WO2021162581A1

WO2021162581A1 - Dual-energy radiography method (variants)

Info

Publication number: WO2021162581A1
Application number: PCT/RU2021/000021
Authority: WO
Inventors: Заурбек Викторович БУЛАТОВ; Анатолий Рудольфович ДАБАГОВ; Игорь Сергеевич КОБЫЛКИН; Александр Валерьевич ПРОХОРОВ; Владимир Игоревич СПОРЫШ; Юрий Евгеньевич ШУНКОВ; Дмитрий Викторович ПОЗДНЯКОВ; Дмитрий Михайлович КАСЮК
Original assignee: Акционерное, Общество "Медицинские Технологии Лтд"
Priority date: 2020-02-11
Filing date: 2021-01-20
Publication date: 2021-08-19
Also published as: RU2738135C1

Abstract

The claimed group of inventions relates to medicine. A dual-energy radiography method comprises exposing a patient to X-ray radiation resulting from supplying two voltage pulses of different magnitudes to a source of X-ray radiation; obtaining two initial X-ray images; and constructing separate images of tissues having different linear attenuation coefficients. A high voltage pulse is supplied no sooner than the middle of a first exposure period, and a low voltage pulse is supplied simultaneously with the start of a second exposure period. The two initial images are aligned by correcting one of the images, for which purpose a sequence of compressions of the initial X-ray images is carried out. According to a first variant, a sequence of actions in which a displacement map is generated in the scale of the initial images from a combination of displacement vectors, and a current corrected image is obtained by displacing the previous corrected image according to the current displacement map, is carried out until a final corrected image is obtained. According to a second variant, a displacement map in the scale of the initial images is generated from a combination of displacement vectors and is subsequently refined until a final displacement map is obtained, and a corrected image is obtained by displacing the initial image according to the final displacement map.

Description

TWO-ENERGY X-RAY METHOD (VERSIONS)

The claimed group of inventions relates to the field of medical X-ray technology and can be used in examining patients with various diseases, including oncological diseases.

There is a known method of dual-energy radiography, which includes irradiating a patient with X-rays as a result of supplying two voltage pulses of different magnitude to the X-ray source, the first of which (low voltage) is supplied in the corresponding first exposure interval, and the second (high voltage) is supplied essentially at the same time as the start of the corresponding second exposure interval, obtaining two corresponding initial X-ray images and constructing from them separate images of tissues with different linear attenuation coefficients (see article Tong Xu et al. Dynamic dual-energy chest radiography: a potential tool for lung, tissue motion monitoring and kinetic study, Phys Med Biol, 2011, February 21, 56 (4), pp. 1191-1205).

The disadvantage of the known method consists in the manifestation of artifacts on the obtained separate images, caused both by the natural rhythmic movement of the patient during the diagnostic study (as a result of breathing and heartbeat), and by possible random changes in the position of his body, which reduces the accuracy of image interpretation.

The known method is adopted as the closest analogue of the claimed method for both options.

The technical problem solved by the claimed group of inventions consists in the creation of a dual-energy radiography method, which makes it possible to accurately interpret X-ray images, which increases the diagnostic value of the study.

At the same time, the technical result is achieved, which consists in the reduction of motion artifacts on the obtained separate images, both by reducing the influence of the probable movement of the patient during a diagnostic study, and by compensating for the influence of the residual effect of such movement on the information content of these images.

The technical problem is solved, and the specified technical result is achieved by implementing the method of dual-energy radiography, which includes irradiating a patient with X-ray radiation as a result of applying two voltage pulses of different magnitude to the X-ray source, obtaining two corresponding initial x-ray images and construction on their basis of separate images of tissues with different coefficients of linear attenuation. In the claimed method, not earlier than the middle of the first exposure interval, a high voltage pulse is applied, and essentially simultaneously with the beginning of the second exposure interval, a low voltage pulse is applied. Before constructing separate images of tissues with different coefficients of linear attenuation, two initial images are combined by correcting one of them, for which a sequence of compressing the original X-ray images is carried out by k _p times, where k _p is the current compression ratio, selected from the condition: ki kg ^ ^ k _p -i ^ k _p ^ k _{p + i} ... cr, finding the displacement vectors Ar _{P (} y _{) of} each pixel with coordinates i, j, where i = l ... Np, j = 1 ... Мр, a N _p xM _p - the size of each of the compressed images. According to the first embodiment of the invention, a sequence of formations is carried out from the set of said displacement vectors Ar _{P (ij) of the} displacement map Ar in the scale of the original images and obtaining the current corrected image by shifting the previous corrected image according to the current displacement map until the final corrected image is obtained.

