Overview of research program pursued in the Biophotonics and Optical Radiology Research Laboratory: To establish a new biomedical imaging modality as a clinical tool there are two major steps that need to be taken. First, there is the fundamental science and engineering that needs to be performed. Instrumentation has to be developed that provide high-fidelity measurement data than can be analyzed. The raw data obtained needs to be converted into meaningful cross sectional images through the tissues under investigation. To achieve this image reconstruction algorithms have to be conceived, implemented, and tested. Once the instrumentation and algorithms are in place, the practical biomedical applications become into focus. Only if it can be shown that a novel technology is of clinical utility and adds benefits that go beyond existing technology, will the new technology be accepted.
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 scattering and absorption coefficients, mus and mua,
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 ms-values between different tissue. Differences in
chromophore content and concentration lead to different ma-values.
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.
Overview of research program pursued in the Biophotonics and Optical Radiology Research Laboratory: To establish a new biomedical imaging modality as a clinical tool there are two major steps that need to be taken. First, there is the fundamental science and engineering that needs to be performed. Instrumentation has to be developed that provide high-fidelity measurement data than can be analyzed. The raw data obtained needs to be converted into meaningful cross sectional images through the tissues under investigation. To achieve this image reconstruction algorithms have to be conceived, implemented, and tested. Once the instrumentation and algorithms are in place, the practical biomedical applications become into focus. Only if it can be shown that a novel technology is of clinical utility and adds benefits that go beyond existing technology, will the new technology be accepted.