Assessment of facial asymmetry using stereophotogrammetry

Asymmetry in the dimensions and spatial position of facial structures is a common finding in healthy individuals and in esthetically pleasing faces (1). Additionally, a variety of craniofacial anomalies are characterized by severe hard- and soft-tissue asymmetry (2). Facial asymmetry can impair the affected people from both aesthetical and functional points of view. Currently, facial asymmetry is mainly evaluated using the entire facial surface, thus providing measurements that give only general information about facial morphology. In contrast, several pathologies affecting facial appearance are localized in selected parts of the face, and a local assessment can provide helpful information for clinical decisions. For these reasons a detailed, focused and objective evaluation of facial asymmetry is advised, both for surgical planning and treatment evaluation. In this study we present a new quantitative method to assess symmetry in different facial thirds, objectively defined on the territories of distribution of trigeminal branches. Forty healthy young adults (21 women; 19 men; average age 39 ± 12 years) were acquired with a stereophotogrammetric system and the level of asymmetry of their hemi-facial thirds was evaluated, comparing the root mean square of the distances (RMSD) between their original and mirrored facial surfaces. The method resulted highly reproducible (Bland and Altman coefficient of reproducibility for area selection, 98.8%). In the upper facial third, median asymmetry was 0.726 mm (IQ range: 0.579-0.954 mm); in the middle facial third, median asymmetry was 0.739 mm (IQ range: 0.558-0.887 mm); in the lower facial third, median asymmetry was 0.679 mm (IQ range: 0.552-0.907 mm). No significant differences in RMSD values among the facial thirds were found (ANOVA, p>0.05). The presented method provides an accurate, reproducible and local facial symmetry analysis, that can be used for different conditions, especially when only part of the face is asymmetric.This work was supported by grants from University of Milan (Grant for Research 2015-2017)

Morphometric parameters for nasal septum deviation identification in CBCT data

Advances in the upper airway imaging allow to better evaluate and understand their morphology, pathology and mechanics [1]. In particular, Cone beam CT technology (CBCT), with its isotropic spatial resolution, undistorted images, X-ray lower radiation exposure, versatility and relatively low cost, takes over other imaging modalities [2]. The purpose of this study is to evaluate whether CBCT scans can be valuable tools for the extraction of quantitative parameters to confirm the deviation of the nasal septum in a specific patient. First, we assessed the difference in angle of septal deviation, calculated as proposed by Orhan et al., among a control group and a patient group [3]. Subsequently, we evaluated the percentage difference between the volume of the upper airways in the right side and left side of the nose in the same sample. The measurements were performed on 23 CBCT scans of Caucasian adult women, divided into 7 control subjects and 16 patients. The results demonstrate that there is a significant difference both in the deviation angle (p<0.05) and in the volume difference between healthy and patient subjects (p<0.001). Duplicate measurements of the deviation angle and the volume found no significant difference (p>0.05); random errors explained 0.77% (angle) and 0.99% (volume) of the sample variance. Paired Student’s t tests were used for comparisons. In particular, the volume difference appears to be less sensitive to the presence of isolated cartilaginous ridges that increase the angle of deviation even if the septum is not pathological. This makes it more suited to the identification of this pathology. The obtained outcomes are encouraging and it is advisable to continue the study on a larger sample

Evaluation of different registration approaches in 3D cephalometric landmark estimation

Thanks to the development of dedicated CBCT scanners, 3D cephalometric analysis is become a widely used tool for the diagnosis and treatment of dentofacial disharmonies in maxillofacial surgery and dentistry [1]. Traditionally, an expert manually annotates a set of cephalometric landmarks on a CBCT scan. Accuracy and repeatability of this manual approach are limited because of intra- and inter-subject variability in landmarks identification [2]. To improve the manual annotation, we are developing a nearly-automatic method that estimates the positions of a set of landmarks registering a previously annotated reference subject to the patient skull. In this study, in order to reduce the estimation error, we compare different registration approaches by varying two registration parameters, such as elasticity (affine or elastic) and domain (local or global) of geometric transformation. The algorithms were tested on 21 CBCT scans of adult caucasian women. To evaluate the outcome of the registration process, Euclidean distances in the 3D space between automatically and manually annotated landmarks were computed. Finally, for each landmark, accuracy and precision of the annotation process were calculated as the mean and standard deviation of the distances of the analyzed sample. Results show that the combination of a global affine registration followed by a global elastic registration significantly reduces the annotation error (p<0.001), increasing both accuracy (p<0.001) and precision (p>0.05). Paired Student’s t tests were used for comparisons. The obtained results are promising, nevertheless the study should be continued in order to reduce further estimation error

