JPS6052387B2 - nuclear stethoscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates generally to the field of nuclear medicine and, more particularly, to the field of nuclear medicine, which relies on the detection of radioactivity from radioisotopes injected into the bloodstream to detect radioactivity that passes through the heart. It relates to diagnostic technology that analyzes blood flow.

[Conventional technology]

In addition to standard instruments for cardiac diagnosis, such as the electrocardiogram (ECG) and a traditional stethoscope for listening to heart sounds, relatively new technologies include angiography, ultrasound cardiography, and measurement of radioactivity in the blood. are being studied and implemented to increase the amount of quantitative data and provide a more reliable basis for diagnosis.

When determining the performance of the heart, it is desirable to measure the volumetric flow rate of blood through the heart. For example, the difference in left ventricular volumes during different stages of the cardiac cycle represents blood flow. Volume measurements can be approximated using X-ray or ultrasound imaging techniques.

Another type of x-ray technology is described in U.S. Patent No. 38 to BjOrk et al.
No. 2439, which indicates the concentration of a radiopaque tracer in the heart over several cardiac cycles to produce quantitative data on blood flow. The same model relies on injecting a radioisotope into the bloodstream entering the heart and using a scintillation detector or Geiger counter to measure changes in the concentration of the radioactive tracer in the cardiac outflow tract over several cardiac cycles. technology was used in the early days. The data collected was plotted and utilized to determine blood flow through the heart. For example, Vig
U.S. Patent Nos. 3,221,731 and 3 of Mr. Ou] Et et al.
See No. 528407. Problems to be Solved by the Invention Known systems for analyzing blood flow using detection of radioactive isotope concentrations are deficient in providing data quickly to the physician in an easy-to-understand format.

A general object of the present invention is to create an easy to understand representation of the radiation (and thus gamma radiation) emitted from the cardiac blood pool at precise time intervals of the cardiac cycle, and to provide data for multiple cardiac cycles over time. It is to be accumulated over a heartbeat and displayed in one composite image showing the accumulated radioactivity at time intervals within the cardiac cycle.

[Means and actions for solving the problem] To achieve the above object, in the present invention, a collimated probe directed at a selected position of the heart detects the concentration of radioactive isotopes in the blood. Output pulses are generated which are counted during each short time interval repetition and stored in a multi-channel memory.

The first channel of memory is gated upon detection of the patient's ECG (7) QRS complex. The channels of memory are then addressed one after another such that each successive radiation count in each repetition of the time interval is stored in a corresponding memory channel. With subsequent heartbeats, this process repeats, and new counts are added to the counts already stored in the particular channel.
At the same time, the memory channels are read out to a TV type display where each memory channel is correlated in a 66 horizontal '1' scan line sweep.

At the beginning of each scan line, the video input signal is switched from a low level to a high level, where it remains in the memory channel for a time corresponding to the accumulated total, thus increasing the time depending on the accumulated radioactive count. T the line where the height is determined.
Write on the screen. As successive scan lines of the display correspond to different time intervals of the cardiac cycle, the clinician can view images showing changes in radioisotope concentrations in selected portions of the cardiac blood pool during the patient's cardiac cycle. Establishment can be observed for about 1 minute.

Instead of being synchronized to the ECG, the device can also be configured to operate in ``dynamic mode,'' in which case the memory input is activated for a longer period of time (e.g., 100 milliseconds) before switching to the next channel. A non-repetitive (single pass) test is performed by accumulating radioactivity counts in each channel. It is constructed so that the time-radioactivity curve of the retained radioactive isotope can be immediately visualized.

The device has two modes of operation, referred to as ``Synchronized mode'' and ``Dynamic mode.'' The program diagram in Figure 2 shows all the functional elements of the electronic system for operation in each mode. The term synchronous mode means that the storage of information is based on the R wave (Q
It is used so that it is synchronized with the central peak of the RS group.

