Chemometric determination of blood parameters using visible-near-infrared spectra.

Visible and near-infrared (NIR) integrating sphere spectroscopy and chemometric multivariate linear regression were applied to determine hematocrit (HCT) and oxygen saturation (SatO2) of circulating human blood. Diffuse transmission, total transmission, and diffuse reflectance were measured and the partial least squares method (PLS) was used for calibration considering different wavelength ranges and selected optical measurement parameters. HCT and SatO2 were changed independently. Each parameter was adjusted to different levels and four designs with blood from different donors were carried out for the calibration with PLS. The calibration included the changes in hemolysis as well as inter-individual differences in cell dimensions and hemoglobin content. At a sample thickness of 0.1 mm the HCT and SatO2 were predicted with a root mean square error (PRMSE) of 1.4% and 2.5%, respectively, using transmission and reflectance spectra and the full Vis-NIR range. Using only diffuse NIR reflectance spectroscopy and a sample thickness of 1 mm, HCT and SatO2 could be predicted with a PRMSE of 1.9% and 2.8%, respectively. Prediction of hemolysis was also possible for one blood sample with a PRMSE of 0.8% and keeping HCT and SatO2 stable with a PRMSE of 0.03%.

A novel device for the non-invasive measurement of free hemoglobin in blood bags.

The production of red blood cell concentrates from human donors is a very expensive procedure and human resources are in short supply. Under perfect storage conditions at a temperature of 2-6 degrees C, a blood bag must be used within 35-49 days (in Germany). Visual inspection of the bag for apparent hemolysis by a blood bank physician is a crucial but subjective quality control assessment. Since an interruption of the cold chain cannot be definitely ruled out, bags are often disposed of prematurely for safety reasons. There is currently no method of testing a closed blood bag with respect to hemolysis for its suitability to be used in a transfusion. The proposed optical measuring device is a hemoglobin sensor which determines the free hemoglobin in standard erythrocyte concentrates without opening the bag. The optical measurements are done on the flexible tube connected to the main bag. The optical measurements were evaluated using standard hemoglobin solutions with an accuracy of 0.005 g/dL. These investigations show that in the future each blood bag can be tested non-invasively for its content of free hemoglobin. This will contribute to decreasing the wastage rate of red blood cell concentrates.

A new system for a combined laser and ultrasound application in neurosurgery.

A new combined Laser and Ultrasound Surgical Therapy (LUST) device suitable for endoscopical coagulation and tissue fragmentation has been developed at the LMTB. The new feature is the simultaneous transmission of laser radiation and ultrasound via flexible silica glass fibers. The ultrasound tissue interaction is based on the well-known CUSA-technology which enables the surgeon to cut various types of tissue with different degrees of effectiveness. Application fields are in oncology, neurosurgery and angioplasty. The laser radiation can be used, for example, for tissue coagulation purposes. With a fiber based LUST-system working at a frequency of 30 kHz, a displacement of 100 microns could be attained at the distal end. (The usual standard CUSA displacement is 10-350 microns.) During in vitro experiments the following tissue fragmentation rates could be achieved: brain tissue 50 mg sec-1, liver 4.5 mg sec-1 and kidney 4 mg sec-1 (displacement of the tip 60 microns; phi 1.3 mm; suction setting: 5 W). Laser radiation up to 25 W was sufficient to coagulate soft tissue. This technology offers new possibilities in minimal invasive surgery. The flexible opto-acoustic waveguide (phi 400-1700 microns) can be bent making areas accessible that were previously inaccessible. Without changing the instrumentation the surgeon can use the laser radiation for tissue coagulation or cutting and the ultrasound for tissue fragmentation and tissue reduction.

The spatial variation of the refractive index in biological cells.

With a phase microscope the phase shift of cells from type L 929 fibroblast and mitochondria from liver cells was measured. Compared to the total phase shift caused by the cell relative to vacuum (approximately 1400 nm) the single phase shift of the mitochondria (approximately 180 nm) is small. Only the nucleus and the membrane of the cell give a visibly different phase shift relative to the mean value of the cell. The Fraunhofer diffraction of the measured phase object is calculated. With a simplified scattering theory, i.e. Rayleigh-Gans Scattering, different phase objects are investigated and their differential cross section is discussed.

[Fluorescence behavior of the cornea with 193 nm excimer laser irradiation]. / Fluoreszenzverhalten der Hornhaut unter 193 nm Excimerlaserbestrahlung.

Fluorescence spectra of human, bovine and porcine corneas were measured under 193 nm excimer laser irradiation. Secondary radiation occurs in the mutagenic range between 260 and 290 nm. In situ measurements via a quartz fiber introduced into the eye to the lens surface showed that secondary radiation in the cataractogenic range between 295 and 320 nm is transmitted by the cornea and reaches the lens. The potential adverse effects of this secondary radiation should be considered when applying 193 nm excimer laser radiation to the cornea.