RU2449729C2 - X-ray installation for formation of image of examined object and its application - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to medical equipment, namely to devices for formation of examined object images. X-ray installation contains at least one X-ray source, emitting polychromatic X-ray radiation, first receiver or first unit of receivers of determining values of first intensity of passing X-ray radiation, second receiver or second receiver or second unit of receivers of determining values of second intensity emitted by examined object of fluorescent X-ray radiation, correlation unit, as well as device of output for display of examined object on the basis of signals of image elements. Application of X-ray installation for formation of examined object image, which contains at least one radio-opaque chemical element is realised by X-ray radiation, passing through examined object, and fluorescent X-ray radiation, emitted by said object.

EFFECT: application of invention makes it possible to ensure display of small pathological changes with high spatial resolution with smaller dose of radiation.

22 cl, 7 dwg

Description

FIELD OF THE INVENTION

The invention relates to an x-ray apparatus for forming an image of an object under investigation containing at least one radiopaque chemical element by means of x-ray radiation, to the use of an x-ray apparatus, and also to a method for radiopaque imaging of an object under study, for example, a mammal, especially a human.

State of the art

X-ray medical diagnostics is a technically highly developed section in the diagnosis of diseases, for example, for their timely recognition, radiographic confirmation, characterization and localization of tumors, vascular diseases and other pathological changes in the human body. The technique is very effective and has a high degree of accessibility.

X-ray tubes are used to generate x-ray radiation with tungsten, molybdenum or rhodium-plated rotating anodes and aluminum, copper, titanium, molybdenum and rhodium-plated filters. Appropriate filters allow you to filter out part of the bremsstrahlung, therefore, in favorable cases, essentially characteristic radiation enters the output of the x-ray tube.

As receivers (detectors), conventional x-ray films, floppy disks of drives or digital planar receivers are used. Computer tomographs use single-line receivers or multi-line receivers. It is also possible parallel connection of several receivers. For direct conversion of X-rays into electrical signals, semiconductor receivers (detectors) are used, based on cadmium telluride (CT), cadmium zinc telluride (CZT), amorphous selenium, or amorphous or crystalline silicon (MJYaffe, JARowlands, “X- Ray Detectors for Digital Radiography ", Med. Biol, 42 (1) (1997) 1-39).

An example of the design of such receivers is given in US Pat. No. 5,434,417 A. In order to ensure the energy sensitivity of the receiver, it is composed of several layers. X-rays with different energies penetrate into this receiver at different depths and, due to the photoelectric effect, generate an electrical signal in the corresponding layer, which can be directly read out as a current pulse with identification by the layer and, therefore, by the energy of X-ray photons.

Computed tomography (CT) has long been used in everyday clinical practice. CT allows you to get body pictures in a section with improved spatial resolution compared to conventional projection radiography. Despite the fact that the resolution in density at CT is much higher than the resolution in density with conventional X-ray technology, radiopaque preparations are required for more reliable recognition of many painful changes. They improve the quality of morphological information. In this case, the contrast agent allows, on the one hand, to present the functional processes in the body (excretion, perfusion, permeability), and, on the other hand, to emphasize the morphology by creating contrasts (different concentrations of radiopaque substances in various tissues).

In many cases, conventional X-ray technology could not be used, since the contrast of the test tissue was insufficient. For this purpose, radiopaque substances have been developed that create a high radiographic density in the tissue in which they accumulate. Typical examples are iodine, bromine, elements with serial numbers 34, 42, 44-52, 54-60, 62-79, 82 and 83 as radiopaque elements, as well as intra-complex compounds with serial numbers 56-60, 62-79, 82 and 83. Of the iodine compounds, for example, meglumine sodium or lysine diatrizoate, yotalamate, yoxitalamate, iopromide, yohexol, yomeprol, iopamidol, yoversol, yobitridol, iopentol, iotrolan, iodixanol and yoxylan (IN8816) can be used (INN16) A1).

In certain cases, despite the introduction of radiopaque substances, it was not possible to achieve sufficient tissue contrast. To further enhance contrast, digital subtractive angiography (DSA) was introduced, in which pre-contrast and post-contrast images (logarithmically) are subtracted from each other. A subtraction method for use in mammography is described in EP 0885616 A1: For projection mammography, it is proposed to first remove a high-contrast mammogram, then quickly introduce an intravenous urographic radiopaque drug to the patient, and take a post-contrast mammogram after about 30 seconds after the injection. The obtained data of both pictures are correlated with each other, preferably subtracting one from the other.

New developments in the field of computed tomography with regard to radiation excitation refer, for example, to the use of synchrotron radiation in CT (FADilmanian “Computed Tomography with Monochromatic X-Rays”, Am. J. Physiol. Imaging, 314 (1992) 175-193 ) Good x-rays can be obtained, for example, through the so-called “K-edge subtractive computed tomography” (F.A.Dilmanian, p. 179), and a strong increase in the absorption coefficient in the binding energy of the K-electrons of the atom is used. The iodine element has a K-line at an energy of 33.17 keV. Unfortunately, this method operates only with the help of synchrotron radiation obtained on large storage rings, for example DESY, since this radiation has monochromaticity and intensity favorable for the method. Conventional x-ray tubes produce not monochromatic radiation, but a continuous spectrum. Therefore, they are not suitable for such differential measurements.