The storage time of each memory channel, described below, is short enough to allow sampling at a desired number of time intervals during each cardiac cycle. The disadvantage of synchronization is illustrated by the fact that a counter that increments the channel designator or address for incoming data is reset on each R wave to cycle through the memory channels.The synchronization mode is switched off. It can continue indefinitely until the memory is filled with new data, but it is effectively terminated (there is no point in displaying it) when all channels are completely filled so that the memory is no longer filled with new data. In contrast, dynamic mode involves only a single pass across all memory channels, and each channel is "open" for a significantly longer period of time than in synchronous mode.

After the radioactivity has been counted in the last time interval (last channel), the dynamic mode is automatically terminated. The following detailed description begins with the operation of the apparatus in synchronous mode, and concludes with a discussion of certain control aspects, such as how dynamics and synchronous mode are selected and initiated.

In FIG. 2, the patient's ECG signal is amplified with an ECG isolation amplifier 10 and filtered to remove breathing, muscle contraction and other noise, and Q.
The RS group includes a conventional 0RS detector 12 having a front panel indicator light 12a (FIG. 1) for providing a reset signal to the memory channel switch device described below.
It is distinguished depending on.

Adjustable high voltage DC power supply 16 (typically 300 DC
Collimating probe 14 is energized by a NaI crystal (typically 3.5 to 1000 volts) in diameter.
8c1n (1.5 inches)), a photomultiplier tube, and a shielded deep-focus collimator with two apertures that produce an earthpick or pinhole field of view. Gamma rays from the focal point of the probe 14 being positioned produce a current pulse from the probe 14 that passes through a nuclear pulse amplifier 18 to a single channel analyzer 20. The term ``single channel'' indicates that only one type of radiation is being detected. Note that this is not related to the term multichannel memory, which is used to refer to multiple memory channels corresponding to adjacent intervals of a cardiac cycle.Variable Range Rate Meter Circuit 22 converts the pulse repetition rate from analyzer 20 into a voltage that is used to adjust power supply 16 with knob 16a (FIG. 1) to accept a particular isotope. count rate meter 2 to indicate whether the gain of the photomultiplier tube should be controlled by
Drive 4.

Front panel switch 22a. (FIG. 1) changes the range of count rate meter 22 by a factor of 100, 1000, or 10000. The digital pulse output of the analyzer 20 is simultaneously passed to a counter 26, which counts one "nuclei event" each time a pulse is received from the output of the analyzer 20 at adjacent times within one cardiac cycle width. To count the number of events in an interval, a nuclear event counter is set to zero at the beginning of each time interval by an adjustable time-per-channel time base generator 28.

In the preferred embodiment, three options for memory channels are available: 192, 96, or 48, described below. The time base generator 28 cooperates with a frequency divider 29 (optionally including a multiplier) and is selected to provide a coverage of the entire heart cycle at an approximate heart rate of ω beats/minute. Nominally 5.12 ms, 10.24 ms or 20.
It emits a clock pulse every 48 milliseconds. This nominal setting accommodates the patient's heart rate.
i.e., by using the front panel max/min ratio control knob 28 to ensure that all 192 channels are used.
can be varied over a 4:1 range around this nominal setting via a. The output of the nuclear event counter 26 is passed to a multi-channel accumulation memory unit 30, which includes a two-input digital adder 3.
2 and non-destructive read addressable read/write memory 3
The memory 34 has 192 channels with 12 bits of storage per channel.

The type of memory selected should be one that allows data to be written to and read from simultaneously, such as a core storage matrix. The nuclear event counter 26 is the adder 3
Give one (A) of the inputs to 2. The other input B is provided by the data output of memory 34. The output of adder 82 forms the data input to memory 34. 0RS detector 1 via mode switch 38.
2 and clocked (incremented or decremented) by the time base generator 28. Each count time (e.g. 5.12 ms)
During the process, memory 34 stores new accumulated memory data in the corresponding channel. During the next time, input channel counter 36 re-addresses memory 34 to its corresponding memory channel. The memory 34 is therefore operated in cumulative fashion by combining the count at a particular time with the count already stored in the corresponding channel of memory during all corresponding times since entering the synchronous mode. . For storage (input) operations, the address of the memory data output provided to digital adder 32 is controlled by input channel counter 36 in the same manner as the input address is controlled.

