A method for controlling X-ray exposure in real time.

Abstract

To provide a method for the real-time control of exposure to an X-ray dose.SOLUTION: In the method, there are provided: a flat panel detector comprising a set of pixels organized into a matrix along rows and columns and configured so as to generate signals on the basis of the X-ray dose impinging on the detector; and a generator tube comprising a control unit for controlling the generator tube that is configured so as to control an emitted X-ray dose. The method comprises: a step 100 of exposing the flat panel detector to an X-ray dose emitted by the generator tube for generating an X-ray beam; a step 101 of repeatedly reading out at least one of the rows of pixels while the flat panel detector is exposed to the X-ray dose; a step 102 of determining a payload signal and a stray signal based on the signals from the readout of the at least one of the rows; and a step 103 of transmitting the payload signal to the control unit for controlling the generator tube.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to the field of radiography using digital flat panel detectors, and more specifically to a device for real-time control of radiation exposure levels. [Background technology]

[0002] To ensure optimal image quality for the radiologist while minimizing the dose received by the patient, exposure parameters (voltage, current, distance between source / patient / detector) must be adjusted. Optimal exposure parameters depend on the patient's size, the type of examination required, and the sensitivity characteristics of the X-ray imaging device (silver film, PSP plate, digital flat panel detector, etc.). These parameters are generally determined using system software based on instructions provided by the radiographer regarding the examination situation (patient size, type of image required). If these parameters are not correctly defined due to incorrect or inaccurate instructions or incorrect system calibration, there is a high risk of overexposure or underexposure of images. These risks include the risk of excessive X-ray exposure to the patient, either directly or due to the need for re-imaging.

[0003] Figure 1 schematically shows a conventional radiography assembly 50. The radiography assembly 50 consists of two elements: a generating tube 20 for generating an X-ray beam 22 and a flat panel detector 11 for radiographic imaging. The assembly is intended to take radiographic images of patients primarily in a hospital setting. Patients whose region of interest 40 is to be radiographed are positioned between the generating tube 20 for generating the X-ray beam 22 and the flat panel detector 11. Therefore, the two elements must be precisely positioned relative to each other so that all X-rays emitted by the generating tube 20 for generating the X-ray beam are captured by the flat panel detector 11. Next, we will discuss the precise alignment between the two elements. Alignment should be performed before X-rays are emitted from the generating tube 20 for generating the X-ray beam. Its purpose is to avoid overexposure of the patient by X-rays arriving from outside the detector. Several methods for aligning the two elements are known.

[0004] In addition to precisely aligning the X-ray beam with the flat-panel detector, it is crucial to control exposure parameters to ensure that a sufficient dose of X-rays is transmitted to guarantee good images, while preventing the patient from being overexposed.

[0005] To date, the problem of quantifying radiation exposure has been solved using one of the following solutions: - External AEC (Acronym for "Automatic Exposure Mechanism") equipment, such as an "ionization chamber" or "solid-state detector." This is separate from the imaging device and is a functional unit (e.g., an ionization chamber) for automatic dose control based on a hardware unit of "X-ray detector + current amplifier" connected to a control unit for controlling the X-ray generator. The detector is installed upstream of the imaging device and absorbs very small amounts of X-rays so as not to interfere with the image. The detector is divided into regions of interest (typically 3 or 5 regions) and can supply current to an amplifier for each region. The amplifier is connected to the detector on one end and to the control unit for controlling the X-ray generator on the other. The function of the amplifier is to supply a signal to the generator without delay corresponding to the updated total exposure. This signal allows the control unit for controlling the generator to control the generator and interrupt X-ray emission (the stop level is calibrated during system installation). - An internal AEC (Automatic Exposure Control) device that generally involves the use of signals received as images. There are two main types of solutions. In the first type of solution, the pixel matrix is ​​physically modified so that electrical signals, specifically those dedicated to signal measurement, are routed first to a charge-voltage converter and then to an analog-to-digital converter. In the second type of solution (disclosed, for example, in Japanese Patent Publication No. 5481053), the matrix is ​​not deductively modified, but there is no mention of the problem of stray signals from all illuminated pixels that are not within the region of interest defined for exposure adjustment. - This is known as a "pre-shot" device, which performs preliminary exposure at a very low dose. A "pre-image" of the patient is taken at a very low dose immediately before the "actual image." Real-time signals are not supplied to the system; the final parameters are identified and automatically placed into position by the system using a pre-image analysis algorithm.

