Stable Landmark Research Articles

The apex of the deep cartilage is a stable landmark to position the femoral tunnel during remnant-preserving anterior cruciate ligament reconstruction.

The aim of this retrospective cohort study was to investigate whether the apex of the deep cartilage (ADC) could help surgeons position the femoral tunnel accurately in remnant-preserving anterior cruciate ligament (ACL) reconstruction (ACLR). In the current retrospective cohort study, a total of 134 patients who underwent ACLR between 2016 and 2020 were included. The femoral tunnel position was located using ADC as the landmark. The patients were divided into two groups: the remnant-preserving group (RP group, n = 68) underwent remnant-preserving ACLR, and the nonremnant group (NRP group, n = 66) underwent traditional ACLR with remnant removal. Postoperatively, the femoral tunnel position was evaluated on 3D-CT. The length from the ADC to the shallow cartilage margin (L) and to the centre of the femoral tunnel (l) and the length from the centre of the femoral tunnel to a low cartilage ratio in the direction from high to low (H) were measured. The l/L values of the RP and NRP groups were both 0.4 ± 0.1 after rounding (n.s.), and the H values were 9.3 ± 1.6mm and 9.3 ± 1.7mm, respectively (n.s.). There was no significant difference in l/L or H between the two groups. The estimation plot also showed high consistency of H and l/L of the two groups. The inter- and intraobserver reliability of I, L, l/L, and H were almost perfect. The apex of the deep cartilage is a good landmark for positioning the femoral tunnel in remnant-preserving ACL reconstruction. Level III.

Comparative analysis for variation of skeletal and dental parameters in bilateral cleft palate in central India population – A Nemoceph study

Introduction: An area of dentistry called orthodontics focuses on repositioning crooked teeth and regulating facial development. Orthodontists and oral surgeons use cephalometric analysis as a planning tool for their patient care. Conventional film-based radiography equipment has been replaced with direct digital devices, which have advantages such as reduced patient radiation exposure, immediate radiographic image generation, the removal of the need for darkrooms, and simple image sharing. The second-most typical craniofacial abnormality that results in birth abnormalities is cleft lip and palate. Such patients frequently do not receive cephalometric testing because of their hypoplastic growth and limited development. Research is needed to help plan a standard treatment regimen, perform orthognathic operations, and use a low-radiation analysis technique. Objectives: To evaluate skeletal and dental parameters for cleft lip and palate using Down analysis, Steiner's analysis, and Tweed's analysis using Nemoceph. Methods: Around 50 cases from cleft lip and palate and non-cleft lip and palate will be selected from the orthodontics department of Sharad Pawar Dental College and Hospital. Steiner's, Down's, and Tweed's analyses will be evaluated using Nemoceph. Further analysis will be conducted using the observational data from the readings. There will be millimetre-based measurements made. Comparative analysis will be done with one-way ANOVA and post hoc statistics and regression analysis will be done for association of demographic variables. Expected outcomes: This study will use the nasion as a stable landmark to evaluate point A in cleft lip and palate patients, making it easier to perform normal cephalometric analysis. This will enable the evaluation of the probable position of point A for performing cephalometric analysis in orthodontics.