The face in Marfan syndrome: a 3D morphometric study

Marfan syndrome (MFS) is a rare congenital disorder of the connective tissue mainly caused by mutations in the FBN1 gene, resulting in an altered assembly of extracellular matrix microfibrils and TGF-beta signalling dysregulation. Major clinical manifestations of MFS involve the skeletal, ocular, and cardiovascular systems, with a high risk of life-threatening aortic dissection and rupture. An early recognition of the disorder is essential, but it could be difficult, due to the variable phenotypic expression of the disease and the current incomplete sensitivity of molecular genetic testing of FBN1. It has been suggested that craniofacial dysmorphism associated with MFS could facilitate obstructive sleep apnea, which in turn may promote aortic dilation. The study aimed to investigate the face in MFS through a 3D not invasive approach [1], identifying new morphometric features which could facilitate the early diagnosis of the disease. The 3D coordinates of 50 anatomical facial landmarks were obtained using a stereophotogrammetric system in 68 Italian subjects diagnosed with MFS, aged 4-64 years (27 males, mean ± SD age 29.6 ± 18.2 years; 41 females, mean ± SD age 37.2 ± 15.5 years). Subjects were divided in 11 non-overlapping age groups. Facial linear distances and angles were measured; z score values were calculated comparing patients with healthy Italian reference subjects (347 males, 388 females), matched for gender and age. Subjects with MFS showed a shorter mandibular ramus than controls (mean z score = -1.9), a greater facial divergence (mean z score = +2.0), a reduced ratio between posterior and anterior facial height (mean z score = -1.9), and a reduced ratio between facial width and facial height (mean z score = -1.5), together with an expected but overall mild increase of facial height (mean z score = +1.3). Noteworthy gender differences or age trends were not observed. Facial abnormalities pointed out in the current study could represent phenotypic traits of MFS; since they were observed also in young patients, their detection could facilitate the early recognition, management, and follow up of the disease. These promising findings need to be confirmed extending the study on more patients

Comparison of direct linear measurements on dental plaster cast and digital measurements obtained from laser scanner and Cone-Beam CT dental models

Different dental imaging technologies are now daily used in clinical practice to evaluate oral anatomy. These new techniques allow to replace dental plaster casts with digital models that are easier to manage and store. Such models can be acquired with optical methods like laser scanner, stereophotogrammetry and intraoral scanner or reconstructed by 3D CT or CBCT images [1]. Since these digital casts are used in clinical routine, it is important to evaluate accuracy and reliability of measurements taken from them, in relation to traditional methods [2]. We wanted to compare linear measurements taken on digital models obtained from CBCT images and laser scanner surfaces, with direct measurements obtained with digital calliper on dental plaster casts. Data from 6 adult Caucasian subjects with full dentition, no history of implant surgery and without dental filling were obtained. The absence of implants and metal fillings was selected as inclusion criterion to reduce the presence of metal artefacts that can affect the measurement process. All patients were retrospectively selected from a clinical database and underwent CBCT examination for clinical reasons uncorrelated with this study. Six dental distances in the upper and six in the lower jaw were examined: the mesio-distal distance of teeth 21, 23, 24 and 26, the palatal-vestibular distance of teeth 24 and 26, and the corresponding distances on teeth 41, 43, 44 and 46. All measurements were performed using: 1) a digital calliper on dental plaster casts; 2) a virtual calliper on digital models obtained from CBCT images; and 3) a virtual calliper on laser scanner surfaces. Kruskal-Wallis test compared measurements performed with the 3 different techniques. There was no statistical significant difference among different techniques for all measurements (p>0.05) except for one distance, the mesio-distal distance of tooth 24 (

Evaluation of accuracy and reproducibility in manual point picking during 3D cephalometry on CBCT data

