Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 314)

This bibliography lists 139 reports, articles, and other documents introduced into the NASA scientific and technical information system in August, 1988

Aerospace Medicine and Biology

This bibliography lists 184 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during October 1989. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance

Virtual clinical trials in medical imaging: a review

The accelerating complexity and variety of medical imaging devices and methods have outpaced the ability to evaluate and optimize their design and clinical use. This is a significant and increasing challenge for both scientific investigations and clinical applications. Evaluations would ideally be done using clinical imaging trials. These experiments, however, are often not practical due to ethical limitations, expense, time requirements, or lack of ground truth. Virtual clinical trials (VCTs) (also known as in silico imaging trials or virtual imaging trials) offer an alternative means to efficiently evaluate medical imaging technologies virtually. They do so by simulating the patients, imaging systems, and interpreters. The field of VCTs has been constantly advanced over the past decades in multiple areas. We summarize the major developments and current status of the field of VCTs in medical imaging. We review the core components of a VCT: computational phantoms, simulators of different imaging modalities, and interpretation models. We also highlight some of the applications of VCTs across various imaging modalities

Evaluation of Morphed Human Body Models for Diverse Occupant Safety Analysis

Female, obese, and elderly occupants are at increased risk of injury in vehicle accidents. Human Body Models (HBMs) are used to represent the human anatomy and to study injury mechanisms in mathematical crash test simulations. HBM morphing methods can adjust the anatomical geometry of existing HBMs, enabling HBMs to represent the diverse occupant population, beyond the traditionally considered body sizes.The aims of this thesis were to define and select a diverse population of occupants. Thereafter, select an HBM morphing tool for morphing of the SAFER HBM to individuals in this population; Finally, this population of morphed HBMs was to be validated.The defined target population to be represented by HBMs in occupant injury risk evaluations included individuals of both sexes. The selection was based on occupant injury risks and biomechanical risk factors. The male and female sub-populations include individuals of a wide range of statures and weights and ages from 20 to 80 years. A sample of 27 female and 27 males were selected as the initial population.The parametric HBM morphing tool, developed by University of Michigan Transportation Research Institute, was selected for morphing the SAFER HBM. Sled test results from individual male and female Post Mortem Human Subjects (PMHSs) of a wide range of body sizes were used for validation of morphed HBMs. The SAFER HBM was parametrically morphed to each individual PMHS. Predictions from both morphed and the baseline SAFER HBM were collected in reconstructions of the PMHS tests. HBM kinematics, chest deflections and interaction forces were compared to corresponding test results using CORA cross-correlation rating. Comparison of morphed and baseline HBM results showed that correlation rating was not consistently improved for morphed HBMs. For large, obese, and small female subjects in frontal impacts, and in lateral impacts, morphed HBMs were stiffer than the corresponding PMHSs. \ua0To improve morphed SAFER HBM predictions for diverse occupants, future work will identify and mitigate the sources of the stiff responses through model updates. Sex and age dependent biomechanical properties, as available in literature will be included. Biofidelity criteria for morphed HBMs will be defined and with morphed HBMs meeting these criteria, protective principles increasing the protection of all occupants will be investigated

Energy Subtraction Methods as an Alternative to Conventional X-Ray Angiography

Digital subtraction angiography (DSA) is a technique that is widely used to enhance the visibility of small vessels obscured by background structures by subtracting a mask and contrast image. However, DSA is generally unsuccessful for imaging the heart due to the motion that occurs between mask and contrasted images which cause motion artifacts. An alternative approach known as energy subtraction angiography (ESA) exploits the iodine k-edge by acquiring contrast images with a low and high kV in rapid succession to bring the benefits of DSA without motion artifacts. However, it was concluded that image quality for ESA could not compete with DSA, and the approach was abandoned. In our work we show that conclusions about iodine SNR for ESA were based on limitations of early technical components that are no longer relevant. The goals of this thesis were to: 1) develop a theoretical model of iodine SNR that is independent of technology for DSA and ESA; 2) optimize the iodine SNR for ESA; 3) image ESA in an anthropomorphic phantom. It is concluded that, when these conditions are satisfied, ESA iodine SNR equal to that of DSA for low iodine mass loadings (artery sizes) for the same patient entrance exposure, and therefore may provide alternatives to DSA in situations where motion artifacts are expected to render a study as non-diagnostic, such as in coronary applications. In the future this will have important applications for subtraction imaging of the coronary arteries and other vessels where stenosis is vital to patient health