Characteristic changes of the palatal rugae following orthodontic treatment

BackgroundBecause of the individuality of the palatal rugae, they are applicable for human identification purposes the same as the fingerprints. Therefore, it is important to assess the effect of different factors on rugae characteristics. We assessed the characteristic changes of the palatal rugae following extraction and expansion during orthodontic treatments. Before and after orthodontic treatment dental casts of 30 patients were scanned by 3Shape Trios 3D intraoral scanner, and superimposed in Geomagic X 2018 software. Displacement of 13 reference points was analyzed in three dimensions. The length of the palatal rugae was also measured. SPSS version 22.0 was applied for data analysis, using independent t test, sample t test, and chi-square test.ResultsThe alterations in the mean palatal rugae length were significant in the first right and third right ridges after extraction, and right and left second ridges after expansion treatment (P < 0.05). Changes in coordinates in the X, Y, and Z axes were significant at 8 points on the rugae after extraction, and 5 points after expansion treatment (P < 0.05). The changes in the sum of means of displacements were significant at all 13 points after extraction and expansion treatments (P < 0.05).ConclusionsThe palatal rugae do not remain stable during expansion and extraction orthodontic treatments. Some changes occurred in length, and the most medial and most lateral points on each ridge were displaced. The length of the incisive papilla did not change during treatment; thus, it can serve as a stable landmark. If we consider palatal rugae as an individual landmark, we can refer the patients after orthodontic treatment for scanning of their palatal rugae to document their post treatment pattern; but it should be noted that treatment relapse may change it again.

Comparative analysis of sex-based variations in mental foramen using cone-beam computed tomography

Introduction: The use of morphological features of the mandible is a common approach used by anthropologists and forensic dentists in the determination of sex. Among many anatomical landmarks of the skull, the mental foramen (MF) is a stable landmark on the mandible. Aim of the Study: The aim of the study was to analyze the sex-based variations of MF using cone-beam computed tomography (CBCT). Materials and Methods: This retrospective study evaluated 60 CBCT scans, retrieved from the radiological archives of our institution. MF was identified in the sagittal section of both the right and left sides. Parameters such as width of MF (W), the height of MF (H), the distance from superior border of MF to the lower border of the mandible (SMF-LM), the distance from inferior border of MF to the lower border of the mandible (IMF-LM), and the interforaminal distance (IFD) were evaluated and compared between the two groups. Statistical Analysis: The data obtained were analyzed using the SPSS 27 version software. Paired t-test was done for intragroup analysis; unpaired t-test was done for intergroup analysis. Results: The SMF-LM distance, IMF-LM distance, and the IFD were significantly greater in males compared to females. Conclusion: Based on the results of this study, the distance from MF to the lower border of the mandible and the IFD showed clear sexual dimorphism and can be used as an effective tool for sex discrimination.

The role of the parahippocampal cortex in landmark-based distance estimation based on the contextual hypothesis.

Parahippocampal cortex (PHC) is a vital neural bases in spatial navigation. However, its functional role is still unclear. "Contextual hypothesis," which assumes that the PHC participates in processing the spatial association between the landmark and destination, provides a potential answer to the question. Nevertheless, the hypothesis was previously tested using the picture categorization task, which is indirectly related to spatial navigation. By now, study is still needed for testing the hypothesis with a navigation-related paradigm. In the current study, we tested the hypothesis by an fMRI experiment in which participants performed a distance estimation task in a virtual environment under three different conditions: landmark free (LF), stable landmark (SL), and ambiguous landmark (AL). By analyzing the behavioral data, we found that the presence of an SL improved the participants' performance in distance estimation. Comparing the brain activity in SL-versus-LF contrast as well as AL-versus-LF contrast, we found that the PHC was activated by the SL rather than by AL when encoding the distance. This indicates that the PHC is elicited by strongly associated context and encodes the landmark reference for distance perception. Furthermore, accessing the representational similarity with the activity of the PHC across conditions, we observed a high similarity within the same condition but low similarity between conditions. This result indicated that the PHC sustains the contextual information for discriminating between scenes. Our findings provided insights into the neural correlates of the landmark information processing from the perspective of contextual hypothesis.

The apex of the deep cartilage is a stable landmark to evaluate the femoral tunnel position in ACL reconstruction.

