A method for constructing three-dimensional face symmetry reference plane based on weighted shape analysis algorithm / 北京大学学报(医学版)

OBJECTIVE@#To establish a novel method based on three-dimensional (3D) shape analysis and weighted Procrustes analysis (WPA) algorithm to construct a 3D facial symmetry reference plane (SRP), automatically assigning weight to facial anatomical landmarks. The WPA algorithm suitability for commonly observed clinical cases of mandibular deviation were analysed and evaluated.@*METHODS@#Thirty patients with mandibular deviation were recruited for this study. The 3D facial SRPs were extracted independently based on original-mirror alignment method. Thirty-two anatomical landmarks were selected from the overall region by three times to obtain the mean coordinate. The SRP of experimental groups 1 and 2 were using the standard Procrustes analysis (PA) algorithm and WPA algorithm, respectively. A reference plane defined by experts based on regional iterative closest point (ICP) algorithm, served as the ground truth. Three experts manually selecting facial regions with good symmetry for original model, and common region was included in the study. The angle error values between the SRP of WPA algorithm in the experimental group 1 and the truth plane were evaluated in this study, and the SRP of PA algorithm of experimental group 2 was calculated in the same way. Statistics and measurement analysis were used to comprehensively evaluate the clinical suitability of the WPA algorithm to calculate the SRP. A paired t-test analysis (two-tailed) was conducted to compare the angles.@*RESULTS@#The average angle error between the SRP of WPA algorithm and the ground truth was 1.53°±0.84°, which was smaller than that between the SRP of PA and the ground truth (2.06°±0.86°). There were significant differences in the angle errors among the groups (P < 0.05). For the patients with severe mandibular deviation that the distance between pogonion and facial midline greater than 12 mm, the average angle error of the WPA algorithm was 0.86° smaller than that of the PA algorithm.@*CONCLUSION@#The WPA algorithm, based on weighted shape analysis, can provide a more adaptable SRP than the standard PA algorithm when applied to mandibular deviation patients and preliminarily simulate the diagnosis strategies of clinical experts.

Comparison of midsagittal reference plane in PA cephalogram and 3D CT / 대한치과교정학회지

OBJECTIVE: The aim of this study is to find the most helpful midsagittal reference plane for diagnosis in PA cephalometry compared with 3D CT. METHODS: The subjects consisted of 25 adults who showed no facial asymmetry by gross inspection. 3D CT and posteroanterior cephalogram of the subjects were taken. To find the most helpful midsagittal reference plane in PA cephalometry, we considered five kinds of midsagittal planes from which the distances to five landmarks were measured and compared the result with that of 3D CT. The midsagittal plane for 3D CT was determined by the landmarks Nasion, Sella and Basion. RESULTS: PA measurements using the midsagittal reference plane on a perpendicular plane lying through the midpoint of the right and left latero-orbitales was closest to those of 3D CT. CONCLUSIONS: It was considered that latero-orbitale perpendicular could be used as the helpful midsagittal reference plane to assess facial asymmetry in PA cephalometry.

Validity of midsagittal reference planes constructed in 3D CT images / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the validity of midsagittal reference (MSR) planes constructed in maxillofacial 3D images. METHODS: Maxillofacial computed tomography (CT) images were obtained in 36 normal occlusion individuals who did not have apparent facial asymmetry, and 3D images were reconstructed using a computer software. Six MSR planes (Cg-ANS-Ba, Cg-ANS-Op, Cg-PNS-Ba, Cg- PNS-Op, FH perpendicular (Cg, Ba), FH perpendicular (Cg, Op)) were constructed using the landmarks located in the midsagittal area of the maxillofacial structure, such as Cg, ANS, PNS, Ba and Op, and FH plane constructed with Po and Or. The six pairs of landmarks (Z, Fr, Fs, Zy, Mx, Ms), which represent right and left symmetry in the maxillofacial structure, were selected. Statistically significant differences of the right and the left measurements were examined through t-test, and the difference of the right and the left measurement was compared among the six MSR planes. RESULTS: The distances from the right and the left landmarks in each pair to each MSR plane did not show a statistically significant difference. The reproducibility of the landmark identification was excellent. CONCLUSION: All the six planes constructed in this study can be used as a MSR plane in maxillofacial 3D analysis, particularly, the planes including Cg and ANS.

