Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session W16: Focus Session: Novel Biomedical Techniques |
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Sponsoring Units: DBP Chair: Paul Gueye, Hampton University Room: Morial Convention Center 208 |
Thursday, March 13, 2008 2:30PM - 3:06PM |
W16.00001: Novel Radiation Sources Based on Ultra-High-Power Lasers: New Capabilities for Radiology and Radiotherapy Invited Speaker: As the maximum power level of compact lasers steadily increases, new opportunities are enabled for their use in bio-medicine and medicine. For instance, the Diocles laser at the University of Nebraska, Lincoln, now produces a peak power of 150-terawatts (1.5x10$^{14}$ W) from a table-top-size system. When light at this power level is focused, it can accelerate electrons, and produce quasi-monoenergetic beams of x-rays, similar to those produced by much larger synchrotron light sources. Such MeV-energy beams create new opportunities in biomedicine, radiology and radiography. Examples to be discussed include structural analysis of bio-molecules, diffraction-enhanced imaging for computed tomography, and radio-sensitization-enhanced radiotherapy. This talk will describe the current status of laser-based x-ray technology, as well as the potential advantages and prospects for their use in medicine. [Preview Abstract] |
Thursday, March 13, 2008 3:06PM - 3:42PM |
W16.00002: New techniques required to understand the by-stander effect in situ. Invited Speaker: The by-stander effect has been known for nearly a century under various names, of which the abscopal effect is probably the most well known. More recently the by-stander effect has received a lot of attention, and various models have been developed to assess the relative importance of the bystander effect in radiation treatment. It is clear that irradiated cells release factors that lead to alterations in the physiology of adjacent irradiated cells, both via inter-cellular junctions and through systemic factors. Most studies that have sought to identify the systemic factors and the cellular mechanisms that are responsible for the bystander effect have by necessity used in vitro systems. The purpose of this presentation is to alert the audience to the various techniques that are available to study the proteomic changes related to the bystander effect in situ. We shall pay attention to the use of MALDI-imaging to track spatial proteomic changes in tissue that have been exposed to microbeams. [Preview Abstract] |
Thursday, March 13, 2008 3:42PM - 3:54PM |
W16.00003: The Physics of Up-Conversion Nanophosphors for Cancer Treatment Shuang-fang Lim, William Ryu, Robert Riehn, Robert Austin Upconversion phosphors are rare-earth containing crystalline materials which can convert infrared light to visible light (hence the name up-conversion), via excitation of real levels of rare earths. They overcome limitations of current organic fluorophors and quantum dots and have unique properties that enable advanced imaging, drug delivery applications and light-based chemotherapy. The process by which near -IR photons (980 nm) are summed in a rare-earth matrix to emit visible light is a fascinating problem in atomic physics combined with solid-state physics. We will present experimental results which probe this non-linear phenomena. [Preview Abstract] |
Thursday, March 13, 2008 3:54PM - 4:06PM |
W16.00004: Disposal of Energy by UV-B Sunscreens Thomas Nordlund, Rajagopal Krishnan Ideal sunscreens absorb dangerous UV light and dispose of the energy safely. ``Safe disposal'' usually means conversion to heat. However, efficient absorption entails a high radiative rate, which implies high energy-transfer and other rates, unless some process intervenes to ``defuse'' the excited state. We studied the excited-state kinetics of three UV-B (290-320 nm) sunscreens by absorption, steady-state and time-resolved fluorescence. Excited-state rate analysis suggests that some sunscreens have low radiative-rate ``dark'' states, in addition to normal excited states.* We deduce dark states when sunscreens of high extinction coefficient do not show lifetimes and total emission consistent with such high radiative rates. A high radiative rate, accompanied by efficient fluorescence emission and/or transfer, may be unfavorable for a sunscreen. In spite of its dark excited state, padimate O shows significant re-emission of light in the UV-A (320-400 nm) and energy transfer to a natural component of excised skin, probably collagen. * Krishnan, R. and T.M. Nordlund (2007) J. Fluoresc. DOI 10.1007/s10895-007-0264-3. [Preview Abstract] |
Thursday, March 13, 2008 4:06PM - 4:42PM |
W16.00005: Microdosimetry of ondividual cells with microbeam facilities Invited Speaker: This abstract has not been submitted. [Preview Abstract] |
Thursday, March 13, 2008 4:42PM - 4:54PM |
W16.00006: Dynamical Systems, Cytokine Storms, and Blood Filtration Glenn Foster, Alfred Hubler Various infections and non-infectious diseases can trigger immune cells and the proteins (cytokines) the cells use to communicate with each other to be caught in a positive feedback loop; this ``cytokine storm'' is frequently fatal. By examining the network of cytokine-immune cell interactions we will illustrate why anti-mediator drugs have been generally ineffective in stopping this feedback. A more effective approach may be to try and reduce interactions by dampening many signals at once by filtering the cytokines out of the blood directly (think dialysis). We will argue that feedback on an out of control nonlinear dynamical system is easier to understand than its normal healthy state and apply filtration to a toy model of immune response. [Preview Abstract] |
Thursday, March 13, 2008 4:54PM - 5:06PM |
W16.00007: Differentiation of benign epithelia, prostatic intraepithelial neoplasia and, stromal region of prostate biopsies using Raman spectroscopy Houbei Dai, Jagdish Thakur, Ratna Naik, Fazlul Sarkar, Wael Sakr, Greg Auner, Alex Cao, Abhilash Pandya, Vaman Naik A pilot study was performed to differentiate the benign epithelia (BE), prostatic intraepithelial neoplasia (PIN) and, stromal regions from deparaffinized prostate needle biopsies using Raman spectroscopy. Raman spectra were collected from six deparaffinized prostate tissues and all the three regions showed different Raman spectral features that may represent unique Raman signatures of these regions. One of the unique features observed in these spectra is that the ratio of the two peak heights at 1449 cm$^{-1}$ and 1338 cm$^{-1}$ is constant with different values for BE and PIN. While the peak at 1338 cm$^{-1}$ is quite weak in the stromal regions. Multivariate statistical methods clearly separated the spectra from three different regions of the tissues into three distinct groups. This study demonstrates the feasibility of using deparaffinized tissue biopsy samples for the diagnostic purpose. [Preview Abstract] |
Thursday, March 13, 2008 5:06PM - 5:18PM |
W16.00008: Medical Applications of the Geant4 Simulation Toolkit Joseph Perl Geant4 is a toolkit for the simulation of the passage of particles through matter. While Geant4 was originally developed for High Energy Physics (HEP), applications now include Nuclear, Space and Medical Physics. Medical applications of Geant4 in North America and throughout the world have been increasing rapidly due to the overall growth of Monte Carlo use 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 and free source code. Work has included characterizing beams and brachytherapy sources, treatment planning, retrospective studies, imaging and validation. This talk will provide an overview of these applications, with a focus on therapy, and will discuss how Geant4 has responded to the specific challenges of moving from HEP to Medical applications. [Preview Abstract] |
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