Measurement of bone blood flow using the hydrogen washout Technique-Part I: quantitative evaluation of tissue perfusion in the laboratory rat.

The measurement of blood flow in bone is of interest in both clinical and experimental settings. Such determinations would ideally provide accurate, quantitative, and reproducible data with relatively simple and safe technology, even in the small bones of experimental animals. Methods that provide absolute or quantitative measurements include positron emission tomography, "isotope fractioning" using radioactive or fluorescent-labeled microspheres, and measurement of the rate of washout of diffusible tracers delivered either by injection or inhalation. In this article, we describe in detail a modification of the original Whiteside hydrogen washout technique, using modern hydrogen sensors, a micromanipulator for probe placement, and custom software that greatly simplifies blood flow determination and is effective in the small bones of experimental animals.