OPTIMAX 2014 - Radiation dose and image quality optimisation in medical imaging

Medical imaging is a powerful diagnostic tool. Consequently, the number of medical images taken has increased vastly over the past few decades. The most common medical imaging techniques use X-radiation as the primary investigative tool. The main limitation of using X-radiation is associated with the risk of developing cancers. Alongside this, technology has advanced and more centres now use CT scanners; these can incur significant radiation burdens compared with traditional X-ray imaging systems. The net effect is that the population radiation burden is rising steadily. Risk arising from X-radiation for diagnostic medical purposes needs minimising and one way to achieve this is through reducing radiation dose whilst optimising image quality. All ages are affected by risk from X-radiation however the increasing population age highlights the elderly as a new group that may require consideration. Of greatest concern are paediatric patients: firstly they are more sensitive to radiation; secondly their younger age means that the potential detriment to this group is greater. Containment of radiation exposure falls to a number of professionals within medical fields, from those who request imaging to those who produce the image. These staff are supported in their radiation protection role by engineers, physicists and technicians. It is important to realise that radiation protection is currently a major European focus of interest and minimum competence levels in radiation protection for radiographers have been defined through the integrated activities of the EU consortium called MEDRAPET. The outcomes of this project have been used by the European Federation of Radiographer Societies to describe the European Qualifications Framework levels for radiographers in radiation protection. Though variations exist between European countries radiographers and nuclear medicine technologists are normally the professional groups who are responsible for exposing screening populations and patients to X-radiation. As part of their training they learn fundamental principles of radiation protection and theoretical and practical approaches to dose minimisation. However dose minimisation is complex – it is not simply about reducing X-radiation without taking into account major contextual factors. These factors relate to the real world of clinical imaging and include the need to measure clinical image quality and lesion visibility when applying X-radiation dose reduction strategies. This requires the use of validated psychological and physics techniques to measure clinical image quality and lesion perceptibility

LifeChair: A Conductive Fabric Sensor-Based Smart Cushion for Actively Shaping Sitting Posture.

The LifeChair is a smart cushion that provides vibrotactile feedback by actively sensing and classifying sitting postures to encourage upright posture and reduce slouching. The key component of the LifeChair is our novel conductive fabric pressure sensing array. Fabric sensors have been explored in the past, but a full sensing solution for embedded real world use has not been proposed. We have designed our system with commercial use in mind, and as a result, it has a high focus on manufacturability, cost-effectiveness and adaptiveness. We demonstrate the performance of our fabric sensing system by installing it into the LifeChair and comparing its posture detection accuracy with our previous study that implemented a conventional flexible printed PCB-sensing system. In this study, it is shown that the LifeChair can detect all 11 postures across 20 participants with an improved average accuracy of 98.1%, and it demonstrates significantly lower variance when interfacing with different users. We also conduct a performance study with 10 participants to evaluate the effectiveness of the LifeChair device in improving upright posture and reducing slouching. Our performance study demonstrates that the LifeChair is effective in encouraging users to sit upright with an increase of 68.1% in time spent seated upright when vibrotactile feedback is activated

Phantom and computational studies towards the clinical translation of gas in scattering media absorption spectroscopy into neonatal respiratory care