In operation, the memory is addressed once per time interval, very briefly, by sending it to the incoming channel counter 36.

For example, at the end of a predetermined time interval, memory address control is switched from the video section (described below) to the input channel counter 36 to hold the corresponding memory channel open for a short time, and during this time the adder 32 is clocked just before the reset pulse from the time-per-channel time base generator 28 to enable the adder to add the previous number of memory channels in the output register and the count during the current time interval. , and passes the added count back to the same memory channel. After this update operation is completed, control of the memory address is switched back to the video display system. The video section of the device serves to display the updated contents of the memory channels all at once. The memory channels are visually represented by the display in the form of adjoining parallel lines, and the numerical value of each channel is represented by the length of the bar drawn on the scan line, similar to the configuration of a bar graph. Since the channels represent adjacent time intervals, the display can be represented by an X-Y display, where the X-axis represents time and the Y-axis represents radioactivity. The total length of the x-axis corresponds to one cardiac cycle and the data displayed represents the variation in radioactivity within a cardiac cycle. Because the image is established over a large number of cardiac cycles, the displayed data tends to represent radioactivity variations within a representative or average cardiac cycle. The heart of the video section of the device consists of a conventional cathode ray tube (CR), shown schematically in the front screen view of FIG. 1 and in FIG.
T) Display device 40.

The video display time base generator 42 generates approximately S timed synchronization pulses to produce a general raster scan pattern of the electron beam on the display 40 even though the horizontal and vertical deflection control signals are generated. TV sweep circuit 44
give to The raster pattern is oriented at right angles to a typical TV raster scan. That is, the scanning lines run vertically. This is accomplished by rotating the TV monitor 90 degrees. The number of scan lines in the raster pattern can be determined in an approximately 1:1 relationship with the maximum number of desired memory channels. However, there is no reason why a standard configuration ``synchronization signal configuration'' in which 25 scan lines are created cannot be used. If the number of scan lines is significantly greater than the number of channels used, one channel must be represented by a large number of adjacent scan lines to maintain adequate image size. In addition to controlling the generation of the rask pattern on the display 40, the video time base generator 42 generates multiple channels at any time except at the time of the end of one count time interval when the memory is updated with new accumulated data. It also controls the read function of memory 34.

Address control multiplexing is accomplished by a high speed electronic switch 46 operated by a time-per-channel time base generator 28. Addressing is controlled by incoming channel counter 36 only at certain times during each counting time interval. This small time interval,
That is, during the "update time," the corresponding memory channel is interrogated non-destructively with the count of the nuclear event counter 26, and the two data are added together and returned to the corresponding memory channel. The data input to adder 32, ie memory 34, is disabled.Following the update time, control of the address of the memory output is returned to video time base generator 42 by switch 46.The update time is stored. video time base generator 42.
increases or decreases the output channel address of memory 34 at the same rate as the scan line sync signal so that the contents of each channel appear at the output at the same time as each sync pulse that starts the scan line sweep deflection signal.

The output register of memory 34 is connected to one input of comparator 48. The other input is the video time base generator 4
2 are interconnected. The output of comparator 48 produces a data video signal that causes a line to be drawn on the corresponding scan line of the display device with a length proportional to the number stored in the corresponding memory channel. Comparator 48 can be implemented with digital or analog circuitry (not shown).

Digital implementations require high speed clocks, which are commonly available in time-based formats, from which video time-base synchronization signals are generated. This high speed clock operates a counter that is triggered and enabled by the scan line sync pulse. A standard digital comparator circuit receives in parallel the output of the memory channel and the successively incremented output of a counter operated by a high speed clock. When the count reaches the same number of input registers in memory 34,
A digital adder switches from one binary level to another. Precisely the same comparison operation can be performed in analog mode by using a ramp signal generator triggered by the scan line synchronization pulse.

