Abstract: Novel intravascular, ultrasonic imaging catheters are provided which utilize thin layers of a flexible plastic material, such as PVDF, which can be spot polarized in active regions which are to serve as piezoelectric transducers. Thin layer metallic electrodes are deposited on opposing surfaces of these active regions. Strips of the appropriately configured material also having shielding and backing and/or core forming portions are spiral wound into a completed catheter. Alternatively, the catheters are fabricated from extruded PVDF tubing which may be formed around a central core which carries those electrodes which are to contact the inner surface of the extruded tube.

Abstract: Novel intravascular, ultrasonic imaging catheters are provided which utilize thin layers of a flexible plastic material, such as PVDF, which can be spot polarized in active regions which are to serve as piezoelectric transducers. Thin layer metallic electrodes are deposited on opposing surfaces of these active regions. Strips of the appropriately configured material also having shielding and backing and/or core forming portions are spiral wound into a completed catheter. Alternatively, the catheters are fabricated from extruded PVDF tubing which may be formed around a central core which carries those electrodes which are to contact the inner surface of the extruded tube.

Abstract: The present invention relates to an apparatus which determines the distribution of the attenuation slope coefficient on a real-time basis using the center frequency shift. In one embodiment, the phase difference between a received signal and a reference signal is determined using EXCLUSIVE OR gates or an inverse trigonometric relation stored in a ROM. The phase difference is input to a differentiator which outputs the center frequency shift of the received signal on a real-time basis. The center frequency shift is input to another differentiator which outputs the attenuation slope coefficient. In other embodiments, the received signal is distributed into received signal bands, having different center frequencies, and signal characteristics of the received signal bands are averaged to remove virtually all effects of spectrum scalloping in the time domain. Thus, the attenuation slope coefficient is obtained without the effects of spectrum scalloping using simple hardware and without Fourier transformation.

Abstract: A method for ultrasonic living body tissue characterization using a transducer and processor. The method includes the steps of transmitting an ultrasonic pulse into the tissue and receiving a reflected pulse, calculating the normalized power frequency spectrum of the reflected pulse, determining the frequency at which the maximum value for the power spectrum occurs, determining the high and low half power frequencies, calculating the upper and lower frequency ratios of the maximum value frequency and the half power frequencies, and determining the power exponent of the frequency of the reflection coefficient. The frequency exponent of the reflection coefficient is used to calculate the attenuation slope of the ultrasonic wave. The attenuation slope or the reflection power exponent is used to generate a tomographic image of the living tissue characteristics for visual non-invasive tissue diagnosis.

Abstract: The present invention relates to an apparatus which determines the distribution of the attenuation slope coefficient on a real time basis using the center frequency shift. The phase difference between a received signal and a reference signal is determined using EXCLUSIVE OR gates or an inverse trigonometric relation stored in a ROM. The phase difference is input to a differentiator which outputs the center frequency shift of the received signal on a real time basis. The center frequency shift is input to another differentiator which outputs the attenuation slope coefficient. Thus, the attenuation slope coefficient is determined using simple hardware and without calculating the power spectrum and the first moment.

Abstract: Continuous wave ultrasonic sound waves from a transmitter and receiver are highly focused to a width of approximately 1 millimeter or less and are transmitted and received through intersecting paths within the tissue of a patient. A doppler flow detector produces an image of the moving blood within the vessel. The transmitter and receiver are systematically scanned over the subject and the detected images are converted into visually intelligible pictures.An improved circuit for more clearly defining the flow picture of the moving blood particles utilizes a conventional directional doppler circuit plus a multiplier-differentiator-low pass filter circuit to automatically eliminate venous flow signals. A grey scale oscilloscope provides brightness intensity on the visual picture proportional to the velocity and direction of the blood flow for detecting stenosis in the vessel.A recording technique is disclosed for detecting atherosclerotic thickening of the artery wall.