To develop a simple and effective method for evaluating the femoral tunnel position using the apex of the deep cartilage (ADC) as the landmark. A total of 52 patients who underwent arthroscopic ACL reconstruction were recruited between June and September 2021. The femoral tunnel was placed on the central point of the anteromedial footprint with an accessory anteromedial and a high anterolateral portal. Then, the length from the ADC to the shallow cartilage margin (L1) and to the center of the femoral tunnel (l1), as well as the center to the low cartilage margin (H1, intraoperative height), was measured under arthroscopy and on postoperative CT scans (L2, l2 and H2). Moreover, intraoperative and postoperative cartilage ratios were equivalent to l1/L1 and l2/L2, respectively. Linear regression, Pearson correlation and Bland-Altman analysis were performed to evaluate the consistency between these two measurements of cartilage ratio (l/L) and height (H). The mean age at the time of surgery was 28.7years; 42 patients were male, and 17 patients were hurt in the left knee among 52 patients. The intraoperative cartilage ratio was 0.37 ± 0.04, and the height was 8.1 ± 1.1mm with almost perfect inter-observer reproducibility. After the surgery, the cartilage ratio and height were measured as 0.39 ± 0.04 and 8.2 ± 1.3mm on 3D-CT, respectively, with almost perfect intra- and inter-observer reproducibility. Significant positive correlations and linear regression were detected in the cartilage ratio (r = 0.844, p < 0.001), and height (r = 0.926, p < 0.001) intraoperatively and postoperatively. The Bland-Altman plot also showed excellent consistency between arthroscopy and 3D-CT. The ADC is a good landmark in the assessment of femoral tunnel position, with excellent consistency between intraoperative arthroscopic measurements and postoperative 3D-CT. gov Identifier: NCT04937517. Level III.

Landmark-modulated directional coding in postrhinal cortex.

Visual landmarks can anchor an animal’s internal sense of orientation to the external world. The rodent postrhinal cortex (POR) may facilitate this processing. Here, we demonstrate that, in contrast to classic head direction (HD) cells, which have a single preferred orientation, POR HD cells develop a second preferred orientation when an established landmark cue is duplicated along another environmental wall. We therefore refer to these cells as landmark-modulated–HD (LM-HD) cells. LM-HD cells discriminate between landmarks in familiar and novel locations, discriminate between visually disparate landmarks, and continue to respond to the previous location of a familiar landmark following its removal. Rats initially exposed to different stable landmark configurations show LM-HD tuning that may reflect the integration of visual landmark information into an allocentric HD signal. These results provide insight into how visual landmarks are integrated into a framework that supports the neural encoding of landmark-based orientation.

Palatal rugae: Stable or variable

Forensics has always considered Palatal rugae as a stable landmark for identification in cases of mishap which needs forensic intervention. Many previous studies have claimed that palatal design and structure is not altered during growth as its position protects it from external trauma. But this theory can now be challenged with studies showing otherwise as a number of people are undergoing Orthodontic treatment to enhance their aesthetics. The question that now arises is that can palatal rugae be actually considered a stable landmark? How orthodontic treatment alters the structure of rugal area and how tooth movement affects the stability of rugae. This article throws light on significant effects of tooth movement on palatal rugae reported by various studies. Keywords: Palatal rugae, Orthodontic treatment, Stability, Variability, Landmark.

Feasibility of Optical Surface-Guidance for Position Verification and Monitoring of Stereotactic Body Radiotherapy in Deep-Inspiration Breath-Hold

