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    Perspectives in blood flow measurement Perspectives in blood flow measurement Presentation Transcript

    • Perspectives in Blood Flow Measurement
      By SuhasDeshpande
      Prof. Druzgalski
      EE 506 (Fall 2009) P3
    • 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
    • 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
    • Measurement techniques
      Electromagnetic methods
      Ultrasonic methods
      Thermal or using tracers methods
      Peripheral or indirect methods
    • 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]
    • 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]
    • 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]
    • 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]
    • 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]
    • Photoplethysmograph probe design
      • The probe detects the reflected light from the subject
      • The IR diode (OP240D Optek) and Phototransistor (LPT85A Siemens) were attached to an ellipsoid plastic sheet 0.5 cm apart
      • Probe attached to the skin using an ECG electrode
      [4]
    • 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]
    • 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]
    • 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]
    • 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]
    • Biotelemetry system
      • System implanted in a strugeon
      [8]
    • 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)