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Photoacoustic Tomography: Ultrasonically Breaking through the Optical Diffusion Limit（偏醫學應用） (01:20:03)
| 影片標題: | Photoacoustic Tomography: Ultrasonically Breaking through the Optical Diffusion Limit（偏醫學應用） |
| 影片說明: | Photoacoustic Tomography: Ultrasonically Breaking through the Optical Diffusion Limit Lihong V. Wang, Ph.D. Gene K. Beare Distinguished Professor Optical Imaging Lab, Dept. of Biomedical Engineering, Washington University in St. Louis Email: lhwang@biomed.wustl.edu; URL: http://oilab.seas.wustl.edu We develop photoacoustic imaging technologies for in vivo early-cancer detection and functional or molecular imaging by physically combining non-ionizing electromagnetic and ultrasonic waves. Unlike ionizing x-ray radiation, non-ionizing electromagnetic waves—such as optical and radio waves—pose no health hazard and reveal new contrast mechanisms. Unfortunately, electromagnetic waves in the non-ionizing spectral region do not penetrate biological tissue in straight paths as x-rays do. Consequently, high-resolution tomography based on non-ionizing electromagnetic waves alone—such as confocal microscopy, two-photon microscopy, and optical coherence tomography—is limited to superficial imaging within approximately one optical transport mean free path (~1 mm in the skin) of the surface of scattering biological tissue. Ultrasonic imaging, on the contrary, provides good image resolution but has strong speckle artifacts as well as poor contrast in early-stage tumors. Ultrasound-mediated imaging modalities that combine electromagnetic and ultrasonic waves can synergistically overcome the above limitations. The hybrid modalities provide relatively deep penetration at high ultrasonic resolution and yield speckle-free images with high electromagnetic contrast. In photoacoustic computed tomography, a pulsed broad laser beam illuminates the biological tissue to generate a small but rapid temperature rise, which leads to emission of ultrasonic waves due to thermoelastic expansion. The short-wavelength pulsed ultrasonic waves are then detected by unfocused ultrasonic transducers. High-resolution tomographic images of optical contrast are then formed through image reconstruction. Endogenous optical contrast can be used to quantify the concentration of total hemoglobin, the oxygen saturation of hemoglobin, and the concentration of melanin. Melanoma and other tumors have been imaged in vivo. Exogenous optical contrast can be used to provide molecular imaging and reporter gene imaging. In photoacoustic microscopy, a pulsed laser beam is focused into the biological tissue to generate ultrasonic waves, which are then detected with a focused ultrasonic transducer to form a depth resolved 1D image. Raster scanning yields 3D high-resolution tomographic images. Super-depths beyond the optical diffusion limit have been reached with high spatial resolution. The following skin image was acquired in vivo in a mouse using optical-resolution photoacoustic microscopy. The annual conference on this topic has been doubling in size approximately every three years since 2003 and has become the largest in SPIE’s Photonics West as of 2009. |
| 影片分類: | 研討會議/教育訓練 |
| 演講者: | Washington University in St. Louis Lihong V. Wang Prof. |
| 活動時間: | 2012-12-13 |
| 主辦單位: | 尖端光電中心 |
| 上傳時間: | 2013-10-30 10:52:07 |
| 上傳者: | 王峙中 |
| 觀看次數: | 2767 |
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