DE2065980C2 - Device for recording and reproducing the two-dimensional distribution of radiation emanating from an object to be examined with a scintillation camera - Google Patents

Description

The invention relates to a device for recording and reproducing the double-menslonal distribution of a Radiation emanating from an object to be examined with a scintillation camera that uses a scintillation crystal and a plurality of photoelectron tubes with one of the photoelectron tubes at analog signals emitted with every flash of light of the Llchtblltzes in a predetermined coordinate system characterizing position signals and In a An evaluation circuit designed as an analog computer converting the intensity signal characterizing the brightness of the lightning bolt, the one pulse height analyzer which prescribes an adjustable amplitude range for the intensity signals and having a display device operated under control of the pulse height analyzer a two-dimensional image of the by the relevant position signals defined points represents only those light flashes whose intensity signals Fall into a set amplitude area.

In a known device of this type (US Pat. No. 11,057), the pulse height analyzer delivered by Signals used to the electron beam of the cathode ray tube serving as a display device light or dark to be felt, depending on whether the amplitude of the received light flash corresponding intensity signal Inside or outside the amplitude range spanned by the pulse height analyzer .lies. This serves to prevent such flashes of light from the scintillation crystal from being displayed, which were triggered by background and / or scattered radiation and thus a disruption of the actually interesting Information, namely the two-dimensional distribution of the originating from the object to be examined and represent radiation within a narrowly limited energy range.

In more recent times, however, efforts are being made to find methods of investigation apply, where in the object to be examined two or more different it contains radioactive substances that are under release decay of radiation of different energies and their distribution in the object to be examined individually, d. H. unaffected by the other radioactive substances to be examined. this can only be done with the help of the known device that the amplitude range of the pulse analyzer initially suitable for the first of these radioactive substances is adjusted, so that only their distribution is reproduced in the display device. According to this, the amplitude range must then be based on the energy of second radioactive substance must be set so that it can be reproduced. This is an extraordinarily cumbersome process, which it in particular does not allow a direct comparison between the instantaneous distributions of the various carry out radioactive substances, which is particularly detrimental when one or several of these substances have a very short half-life, so that their decay frequency By measuring the distribution of another substance, it already changes noticeably.

The invention is based on the object of a device of the type mentioned at the outset so that they can display the distributions at the same time of radioactive substances with different radiation energies.

This object is achieved according to the invention in that in the evaluation circuit a second on one of the amplitude range of the first pulse height analyzer Different amplitude ranges adjustable pulse height analyzer provided for the intensity signals 1st and that the reproducing device by the output from the second pulse height analyzer Signals for the simultaneous generation of a second, spatially separable image is controllable, which reproduces the two-dimensional distribution of the light flashes assigned to the second amplitude range. By designing the device in this way, it is achieved that the origin of the radiation is more different Energy through different brightness or intensity revealing scintillatlons in two for Representation of incoming groups can be divided, one of which is representative of the distribution a first radioactive substance with a defined radiation energy and the second representative of the other is radioactive substance with also defined radiation energy.

This means that the two-dimensional distributions of various radioactive substances can be recorded at the same time and reproduced, which enables a direct comparison of identical points in time or Measurement results obtained in identical tent rooms are permitted.

The invention is explained below on the basis of an exemplary embodiment explained in more detail with reference to the drawing; In this show:

F1 g. 1 and 2 are a block diagram of a device according to the invention trained facility.

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Signals from photoelectron tubes of a detector head 16 are in preamplifiers of a preamplifier arrangement 20 and then attenuated in an attenuator assembly 22. The main purpose of the latter Is the calibration of the various photoelectron tubes that are in their amplification? differentiate can.

The attenuator arrangement 22 transmits the signals to a decoder arrangement 24 with six decoder matrixes 24a to 24 / supplied. The output signals of the decoding pins 24c to 24e are fed to two analog computers 26/1 and 265 connected in parallel as input signals.

The decoding matrix 24 / contains a selector switch (not shown) which enables the output of any popular photoelectron tube of the detector head 16 via a test switch 28 and via a line 30 a data processing unit 15 can be performed for calibration.

Since the two analog computers 26A and 2CB are identical in structure, only the analog computer 26A will be described in detail. The signals originating from the decoding matrices 24a to 24e are fed to the analog computers 26/1 and 265 via five amplifiers 32a to 32e with variable gain. The gain factors of these five amplifiers are remotely controlled to allow recording of scintillations with different energy ranges.

The output signals of the amplifiers 32a to 32e are fed to pulse stretchers 34a to 34e, respectively. The output of the amplifier 32a is fed as an input to a pulse height analyzer 36/1. In addition to such a pulse height analyzer 36A or 365, each of the analog computers 26/1 and 265 also contains a ratio detector circuit 38.

