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U Netz

Publications and source records attributed to U Netz.

4 recordsLinked to original sources
PubMed2002

Near-infrared diffuse optical tomography.

Diffuse optical tomography (DOT) is emerging as a viable new biomedical imaging modality. Using near-infrared (NIR) light, this technique probes absorption as well as scattering properties of biological tissues. First commercial instruments are now available that allow users to obtain cross-sectional and volumetric views of various body parts. Currently, the main applications are brain, breast, limb, joint, and fluorescence/bioluminescence imaging. Although the spatial resolution is limited when compared with other imaging modalities, such as magnetic resonance imaging (MRI) or X-ray computerized tomography (CT), DOT provides access to a variety of physiological parameters that otherwise are not accessible, including sub-second imaging of hemodynamics and other fast-changing processes. Furthermore, DOT can be realized in compact, portable instrumentation that allows for bedside monitoring at relatively low cost. In this paper, we present an overview of current state-of-the -art technology, including hardware and image-reconstruction algorithms, and focus on applications in brain and joint imaging. In addition, we present recent results of work on optical tomographic imaging in small animals.

Algorithms↗
PubMed2001

[Initial studies of the application of the linear signal transfer theory in evaluating diaphanoscopic examinations exemplified by rheumatism diagnosis].

Rheumatoid arthritis affecting the small joints--in particular the fingers--has advantageous geometry for the transmission of near-infrared (NIR) light. Examination of the optical properties of tissues has revealed that as a result of changes to the capsule and synovial fluid there is a considerable increase in photon scattering already in the early stages of the disease--in particular around 685 nm. This suggests the appropriateness of analysing the photon density profile resulting from punctiform irradiation of the joint. In a first approximation, the point spread function of transmitted photon density is confirmed to be proportional to a Gauss distribution, as suggested by Arridge. In accordance with the linear signal transfer theory, therefore, it is possible to establish a virtual transfer system described by a first-order differential equation. (The tissue optical conditions mu a << mu's and mu a = constant (mu a = absorption coefficient) were assumed). The parameter mu's (= reduced scattering coefficient) was determined by linear approximation of the Gauss distribution to the calculated or measured point spread function. For selected patient data, the mu's was determined in healthy and diseased finger joints (e.g. 10.1 cm-1 and 26.8 cm-1, respectively), and the results were in good agreement with those obtained experimentally.

Arthritis, Rheumatoid↗
PubMedDate not supplied

An initial assessment of the optical properties of human laryngeal tissue.

The optical properties of human laryngeal tissue have been examined over the whole wavelength range from 400 to 2,200 nm to facilitate the development of new laser applications. Tissue samples were taken from healthy vocal fold and from vocal fold of patients with papillomatosis and with chronic, nonspecific laryngitis. The transmission and scattering properties of the tissue samples were recorded with a computer-guided integrating-sphere system. From the measured data the optical properties were calculated by means of the inverse Monte Carlo simulation. In the 500- to 600-nm range papilloma tissues had a considerably higher absorption than healthy vocal fold. When applying the optical tissue properties as a possible influencing factor of the effectiveness of laser systems, laser applications at this wavelength range may be useful in the ablation of papilloma tissue.

Anisotropy↗