RU2273844C1 - Microdose x-ray pulse diagnostics method - Google Patents

Abstract

FIELD: nondestructive check; medicine.

SUBSTANCE: method can be used for nondestructive check of different materials, items and objects by means of pulsed X-rays. Method consists in examining object by pulsed X-ray radiation, converting of radiation, which passed the object by converter, registering of optical image by photo-electric device being time synchronized with x-ray source, converting of signals from analog to digital form, memorizing, processing and translating of image. Irradiation of object and registration of its optical image are performed within time interval between radiation cosmic pulses.

EFFECT: improved sensitivity of image of tested object; reduced radiation dosage.

2 dwg

Description

The invention relates to the field of radiation engineering, namely to fluoroscopy, X-ray diagnostics, and can be used for non-destructive testing of various materials, products and objects using pulsed X-rays, as well as for medical X-ray diagnostics.

A known method [1] of radiation defectoscopy, including the transmission of the controlled object by the flow of penetrating radiation to obtain an optical image of the object and the analysis of the specified image.

The disadvantage of this method is the low sensitivity.

A known method [2] of obtaining an x-ray image, comprising irradiating with a pulsed x-ray radiation a converter behind the object being studied, converting the x-ray into visible, capturing the received image by a video camera, converting the signal from an analog form to digital, storing, processing and transmitting the image.

The disadvantage of this method is that the formation and registration of the image is carried out by irradiation with a package of x-ray pulses. The synchronization of the camera is carried out only by the first pulse of the package of x-ray pulses. The package consists of 4-10 pulses. At the same time, the video camera records not only the useful signal on the X-ray optical transformer at the time of arrival of X-ray pulses, but also radiation and intrinsic noise. This in turn greatly reduces the signal-to-noise ratio.

The closest technical solution to the claimed one is a method [3] for obtaining an X-ray image, including transillumination of the object by pulsed X-ray radiation, conversion of the transmitted radiation object by an X-ray luminescent converter, and recording of the optical image using an optoelectronic analog-to-digital information system. In this case, the time of irradiation and registration of the optical image is set to less than or equal to the radiative time of the X-ray luminescent converter, and the beginning of the exposure of the photoelectronic device is synchronized in time with the X-ray pulse.

The disadvantage of the method [3] with its high sensitivity is that at the time of arrival of the translucent object of the x-ray pulse on the X-ray optical transformer, along with the useful signal, it is also possible to register a radiation cosmic flash. This reduces the signal to noise ratio.

The objectives of the invention are to reduce radiation exposure to the object, increasing the sensitivity and image quality of the studied subject.

This goal is achieved by the fact that the claimed method includes transillumination of an object by pulsed x-ray radiation, conversion of the transmitted radiation object by an X-ray luminescent converter, registration of an optical image by a photoelectronic device synchronized with an x-ray source and subsequent conversion of signals from an analog form to digital, storing, processing and broadcasting the image. In this case, the time of irradiation and registration of the optical image is selected in the interval between radiation cosmic pulses.

Comparative analysis with the prototype allows us to conclude that the technical solution meets the criterion of "novelty."

The applicant is not known from the prior art about the presence of the following symptoms:

1. The duration of exposure and registration of the optical image is in the interval between radiation pulses of cosmic origin.

Thus, the claimed technical solution meets the criterion of "inventive step". In addition, the interaction of the signs results in a new technical result - the signal-to-noise ratio is significantly reduced (relative to the prototype).

The figure 1 presents a structural diagram of a device for implementing this method. The figure 2 shows the density distribution of the frequency of radiation of cosmic pulses by their amplitude.

The method is as follows:

The object 2 under study is illuminated by the pulse of the x-ray source 1, at which the start time is set, and the amplitude is fixed by the control, monitoring and signal conversion system 5. The x-ray converter 3 behind the object 2 converts the x-ray image into a visible image, which arrives at the time-synchronized radiation source optoelectronic information system 4, the electrical signals from which through the control system, control and information processing 5 is transmitted to the monitor Example 6 In this irradiation and tested check time interval in space between the radiation pulses of the command optoelectronic assembly 4, which also monitors the radiation space noise in the vicinity of the test object. Optoelectronic information system 4 is a CCD matrix, image intensifier tubes, PMT, etc.

