1. Perspectives in Blood Flow Measurement By SuhasDeshpande Prof. Druzgalski EE 506 (Fall 2009) P3
2. Outline About Blood Flow measurement Measurement techniques Electromagnetic methods Thermal methods Tracer dyes for measurement Ultrasound measurement Plethysmograph probe design Blood flow using thermal analysis Biotelemetry system References
3. Blood flow measurement Provides vital info about the oxygen and nutrient supply to the various parts of body More difficult and complicated Most of the methods are invasive techniques Blood flow ranges from 0.45 m/s in the arteries to 0.1 m/s in veins Blood pressure measurement provides supplemental info which can be used
5. Electromagnetic methods Blood being a conductive fluid adheres to the Faraday’s law of electromagnetic induction Flow in a magnetic field results in a generation of electromagnetic force perpendicular to the magnetic field and flow Another technique used is that of Nuclear magnetic resonance [2]
6. Thermal methods A thermistor or a hot wire anemometer can be implanted inside the body. Blood acts as a coolant for a thermistor . By different designs and calculations based on fluid mechanics and heat transfer flow of blood can be estimated [5]
7. Tracer dyes for measurement The injection of some tracers helps in imaging and analyzing the blood flow Indocyanine Green is a dye which causes fluorescence and images the blood flow [6]
8. Ultrasound measurement Blood flow measurement using implantable CMUT Array (Capacitive Micromachined Ultrasonic Transducer) CMUT consists of a SOC cmos electronics and transducer with cross section 40µm and shaft length 4-10mm [1]
9. Experimental operation Ultrasonic pulse transmitted at frequency 1/T Echo is received at time t1 from position 1, t2 from positions 2 The velocity is calculated as c(t2-t1)/2T cosѳ [1]
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11. The IR diode (OP240D Optek) and Phototransistor (LPT85A Siemens) were attached to an ellipsoid plastic sheet 0.5 cm apart
12. Probe attached to the skin using an ECG electrode[4]
13. Blood flow using thermal analysis Arteriola and Venula connected by blood capillaries and AVA Blood flow to capillaries controlled by AVA Temperature regulation is based on blood flow in capillaries Heat transfer model analysis [7]
14. Blood flow in fingertip using heat transfer analysis Non Contact sensor placed below consists of an IR detector (Thermopile and resistance temperature sensor) Sensitivity enhanced by a Ge lens Contact sensor consists of thermistor (0.25mm) to transmit the heat [7]
15. Blood flow in fingertip using heat transfer analysis First step ambient temperature measured (25s) Second step finger placed on the sensor initial temperature of skin surface measured (35s) Third step measure the thermal release characteristics for correction in second step (15s) Blood flow coefficient is calculated by using the temperature gradient in step 2 [7]
16. Biotelemetry system The implant module (B) consists of a doppler flow meter µcontroller and a RF link communicator The base station (A) consists of RF link µcontroller and D-A Converter [8]
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18. References [1] M. Wang, "The initial doppler blood flow measurement using an implantable CMUT array," Proceedings - IEEE Ultrasonics Symposium, pp. 2442, 2007. [2] C. Elkins, "Magnetic resonance velocimetry: Applications of magnetic resonance imaging in the measurement of fluid motion," Exp. Fluids, vol. 43, pp. 823, 2007. [3] K. Nagata. (2009), “Heat transfer analysis for peripheral blood flow measurement system”. Review of scientific instruments 80(6), [4] D. Zikic, "An improved reflective photoplethysmograph probe design for detection of an arterial blood flow," Journal of Medical Engineering Technology, vol. 32, pp. 23, 2008. [5] D. Wei, "Optimal design of a thermistor probe for surface measurement of cerebral blood flow," IEEE Trans. Biomed. Eng., vol. 37, pp. 1159, 1990. [6] M. Miwa, "ICG fluorescence imaging and its medical applications," Proceedings of SPIE--the International Society for Optical Engineering, vol. 7160, 2009. [7] K. Nagata. (2009), “Heat transfer analysis for peripheral blood flow measurement system”. Review of scientific instruments 80(6), [8] A. Gra¨ns, “A fully implantable multi-channel biotelemetry system for measurement of blood flow and temperature: a first evaluation in the green sturgeon,” Hydrobiologia (2009)