BackgroundReductions in tumor movement allow for more precise and accurate radiotherapy with decreased dose delivery to adjacent normal tissue that is crucial in stereotactic body radiotherapy (SBRT). Deep inspiration breath-hold (DIBH) is an established approach to mitigate respiratory motion during radiotherapy. We assessed the feasibility of combining modern optical surface-guided radiotherapy (SGRT) and image-guided radiotherapy (IGRT) to ensure and monitor reproducibility of DIBH and to ensure accurate tumor localization for SBRT as an imaging-guided precision medicine.MethodsWe defined a new workflow for delivering SBRT in DIBH for lung and liver tumors incorporating SGRT and IGRT with cone beam computed tomography (CBCT) twice per treatment fraction. Daily position corrections were analyzed and for every patient two points retrospectively characterized: an anatomically stable landmark (predominately Schmorl’s nodes or spinal enostosis) and a respiratory-dependent landmark (predominately surgical clips or branching vessel). The spatial distance of these points was compared for each CBCT and used as surrogate for intra- and interfractional variability. Differences between the lung and liver targets were assessed using the Welch t-test. Finally, the planning target volumes were compared to those of free-breathing plans, prepared as a precautionary measure in case of technical or patient-related problems with DIBH.ResultsTen patients were treated with SBRT according this workflow (7 liver, 3 lung). Planning target volumes could be reduced significantly from an average of 148 ml in free breathing to 110 ml utilizing DIBH (p < 0.001, paired t-test). After SGRT-based patient set-up, subsequent IGRT in DIBH yielded significantly higher mean corrections for liver targets compared to lung targets (9 mm vs. 5 mm, p = 0.017). Analysis of spatial distance between the fixed and moveable landmarks confirmed higher interfractional variability (interquartile range (IQR) 6.8 mm) than intrafractional variability (IQR 2.8 mm). In contrast, lung target variability was low, indicating a better correlation of patients’ surface to lung targets (intrafractional IQR 2.5 mm and interfractional IQR 1.7 mm).ConclusionSBRT in DIBH utilizing SGRT and IGRT is feasible and results in significantly lower irradiated volumes. Nevertheless, IGRT is of paramount importance given that interfractional variability was high, particularly for liver tumors.

Learning spatial-temporal deformable networks for unconstrained face alignment and tracking in videos

In this paper, we propose a spatial-temporal deformable networks approach to investigate both problems of face alignment in static images and face tracking in videos under unconstrained environments. Unlike conventional feature extractions which cannot explicitly exploit augmented spatial geometry for various facial shapes, in our approach, we propose a deformable hourglass networks (DHGN) method, which aims to learn a deformable mask to reduce the variances of facial deformation and extract attentional facial regions for robust feature representation. However, our DHGN is limited to extract only spatial appearance features from static facial images, which cannot explicitly exploit the temporal consistency information across consecutive frames in videos. For efficient temporal modeling, we further extend our DHGN to a temporal DHGN (T-DHGN) paradigm particularly for video-based face alignment. To this end, our T-DHGN principally incorporates with a temporal relational reasoning module, so that the temporal order relationship among frames is encoded in the relational feature. By doing this, our T-DHGN reasons about the temporal offsets to select a subset of discriminative frames over time steps, thus allowing temporal consistency information memorized to flow across frames for stable landmark tracking in videos. Compared with most state-of-the-art methods, our approach achieves superior performance on folds of widely-evaluated benchmarking datasets. Code will be made publicly available upon publication.

Distance Between the Most Prominent Labial Surface of Maxillary Central Incisors to the Posterior Limit of Incisive Papilla in Various Arch Forms

Introduction: Arranging artificial teeth has always been a challenging work since edentulous alveolar ridges are in a constant verge of physiological resorptive changes. Incisive papilla is a reliable biometric guide which can be used as a reference for arrangement of anterior teeth, since it is a stable intraoral anatomical landmark unless surgically modified.&#x0D; Objective: This study was conducted to determine the mean distance between the most prominent labial surface of maxillary central incisors to the posterior limit of incisive papilla in various arch forms.&#x0D; Materials and Methods: The study was carried out among 170 undergraduate students of BPKIHS, after obtaining ethical clearance from Institutional Review Committee, BPKIHS. Maxillary impressions were made with alginate impression materials and casts were poured with dental stone. Distance from the posterior limit of incisive papilla to maximum convexity of central incisor (Papillo-Incisal Distance, PID) was measured with a Digital Vernier caliper with a precision of 0.01mm. The arch forms were analyzed and classified into ovoid, tapering and squarish arch, subjectively based on morphological parameters. The intra-examiner reliability of the measurement was tested in 17 casts calculating Cronbach’s Alpha. Pearson Chi-square test was applied to explore the relation of the arch forms with age and gender. One-way ANOVA was used to check the association between the mean PID between with different arch forms.(p value = 0.05)&#x0D; Results: The mean distance from the labial surface of maxillary central incisors to the posterior limit of incisive papilla was 11.58±1.32 mm. The mean papillo-incisal distance varied with respect to different arch forms which was statistically significant (P&lt;0.05). The mean PID of oval, squarish and tapering arch forms were 11.86 mm, 10.82 mm and 11.93 mm respectively.&#x0D; Conclusion: Incisive papilla is a valuable starting point in the preliminary location of maxillary incisors during fabrication of dentures. The suggested mean PID for arranging central incisors is 11.58 mm.

