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Biomedical subjects

J W Eberhard

Publications and source records attributed to J W Eberhard.

6 recordsLinked to original sources
PubMed2002

A calibration approach to glandular tissue composition estimation in digital mammography.

The healthy breast is almost entirely composed of a mixture of fatty, epithelial, and stromal tissues which can be grouped into two distinctly attenuating tissue types: fatty and glandular. Further, the amount of glandular tissue is linked to breast cancer risk, so an objective quantitative analysis of glandular tissue can aid in risk estimation. Highnam and Brady have measured glandular tissue composition objectively. However, they argue that their work should only be used for "relative" tissue measurements unless a careful calibration has been performed. In this work, we perform such a "careful calibration" on a digital mammography system and use it to estimate breast tissue composition of patient breasts. We imaged 0%, 50%, and 100% glandular-equivalent phantoms of varying thicknesses for a number of clinically relevant x-ray techniques on a digital mammography system. From these images, we extracted mean signal and noise levels and computed calibration curves that can be used for quantitative tissue composition estimation. In this way, we calculate the percent glandular composition of a patient breast on a pixelwise basis. This tissue composition estimation method was applied to 23 digital mammograms. We estimated the quantitative impact of different error sources on the estimates of tissue composition. These error sources include compressed breast height estimation error, residual scattered radiation, quantum noise, and beam hardening. Errors in the compressed breast height estimate contribute the most error in tissue composition--on the order of +/-7% for a 4 cm compressed breast height: The spatially varying scattered radiation will contribute quantitatively less error overall, but may be significant in regions near the skinline. It is calculated that for a 4 cm compressed breast height, a residual scatter signal error is mitigated by approximately sixfold in the composition estimate. The error in composition due to the quantum noise, which is the limiting noise source in the system, is shown to be less than 1% glandular for most breasts.

Adipose Tissue↗
PubMed1998

Assessing medically impaired older drivers in a licensing agency setting.

An exploratory study is being conducted jointly by the California Department of Motor Vehicles and the National Highway Traffic Safety Administration to develop a licensing agency assessment battery for elderly drivers with dementia or other aging-related medical conditions. A preliminary battery of nondriving tests and road tests is described; test results for a small pilot sample are presented, and the tests are evaluated in terms of their utility for detecting functional impairment and predicting driving performance. Some considerations that shape construction of a test battery for licensing agency use are discussed in relation to these goals and the givens of a driver licensing environment.

Aged↗
PubMed1998

Crash risks of older drivers: a panel data analysis.

Considerable progress has been made on understanding older drivers' safety issues. None the less, findings from previous research have been rather inconclusive. Differences in data and research methodology have been suggested as factors that contribute to the discrepancies in previous findings. One of the methodological limitations is the lack of considering temporal order between events (i.e. the time between onset of medical condition, symptom and crash). Without time-series data, a 'snap-shot' of medical conditions and driving patterns were often linked to more than 1 year--of crash data, hoping to accumulate enough data on crashes. The interpretation of the results from these studies is difficult in that one cannot explicitly attribute the increase in highway crash rates to medical conditions and/or physical limitations. This paper uses a panel data analysis to identify factors that place older drivers at greater crash risk. Our results show that factors that place female drivers at greater crash risk are different from those influencing male drivers. More risk factors were found to be significant in affecting older men's involvement in crashes than older women. When the analysis controlled for the amount of driving, women who live alone or who experience back pain were found to have a higher crash risk. Similarly, men who are employed, score low on word-recall tests, have a history of glaucoma, or use antidepressant drugs were found to have a higher crash risk. The most influential risk factors in men were the number of miles driven, and use of antidepressants.

Accidents, Traffic↗
PubMed1998

Driving is transportation for most older adults.

The number of people in the United States older than age 65 is expected to double to 60,000,000 within the next 25 years. It is likely that in the future more older persons will drive longer into their lifetimes than they do now. Actions taken now to prepare for this population expansion will have a profound effect on the lives of future older Americans. Functional disabilities among some older people may make it difficult for them to continue to be safely mobile. A crucial issue is to determine who can drive safely and who cannot. A corollary issue is how to rehabilitate those whose functional abilities can be enhanced. For those who cannot be rehabilitated, decisions need to be made on either modifying or stopping driving, and we must facilitate the use of other options that allow older people to remain mobile. The National Highway Traffic Safety Administration and other public and private organizations are now developing programs to enable the public and private sectors to address these issues.

Accidents, Traffic↗