[0006] The solution using an external AEC has three main drawbacks. It generally incorporates an X-ray absorbing detector upstream of the imaging device, which leads to a few percent increase in the dose delivered to the patient. In some cases, the external detector may be downstream of the imaging device, thereby distorting information about the amount of beam visible from the imaging device and thus requiring advanced calibration. Furthermore, this AEC solution can only be applied to fixed systems due to its bulk; the detector must be fixed to the imaging device, and cables are needed to route the signal to the amplifier. Therefore, it cannot be applied to capturing images on portable detectors outside of mobile radiography systems or their dedicated enclosures. Finally, the integration of this system is financially expensive; in a typical room with a table and support arm, two AEC units must be installed, each costing at least 500 euros.

[0007] Solutions using internal AEC have the following drawbacks: They cannot be implemented on existing products because they require modification of the pixel matrix. Although proposed in the literature, implementation is difficult due to technical problems with capacitive coupling between the illuminated pixels and the AEC signal readout sequence.

[0008] The pre-shot solution also has two main drawbacks. It requires perfect system calibration, meaning that a correlation must be established between parameters related to low doses (pre-images) and parameters related to normal doses (images). This correlation must also take into account the examination situation (patient size, type of image required). A time delay between the pre-image and the actual image is also assumed, which can reduce the application flow: waiting time, the impact of patient movement, etc. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Patent No. 5481053 [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention aims to overcome all or some of the above-mentioned problems by proposing a method for real-time control of X-ray dose exposure, which enables the assurance of an accurate dose level for a patient by displaying to the system in real time the grayscale level in the image currently being formed within the imaging device (digital flat panel detector, hereinafter referred to as the detector) for a predetermined area of ​​interest in the image. This method is based on the direct use of the detector panel without any modifications to analyze the signal level within the area of ​​interest of the image in real time. The method according to the present invention further proposes an algorithm-based method for solving the critical problem of coupling between the signal of interest (also called the payload signal) and stray signals, particularly uncollimated signals, emitted from the illuminated area. Finally, the method according to the present invention can be implemented without wiring connections, thereby enabling its implementation in a mobile radiography system or in a portable cassette mode within a radiography room. [Means for solving the problem]

[0011] For this purpose, one subject of the present invention is a method for controlling exposure in real time to an X-ray dose emitted by a generating tube for generating an X-ray beam and received by a detector including a flat panel detector, wherein the generating tube includes a control unit for controlling the generating tube, which is configured to control the amount of X-rays emitted by the generating tube, and the flat panel detector is a. A set of pixels organized into a matrix along rows and columns, and configured to generate a signal based on the amount of X-rays hitting the detector. b. A circuit configured to identify a payload signal based on signals from at least one of the rows. c. A transmitting module for sending payload signals to a control unit for controlling the generation tube. In a method including, - A step of exposing a flat panel detector to the amount of X-rays emitted by a generating tube for generating an X-ray beam, - A step of repeatedly reading out at least one row of pixels while the flat panel detector is exposed to an X-ray dose, - Steps to identify the payload signal and the stray signal based on the signal from at least one readout of the row, - Step of sending the payload signal to a control unit for controlling the generating tube. This method is characterized by including [a certain element].

[0012] Advantageously, the exposure control method according to the present invention further includes the step of adapting the amount of X-rays emitted by the generating tube based on a payload signal transmitted to a control unit for controlling the generating tube.

[0013] Advantageously, the step of repeatedly reading at least one row of pixels is, for each row of at least one row, - A step of reading the column without activating row Li to obtain the first signal An, - Step 1: Activate row Li and read out the column to obtain the second signal Bn. Includes.

