RU2597026C1 - Method for recording radiographic images generated by means of ionizing radiation - Google Patents

Abstract

FIELD: radars.

SUBSTANCE: invention is applied to registration of radiographic images generated by means of ionizing radiation; it relates to radiography, in particular, to methods for recording optical images generated by means of proton radiation, and can be used e.g. in digital imaging systems for determination of internal structure of dense objects, or researches of high-speed processes. This invention consists in that, first, ionizing radiation passed through analyzed object, and then through storage luminescent screen, wherefrom image subsequently is read, wherein as ionizing radiation, beam of protons is employed that are accelerated to energy of not less than 10 GeV, and as storage luminescent screen, plate is employed with sensitive layer based on barium fluoro halogenides activated by europium.

EFFECT: technical result is higher translucent capacity at high resolution range, avoiding losses of source information in power conversions, and avoiding geometrical distortions.

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Description

The invention relates to the field of radiography, in particular to methods for recording radiographic images formed using proton radiation, and can be used, for example, in digital recording systems to determine the internal structure of dense objects.

Radiography assumes the presence of a radiation source passing through the object under study and changing its intensity depending on the spatial distribution of the mass thickness, as well as a receiver that registers the radiographic image formed by the radiation.

The registration of radiographic images formed using ionizing radiation, in particular x-ray radiation, is carried out using scintillation converters, for example, based on CsI (patent RU 2472138, publ. 10.01.2013), converting ionizing radiation into optical radiation, which through a rotary mirror, lens and the electron-optical shutter is recorded on a photosensitive film or on a matrix semiconductor sensor.

A scintillation converter circuit can be used to register images generated using a proton beam. The known method of proton radiography, which consists in illuminating the test sample with a beam of protons accelerated in the synchrotron, recording proton images using a multi-frame electron-optical system based on the use of scintillation converters, processing the information obtained in the computer with subsequent restoration of three-dimensional geometry of the sample using low-angle tomography methods (patent RU 2426100, publ. 08/10/2011).

The disadvantage of using scintillation converters is the presence of many stages of converting the energy of the initial radiation: in the scintillator, the energy of ionizing radiation is converted into the optical range, then the optical image is converted to the electronic image on the shutter photocathode, then the electronic image is converted again to the optical on the shutter phosphor, and then its absorption in the semiconductor material sensor with the formation of electron-hole pairs, then the charge is read from the sensor through the anal ogo-digital converter. At each stage of the conversion, the information contained in the original radiographic image is lost. In addition, blurring of the optical image occurs on the scintillator, rotary mirror and lens, as well as blurring of the electronic image inside the electron-optical shutter.

Radiographic, in particular X-ray, images can be recorded directly on an X-ray sensitive film — a triacetate film with a sensitive layer based on iodide and bromide silver salts (patent RU 2188446, published on 27.08.2002), or on an X-ray sensitive film in combination with amplifying phosphor screens ( patent RU 2290664, publ. 12/27/2006). When registering radiographic images on an X-ray film located directly in the field of penetrating radiation, there is no numerous energy conversion, and the film does not introduce geometric distortions into the recorded image. However, the x-ray sensitive film has a narrow dynamic range (~ 10 ² ), which is defined as the ratio of the maximum value of the recorded signal to its minimum value, which does not allow using it for registration of proton images. The ionizing ability of a high-energy proton (10-100 GeV) is more than three orders of magnitude higher than the ionizing ability of a hard gamma quantum (1-10 MeV), and with this type of irradiation, the film immediately goes into saturation mode.

Recently, fluorescent screens made in the form of plates with a halogen-based sensitive layer have been used to register X-ray images (application TW 201442515, published 01.11.2014). In international literature, such screens are referred to as “storage phosphors” or are referred to as “IP” (image plate). Under the influence of ionizing radiation in a sensitive layer of screens, atoms go into a metastable state, and a latent image is formed in it. The image from the screen is scanned by laser radiation in a special device - a digitizer [In the world of non-destructive testing 4 (62) March 2013, p. 65-70.].