The output of this gradient signal generator forms one input to a differential amplifier or comparator circuit, and the other input is the output of a digital-to-analog converter connected to a memory output register. Both digital and analog implementations of comparator 48 are considered quite conventional for the functions described above. The digital output of comparator 48 is therefore synchronized with display device 40.

The data level of the video output (ie, completely white) is on from the beginning of the scan line until the point at which comparator 48 finds a match between the contents of the memory channel and the reference slope or count. The largest significant number that can be included in a given channel is considered to be the number in which all 12 bits are represented by "1", which in w-adic form is equal to 4095. The proportion of the digital reference counts used and the slope of the analog slope should be adjusted so that the total count (4095) does not exceed the total width of the screen.However, in a given test, memory Since only one portion of the capacity is used, it is necessary to shift the count up. This is accomplished by the count per line controller 50 of FIG. It is operated by a calibrated "count full scale" knob 50a on the front panel of FIG. One way in which this higher order movement of data can be accomplished is by taking the binary number in the output register of memory 34 and
Then, before entering this number into comparator 48, this number is shifted by one or more digits above 6° (similar to shifting the decimal point). This type of operation is based on the count full scale knob 50a shown in FIG.
It is suggested by a power-of-power calibration. A preferred feature of this device is a self-generating grid that allows quantitative measurements of radioactivity fluctuations to be made independent of non-linear distortions.

For this purpose, the gradient signal generator 52 is operated by the same video time base generator 42 that operates the T-sweep circuit. The gradient signal generator simply consists of a clocked logic circuit that writes equally spaced white dots along each scanline sweep to create a vertical line and Create a horizontal line of the grid pattern by drawing a complete white line for each line. The video output of the gradient signal generator 52 is passed along with the output of the comparator 48 to an exclusive-OR gate 54;
is normally open even if either one of the video outputs is white. However, this exclusive-OR gate is prohibited when both video outputs are white. The result of this logical operation is to make the lines of the grid appear as black lines, which always radiate visibly as either white lines against a black background or black lines against a white background. In normal operation, the number of channels corresponds on a 1:1 basis to the number of scan lines utilized to visualize the display.

However, the number of channels may be selectively reduced if desired. In the preferred embodiment, a channel number selector 56 operated by a three-position switch 56a on the front panel of FIG. 1 selects the number of channels from two to four.
It can be used to divide by 96 channels or 48 channels respectively. No radioactivity is missed or uncounted when the number of channels is divided into two, but the resolution of the instrument is reduced. For example, if 9 channels are selected instead of all 192 channels, the channel number selector 56 is set to 5 of the memory channels.
Simply remove 0%. One way this can be achieved is such that the preset number for all channels is 192 (in W-adic form) and the number for half channels is preset to only 96.
A presettable count counter for the incoming channel counter 36 is used. In either case, when the power count of a channel is lowered to zero, the counter 36 is activated until commanded by the next R wave to start counting down again from the preset number.
stops. At the same time, the channel number selector 56 can be used via the frequency divider 29 to double and quadruple the time interval clocked by the time base generator 28 in hours per channel. At the same time, the channel number selector 56 also operates a comparator 48 which generates a video signal.
must be corrected. Thus, each memory channel is interrogated for two or four scan lines such that two or four adjacent parallel bars of equal length are written. Another way to make a video display a complete screen even when the number of channels is divided by two or four is to connect the memory channels in tandem or groups of four based on the setting of the channel number selector 56. It is.

For a first address, say 96, the same data is put into two adjacent channels, typically corresponding to channels 192 and 191, for example. In this way, the video display device can read out channels at the same rate as if the entire channel capacity of the memory were being used. Other functions provided on the front panel of the device are "Sync", "Dynamic" and "Erase".

Erase controller 58 (FIG. 2) operates in a conventional manner to clear the entire memory upon a command to set all 304 bits to zero. Synchronous/dynamic mode control unit 6 operated by front panel synchronized and dynamic pushbuttons 60a and 60b.
0 has many functions.