An alternative possibility is described in DE 10118792 A1. Here, for the removal of projection mammograms, a method is proposed in which X-ray sources with two X-ray anodes from various materials are used. To take mammograms, the patient is first injected with a radiopaque substance. Then, the first projection image is made using the first of two x-ray anodes, after which the second projection image is used using the second x-ray anode. By superimposing each individual image element of the first image onto each individual image element of the second image, a correlation image is produced. The characteristic radiation of both X-ray anodes is consistent with the absorption spectrum of the X-ray contrast material. The radiation energy of the first x-ray anode is slightly lower than the absorption energy of the contrasting element in the radiopaque material, and the radiation energy of the second anode is slightly higher than the absorption energy of the contrasting element. The disadvantage of this method is that conventional x-ray tubes with one x-ray anode have to be replaced by two-anode tubes.

In addition to transmission radiography, emission radiography is described.

Thus, document WO 2004/041060 A2 describes a device for non-invasively determining in vivo a chemical element in a human prostate, consisting of a probe, an irradiation system capable of exciting radiation from a chemical element, a radiation receiver inside the probe that allows the detection of the detected radiation, and a recording system , processing and displaying signals, allowing to determine the amount of a chemical element in various areas of the prostate in accordance with the display of detected radiation. The emitted radiation is mainly fluorescent radiation. In the case of prostate examination, the distribution of zinc in the tissues is preferably determined.

DE 3608965 A1 further describes a method for determining the proportion of various chemical elements in a layer of a test zone by gamma or X-ray radiation. In this case, Compton and Rayleigh scattered radiation are separately recorded. The nature of the differential scattering coefficient determined from the measurement data depends on the proportions of various chemical elements in individual image elements. Therefore, it allows you to determine the proportion of these chemical elements. To do this, the studied zone is illuminated by the primary beam from a large number of directions, and the radiation emitting at different angles from the studied zone is detected by the receiving (detector) device in various positions outside the studied zone, after which the difference scattering coefficient is determined from the measurement results different transmitted pulses of each image element in the layer.

Along with this, Quanwen Yu et al. In “Preliminary Experiment of Fluorescent X-Ray Computed Tomography to Detect Dual Agents for Biological Study”, see J. Synchrotron Rad. (2001), 8 1030-1034, suggest using the X-ray fluorescence method to determine very low concentrations of non-radioactive substances in biomedical research. Using this method, it is possible to obtain images that allow the use of the _Kα fluorescence line in one study to simultaneously detect multiagents in order, for example, to quantify the blood flow in the brain and the density of brain cells. In the presented study, images obtained by this method were compared with images obtained using x-ray transmission tomography.

True, the method of X-ray fluorescence or X-ray scattered light described in the above publications has the disadvantage that the presentation of small details in the object under study is rather difficult due to the difficulties of display. Moreover, images are obtained only with a rough resolution, which does not allow you to present small details in the picture.

Disclosure of invention

Based on the foregoing, the objective of the invention is to avoid these drawbacks and, above all, to create installations and methods that allow you to get pictures with various radiopaque chemical elements. Further, obtaining x-rays should also be simple, convenient and economical. Research techniques should be available on a broad basis. It is necessary to ensure that even small pathological changes are displayed in the studied object with high spatial resolution at the lowest possible radiation dose. It is necessary to avoid image defects caused by the movement of the object.

The problem is solved by using an x-ray setup for forming an image of an object under study containing at least one radiopaque chemical element, by means of x-ray radiation according to claim 1, the use of this apparatus according to claim 11 and the method of radiopaque image formation according to claim 25. Preferred embodiments of the invention are described in the dependent claims.

If the terms “emitted radiation” and “emit” are used in the description of the invention and in the claims, then this should be understood, firstly, X-ray fluorescence, i.e. emission of radiation after excitation of the irradiated matter by electromagnetic radiation and, secondly, preferably, Rayleigh scattering. In the latter case, radiation without momentum transfer is again emitted (re-radiation) by the irradiated matter, however, as a result of irradiation, however, the shell electrons in the atoms of this matter do not go into an excited state, as in fluorescence.

To form an image, an x-ray unit uses the x-ray radiation emitted through the object under study. For this, the x-ray apparatus according to the invention comprises:

a) at least one x-ray source emitting essentially polychromatic x-ray radiation,

b) the first receiver or the first block of receivers, configured to determine the values of the first intensity of the x-ray radiation passing through the studied object,

C) a second receiver or a second block of receivers, configured to determine the values of the second intensity of the x-ray radiation emitted by the investigated object,

g) at least one correlation unit, configured to correlate, according to image elements, the values of the first intensity of the transmitted x-ray radiation with the values of the second intensity of the emitted x-ray radiation, and

d) at least one output device for displaying the object under study based on the signals of the image elements obtained by correlating the values of the first intensity with the values of the second intensity.

Transmitted x-rays and emitted x-rays can be detected (detected) simultaneously or sequentially one after another.

This x-ray unit can be used to form an image of an object under study containing at least one radiopaque chemical element by means of x-ray radiation. The radiopaque chemical element is preferably introduced into the test object with a radiopaque substance, which for this is introduced into the object of study, for example, into a human or animal organism.

X-ray contrast chemical elements with a low ordinal number, which are naturally present in the studied object, give only an insignificant yield of X-ray fluorescence, therefore, imaging using these elements seems to be practically inappropriate. In addition, the energy of X-ray fluorescence photons in this case is small, so that their distribution in the tissues of the body is negligible. In particular, starting with the iodine element (serial number 53) with emission lines of 28.6 and 32.3 keV, fluorescence lines are available that quite intensively leave the object under study and can be detected by a receiver located outside the object. In cases of a lower ordinal number of the chemical element, the location of the second receiver should be chosen as close as possible to the studied zone (or the zone of interest).

