John J. Bloomer

Image segmentation via motion vector estimates

In the visual world moving edges in the periphery represent vital pieces of information that directs the human foveation mechanism to selectively gather information around these specific locations. This computationally efficient approach of allocating resources at key locations has inspired computer visionists to develop new target detection and hacking algorithms based on motion detection in image sequences. In this study we implemented a recursive algorithm for estimating motion vector fields for each pixel in a sequence of Digital Subtraction Angiography (DSA) images. Velocity information is used to segment the image and perform linear quadratic and acceleration-based frame interpolation to produce an apparent frame rate increase. Our results demonstrate the feasibility of low-rate digital fluoroscopy hence less exposure risks while preserving image quality. Furthermore the technique can be useful in the medical Picture Archival and Communication Systems (PACS) where image data can be compressed by storing and transmiting only the motion fields associated with the moving pixels. 1.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Visually optimized image reconstruction

Exploiting human visual limitations in image reconstruction significantly reduces computational complexity. Based on a multiresolution pyramid image representation, direct and indirect exploitation of these limitations are attainable. In this study, direct exploitation of the variable acuity feature of the human visual system is achieved through tracking the viewers fovea. Multiresolution images are reconstructed such that high resolution is assigned to a rectangular region, centered at the fovea, with spatial resolution dropping gradually with eccentricity. Indirect exploitation makes use of the human visual sensitivity to abrupt intensity changes (edges) in the image. Accordingly, high resolution need only be preserved within 2X2 pixel neighborhood around the detected edges while low resolution is assigned elsewhere. The amount of savings in the number of pixels rendered could be as high as 98% for the direct exploitation and may exceed 50% (depending on image edge density) for the indirect application.

A high speed static CMOS PLA architecture

A static CMOS programmable-logic-array (PLA) architecture has been developed that enables the realization of high-speed control circuits while at the same time providing the low static power consumption inherent in CMOS technology. The PLA uses a novel circuit configuration and a two-phase clock to latch data between the AND and the OR planes. An 8-input, 13-output, 42-minterm finite state machine has been realized using an automatic generating system, in an area of 0.36 mm/sup 2/. This structure operates from near DC to above 80 MHz.<<ETX>>

Effect of on-board compression on stereo and classification

Application-specific metrics for measuring effect of lossy compression on imagery are defined. Experimental results reveal that even small information loss, as measured by mean- square error, may result in large errors in classification and stereo extraction.

Adaptive pulse rate scheduling for reduced dose X-ray cardiac interventional fluoroscopic procedures

Presents an approach for reducing X-ray absorbed dose during cardiac fluoroscopic interventional procedures. The approach hinges on two main concepts: (1) adapting the X-ray pulse rate to the activity of the organ under investigation (the heart); and (2) maintaining the appearance of a 30-frame/s display rate to the viewer. The first concept was accomplished through the processing of multiple sensor information to determine the onset of the various phases of ventricular motion within the cardiac cycle. For each detected phase of the cardiac cycle, a specific tube pulse rate is assigned or automatically determined (after a learning period) such that high activity phases will have higher tube rate than phases with low activity. In order to maintain a 30-frame/s display rate to the viewer, a last-frame-hold approach was used and the resultant sequence shows minimal jerkiness artifacts as a result of the adaptive-motion-dependent sampling strategy. Preliminary results of the proposed system indicate the possibility of a three-to-one reduction of the tube pulse-rate. This translates to a dose reduction of a similar ratio.<<ETX>>