Datum Collection.
This study was conducted in the West China Hospital of Stomatology of Sichuan University and was approved by the Ethics Committee of the West China School of Stomatology, Sichuan University (WCHSIRB-OT-2019-125). The patients included in training diagnose model consisted of 574 cases who visited the Department of Orthognathic and temporomandibular joint surgery, West China Hospital of Stomatology, Sichuan University during the period from January 2015 to August 2020. Exclusion criteria were missing teeth (except third molars), previous orthodontic and orthognathic treatment history, without CT scanning and dento-maxillofacial deformities caused by fracture and tumor. Their medical records before treatment were collected, including demographic information, extraoral photos, intraoral photos and cephalometric measurements. [1, 12]
The demographic characteristics in this study is shown in Table 1. We used 28 commonly features from these clinical records as input features (Supplementary document). The input features were preprocessed to ensure that all of them were quantified before being used for model training. The diagnosis of dento-maxillofacial deformities is determined by orthognathic surgeon (Dr. Luo) with 19 years of clinical experience. All experiments were performed in accordance with relevant guidelines and regulations. The diagnostic types of dento-maxillofacial deformities include maxillary development, mandibular development, maxillary deviation and mandibular deviation.
Table 1
The demographic characteristics in this study
N = 574
|
Male
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Female
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Age mean (SD)
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23.4 (7.2)
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26.3 (8.5)
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Gender
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203 (35.4%)
|
371 (64.6%)
|
Maxillary development
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Underdevelopment
|
201 (35%)
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Normal
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210 (36.6%)
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Overdevelopment
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163 (28.4%)
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Maxillary deviation
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Deviation
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208 (36.2%)
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Non-deviation
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366 (63.8%)
|
Mandibular development
|
Underdevelopment
|
175 (30.5%)
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Normal
|
138 (24%)
|
Overdevelopment
|
261 (45.5%)
|
Mandibular deviation
|
Deviation
|
253 (44.1%)
|
Non-deviation
|
321 (55.9%)
|
Diagnose models.
In this paper, we use binary relevance extreme gradient boosting (BR-XGBoost) algorithm to process the information of patients' dental and maxillofacial malformations, so as to realize intelligent diagnosis. Similar to the traditional supervised tree model algorithm based on boosting idea, XGBoost integrates several weak classifiers into a strong classifier through multiple rounds of iteration and residual fitting, which has good generalization performance and operation efficiency. In this paper, we model the diagnosis problem as single label two classification models. is the number of labels, and each label represents whether the patient has this kind of disease. For disease , set up a training set \({D_j}=\left\{ {\left( {{X_i},{y_i}} \right)|1 \leqslant i \leqslant n} \right\}\left( {1 \leqslant j \leqslant Q} \right)\), where is the sample serial number, is the patient's clinical symptom vector, and the variable \({y_i} \in \left\{ {1,0} \right\}\) indicates whether sample belongs to label . The XGBoost binary classification model is constructed based on \({D_j}\) training, so that the prediction result \({y_j}\) of label can be obtained. Then, multiple binary classifiers are combined into BR-XGBoost to output the multi label diagnose result \(Y=\left[ {{y_1},{y_2},...,{y_Q}} \right]\).
Considering the difference of patients' clinical symptoms, it is necessary to further study the generalization performance of the proposed algorithm. In this paper, the feature selection of each \(XGBoos{t_j}\)is based on the forward sequence selection method. For label , firstly, the importance ranking of all features is obtained based on XGBoost, then the features with the top ranking are added to the feature subset (initially empty set), and the cross-validation classification accuracy of the feature subset is calculated after each addition. If the classification accuracy is improved, the feature is retained, otherwise it is eliminated, and the optimal feature subset of label can be obtained by traversing all features. The performance of the model is not only affected by the training set, but also depends on the selection of its built-in parameters, that is, super parameters. In order to avoid the complexity and uncertainty of manual parameter adjustment, this paper calls the distributed asynchronous hyper parameter optimization module on the Pycharm platform. Based on the Bayesian optimization theory, the cross-validation method is adopted to optimize each XGBoost on the basis of determining the range of hyper parameters, so as to improve the model accuracy of BR-XGBoost.
To evaluate the performance of the artificial intelligence model, the following normal metrics are used.
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Accuracy: \(Accuracy=\frac{{TP+TN}}{{TP+FP+TN+FN}}\)
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Precision: \(Precision=\frac{{TP}}{{TP+FP}}\)
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Recall: \(Recall=\frac{{TP}}{{TP+FN}}\)
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Specificity: \(Specificity=\frac{{TN}}{{FP+TN}}\)
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F1score: \(F1score=2 \cdot \frac{{Precision \cdot Recall}}{{Precision+Recall}}\)
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AUC: Accuracy and area under the curve
TP: true positive; TN: true negative; FP: false positive; FN: false negative
Basis of surgical plan design.
