Analyse de la relation entre les déformations scoliotiques du tronc et celles des structures osseuses sous-jacentes

RÉSUMÉ La scoliose idiopathique adolescente est une déformation tridimensionnelle complexe de la colonne vertébrale et de la cage thoracique qui entraine des déformations visibles à la surface du tronc. On remarque généralement une asymétrie des épaules, des omoplates, de la taille et du bassin ainsi qu’une bosse dans le dos. Ces déformations esthétiques constituent, d’une part, les premiers signes d’une scoliose, et d’autre part, la principale préoccupation des jeunes patients qui voient leur corps se développer différemment des jeunes de leur âge. Les outils cliniques utilisés pour quantifier les déformations du tronc, comme le scoliomètre ou le fil à plomb, sont peu fiables. C’est pourquoi, aujourd’hui, l’évaluation de la scoliose repose principalement sur des radiographies de face et de profil du tronc complet. Celles-ci permettent d’apprécier le type de courbure rachidienne et de quantifier son degré de sévérité, en fonction de quoi une stratégie de traitement sera décidée. Cependant, une exposition répétée des patients aux rayons X peut entrainer des effets indésirables sur leur santé. De plus, ces paramètres radiographiques ne permettent pas de documenter les déformations esthétiques. Cette différence notable entre ce que le patient perçoit, et ce que le clinicien est capable d’évaluer, peut mener à l’insatisfaction des patients suite au traitement. Comparativement aux radiographies, la surface du tronc reconstruite par les systèmes de numériseurs optiques 3D représente mieux les déformations que les patients observent et dont ils se soucient principalement, comme la gibbosité. De plus, l’absence de rayonnement ionisant est un avantage majeur de ces systèmes optiques, qui favorise une évaluation aussi fréquente que souhaité. Toutefois, l’absence de consensus sur un ensemble de mesures des déformations de la surface du tronc fait en sorte qu’elles restent encore considérées comme secondaires dans l’évaluation clinique; pourtant elles sont au coeur des préoccupations des patients. De cette double problématique, découle la question de recherche globale de cette thèse : comment compléter, voire remplacer, les évaluations clinique et radiographique actuelles de la scoliose par de l’information quantitative obtenue de manière non irradiante et qui permet de prendre davantage en considération les préoccupations des patients par rapport à leurs déformations esthétiques du tronc ? Parmi les premiers signes de scoliose, la gibbosité est une déformation esthétique qui ne peut être évaluée sur des radiographies, ni sur une reconstruction 3D de la colonne vertébrale.----------ABSTRACT Adolescent idiopathic scoliosis is a complex three-dimensional deformation of the spine and rib cage which leads to visible deformations at the trunk surface. The first signs of scoliosis include a hump on the back, a lateral shift of the trunk and asymmetries of the shoulders, the scapula, the waist and the hips. These esthetic deformities constitute major concern of patients and the reason for which they seek treatment. Currently, the tools available in clinical practice to quantify trunk deformations have limited reliability. For this reason, current scoliosis assessment is mainly based on frontal and lateral radiographs of the entire spine. These images allow clinicians to determine the type of the spinal curvature and its severity, according to which the treatment strategy is decided. However, the repeated exposure of patients to X-ray radiation can be harmful. Moreover, these radiographic measures do not give an indication as to the esthetic deformities of the trunk. This significant difference between what patients perceive and what clinicians are able to evaluate can lead to patient dissatisfaction following treatment. Compared to X-rays, the trunk surface acquired and reconstructed in 3D using optical digitizers better represents the deformations that patients observe and are primarily concerned with, such as the rib hump. In addition, the major advantage of these optical systems is their lack of ionizing radiation, thus allowing for a more frequent scoliosis assessment when compared to X-rays. However, there is currently no consensus on a set of indices that optimally quantifies trunk surface deformations. For this reason, trunk surface indices are still considered as secondary in the clinical evaluation, even though they are at the heart of the patients’ preoccupations. These problems lead to the main research question of this thesis: How can we complete, or even replace, the current clinical and radiographic evaluations of scoliosis with quantitative information obtained without ionizing radiation that takes more into account the patients’ concerns about their cosmetic trunk deformities? Among the first signs of scoliosis, the rib hump is a cosmetic deformity that cannot be assessed on radiographs, nor on a 3D reconstruction of the spine. It is mainly associated with rib cage deformity. It is therefore intuitive to suppose that the axial rotations of the ribs and of the back surface are highly correlated. Nevertheless, previous works have failed to demonstrate a strong relationship between these measurements. This might be explained by the limited accuracy of the technique used for the 3D reconstruction of the ribs. Consequently, in this work, a novel metho

