Catadioptric stereo-vision system using a spherical mirror

Abstract In the computer vision field, the reconstruction of target surfaces is usually achieved by using 3D optical scanners assembled integrating digital cameras and light emitters. However, these solutions are limited by the low field of view, which requires multiple acquisition from different views to reconstruct complex free-form geometries. The combination of mirrors and lenses (catadioptric systems) can be adopted to overcome this issue. In this work, a stereo catadioptric optical scanner has been developed by assembling two digital cameras, a spherical mirror and a multimedia white light projector. The adopted configuration defines a non-single viewpoint system, thus a non-central catadioptric camera model has been developed. An analytical solution to compute the projection of a scene point onto the image plane (forward projection) and vice-versa (backward projection) is presented. The proposed optical setup allows omnidirectional stereo vision thus allowing the reconstruction of target surfaces with a single acquisition. Preliminary results, obtained measuring a hollow specimen, demonstrated the effectiveness of the described approach

Sensor architectures and technologies for upper limb 3d surface reconstruction: A review

3D digital models of the upper limb anatomy represent the starting point for the design process of bespoke devices, such as orthoses and prostheses, which can be modeled on the actual patient’s anatomy by using CAD (Computer Aided Design) tools. The ongoing research on optical scanning methodologies has allowed the development of technologies that allow the surface reconstruction of the upper limb anatomy through procedures characterized by minimum discomfort for the patient. However, the 3D optical scanning of upper limbs is a complex task that requires solving problematic aspects, such as the difficulty of keeping the hand in a stable position and the presence of artefacts due to involuntary movements. Scientific literature, indeed, investigated different approaches in this regard by either integrating commercial devices, to create customized sensor architectures, or by developing innovative 3D acquisition techniques. The present work is aimed at presenting an overview of the state of the art of optical technologies and sensor architectures for the surface acquisition of upper limb anatomies. The review analyzes the working principles at the basis of existing devices and proposes a categorization of the approaches based on handling, pre/post-processing effort, and potentialities in real-time scanning. An in-depth analysis of strengths and weaknesses of the approaches proposed by the research community is also provided to give valuable support in selecting the most appropriate solution for the specific application to be addressed

Which is the most accurate diagnostic procedure in Tamoxifen treated breast cancer patients

Purpose: The aim of this study was to evaluate the diagnostic accuracy of bi-dimensional (2D) and three-dimensional (3D) transvaginal ultrasound (TVUS), hysterosonography (HSSG) and hysteroscopy in the detection of endometrial pathology in women treated with tamoxifen (TMX) for breast cancer. Methods: Forty-two patients, affected by breast cancer under treatment with TMX, underwent 2D-3D TVUS, HSSG and hysteroscopy completed by biopsy, after abnormal findings following a routine 2D TVUS examination. Results: 3D-TVUS was more accurate than 2D-TVUS in the detection of atrophic endometrium confirmed by biopsy and in the detection of endometrial polyps. HSSG and hysteroscopy detected atrophic endometrium and endometrial polyps significantly better than ultrasound scan. Endometrial carcinoma was detected in two cases, and in both HSSG and hysteroscopy were 100% diagnostic. Conclusion: In TMX treated breast cancer patients, HSSG and hysteroscopy provide more accurate diagnosis than 2D-3D ultrasound in the detection of treatment related endometrial lesions

Pancreas divisum. Correlation between anatomical abnormalities and bile precipitation in the gallbladder in seven patients

Pancreas divisum is a genetic defect associated with recurrent acute pancreatitis due to insufficient drainage of the accessory pancreatic duct. Seven young patients diagnosed with pancreatic divisum and thickening of the gallbladder bile as shown on magnetic resonance cholangio-pancreatography without pancreatic ductal changes underwent laparoscopic cholecystectomy. During the mean follow-up of 32 months no episode of pancreatitis was reported. There is an association between PD and higher concentration of bile in the gallbladder. Cholecystectomy can be considered curative in patients with PD in the absence of indications for major surgery

A CAE approach for the stress analysis of gear models by 3D digital photoelasticity

