A Real-time Image Reconstruction System for Particle Treatment Planning Using Proton Computed Tomography (pCT)

Proton computed tomography (pCT) is a novel medical imaging modality for mapping the distribution of proton relative stopping power (RSP) in medical objects of interest. Compared to conventional X-ray computed tomography, where range uncertainty margins are around 3.5%, pCT has the potential to provide more accurate measurements to within 1%. This improved efficiency will be beneficial to proton-therapy planning and pre-treatment verification. A prototype pCT imaging device has recently been developed capable of rapidly acquiring low-dose proton radiographs of head-sized objects. We have also developed an advanced, fast image reconstruction software based on distributed computing that utilizes parallel processors and graphical processing units. The combination of fast data acquisition and fast image reconstruction will enable the availability of RSP images within minutes for use in clinical settings. The performance of our image reconstruction software has been evaluated using data collected by the prototype pCT scanner from several phantoms.Comment: Paper presented at Conference on the Application of Accelerators in Research and Industry, CAARI 2016, 30 October to 4 November 2016, Ft. Worth, TX, US

The early history of protostellar disks, outflows, and binary stars

In star formation, magnetic fields act as a cosmic angular momentum extractor that increases mass accretion rates onto protostars and in the process, creates spectacular outflows. However, recently it has been argued that this magnetic brake is so strong that early protostellar disks -- the cradles of planet formation -- cannot form. Our three-dimensional numerical simulations of the early stages of collapse (\lesssim 10^5 yr) of overdense star--forming clouds form early outflows and have magnetically regulated and rotationally dominated disks (inside 10 AU) with high accretion rates, despite the slip of the field through the mostly neutral gas. We find that in three dimensions, magnetic fields suppress gravitationally driven instabilities which would otherwise prevent young, well ordered disks from forming. Our simulations have surprising consequences for the early formation of disks, their density and temperature structure, the mechanism and structure of early outflows, the flash heating of dust grains through ambipolar diffusion, and the origin of planets and binary stars.Comment: 12 pages, 3 figures, accepted by ApJ Letters; corrected text to match journal version; movies can be found at http://www.physics.mcmaster.ca/~duffindf/movies.htm

Fast Focal Length Solution in Partial Panoramic Image Stitching

Accurate estimation of effective camera focal length is crucial to the success of panoramic image stitching. Fast techniques for estimating the focal length exist, but are dependent upon a close initial approximation or the existence of a full circle panoramic image sequence. Numerical solutions of the focal length demonstrate strong coupling between the focal length and the angles used to position each component image about the common spherical center. This paper demonstrates that parameterizing image position using distance over the sphere surface instead of angles effectively decouples the focal length from the image position. This new parameterization does not require an initial focal length estimate for quick convergence, nor does it require a full circle panorama in order to refine the focal length. Experiments with synthetic and real image sets demonstrate the robustness of the method and a speedup of 5 to 20 times over angle based positioning

Globally Optimal Image Mosaics

In this paper we examine the simultaneous solution of a set of image transformations with the goal of creating a globally optimal image mosaic. We examine an alternative parameterization of the full projective matrix transformation that leads to elimination of independent skew and aspect ratio parameters for each image. We also create a scale-free distance error metric which prevents the tendency of simultaneously solved systems to tend toward the zero solution. Keywords: Image stitching, image mosaics, projective transformations Introduction Image stitching or image mosaicing is the process of transforming and compositing a set of images, each a subset of a scene, into a single larger image. The transformation for each image maps the local coordinate system present in each image onto the global coordinate system in the final composite. There are several image transformation types used. Panoramic transformations onto cylinders are most common, as found in QuickTime VR[3, 2] and plen..

Spiders: A New User Interface for Rotation and Visualization of N-dimensional Point Sets

We present a new method for creating n-dimensional rotation matrices from manipulating the projections of n-dimensional data coordinate axes onto a viewing plane. A user interface for n-dimensional rotation is implemented. The interface is shown to have no rotational hysteresis. 1 Introduction Many techniques for visualizing n-dimensional data sets separate the data into its component dimensions, allowing the user to look at various coordinate combinations in a way that hopefully brings understanding. These methods do well at avoiding the traditional projection to two dimensions that hides data. However the data relationships are not immediately intuitive to our brains, which are used to transforming large amounts of information from three dimensional projections down to two. On the other hand, projection of n-dimensional information down to two may be slightly more intuitive, but suffers from the curse of data hiding due to projection. Moving the data in n-space, by predetermined m..