Formulation of a reference coordinate system of three-dimensional head and neck images: Part II. Reproducibility of the horizontal reference plane and midsagittal plane / 대한치과교정학회지

This study was performed to investigate the reproducibility of the horizontal and midsagittal planes, and to suggest a stable coordinate system for three-dimensional (3D) cephalometric analysis. Eighteen CT scans were taken and the coordinate system was established using 7 reference points marked by a volume model, with no more than 4 points on the same plane. The 3D landmarks were selected on V works (Cybermed Inc., Seoul, Korea), then exported to V surgery (Cybermed Inc., Seoul, Korea) to calculate the coordinate values. All the landmarks were taken twice with a lapse of 2 weeks. The horizontal and midsagittal planes were constructed and its reproducibility was evaluated. There was no significant difference in the reproducibility of the horizontal reference planes. But, FH planes were more reproducible than other horizontal planes. FH planes showed no difference between the planes constructed with 3 out of 4 points. The angle of intersection made by 2 FH planes, composed of both Po and one Or showed less than 1 degrees difference. This was identical when 2 FH planes were composed of both Or and one Po. But, the latter cases showed a significantly smaller error. The reproducibility of the midsagittal plane was reliable with an error range of 0.61 to 1.93 degrees except for 5 establishments (FMS-Nc, Na-Rh, Na-ANS, Rh-ANS, and FR-PNS). The 3D coordinate system may be constructed with 3 planes; the horizontal plane constructed by both Po and right Or; the midsagittal plane perpendicular to the horizontal plane, including the midpoint of the Foramen Spinosum and Nc; and the coronal plane perpendicular to the horizontal and midsagittal planes, including point clinoidale, or sella, or PNS.

Quantitative Analysis of Diabetic Macular Edema after Laser Photocoagulation

PURPOSE: Diabetic macular edema is one of major causes leading to visual loss and it is difficult to be quantified. We investigated a volumetric quantification of retinal thickness change before and after focal laser photocoagulation with Heidelberg Retina Tomograph (HRT). METHODS: Ten patients who were diagnosed as diabetic retinopathy with clinically significant macular edema (CSME) in only one eye and treated with focal laser photocoagulation were studied. The opposite eyes which had no CSME were studied as control group. In the eyes which had CSME, the volume above reference plane (VARP) bounded by three consecutive circle centered at the fovea (diameter 1, 2, and 3 mm) were measured. The retinal thickness of control group was also measured with the same method. We performed focal laser photocoagulation for the eyes which had CSME and measured VARP at 1, 2, and 3 months after laser treatment. RESULTS: Three months after laser treatment, the VARP of treated eyes measured in each diameter was significantly decreased, however, there was no significant difference in control group. There was no significant difference in visual acuity change between before and 3 months after laser treatment. CONCLUSION: From the above results, we concluded that HRT could be used to quantify the change of diabetic macular edema before and after laser treatment.

Cephalometric norms of the hard tissues of Korean for orthognathic surgery

This study was performed to evaluate hard tissue cephalometric norms for Korean adults which can be implemented in surgical orthodontic treatment planning using selected horizontal reference plane especially for Koreans (Male: SN-7.5degreeC, Female: SN-9.0degreeC) and a simplified analytical method. 70 males and 70 females consisting of freshmen of Yonsei University from 1996 to 1997 and students from the Dental College of Yonsei University were chosen according to clinical examination and cephalometric analysis. The samples had normal profiles, normal anteroposterior skeletal relationship(ANB angle of 0degreeC to 4degreeC and Wits appraisal of -4.0mm to 0mm) , and Class I molar and canine relationship. They had no missing or supernumerary teeth and had no experience of orthodontic or prosthetic treatment. After the selection of 23 landmarks and the construction of horizontal and vertical reference lines, 22 skeletal and 12 dental measurements were taken. These consisted of vertical and horizontal linear measurements and angular measurements. The results were as follows. 1. Mean and standard deviation of the measurements were calculated for males and females. 2. Most of the skeletal vertical measurements, and maxillary and mandibular length were bigger in males than females. Whereas anterior facial height ratio(N-ANS/ANS-Me) as well as maxillary and mandibular antero-posterior position in relation to the vertical reference line(N-perpendicular) showed no signigicant difference between sexes. 3. Maxillary and mandibular dental antero-posterior position in relation to the vertical reference line(N-perpendicular) showed no significant difference between sexes. 4. The upper incisor show(U1-Stms) was 2.1+/-1.7mm in males and 3.3+/-1.7mm in females. In this study, hard tissue cephalometric norms of Korean adults for orthognathic surgery were obtained.

