Shape and Motion from Linear Features

This paper introduces a technique for extracting structure and motion using directionally selective matches between linear features. A world-centered coordinate system is used to make these computations without the intermediate calculation of depth. In order to constrain the possible structure and motion configurations, we assume that the three-dimensional direction of gravity relative to each image frame is known. The direction of gravity, along with the directionally selective linear feature matches, form a set of quadratic equations which can be used to determine structure and motion

Translational Decomposition of Flow Fields

We introduce a low-level description of image motion called the local translational decomposition (LTD). This description associates with image features or small image areas, a three-dimensional unit vector describing the direction of motion of the corresponding environmental feature or small surface area. The local translational decomposition is derived by applying a procedure for processing purely translational motion to small overlapping image areas. This intermediate representation of motion considerably simplifies the inference of motion parameters for ego-motion and can support qualitative inferences for non-rigid motions. We first show how to compute the LTD from optic flow fields and then show how the LTD is used to recover the parameters of rigid body motions. We present three cases for which the recovery of motion parameters is particularly robust: motion constrained to a determined plane (the normal to the plane is known); motion constrained to an undetermined plane (the normal to the plane is not known); arbitrary motion relative to locally planar surfaces. We then discuss techniques for computing the local translational decomposition directly from real image sequences without the initial extraction of optic flow and other areas for future work

Interactive Model-Based Image Understanding

This paper describes a general architecture for an interactive model-based vision system. A human specifies a limited amount of information which establishes a context for autonomous interpretation of images. Object models are described by constraints specifying necessary geometrical properties and relationships between objects. The use of constraints allows for flexible object instantiation. A user can indicate an object in a scene and this directs perceptual processing routines as well as constraining future object instantiations. This interactive model-based concept has been applied to the domain of vehicle tracking, and this paper concludes with several processing examples from this domain

The Knowledge Weasel hypermedia annotation system

We describe the organization and implementation of the Knowledge Weasel (KW) Hypermedia Annotation System which we are using to explore knowledge structuring by collaborative annotation. Knowledge Weasel incorporates many useful features: a common record format for representing annotations in different media for uniform access; dynamic user control of the presentation of annotations as a navigational aid global navigation using queries and local navigation using link following; support for collecting related sets of annotations into groups for contextual referenee and communication. KW purposely leverages off of free, publicly available software so it doesn’t require building specialized tools and also so it can be freely available. We discuss some of the issues involved with annotating non-textual material such as images and sound and conclude with a brief discussion of ongoing and future work

Interactive Model-Based Vehicle Tracking

This paper describes an interactive model-based vision system for vehicle tracking. A human specifies a limited amount of information in the form of object models, which establish a context for autonomous interpretation of scenes containing moving vehicles. The system is able to successfully track vehicles under complex outdoor conditions through the use of gravity, vehicle, and road models. Results are presented from several image sequences shot with hand-held uncalibrated cameras

Automated analysis of the American College of Radiology mammographic accreditation phantom images

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134992/1/mp7992.pd

Association Between Subarachnoid Hemorrhage Outcomes and Number of Cases Treated at California Hospitals

BACKGROUND AND PURPOSE: Studies of several complex medical conditions have shown that outcomes are better at hospitals that treat more cases. We tested the hypothesis that patients with subarachnoid hemorrhage treated at high-volume hospitals have better outcomes. METHODS: Using a database of all admissions to nonfederal hospitals in California from 1990 to 1999, we obtained discharge abstracts for patients with a primary diagnosis of subarachnoid hemorrhage who were admitted through the emergency department. Hospital volume, defined as the average number of subarachnoid hemorrhage cases admitted each year, was divided into quartiles. Rates of mortality, adverse outcomes (death or discharge to long-term care), length of stay, and hospital charges were computed by univariate analysis and by multivariable general estimating equations, with adjustment for demographic and admission characteristics. RESULTS: A total of 12 804 patients were admitted for subarachnoid hemorrhage through the emergency departments of 390 hospitals. Hospital volumes varied from 0 to 8 cases per year in the first quartile to 19 to 70 cases per year in the fourth quartile. The mortality rate in the lowest volume quartile (49%) was larger than that in the highest volume quartile (32%, P\u3c0.001). In multivariable analysis, the difference persisted (odds ratio comparing highest with lowest volume quartiles 0.57, 95% CI 0.48 to 0.67; P\u3c0.001). At higher volume hospitals, lengths of stay were longer, and hospital charges were greater in univariate and multivariable models (all P\u3c0.001). Only 4.8% of those admitted to hospitals in the lowest volume quartile were transferred to hospitals in the highest quartile. CONCLUSIONS: In this study of discharge abstracts in California, hospitals that treated more cases of subarachnoid hemorrhage had substantially lower rates of in-hospital mortality. Few patients with subarachnoid hemorrhage are being transferred to high-volume centers

