Showing papers in "IEEE Transactions on Biomedical Engineering in 1963"

A Method of Measuring Eye Movemnent Using a Scieral Search Coil in a Magnetic Field

Abstract: With the subject exposed to an alternating magnetic field, eye position may be accurately recorded from the voltage generated in a coil of wire embedded in a scleral contact lens worn by the subject. Using two magnetic fields in quadrature phase and two coils on the lens, one may measure horizontal, vertical and torsional eye movements simultaneously. The instrument described has an accuracy and linearity of about 2 per cent of full scale, a resolution of 15 seconds of arc and a bandwidth of 1000 cyles per second.

An Experimental Determination of a Multipole Representation of a Turtle Heart

Abstract: The potentials generated by a live turtle (pseudemys) heart at the center of a spherical electrolytic tank were measured at surface points. Using a truncated multipole expansion, the dipole and quadrupole coefficients were determined from the resultant set of simultaneous equations at intervals over the QRS period. The measurement technique was checked using known artificial sources; a rough check on the truncation assumptions was made based on a known analytical model. The experimental results show that a significant quadrupole term is present. The presence of higher order poles could not be ruled out.

Subminiature Apparatus for Radio-Telemetering of EEG Data

Abstract: The use of radio-telemetering has several advantages for the recording of EEG data from unrestrained subjects. By use of transistor techniques, miniaturization of the apparatus carried by the subject is made possible. Design considerations for a transistorized high input impedance, low-noise, single-sided amplifier for the EEG frequency and dynamic range are evaluated. Common-collector configuration and an unconventional input circuit of the first stage, and careful choice of transistors and their operating points, enable one to obtain satisfactory noise performance in the actual amplifier. A differential-input amplifier, based on features utilized in the design of a single-sided type, was developed. Rejection of in-phase signals (better than 3000 to 1 at 50 cps), an input impedance of 300 kilohms, and low noise referred to the input (3?v peak-to-peak at 20 kilohms of interelectrode resistance), determine the main features for EEG amplification purposes. A VHF FM one-stage oscillator, working at 30 Mc, provides transmission of signals up to a distance of 10 m. EEG records taken from subjects free in behavior, and even during convulsions, show no artifacts.

Electronically Controlled Stage for Systematic Scanning of Microscopic Areas

Abstract: An instrument has been developed to automatically scan a microscopic area for the quantitative evaluation of the light transmitting properties of biological materials on the cellular and subcellular levels. The specimen may be viewed through an aperture of selected size in the microscope both visually and electronically, while the slide is electronically manipulated to scan a rectangular area whose length and width are independently adjustable from 5 to 100?. The slide is swept back and forth horizontally at a uniform rate which is adjustable from 0.4 to 4 ?/sec. At the end of each horizontal sweep it is moved vertically by an adjustable step of 0.2 to 10 ?. The scanning process proceeds entirely automatically until the selected area has been scanned. The stage motion is produced by thermal expansion and contraction in tungsten wires through which electronically controlled heating currents are passed. Precise control of the velocity and position of the stage is achieved by the use of feedback systems to control the heating currents in the wires so that their resistances, and therefore their temperatures, are accurately related to the values of analog control voltages. The relation between the horizontal and vertical stage displacements and the controlling voltages is linear within the precision of an occular micrometer.