7,423 research outputs found
Deformable registration using shape statistics with applications in sinus surgery
Evaluating anatomical variations in structures like the nasal passage and sinuses is challenging because their complexity can often make it difficult to differentiate normal and abnormal anatomy. By statistically modeling these variations and estimating individual patient anatomy using these models, quantitative estimates of similarity or dissimilarity between the patient and the sample population can be made. In order to do this, a spatial alignment, or registration, between patient anatomy and the statistical model must first be computed.
In this dissertation, a deformable most likely point paradigm is introduced that incorporates statistical variations into probabilistic feature-based registration algorithms. This paradigm is a variant of the most likely point paradigm, which incorporates feature uncertainty into the registration process. The deformable registration algorithms optimize the probability of feature alignment as well as the probability of model deformation allowing statistical models of anatomy to estimate, for instance, structures seen in endoscopic video without the need for patient specific computed tomography (CT) scans. The probabilistic framework also enables the algorithms to assess the quality of registrations produced, allowing users to know when an alignment can be trusted. This dissertation covers three algorithms built within this paradigm and evaluated in simulation and in-vivo experiments
Measuring neutron star tidal deformability with Advanced LIGO: a Bayesian analysis of neutron star - black hole binary observations
The discovery of gravitational waves (GW) by Advanced LIGO has ushered us
into an era of observational GW astrophysics. Compact binaries remain the
primary target sources for LIGO, of which neutron star-black hole (NSBH)
binaries form an important subset. GWs from NSBH sources carry signatures of
(a) the tidal distortion of the neutron star by its companion black hole during
inspiral, and (b) its potential tidal disruption near merger. In this paper, we
present a Bayesian study of the measurability of neutron star tidal
deformability using observation(s) of
inspiral-merger GW signals from disruptive NSBH coalescences, taking into
account the crucial effect of black hole spins. First, we find that if
non-tidal templates are used to estimate source parameters for an NSBH signal,
the bias introduced in the estimation of non-tidal physical parameters will
only be significant for loud signals with signal-to-noise ratios . For
similarly loud signals, we also find that we can begin to put interesting
constraints on (factor of 1-2) with individual
observations. Next, we study how a population of realistic NSBH detections will
improve our measurement of neutron star tidal deformability. For astrophysical
populations of NSBH mergers, we find 20-35 events to be sufficient
to constrain within , depending on the
chosen equation of state. In this we also assume that LIGO will detect black
holes with masses within the astrophysical -. If the mass-gap
remains preserved in NSBHs detected by LIGO, we estimate that
detections will furnish comparable tidal measurement accuracy. In
both cases, we find that the loudest 5-10 events to provide most of the tidal
information, thereby facilitating targeted follow-ups of NSBHs in the upcoming
LIGO-Virgo runs.Comment: 21 pages, 17 figure
Deformable Prototypes for Encoding Shape Categories in Image Databases
We describe a method for shape-based image database search that uses deformable prototypes to represent categories. Rather than directly comparing a candidate shape with all shape entries in the database, shapes are compared in terms of the types of nonrigid deformations (differences) that relate them to a small subset of representative prototypes. To solve the shape correspondence and alignment problem, we employ the technique of modal matching, an information-preserving shape decomposition for matching, describing, and comparing shapes despite sensor variations and nonrigid deformations. In modal matching, shape is decomposed into an ordered basis of orthogonal principal components. We demonstrate the utility of this approach for shape comparison in 2-D image databases.Office of Naval Research (Young Investigator Award N00014-06-1-0661
Combining Self-Supervised Learning and Imitation for Vision-Based Rope Manipulation
Manipulation of deformable objects, such as ropes and cloth, is an important
but challenging problem in robotics. We present a learning-based system where a
robot takes as input a sequence of images of a human manipulating a rope from
an initial to goal configuration, and outputs a sequence of actions that can
reproduce the human demonstration, using only monocular images as input. To
perform this task, the robot learns a pixel-level inverse dynamics model of
rope manipulation directly from images in a self-supervised manner, using about
60K interactions with the rope collected autonomously by the robot. The human
demonstration provides a high-level plan of what to do and the low-level
inverse model is used to execute the plan. We show that by combining the high
and low-level plans, the robot can successfully manipulate a rope into a
variety of target shapes using only a sequence of human-provided images for
direction.Comment: 8 pages, accepted to International Conference on Robotics and
Automation (ICRA) 201
Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic surgery
One of the main challenges for computer-assisted surgery (CAS) is to determine the intra-opera- tive morphology and motion of soft-tissues. This information is prerequisite to the registration of multi-modal patient-specific data for enhancing the surgeon’s navigation capabilites by observ- ing beyond exposed tissue surfaces and for providing intelligent control of robotic-assisted in- struments. In minimally invasive surgery (MIS), optical techniques are an increasingly attractive approach for in vivo 3D reconstruction of the soft-tissue surface geometry. This paper reviews the state-of-the-art methods for optical intra-operative 3D reconstruction in laparoscopic surgery and discusses the technical challenges and future perspectives towards clinical translation. With the recent paradigm shift of surgical practice towards MIS and new developments in 3D opti- cal imaging, this is a timely discussion about technologies that could facilitate complex CAS procedures in dynamic and deformable anatomical regions
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