This x-ray unit is used to implement the proposed in the invention x-ray contrast research method. The method includes the following operations:

a) preferably carried out the introduction into the body of at least one x-ray contrast chemical element,

b) transillumination of the investigated object essentially polychromatic x-ray radiation,

c) determination of the values of the first intensity of the x-ray radiation passing through the studied object,

g) determining the values of the second intensity of the x-ray radiation emitted by the object under study,

e) correlation of the values of the first intensity of the transmitted x-ray radiation performed by the image elements with the values of the second intensity of the emitted x-ray radiation, and

f) displaying the test object based on the signals of the image elements obtained by correlating the values of the first intensity with the values of the second intensity.

In contrast to the known methods in which either only transmission X-ray computed tomography (TRF) is performed or X-ray fluorescence (fluorescence X-ray computed tomography - CT) is detected, in the present invention the transmitted and emitted radiation are measured simultaneously or sequentially and combined with each other according to the present invention, and the resulting image through the appropriate method of correlation (correlation) are superimposed on one another. This approach allows you to take advantage of both technologies.

The advantage of transmission X-ray tomography is its high temporal and spatial resolution, which makes it possible to detect even the smallest pathological changes or other details in the studied human body. However, the contrast obtained is often not sufficient to visualize these details. This primarily refers to the study of soft tissues. In addition, the study of certain parts of the body by TRKT is complicated by the bone skeleton.

On the other hand, fluorescence x-ray tomography has the advantage of an extremely contrasting representation, since exceptionally certain chemical elements emit electromagnetic radiation when they are properly excited, therefore the elements located in the studied area can serve as extremely sensitive measuring probes. However, the CTGF method has the disadvantage that it provides only a small spatial resolution and does not allow to display small pathological changes.

Only correlation of the values of the intensity of the transmitted x-ray radiation according to the elements of the invention (from one image element to another) with the values of the intensity of the emitted x-ray radiation and the representation of the studied object on the basis of the signals of the image elements obtained by such a correlation allows creating a contrasting and detailed image of the studied area . True, the part of the image that provides contrast has a low resolution. By correlating the corresponding values with each other, this drawback can be almost completely eliminated, since the necessary detailed information is determined by the values of the radiation intensity measured by the TRKT method.

The invention is particularly intended for human research. It can be used for radiographic imaging to display spatial requirements, blood vessels and perfusion, such as the esophagus, gastrointestinal tract, for bronchography, cholegraphy, angiography and cardioangiography, for cerebral angiography and perfusion measurements, for mammography, as well as for lymphography. The main direction of the use of the invention is computed tomography (multislice computed tomography - MSCT, computed microtomography CMVT) and its varieties PET (positron emission tomography), SPECT (single-photon emission computed tomography), sonography and other methods of optical imaging. In principle, the invention can also be used to study inanimate matter, for example, in the field of material control.

To conduct the study, the transmitted radiation is recorded by the first receiver located on the path of the rays of the x-ray tube, weakened by the studied object. The emitted radiation is measured by means of a second receiver located outside the course of the rays, preferably at an angle of 90 ° to the course of the rays. This second receiver can, in principle, be installed at any other angle to the x-ray, for example, at an angle of 45 ° or 135 ° to the beam of the x-ray source, however, it should not be in the path of the beam passing through the object under study. If the x-ray tube is in the 12 o'clock position, then conventional CT scanners are equipped with a number of receivers installed in the opposite position at 6 o’clock. It is preferable to have the second receiver in the 3 o'clock or 9 o'clock position. By means of this second receiver, both x-ray fluorescence and x-ray scattering (Rayleigh, Compton scattering) can be detected.

To selectively register images with a second receiver using the emitted x-ray radiation, the energy of the emitted x-ray radiation can be measured with good resolution. In particular, it is preferable, in the presence of a given radiating chemical element in the object under study, to distinguish (discriminate, or isolate) the X-ray radiation received by the second receiver from the X-ray contrast element, from another emitted X-ray radiation, for example, scattered radiation (Compton, Rayleigh radiation) and fluorescent radiation other chemical elements. This allows you to very clearly represent certain areas of the study using, for example, clusters of radiopaque chemical elements in certain organs of the human body, using a large contrast between the highlighted radiation from the tissue and the surrounding tissues. Even the structure caused by the bone skeleton in the resulting image in this case recedes into the background compared to the image of the tissue, so that the bone skeleton practically does not interfere with the image.

To detect and determine the characteristics of the emitted radiation, it is preferable to use an energy dispersive receiver. However, one can use simpler receivers for this and determine radiation characteristics by means of X-ray optical modules (combination of filters, monochromators).

In addition, this principle can be applied in the same way to measuring the intensity of transmitted x-ray radiation by the first receiver. In this case, a selective image of the zones in the studied object is achieved in which X-ray contrast chemical elements accumulate.

Thus, the invention also allows the contrast to display soft tissue, for example, in the human body. By matching the energy or energy range of the transmitted and emitted x-ray radiation detected by the receivers with the appearance of the radiopaque chemical element, an effective contrast enhancement can be achieved compared to other methods.

To generate x-rays, you can use a conventional, continuous spectrum x-ray tube, such as a molybdenum, tungsten or rhodium anode tube. Depending on the type of the radiopaque chemical element contained in the test object, a voltage is applied to the anode that provides continuous radiation, for example, in the range of over 100 keV.

