JPH0755946A - Quantum counting device - Google Patents

Abstract

PURPOSE:To measure photon energy by providing a circuit means where a pulse of higher waveheight than specified one of an output signal of the detector is modulated by a pulse with a shorter cycle than the pulse duration, and a counting device. CONSTITUTION:A semiconductor radiation detector 1 generates a pulse signal with a waveheight corresponding to the energy of incident X-ray photon. After the pulse signal is led to an amplifier 2 to be converted/amplified into a voltage signal, only a pulse signal whose waveheight is larger than a specified value Vref is extracted, and the discriminated effective pulse is led to an AND gate 5. In the gate 5, a clock pulse, whose cycle is made in advance to be shorter than the duration (pulse width) of effective pulse outputting from a comparator 3, is introduced, so outputting of the gate 5 becomes a signal that the output signal of the comparator 3 is modulated by a clock pulse and the number of pulses after modulation is counted 4. The energy information on incident photon can be obtained from the counted values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quantum counting device used in, for example, a medical X-ray imaging device.

[0002]

2. Description of the Related Art The most widely used technique for obtaining an image of an object using X-rays is X-ray after passing through an object.
It is an X-ray photograph that reproduces the difference in the intensity distribution of the lines as a light and shade distribution of photographic density on an X-ray film.

In addition to expressing such intensity information on a film, a detector array in which a plurality of pixels are arranged one-dimensionally or two-dimensionally includes an X containing information on an object from a radiation source. An X-ray imaging device that makes a ray bundle incident and expresses intensity information thereof on, for example, a CRT is also commonly used.

In the X-ray image pickup apparatus of this type, conventionally, there is a so-called photon (quantum) counting method in which pulse signals generated from a detector upon incidence of X-ray photons are counted and the counted value is used as image information. Has been adopted. The basic circuit configuration of the quantum counter is shown in FIG. The pulse signal generated when the X-ray enters the detector 1 is guided to the comparator 3 through the amplifier 2, where only the pulse having a predetermined peak value (Vref) or more is discriminated, and the pulse after the discrimination. Are counted by the counter 4 in the subsequent stage, and the photon count value is output as image information.

[0005]

In an X-ray image pickup device, an X-ray tube which is usually used as a radiation source has a structure utilizing bremsstrahlung, so that an X-ray to be measured has a wide X-ray spectrum. In most cases, it has a distribution (see FIG. 5).

Therefore, if an image is created by adding X-ray energy information, an image of high quality can be obtained.
In the above quantum counter, it is difficult to obtain X-ray energy information simply and in a short time like an X-ray film or an image intensifier.

That is, according to the quantum counting method, the count value corresponding to one X-ray photon incident on the detector always becomes "1" regardless of the magnitude of the energy of the photon. Measurements other than counting the number of incident X-ray photons (intensity measurement) are impossible.

The present invention has been made in view of such circumstances, and an object thereof is to provide a quantum counting device capable of measuring the energy of photons such as X-rays.

[0009]

In order to achieve the above object, the quantum counting device of the present invention, as shown in FIG. 1 corresponding to the embodiment, has a pulsed signal generated by the incidence of X-rays or photons of light. And a circuit means (for example, a comparator 3, an AND gate 5 and a high frequency wave) for modulating a pulse having a predetermined peak value or more of an output signal of the detector 1 with a pulse having a cycle shorter than the pulse duration. Pulse generator 6),
Counter 4 for counting the number of pulses after this modulation
It is characterized by having.

[0010]

Since the output pulse of the detector 1 is a signal corresponding to the energy of photons such as X-rays, the predetermined peak value (Vre
The pulse duration (pulse width) of the signal above f) will be proportional to the energy of the incident photon. Therefore, the energy of the incident photon can be known by measuring the pulse width. Therefore, in the present invention, the effective pulse having a predetermined peak value or more of the signal from the detector 1 is modulated by, for example, a high-frequency clock, and the number of pulses is counted, so that the above-described pulse duration is A / D. Measure with a conversion method.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram of an embodiment of the present invention.

