Patent GB-1422773-A (GB)
Title: Apparatus for detecting a fluid flow
IPC: G01S15/58
Filed: 1971-11-11
Abstract: 1422773 Measuring fluid flow rate SOCIAL SERVICES SECRETARY OF STATE FOR 7 Feb 1973 [11 Nov 1971] 52386/71 Heading H4D An apparatus for detecting fluid flow in a body comprises a generator and receiver for transmitting and receiving ultrasonic pulses into and from the fluid, a detector producing an output in accordance with any frequency difference in the transmitted and received signals, a delay for varying the time between transmitting' a pulse and actuating the detector, a support for the generator and receiver providing signals representing the position and orientation thereof and a display responsive to the detector and support providing a visual display of the fluid flow and its position in said body. Fig. 3 shows a device for investigating blood flow in the human body. Oscillator 10 supplies 5 MHz signals to gate 13 which opens under the control of generator 12 driven by oscillator 10 via divider 11. The 5 MHz pulses are transmitted by transducer 7 into the patient's body and reflected signals are passed by transducer 8 to pre-amplifier 15. Switch 17 also driven by divider 11 supplies 5 MHz signals sequentially to sixty four range channels each having a Doppler shift detector 16(1)- 16(64). The detectors also receive the preamplifier 15 output and give signals proportional to the Doppler frequency shift at their outputs. The signal may alternatively be passed through a level detector which gives a fixed output if the shift is above a predetermined level. The detector outputs are multiplexed and passed to the intensity modulation channel of a storage CRT 24. The deflection voltages for the CRT are derived from a pantograph 26 connected to the transducer support 9 and from the range of the reflectors determined by the range channels. The display thus indicates only moving reflectors-above a predetermined velocity (if the level detector is used) or whose velocity is indicated by the intensity of the CRT display. Various modifications are described, in Fig. 6 (not shown) there are provided Doppler detectors which determine the direction of the fluid flow using quadrature detection channels. In the Figs. 8, 9 (not shown) embodiments, the multiplexer output is converted to digital form and the position and velocity information is fed to a computer which provides display outputs such as cross-sections or velocity profiles. In the embodiments described in Figs. 10-13 (not shown, the CRT displays non-stored information on a stored background. A bright line indicates the position of the first twenty channels along the beam. By aligning the centre of the bright line with the centre of a blood vessel the volume flow rate can be determined by operating a mode switch. This causes the twenty channel outputs to be fed simultaneously to a weighted adder (Figs. 10, 11) or sequentially to a computer (Figs. 12-13). The flow rate is then indicated on either an analogue or digital meter. In all the embodiments the storage CRT may be replaced by a normal CRT and camera, whilst if using the computer version, only the normal CRT is necessary. The CRT may be a colour one in which case, fixed targets, moving reflectors and different flow directions may all be shown in different colours.