In principle, an X-ray source can operate without outgoing radiation, as a result of which polychromatic radiation enters the object under study in the entire spectrum. However, to reduce the radiation load on the object under study, it is also possible to filter out such x-ray radiation from the spectrum of a polychromatic source of x-rays, the energy of which is not required or is not desirable for detection. To do this, for example, an aluminum or copper filter is used, which filters out energy in the range of ≤20 keV (soft radiation). Thus, the continuous spectrum should be understood as x-ray radiation in the range of ≥0 keV, more preferably ≥15 keV, even more preferably ≥17 keV and particularly preferably ≥20 keV, for example up to 100 keV, and no spectral range within these limits is distinguished relative to others and not excluded. The upper limit of the emission spectrum is determined by the voltage applied to the x-ray anode.

The low-energy radiation region is preferably filtered out to exclude a radiation dose that is hazardous to the human body.

Usually, an appropriate receiver is used to study an object with polychromatic x-ray radiation. Alternatively, an energy dispersive receiver can be used to determine the energy of the photons incident on the object.

There are two fundamentally different options for the implementation of energy dispersive receivers and receiver blocks:

a) A description of energy dispersive receivers according to the type of cadmium (zinc) technetium receivers is contained in the introductory part. Such a series of receivers makes it possible to measure x-ray spectra of x-ray radiation from image elements.

b) Simple x-ray receivers are used. A discriminator is installed in front of the receiver, which in the simplest case is an appropriate combination of filters. However, for energy selection, monochromators can also be used, tuned, for example, to X-ray fluorescence of a radiopaque substance introduced into the body.

c) However, it is technically quite possible to tune the receiver directly to a radiopaque substance. So, you can use the gadelin (zinc) technetium or dysprosium (zinc) technetium receivers.

In all cases, the receiver, if possible, is positioned so as to measure the minimum of Compton scattering.

In order to determine the intensity values, as well as the energy of the x-ray radiation emitted by the object under study, the detected photons are divided into at least two different energy ranges, containing, for example, the emission lines K _α and K _β . To increase the specificity of elements, in some cases, a correction for Compton scattering can be introduced. However, as the examples below show, this is not always required.

If you abandon the inherent x-ray contrast, it is possible to implement the proposed in the invention method to introduce into the object under study, for example, the human body, a radiopaque substance. The radiopaque substance can be administered, for example, enterally or parenterally, especially in the form of an intravenous, intramuscular or subcutaneous injection or infusion. After that, an x-ray is taken. Suitable radiopaque substances that in a selected region of the spectrum themselves have a high attenuation coefficient. X-ray contrast substances, the absorbing element of which has the K-edge of the absorption spectrum in the selected spectral range, are also quite suitable. Such radiopaque substances contain radiopaque chemical elements with an ordinal number of 35 or greater than 35 (in this case, for example, radiopaque substances containing bromine), with an ordinal number of 47 or greater 47 (for example, radiopaque substances containing iodine) , with an ordinal number of 57 or greater than 57 (in this case, for example, radiopaque substances containing lanthanides, primarily radiopaque substances containing gadolinium), or with an ordinal number of 83 (here tons of radiopaque substance containing bismuth). Therefore, radiopaque substances containing radiopaque chemical elements with ordinal numbers from 35 (bromine) to 83 (bismuth) are used. Also suitable are radiopaque substances with radiopaque chemical elements having ordinal numbers from 53 (iodine) to 83 (bismuth), as well as with an ordinal number of 57 or more 57 (lanthanides) to 83 (bismuth), and substances with radiopaque chemical elements are especially preferred. having ordinal numbers 57-70 (lanthanides: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb).

Suitable iodine-containing radiopaque substances are, for example, compounds containing triiodic aromatic hydrocarbons, in particular amidotrizoate, iohexol, iopamidol, iopanoic acid, iopadic acid, iopromide, ioproic acid, iopidone, iotalamic acid, iopentol, yoversolan, yo-yolansol, yo-yolansol, yo-yolansol, yo-yolansol, yo-yolansol, yo-yolansol yotroksinic acid, yoksglinovy acid, yoksitalaminovy acid and yosimenol (INN). Brand names for radiopaque substances containing iodine are Urografin® (F. Schering), Gastrografin® (F. Schering), Biliscopin® (F. Schering), Ultravist® (F. Schering) and Isovist® (F. Schering).

Metal complex compounds are also used as radiopaque substances, for example, Gd-DTPA (Magnevist® (F. Schering)), Gd-DOTA (Gadoterate, Dotarem), Gd-HP-DO3A (Gadoteridol, Prohance® (F. Bracco)), Gd -EOB-DTPA (Gadoxrtat, Primavist), Gd-BOPTA (Gadobenat, MultiHance), Gd-DTPA-BMA (Gadodiamide, Omniscan® (F. Amersham Health)), Dy-DTPA-BMA, Gd-DTPA-Polylysin, cascade polymers Gd-DTPA and others, with DTPA = diethylene triamine pentaacetic acid, DOTA = 1,4,7,10-tetraazacyclododecane, HP-DO3A = 10- (hydroxypropyl) -1,4,7,10-tetraazacyclodecane-1,4, 7-triacetic acid), EOB-DTPA = 3,6,9-triase-3,6,9-tris (carboxylmethyl) -4- (4-ethoxybenzyl) undecandicrabonic acid, BORTA = (4-carboxy-5,8,11-tris (carboxymethyl) -1-phenyl-2-oxa-5,8,11-triazatridecan-130-ois, benik oxide), DTPA-BMA = diethylene triamine pentaacetate bis (methylamide ), DTPA-polylysine = daethylenetriaminepentaacetate-polylysine, cascaded DTPA polymers.