Automatic Grading of Diabetic Retinopathy on a Public Database

With the growing diabetes epidemic, retina specialists have to examine a tremendous amount of fundus images for the detection and grading of diabetic retinopathy. In this study, we propose a first automatic grading system for diabetic retinopathy. First, a red lesion detection is performed to generate a lesion probability map. The latter is then represented by 35 features combining location, size and probability information, which are finally used for classification. A leave-one-out cross-validation using a random forest is conducted on a public database of 1200 images, to classify the images into 4 grades. The proposed system achieved a classification accuracy of 74.1% and a weighted kappa value of 0.731 indicating a significant agreement with the reference. These preliminary results prove that automatic DR grading is feasible, with a performance comparable to that of human experts

Multilevel Analysis of Trunk Surface Measurements for Noninvasive Assessment of Scoliosis Deformities

Study Design. Reliability study. Objectives. To assess between-acquisition reliability of new multilevel trunk cross sections measurements, in order to define what is a real change when comparing 2 trunk surface acquisitions of a same patient, before and after surgery or throughout the clinical monitoring. Summary of Background Data. Several cross-sectional surface measurements have been proposed in the literature for noninvasive assessment of trunk deformity in patients with adolescent idiopathic scoliosis (AIS). However, only the maximum values along the trunk are evaluated and used for monitoring progression and assessing treatment outcome. Methods. Back surface rotation (BSR), trunk rotation (TR), and coronal and sagittal trunk deviation are computed on 300 cross sections of the trunk. Each set of 300 measures is represented as a single functional data, using a set of basis functions. To evaluate between-acquisition variability at all trunk levels, a test-retest reliability study is conducted on 35 patients with AIS. A functional correlation analysis is also carried out to evaluate any redundancy between the measurements. Results. Each set of 300 measures was successfully described using only 10 basis functions. The test-retest reliability of the functional measurements is good to very good all over the trunk, except above the shoulders level. The typical errors of measurement are between 1.20° and 2.2° for the rotational measures and between 2 and 6 mm for deviation measures. There is a very strong correlation between BSR and TR all over the trunk, a moderate correlation between coronal trunk deviation and both BSR and TR, and no correlation between sagittal trunk deviation and any other measurement. Conclusion. This novel representation of trunk surface measurements allows for a global assessment of trunk surface deformity. Multilevel trunk measurements provide a broader perspective of the trunk deformity and allow a reliable multilevel monitoring during clinical follow-up of patients with AIS and a reliable assessment of the esthetic outcome after surgery.CIHR /IRS

Changes in Trunk Appearance After Scoliosis Spinal Surgery and Their Relation to Changes in Spinal Measurements