As an X-ray luminescent converter (converter), X-ray phosphors are used, in which the radiative time is less than the time interval between radiation cosmic pulses. The registration of the optical image from the X-ray luminescent converter can be carried out by various photodetectors synchronized in time with the x-ray radiation source. For example, use is made of a pulsed photoelectronic matrix analog-to-digital device with charge coupling (CCD), the exposure of which is less than the time interval between radiation cosmic pulses. To increase the sensitivity of the optical signal, a pulsed controlled electron-optical converter (EOP) coupled to a CCD pulse matrix is used, the exposure time of which is in the interval between cosmic radiation pulses. An X-ray signal at the output of the object under study can be recorded with a set of a matrix, a ruler, a disk, etc., made up of the same type of X-ray luminescent converters coupled with photomultiplier tubes (PMTs). The amplification of signals in a PMT occurs during a time that is in the interval between cosmic radiation pulses.

Example 1. A controlled object is irradiated with a frequency f = 0.1-15 Hz with X-ray pulses of duration t = 10 ns (quantum energy 120 keV). The conversion of X-ray radiation into optical radiation is carried out using an X-ray luminescent converter based on an effective ZnS-Cds-Ag phosphor, in which the total radiation time (~ 2τ) is 3 μs. In this case, the CCD matrix has an exposure of τ _о = 1 μs, which is less than the radiative time (τ≈1.5 μs) of the X-ray luminescent converter. Registration of the optical image is synchronized in time with the x-ray source. The duration of pulses of cosmic origin does not exceed 12 ns. The density distribution of the amplitude of the repetition frequency of cosmic pulses is presented in figure 2. At the maximum sensitivity of this CCD system, the matrix can register the accompanying powerful cosmic pulses from the X-ray luminescent transducer, which come with a repetition rate of F = 1-2 Hz (see figure 2). Therefore, taking into account the values of τ _о = 1 μs, f = 15 Hz, the probability (A) of detecting the CCD by the cosmic radiation burst matrix almost tends to zero (A = τ _о fF <0.00001). It follows that, even at f = 15 Hz, the CCD matrix records practically only the useful signal of the X-ray luminescent converter and does not register the radiation cosmic background and external optical noise. In direct measurements, upon image acquisition, the object was irradiated with an x-ray pulse with a duration of t = 10 ns and a power (P) of 10 ⁴ P / s, at the moment when a cosmic pulse acts on the X-ray transducer and in the time interval between cosmic radiation pulses, when there is no luminescence excited by cosmic flashes . The experiments showed that compared to the prototype with the same radiation dose (D) (D = Pt = 10 ⁴ P / s × 10 ^-8 s = 10 ^-4 P, 1 P≈1 rad), the signal-to-noise ratio increased by ~ 10 times, which significantly increased the sensitivity to defects and the image quality of the object.

Example 2. The controlled object is irradiated in a single mode with an x-ray pulse of 10 ns duration. The conversion of X-ray radiation into optical radiation is carried out using a plate of an X-ray luminescent converter based on a NaI-T1 crystal, which has a total radiation time of about 650 ns. At the input of the CCD of a matrix operating with a minimum exposure of 1 μs, a controlled electron-optical converter (EOC) with an exposure of 100 ns is connected. The operation of the image intensifier tube is synchronized with the X-ray source and the CCD matrix so that the beginning of the exposure of the image of the CCD matrix occurs after 50 ns from the beginning of the radiation pulse of the X-ray luminescent converter. In this case, the radiation dose is set to the same as in example 1.

The CCD-CCD matrix records the useful signal of the X-ray luminescent transducer for τ _о = 100 ns. The image intensifier has a significant amplification of the optical image (from 100 to 20,000 times). In this case, the sensitivity of the recording system without loss of image quality is increased 2000 times. With this sensitivity, the recording system can capture a concomitant pulse from a series of cosmic flares manifesting themselves on an X-ray luminescent converter with a repetition rate of ~ 1 kHz (Fig. 2). Hence, at F = 1 kHz, τ _о = 100 ns, f <1 Hz, the probability of detecting a spurious cosmic pulse does not exceed 0.0001. In this case, as shown by the tests according to the method of example 1, in comparison with the prototype, without deterioration of the signal-to-noise ratio and the constant energy of x-ray quanta of 250 keV, the maximum thickness of the controlled steel parts without loss of image quality is increased from 10 cm to 12 cm.