According to the second embodiment of the invention, the formation of the aforementioned displacement vectors Ar _{P (} y> the displacement map Ar in the scale of the original images with its sequential refinement until the final displacement map is obtained and obtaining the corrected image by shifting the original image according to the final displacement map) is carried out.

FIG. 1 shows the time base of the pulses, in accordance with the closest analogue, and Ui <U2.

FIG. 2 shows the time base of pulses, in accordance with the present invention in both versions, with U2 <Ui.

The claimed method of dual-energy radiography is implemented as follows.

The patient is irradiated with X-ray radiation by applying to the X-ray source two pulses, high and low voltage, respectively, Ui and U2. The supply of pulses is carried out using a voltage generator included in the X-ray power supply device. The radiation emitted by the source is optionally additionally filtered by passing through a layer of selectively absorbing material. The radiation transmitted through the patient is recorded using an X-ray detector, optionally equipped with a raster filtering out scattered radiation.

The high voltage pulse Ui is applied not earlier than the middle of the first exposure interval (denoted in Figs. 1 and 2 as ti ^ b), i.e. not earlier than the point in time indicated in FIG. 2 as (ti + t ₂ ) / 2). Applying a high voltage pulse Ui of the previously mentioned time point unreasonably increases the total exposure time indicated in FIG. 2 as T ₂ , because, due to the high penetrating ability of high-energy radiation with a high degree of probability, repeatedly confirmed experimentally, the duration of the high-voltage pulse Ui turns out to be shorter than half the exposure interval.

The low voltage pulse U _{2 is} applied substantially simultaneously with the start of the second exposure interval (denoted in FIGS. 1 and 2 as t ₃ I ₄ ).

Preferably, "high voltage" means a voltage in the range of 100-150 kV, and "low voltage" means a voltage in the range of 50-100 kV. At the intervals indicated in FIG. 1 and 2, as t ₂ t ₃ and U ts, the signals accumulated by the X-ray detector during the exposure intervals ti 1 ₂ and t3 U are read, respectively.

The claimed sequence of impulses significantly reduces the total duration of exposure (from the value of ti in Fig. 1 to the value of m in Fig. 2), which, in turn, leads to a decrease in the influence of the probable movement of the patient during the diagnostic study, which is expressed, ultimately, in the reduction of motion artifacts on the obtained separate images.

Further, having received two initial X-ray images g and f, they are combined by correcting one of them, for example, f.

For this, according to the first embodiment, the following sequence of operations is performed:

1) compress images g and f by a factor of ki, resulting in images gi and fi;

2) find the displacement vector Atsu _{) of} each pixel gi relative to fi (this operation can be implemented by any suitable algorithm, in particular, one of the so-called “optical flow” algorithms, disclosed, for example, in Beauchemin SS, Barron JL “The computation of optical flow ”, ACM Journals, ACM Computing Surveys, Vol. 27, Ns 3, September 1995), while the set of all found vectors Atsu) forms a displacement map An; 3) the formation of the displacement map Ar in the scale of the original images is carried out as a result of the fact that the scale of the displacement map from An to Ar is changed by interpolation;

4) the subsequent corrected image f is obtained by shifting the image f according to Ar;

5) operations 1-4 are repeated at subsequent selected values of k _p (from the sequence ki, kg, ... kr, obeying the condition k _p > k _{p + i} ), the selection of which is carried out in advance (at the stage of debugging the declared alignment algorithm), based on requirements for the quality of separate images (for more details on the issue of determining the quality of X-ray images, see, for example, Martin CJ et al. "Measurement of image quality in diagnostic radiology", Appl Radiat Isot, 1999 Jan, 50 (1), pp. 21 -38), resulting in the final corrected image f.

According to the second embodiment, the following sequence of operations is performed.

