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Biomedical subjects

W A Barrett

Publications and source records attributed to W A Barrett.

7 recordsLinked to original sources
PubMed1997

Interactive live-wire boundary extraction.

Live-wire segmentation is a new interactive tool for efficient, accurate and reproducible boundary extraction which requires minimal user input with a mouse. Optimal boundaries are computed and selected at interactive rates as the user moves the mouse starting from a manually specified seed point. When the mouse position comes into the proximity of an object edge, a 'live-wire' boundary snaps to, and wraps around the object of interest. The input of a new seed point 'freezes' the selected boundary segment and the process is repeated until the boundary is complete. Two novel enhancements to the basic live-wire methodology include boundary cooling and on-the-fly training. Data-driven boundary cooling generates seed points automatically and further reduces user input. On-the-fly training adapts the dynamic boundary to edges of current interest. Using the live-wire technique, boundaries are extracted in one-fifth of the time required for manual tracing, but with 4.4 times greater accuracy and 4.8 times greater reproducibility. In particular, interobserver reproducibility using the live-wire tool is 3.8 times greater than intraobserver reproducibility using manual tracing.

Brain↗
PubMedDate not supplied

A PC-based 3D imaging system: algorithms, software, and hardware considerations.

Three-dimensional (3D) imaging in medicine is known to produce easily and quickly derivable medically relevant information, especially in complex situations. We intend to demonstrate in this paper, that with an appropriate choice of approaches and a proper design of algorithms and software, it is possible to develop a low-cost 3D imaging system that can provide a level of performance sufficient to meet the daily case load in an individual or even group-practice situation. We describe hardware considerations of a generic system and give an example of a specific system we used for our implementation. Given a 3D image as a stack of slices, we generate a packed binary cubic voxel array, by combining segmentation (density thresholding), interpolation, and packing in an efficient way. Since threshold-based segmentation is very often not perfect, object-like structures and noise clutter the binary scene. We utilize an effective mechanism to isolate the object from this clutter by tracking a specified, connected surface of the object. The surface description thus obtained is rendered to create a depiction of the surface on a 2D display screen. Efficient implementation of hidden-part removal and image-space shading and a simple and fast antialiasing technique provide a level of performance which otherwise would not have been possible in a PC environment. We outline our software emphasizing some design aspects and present some clinical examples.

Algorithms↗
PubMedDate not supplied

Analysis and correction of imperfections in the image intensifier-TV-digitizer imaging chain.

Image intensifier-television-video digitizer (IITVD) systems are commonly used for digital planar image acquisition in radiology. However, the well-known distortions inherent in these systems limit their utility in research and in some clinical applications where quantitatively correct images are required. Software correction techniques have been implemented which restore both the spatial and grey scale quantitative integrity, allowing IITVD systems to be used as analytical research tools. Previously reported and novel correction techniques were used to reduce veiling glare, pincushion distortion, dc bias, and residual shading effects. The results indicate that excellent quantitative integrity can be achieved when these straightforward artifact reduction techniques are employed.

Analog-Digital Conversion↗
PubMedDate not supplied

Topographic study of sudanophilic lesions in cholesterol-fed minipigs by image analysis.

A new morphometric technique using image analysis has been developed to express the topographic distribution of atherosclerotic lesions in unambiguous statistical terms. Computer-stored images of opened Sudan IV-stained aortas and iliac and coronary arteries from hypercholesterolemic minipigs (n = 39) were used in this study. The image processing methods included transformation of the data to standard templates, automated image segmentation, and creation of probability-of-occurrence maps. These maps have shown that sudanophilic lesions are localized with a characteristic topography along the aortas and iliac and coronary arteries. Areas of high probability are associated with the entrance regions of vessels and the lateral leading edges of the major flow dividers. Regions immediately distal to large branches were found to be areas of low probability. Despite the association of areas of sudanophilia with entrance regions and branch points, a major portion of sudanophilic lesions was not associated with any orifice region (e.g., ductus scar, dorsolateral surface of abdominal aorta, and ventral surface of terminal aorta). The present study provides the necessary information for the development of a rational sampling strategy for the experimental study of the distribution of localizing factors (e.g., hemodynamic, biochemical, cellular, mass transport, histological) and their relationships to putative atherogenic mechanisms.

Animals↗