A signal is present on a line 406 which exactly reproduces the + J position of a scintillator occurring in the scintillator, a signal is present on a line 40c which reproduces precisely the -J coordinates of such a signal, and a similar signal is present on a line 40rf , which reproduces the +7 coordinates, and a similar signal on a line 40e which represents the -7 coordinates. Similar signals are emitted on the lines from the analog computer 265 of channel 5. Gate control means (not shown) ensure that signals are not picked up from both channels A and B simultaneously. For example, if signals from channel A are picked up, channel B is switched off. There is only one channel in the controller at a time.

A clock circuit 42 receives signals via a line 44 from the ratio detector circuits 38 of both the channel Λ and the channel S analog computers 26/4 and 265, and via a line 46 signals from the two pulse height analyzers 3 (> A and 365 of these Furthermore, the clock circuit 42 receives input pulses via a line 48 from a gate 50 and via a line 52 from a monostable multivibrator 86. The clock circuit 42 also sends a signal directly to this multivibrator 86 when so-called "fast analog" operation is present. The clock circuit 42 waits for the signal from line 52 indicating the end of a cycle and then provides a reset signal to each of the pulse height analyzers 36/1 and 365. It also provides a clear signal for gate 50 on line 54. The clock circuit 42 also provides turn-on signals to an analog-to-digital converter circuit on line 56.

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60 The four output signals from the pulse stretchers 346 to 34e are fed to two differential amplifiers 58Jbzw. 587 supplied. The + J and - J signals on lines 406 and 40c are fed to differential amplifier 58.Y, and the + Y and - / signals on lines 40rf and 40e are fed to differential amplifier 587. Each of the differential amplifiers 58 J and 58 Y combines its respective input signals and provides individual output signals which each represent X and / position coordinates. The J-coordinate at the output of the differential amplifier 58J is an amplitude lengths converter 6OJ, the differential amplifier 587 is supplied with the y-Koordlnaten-Informatlon an amplitude lengths converter 60 Y.

The X and y coordinate information is also fed to a rotor 94 in each case.

The amplitude lengths converter 60J, and 60 Y generate gating pulses constant, predetermined amplitudes, whose length is proportional to the amplitudes of input signals to the transducers. The output signals of the converter 60J, the duration of which is proportional to the amplitudes of the input signals from the differential inverter 58J, are fed to a gate 62J. Similarly, the output of converter 60 Y is fed to a gate 62K. Second inputs to the gates 62A 'and 627 come from an oscillator 64. The oscillator 64 is operated by gating signals from the amplitude-length converters 6OJ, 60 Y and provides a pulse train in which the number of pulses is determined by the longest output pulse from one the converter 6OJ, 6OK is controlled.

At the end of the signal from the transducer 6OJ, the gate 62J is blocked, even if the output pulse from the transducer 6OK has not yet ended. When the longer of the pulses from the transducers 6OJ, 6OK ends, the oscillator is turned off 64 and both gates 62J and 62 Y locked. The result is that a train of output pulses is supplied from the gate 62J, the number of pulses of which is proportional to the height of the output pulse from the differential amplifier 58J, and a train of pulses from the gate 627, the number of which is proportional to the height of the output pulse from the differential amplifier 58K.

The outputs of gates 62J. 62y are supplied to counters 66J, 667, respectively. These counters are used to store the number of pulses proportional to the amplitude of the J and y output signals of the differential amplifier 58J, 58y are. The counter 66y includes one Marker section 66F, the marker signals from the pulse height analyzers 36/4, 365 of the two Analog computer 26/1, 265 picks up and stores, which indicate from which of the two channels the stored Signals are recorded.

The digital signals stored in the J counter 66J, the Y counter 667 and the marking section 66F can be transferred to a shift register 70 via a gate 68. Gate 68 is opened in response to a signal from gate 50.

Gate 50 provides this signal to open gate 68 when there is coincidence between that of the Clock circuit 42 on line 54 received the clear signal and on line 73 of a ring counter 72 recorded signal occurs.

The ring counter 72 is connected to the oscillator 64 by means of a line 74 connected. The ring counter 72 has, for example, 24 different intervals, the clock signals to control the various components of the facility. The ring counter 72 transmits a signal

the line 73 to the gate 50 which indicates when information from the counters 66A *, 66 / to the shift register 70 is to be transferred. It also sends a signal to a recording amplifier 76 indicating when digital information is to be recorded by a video recorder 78. A similar signal is sent to the shift register 70, which enables it to transmit information to the video recorder 78 via the recording amplifier 76. Another signal is fed to a gate 80, which in turn controls a gate 82 between the shift register 70 and an output register 84. The two digitized X and y signals, like the marker signal, are stored in the shift register 70 and transmitted to the output register 84 via the gate 82. The signal from the gate SO, which is fed to the gate 82, is also given via a delay circuit 85 to the monostable multivibrator 86 with the signal from the clock circuit 42. The multivibrator 86 generates a signal which is applied to a gain control circuit 88 and, at the end of that signal, also generates a signal which is returned on line 52 to the clock circuit 42 to cause that clock circuit to send a signal to reset the pulse height analyzers 36/1, 36fl Generated in each analog computer 26/1, 26ß.