Everything except vacuum is heterogeneous to some extent. Even media that we consider homogeneous (such as pure gases and water) can be taken apart into individual heterogeneities (such as atoms and molecules), which can be distinguished with a sufficiently fine probe. Absorption spectroscopy was extensively used by Robert Bunsen and Gustav Kirchhoff in the 1860’s to separate, identify and measure various chemical substances. They defined a line of research, where traces of elements were just detectable with the aid of specialized instruments like the spectroscope, and since then, the absorption lines have been subject of experimental and theoretical developments. Today, we know that the nature of the absorption lines can be described by quantum mechanical changes induced in the atoms or molecules, and with the advances in light sources and sensing technologies, absorption spectroscopy has become a tremendously useful tool with a wide range of applications. The studies presented in this thesis are related to gas absorption spectroscopy, in particular, a technique called GASMAS, which stands for “GAs in Scattering Media Absorption Spectroscopy”. This spectroscopy technique was introduced in Lund University in 2001 by S. Svanberg’s group, to study the spectral features of gases inside porous or hollowed scattering media, combining laser spectroscopy with sensitive modulation techniques. Unlike solids and liquids, which have a smooth absorption and scattering wavelength dependence (1 − 10 nm), gases exhibit sharp absorptive features (10−4 nm). This difference between the absorption spectra of solid state matter and gases, is the corner stone of this technique. In a typical GASMAS measurement, the laser wavelength is scanned across at least one of the absorption lines of the gas of interest. The small gas absorption signal (embedded in the scattered spectrum from the bulk material) is then filtered from the detected signal, making it possible to retrieve the gas concentrations and study their diffusion dynamics using the principles of the Beer-Lambert law. Although there is evidence of the potential of GASMAS to sense oxygen and water vapor in human cavities, such as the ear, nasal sinuses, lungs, intestines and hip bone, one the most promising clinical applications could be the lung function assessment in neonates. The focus of this thesis is to investigate the potential of translating GASMAS into such an application, combining a computational and experimental approach. Most of the work was done in a collaboration between Biophotonics@Tyndall, the Infant Centre (hosted at the Cork University Maternity Hospital-UCC) and the Swedish industry partner, GPX Medical who have built a pioneering GASMAS instrument, suitable for clinical use. The motivation behind this collaborative work, is to assist clinicians in the monitoring of lung function in premature newborns, as their lungs lack structural and biochemical maturation, which can result in respiratory failure. Currently, the use of GASMAS is limited to observational studies with healthy babies. Thus, the improvement and optimization of the technology depends on feasibility tests with tissue-like models. Phantoms mimicking the geometry and optical properties of the main thoracic organs, were created to study the influence of source detector positioning and chest physiognomy in the GASMAS signals. A functional phantom resembling the anatomy, temperature and humidity of the respiratory zone, was also developed to investigate the potential of GASMAS technique in measuring changes in inflated volume. The optimization of source-detector configurations over the thorax is one of the challenges in the clinical translation of GASMAS. It is crucial to define the optimal probe positioning, to obtain the highest possible signal reaching the detector, which also carries information of the gas absorption in lung tissue. Computational studies are then used to simulate the light transport in accurate anthropomorphic models, which contributes with the understanding of near infra-red interaction with the thorax, and most of all, to find the probe locations for which the detection of gas absorption is feasible, and enhance the data acquisition in future clinical studies. This document includes the theoretical background of GASMAS, the basics of respiratory physiology, and the current methods for clinical monitoring and diagnostics of lung pathologies in neonates. The following two chapters, show how the developed phantom and computational models enable the recreation of different clinical scenarios, suitable for GASMAS studies. The main contribute is the identification of the minimum requirements necessary to further improve and advance towards a GASMAS bedside clinical device, that can potentially be used, for lung function assessment and monitoring in neonatal respiratory health

Aerospace medicine and biology: A cumulative index to a continuing bibliography (supplement 371)

This publication is a cumulative index to the abstracts contained in Supplements 359 through 370 of Aerospace Medicine and Biology: A Continuing Bibliography. It includes seven indexes: subject, personal author, corporate source, foreign technology, contract number, report number, and accession number