X-ray contrast agents can be administered enterally or parenterally. In parenteral administration, intravenous administration (i.v.) is preferred. Preferred dosages for iodine-containing non-ionic radiopaque substances are doses up to 0.75 g / kg body weight. This corresponds to approximately 6 mmol / kg body weight. In the future, the dose can preferably be increased to 1.5 g / kg body weight (which corresponds to about 12 mmol / kg body weight), and in exceptional cases, up to 2 g (i.e. 16 mmol) or up to 5 g (39 mmol ) per 1 kg of body weight. For lanthanide complex compounds, the preferred dose is 0.1 mmol / kg body weight. Dosages of up to 0.3 mmol / kg body weight or up to 1 mmol / kg body weight are suitable and also preferred.

The gadolinium emission spectral lines correspond to 43.0 and 48.7 keV, i.e. these values are higher than for iodine, for which they are 28.6 and 32.3 keV. Complex compounds of metals may, instead of gadolinium atoms, include, for example, all other lanthanides, especially lanthanum or ytterbium.

Digital receivers have been available for some time by various manufacturers (e.g.: The BBI Newsletter, February 1999, p. 34; HGChotas, JTDobbins, CERavin “Principles of Digital Radiography with Large-Area, Electronically Readable Detectors: A Review of the Basics, Radiol 210 (1999) 595-599). Often they consist of amorphous silicon or other semiconductor materials. The following detectors are used primarily in the X-ray unit according to the invention: receivers with phosphor plates (e.g. f. Fuji Chemical, Konica), with amorphous silicon (e.g., f. GE Medical, Philips Medical, Siemens Medical), with selenium ( e.g. Philips Medical, Toshiba), with gadolinium hyposulfite (e.g. Kodak), semiconductor elements made of cadmium telluride (CT) or cadmium zinc telluride CZT), with yttrium oxyorthosilicate, lutetium oxyorthosilicate, sodium or germanium . Especially good results are achieved with the so-called C (Z) T receivers, i.e. with receivers made of semiconductor cadmium telluride material - (C (Z) T).

A detailed description of the design of the energy dispersive receiver of semiconductor material is given in US Pat. No. 5,434,417 A. In this case, segmented semiconductor tapes are provided that are irradiated with X-rays from the front side. The radiation passes into the semiconductor material and begins to interact with the semiconductor material. The penetration depth depends on the energy of x-ray photons. With a greater energy of X-ray photons, radiation penetrates deeper than with a lower energy of X-ray photons, until it begins to interact with the receiver material and generate a current pulse under the action of the photoelectric effect. Current pulses in individual segments of the receiver can be removed from the electrical contacts installed there. Current pulses are processed in a preamplifier.

The receiver, firstly, can be made planar type. In this embodiment, all image elements are recorded simultaneously and sent for analysis to the correlation unit. In this case, the receiver is a flat circuit of individual detector sensitive elements (sensors), preferably in the form of a matrix in which the detector sensitive elements are arranged in rows and columns.

Secondly, a receiver unit may be provided, which serves to determine the emitted x-ray radiation and is configured to form an image in the emitted rays, and for this is made with an x-ray optical module for energy selection.

Instead of a planar receiver, line receivers or an array of several receivers can also be used to capture a single image element. In such receivers, x-ray radiation from the object under study is simultaneously directed along the x-ray fibers. Many of these optical fibers are combined into a planar receiver.

In addition, the receiver may be configured to register one individual image element and mounted to move to register all image elements. In this embodiment, the receiver during measurement can only register volatile intensities in a single image element. The intensity values of individual image elements are recorded sequentially, for example line by line, and for further processing are sent to the correlation block.

In addition, the receiver may contain a matrix of detector sensitive elements; it contains a matrix of detector sensitive elements, each of which is configured to register a corresponding image element, which is set to move to register all image elements. An array of detector sensors according to the present invention is understood to mean both a row of detector sensors and another circuit of detector sensors, for example a tabular one. In this embodiment, the receiver registers the intensity values in individual image elements line by line or in some cases block by block. In order to record all intensity values, the receiver during measurement preferably moves perpendicular to the main axis of the matrix. The intensity values determined during the measurement are transferred for processing to the correlation unit.

To form an image, for example, the distribution of radiopaque chemical elements in the studied object, it is advisable to register the intensity of the radiation emitted by the corresponding spatial elements with the same significance. Further, for this purpose, it is also advisable to act on spatial elements by radiation of the same intensity from an x-ray source. However, in practice, it turns out that these premises exist only conditionally, since, on the one hand, the incident x-ray radiation in the object under study is attenuated to varying degrees by absorption, depending on the path traveled by the rays to the receiver, and, on the other hand, the radiation emitted by the spatial elements in the studied object, depending on which path the rays in the studied object still have to go to the receiver, is weakened to various degrees by its own absorption.

This problem is inherent in all emission spectroscopic methods. In order to solve this problem, the values of the second intensity are first corrected taking into account the absorption of the incident X-ray radiation and / or the intrinsic absorption of the emitted X-ray radiation in the object under study, and only after this correction is the correlation of the values of the first and second intensity carried out by the image elements. Such correction can be performed using digital methods, taking into account the geometric shape of the object under study and at least approximately spatially dependent density of x-ray radiation. To determine the spatially dependent density of x-rays, images obtained from the values of the first intensity can be used. To determine the spatially dependent absorption and intrinsic absorption, we can take as a first approximation the spatial dependence of the x-ray density obtained by measuring, as the absorption coefficients of the transmitted and emitted x-rays are identical.

Further, taking into account the intrinsic absorption of the emitted radiation, it may be appropriate to change the position and installation angle of the second receiver relative to the studied area during the measurement, for example along an arc trajectory, in order to compensate for structural inhomogeneities in the studied object, which, depending on the angle and location of the observation, can have different absorbing effects . Images in this case could be obtained after correction by averaging.

