<ul><li>If the electric or muscular function of the heart is disturbed for some reason, it will affect how the electric signals spread through the heart muscle. </li></ul>ECK -- electrocardiogram
<ul><li>The heart's electrical axis refers to the general direction of the heart's depolarization wavefront (or mean electrical vector) in the frontal plane. </li></ul>ECK -- electrocardiogram Lead I. Lead II. Lead III.
<ul><li>These three bipolar limb leads roughly form an equilateral triangle (with the heart at the center) that is called Einthoven's triangle in honor of Willem Einthoven who developed the electrocardiogram in 1901. </li></ul>ECK -- electrocardiogram
Negative electrode on the right arm and the positive electrode on the left arm ECK -- electrocardiogram Negative electrode on the right arm and the positive electrode on the left leg. Negative electrode on the left arm and the positive electrode on the left leg. Different directions during the EKG measurement Maximal positive deflection is obtained in lead III when the depolarization wave travels parallel to the axis between the left arm and left leg.
ECK -- electrocardiogram The realtively small P wave is produced by electrical currents generated just before contraction of the atria EKG Accoustic QRS complex is caused by currents generated in the ventricles during depolarization just prior to venticular contraction. R is the most prominent component of this wave complex.
ECK -- electrocardiogram 160 ms 300 ms 830 ms 370 ms
ECK -- electrocardiogram positive deflection on the ECG negative deflection on the ECG equiphasic complex deflection on the ECG Snap coated with Ag/AgCl External snap Adhesive layer Gel soaked sponge
ECK -- electrocardiogram A transducer AgCl electrode, which convert ECG into electrical voltage. The voltage is in the range of 1 mV ~ 5 mV Instrumentation amplifier, which has a very high CMRR (90dB) ( common-mode rejection ratio ) and high gain (1000), with power supply +9V and -9V. An opto-coupler to isolate the In-Amp and Output. Bandpass filter of 0.04 Hz to 150 Hz filter. It’s implemented by cascading a low-pass filter and a high pass filter
Impedance cardiogram High-frequency = 40-100 KHz Constant current = 4 mA Impedance changes Z0 value is the total impedance between the two inner leads dZ/dt Amplifier Differentiatior
Impedance cardiogram ventricular ejection time R-Z is the time interval from the R wave of the ECG to maximum ejection as indicated by the peak of dZ/dt
<ul><li>Part of automated external defibrillator </li></ul><ul><li>Investigate circulatory system problems: valve defects, right-left shunting, congestive failure </li></ul><ul><li>Impedance of the thorax can be considered to be divided into two parts: </li></ul><ul><ul><li>the impedance of both tissue and fluids </li></ul></ul><ul><ul><li>the amount and distribution of blood The amount of blood in the thorax changes as a function of the heart cycle. The changes in the distribution of blood in the thorax as a function of the heart cycle can be determined by measuring the impedance changes of the thorax. </li></ul></ul>ECK -- electrocardiogram Band electrodes
ECK -- electrocardiogram A X100 transistor amplifier is followed by a zero cross detector circuit, using a voltage comparator. The output is a TTL logic signal, corresponding to the received 40KHz signal.
<ul><li>This crystal controlled circuit drives a 40KHz piezoelectric transducer with a 30v peak to peak signal. </li></ul>ECK -- electrocardiogram
<ul><li>Magnetometers based on dc SQUIDs are currently the most sensitive sensors for magnetic fields, achieving a magnetic field resolution which is about a billion times below the earth's magnetic field. </li></ul><ul><li>A dc SQUID basically consists of a superconducting ring interrupted by two weak links called Josephson junctions. </li></ul><ul><li>SQUID can be viewed as a flux-to-voltage converter. </li></ul>ECK -- electrocardiogram
ECK -- electrocardiogram noise in an industrial environment, measured with an unshielded multiloop magnetometer The magnetometer's intrinsic noise level is several orders of magnitude lower.
<ul><li>The SQUID ring itself is enlarged and it consists of several identical pickup loops, which are connected in parallel to reduce the inductance. The 16 loops are arranged to the cart-wheel like shape of the device. A multilayer technology is needed for the preparation. </li></ul>ECK -- electrocardiogram
ECK -- electrocardiogram transform the applied flux into a room temperature voltage output senses changes in the external magnetic field and transforms them into an electrical current transforms the resulting current into a magnetic flux in the SQUID sensor acquiring, storing analyzing data
ECK -- electrocardiogram SQUID maps the axial (B Z ) component
Magnetocardiography (MCG) <ul><li>Magnetic field: x , y, z component </li></ul><ul><li>Grid measurement </li></ul><ul><li>Similar sensitivity to EKG </li></ul><ul><li>Higher SNR than EKG </li></ul>
magnode Solenoid coil I r = reciprocal current Φ LM = reciprocal magnetic scalar potential field H LM = reciprocal magnetic field B LM = reciprocal magnetic induction field E LM = reciprocal electric field J LM = lead field V LM = voltage in the lead due to the volume source i in the volume conductor Magnetocardiography (MCG)
The general construction of the measurement system Measurement of the x -component of the magnetic heart vector Measurement of the y -component of the magnetic heart vector Measurement of the z -component of the magnetic heart vector Baule-McFee lead system Magnetocardiography (MCG)
<ul><li>Insulating barriers such as the skull, varying layers of tissue, anatomical open spaces, do not attenuate or distort magnetic fields. The magnetic permeability of the tissue = free space. Therefore the sensitivity of the MCG is not affected by the high electric resistivity of lung tissue. </li></ul><ul><li>different sensitivity distribution with EKG </li></ul><ul><li>the magnetic detector is not in contact with the subject </li></ul><ul><li>SQUID magnetometer is readily capable of measuring DC signals. Such signals can be obtained electrically only with great difficulty. </li></ul>Magnetocardiography (MCG)
<ul><li>ECG is easier to use </li></ul><ul><li>Technologically more complicated, requires complex and expensive equipment: SQUID magnetometer, liquid helium, and a low-noise environment </li></ul><ul><li>Because of the development of the SQUID technology, a shielded room is no longer needed in magnetocardiography. </li></ul><ul><li>Future: at the liquid nitrogen temperature which decreases the operational costs </li></ul>Magnetocardiography (MCG)