If synchronization mode is desired, pressing a synchronization button (eg, a bistable electromechanical switch) will initiate the storage operation depending on the next R-wave from the patient. Thus, the mode controller 60 can be implemented with a gated flip-flop whose data input is represented by the position of the synchronization switch, and the output of the QRS detector 12 is determined by the memory receiving the data. This is the clock pulse that sets the output of the flip-flop so that Therefore, once the synchronous switch is set, it will continue to operate in synchronous mode indefinitely until the memory capacity is exhausted or the synchronous switch is repositioned again. When this occurs, the synchronous mode ends with the next R wave. The display device, if permitted,
It continues to be established until the entire screen is white. If a dynamic (single stroke) mode of operation is desired, patient R waves are not an issue.

Therefore, activation of dynamic switch 60b opens the connection between ORS detector 12 and the reset (or preset) input of channel counter 36 via mode switch 38. Instead of being initiated by the patient's R-wave, the channel counter 36 is reset by actuation of a dynamic switch. Furthermore, selection of the dynamic mode of operation momentarily enables the memory 34 and, via the frequency divider 29 (or its equivalent), to divide the count time interval timed by the time base generator 28 into 5.12 Instead of milliseconds, change it to a very long time interval of about 100 milliseconds. 192 100 millisecond time intervals result in a 19.28 hour interrogation, which is automatically terminated by channel counter 36 not being reset after it has counted 192 channels.

In use, the portable device is brought to the bedside and the patient typically injects a protein containing a radioactive isotope, e.g. up to 30 milliliters of technetium-99n1, directly into the bloodstream entering the heart. Preparation is made by making a connection to the ECG device.

Approximately 1 minute after injecting the tracer, the doctor injected probe 14 (
2) is held in front of the patient's heart and the count rate meter is observed to locate the focus on the blood pool of the heart (eg, left ventricle). Once the probe is in position, the synchronization button is activated and the image is viewed for approximately 1 minute until a measurable curve is obtained. During image establishment, if the clinician feels it is appropriate to change the number of channels, the device is taken out of synchronization mode and the memory is cleared.
Adjustments are made and synchronization mode is started again.

The synchronization mode can also be shut off and restarted without erasure if desired. The above detailed description is not intended to limit the invention to any specific form in which there are equivalent means for performing the functions described in detail.

For example, the collimated probe 14 and the nuclear pulse intensifier 13 represent only one way to detect and interpret radioactivity from a particular point in the heart's blood pool; Any available technology may be substituted. In addition, other X-
Y display technology can also be substituted. It should be noted that the description herein is merely illustrative of the preferred embodiment of the invention, which is constructed to meet certain standards and specifications that depend in part on the particular application and conditions in which the apparatus is used. do not have.
It is therefore intended that all modifications that come within the scope of the equivalents of the present invention be included within the scope of the claims. [Effects of the Invention] As is clear from the above explanation, according to the nuclear stethoscope according to the present invention, radiation data emitted from the blood pool flowing in the patient's heart is accumulated over a large number of heartbeats. A single composite image showing the integrated radioactivity at each time interval within the cardiac cycle can be instantly visualized, making it useful for diagnostics regarding blood flow through the patient's heart.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of an apparatus including a display screen and control panel schematically representing a typical image produced in accordance with the present invention, and FIG. 1 is a block diagram showing the electronic equipment associated with the device;

10I-1...ECG isolation amplifier, 12.
...0RS detector, 14...Collimated probe, 20...Single channel analyzer, 22...
... Route meter circuit, 24... Count rate meter, 26... Nuclear event counter, 28.
. . . time base generator of time per channel, 30 . . . multichannel cumulative memory unit;
32... Input digital adder, 34...
addressable read/write memory, 36... input channel counter, 38... mode switch, 40... display device, 42... video display device; Time base generator, 48... Comparator, 54
. . . Exclusive OR gate, 60 . . . Synchronous/dynamic mode control unit.

