Real-time hand tracking for rehabilitation and character animation

Hand and finger tracking has a major importance in healthcare, for rehabilitation of hand function required due to a neurological disorder, and in virtual environment applications, like characters animation for on-line games or movies. Current solutions consist mostly of motion tracking gloves with embedded resistive bend sensors that most often suffer from signal drift, sensor saturation, sensor displacement and complex calibration procedures. More advanced solutions provide better tracking stability, but at the expense of a higher cost. The proposed solution aims to provide the required precision, stability and feasibility through the combination of eleven inertial measurements units (IMUs). Each unit captures the spatial orientation of the attached body. To fully capture the hand movement, each finger encompasses two units (at the proximal and distal phalanges), plus one unit at the back of the hand. The proposed glove was validated in two distinct steps: a) evaluation of the sensors’ accuracy and stability over time; b) evaluation of the bending trajectories during usual finger flexion tasks based on the intra-class correlation coefficient (ICC). Results revealed that the glove was sensitive mainly to magnetic field distortions and sensors tuning. The inclusion of a hard and soft iron correction algorithm and accelerometer and gyro drift and temperature compensation methods provided increased stability and precision. Finger trajectories evaluation yielded high ICC values with an overall reliability within application’s satisfying limits. The developed low cost system provides a straightforward calibration and usability, qualifying the device for hand and finger tracking in healthcare and animation industries.

Voxel-based registration of simulated and real patient CBCT data for accurate dental implant pose estimation

The success of dental implant-supported prosthesis is directly linked to the accuracy obtained during implant’s pose estimation (position and orientation). Although traditional impression techniques and recent digital acquisition methods are acceptably accurate, a simultaneously fast, accurate and operator-independent methodology is still lacking. Hereto, an image-based framework is proposed to estimate the patient-specific implant’s pose using cone-beam computed tomography (CBCT) and prior knowledge of implanted model. The pose estimation is accomplished in a threestep approach: (1) a region-of-interest is extracted from the CBCT data using 2 operator-defined points at the implant’s main axis; (2) a simulated CBCT volume of the known implanted model is generated through Feldkamp-Davis-Kress reconstruction and coarsely aligned to the defined axis; and (3) a voxel-based rigid registration is performed to optimally align both patient and simulated CBCT data, extracting the implant’s pose from the optimal transformation. Three experiments were performed to evaluate the framework: (1) an in silico study using 48 implants distributed through 12 tridimensional synthetic mandibular models; (2) an in vitro study using an artificial mandible with 2 dental implants acquired with an i-CAT system; and (3) two clinical case studies. The results shown positional errors of 67±34μm and 108μm, and angular misfits of 0.15±0.08º and 1.4º, for experiment 1 and 2, respectively. Moreover, in experiment 3, visual assessment of clinical data results shown a coherent alignment of the reference implant. Overall, a novel image-based framework for implants’ pose estimation from CBCT data was proposed, showing accurate results in agreement with dental prosthesis modelling requirements.

A-scan ultrasound system for real-time puncture safety assessment during percutaneous nephrolithotomy

Background: Kidney stone is a major universal health problem, affecting 10% of the population worldwide. Percutaneous nephrolithotomy is a first-line and established procedure for disintegration and removal of renal stones. Its surgical success depends on the precise needle puncture of renal calyces, which remains the most challenging task for surgeons. This work describes and tests a new ultrasound based system to alert the surgeon when undesirable anatomical structures are in between the puncture path defined through a tracked needle. Methods: Two circular ultrasound transducers were built with a single 3.3-MHz piezoelectric ceramic PZT SN8, 25.4 mm of radius and resin-epoxy matching and backing layers. One matching layer was designed with a concave curvature to work as an acoustic lens with long focusing. The A-scan signals were filtered and processed to automatically detect reflected echoes. Results: The transducers were mapped in water tank and tested in a study involving 45 phantoms. Each phantom mimics different needle insertion trajectories with a percutaneous path length between 80 and 150 mm. Results showed that the beam cross-sectional area oscillates around the ceramics radius and it was possible to automatically detect echo signals in phantoms with length higher than 80 mm. Conclusions: This new solution may alert the surgeon about anatomical tissues changes during needle insertion, which may decrease the need of X-Ray radiation exposure and ultrasound image evaluation during percutaneous puncture.

Equívoco analítico & celebração do Plano Real

Este artigo discute a política antiinflacionária dos anos 1990 ("Plano Real") em sua moldura constitucional, na tradição do programa de pesquisa da public choice, revelando aspectos que as análises econômicas convencionais não contemplam: deterioração do sistema de separação de poderes; intensificação do poder discricionário dos burocratas federais; custos de transação associados ao plano, em termos de redução de transparência do processo decisório de política e perda de privacidade, na perspectiva do eleitor-contribuinte.

Violência (ir)real? Contributo para uma reflexão acerca do impacto da violência dos jogos electrónicos nas crianças e nos jovens

Na actualidade os jogos electrónicos são um entretenimento muito popular, fazendo parte do quotidiano de muitas crianças e jovens e ocupando um lugar de destaque nos seus interesses. Porém, o excesso de violência em alguns jogos tem contribuído para a legítima inquietação em torno dos seus efeitos na população mais jovem. Com base nas teorias que têm contribuído para a investigação no domínio dos efeitos da exposição à violência transmitida pelos media, este artigo procura reflectir sobre o impacto que a utilização de jogos, com conteúdos de violência, poderá exercer nos jogadores mais jovens. Tecem-se algumas considerações a propósito dos discursos que emergem sobre esta temática e,por fim, apresentam-se algumas estratégias de intervenção.

Inclusão ideal e inclusão real : estudo de caso com professoras de crianças surdas em uma escola regular de João Pessoa – PB

O presente estudo tem como objetivo analisar as condições de inclusão educacional de crianças surdas em uma escola regular, a partir dos relatos de professoras que vivenciam essa prática. Para coletar informações a esse respeito, foram realizadas junto às participantes entrevistas de caráter semi-estruturado. No tratamento a esses dados foram descritas as condições de inclusão existentes na escola (campo de pesquisa), como também os significados elaborados pelas participantes acerca do aluno surdo e da inclusão do mesmo na escola regular. Os dados foram coletados em uma amostra de cinco professoras de classes regulares que possuem alunos surdos. Esses dados foram submetidos a uma análise de conteúdo manual dos mesmos no modelo de Bardin (2002). Os resultados apontam para uma visão predominantemente negativa das condições de inclusão oferecidas pela escola, consideradas como inadequadas. Isto é agravado pela insuficiência em termos de capacitação dos professores para o trabalho inclusivo. Observa-se, pois, do ponto de vista das participantes, a existência de uma discrepância entre os modelos legal e real de inclusão das crianças surdas em escola regular, que se manifesta em diversos aspectos da prática pedagógica nesse contexto.