[0014] Advantageously, the step of identifying the payload signal and the stray signal is, - A step to estimate the multiplication factor (FM') between the payload signal and the stray signal. - Based on the multiplication factor, the relationship is: DS' n =( A n +B n ) / (FM'+1) and S' n =cumulative(A+B) n / (FM'+1) Steps to estimate the payload signal using Includes.

[0015] Advantageously, the step of estimating the multiplication factor (FM’) between the payload signal and the drift signal comprises: - estimating the measured value A’ of the drift signal at the time of the second signal B n-1 , A n , A n+1 ) = (VA) n based on three consecutive samples of the first signal (A n (e.g., performed through interpolation by the following spline filter: A’ n = 1 / 16.(-1 10 7). n (VA) t ), n ) - performing linear regression on three consecutive points {(x i , y i ); i = 1 to 3} to obtain the proportionality coefficient FP, where ○ {x i} = [cumulative (A + B) n-2 , cumulative (A + B) n-1 , cumulative (A + B) n , ○ {y i} = [cumulative (B - A’) n-2 , cumulative (B - A’) n-1 , cumulative (B - A’) n , ○ cumulative (A) n is equal to A0 + A1 +... + A n , step - calculating the multiplication factor using the relationship FM’ = (FP) -1 -1 including.

[0016] In one embodiment, the step of transmitting the payload signal to the control unit for controlling the generating tube is performed through wired transmission.

[0017] In other embodiments, the step of transmitting the payload signal to the control unit for controlling the generating tube is performed through wireless transmission, preferably through RF transmission.

[0018] The present invention is a radiation assembly, A generating tube for generating an X-ray beam, comprising a control unit for controlling the generating tube, configured to control the amount of X-rays emitted by the generating tube. b. A detector including a flat panel detector, wherein the flat panel detector is i. A set of pixels (P(i,j)) organized into a matrix along rows (Li) and columns (Cj), and configured to generate a signal based on the amount of X-rays hitting the detector. ii. A circuit configured to identify the payload signal based on signals from several of the rows (Li), iii. A transmitting module that sends the payload signal to a control unit for controlling the generating tube. Includes detectors This also relates to radiation assemblies, including those containing radiation.

[0019] In one embodiment, the transmission module for sending the payload signal to a control unit for controlling the generating tube is a wired transmission module.

[0020] In other embodiments, the transmitting module for sending the payload signal to a control unit for controlling the generating tube is a wireless transmitting module, preferably an RF transmitting module.

[0021] The present invention will be better understood and further advantages will become apparent by reading the detailed description of one embodiment provided as an example, illustrated by the attached drawings. [Brief explanation of the drawing]

[0022] [Figure 1] A schematic diagram of a conventional radiation assembly is shown. [Figure 2] A conventional image detector is shown. [Figure 3] A schematic diagram of the steps for a method of controlling X-ray exposure in real time according to the present invention is shown. [Figure 4]A schematic diagram of the radiation assembly according to the present invention is shown. [Figure 5] The present invention demonstrates the principle of row positioning of a matrix of a readout-only detector and repeated readout. [Figure 6] The simulation results of exposure including a rapid increase in radiation level in the implementation of the method according to the present invention are shown. [Figure 7] The simulation results of exposure including a gradual increase in radiation exposure in the implementation of the method according to the present invention are shown. [Modes for carrying out the invention]

[0023] For clarity, these figures are not necessarily all at the same scale. Furthermore, the same elements in different figures share the same reference number.

[0024] In general, the present invention describes a conventional image detector, which typically includes a flat panel detector comprising a set of pixels organized in a matrix along rows and columns, a row addressing unit, a column readout unit, row conductors connecting pixel rows to the row addressing unit, and column conductors connecting pixel columns to the column readout unit. In relation to this patent application, it should be noted that the concepts of columns and rows are in relative terms only, and pixel rows and pixel columns are, for example, rows of pixels arranged perpendicular to each other, without limitation. Row conductors or column conductors are defined as being oriented parallel to the pixel rows or pixel columns.