The signal processed in the pre-amplifier is then sent to at least one correlation block, in which the intensity of the transmitted x-ray from the image element of the object under study is related to the picture of the emitted x-ray radiation (x-ray scattering and x-ray fluorescence) from the same image element. The correlation unit may be a data processing device programmed accordingly.

To correlate the values of the photon intensities of both modalities (the image in transmitted (transmission) and emitted (emission) rays) they are compared element by element, preferably they are subtracted from one another or divided into one another. To establish a correlation from an element to an image element, one can use a comparator, and in the other case, a dividing link. Of course, other mathematical operations can be performed to correlate the intensities of the transmitted and emitted X-ray radiation from the image element.

To process the measured values of the intensity of the image element, preferably the following devices are provided that can be implemented in a data processing device:

g1) a first storage device configured to store, according to image elements, the values of the first intensity of the passing x-ray radiation,

g2) a second storage device configured to store, according to the image elements, the second intensity values of the emitted x-ray radiation (for example, with elements I, Gd, Yb),

d3) a computing device configured to appropriately correlate both generated sets of image data and, thus, based on data from a set of data obtained in transmitted rays and data obtained on the basis of emitted x-ray radiation, preferably x-ray fluorescence, to generate or calculate image data set.

This makes it possible to correlate the intensities of all image elements for transmitted and emitted radiation, and the emission pattern along the characteristic spectral lines of emission is tuned to the used radiopaque substance. If you use a mixture of radiopaque substances (for example, Ultravist® and Gadovist®) or substances containing both iodine and any lanthanide (primarily Gd or DY), then you can use the appropriate characteristic spectral lines of emission to form an image in the emitted rays, moreover, the measured data sets are then correlated by image elements with each other and used to form an image or, alternatively, the corresponding intensity values are correlated by image elements and obtained nnye data is then used for image formation. For this, the obtained data is transmitted element by element to an output device, which contains, for example, a monitor (on a cathode ray tube or liquid crystals) or a plotter.

The invention is explained in more detail by the following figures and examples. In order to get a direct idea of the principle of operation of the invention, it was decided in all cases to refuse to correct the measured X-ray spectra in accordance with the absorption of the exciting beam and intrinsic absorption.

Brief Description of the Drawings

The drawings show:

figure 1 - view of the experimental device in a computed tomograph,

figure 2 - diagram of a device for obtaining images or an experimental device,

figure 3 is a diagram of an experimental device for generating the first phantom measurements,

figure 4 - radiation spectra of the phantom of figure 3, filled with water (figa), preparations Ultravist® (fig.4b), Gadovist® (fig.4c),

in Fig.5 - emission spectra of the phantom of Fig.3 filled with water (Fig.5a), Ultravist® preparations (Fig.5b), Gadovist® (Fig.5c), and in each case a polymethylmethacrylate plate was installed between the receiver and the phantom 5 cm

Fig.6 - radiation intensity depending on the position / displacement of the phantom from Fig.3 in the selected energy zones (in accordance with the lines K _α and K _β ) (iodine: Fig.6a, gadolinium: Fig.6b, a mixture of iodine and gadolinium : figv),

7 is a sectional view of computed tomography (transmission image) of a phantom filled with Gd, a mixture of iodine / Gd, iodine, air and water.

The implementation of the invention

Figure 1 shows a photograph of an experimental device in a computer tomograph with a rubber ball 1 mounted on a tripod 2. The rubber ball is located in the center of the computer tomograph. In various experiments, a rubber ball was filled with air, water, and various radiopaque substances. The ball was between the tube of a computer tomograph (above the rubber ball; not shown in the figure) and the horizontal receiver (under the table located under the rubber ball; not shown in the figure).

At an angle of 90 ° to the line connecting the computed tomography tube, the rubber ball, and the receiver, a measuring chamber 3 was installed to determine X-ray fluorescence. This experimental device simulated tissue, a tumor, or another fragment of an object examined in a computer tomograph filled with X-ray contrast material. For this, the object was scanned in layers, while measuring the scattering spectra.

The experimental device used for this experiment is shown in detail in FIG. 2. In the diagram presented there, you can see the ball 1, which, as a phantom, was in the isocenter of the rack 4. The tube 5 of the CT scan was located at 12 o’clock and was fixed in this position. The measuring chamber 3, consisting of a receiver 6 and a lead tube 7, was calibrated at an angle of 90 ° to the conical x-ray coming from the tube of a computer tomograph and aimed at the phantom (ball) (in the z direction; see arrow).

To detect X-ray radiation, a CZT 6 detector was used with a cadmium-zinc telluride crystal 3 mm × 3 mm × 2 mm in size and 100/400 μm diaphragms (Amptek Inc., USA). The data recorded by the fluorescent receiver was transmitted from the receiver through an amplifier 8 to a multi-channel analyzer 9, and then output to an Excel® graphic table (Microsoft) stored in the memory of personal computer 10. Thus, the signal intensities SI = SI (E) could be processed digitally form as a function of energy E.

Figure 3 presents a diagram of an experimental device for generating the first phantom measurements. A part of the measuring chamber 3 for measuring fluorescence is shown on the left side of the figure, and a ball 1 is shown in the middle. Individual sectional planes located vertically in FIG. 3, of which fluorescence radiation enters the measuring chamber, were generated by a fan-shaped x-ray incident from above. Dotted lines indicate the position of the computer tomograph tube above the cutout of the image. The horizontal scale shows the displacement of the fan-shaped beam and, consequently, the corresponding section plane (excited layer) in the ball.

“Zero measurement” was carried out at a level of +45 mm, i.e. outside the exciting beam.

