Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session CC: Mini-Symposium: Applications of Nuclear Physics from Earth to Outer Space |
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Chair: Cynthia Keppel, Hampton University Room: Jewett Ballroom A-B |
Friday, October 24, 2008 10:30AM - 11:06AM |
CC.00001: Nuclear Physics and Radiobiology - Issues for Humans in Space and on Earth Invited Speaker: Nuclear physics is playing a vital role in human biological applications, specifically in planned space missions, in hadron radiotherapy, and in low dose radiobiology. While seemingly disparate, these and other areas share a common need for the understanding of nuclear interactions in biological systems. Radiobiology continues to provide valuable information that will help develop better methods for using radiation in the treatment of disease as well as provide a scientific basis for radiation protection standards. NASA is now focused on the agency's vision for space exploration encompassing a broad range of human and robotic missions including missions to the Moon, Mars and beyond. As a result, there is a focus on long duration space missions. Protection from hazards of space radiation has been identified as one of the five NASA critical areas for human space flight. The cost effective design of spacecraft demands a very stringent requirement on the optimization process. Exposures from the hazards of severe space radiation in deep space and/or long duration missions are very different from that of low earth orbit, and much needs to be done about their effects. However, it is clear that revolutionary technologies will need to be developed. Here on earth, particulate radiation treatment for cancer, such as proton radiotherapy, is playing an increasing important role, while the biological effectiveness remains less well understood than for x-rays and other forms of medical radiation treatments. Advanced imaging, dosimetric, Monte Carlo, and other techniques from nuclear physics are utilized to study the molecular basis of fractionation dependency and other tumor and normal tissue radiation responses, such as radiosensitivity. Moreover, advances developed by biological research efforts, such as the sequencing of the human genome, have opened new horizons for radiobiology. New techniques have made it possible to determine at the cellular / molecular level how living systems respond even to low doses of radiation. I will discuss the interplay between nuclear physics and human biological applications; Starting with high dose exposure in space applications, to controlled exposure in radiotherapy, and finally, low dose radiobiology. I will project how cellular level living system activities may provide the much needed impact of radiation exposure on living tissues in these applications. [Preview Abstract] |
Friday, October 24, 2008 11:06AM - 11:18AM |
CC.00002: Quantitative and Qualitative Differences in Neurocognitive Impairment Induced by 1 GeV 56Fe Ions and X-Rays R. Britten, S. Mitchell, B. Parris, A. Johnson, S. Singletary-Britten, G. Lonart, R. Drake During the planned mission to Mars, Astronauts will be exposed to heavy charged particles (Hze). Our group has been determining the relative biological effectiveness (RBE) of Hze (1 GeV 56Fe, LET = 150 kev/um) with respect to neurocognitive impairment, specifically spatial memory, short-term working memory and attentional set shifting. Our current data suggest that Hze have RBE values of about 7 for hippocampal-dependent spatial memory tasks (Barnes Maze) and possibly even higher for certain attentional processes. We have also used MALDI-TOF serum profiling analysis to identify several proteins that are biomarkers of both the level and LET of the radiation exposure, and biomarkers of cognitive performance. Our data suggest that Hze particles have a distinctly different impact upon neurocognitive function in rats than do X-rays. From a mission perspective, attentional set shifting is the neurocognitive function most likely to be impacted by the predicted Hze exposure; unfortunately Set shifting underlies our ability to execute complex plans. The proteins identified could be used to monitor the Astronauts for radiation exposure and any associated loss of neurocognitive function, and some may actually give an insight into the complex processes that lead to radiation-induced cognitive impairment. [Preview Abstract] |
Friday, October 24, 2008 11:18AM - 11:30AM |
CC.00003: Biologically Optimized Treatments for Hadron Radiotherapy Vahagn Nazaryan, Cynthia Keppel, Richard Britten, Jerry George, Xiliang Nie Near future advances in proton radiotherapy technology will increasingly require complex, conformal treatment planning. However, the current state of knowledge of the biological efficiency of proton beams may be inadequate to facilitate precision, and reduced margins. A new project at the Hampton University Proton Therapy Institute and the Eastern Virginia Medical School aims to facilitate the expected benefits of increasingly conformal treatment capabilities. Specifically, we seek to establish with measurements the biological depth dose profile of protons with incident energies in the range 62-210 MeV, and to utilize these also to provide vastly improved model algorithms for patient treatment planning based on biological, rather than simply physical, depth dose profiles. A progress report on a model for proton biological efficiency calculations as an input algorithm for treatment planning with protons will be presented. The planned measurements will be discussed. [Preview Abstract] |
