A bone tissue integrated single fibre laser Doppler flowmeter probe

Laser Doppler Flowmetry was developed and evaluated mainly for measuring blood flow in exposed or superficial tissue layers like skin. Results showed large variation coefficients between juxtaposed skin sites with apparently homogeneous blood perfusion. Spatial differences in blood flow as well as anatomical differences probably explain the obtained results. Vasomotion, hereto only discovered with a microscopic technique, was recorded and evaluated for the first time. Similar results had been obtained in previous bone perfusion studies. The LDF technique has also been used extensively for skin irritancy tests and microvascular effects of vasoactive substances and drugs. An in vivo model in calibrating LDF quantitatively showed a linear relationship between LDF output signal and total blood flow in the range 0-300 ml min-1 100 g-1. This quantitative calibration is however tissue specific. Most tissues of interest are not superficial. The single fibre LDF provides additional power in studying deep tissue physiology and trauma-induced changes in regulation of microvascular perfusion. Furthermore long-term studies require implantable and biocompatible probes and this could be fulfilled using the SFLDF technique in combination with a tissue-integrated titanium probe. Implantation of the titanium probes initially creates some trauma to the vascular bed in the bone marrow but almost none in the opposite cortical bone layer. The healing process enhances the blood perfusion during the first weeks. The increased perfusion can be due to different parameters such as angiogenesis. The histological findings support this hypothesis. This gives preference to the tissue-integrated probe where interference with the tissue should be avoided. The integrated probe technique has only been evaluated in bone tissue. Modification of the probe shape and dimension, however, would make it suitable for other tissues as well.