Robert S. Ledley

Analysis of Cells

Three methods approaching the analysis of cells are described, with applications. The methods presuppose that the picture of the cells has already been digitized and resides in the memory of a computer. The first method is an ad hoc approach in which intercommunicating programmable cursors are utilized for the detection of boundary and area features. The second method is concerned with an evaluation of the curvatures of boundary segments in relation to the overall shape of the boundary. The third method imbeds the picture in a non-Euclidean coordinate system, preserving as invariants salient features while negating the effect of nonsignificant distortions.

Decision theory model of the emergency medical triage process

The major objective of this research project was to apply the scientific discipline of decision-making to the problem of identifying the appropriate receiving hospital for persons injured in accidents. This problem, which is usually referred to as the prehospital triage process, is enormously important in terms of maximizing the critically injured patients chances for survival. The long term objective of this research program, for which this project was a pilot study, is to develop an interactive computer system to support decisions regarding triage of patients at the scene of medical emergencies. The completed system will offer guidance to the paramedic in deciding whether to transport the emergency victim to the nearest hospital for stabilization and further evaluation or directly to the hospital best equipped to deal with the specific conditions of the victim.

Processing of stereo image pairs: elimination of depth planes using the 'cut-plane' procedure

We discuss an approach to detect a 3D position or shape by reconstructing real images at multiple positions from a holographic fringe pattern produced on a charge-coupled device (CCD) camera. The calculation of the intensity distribution on a real image at a certain position can be performed by making the Fresnel transformation of the holographic fringe pattern. It is possible to detect the position of an object by comparing reconstructed images at multiple positions and by picking up one having peak intensity in them. In this paper, an approach to position detection using reconstructed images from a holographic fringe pattern and Fresnel transformation for image reconstruction are described. As experimental results, image reconstructions from holographic fringe patterns produced with one or two point light sources are shown. In conclusion, we discuss the accuracy of this method on z position.

SMIS - a real-time stereoscopic medical imaging system

In this paper, we present an X-ray radiography system which can provide intra-operative stereo imaging of the patients operational area during a spinal surgery. We use two horizontally separated X-ray tubes and a flat-panel X-ray detector mounted on two ends of a C-arm microcontroller synchronizes the image acquisition, and the left and right images are grabbed into the system alternately. Surgeons can have a 3D perception of the spines X-ray image in real-time. We further developed a whole image processing language called PPL. PPL takes images as operands instead of dealing with complex pixel operation. To speed up the rendering speed in a network environment, we proposed a level of detail (LOD) with reverse prediction method that can fast transmit images over Internet in real-time.

Cost containment in the concentrated care center: A study of nursing, bed and patient assignment policies

In an effort to deliver the best possible care to seriously ill patients in the most cost-effective manner, Georgetown University has developed the Concentrated Care Center (CCC) as an essential component of the medical center complex. The design of the CCC, together with the application of controlled variable staffing procedures, permits considerable flexibility in the assignment of nurses (as well as patients) to individual units. This report outlines certain research hypotheses regarding policies designed to increase the cost-effectiveness of patient care in the CCC environment. Statistical techniques based on the theory of stochastic processes are developed to test these hypotheses and a FORTRAN IV computer program is developed to analyze one year of operational data from the CCC.

Derivative of Gaussian functions as receptive field models for disparity sensitive neurons of the visual cortex

Non-symmetric Gabor functions are particularly useful neurophysiologic models of simple cell receptive fields which respond to disparity characteristics of visual stimuli. The left and right visual channels of these simple cell have receptive field profiles which are phase-shifted alterations of the same one-dimensional Gabor function. These profiles resemble derivative of Gaussian (DOG) functions, although DOG functions have never been evaluated using neurophysiologic data from disparity sensitive neurons. Here the authors demonstrate (a) the space frequency response characteristics of DOG functions as a model of a single receptive field, and (b) the space-frequency response characteristics of the combinations of two same-order DOG functions as a model of a simple cell disparity neuron which combine left and right receptive fields. Combining left and right visual fields in four different ways resulted in two characteristic patterns for both even and odd ordered derivatives. Each pattern appeared to be useful, in a different way, for detecting disparity information. These results suggest that DOG functions can be used to produce a set of equations for detecting disparity information.

Pre-processing stereo transparent images: extraction of non-transparent regions by variable length pattern correspondence

One of the hallmarks of a transparent image is the superimposition of structures in the image. This gives the image its see through character. However, portions of a transparent image can be considered non-transparent if no superimposed structures are present. By defining a new type of pixel uniqueness, which the authors call pattern uniqueness, the nontransparent portions of transparent images can be identified, and either removed to clarify the adjacent image features or used as templates to find and separate superimposed structures. Several adjustable criteria were defined in order to optimize the algorithms performance: main parameters include two types of pattern similarity and minimum pattern cohesiveness. Simulated stereo image lines were processed by the algorithm with various parameter settings. An analysis of variance determined the influence of parameter alteration on algorithmic performance. It was found that the matching similarity, cohesiveness, and interaction between these variables were very important and could be adjusted to optimize noise tolerance and performance.

Processing of medical images in compressed format

Hundreds of thousands of medical images are produced daily in the United States and must be stored. In addition, many of these images must be processed. Due to the large volume, such processing can strain even current computer capabilities. However, these images will be stored in compressed format to conserve memory storage space in the near future. Compression ratios of 50 to 100 to 1 are not uncommon. Because medical images will be available in compressed format and to help accelerate the processing of medical images, we are proposing that the image processing be carried out on the greatly restricted number of compressed parameters rather than on the pixels themselves as is usual. The processing of the substantially smaller number of compressed parameters for an image should be faster in many cases than the processing of images in a pixel by pixel mode. The feasibility of this approach is discussed based upon components of the JPEG image compression standard.

A physician questionnaire study of the net cost of computerized tomographic scanning.

This paper reports the results of a physician questionnaire study of the net cost impact of CT Scanning on the health care system. The study objective is accomplished by questioning physicians, on a case-by-case basis, on the number and type of diagnostic tests and hospital care which would have been provided in lieu of CT. These findings indicate that CT Scanning, while expensive on a per use basis, results in significant cost savings on a per case basis because it eliminates the need for multiple alternative tests and hospital stays. Finally, the controversy over the cost of CT Scanning is attributed not to the intrinsic merits of CT but rather to structural elements within the health care system which create disincentives to economize.