Three-dimensional cephalometry is currently emerging as an innovative diagnos- tic tool, due to accessibility and radiation low dose of Cone Beam CT (CBCT) scan ners (1). Despite annotation made by specialists is now considered the gold standard in clinical practice and research, reliability of manual point picking can be biased by intra and inter-operator differences (2). In order to estimate the variability of the manual procedure, in this study an evaluation of accuracy, precision and reproducibility was performed. Three experienced operators analyzed ten CBCT images, retrospectively selected from the SST Dentofacial Clinic database. They annotated 9 chosen landmarks on all the images for three times, under the same conditions and at least one week of distance. Accuracy and precision were calculated as the median and the interquartile range of the distances from each landmark to the corresponding barycenter, calculated as the mean of all operator annotations. Kruskal-Wallis test was performed to evaluate reproducibility, and post-hoc tests were carried out to assess whether the significance depended from operators. A remarkable difference was found in accuracy between anatomic and geometrical landmarks, in both the intra and inter-operator repetitions. The intra-operator analysis showed higher accuracy and precision values than the inter-operator one. Statistical analyses revealed significant differences in reproducibility (p<0.05) for all landmarks except for Sella turcica, but the post-hoc tests did not show a clear pattern between operators. Results demonstrate that both accuracy and reproducibility may vary, depending on the operators, suggesting the need for automatic or semiautomatic tools that will help the operator during annotation

3D stereophotogrammetric facial analysis of SMAII patients

Spinal muscular atrophy (SMA) is a rare neurodegenerative disease, due to autosomal recessive mutations on SMN1 gene. It is clinically classified into 4 phenotypes (SMAI-SMAIV) and it is characterized by muscular weakness and atrophy of the voluntary muscles of the legs, arms and trunk [1]. No information is available about soft tissue facial characteristics in these patients. To better define their facial phenotype and to evidence possible modifications, the 3D facial reconstructions of 12 male SMAII patients (3-8 years) were evaluated. All of them were able to sit, but not to walk independently and had respiratory problems, chewing and swallowing difficulties. The facial reconstructions were obtained through a stereophotogrammetric system, after the non-invasive identification of 50 facial reference landmarks, whose 3D coordinates were used to calculate a series of linear measurements. Data were compared with those of healthy controls, matched for age and sex, through the calculation of z-score values [2]. Results show that patients have larger skull base, mandibular and facial widths (z-score = 1.5, 2 and 1.8 respectively), together with an increased height of the nose (z-score = 3) and mandibular body length (z-score = 2.1). The mandibular ramus length is reduced (z-score = -2.6). Results are of interest to define the facial anatomy of these patients, since a detailed knowledge of their facial features can be useful to create ergonomic devices, as respiratory masks, that these patients must daily use

Colorectal Cancer Stage at Diagnosis Before vs During the COVID-19 Pandemic in Italy

IMPORTANCE Delays in screening programs and the reluctance of patients to seek medical attention because of the outbreak of SARS-CoV-2 could be associated with the risk of more advanced colorectal cancers at diagnosis. OBJECTIVE To evaluate whether the SARS-CoV-2 pandemic was associated with more advanced oncologic stage and change in clinical presentation for patients with colorectal cancer. DESIGN, SETTING, AND PARTICIPANTS This retrospective, multicenter cohort study included all 17 938 adult patients who underwent surgery for colorectal cancer from March 1, 2020, to December 31, 2021 (pandemic period), and from January 1, 2018, to February 29, 2020 (prepandemic period), in 81 participating centers in Italy, including tertiary centers and community hospitals. Follow-up was 30 days from surgery. EXPOSURES Any type of surgical procedure for colorectal cancer, including explorative surgery, palliative procedures, and atypical or segmental resections. MAIN OUTCOMES AND MEASURES The primary outcome was advanced stage of colorectal cancer at diagnosis. Secondary outcomes were distant metastasis, T4 stage, aggressive biology (defined as cancer with at least 1 of the following characteristics: signet ring cells, mucinous tumor, budding, lymphovascular invasion, perineural invasion, and lymphangitis), stenotic lesion, emergency surgery, and palliative surgery. The independent association between the pandemic period and the outcomes was assessed using multivariate random-effects logistic regression, with hospital as the cluster variable. RESULTS A total of 17 938 patients (10 007 men [55.8%]; mean [SD] age, 70.6 [12.2] years) underwent surgery for colorectal cancer: 7796 (43.5%) during the pandemic period and 10 142 (56.5%) during the prepandemic period. Logistic regression indicated that the pandemic period was significantly associated with an increased rate of advanced-stage colorectal cancer (odds ratio [OR], 1.07; 95%CI, 1.01-1.13; P = .03), aggressive biology (OR, 1.32; 95%CI, 1.15-1.53; P < .001), and stenotic lesions (OR, 1.15; 95%CI, 1.01-1.31; P = .03). CONCLUSIONS AND RELEVANCE This cohort study suggests a significant association between the SARS-CoV-2 pandemic and the risk of a more advanced oncologic stage at diagnosis among patients undergoing surgery for colorectal cancer and might indicate a potential reduction of survival for these patients