Example 3. The controlled object is irradiated with an x-ray pulse of 1 ns duration. The conversion of X-ray radiation into optical radiation is carried out using an X-ray luminescent transducer based on a plate of the composition of Ce ³⁺ : Y ₂ SiO ₅ and CsI, which has a total radiative time of about 40 ns. In this case, also in addition to the input of the CCD matrix operating with a minimum exposure of 1 μs, a controlled image intensifier with an exposure of 10 ns is connected. The operation of the electron-optical converter is synchronized with the X-ray source and the CCD matrix so that the beginning of exposure of the image by the CCD matrix occurs after 8 ns from the beginning of the radiation pulse of the X-ray luminescent converter. Therefore, the CCD matrix registers the useful signal of the X-ray luminescent transducer for τ _о = 10 ns. The sensitivity of the system compared to example 2 was increased by another 10 times and reached the limit on the amplification of the optical image on the image intensifier tube (20,000 times). With such amplification, the recording system can capture a concomitant pulse from a series of cosmic flares that appear on an X-ray luminescent converter with a repetition rate of ~ 10 kHz (Fig. 2). Hence, at F = 10 kHz, τ _о = 10 ns, f <1 Hz, the probability of detecting a spurious cosmic pulse does not exceed 0.0001. In this series of studies, the initial radiation dose rate is P = 10 ⁴ P / s. The radiation dose D = P t = 10 ⁴ P / s × 10 ^-9 s = 10 ^-5 P. As shown by the tests according to the method of example 1, in comparison with the prototype with an additional reduction of the radiation dose by 5 times (2 · 10 ^{- 6} P) and the same X-ray energy of 250 keV, the limiting thickness of the controlled steel parts without loss of image quality remained the same - 16 cm.

Example 4. The controlled object is irradiated in a single mode with an x-ray pulse of 1 ns duration. The conversion of X-ray radiation into optical radiation is carried out using a matrix (5 × 4) or a ruler (1 × 20) assembled from 20 X-ray luminescent transducers made of TU6094425-77 scintillation plastic (total radiation time 20 ns), with which PMTs working without distortion in pulsed gated mode. The operation of these PMTs is synchronized with the x-ray source so that the onset of exposure occurs 2 ns after the start of the radiation pulse of the x-ray luminescent converter. In this case, the PMTs record the useful signal of the X-ray luminescent converters for τ _о = 20 ns. This system has a significant optical image gain (200,000 times). With such amplification, the recording system can capture a concomitant pulse from a series of cosmic flares that appear on an X-ray luminescent converter with a repetition rate of ~ 100 kHz (Fig. 2). Hence, at F = 100 kHz, τ _о = 20 ns, f <1 Hz, the probability of detecting a spurious cosmic pulse does not exceed 0.001. However, given that the amplitude of the parasitic cosmic pulses recorded by the X-ray transducer with a high repetition rate is one to three orders of magnitude lower than for cosmic noise recorded in examples 1-3 (see Fig. 2), we obtain that the final contribution of cosmic noise in the example 4 no more than for examples 2-3. Tests carried out according to the method of example 1 showed that when the radiation dose is the same as in example 3, the signal-to-noise ratio is increased by 10 times. Along with this, at the same energy of x-ray quanta (250 keV), the thickness of the investigated steel parts is increased in comparison with example 3 from 16 to 20 cm

Information sources

1. Zaydel I.N., Leonova N.I., Gurvich V.A., Kuklev S.V. Advances in the development and study of medical X-ray electron-optical converters // Luminescent detectors and converters of ionizing radiation, Novosibirsk: Nauka, 1985. - P.94-98.

2. RF patent No. 2153848, A 61 B 6/00, H 05 G 1/20. Published August 10, 2000

3. RF patent No. 2206886, A 61 B 6/00, H 05 G 1/22, G 01 N 23/04. Published July 30, 2001

Claims (1)

A method of pulsed micro-dose X-ray diagnostics, including transillumination of an object by pulsed X-ray radiation, conversion of the transmitted radiation object by an X-ray luminescent converter, registration of an optical image by a photoelectronic device synchronized in time with an X-ray source, conversion of signals from an analog form to digital, storing, processing and broadcasting an image, characterized in that irradiation of an object and registration of its optical image is performed in ervale time between the cosmic radiation pulses.

Images