The use of numerical and experimental methods to determine the stress field of mechanical components is well known. In particular, 3D photoelasticity can be considered the only experimental technique for the complete stress state evaluation of 3D components. The advent of rapid prototyping techniques has allowed the manufacturing of complex models in a matter of hours by using birifrangent materials. The present paper is focused on the description of a Computer Aided Engineering (CAE) approach which combines Finite Element (FE) simulations and automatic photoelastic investigations for the stress analysis of face gear drives, made by stereolithography. Computer Aided Design (CAD) geometries, used to manufacture the stereolithographic models, are directly used to perform FE analyses, thus allowing the stress analysis process to become simpler and easier. The substantial agreement observed between experimental and numerical results proved the potentialities of the adopted approach and the usefulness of FE simulations to optimize photoelastic analyses through cost- and time-effective experiments even for complex 3D shapes

Integration of 3D anatomical data obtained by CT imaging and 3D optical scanning for computer aided implant surgery

<p>Abstract</p> <p>Background</p> <p>A precise placement of dental implants is a crucial step to optimize both prosthetic aspects and functional constraints. In this context, the use of virtual guiding systems has been recognized as a fundamental tool to control the ideal implant position. In particular, complex periodontal surgeries can be performed using preoperative planning based on CT data. The critical point of the procedure relies on the lack of accuracy in transferring CT planning information to surgical field through custom-made stereo-lithographic surgical guides.</p> <p>Methods</p> <p>In this work, a novel methodology is proposed for monitoring loss of accuracy in transferring CT dental information into periodontal surgical field. The methodology is based on integrating 3D data of anatomical (impression and cast) and preoperative (radiographic template) models, obtained by both CT and optical scanning processes.</p> <p>Results</p> <p>A clinical case, relative to a fully edentulous jaw patient, has been used as test case to assess the accuracy of the various steps concurring in manufacturing surgical guides. In particular, a surgical guide has been designed to place implants in the bone structure of the patient. The analysis of the results has allowed the clinician to monitor all the errors, which have been occurring step by step manufacturing the physical templates.</p> <p>Conclusions</p> <p>The use of an optical scanner, which has a higher resolution and accuracy than CT scanning, has demonstrated to be a valid support to control the precision of the various physical models adopted and to point out possible error sources. A case study regarding a fully edentulous patient has confirmed the feasibility of the proposed methodology.</p

Automatic Alignment of Multiple Point Clouds by Image Processing and 3D Data Matching

In recent years, various methodologies of reverse engineering have been proposed with the aim at creating CAD models from digitization of target objects using optical sensors. Traditionally, the acquisition of 3D geometrical data includes crucial tasks, such as planning scanning strategies and aligning different point clouds by many alternative methodologies which differ for user interaction levels and costs. This paper describes a technology to acquire free form surfaces by combining a 3D vision system and a fully automatic point clouds alignment procedure based on fiducial marker recognition. The aim is to create accurate and complete digital representations of physical objects, even those presenting a few morphological singularities, in a very short time and with minimal human intervention. The technology has been tested acquiring target objects with complex shape

Large yacht hull measurement by integrating optical scanning with mechanical tracking-based methodologies

In the shipbuilding industry, the manufacturing of large yacht hulls is a complex process. Metal hulls are traditionally manufactured by welding pre fabricated large steel panels to form the external superstructure. A surface finishing process is then carried out in order to obtain a final target surface having a smooth curvature. The methodologies manly rely on manual processes based on the measurement of the as built hull shape through simple testing instrumentation. Well-experienced workers are required, and a great amount of time is usually wasted, thus affecting the overall shipyard competitiveness. This paper introduces a methodology for automating the measurement process of as built hull yacht shapes. The methodology, which is based on the integration of a robotic system with an optical scanner, provides accurate non contact 3D full field measurements of the hull surface. The placement of the robotic system around the hull shape is determined by a laser total station thus allowing the automatic multi view data registration into a common reference frame. The proposed approach represents the basis for the automation of the whole surface finishing process of large yacht hulls. In this paper, the methodology has been tested by measuring a large broadside area of a 59 m hull assembled within a shipyard

A CAD-based Methodology for Dental Implant Surgery

In the field of oral rehabilitation, innovative methodologies based on the combined use of 3D imaging technologies and computer-guided approaches, have been developed with the aim at defining reliable tools for the virtual preoperative assessment of implant placement. The accurate and reliable transfer of the virtual planning into the surgical field represents the main challenge for modern implantology. This paper aims at defining and verifying the clinical applicability of an innovative CAD/CAM framework for the accurate planning of dental implant surgeries based on the integration of Computed Tomography (CT) and surface optical scanning. The higher accuracy and resolution of optical scanning allows a more accurate reconstruction of dentition structures and mouth soft tissues, thus guaranteeing a better fitting of the designed prosthetic structures with respect to the patient oral cavity