1) compress images g and f by a factor of ki, resulting in images gi and fi;

2) find the displacement vector Aq) of each pixel gi relative to fi (this operation can be implemented by any suitable algorithm, in particular, one of the so-called "optical flow" algorithms, disclosed, for example, in the above-mentioned article by Beauchemin SS et al. ; in this case, the totality of all found vectors Arnd forms a displacement map An;

3) the formation of the displacement map Ar in the scale of the original images is carried out as a result of the fact that the scale of the displacement map from An to Ar is changed by interpolation;

4) the image f is shifted according to Ar, as a result of which an intermediate image f is obtained;

5) compress images g and f in kg times (kg <ki), as a result of which images g2 and f2 are obtained;

6) find the displacement vector Arg ₍ y _{) of} each pixel g2 relative to f2 (this operation can be implemented by any suitable algorithm, in particular, one of the so-called "optical flow" algorithms, disclosed, for example, in the above-mentioned article Beauchemin SS et al .; in this case, the set of all found vectors Agg) forms a displacement map Agg; 7) carry out the formation of the displacement map D (DG) in the scale of the original images as a result of the fact that by interpolation, the scale of the displacement map is changed from DG2 to D (DG);

8) refine the displacement map Dt by refining each of the displacement vectors Ary = Ary + A (Ary);

9) shifting the image f according to Dt, resulting in a corrected image f;

10) repeat operations 5-9 with subsequent selected values of k (from the sequence ki, kg, ... cr, obeying the condition k _p > k _{p + i} ) which are selected in advance (at the stage of debugging the described alignment algorithm), based on the requirements to the quality of the split images (disclosed, for example, in the aforementioned article by Martin CJ et al.), obtaining the final displacement map DG AND the corresponding image f, which is taken as the final corrected image.

On the basis of the obtained pair of images, consisting of the final corrected image and the original image, (f and g, respectively, according to the first embodiment, f and g, respectively, according to the second embodiment), separate images of tissues with different linear attenuation coefficients are constructed , by applying any suitable algorithm, for example, disclosed in the above-mentioned article by Tong Xu et al.

The described sequence of operations makes it possible to compensate for the influence of the residual effect of the probable movement of the patient during a diagnostic study on the information content of X-ray images, which also ultimately leads to a reduction in motion artifacts in the obtained separate images and, as a consequence, to an increase in the information content of X-ray images.

Claims

CLAIM

1. The method of dual-energy radiography, which includes irradiating a patient with X-ray radiation as a result of applying to the X-ray source two voltage pulses of different magnitude, the first of which is supplied in the corresponding first exposure interval, and the second is supplied essentially simultaneously with the beginning of the corresponding second exposure interval , obtaining two corresponding initial X-ray images and building on their basis separate images of tissues having different coefficients of linear attenuation, characterized in that no earlier than the middle of the first exposure interval, a high voltage pulse is applied, and, essentially, simultaneously with the beginning of the second exposure interval, a pulse is applied low voltage, while before constructing separate images of tissues with different linear attenuation coefficients, the two original images are combined by correcting one of them, for which a sequence of compressions is performed x-ray images in k _p times, where k _p is the current compression ratio, selected from: ki ^ ki ^ ^ k _p -i ^ k _p ^ k _{p + i} ... kr, finding the displacement vectors Ar _{P (} y _{) of} each pixel with coordinates i, j, where i = l ... Np, j = 1 ... M _p , a N _p xM _p is the size of each of the compressed image by shifting the previous corrected image according to the current displacement map until the final corrected image is obtained.

2. A method of dual-energy radiography, which includes irradiating a patient with X-rays by applying to the X-ray source two voltage pulses of different magnitude, the first of which is supplied in the corresponding first exposure interval, and the second is supplied essentially simultaneously with the beginning of the corresponding second exposure interval , obtaining two corresponding initial X-ray images and building on their basis separate images of tissues having different coefficients of linear attenuation, characterized in that no earlier than the middle of the first exposure interval, a high voltage pulse is applied, and, essentially, simultaneously with the beginning of the second exposure interval, a pulse is applied low voltage, while before building separate images of tissues with different coefficients of linear attenuation, produce combining two original images by correcting one of them, for which a sequence of compressions of the original X-ray images is carried out in k _p times, where k _p is the current compression ratio, selected from the condition: ki>kg>...>kp-i> k _p > k _{p + i} ... cr, finding the displacement vectors Dg _{P (} y _{) of} each pixel with coordinates i, j, where i = l ... Np, j = 1.. .Мр, a N _p xM _p - the size of each of the compressed images, the formation of a displacement map from them on the scale of the original images Dg with its sequential refinement until the final displacement map is obtained and the final corrected image is obtained by shifting the original image according to the final displacement map.