Gradient-domain volumetric photon density estimation

Gradient-Domain Photon Density Estimation

The most common solutions to the light transport problem rely on either Monte Carlo (MC) integration or density estimation methods, such as uni& bi-directional path tracing or photon mapping. Recent gradient-domain extensions of MC approaches show great promise; here, gradients of the final image are estimated numerically (instead of the image intensities themselves) with coherent paths generat...

Mammographic Density Estimation with Automated Volumetric Breast Density Measurement

OBJECTIVE To compare automated volumetric breast density measurement (VBDM) with radiologists' evaluations based on the Breast Imaging Reporting and Data System (BI-RADS), and to identify the factors associated with technical failure of VBDM. MATERIALS AND METHODS In this study, 1129 women aged 19-82 years who underwent mammography from December 2011 to January 2012 were included. Breast dens...

Distance Transform Gradient Density Estimation Using the Stationary Phase Approximation

we prove a novel result using the higher-order stationary phase approximation: we show convergence of the normalized power spectrum (squared magnitude of the Fourier transform) of the wave function to the density function of the distance transform gradients as the free parameter τ → 0. In colloquial terms, spatial frequencies are gradient histogram bins. Since distance transform gradients carry...

Regularized Multitask Learning for Multidimensional Log-Density Gradient Estimation

Log-density gradient estimation is a fundamental statistical problem and possesses various practical applications such as clustering and measuring nongaussianity. A naive two-step approach of first estimating the density and then taking its log gradient is unreliable because an accurate density estimate does not necessarily lead to an accurate log-density gradient estimate. To cope with this pr...

Stochastic Information Gradient Algorithm Based on Maximum Entropy Density Estimation