Rugoscopy: An Adjunctive Diagnostic Tool for Malocclusion?

Context:Palatal rugae (PR) are regularly used in forensic dentistry for identification of individuals. PR gets established early in intra-uterine life and remains stable thereafter, thus considered as a stable land mark. Correlation of PR with different occlusal relations may aid in diagnosing malocclusions at an early stage.Aims: Identification of distinctive features of PR in different classes of dental malocclusion and to identify the most common pattern in Malaysian students. To explore probability of PR as an adjunctive tool for categorizing malocclusions.Method and Material: PR in casts of 70 Malaysian students aged 19–23 years demonstrating Class I, Class II and Class III malocclusions were studied. The number, pattern, orientation and strength of rugae both on left and right side of mid-palatal raphe were determined and statistically analysed by anova test for different categories of malocclusions.Results:Class I malocclusion showed similar bilateral orientation of all the parameters when compared to other two types of malocclusion. PR in all malocclusions showed a predominantly wavy pattern but forking-diverging type was mainly in fragmentary rugae. The number of primary, secondary and fragmentary rugae was greatest in number in Class II malocclusion when compared to class I and class III.Conclusions: This study provides evidence of a distinct pattern of PR in Class I and Class III patients and but to ascertain its statistical significance, further research may be conducted with a larger sample size.

The development of the cloaca in the human embryo.

Subdivision of cloaca into urogenital and anorectal passages has remained controversial because of disagreements about the identity and role of the septum developing between both passages. This study aimed to clarify the development of the cloaca using a quantitative 3D morphological approach in human embryos of 4–10 post‐fertilisation weeks. Embryos were visualised with Amira 3D‐reconstruction and Cinema 4D‐remodelling software. Distances between landmarks were computed with Amira3D software. Our main finding was a pronounced difference in growth between rapidly expanding central and ventral parts, and slowly or non‐growing cranial and dorsal parts. The entrance of the Wolffian duct into the cloaca proved a stable landmark that remained linked to the position of vertebra S3. Suppressed growth in the cranial cloaca resulted in an apparent craniodorsal migration of the entrance of the Wolffian duct, while suppressed growth in the dorsal cloaca changed the entrance of the hindgut from cranial to dorsal on the cloaca. Transformation of this ‘end‐to‐end’ into an ‘end‐to‐side’ junction produced temporary ‘lateral (Rathke's) folds’. The persistent difference in dorsoventral growth straightened the embryonic caudal body axis and concomitantly extended the frontally oriented ‘urorectal (Tourneux's) septum’ caudally between the ventral urogenital and dorsal anorectal parts of the cloaca. The dorsoventral growth difference also divided the cloacal membrane into a well‐developed ventral urethral plate and a thin dorsal cloacal membrane proper, which ruptured at 6.5 weeks. The expansion of the pericloacal mesenchyme followed the dorsoventral growth difference and produced the genital tubercle. Dysregulation of dorsal cloacal development is probably an important cause of anorectal malformations: too little regressive development may result in anorectal agenesis, and too much regression in stenosis or atresia of the remaining part of the dorsal cloaca.

