Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session V16: Focus Session: Medical Imaging and Related Technologies |
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Sponsoring Units: DBP Chair: Christopher Njeh, Tyler Cancer Center Room: Morial Convention Center 208 |
Thursday, March 13, 2008 11:15AM - 11:51AM |
V16.00001: Overview of Medical Imaging Invited Speaker: The use of radiation probes to image tissues in the human body has progressed through an extraordinary evolution in the past three decades. Beginning with transmission computed tomography in the 1970s, this evolution has included real-time ultrasound, emission computed tomography, magnetic resonance imaging and digital radiography. These advances have recently yielded major improvements in imaging such as multi-detector transmission computed tomography, functional magnetic resonance imaging, dual imaging modalities built on a common platform, and image-guided intervention. These improvements and others have accelerated the usefulness of imaging methods in the early detection, definitive diagnosis, and effective intervention of a wide spectrum of diseases and disabilities. They also have led to increases in radiation doses to patients and the population, an issue of major concern to physicists and physicians. At this time there are four major frontiers for research in medical imaging: (1) molecular imaging; (2) functional imaging; (3) multi-modality imaging; and (4) information management. These research frontiers, together with the use of sophisticated imaging technologies in clinical practice, offer rich professional opportunities for physicists. [Preview Abstract] |
Thursday, March 13, 2008 11:51AM - 12:27PM |
V16.00002: PET Imaging - from Physics to Clinical Molecular Imaging Invited Speaker: From the beginnings many years ago in a few physics laboratories and first applications as a research brain function imager, PET became lately a leading molecular imaging modality used in diagnosis, staging and therapy monitoring of cancer, as well as has increased use in assessment of brain function (early diagnosis of Alzheimer's, etc) and in cardiac function. To assist with anatomic structure map and with absorption correction CT is often used with PET in a duo system. Growing interest in the last 5-10 years in dedicated organ specific PET imagers (breast, prostate, brain, etc) presents again an opportunity to the particle physics instrumentation community to contribute to the important field of medical imaging. In addition to the bulky standard ring structures, compact, economical and high performance mobile imagers are being proposed and build. The latest development in standard PET imaging is introduction of the well known TOF concept enabling clearer tomographic pictures of the patient organs. Development and availability of novel photodetectors such as Silicon PMT immune to magnetic fields offers an exciting opportunity to use PET in conjunction with MRI and fMRI. As before with avalanche photodiodes, particle physics community plays a leading role in developing these devices. The presentation will mostly focus on present and future opportunities for better PET designs based on new technologies and methods: new scintillators, photodetectors, readout, software. [Preview Abstract] |
Thursday, March 13, 2008 12:27PM - 12:39PM |
V16.00003: Room temperature STM imaging in air can damage DNA, even at low tunneling biases and currents John Bechhoefer, Philip Grant, Yuekan Jiao STM images of DNA molecules in air or vacuum at room temperature have been plagued by problems of reproducibility. These difficulties have usually been ascribed to substrate artifacts or tip-related effects. However, the recent discovery that low-energy electron beams cause single-strand breaks in DNA suggests that the tunneling electrons used for STM imaging can damage DNA similarly and could be responsible for many imaging problems. Here, we provide experimental support for such a conclusion. Collecting images from an STM that simultaneously detects light-emission from the tip region, we show that the observed DNA structure changes after the first scan. The organic debris from the DNA quenches the light emission from surface plasmons on the gold substrate. Next, we use an atomic force microscope (AFM) whose stiff tip can be used both for tapping-mode AFM and for STM imaging modes. We assess STM-induced damage by re-imaging the same area in tapping-mode AFM. The bias-dependent change in DNA film thickness correlates with the previously observed rate of DNA strand breaks caused by low-energy electron beams of different energies. [Preview Abstract] |
Thursday, March 13, 2008 12:39PM - 12:51PM |
V16.00004: Tomography of biological interfaces using defocusing microscopy Oscar Mesquita Transparent objects can render visible in a standard bright-field microscope by slightly defocusing the microscope objective. From contrast fluctuations of images defocused in a controlled way one can measure the fluctuation spectrum of biological membranes and living cells surfaces. We extended our previous defocusing theory, valid for small defocusings, to arbitrarily large defocusings. We discovered that we can measure height fluctuations of transparent interfaces selectively, and obtain elastic properties of layered biological membranes separately. As an example, we measured separately the elastic constants associated with the two opposite surfaces of a red blood cell. The technique is very sensitive and allows us to measure the small increase of surface tension on the surface in contact with the glass-slide, as compared to the one of the free surface. Interface roughness (static and dynamic), down to nanometer amplitudes, can be measured selectively with defocusing microscopy in transparent layered materials. [Preview Abstract] |
