SYSTEMS FOR INDICATING THE VARIATION IN RADIOACTIVITY WITHIN A PATIENT'S CARDIAC CYCLE FROM A TRACER SUBSTANCE IN THE BLOOD

摘要

1527590 Cardiac measurement by radioactivity OHIO-NUCLEAR Inc 24 Feb 1976 [6 Nov 1975] 07250/76 Heading G1A A system for indicating the variation of radioactivity within a patient's cardiac cycle has timing means 28 for determining a plurality of corresponding sampling intervals in each of a plurality of cardiac cycles, means 26 for counting the number of radiations from a selected heart blood pool location in each interval and an indicator of the cumulative amount of radiation counted in the corresponding sample intervals of the plurality of cardiac cycles. Analyser 20 produces digital output pulses for gamma rays (i.e. when its input voltages are in a certain range). These are counted by counter 26, cleared at the beginning of each interval by generator 28. Input channel counter 36 is reset by the ECG signal from detector 10 and clocked by generator 28. During each sampling interval memory 34 stores cumulative data and its corresponding memory channel is switched by counter 36. This data is automatically added by adder 32 to the count already stored after which control of the memory address is switched from counter 36 to the video display system, so that time base generator 42 controls the read-out of memory 34. Each channel's contents appear at the output simultaneously with each line SYNC pulse. The output of comparator 48 causes a bar to be drawn on the corresponding line of the raster of CRT 40 of length proportional to the number stored in the corresponding channel of memory 34. CRT 40 is orientated so that this length is vertical. For a single pass mode of operation, opening mode switch 38 prevents the initiation of counter 36 by the patients R-wave and it is only reset by the action of a switch, and is automatically terminated after counting a certain number of channels. Generator 52 generates a digital graticule signal gated by ECLUSIVE OR gate 54 to CRT 40 such that the grid pattern is not obscured by the data image. Rate control 28a varies the sampling intervals over a 4:1 range. Counter 36 can be adjusted to switch in ¢ or “ of the number of memory channels. Channel number selector 56 can be used to multiply the sampling interval by 2 or 4 and to correct comparator 48 to interrogate each memory channel for 2 or 4 lines to lower the resolution of the display.