Cephalometric norms of the soft tissues of Korean for orthognathic surgery

This study was performed to evaluate soft tissue cephalometric norms for Korean adults which can be implemented in surgical orthodontic treatment planning using selected horizontal reference plane especially for Koreans (Male: SN-7.5degreeC, Female: SN-9.0degreeC) and a simplified analytical method. 70 males and 70 females consisting of freshmen of Yonsei University from 1996 to 1997 and students from the Dental College of Yonsei University were chosen according to clinical examination and cephalometric analysis. The samples had normal profiles, normal anteroposterior skeletal relationship(ANB angle of 0degreeC to 4degreeC and Wits appraisal of -4.0mm to 0mm), and Class I molar and canine relationship. They had no missing or supernumerary teeth and had no experience of orthodontic or prosthetic treatment. After the selection of 15 soft tissue landmarks and the construction of horizontal and vertical reference lines, 25 measurements were taken. These consisted of vertical and horizontal linear measurements and angular measurements. The results were as follows. 1. Mean and standard deviation of the measurements were calculated in males and females. 2. Vertical measurements were comparably bigger in males than females whereas anterior facial height ratio(sN-Sn/Sn-sMe) and lower anterior facial height ratio(Sn-Stms/Stmi-sMe) showed no significant difference between sexes. 3. Most of the horizontal measurements in relation to the vertical reference line(G-perpendicular) showed no significant difference between sexes. 4. Nasofacial angle, columellar angle, nasolabial angle and facial contour angle showed no significant difference between sexes. 5. The upper and lower lip were positioned about -1.0+/-2.0mm and +1.0+/-2.0mm in relation to the Ricketts' esthetic line in both sexes. In this study, soft tissue cephalometric norms of Korean adults for orthognathic surgery were obtained.

Evaluation of Reference Planes Related to Wits Appraisal Measurement / 中国医师杂志

Objective To investigate the reliability and validity of three reference planes used in Wits appraisal measurement in evaluation of sagittal jaw relationship. Methods Lateral cephalo-radiography was performed before and after treatment in 25 patients with class Ⅱ division 1 of four premolars extraction. Wits appraisals were measured using the functional occlusal plane(FOP), bisected occlusal plane(BOP), and maxillary-mandibular bisector (MMB), respectively. The effect of different reference planes on Wits appraisals was analyzed. Results FOP and BOP showed a statistically significant change in their cant after treatment(P0.05). MMB Wits had the highest correlation with ANB angle (r=0.79, P

The Relationship between the Mean Height of Contour of the Retinal Surface at the Temporal Disc Margin and the Reference Height in Analyzing Optic Disc using Heidelberg Retina Tomograph

The relationship between the amount of posterior displacement of the retinal surface at the temporal disc margin and the reference height(HRef)in analyzing optic disc using Heidelberg Retina Tomograph(HRT;Heidelberg Engineering, Heidelberg, Germany)was evaluated. The displacement was measured as mean height of contour(MHC)in the temporal 40degrees C segment(20degrees C superior and 20degrees C inferior to the horizontal midline)of optic disc. HRef is a value representing the location of the standard reference plane. The accordances of HRef and stereometric parameters between right and left disc were also evaluated. MHC in the temporal 40 degrees C and nasal 40 degrees C segment, HRef, and stereometric parameters of optic disc were measured with the HRT in 244 eyes of 122 subjects. HRef was 0.376+/-0.099 mm in the right disc and 0.385+/-0.090 mm in the left disc. There was good correlation between HRef and MHC in the temporal 40degrees C segment(r=0.97, p<0.01), but poor in the nasal 40 degrees C segment(r=0.29, p<0.01). The accordances of HRef and stereometric parameters increased as the difference of MHC in the temporal 40degrees C segment between right and left disc decreased. HRef was affected by the amount of posterior displacement of the retinal surface at the temporal disc margin, which occurs in instances such as a tilted disc. We should find the method to adjust stereometric parameters to the amount of disc tilt.