After each recording of the spectrum, the measuring device moved 10 mm further into the matrix (in the z direction), and a new spectrum was recorded. Thus, different spectra arose in layers depending on the position of the ball in the beam or in accordance with the geometry of the ball.

Thus, the measuring device made it possible to measure X-ray fluorescence depending on the phantom topography, and at z = -60 mm the layer closest to the receiver was revealed, and at z = 0 the layer farthest from the receiver (therefore, at z = -60 mm intrinsic absorption of radiation is minimal, and at z = 0 it is maximum; due to the spherical geometry, the absorption effect is also noticeable in the transmitted beam at elevated concentrations of radiopaque material).

Example 1

In the first measurement, the ball was filled with water, and at 80 kV, 50 mA for 80 s in each position of the ball in the path of the beam according to Fig. 3, radiation was measured (parameters: XR-100.CZT receiver (diaphragm 0.1 mm), distance from the ball to the receiver: 18.0 cm, the distance from the ball to the tube of the x-ray tomograph: 32.0 cm).

Figure 4a shows the scattering spectra of water in a phantom for various positions.

In the second measurement, the ball was filled with a solution of 50 mmol / l iodine in water (Ultravist®), and at 80 kV, 50 mA for 80 s, radiation was measured at each position of the ball (parameters: XR-100.CZT receiver (0.1 mm diaphragm )).

The obtained emission spectra in various positions are presented in fig.4b). The lines of K _α and K _β iodine (28.6 and 32.3 keV) are clearly visible in the figure. The graphic image shows the dependence of the measured X-ray fluorescence intensity on the phantom geometry. The greater the thickness of the translucent phantom layer, the higher the measured intensity.

In the third measurement, the ball was filled with a solution of 50 mmol / L gadolinium in water (Gadovist®), and at 80 kV, 50 mA for 80 s, radiation was measured at each ball position (parameters: XR-100.CZT receiver (0.1 mm diaphragm )).

The obtained emission spectra in various positions are presented in figv. The lines K _α and K _β gadolinium (43.0 and 48.7 keV) are clearly visible in the figure. It was found that the intensity of the measured radiation, especially in the zone of K-lines, depends on the geometry of the ball in the field of rays.

Example 2

For individual measurements in this experiment, a 5-cm-thick polymethylmethacrylate plate was installed between the receiver and the phantom to simulate the intrinsic absorption of fluorescence X-ray radiation from surrounding tissues.

Fig. 5a shows the scattering spectra of water in a phantom for various positions.

In the second measurement, the ball was filled with a solution of 50 mmol / l iodine in water (Ultravist®), and at 80 kV, 50 mA for 80 s, radiation was measured at each ball position (parameters: XR-100.CZT receiver (0.1 mm diaphragm )).

The obtained emission spectra for various positions are presented in Fig.5b. The installed polymethylmethacrylate plate attenuated the intensity of fluorescence radiation. It was confirmed that the intensity became less, the greater the thickness of the plate. However, even with the largest layer thickness of the ball (in the middle), the K-lines were still measurable.

In the third measurement, the ball was filled with a solution of 50 mmol / L gadolinium in water (Gadovist®), and at 80 kV, 50 mA for 80 s, radiation was measured at each ball position (parameters: XR-100.CZT receiver (0.1 mm diaphragm )).

The obtained emission spectra for various positions are presented in figv. Here, fluorescent radiation was also attenuated by the installed polymethyl methacrylate plate. Since the line K _α and K _β gadolinium matter, respectively 43.0 and 48.7 keV, in the presence polimetilmetakrilatovoy plate revealed significantly more intense fluorescence emission than in the previous case, the emission of iodine. So in this case, even with the largest thickness of the ball layer (in the middle), the K-line could still be measured.

Example 3

In another experiment, fluorescence intensities were determined and recorded depending on the position of the ball relative to the x-ray.

In the first measurement, the ball was filled with a solution of 50 mmol / l iodine in water (Ultravist®), and at 80 kV, 50 mA for 80 s, radiation was measured in each position of the ball.

On figa shows the dependence of the intensity of the fluorescent radiation on the position / displacement of the phantom in the selected energy ranges corresponding to the line K _α iodine at 28.6 keV and the line K _β iodine at 32.3 keV. In this figure, one can see the radiation intensity profile due to the shape of the ball.

According to the second measurement, the ball was filled with a solution of 50 mmol / L gadolinium in water (Gadovist®), and at 80 kV, 50 mA for 80 s, at each position of the ball, radiation was measured for each position.

6B shows the dependence of fluorescence intensity on the position / displacement of the phantom in selected energy ranges corresponding to K _α line of gadolinium at 43.0 keV K line _β Gadolin at 48.7 keV. In this figure, one can also see the radiation intensity profile due to the shape of the ball.

In the second measurement, the ball was filled with a solution of 25 mmol / L of iodine in water (Ultravist®) and 25 mmol / L of gadolinium in water (Gadovist®), and at 80 kV, 50 mA for 80 s, radiation was measured at each ball position.

Fig. 6c shows the dependence of the fluorescence intensity on the position / displacement of the phantom in the selected energy ranges corresponding to the K _α line of iodine at 28.7 keV, the K _β line of iodine at 32.3 keV, the K _α line of gadolinium at 43.0 keV and line K _β gadolinium at 48.7 keV. As can be seen from figv, the profile of the ball when directly applying the signal intensity as a function of position is reproduced unsatisfactorily. This is due to absorption on the side of excitation and intrinsic absorption on the side of radiation, which distort the image. Low concentrations of the radiopaque substance and corrections for the absorption of the primary ray and for the intrinsic absorption of the X-ray fluorescence lead to one-dimensional reproduction of the image of the ball.

