Methods of blood flow measurement in the arterial circulatory system

The most commonly employed techniques for the in vivo measurement of arteri al blood flow to individual organs involve the use of flow probes or sensor s. Commercially available systems for the measurement of in vivo blood flow can be divided into two categories: ultrasonic and electromagnetic. Two ty pes of ultrasonic probes are used. The first type of flow probe measures bl ood flow-mediated Doppler shifts (Doppler flowmetry) in a vessel. The secon d type of flow probe measures the "transit time" required by an emitted ult rasound wave to traverse the vessel and are transit-time volume flow sensor s. Measurement of blood flow in any vessel requires that the flow probe or sensor be highly accurate and exhibit signal linearity over the flow range in the vessel of interest. Moreover, additional desirable features include compact design, size, and weight. An additional important feature for flow probes is that they exhibit good biocompatability; it is imperative for the sensor to behave in an inert manner towards the biological system. A sensi tive and reliable method to assess blood flow in individual organs in the b ody, other than by the use of probes/sensors, is the reference sample metho d that utilizes hematogeneously delivered microspheres. This method has bee n utilized to a large extend to assess regional blood flow in the entire bo dy. Obviously, the purpose of measuring blood flow is to determine the amou nt of blood delivered to a given region per unit time (milliliters per minu te) and it is desirable to achieve this goal by noninvasive methodologies. This, however, is not always possible. This review attempts to offer an ove rview of some of the techniques available for the assessment of regional bl ood flow in the arterial circulatory system and discusses advantages and di sadvantages of these common techniques. (C) 2001 Elsevier Science Inc. All rights reserved.