Biomedical Applications

Team:
Daniela Staiculescu, Vasileios Lakafosis, Li Yang, Catherine Kruesi, Napol Chaisilwattana

Antenna Body Area Networks

Challenges:
  • Power
  • Absorption (SAR): specific allowances of radiation
  • Signal integrity
  • Body is a lossy, complex medium for signal propagation
  • Distortion of radiation pattern close to human?


back to top

Circular patch antenna

  • Disadvantage: low efficiency due to the high dielectric constant:
    • – Low range in confined spaces – OK
  • Silicone coating helps further miniaturization
  • Broadside gain 0.55dB

back to top

Wireless PANs in Medical Applications

The aim is the creation of a patient-centered RF hub that can receive vital signs from patients, concentrate them and send them to a base station in a relatively short range via a wireless personal area network (WPAN). WPANs can be used for connecting to a higher level network and the Internet (uplink) and even for wireless communication among the ECG sensors themselves (intrapersonal communication).

The criteria that are mostly considered for the selection of the most appropriate and efficient protocol in this area are:
  • Data rate
  • Range
  • Low battery power requirement
  • Safety and reliability
  • Security
  • Data Latency
ETSI ERM Task Group 30 – Medical Devices
Its task is to propose and elaborate product specific standards and address frequency allocation matters in relation with radiocommunications applications for medical devices.

back to top

First implementation of 3 lead ECG and temperature sensor node

  • Xbow's MICA wireless sensor node
  • Sensing board on top:
    • Custom 3-lead ECG sensor
    • Medical grade YSI400 temperature probe

back to top

Protocol choices for Transciever


  • Bluetooth ULP (Ultra Low Power)
  • Wireless USB
  • Zigbee
  • Non-proprietory protocols – ANT
  • Multi-hopping
    • body area network
    • patient to patient

back to top

RF Power scavenging

Operation modes:
  • Semi-passive tag:
    • IC uses electromagnetic power distribution
    • Sensor uses battery
    • Increased node's lifetime
  • Active tag:
    • IC and sensor utilize battery
    • Increased data range (>100 ft compared to 30 ft in semi-passive)
    • Improved Signal to Noise ratio → noise immunity in harsh environments

back to top

Energy Sources for Power Scavenging

back to top

Non-Invasive Method Investigation for Blood Pressure Measurements

Cuff
  • Accurate
  • Non-continuous monitoring
  • Discomfort from pressure

Arterial tonometer
  • Applies constant pressure on artery at the wrist
  • Constant pressure creates discomfort

back to top

Challenges of coughless methods

  • Pulse Transit Time method (PTT)
    • The time taken for one arterial pulse pressure wave to travel from aortic valve to peripheral site.
    • Two different blood pressures have to be induced in order to make the method work
  • Detect PTT
    • Pulse Oximeter
      • Diodes emits light and detect absorption of light.
      • Light absorption differ due to SpO2 level and vessel expansion.
    • Impedance sensor
      • Sends current between 2 points to detect impedance change from arterial pulse.
      • Current LifeSync system already contains impedance sensor for detecting respiration.
    • Issues with impedance detection
      • Impedance change can result from stretching skin as in respiratory.
      • How to isolate the change from breathing and blood pulse?

back to top

Sakamoto’s Thorax Model

  • A more accurate non-homogenous physical model contrary to Kubicek’s two cylinder model.
  • Lungs, heart, aorta and veins are represented by geometric shaped contained in an elliptical cylinder defined as the body.
  • The model injects current with a band electrode at the neck.
  • Simulates the different respiratory and cardiac phases through altering the resistivity of the model.

back to top

Proposed Tool: Cylindrical Model

  • Cylinder model with a 100mV point source in the middle bottom developed as a starting point.
  • Multiple point sources defined on outer lower surface of the electrode to simulate band electrode.
  • Objective: develop two electrically parallel, one inside another, to verify the model as well as Kubiceks’ two cylinder formula.
    • Find Zb and Zt separately with the tool, plug in formula.
    • Model Zb and Zt together

back to top

Liquid Antennas for Bio-monitoring Applications

back to top