Patent GB-1160101-A (GB)
Title: Improvements in or relating to Ultrasonic Encephalographic Systems
IPC: A61B8/08
Filed: 1966-08-02
Abstract: 1,160,101. Ultrasonic encephalograph; cathode ray tube circuits; gating circuits. MAGNAFLUX CORP. 2 Aug., 1966 [2 Aug., 1965], No. 34628/66. Headings H3P, H3T, H4D and H4T. In an encephalographic system for determining physical characteristics of a skeletal head, ultrasonic pulses are transmitted into at least one of two separate surface portions of the head, reply pulses are received at both surface portions, and the travel times of the received pulses are compared. In the Fig. 1 embodiment for sensing displacement of the brain midline, " left " and " right " transducers 11, 12, coupled to head 13 are connected to pulsing circuits 43, 44 and receiver gate circuits 37, 38 which can be operated selectively to give three inspection modes, viz. a " left " mode (L) in which transducer 11 only is used to obtain echo pulses from midline 14, a similar " right " mode (R) using transducer 12 only, and a " through-transmission " mode (TT) in which pulses transmitted from transducer 11 are received by transducer 12. The pulse travel times in the three modes are compared on oscilloscope 18, the traces 19, 21, 23 for the three modes being vertically separated on the oscilloscope screen. According to the position of ganged switches 251, 252, 253 the system is locked to either (a) the L mode, (b) the R mode, (c) the TT mode, (d) an automatic mode in which the L, R and TT modes repeat cyclically under the control of voltages on output lines 61-66 of a shift register 54 clocked by pulses from horizontal sweep circuit 50, or (e) a mode in which the L, R or TT mode is selected according to the degree of depression of foot-switch 26. Pulse circuits (Fig. 4).-For pulsing the " left " transducer, negative-going voltages from the shift register 54 and gate 47 of Fig. 1 are differentiated by networks 241-244 and 247. 250 and applied via diode OR gate 237, 238, 245 to pentode pulse-amplifier 230 which feeds subsequent stages driving the transducer. The OR gate input via diode 245 is enabled only if control line 249 is negative with respect to ground. A two-input OR gate and pulseamplifier 46, 44 similarly pulse the right " transducer. Gating circuits (Fig. 4).-During the L mode' echo pulses from the " left " transducer pass to receiver amplifier input line 35 via preamplifier 39 and gate 37. Preamplifier 39 comprises triode stage 212 and emitter follower stage 208. Gate 37 comprises emitter-follower stage 202 which is switched on when shunt transistor 207 is made non-conducting by a gating signal on line 62. During the R and TT modes echo pulses from the " right " transducer pass to line 35 via preamplifier 40 and gate 38 (similar to gate 37 but including transistor OR gate 224 for switching on stage 220 when gated by a signal on line 63 or 65). Cathode ray tube circuits (Fig. 3).-The echo pulses are applied via stage 162 to parallel emitter-follower stages 150, 176, 189 where they are superimposed on three different D.C. voltages preset by potentiometers 164, 177, 196 respectively. The stages 150, 176, 189 are enabled one at a time during the R, L and TT modes respectively, when gating signals on lines 61-66 render the associated shunt stages 155, 156, 179, 180, 198 non-conducting. The superimposition signals are taken from circuit points 147, 148 and applied to push-pull pentode amplifiers 127, 128 driving the two vertical deflection plates of the oscilloscope. Time marker signals are fed via stage 169 to stages 150, 176, 189 and mixed with the echo pulses. Stage 139 provides voltage control for the screen grids of pentodes 127, 128.