Estimating the 3D skeletons and transverse areas of coronary arteries from biplane angiograms

A method for estimating the three-dimensional (3D) skeletons and transverse areas of the lumens of coronary arteries from digital X-ray angiograms is described. The method is based on the use of a 3D generalized cylinder (GC) consisting of a series of 3D elliptical disks transverse to and centered on a 3D skeleton (medial axis) of the coronary arteries. The estimates of the transverse areas are based on a nonlinear least-squares-error estimation technique described by D.W. Marquardt (1963). This method exploits densitometric profiles, boundary estimates, and the orientation of the arterial skeleton in 3-space and includes an automatic artery tracking procedure. It applies an adaptive window to the densitometric profile data that are used in the parameter estimation. Preliminary experimental tests of the procedure on angiograms of in vivo human coronaries and on synthetic images yield encouraging results.     

Pressure-induced conversion of α-connectin to β-connectin

The mechanism of the pressure-induced tenderization of meat has not been fully established in spite of its beneficial effect. To detect the changes in the large structural proteins of the myofibrils induced by pressurization without heat treatment, high hydrostatic pressure (100-300 MPa) was applied to rabbit at-death skeletal muscle for 10 min at low temperature (0-2°C). Significant differences in the electrophoretic pattern of connectin (also called titin) in isolated myofibrils were observed between the control and pressurized muscle samples. The conversion of α-connectin (2800 kDa) to β-connectin (2100 kDa) was accelerated with increasing pressure applied to the muscle; also nebulin (800 kDa) was degraded by pressure treatment. From the results it is clear that the degradation of connectin is induced by pressurization alone without heat treatment. If the conversion of α-connectin to β-connectin during conditioning has some influence on meat tenderization, the pressure-induced conversion of α- to β-connectin is possibly one of the causes of pressure-induced tenderization of meat.     

Correction of T2 distortion in multi-excitation RARE sequence

Correction schemes have been implemented to correct for T2 distortions in a multiexcitation RARE (rapid acquisition with relaxation enhancement) sequence where data from multiple echoes and multiple excitations are combined. Computer simulation studies and human imaging studies have been conducted to develop and test the correction procedures. A direct method and an iterative technique have been investigated. The direct technique utilizes Hermitian symmetry of the T2 weighted data and is shown to reduce distortions in T2 weighted images. The iterative scheme begins with an estimation of T2, wherefrom k-space data are computed and compared to the true data to provide error images. The error images are then used to refine iteratively the reconstructed images at a specified echo time. The iterative procedure has been used to improve T1 weighted images acquired through a sequence based on acquisition of two half-plane Fourier samples. These correction techniques should enable a practical implementation of RARE for producing T1 and T2 weighted images comparable to standard spin echo images.     

Standing up to the big squeeze

Consumer confidence is at its lowest ebb since 1980. Economic growth is at a standstill & unemployment & inflation are both rising. Here's a front-line report from more than three dozen operators who are fending off the recession's dual pressures of slow sales & rising costs. They are using discount pricing, partnering with vendors, setting pay for performance standards & a variety of other recession-beating practices.     

Goodwin House, a place for healing

The following report is excerpted from a senior thesis project prepared by Kirstin Shank. For her thesis, Shank produced an exceptionally thorough and thoughtful proposal for a home for people living with AIDS and HIV. The specifics of her plan may not be easily translated for all such centers, but her holistic approach to designing a therapeutic environment can indeed serve as a models for designers across the country grappling with similar challenges.     

Vector-extrapolated fast maximum likelihood estimation algorithms for emission tomography

A new class of fast maximum-likelihood estimation (MLE) algorithms for emission computed tomography (ECT) is developed. In these cyclic iterative algorithms, vector extrapolation techniques are integrated with the iterations in gradient-based MLE algorithms, with the objective of accelerating the convergence of the base iterations. This results in a substantial reduction in the effective number of base iterations required for obtaining an emission density estimate of specified quality. The mathematical theory behind the minimal polynomial and reduced rank vector extrapolation techniques, in the context of emission tomography, is presented. These extrapolation techniques are implemented in a positron emission tomography system. The new algorithms are evaluated using computer experiments, with measurements taken from simulated phantoms. It is shown that, with minimal additional computations, the proposed approach results in substantial improvement in reconstruction.     

Effective vehicle width in self-paced tracking

In self-paced tracking tasks, such as driving, the speed is related to the lateral tolerance. This lateral tolerance has been varied in two ways in previous studies by changing the track width for constant vehicle width and vice versa. The current study used both an automobile driving task and a computer/mouse task to show that these two ways of varying lateral tolerance did not produce equivalent results. Subjects behaved as if vehicle width were less important than track width. Speeds and errors both increased as vehicle width increased for a constant lateral tolerance. This could have safety consequences when driving in confined spaces.