Quantification of Diabetic Macular Edema with Heidelberg Retina Tomograph

Diabetic macular edema is a major cause of visual loss and it is difficult to be quantified.We investigated a method of assessment and volumetric quantification of diabetic macular edema with Heidelberg Retina Tomograph[HRT].Ten normal eyes of control group and 20 eyes with diabetic patients were studied.In 20 diabetic patients, 10 patients had macular edema and 10 patients had no macular edema. Macular edema was defined as any visible macular thickening within a circle centered at the fovea with 6mm in diameter. With HRT, the volumes above reference plane[VARP]bound by three consecutive circles centered at the fovea [diameter, 1, 2, and 3mm ]were measured. Measurements were repeated three times, and mean measurements were used for the analysis. Diabetic eyes with macular edema had statistically greater VARP than diabetic eyes without edema[p0.05]. The sensitivity of HRT was 90%, and the specificity was 100%. The VARP measured using HRT was found to be linearly correlated with visual acuity expressed on a logMAR scale[p<0.05]. From the above results, we concluded that HRT could identify diabetic macular edema by volumetric analysis and indicated a good relationship of volumetric changes with visual acuity.

A study on horizontal reference planes in lateral cephalogram in Korean children / 대한치과교정학회지

Various types of horizontal reference planes are used for diagnosis, treatment planning and evaluation of treatment results. But these reference planes lack accuracy and repro- ducibility, and are mainly for Caucasian. Unlike the adult patients who have completed growth, the horizontal reference planes for growing children may change continuously during growth, Therefore this must be considered in selecting the horizontal reference plane. The purpose of this study was to investigate the angle formed by the Sella-Nasion(SN) plane and Frankfort-Horizontal(FH) plane and evaluate the angle formed by FH plane and other horizontal reference planes in relation to different skeletal maturity and malocclusion types. 540 subjects with no orthodontic treatment history were chosen, and hand wrist X-rays and lateral cephalometric X-rays were taken, According to SMA(Skeletal maturity Assessment)of hand -wrist X-rays, the subjects were classified into 3 skeletal maturity groups ; SMI 1-2 for group A, SMI 5-7 for group B and SMI 8-11 for group C. A second classification was made according to cephalometric analysis of lateral cephalograms. The subjects were classified into 3 malocclusion group ; Skeletal Class I,II and III malocclusion group. 10 measurements were evaluated. The results were as follow. 1. The angle formed by the SN plane and FH plane showed no difference among skeletal maturity groups, malocclusion groups, and between sexes. 2. The angles formed by the SN plane and FH plane were 8.27degrees+/-2.31degrees for males and 8.59degrees+/-2.24degrees for females. The average value for females and males was 8.42degrees+/-2.28degrees. 3. The angle formed by the FH plane and palatal plane was almost constant showing no difference among skeletal maturity groups, malocclusion groups, and between sexes( 1.0 9degrees+/- 3.21degrees).

A study on horizontal reference planes in lateral cephalogram in Korean adults / 대한치과교정학회지

The purpose of this study was to investigate the angle formed by the Sella-Nasion(SN) plane and Frankort-Horizontal(FH) plane and evaluate the correlation and difference of the FH plane to other horizontal reference planes. Through this study we hope to present a basis for selecting a horizontal reference plane which can be implemented in cephalometric studies and in surgical orthodontic treatment planning. 600 subjects were chosen following a clinical examination and lateral cephlometric X-rays were taken. According to cephalometric analysis the subjects were classified into 3 groups; Skeletal Class I malocclusion or normal occlusion group(male 50, female 50), Skeletal Class II malocclusion group(male 50, female 65) and Skeletal Class III malocclusion group(male 50, female 50). The results were as follows. 1. The angle formed by the SN plane and FH plane showed no difference among the malocclusion groups, but there was a significant sex difference. For males the angle measured was 7.47degrees+/-2.40degrees whereas for females it was 8.93degrees+/-2.72degrees. 2. The angle formed by the SN plane or FH plane and Mandibular plane was higher in females for all malocclusion groups. This angle in the Skeletal Class I malocclusion group was 1 awer than in the other two groups. 3. There was no difference among the sexes or malocclusion groups con ,idering the angle formed by the FH plane and Palatal plane. 4. The gonial angle in the Skeletal Class III malocclusion group was higher than in the Skeletal Class I and Class II malocclusion groups- in both sexes.