Study Design Retrospective study of surgical outcome. Objectives To evaluate quantitatively the changes in trunk surface deformities after scoliosis spinal surgery in Lenke 1A adolescent idiopathic scoliosis (AIS) patients and to compare it with changes in spinal measurements. Summary of Background Data Most studies documenting scoliosis surgical outcome used either radiographs to evaluate changes in the spinal curve or questionnaires to assess patients health-related quality of life. Because improving trunk appearance is a major reason for patients and their parents to seek treatment, this study focuses on postoperative changes in trunk surface deformities. Recently, a novel approach to quantify trunk deformities in a reliable, automatic, and noninvasive way has been proposed. Methods Forty-nine adolescents with Lenke 1A idiopathic scoliosis treated surgically were included. The back surface rotation and trunk lateral shift were computed on trunk surface acquisitions before and at least 6 months after surgery. We analyzed the effect of age, height, weight, curve severity, and flexibility before surgery, length of follow-up, and the surgical technique. For 25 patients with available three-dimensional (3D) spinal reconstructions, we compared changes in trunk deformities with changes in two-dimensional (2D) and 3D spinal measurements. Results The mean correction rates for the back surface rotation and the trunk lateral shift are 18% and 50%, respectively. Only the surgical technique had a significant effect on the correction rate of the back surface rotation. Direct vertebral derotation and reduction by spine translation provide a better correction of the rib hump (22% and 31% respectively) than the classic rod rotation technique (8%). The reductions of the lumbar Cobb angle and the apical vertebrae transverse rotation explain, respectively, up to 17% and 16% the reduction of the back surface rotation. Conclusions Current surgical techniques perform well in realigning the trunk; however, the correction of the deformity in the transverse plane proves to be more challenging. More analysis on the positive effect of vertebral derotation on the rib hump correction is needed. Level of evidence III.Natural Sciences and Engineering Research Council of Canada (Grant # 222860-2012RGPIN) and MENTOR, a strategic training program of the Canadian Institutes of Health Research

Non-invasive quantitative assessment of scoliosis spinal surgery outcome

Improving the appearance of the trunk is an important goal of scoliosis surgical treatment, mainly in patients' eyes. Unfortunately, existing methods for assessing postoperative trunk appearance are rather subjective as they rely on a qualitative evaluation of the trunk shape. In this paper, an objective method is proposed to quantify the changes in trunk shape after surgery. Using a non-invasive optical system, the whole trunk surface is acquired and reconstructed in 3D. Trunk shape is described by two functional measurements spanning the trunk length: the lateral deviation and the axial rotation. To measure the pre and postoperative differences, a correction rate is computed for both measurements. On a cohort of 36 scoliosis patients with the same spinal curve type who underwent the same surgical approach, surgery achieved a very good correction of the lateral trunk deviation (median correction of 76%) and a poor to moderate correction of the back axial rotation (median correction of 19%). These results demonstrate that after surgery, patients are still confronted with residual trunk deformity, mainly a persisting hump on the back. That can be explained by the fact that current scoliosis assessment and treatment planning are based solely on radiographic measures of the spinal deformity and do not take trunk deformity into consideration. It is believed that with our novel quantitative trunk shape descriptor, clinicians and surgeons can now objectively assess trunk deformity and postoperative shape and propose new treatment strategies that could better address patients' concern about their appearance. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.CIHR / IRS

Predicting Next Local Appearance for Video Anomaly Detection

We present a local anomaly detection method in videos. As opposed to most existing methods that are computationally expensive and are not very generalizable across different video scenes, we propose an adversarial framework that learns the temporal local appearance variations by predicting the appearance of a normally behaving object in the next frame of a scene by only relying on its current and past appearances. In the presence of an abnormally behaving object, the reconstruction error between the real and the predicted next appearance of that object indicates the likelihood of an anomaly. Our method is competitive with the existing state-of-the-art while being significantly faster for both training and inference and being better at generalizing to unseen video scenes.Comment: Accepted as an oral presentation for MVA'202

A Novel Method for the 3-D Reconstruction of Scoliotic Ribs From Frontal and Lateral Radiographs