Association between subarachnoid hemorrhage outcomes and number of cases treated at California hospitals

BACKGROUND AND PURPOSE: Studies of several complex medical conditions have shown that outcomes are better at hospitals that treat more cases. We tested the hypothesis that patients with subarachnoid hemorrhage treated at high-volume hospitals have better outcomes. METHODS: Using a database of all admissions to nonfederal hospitals in California from 1990 to 1999, we obtained discharge abstracts for patients with a primary diagnosis of subarachnoid hemorrhage who were admitted through the emergency department. Hospital volume, defined as the average number of subarachnoid hemorrhage cases admitted each year, was divided into quartiles. Rates of mortality, adverse outcomes (death or discharge to long-term care), length of stay, and hospital charges were computed by univariate analysis and by multivariable general estimating equations, with adjustment for demographic and admission characteristics. RESULTS: A total of 12 804 patients were admitted for subarachnoid hemorrhage through the emergency departments of 390 hospitals. Hospital volumes varied from 0 to 8 cases per year in the first quartile to 19 to 70 cases per year in the fourth quartile. The mortality rate in the lowest volume quartile (49%) was larger than that in the highest volume quartile (32%, P\u3c0.001). In multivariable analysis, the difference persisted (odds ratio comparing highest with lowest volume quartiles 0.57, 95% CI 0.48 to 0.67; P\u3c0.001). At higher volume hospitals, lengths of stay were longer, and hospital charges were greater in univariate and multivariable models (all P\u3c0.001). Only 4.8% of those admitted to hospitals in the lowest volume quartile were transferred to hospitals in the highest quartile. CONCLUSIONS: In this study of discharge abstracts in California, hospitals that treated more cases of subarachnoid hemorrhage had substantially lower rates of in-hospital mortality. Few patients with subarachnoid hemorrhage are being transferred to high-volume centers

Predictors of rehemorrhage after treatment of ruptured intracranial aneurysms: The Cerebral Aneurysm Rerupture After Treatment (CARAT) study

BACKGROUND AND PURPOSE - The primary purpose of intracranial aneurysm treatment is to prevent rupture. Risk factors for rupture after aneurysm treatment have not been clearly established, and the need to completely occlude aneurysms is debated. METHODS - The Cerebral Aneurysm Rerupture After Treatment (CARAT) study is an ambidirectional cohort study of all patients with ruptured intracranial aneurysms treated with coil embolization or surgical clipping at 9 high-volume centers in the United States from 1996 to 1998. All subjects were followed through 2005, and all potential reruptures were adjudicated by a panel of 3 specialists without knowledge of the initial treatment or aneurysm characteristics. Degree of aneurysm occlusion post-treatment was evaluated as a predictor of nonprocedural rerupture in univariate Kaplan-Meier analysis (log-rank test) and in a Cox proportional-hazards model after adjustment for potential confounders and censoring at time of retreatment. RESULTS - Among 1001 patients during a mean of 4.0 years follow-up, there were 19 postprocedural reruptures; median time to rerupture was 3 days and 58% led to death. The degree of aneurysm occlusion after treatment was strongly associated with risk of rerupture (overall risk: 1.1% for complete occlusion, 2.9% for 91% to 99% occlusion, 5.9% for 70% to 90%, 17.6% for \u3c70%; P\u3c0.0001 in univariate and multivariable analysis). Overall risk of rerupture tended to be greater after coil embolization compared with surgical clipping (3.4% versus 1.3%; P=0.092), but the difference did not persist after adjustment (P=0.83). CONCLUSIONS - Degree of aneurysm occlusion after the initial treatment is a strong predictor of the risk of subsequent rupture in patients presenting with subarachnoid hemorrhage, which justifies attempts to completely occlude aneurysms. © 2008 American Heart Association, Inc