Claims (1)

[Scope of Claims] 1. In an apparatus for displaying fluctuations in radioactivity during a cardiac cycle of a patient from tracer substances in the blood, the radiation emitted from a selected location in a blood pool of the heart. detector means 14, 18, 20 for producing an output representative of a quantity;
timing means 28, 29 for determining a next sampling time interval, responsive to the outputs of said timing means and said detector means for producing an output representing the amount of said radiation detected in each successive sampling time interval; Nuclear event integration means 26, 30 to store the total amount of radiation in the n-th (n is a natural number less than or equal to N) sampling time interval indicated by the integration means into N (N is a natural number) memories. addressable N-channel accumulation memory means 34 for accumulating into a corresponding one of the channels, heartbeat response means 10, 12 for generating synchronization pulses at the patient's heartbeat rate, said timing means and said Responsive to the heartbeat response means, incrementing the input channel address of said memory means for each sampling time interval in a repetition of the fixed sequence of a predetermined number N of channel addresses, such that each successive sequence of channel addresses is incremented by said synchronized sequence of channel addresses; memory channel addressing means 36, as initiated by the numeric pulse, and N adjacent spaced apart memory channels each having a height above a common axis based on the current cumulative sum represented in each corresponding memory channel; display means 40, 42 for simultaneously displaying the contents of all N channels of said memory means in the format of a visible display;
, 44, 48, 50, 52, 54. 2. The display means includes means for generating the visual display in the form of N adjacent parallel lines, each having a length corresponding to the cumulative sum represented in each of the corresponding memory channels. The device according to paragraph 1. 3. The detector means includes transducer means for producing output pulses representative of radiation emitted from selected locations in the blood pool of the heart, and transducer means representative of radiation of a particular type in response to the output pulses of the transducer means analyzer means for generating a digital pulse output, said nuclear event accumulation means including nuclear event counter means for counting the number of digital pulses during each successive sampling time interval. Device. 4. The accumulation memory means includes an addressable N-channel read/write digital memory and two-input adder means, the addition means having one input connected to the read end of the memory and the nuclear event accumulation means. and the other input connected to the memory, the sum of these two inputs being provided as a data input to the memory for providing a cumulative sum of the outputs of the nuclear event accumulating means. The device described. 5. Said display means is a video display device, a series of at least N
means for generating on said display device a raster scan consisting of adjacent scan line sweeps, and corresponding to a cumulative sum of corresponding memory channels of said memory means beginning approximately at the beginning of each scan line sweep and during said scan line sweep; 2. The apparatus of claim 1, including comparator means synchronized with said raster scan for generating a digital data video signal terminating after a time interval of 0 to produce a composite data image on said video display device. 6. Apparatus as claimed in claim 5, wherein said comparator means includes means for interrogating channels of said memory means at the rate of said raster scan. 7. said display means includes means for generating a digital gradient video signal to produce a grid pattern of lines on said display device; said display means producing a video signal with reduced correspondence between said data and said video signal; 6. The apparatus of claim 5 further comprising exclusive OR means for gating said data and said tilted video signal to said display device so as not to be obscured by data images. 8. The apparatus of claim 1, further comprising means for adjusting the sampling time interval over a predetermined range to allocate N consecutive sampling time intervals to patient cardiac cycles. 9. Apparatus according to claim 1, further comprising means for selectively dividing the number of memory channels of said memory means and correspondingly extending the sampling time interval to reduce the resolution of the display device. . 10. The method of claim 1, further comprising means for decoupling said memory channel addressing means from said synchronization pulse and for sequencing said memory means once across said N channels on command. Device. 11. In a device for displaying variations in radioactivity during a patient's cardiac cycle from tracer substances in the blood, for producing an output indication of the amount of radiation emitted from a selected location in the blood pool of the heart. comprising detector means, timing means for determining a sampling time interval, and generating means for producing an output representative of the cumulative amount of radiation at each corresponding sampling time interval over a number of cardiac cycles. device to do. 12. Claim 11 further comprising means for synchronizing the sampling time interval and the patient's cardiac cycle.
Apparatus described in section. 13 further comprising means for displaying a graphical feature for each interval in response to said generating means, said graphical feature being, for a predetermined interval, a current sum of said detector means during that predetermined interval; 12. A device according to claim 11, wherein the device is indicative of a previous output.