In patent RU 2393463, public. 06/27/2010, a phosphor plate is used as a storage screen and the object is illuminated at 10-30% of the voltage applied to the x-ray tube when radiating onto a radiographic film, providing for the plate no more than the film exposure value, according to the computer image received from the phosphor storage plate, the achieved sensitivity of control is estimated and upon receipt of an image from the phosphor storage plate at least high (not higher than mm) than on the radiographic film, the control sensitivity, the applied voltage value on the X-ray tube (radiation energy value) is recorded, and the object being examined is further illuminated on a phosphor storage plate at the indicated fixed voltage on the X-ray tube (radiation energy value) with the corresponding control by standards of the achieved sensitivity of radiographic control. Effect: the use of phosphorus storage plates of reduced, compared with transmission to a radiographic film, voltage on the x-ray tube while maintaining the control sensitivity at the level of control sensitivity achieved on a radiographic film, as well as eliminating the photographic processing of images, making it possible to reuse phosphorus memory plates and automation of the process of decoding radiograms by computer processing. This method is the closest analogue of the claimed invention.

The main advantage of radiography is the prevalence and availability of gamma radiation sources, the main disadvantage is the low transmission ability.

The technical result of the invention is a high transmission ability with a high limit of resolution.

The technical result is achieved due to the fact that in the method of recording radiographic images generated using ionizing radiation, including passing the ionizing radiation first through the object under study, and then through the luminescent screen, from which the image is subsequently read, it is new that, as the ionizing radiation use a proton beam, the acceleration of which is carried out to an energy of not less than 10 GeV, and a plate with a barium fluoride halide-based active layer activated by rare-earth additives.

The use of a proton beam as ionizing radiation, the acceleration of which is carried out up to an energy of at least 10 GeV, allows for a high transmission ability. For example, the mean free path of a proton with an energy of 24 GeV in copper is 13.9 cm, and the mean free path in a copper of a photon with an energy of 10 MeV is 3.6 cm.

The use of a plate with a sensitive layer based on barium fluoride halides activated by europium as a luminescent screen makes it possible to eliminate geometric distortions in the recorded image and eliminate the loss of initial information during energy conversions.

An example of a specific implementation that allows the proposed method to be implemented is a device that is based on the current U-70 synchrophasotron built in Protvino [News and Problems of Fundamental Physics, No. 1 (5), 2009, p. 32-42], and includes a chamber of the IBD, a registration system and the studied prototypes. The registration system is made on the basis of a memory screen in the form of a plate with a sensitive layer based on barium fluoride halides activated by europium.

The inventive method is as follows.

Under the influence of ionizing radiation in the sensitive layer of the screens, the atoms transform into a metastable state and a latent image is formed in it, which is subsequently scanned by laser radiation in the digitizer due to the effect of photostimulated luminescence. After reading, the screen is ready for use again. The limit of screen resolution is determined by the discrete reading of the digitizer, which today reaches 25 microns [In the world of non-destructive testing 4 (62) March 2013, pp. 65-70.]. As well as x-ray film, memories, displays, do not contribute to the measured geometric distortion of the image, but at the same time provide a wide dynamic range (~ 10 ⁴ or more), unobtainable for other systems, which allows to use them as a means of recording of radiographic images formed by high-energy proton beam.

The positive aspects of this method include high translucency, a high resolution limit, the absence of loss of initial information during energy conversions, and the absence of geometric distortions.

Claims (1)

A method for detecting radiographic images formed using ionizing radiation, namely, that the ionizing radiation is first passed through an object to be studied, and then through a storage luminescent screen, from which an image is subsequently read out, characterized in that a proton beam is used as the ionizing radiation, acceleration of which is carried out up to an energy of at least 10 GeV, and a plate with a sensitive layer based on fl is used as a storage luminescent screen orogalogenidov barium activated by europium.