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This site is a joint effort of COMP, The Greek Organization of Medical Physicists,
and CCPM, The Greek College of Physicists in Medicine
CCPM Symposium Programme - Hamilton 2005
Anatomic, functional, and molecular imaging using optical coherence tomography
Joseph Izatt,
Department of Biomedical Engineering, Duke UniversityOptical Coherence Tomography (OCT) is a novel biomedical imaging technique which uses low-coherence optical interferometry to obtain micron-scale resolution tomographic images of sub-surface tissue structure noninvasively. OCT has become a standard diagnostic tool in clinical ophthalmology, and is under investigation for other clinical applications including cancer detection and evaluation of cardiovascular disease. Within the past few years, dramatic technology advances have increased the performance of OCT systems many-fold, and have also demonstrated the potential for micron-scale functional and molecular imaging in living systems for the first time. We have developed spectral domain OCT scanners capable of imaging up to several times video rate, and applied them for real-time two-dimensional and near real-time three dimensional imaging in human and small animal models. The applications of this new technology for high-throughput noninvasive phenotyping and rapid 3D imaging in small animals and developmental biology models is particularly compelling. In addition, we have developed novel functional imaging extensions to OCT which take advantage of the altered spectral content of elastic and inelastically backscattered light to provide enhanced image contrast. These include the first demonstrations of molecular imaging with OCT, in which an imaging form of pump-probe spectroscopy has been used to image the distributions of genetically expressed proteins with micron resolution in living animals, with sensitivity comparable to multiphoton microscopy.
Diffuse Optical Imaging of the Neuro-Metabolic-Vascular Relationship during Brain Activation
David Boas
Associate Professor of Radiology, Harvard Medical School, Massachusetts General HospitalThe ability and interest in functional imaging of the human brain has grown with the advent of positron emission tomography (PET) and functional magnetic resonance tomography (fMRI). These imaging techniques are leading to a better understanding of the healthy, diseased, and injured functioning brain. Diffuse optical imaging is a non-invasive, portable, and relatively inexpensive method that complements PET and fMRI with the ability to continuously monitor the hemodynamic, metabolic, and possibly neuronal activity state of the brain, and to measure populations of subjects and paradigms not amendable to PET or fMRI. All of these methods are predominantly sensitive to the hemodynamic parameters of the brain which arise from the neuronal and metabolic activity. During this talk, I will discuss the contributions of optical imaging to understanding the relationship between neuronal, metabolic, and vascular activity within the brain. Better knowledge of this relationship will guide the development of better treatments and improve the utility of diagnostic imaging methods.
Imaging Breast Tumor Tissue In Vivo with Diffuse Light: Tumor Tissue Characterization and Monitoring
Brian W. Pogue,
Thayer School of Engineering at Dartmouth CollegeDiffuse optical tomography with near-infrared light has allowed characterization of breast tumor tissue with a number of different constituent parameters, which could have relevance for diagnosis and therapy. Multi-spectral tomography provides quantification of hemoglobin, oxygen saturation, water, and scatterer particle size and density. These parameters are shown for normal and diseased breast tissue, with an eye toward their pathobiological interpretation. The images of tumors present in breast cancer show significant increases in hemoglobin, water and scattering relative to the corresponding normal tissue, and the results of ongoing clinical trials are presented. The scattering particle size is shown to be correlated to the pathologically measured particle sizes in excised breast tissue, and further model-based interpretation of the scatter signal may yield important structural information at the nanometer level in tissue, as measured macroscopically with NIR tomography. Imaging of fluorescence from tissue is also possible and is presented, along with a demonstration of how the technological design can be altered to allow video-rate imaging similar to an ultrasound scanner.
Physics and Biophysics of Photodynamic Therapy
Brian C Wilson
Division of Biophysics and Bioimaging, Ontario Cancer Institute, Department of Medical Biophysics, University of TorontoPhotodynamic therapy (PDT)- the use of light-activated drugs- continues to develop as a viable treatment for solid tumors and dysplasias and for non-oncologic applications. The underlying optical technologies for light generation, delivery and dosimetry are described. The last, in particular, remains challenging. This, together with the measurement of photosensitzer levels in tissue, tissue oxygenation and the biological effects of PDT, has required development of several different techniques and corresponding clinical and pre-clinical instruments. These include fiberoptic-based optical probes, near-infrared luminescence measurement of excited singlet oxygen generated in PDT, measurements of photosensitzer photobleaching, and the use of bioluminescence to assess both tumor (or cell) destruction and gene regulation. Fundamentally new approaches to PDT include the use of ultrafast pulsed lasers for 2-photon excitation of photosensitizers, the use of 'metronomic' (i.e. low dose-rate) drug and light delivery, and tumor-specific targeting using phototherapuetic 'molecular beacons'. Each of these techniques requires multidisciplinary research and development spanning physics, optical engineering, photobiology and clinical specialties.
2/17/2005 3:46:00 PM
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