Thursday, March 13, 2008 12:51PM - 1:03PM |
V16.00005: Terahertz spectroscopy of human skin constituents in suspension Cecil Joseph, Anna Yaroslavsky, Munir Al-Arashi, Andrew Gatesman, Thomas Goyette, Robert Giles Continuous wave terahertz imaging has the potential to offer a non-invasive medical imaging modality for detecting different types of human cancers. The aim of this study was to identify frequencies of interest for continuous wave terahertz imaging of skin cancer. The absorption characteristics of water, collagen, and elastin were studied in the range between 20 and 100cm$^{-1}$. In addition, we have recorded and analyzed the teraherz absorption spectra of several substances that are present in human skin (i.e. tryptophan, tyrosine, melanin, urocanic acid, keratin) and their water suspensions with the goal of using them as biomarkers for skin cancer detection. [Preview Abstract] |
Thursday, March 13, 2008 1:03PM - 1:39PM |
V16.00006: Advances in Medical X-Ray Imaging Invited Speaker: |
Thursday, March 13, 2008 1:39PM - 1:51PM |
V16.00007: Inverse Participation Ratio (IPR) Analysis of Transmission Electron Microscopy (TEM) Images: Quantification of Optical Disorder Strength Due to Nanoscale Refractive Index Fluctuations of Tissues/Cells P. Pradhan, V. Turzhitsky, H. Subramanian, A. Heifetz, D. Damania, J. L. Hoogheem, M. J. Jung, H. K. Roy, V. Backman An IPR analysis technique is developed for the first time to analyze and to quantify TEM images of cells/tissues by projecting them to optical lattices and quantifying their short-range nanoscale refractive index fluctuations. The value of IPR of a finite optical lattice provides the measure of the localization of light due to the lattice refractive index fluctuations. The high resolution ($\sim $1nm) of the TEM technique enables imaging of the nanoscale refractive index fluctuations of thin tissue/cell sample slices ($\sim $50-100 nm ). TEM images have been widely used in biology for pathological and visual observation of cells and sub-cellular structures. However, properties of the nanoscale fluctuations in the images have not been fully understood. Results of our IPR study of human tissue/cell TEM images show that average short range nanoscale refractive index fluctuations in tissues/cells increase ( i.e. increase of the IPR value) with the progress of carcinogenesis. Presently available detection techniques are unable to detect these changes. Potential applications of the IPR analysis to probe other nanoscale biological changes are also discussed. [Preview Abstract] |
Thursday, March 13, 2008 1:51PM - 2:03PM |
V16.00008: Imaging Stem Cell Aggregation Using Digital Holographic Microscopy Emily J. Gardel, Yonas Yemane, Debra Auguste, Vinothan N. Manoharan Stem cells in solution aggregate and self-assemble into spheres of cells called embryoid bodies (EBs). During this process, cells divide, differentiate, and influenced by interactions with other cells both chemically and mechanically. We use a combination of holographic, interferometric, and spectroscopic techniques to visualize EB formation. Such methods track the cells' positions and allow us to measure the rates and mechanisms of aggregation as well as the overall structure of the EB. The goal is to understand how cell-cell interactions influence the self-assembly process as well as the environmental cues responsible for stem cell differentiation. [Preview Abstract] |
Thursday, March 13, 2008 2:03PM - 2:15PM |
V16.00009: Magnetomotive Optical Coherence Elastography for Measuring Biomechanical Properties of Tissue using Magnetic Nanoparticles V. Crecea, A.L. Oldenburg, X. Liang, T.S. Ralston, M.B. Orescanin, M.F. Insana, S.A. Boppart Biomechanical properties of tissue are indicative of health and disease, and the ability to readily measure them is instrumental for the diagnosis of early-stage changes. We present a new method for measuring elastic properties of tissue-like phantoms, which employs Fe$_3$O$_4$ nanoparticles as contrast agents in a technique called magnetomotive optical coherence elastography (MMOCE). PDMS-based samples similar to soft biological tissue (0.5-12 kPa) were prepared, with nanoparticles embedded within their volume. The magnetic nanoparticles are displaced upon probing with an external magnetic field, engaging the sample in axial motion. M-mode MMOCE phase data was acquired concomitantly at a rate of 29 kHz, allowing for the tracking of scatterers in the sample with a displacement sensitivity of 11 nm. The scaterers in the samples underwent underdamped oscillations when the magnetic field was applied step-wise. We extracted the damping constants and the natural frequencies of oscillation (30-200 Hz) from the time-resolved displacement traces. A microindentation apparatus was used to measure the Young's moduli of the samples for validation and calibration with the MMOCE measurements. This novel real-time non-invasive technique affords the potential for \textit{in vivo} studies. [Preview Abstract] |
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