Friday, October 24, 2008 11:30AM - 11:42AM |
CC.00004: Variation of Space Radiation Exposure inside Spherical and Hemispherical Geometries Zi-Wei Lin, Younes Baalla, Lawrence Townsend We calculate the space radiation exposure to blood-forming organs everywhere inside a hemispherical dome that represents a lunar habitat. We derive the analytical path length distribution from any point inside a hemispherical or a spherical shell. Because the average path length increases with the distance from the center, the center of the hemispherical dome on the lunar surface has the largest radiation exposure while locations on the inner surface of the dome have the lowest exposure. This conclusion differs from an earlier study on a hemispherical dome but agrees with another earlier study on a spherical-shell shield. We also find that the reduction in the radiation exposure from the center to the inner edge of the dome can be as large as a factor of 3 or more for the radiation from solar particle events while being smaller for the radiation from galactic cosmic rays. [Preview Abstract] |
Friday, October 24, 2008 11:42AM - 11:54AM |
CC.00005: Space and Medical Applications of the Geant4 Simulation Toolkit Joseph Perl Geant4 is a toolkit to simulate the passage of particles through matter. While Geant4 was developed for High Energy Physics (HEP), applications now include Nuclear, Medical and Space Physics. Medical applications have been increasing rapidly due to the overall growth of Monte Carlo in Medical Physics and the unique qualities of Geant4 as an all-particle code able to handle complex geometry, motion and fields with the flexibility of modern programming and an open free source code. Work has included characterizing beams and sources, treatment planning and imaging. The all-particle nature of Geant4 has made it popular for the newest modes of radiation treatment: Proton and Particle therapy. Geant4 has been used by ESA, NASA and JAXA to study radiation effects to spacecraft and personnel. The flexibility of Geant4 has enabled teams to incorporate it into their own applications (SPENVIS MULASSIS space environment from QinetiQ and ESA, RADSAFE simulation from Vanderbilt University and NASA). We provide an overview of applications and discuss how Geant4 has responded to specific challenges of moving from HEP to Medical and Space Physics, including recent work to extend Geant4's energy range to low dose radiobiology. [Preview Abstract] |
Friday, October 24, 2008 11:54AM - 12:06PM |
CC.00006: Radiometric Meteorology: radon progeny as tracers Mark Greenfield, Atsushi Iwata, Nahoko Ito, Kenya Kubo, Kazu Komura, Miho Ishizaki In-situ measurement of atmospheric $\gamma $ radiation from radon progeny determine rain and snow rates to better accuracy than standard rain gauges and gives a handle on how droplets are formed. The measured $\gamma $ ray rates (GRR) have been shown to be proportional to a power of radiometric precipitation rates (RPR)$^{\alpha }$, $\alpha $ giving a handle on the extent to which radon progeny are surface adsorbed or volume absorbed.\footnote{M. B. Greenfield et al., \textbf{J. Appl. Phys. 93}, (2003) pp 5733-5741.} More recently time dependent ratios of GRR from $^{214}$Pb and $^{214}$Bi, concentrated from collected rainwater, have been used to determine the elapsed time since activity from RPR, adhered to rain droplets, was removed from secular equilibrium. Ion exchange resins precipitate out the $^{214}$Pb and $^{214}$Bi ions, which are then filtered from 10s of liters of rainwater or snowmelt. A portable Ge detector is used to integrate the resulting activity over 5-10 min intervals. The measured evolution of these two activities from secular equilibrium to transient equilibrium has meteorological applications enabling both the determination of average elapsed times between the formation of raindrops and the time they reach the ground, as well as an estimate of the initial activity at the source of droplet formation. [Preview Abstract] |
Friday, October 24, 2008 12:06PM - 12:18PM |
CC.00007: Nuclear Resonance Fluorescence from $^{238}$U S. Hammond, C.T. Angell, H.J. Karwowski, C.R. Howell, E. Kwan, G. Rusev, A. Tonchev, W. Tornow, J.H. Kelley Nuclear resonance fluorescence provides unambiguous isotope identification by observing de-excitations of nuclear levels of $\gamma$-ray transitions characteristic of the isotope of interest as high-energy $\gamma$ rays penetrate protective shielding, acting as an identifier of hidden nuclear materials. Using the mono-energetic $\gamma$-ray source at the HI$\gamma$S facility to investigate the nucleus $^{238}$U through the ($\gamma$, $\gamma$') reaction, we measured the widths of low-spin states observed at incident $\gamma$-ray beam energies in the range of 2.94 to 4.40 MeV. [Preview Abstract] |
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