Biomedical subjects
T Krouskop
Publications and source records attributed to T Krouskop.
Elastography: ultrasonic estimation and imaging of the elastic properties of tissues.
The basic principles of using sonographic techniques for imaging the elastic properties of tissues are described, with particular emphasis on elastography. After some preliminaries that describe some basic tissue stiffness measurements and some contrast transfer limitations of strain images are presented, four types of elastograms are described, which include axial strain, lateral strain, modulus and Poisson's ratio elastograms. The strain filter formalism and its utility in understanding the noise performance of the elastographic process is then given, as well as its use for various image improvements. After discussing some main classes of elastographic artefacts, the paper concludes with recent results of tissue elastography in vitro and in vivo.
Elastographic imaging of low-contrast elastic modulus distributions in tissue.
Elastography is a new ultrasonic imaging technique that produces images of the strain distribution in compliant tissues. This strain distribution is derived from ultrasonically estimated longitudinal internal motion induced by an external compression of the tissue. The displayed two-dimensional (2-D) images are called elastograms. In this paper, it is demonstrated that, when signal-to-noise ratio-enhancing techniques are used, elastography is capable of imaging low-contrast elastic modulus tissue structures with high contrast-to-noise ratios. This is demonstrated using both computer simulations and data obtained from 3 days postmortem ovine kidneys in vitro. The elastograms of such organs suggest that the modulus slowly decays from the renal cortex (RC) to the interior of the renal sinus (RS). Such modulus variation is corroborated by independent measurements of the Young's moduli. It is found that the RC is approximately twice as hard as the interior of the RS. We invoke our previous results on elastographic contrast-transfer efficiency to demonstrate that, at low contrast, the elastogram may be interpreted as a quantitative image of the relative Young's modulus distribution.
Applying robotic technology to aid people with severe disabilities.
Researchers at Rice University and the Baylor College of Medicine in Houston have developed a prototype robotic aid for people with severe disabilities, with emphasis on low cost, versatility, and ease of use. Using custom software written for the Macintosh¿ line of personal computers and a custom input device that emulates a mouse, a user can command a modified HERO 2000¿ robot to perform simple fetch and carry tasks in a structured indoor environment. Further interaction with the environment is possible using a household appliance controller that is also interfaced to the computer.
Supine interface pressure in children.
The effectiveness of using 2-inch and 4-inch convoluted foam overlays to protect children from developing pressure sores was investigated in 13 healthy children ranging in age from ten weeks to 13.5 years. Interface pressures were measured under the occipital, sacral, and scapular areas of children as they lay on a standard mattress, then on 2-inch and 4-inch foam overlays. The differences in pressures between the occiput and scapula, occiput and sacrum, and scapula and sacrum were significant (p less than .001), with the highest pressures recorded under the occipital area. Occipital pressures decreased from 45.7mmHg on the standard mattress to 22.3mmHg on the 4-inch overlay in ages 0 to 2, 54.3mmHg to 30.5mmHg in ages 2 to 10, and 78.0mmHg to 42.4mmHg in ages 10 to 14. Sacral pressures were highest in older and larger children, increasing from 17mm Hg in ages 0 to 2 to 34mmHg in ages 10 to 14, and when body surface area was greater than 1m2. These results indicate that the site of greatest pressure changes with increasing age from the occipital area to the sacral area. Therefore, different pressure relief considerations are necessary in treating pediatric patients than in managing pressure under adults.
Salvage of amputation stumps by secondary reconstruction utilizing microsurgical free-tissue transfer.
During a 2-year period, 15 lower and upper extremity amputees were treated by microsurgical free-tissue transfer in an effort to salvage their amputation stumps. Salvage of length and restoration of contour to aid in prosthetic rehabilitation were the two main indications for reconstruction. Included in the 15 transfers were 3 scapular free flaps, 11 latissimus dorsi musculocutaneous flaps, and 1 groin flap. Thirteen of the patients in this group were refitted with prostheses following reconstruction and did well with no pain or skin breakdown of the resurfaced stumps. The follow-up period on these patients averaged 16 months. One patient, in whom the flap succeeded, underwent stump soft-tissue revision and myodesis. One patient, in whom the flap failed, continued to develop recurrent ulceration in his stump. This clinical experience followed an extensive laboratory study of 12 above-knee amputation patients using noninvasive Doppler ultrasound measurements to determine weight-loading and interface-pressure distribution between the stump and the socket of the prostheses and their relation to stump length and circumference.
Synthetic aortas for systemic simulators.
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Standardizing performance-based criteria for support surfaces.
Due to the sparsity of prospective, controlled, clinical studies on the efficacy of and the lack of standardized information about support surfaces, current literature does not clearly define how these surfaces address patient needs. Standardization would help healthcare professionals make better informed decisions about the use of support surfaces. Standardization would also help researchers design and implement controlled, clinical studies by defining characteristics of surface evaluation, making it possible to replicate research activities. The first step toward standardization is to develop a performance-based set of criteria for classifying these surfaces. With respect to the three purposes identified: comfort, postural control and pressure management, only parameters that can be measured noninvasively, have been considered. The nine parameters are life expectancy of the surface, skin moisture control, skin temperature control, redistribution of pressure, product service requirements, fail safety, infection, flammability, and patient/product friction. Specific guidelines for each of these nine parameters are discussed in depth. With testing and evaluation of support surfaces standardized, clinicians will be able to choose a surface to meet the needs of patients the same way they make other treatment decisions: based on outcomes and the results of controlled, clinical studies.