The system assists orthognathic surgery design is built based on clinical experiences. We screened 19 indicators as restrictions for designing surgical plan. The normal interval of these restrictions is given according to clinical experience. Surgeons can also adjust the range based on personal experience to produce personalized solutions. The imported data were the three-dimensional coordinates of 25-mark points on the preoperative CT. The involved landmarks were shown in the Supplementary Information. The terminal occlusal relationship was recorded by the three-dimensional spatial relationship of three marks on the maxilla and the mandible. Six sets of data were used to accurately describe the three-dimensional movement of the maxilla, mandible and chin respectively according to the commonly used clinical methods. We randomly selected 50 patients from the aforementioned 574 patients and performed expert ratings on the automatic output surgical plan. The subjects included were all patients who had undergone bimaxillary surgery. The objective of the output surgical protocol was to correct the patient's diagnosed dento-maxillofacial deformities. The effectiveness and feasibility of the surgical plan were evaluated by three experienced maxillofacial surgeons. For unsatisfactory surgical plans, the final score will be given by experts after human-computer interaction.
Treatment plan model.
In this paper, the design of surgical scheme is determined based on artificial intelligence. We use the adaptive artificial bee colony (aABC) algorithm to calculate the maxillary movement, mandibular movement and mentum movement. Artificial bee colony algorithm is an intelligent optimization algorithm that simulates bee colony behavior. It was proposed by Karaboga in 2005. Because ABC algorithm has strong global, parallel and can better combine with other intelligent algorithms, it has attracted the attention of the majority of scientific researchers in recent years.
In this paper, the three-dimensional translation and rotation of each part in the surgical scheme constitute the solution space of the artificial bee colony algorithm. All possible solutions in the solution space are expressed by honey source, and the degree of honey source is measured by the value of fitness function. Bees can be divided into three types according to different division of labor: collecting bees, following bees and reconnaissance bees (collecting bees and following bees each account for half of the total number of bees, and the collecting bees corresponding to inferior honey sources are transformed into reconnaissance bees to search for new honey sources). The specific search for honey source is as follows:
1) Algorithm initialization. In a random way, an initial solution is generated according to the following formula, which is the honey source:
$$x_{{m,i}}^{{}}={L_i}+rand\left( {0,1} \right)\left( {{U_i} - {L_i}} \right)$$
1
where the position of each honey source is represented by \(x_{{m,i}}^{{}}\). \({U_i}\) and \({L_i}\) are the upper and lower bounds of the algorithm space. The number of honey sources is equal to the number of bees, and the number of honey source cyclic search is the number of optimization iterations.
2) The investigation bee found the honey source and measured the amount of honey (fitness value). The calculation formula of fitness value is:
$$fit\left( {{x_m}} \right)=\frac{{\text{1}}}{{J+\varepsilon }}$$
2
where, is the evaluation function, which is determined by the doctor preference.
3) Neighborhood search. Search for new honey sources through neighborhood search. If the new honey source fitness value is better than the current honey source fitness value, replace the honey source.
The neighborhood location search formula adopted by the classical artificial bee colony algorithm is:
$${v_{m,i}}=x_{{m,i}}^{{}}+{\varphi _{m,i}}\left( {x_{{m,i}}^{{}} - x_{{k,i}}^{{}}} \right)$$
3
It can be seen that the randomness of neighborhood search makes the classical artificial bee colony algorithm have strong exploration ability, but the development ability is poor, and there are some problems such as slow convergence speed and poor search accuracy. To solve this problem, this paper introduces the adaptive coefficient to improve the neighborhood location search equation of the classical artificial bee colony algorithm.
$$\begin{gathered} {v_{m,i}}={x_{m,i}}+u(t)({x_{j,i}} - {x_{k,i}})+\alpha {\psi _{m,i}}({V_{g,i}} - {x_{m,i}}) \hfill \\ \alpha =(1 - u(t)) \hfill \\ u(t)=1 - ran{d^{{{(1 - t/\hbox{max} cycle)}^2}}} \hfill \\ \end{gathered}$$
4
The global optimal solution under the current cycle is represented by ; \({\text{maxcycle}}\) is the maximum number of cycles; is the adaptive coefficient ; is current number of cycles. With the increase of the number of cycles of the algorithm, the weight between algorithm exploration and development is constantly changing. When the cycle starts, the algorithm has a high weight in exploration, and the global search ability is strengthened, so it is not easy to fall into local optimization; With the continuous increase of the, the value of the adaptive coefficient decreases gradually. At this time, the algorithm tends to develop the region guided by the global optimal solution, which improves the convergence speed and accuracy of the algorithm.
4) For the following bee, the calculated probability value selects the honey source and carries out neighborhood search to generate a new solution, and selects the honey source with better fitness value.
5) If no better honey source is found within the limited number of times, give up the honey source and randomly generate a new honey source.
6) Save the optimal honey source (global optimal solution) found by all bees, and judge the termination condition of the algorithm (maximum number of iterations). If the conditions are met, the optimal surgical scheme is returned and the algorithm is terminated. Otherwise, return to the first step to continue the algorithm.
The overall process of the Decision Support System is shown in Fig. 1.