Among the external manifestations of scoliosis, the rib hump, which is associated with the ribs' deformities and rotations, constitutes the most disturbing aspect of the scoliotic deformity for patients. A personalized 3-D model of the rib cage is important for a better evaluation of the deformity, and hence, a better treatment planning. A novel method for the 3-D reconstruction of the rib cage, based only on two standard radiographs, is proposed in this paper. For each rib, two points are extrapolated from the reconstructed spine, and three points are reconstructed by stereo radiography. The reconstruction is then refined using a surface approximation. The method was evaluated using clinical data of 13 patients with scoliosis. A comparison was conducted between the reconstructions obtained with the proposed method and those obtained by using a previous reconstruction method based on two frontal radiographs. A first comparison criterion was the distances between the reconstructed ribs and the surface topography of the trunk, considered as the reference modality. The correlation between ribs axial rotation and back surface rotation was also evaluated. The proposed method successfully reconstructed the ribs of the 6th-12th thoracic levels. The evaluation results showed that the 3-D configuration of the new rib reconstructions is more consistent with the surface topography and provides more accurate measurements of ribs axial rotation.Natural Sciences and Engineering Research Council of Canada and MENTOR, a strategic training program of the Canadian Institutes of Health Research

Noninvasive Clinical Assessment of Trunk Deformities Associated With Scoliosis

Besides the spinal deformity, scoliosis modifies notably the general appearance of the trunk resulting in trunk rotation, imbalance, and asymmetries that constitutes patients' major concern. Existing classifications of scoliosis, based on the type of spinal curve as depicted on radiographs, are currently used to guide treatment strategies. Unfortunately, even though a perfect correction of the spinal curve is achieved, some trunk deformities remain, making patients dissatisfied with the treatment received. The purpose of this study is to identify possible shape patterns of trunk surface deformity associated with scoliosis. First, trunk surface is represented by a multivariate functional trunk shape descriptor based on 3-D clinical measurements computed on cross sections of the trunk. Then, the classical formulation of hierarchical clustering is adapted to the case of multivariate functional data and applied to a set of 236 trunk surface 3-D reconstructions. The highest internal validity is obtained when considering 11 clusters that explain up to 65% of the variance in our dataset. Our clustering result shows a concordance with the radiographic classification of spinal curves in 68% of the cases. As opposed to radiographic evaluation, the trunk descriptor is 3-D and its functional nature offers a compact and elegant description of not only the type, but also the severity and extent of the trunk surface deformity along the trunk length. In future work, new management strategies based on the resulting trunk shape patterns could be thought of in order to improve the esthetic outcome after treatment, and thus patients satisfaction.CIHR / IRS

Towards Non Invasive Diagnosis of Scoliosis Using Semi-supervised Learning Approach

Collection : Lecture notes in computer science ; vol. 6112In this paper, a new methodology for the prediction of scoliosis curve types from non invasive acquisitions of the back surface of the trunk is proposed. One hundred and fifty-nine scoliosis patients had their back surface acquired in 3D using an optical digitizer. Each surface is then characterized by 45 local measurements of the back surface rotation. Using a semi-supervised algorithm, the classifier is trained with only 32 labeled and 58 unlabeled data. Tested on 69 new samples, the classifier succeeded in classifying correctly 87.0% of the data. After reducing the number of labeled training samples to 12, the behavior of the resulting classifier tends to be similar to the reference case where the classifier is trained only with the maximum number of available labeled data. Moreover, the addition of unlabeled data guided the classifier towards more generalizable boundaries between the classes. Those results provide a proof of feasibility for using a semi-supervised learning algorithm to train a classifier for the prediction of a scoliosis curve type, when only a few training data are labeled. This constitutes a promising clinical finding since it will allow the diagnosis and the follow-up of scoliotic deformities without exposing the patient to X-ray radiations.CIHR / IRS

Prediction of scoliosis curve type based on the analysis of trunk surface topography

Scoliosis treatment strategy is generally chosen according to the severity and type of the spinal curve. Currently, the curve type is determined from X-rays whose acquisition can be harmful for the patient. We propose in this paper a system that can predict the scoliosis curve type based on the analysis of the surface of the trunk. The latter is acquired and reconstructed in 3D using a non invasive multi-head digitizing system. The deformity is described by the back surface rotation, measured on several cross-sections of the trunk. A classifier composed of three support vector machines was trained and tested using the data of 97 patients with scoliosis. A prediction rate of 72.2% was obtained, showing that the use of the trunk surface for a high-level scoliosis classification is feasible and promising.CIHR / IRS