GB1398022A - Transcutaneous sonic monitoring apparatus - Google Patents

Abstract

1398022 Ultrasonic diagnostic devices AMERICAN OPTICAL CORP 12 Oct 1972 [27 Oct 1971] 47104/72 Headings H4D and H4J Ultrasonic apparatus for determining, e.g. heart rate or blood flow characteristics, by transcutaneous Doppler monitoring of a vessel, includes a piezoelectric transducer comprising an array of coplanar transmitting and receiving elements which give the transducer a broad directivity pattern so that the apparatus is substantially insensitive to the position of the transducer with respect to the monitored vessel. Continuous wave ultrasonic energy is used in a reflection mode. In the embodiments described, Doppler frequency signals extracted from the reflection signal are presented audibly, or applied to a frequency-to-D.C. converter, a spectrum analyser or a digital computer for analysis. Transducer details.-In Fig.2, the transmitting and receiving elements alternate and comprise inter-digitated electrodes 21-25 on a lead zirconate titanate substrate. For operation at 10 MHz the substrate is 8 mils. thick. The electrodes (e.g. each <SP>1</SP>/ 16 by # inch) are typically 1 micron thick, spaced by 20 mil. gaps. They and their interconnections are formed by deposition of a gold layer on top of a chromiumcontaining bonding layer. Cross-talk between the elements is reduced by undercutting the substrate in the gaps.