The Biophotonic and Optical Radiology Laboratory focuses on the development of state-of-the-art imaging hardware and software for a novel medical imaging modality commonly referred to as Optical Tomography (OT). This technology is based on delivering low energy electromagnetic radiation, in the near-infrared (NIR) wavelength range (700 nm < l < 900nm), to one or more locations on the surface of the body and measuring transmitted and/or back-reflected intensities. The propagation of light in biomedical tissue is governed by the spatially varying scattering and absorption properties of the medium, which are described in the framework of absorption and scattering coefficients, respectively. Differences in the refractive index between intracellular and extra cellular fluids, and various sub-cellular components, such as mitochondria or nuclei, as well as varying tissue densities give rise to differences in scattering coefficients between different tissue. Differences in chromophore content and concentration lead to different absorption coefficients. Based on measurements of transmitted and reflected light intensities on the surface of the medium, a reconstruction of the spatial distribution of these optical properties inside the medium is attempted.
Optical tomography offers several advantages over currently existing imaging modalities, such as X-ray computerized tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), single photon emission computed tomography (SPECT), and ultrasound (US) imaging. For example, the comparatively high speed of the data acquisition allows sub-second imaging of spatio-temporal changes of many physiological processes not accessible with other techniques. Various different contrast mechanisms complement already available imaging modalities, and the use harmless non-ionizing radiation offers a valuable alternative to other imaging procedures. In addition, the instrumentation is available at a lower cost and portable. In initial clinical trials, performed by various groups around the world, optical tomography has shown great promise for brain-blood-oxygenation monitoring in preterm infants, hematoma detection and location, cognition analysis, breast cancer diagnosis, joint imaging, and, most recently, fluorescence enhanced molecular imaging.
But OT remains a very challenging imaging modality because NIR light is strongly scattered in biological tissues, in addition to being absorbed. This results in two major problems. First, only very small amounts of light are transmitted through various body parts, such as the brain or the breast. This poses special demands on detector technology. Secondly, standard backprojection algorithms, as employed in X-ray based computerized tomography (CT), have limited applicability, and more complex image reconstruction algorithms need to be employed. Therefore, any research program in OT will have to address these fundamental challenges in instrument and algorithm design, in addition to proving clinical utility for a variety of applications.
Browse through this website for descriptions of some of the projects currently under investigation at the Biophotonics and Optical Radiology Laboratory. We also provide information on the members of the Lab, a comprehensive list of publications, and information on how to contact us for further information.