The rate of blood flow in the skin has relevance to several cardiovascular conditions of clinical significance. However, there is no accepted fast, easy way to noninvasively measure the volumetric rate of blood flow per unit tissue volume. Previous work has suggested the potential for using skin heating from radio frequency (RF) energy in the millimeter wave (MMW) band, with simultaneous monitoring of skin surface temperature as a means for noninvasive skin blood flow measurement. This work presents a design and in vitro test results for a simple transducer for MMW blood flow measurement. The transducer consists of a Ka band microstrip antenna and an infrared temperature sensor integrated in a thermoplastic housing. A prototype was tested in a controlled flow chamber, using a commercial tissue phantom material. The device was tested at eight flow rates ranging from 0.25 ml min−1 to 20 ml min−1, equivalent to approximately 10–800 ml min−1·per 100 cm3 of tissue. The differences in temperature increase at exposure time t=60 s were statistically significant (n = 5) so as to allow resolution of flow rates of 0.25, 0.50, 1.0, 2.0, 10, and 20 ml min−1. The ensemble average of temperature increase versus time over the 60 s exposure window were described by a simple two-parameter lumped model which can be correlated with the flow rate. The flow rate model parameter does not scale directly with the flow in the experimental chamber however. This may suggest limitations either in the model or the experimental procedure.

Peripheral Artery Disease (PAD) is a widespread and often undiagnosed condition associated with increased incidence of serious cardiovascular events. Current diagnostic tests for PAD may not be adequate for screening the large at-risk population. A new skin blood flow measurement technique using RF heating in the millimeter wave band, with simultaneous surface temperature measurement offers a potential method for screening individuals at risk for PAD quickly and easily. The feasibility of a transducer design incorporating a microstrip antenna and one or more infrared temperature sensors was evaluated in vitro, using a phantom skin material and a custom flow chamber. Results demonstrate the ability to heat the unperfused phantom by up to 7°C in less than 60 s, depending on antenna separation distance from the target surface. At a distance of 2 mm, preliminary results indicate the rate of temperature increase is sensitive to flowrate. These results suggest a possible method for noninvasive screening of individuals for PAD that is quick, easy and inexpensive.