Image registration via stochastic gradient markov chain monte carlo

We develop a fully Bayesian framework for non-rigid registration of three-dimensional medical images, with a focus on uncertainty quantification. Probabilistic registration of large images along with calibrated uncertainty estimates is difficult for both computational and modelling reasons. To address the computational issues, we explore connections between the Markov chain Monte Carlo by backprop and the variational inference by backprop frameworks in order to efficiently draw thousands of samples from the posterior distribution. Regarding the modelling issues, we carefully design a Bayesian model for registration to overcome the existing barriers when using a dense, high-dimensional, and diffeomorphic parameterisation of the transformation. This results in improved calibration of uncertainty estimates

A Closest Point Proposal for MCMC-based Probabilistic Surface Registration

We propose to view non-rigid surface registration as a probabilistic inference problem. Given a target surface, we estimate the posterior distribution of surface registrations. We demonstrate how the posterior distribution can be used to build shape models that generalize better and show how to visualize the uncertainty in the established correspondence. Furthermore, in a reconstruction task, we show how to estimate the posterior distribution of missing data without assuming a fixed point-to-point correspondence. We introduce the closest-point proposal for the Metropolis-Hastings algorithm. Our proposal overcomes the limitation of slow convergence compared to a random-walk strategy. As the algorithm decouples inference from modeling the posterior using a propose-and-verify scheme, we show how to choose different distance measures for the likelihood model. All presented results are fully reproducible using publicly available data and our open-source implementation of the registration framework

Avaliação e perspectivas da abordagem à conservação do patrimônio organístico no Brasil

Órgãos de tubos são construídos no Brasil, ou importados do exterior, desde as primeiras décadas do período colonial. Estes instrumentos, apesar de constituírem um conjunto relativamente exíguo, representam um testemunho histórico e musical de valor inestimável. No entanto, de um modo geral, encontram-se em condições precárias de funcionamento e, em parte, mais ou menos descaracterizados profundamente, quanto à sua estrutura e configuração original, às vezes em estado de abandono e, por incrível que pareça, ainda sujeitos ao risco de intervenções arbitrárias e desprovidas de bases técnicas e de preocupação histórica e musicológica. Neste artigo, busca-se percorrer o caminho que levou à atual situação e discutem-se os princípios e os critérios de processos de recuperação, manutenção e conservação preventiva desse patrimônio, partindo dos pressupostos do respeito à sua originalidade e do direito a restauros segundo os rigorosos cânones já definidos para objetos com plena condição de bem cultural, cujo reconhecimento para os órgãos de qualquer época deve ser urgentemente garantido.Pipe organs have been built in Brazil or imported from elsewhere since the very first decades of the colonial period. Albeit relatively small in number, such instruments have inestimable historical and musical value. Notwithstanding, they are generally in very poor working condition and some have lost much of their original structure and configuration; they are often found in a state of abandonment and, incredible as it may seem, still under the threat of arbitrary interventions performed with no technical expertise or any concern for their historical and musicological significance. This article is an effort to understand how this state of affairs came to be, and discusses principles and criteria for the restoration, maintenance and preventive conservation of this legacy, based on assumptions regarding its original conditions and entitlement to restoration in accordance with the stringent standards already set for artifacts that enjoy the full status of cultural assets, which should also be urgently granted to pipe organs of any time and age

Efficient Laplace Approximation for Bayesian Registration Uncertainty Quantification

© Springer Nature Switzerland AG 2018. This paper presents a novel approach to modeling the posterior distribution in image registration that is computationally efficient for large deformation diffeomorphic metric mapping (LDDMM). We develop a Laplace approximation of Bayesian registration models entirely in a bandlimited space that fully describes the properties of diffeomorphic transformations. In contrast to current methods, we compute the inverse Hessian at the mode of the posterior distribution of diffeomorphisms directly in the low dimensional frequency domain. This dramatically reduces the computational complexity of approximating posterior marginals in the high dimensional imaging space. Experimental results show that our method is significantly faster than the state-of-the-art diffeomorphic image registration uncertainty quantification algorithms, while producing comparable results. The efficiency of our method strengthens the feasibility in prospective clinical applications, e.g., real-time image-guided navigation for brain surgery

Visualization tool for improved accuracy in needle placement during percutaneous radio-frequency ablation of liver tumors

The European research network “Augmented reality in Surgery” (ARIS*ER) developed a system that supports percutaneous radio frequency ablation of liver tumors. The system provides interventionists, during placement and insertion of the RFA needle, with information from pre-operative CT images and real-time tracking data. A visualization tool has been designed that aims to support (1) exploration of the abdomen, (2) planning of needle trajectory and (3) insertion of the needle in the most efficient way. This work describes a first evaluation of the system, where user performances and feedback of two visualization concepts of the tool – needle view and user view – are compared. After being introduced to the system, ten subjects performed three needle placements with both concepts. Task fulfillment rate, time for completion of task, special incidences, accuracy of needle placement recorded and analyzed. The results show ambiguous results with beneficial and less favorable effects on user performance and workload of both concepts. Effects depend on characteristics of intra-operative tasks as well as on task complexities depending on tumor location. The results give valuable input for the next design steps.Human Information Communication DesignIndustrial Design Engineerin