The detector 1 is a semiconductor radiation detector and generates a pulse signal having a wave height corresponding to the energy of incident X-ray photons. The pulse signal from the detector 1 is guided to the amplifier 2, converted into a voltage signal and amplified, and then the comparator 3 extracts only the pulse signal having a predetermined peak value Vref or more.

The effective pulse discriminated by the comparator 3 is led to the AND gate 5. This AND gate 5 has
The clock pulse from the high-frequency pulse generator 6 is introduced as the other input. Therefore, the AND output after passing through this gate becomes a signal obtained by modulating the output signal of the comparator 3 with the clock pulse, and after the modulation. The number of pulses is counted by the counter 4. Here, the cycle of the clock pulse from the high frequency pulse generator 6 is set smaller than the duration (pulse width) of the effective pulse output by the comparator 3.

In the above configuration, only one detector and its signal processing system are shown. However, when applied to an X-ray image pickup device, for example, the detector 1 is one-dimensional or two-dimensional.
It goes without saying that they are arranged in a dimension and used.

Next, the operation of the embodiment of the present invention will be described with reference to the time chart of FIG. First, assuming that two X-ray photons having different energies are incident on the detector 1 at intervals, in the conventional counting method, as shown in FIG. The count value is "2" regardless of. On the other hand, in the embodiment of the present invention,
As shown in (a) of the figure, when the energy of the incident photon is large, that is, when the duration of the effective pulse passed through the comparator 3 is long, the count value becomes "2" or more for one photon incident. Therefore, energy information of incident photons can be obtained from the count value.

Here, as a means for measuring the duration of the effective pulse, as described above, in addition to the method of modulating the output pulse of the comparator 3 with a high frequency clock, for example, the comparison voltage Vref introduced to the comparator 3 is used. Is modulated with a high frequency clock, or the D / A converter is used as the comparison voltage generator and a method of generating the comparison voltage in the form of high frequency pulse is adopted to measure the duration of the effective pulse. (See the time chart in Fig. 3).

In the above embodiments, the energy of the incident photon can be measured by the signal processing of the output pulse of the amplifier 2, but in addition to this, for example, the bias power supply 1a (see FIG. The photon energy can also be measured by adopting a method in which the high-voltage bias applied to the detector 1 from (see 1) is modulated with a clock pulse or the like.

The present invention is also applicable to an apparatus for counting photons of light, in addition to counting X-ray photons.

[0019]

As described above, according to the quantum counting device of the present invention, a signal having a predetermined peak value or more of a pulse-like signal generated by the incidence of photons on the detector is modulated by a clock pulse or the like. Since it is configured to measure the pulse duration, the energy can be measured in addition to the number (intensity) of incident photons. So, for example, X
If the quantum counting device of the present invention is applied to the X-ray imaging device, it is possible to obtain an X-ray image having high image quality.

Further, according to the present invention, the above effect can be achieved with a simple structure only by adding, for example, an AND gate and a clock generation source to the circuit structure of the conventional quantum counter. is there.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a time chart showing the signal waveform of each part, which is an explanatory view of the operation of the embodiment of the present invention.

FIG. 3 is a time chart of another embodiment of the present invention.

FIG. 4 is a block diagram showing a general configuration example of a conventional quantum counting device.

FIG. 5 is a graph showing a radiation X-ray spectrum.

[Explanation of symbols]

 1 Detector 2 Amplifier 3 Comparator 4 Counter 5 AND Gate 6 High Frequency Pulse Generator

Claims (1)

[Claims] 1. A detector which outputs a pulsed signal upon incidence of X-rays or photons of light, and a pulse having a period shorter than a pulse duration of a pulse having a predetermined peak value or more of an output signal of the detector. A quantum counting device provided with a circuit means for modulating by the above and a counter for counting the number of pulses after this modulation.