Mental foramen: A predictor of age and gender and guide for various procedures

Background: The distance from the inferior border of mental foramen (MF) to lower border of mandible remains constant throughout the life. Considering this fact the present study was carried out to determine role of MF in age and gender estimation and also its importance in planning various treatments. Aims and Objective: (1) To determine the most common type and shape of MF 2) To measure the height of the mandibular body (H), the distance between the superior margin of the MF to the alveolar crest (SM-AC), the distance between the superior margin of the MF to the inferior border of the mandible (SM-IB), the distance between the inferior margin of the MF to the inferior border (IM-IB) on the right side and left side. (3) To compare the above measurements for age and gender determination. (4) To determine effect of various factors on above measurements (5) to evaluate whether any significant difference in measurement occurs on right and left side. (6) To derive a regression equation for age estimation. Materials and Methods: A total of 300 Orthopantomogram were studied. Measurements such as H, SM-AC, SM-IB and IM-IB were carried out on both sides on type II MF in males and females in all the six age groups. Statistical analysis was carried using IBM SPSS version 24 to determine differences in measurements and linear regression analysis was carried out to determine age of individuals. Result: The most common appearance of MF was type II and shape was oval. Statistically significant differences occurred in measurements using which regressive equation for age estimation was derived for males & females. Conclusion: MF, being a stable landmark in mandible, serves as a good indicator for the determination of age and gender. Hence, using certain measurements related to MF, it can help in determining the age of the individual. Further, its position and distance from the alveolar crest serve as a guide for orthognathic surgeries, implant placement, and pre-prosthetic surgery.

Can personality predict individual differences in brook trout spatial learning ability?

While differences in individual personality are common in animal populations, understanding the ecological significance of variation has not yet been resolved. Evidence suggests that personality may influence learning and memory; a finding that could improve our understanding of the evolutionary processes that produce and maintain intraspecific behavioural heterogeneity. Here, we tested whether boldness, the most studied personality trait in fish, could predict learning ability in brook trout. After quantifying boldness, fish were trained to find a hidden food patch in a maze environment. Stable landmark cues were provided to indicate the location of food and, at the conclusion of training, cues were rearranged to test for learning. There was a negative relationship between boldness and learning as shy fish were increasingly more successful at navigating the maze and locating food during training trials compared to bold fish. In the altered testing environment, only shy fish continued using cues to search for food. Overall, the learning rate of bold fish was found to be lower than that of shy fish for several metrics suggesting that personality could have widespread effects on behaviour. Because learning can increase plasticity to environmental change, these results have significant implications for fish conservation.

Evaluation of the Relationship between Incisal Edge Position of Maxillary Central Incisors and Incisive Papilla in Patients Referred to Prosthodontics Department of Tabriz Dental Faculty

Background and Aims: Teeth position is an important component in a facial esthetic. Distance between incisive papilla and incisal edge of the maxillary centrals is a stable landmark in reconstruction anterior teeth of maxilla. Therefore in this study, we tried to establish this index in patients who recourse to the fixed prosthodontics dentistry faculty of Tabriz. Materials and Methods: The initial samples consisted of 59 patients referred to prosthodontics department of Tabriz dental faculty and took upper jaw impressions with irreversible hydrocolloid. Then, records poured by moldana stone until 15 minutes and needed anatomical spots were highlighted. The horizontal distance from anterior part on incisal edge of the maxillary centrals to anterior border, center and posterior border of incisive papillae were measured and statistically inspected. Results: The mean distance between the most anterior point of the incisal edge of the maxillary central incisors and the middle point, anterior border and posterior border of the incisive papilla was 8.54 ,7.12,10.28 mm with standard deviations of 0.83,0.75,1.002 mm. Conclusions: The usefulness of the incisive papilla as a reference point is limited because of the migration and change of shape it has been shown to undergo. However, it may serve some purpose because it is an easy measurement to make. Although the clinical findings may not always be true, but in many cases there is a close relationship. Key words : Teeth; incisive papilla; maxilla; occlusal plane;

Three-dimensional assessment of the palatal contour changes in orthodontically treated cases: A scanned maxillary cast analysis