The Λ 'and / coordinate signals in the output register 84 are fed to a digital-to-analog converter 90, which converts them back into X and / -analog signals. Since the signals fed to the digital-to-analog converter 90 are in digital form, when output on an oscilloscope they cause the beam of the oscilloscope to assume certain discrete positions. This results in a dot-like pattern on the screen which can be undesirable for a viewer. For this reason, this pattern is changed by means of a smoothing generator 92, which causes the dots to tend to flow together and represent a continuous pattern.

The X and Y analog signals are fed from the digital-to-analog converter 90 via suitable gating means (not shown) to the rotor 94. Signals from the differential amplifiers 58Z, 5SY can also be fed to the rotor 94 via similar control means. It is of course necessary that signals be supplied only from the digital-to-analog converter 90 or from the differential amplifiers 5SX, 5SY at any given time and that signals do not come from both simultaneously.

The rotor 94 is remotely controlled and mixes the X and Y signals with sine / cosine weight factors to rotate the output image in accordance with the viewer's preference. The rotor 94 may include a resistor matrix for allowing rotation of an image on an oscilloscope 13 by fixed predetermined increments. This is associated with the use of a selector switch to select a particular combination of resistors.

The rotor 94 may also include a sine / cosine resolver which provides continuous rotation of the image by any desired amount rather than fixed increments. In either case, the output of rotor 94 contains four signals instead of two. These four signals represent + X-, - X-, + Y- and - / -coordinates of a scintillator.

The four signals from the rotor 94 are fed to two differential amplifiers 96, which convert them again into two signals which represent the X and / coordinates of the location of the scintillator ion occurring in the scintillator. The output signals of the differential amplifiers 96 are fed to a multiplexer 98 and a dual output controller 100.

The multiplexer 98 also takes signals from the decoder matrix 24 / via the pushbutton switch 28 from the line 30 on. The multiplexer 98 is essentially a circuit which provides the correct signal that the Data processing unit 15 is to be supplied, depending on the operating mode selected by the Operator has been appointed.

Normally, the dual output control 100 has no effect on the operation of the device and the signals from the differential amplifiers 96 only pass through them for output on the oscilloscope 13. If, however, a double isotope operating mode is used, the double output controller 100 operates. In this case, the controller 100 serves e.g. B. to weaken the / signal by a factor of 2. The X signal is also weakened by a factor of 2 and shifted to the left or to the right, depending on the presence of a marker supplied by the output register 84 to the controller. If there is a marker indicating that the signal corresponds to an isotope A , the J signal is shifted to the left. If there is a marker indicating that the signal corresponds to an isotope B , the signal is shifted to the right, or vice versa, depending on the structure of the system.

The data processing unit 15 can be of any type. It contains z. B. an oscilloscope on which the various desired histograms are output. You can also go to the calibration display are used when calibrating the photoelectron tubes.

In tape playback mode, only recorder 78 and playback amplifier 130 are used, together with the rest in Flg. 2 circuit shown. The reproduction amplifier 130 supplies a signal the gate 80 and the ring counter 72 to indicate that the system is in a playback mode. The recorded signals are applied to the shift register 70.

In a "fast analog mode", all of the analog-digital-analog parts of the facility are not used. These include the amplitude-length converter 60Λ ', 60 /, the gates 62λ, 62 /, the oscilloscope 64, the gate circuit 50, the ring counter 72, the gate 80, the shift register 70, the recording and playback amplifiers 76 and 130, the delay circuit 85, the multivibrator 86, the output register 84, the digital-to-analog converter 90 and the smoothing generator 92. In the "fast analog" mode, signals representing X and / coordinates are received directly from the differential amplifiers 58Z mnd 58 / dem Rotor 94 and fed from the rotor via the multiplexer 98 to the data processing unit 15 and to the oscilloscope 13 via the double output control system 100.

For this purpose 2 sheets of drawings

Claims (1)

Claim: Device for recording and reproducing the two-dimensional distribution of radiation emanating from an object to be examined with a scintillation camera, which has a scintillation crystal and several photoelectron tubes, with position signals that characterize the analogue signals emitted by the photoelectron tubes for each flash of light in the position of the flash of light in a given coordinate system and in an evaluation circuit which converts the intensity signal and which is designed as an analog computer and which converts the intensity signal into an adjustable amplitude range for the intensity signals, and with a display device which, under control by the pulse height analyzer, provides a two-dimensional image of the points defined only by the relevant position signals represent those light flashes whose intensity signals fall within a set amplitude range, thereby marked In the evaluation circuit, a second pulse height analyzer (36β), which can be set to an amplitude range different from the amplitude range of the first pulse height analyzer (36A), is provided for the intensity signals and that the transmission fork device (13), through the signals emitted by the second pulse height analyzer (36β), is provided for simultaneous generation of a second, spatially separable from the first image is controllable, which reproduces the two-dimensional distribution of the light flashes assigned to the second amplitude area. 35