Monte Carlo sampling of non-Gaussian proposal distribution in feature-based RBPF-SLAM

Particle filters are widely used in mobile robot localization and mapping. It is well-known that choosing an appropriate proposal distribution plays a crucial role in the success of particle filters. The proposal distribution conditioned on the most recent observation, known as the optimal proposal distribution (OPD), increases the number of effective particles and limits the degeneracy of filter. Conventionally, the OPD is approximated by a Gaussian distribution, which can lead to failure if the true distribution is highly non-Gaussian. In this paper we propose two novel solutions to the problem of feature-based SLAM, through Monte Carlo approximation of the OPD which show superior results in terms of mean squared error (MSE) and number of effective samples. The proposed methods are capable of describing non-Gaussian OPD and dealing with nonlinear models. Simulation and experimental results in large-scale environments show that the new algorithms outperform the aforementioned conventional methods

mpMRI preoperative staging in men treated with antiandrogen and androgen deprivation therapy before robotic prostatectomy

© 2019 Introduction: Using multiparametric magnetic resonance imaging (mpMRI), we sought to preoperatively characterize prostate cancer (PCa)in the setting of antiandrogen plus androgen deprivation therapy (AA-ADT)prior to robotic-assisted radical prostatectomy (RARP). We present our preliminary findings regarding mpMRI depiction of changes of disease staging features and lesion appearance in treated prostate. Methods: Prior to RARP, men received 6 months of enzalutamide and goserelin. mpMRI consisting of T2 weighted, b = 2,000 diffusion weighted imaging, apparent diffusion coefficient mapping, and dynamic contrast enhancement sequences was acquired before and after neoadjuvant therapy. Custom MRI-based prostate molds were printed to directly compare mpMRI findings to H&E whole-mount pathology as part of a phase II clinical trial (NCT02430480). Results: Twenty men underwent imaging and RARP after a regimen of AA-ADT. Positive predictive values for post-AA-ADT mpMRI diagnosis of extraprostatic extension, seminal vesicle invasion, organ-confined disease, and biopsy-confirmed PCa lesions were 71%, 80%, 80%, and 85%, respectively. Post-treatment mpMRI correctly staged disease in 15/20 (75%)cases with 17/20 (85%)correctly identified as organ-confined or not. Of those incorrectly staged, 2 were falsely positive for higher stage features and 1 was falsely negative. Post-AA-ADT T2 weighted sequences best depicted presence of PCa lesions as compared to diffusion weighted imaging and dynamic contrast enhancement sequences. Conclusion: mpMRI proved reliable in detecting lesion changes after antiandrogen therapy corresponding to PCa pathology. Therefore, mpMRI of treated prostates may be helpful for assessing men for surgical planning and staging