Context: An accurate method for assessing the contour, symmetry, and stability of the dental arches is a prerequisite for investigations of form-function relationship. Various approaches to the study of arch shape have been described, but they were either best suited for simple visual analysis or when maximal accuracy was desired. The cost and complexity of the techniques and the equipment employed for assessing the arch shape preclude their general application. Hence, the present study was undertaken to evaluate the changes in palatal contour in orthodontically treated cases using scanned maxillary casts. Aims: The aim of the study was to evaluate the changes in palatal contour in orthodontically treated cases using scanned maxillary casts. Settings and Design: Retrospective study. Subjects and Methods: One hundred pre- and post-treatment maxillary casts of fifty completed cases in permanent dentition phase managed with fixed mechanotherapy were included in the present study. The landmarks were identified; scanning of the casts was done using flatbed scanner, and the palatal contoural changes were measured in three-dimensions after superimposing the pre- and post-treatment scanned images on medial points of the third palatal rugae which were considered as stable landmark. Statistical Analysis Used: Paired t -test. Results and Conclusions: There is statistically significant difference between the pre- and post-treatment width, anteroposterior length, and depth of the palate in orthodontically treated cases.

Relationship of Incisive Papilla to Maxillary Incisors and Canines

The study was carried to find a relationship between the postextraction stable landmark, the incisive papilla, and the most labial position of the maxillary central incisor teeth, which occurred in Nepalese population. Casts of the subjects selected by nonprobability random sampling meeting the inclusion criteria were obtained. Each casts were standardized with respect to the occlusal plane and a photographic technique was used to measure the distance from the tangent of the labial surface of the central incisors to the posterior border of the incisive papilla. The measurements were made using Adobe Photoshop and results were analyzed by using appropriate statistical methods. Most appropriate software (SPSS) for the purpose was used to generate all desired values. The data obtained suggested that the distance from the labial surface of maxillary central incisors to the posterior border of the incisive papilla ranged from 9 to 15.9 mm with a mean of 11.59 mm (SD 1.3). Various other results were also found after evaluation of the arch forms in relation to sex and race. Within the limitations of the study, these results suggested that there is a relationship between the maxillary central incisors and the incisive papilla aiding in the anteroposterior positioning of the anterior tooth. The clinical relevance of the study lies in application of the incisive papilla as a starting point in the preliminary location of maxillary incisors and canines during construction of the denture in absence of preextraction records.

AUTOMATIC NIPPLE DETECTION IN MAMMOGRAMS USING LOCAL MAXIMUM FEATURES ALONG BREAST CONTOUR

Mammogram registration is an important preprocessing technique, which helps in finding asymmetrical regions in left and right breast. However, correct nipple position is the crucial key point of mammogram registration since it is the only consistent and stable landmark upon a mammogram. To locate the nipple coordinates accurately in mammogram images, this work improves previous algorithms such as maximum height of the breast border (MHBB) and proposes a novel method consisting of local spatial-maximum mean intensity (LSMMI), local maximum zero-crossing (LMZC) based on the second-order derivative, and a combined approach dependent on LSMMI and LMZC. The proposed method is tested on 413 mammogram images from MIAS and DDSM databases. Consequently, the mean Euclidean distance (MED) between the ground truth identified by the radiologist and the detected nipple position is 0.64 cm, within 1 cm of the gold standard, for estimating the proposed method. The experimental results hence indicate that our proposed method can detect the nipple positions more accurately than other previous methods. Furthermore, the proposed select visible-nipple mammograms (SVNM) algorithm with the ability of generalization has achieved a 99% selection rate for automatic clustering of nipples in a mammography database, besides automatically detecting the breast border and nipple positions in mammograms.

A109 特徴領域の長期安定追従のための統計的存在確率による探索範囲制御及び不整地における基準平面導出に関する研究(OS2 宇宙機・宇宙ロボットのダイナミクスと制御2)

A109 特徴領域の長期安定追従のための統計的存在確率による探索範囲制御及び不整地における基準平面導出に関する研究(OS2 宇宙機・宇宙ロボットのダイナミクスと制御2)