICC value between 0.75⁰.9,indicating reproducibility is acceptable.?2?Control group:?1?ICC results of 5 anatomical landmarks such as ZvR,ZvL,OrL,PR,PL,etc.are between 0.75 and 0.9,indicating repeatability;?2?ZvR,ZvL,OrL,ZpR,ZpL The ICC results between the five anatomical landmarks were between 0.75 and 0.9,indicating that the repeatability was acceptable.Two anatomical landmarks such as ZpR and ZpL were mainly expressed in the Y-axis;?3?ANS,BcR,BcL three anatomical landmarks showed an ICC result of<0.75 between the observer and the observer,indicating poor reproducibility and mainly focusing on the instability of the X-axis.?4?PR?PL and other two anatomical landmarks between the observers ICC<0.75,indicating poor repeatability,mainly X-axis instability.?5?The remaining 35 anatomical landmarks have an ICC value of?0.9 between the observer and the observer,which is highly reproducible.3.The paired sample t-test results showed that the coordinate data of 31 anatomical landmarks in the two groups had a P value of<0.05,and the difference was statistically significant:?1?the coordinates of 16 anatomical landmarks were in the direction of 3coordinate axes.There are significant differences:OrR,OrL,ZvR,ZvL,TR,TL,ChR,ChL,GoRs,GoLs,PR,PL,GoR,GoL,ZpR,ZpL;?2?the coordinates of the seven anatomical landmarks are There are significant differences in the Y-axis and Z-axis directions:Ns,Prn,Sn,BcR,BcL,Po,Me;?3?The coordinate values??of the eight anatomical landmarks are significantly different in the X-axis direction:AcR,AcL,As,Bs,OrR,OrL,A,B.Another 15 anatomical landmarks had P value of?0.05,and the difference was not statistically significant.Conlusion1.By selecting the fitting region in the computer software to generate the centroid to determine the anatomical landmarks,the craniomaxillofacial anatomical landmarks can be fixedly positioned.2.Compared with the manual direct point method,the method of generating the centroid in the fitting region can effectively improve the stability and repeatability of the anatomical landmark positioning in the three-dimensional cephalometric measurement.3.Compared with the manual direct point method,although there are significant differences in 31 anatomical landmarks after the two groups of control tests,the reliability of the control group itself is low,so the difference between the two methods cannot be proved.The accuracy of the new method is high.In view of the high stability of the experimental group method,in order to prove the accuracy of the method,it is necessary to examine by examining more clinical cases and combining clinical efficacy observations.