Example 4

Fig. 7 shows sectional views of a previous X-ray fluorescence examples recorded by a computer tomograph. From left to right, images are shown for a ball filled with gadolinium, a mixture of gadolinium and iodine, iodine, clean water and air. A ball filled with air obviously gives the least attenuation of x-rays, followed by a ball filled with water. When using a ball filled with a solution of a 50 mmol / L X-ray contrast element, the attenuation of X-rays is more pronounced than when filled with water, quantitative analysis is possible by determining Hounsfield units (HU), but only using X-ray fluorescence images allows us to judge the filling of the ball with one or another chemical elements.

Claims (22)

1. An x-ray apparatus for forming an image of a test object containing at least one radiopaque chemical element by means of x-ray radiation passing through the test object and fluorescent x-ray radiation emitted by said object, comprising:
a) at least one x-ray source emitting essentially polychromatic x-ray radiation,
b) the first receiver or the first block of receivers, configured to determine the values of the first intensity of the x-ray radiation passing through the studied object,
C) a second receiver or a second block of receivers, configured to determine the values of the second intensity of the fluorescence x-ray emitted by the investigated object,
d) at least one correlation unit, configured to correlate the image intensities of the first intensity of the transmitted x-ray radiation with the values of the second intensity of the emitted fluorescence x-ray, and
d) at least one output device for displaying the object under study based on the signals of the image elements obtained by correlating the values of the first intensity with the values of the second intensity. 2. X-ray installation according to claim 1, characterized in that the correlation unit includes the following devices:
g1) a first storage device configured to store values of the first intensity of the passing x-ray radiation over the image elements,
g2) a second storage device configured to store the second intensity values of the emitted fluorescence x-ray radiation according to image elements,
g3) a computing device configured to correlate the elements of the image values of the first intensity of the transmitted x-ray radiation with the values of the second intensity of the emitted fluorescence x-ray. 3. X-ray installation according to one of the preceding paragraphs, characterized in that the second receiver or the second block of receivers is configured to determine the second intensity values with a resolution depending on the energy of the emitted fluorescent x-ray radiation. 4. The x-ray apparatus according to claim 1, characterized in that the second receiver or the second block of receivers makes it possible to distinguish the fluorescent x-ray radiation emitted by the x-ray contrast chemical element contained in the test object from another emitted x-ray radiation by its energy. 5. The x-ray apparatus according to claim 1, characterized in that the correlation of the first and second intensity values for the image elements is carried out after preliminary correction, taking into account the absorption of the incident x-ray radiation and / or the intrinsic absorption of the emitted fluorescence x-ray in the test object. 6. X-ray installation according to claim 1, characterized in that the first and / or second receiver is a receiver in the form of a flat matrix. 7. X-ray installation according to claim 1, characterized in that the first and / or second receiver is configured to register one individual image element and is mounted with the ability to move to register all image elements. 8. The x-ray installation according to claim 1, characterized in that for determining the emitted fluorescent x-ray radiation, a second receiver unit is provided, made with an x-ray optical module for energy selection. 9. The x-ray apparatus according to claim 1, characterized in that the first and / or second receiver comprises a matrix of detector sensitive elements, each of which is configured to register a corresponding image element, mounted to move to register all image elements. 10. The use of an x-ray apparatus according to one of claims 1 to 9 for forming an image of an object under study containing at least one radiopaque chemical element by means of x-ray radiation passing through the object to be studied and fluorescence x-ray radiation emitted by said object. 11. The application of claim 10, characterized in that the following operations are performed:
a) transillumination of the investigated object essentially polychromatic x-ray radiation,
b) determining the values of the first intensity of the x-ray radiation passing through the object under study,
c) determining the values of the second intensity of the fluorescent x-ray radiation emitted by the object under study,
d) correlation of the values of the first intensity of the transmitted x-ray radiation performed on the elements of the image with the values of the second intensity of the emitted fluorescence x-ray radiation, and
d) displaying the object under study based on the signals of the image elements obtained by correlating the values of the first intensity with the values of the second intensity. 12. The application of claim 10, characterized in that the values of the second intensity are measured with a resolution depending on the energy of the emitted fluorescent x-ray radiation. 13. The use according to claim 10, characterized in that the fluorescent x-ray radiation emitted by the x-ray contrast chemical element contained in the test object is distinguished by its energy from another emitted x-ray radiation. 14. The application of claim 10, characterized in that the correlation of the first and second intensity values for the image elements is carried out after preliminary correction, taking into account the absorption of the incident x-ray radiation and / or the intrinsic absorption of the emitted fluorescent x-ray radiation in the studied object. 15. The application of claim 10, characterized in that the first and second receivers are provided, or the first and second blocks of receivers. 16. The application of clause 15, wherein the first and / or second receiver is a plane matrix receiver. 17. The application of clause 15, wherein the first and / or second receiver is configured to register one single image element and moves to register all image elements. 18. The application of clause 15, wherein the first and / or second receiver contains a matrix of detector sensitive elements, each of which is configured to register the corresponding image element and moves to register all image elements. 19. The application of clause 15, characterized in that for determining the emitted fluorescent x-ray radiation, a second receiver unit is provided, made with an x-ray optical module for energy selection. 20. The use of claim 10, wherein the radiopaque chemical element is selected from the group consisting of bromine, iodine, lanthanides and bismuth. 21. The use of claim 10, characterized in that the test object is a mammal, and a radiopaque chemical element is introduced into the body of a mammal. 22. The use of claim 10 for graphical or quantitative representation of the test area in the test object containing at least one radiopaque chemical element.

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