[0025] Figure 1 schematically shows the conventional radiation assembly 50 already described in the introduction.

[0026] Figure 2 shows a conventional image detector 10. The image detector 10 includes a detector 11 formed on a first monolithic substrate 12. The first monolithic substrate 12 includes a set of pixels P(i,j) organized into a matrix 13 along rows Li and columns Cj. The matrix 13 may include several rows and columns that thus form pixels P(i,j). The matrix 13 forms a geometric region on the first substrate 12. Pixels are denoted by the general form P(i,j), where i and j are integer natural numbers indicating the row and column positions in the matrix 13, respectively. The set of pixels P(i,j) is configured to generate a signal based on radiation colliding with the detector 10. The detector 11 includes column conductors Yj, each connected to a pixel in a given column Cj. The column conductors Yj are intended to carry the signals generated by the pixels P(i,j). Similarly, the detector 11 includes row conductors Xi, each connected to a pixel in a given row Li. The matrix 13 of pixels P(i,j) includes columns Cj at even and odd positions. Similarly, the matrix 13 of pixels P(i,j) includes rows Li at even and odd positions. The detector 10 includes a contact pad 14 at the edge of the first substrate 12, outside the matrix 13 of pixels P(i,j). The contact pad 14 is connected to a column conductor Yj. The image detector 10 includes a row addressing unit 15, which is located near the first substrate 12 and connected to a row conductor Xi. Row addressing unit 15 is the name given to any assembly that includes at least one row addressing unit. The unit 15 may be incorporated into the first substrate 12 or into a different substrate, as shown in Figure 1. The row addressing unit 15 makes it possible to address each row Li of a pixel individually. The image detector 10 includes a column readout unit 16 formed on a second substrate 17, which is different from the first substrate 12. The column reading unit 16 includes a connection point 18 that connects the column reading unit 16 to the contact pad 14. The column reading unit 16 enables the reading of signals generated by the pixels of the row selected by the row addressing unit.

[0027] Pixel P(i,j) includes a photodiode Dp(i,j) associated with an electronic switch T(i,j). The photodiode Dp(i,j) can, of course, be replaced with any photosensitive element capable of generating an electrical signal when irradiated with photons. The pixel structure shown in Figure 2 is intentionally simplified, and more complex structures can be implemented within the scope of the present invention.

[0028] A switch T(i,j) formed by a transistor is connected to the row conductor Xi of row i by its gate Gi, to the column conductor Yj by its drain Dj, and to the cathode of the photodiode Dp(i,j) by its source Sij. All anodes of the photodiode Dp(i,j) are connected to a common potential, such as ground. The row addressing unit 15 includes an element that generates a signal to be incident on the row conductor Xi to drive the opening and closing of the transistor T(i,j). The column reading unit 16 may include an element that processes the signal received by the column conductor Yj. These may be amplifiers and / or analog-to-digital converters in particular.

[0029] The image detector 11 conventionally operates as follows: In the image acquisition phase, the photodiode Dp(i,j) is exposed to radiation, generating a charge at source Sij. The amount of charge at each source Sij depends on the intensity of the radiation received by the pixel P(i,j) under consideration. The image acquisition phase is followed by a readout phase, which is performed row by row. The signals incident on various row conductors Xi successively move to the active state, thereby the potential of each column conductor Yj continuously represents the amount of charge accumulated at various pixels P(i,j) in column j.

[0030] As mentioned above, the prior art requires modification of the pixel matrix to quantify the exposure dose. Furthermore, even without matrix modification, the prior art does not offer any solution to eliminate unavoidable stray signals.

[0031] Figure 3 shows a step-by-step diagram of a method for controlling X-ray dose exposure in real time according to the present invention. To better understand the elements, one may refer to Figure 2 unless the proposed solution requires modification of the pixel matrix.

[0032] The present invention relates to a method for controlling, in real time, exposure to an X-ray dose 22 emitted by a generating tube 20 for generating an X-ray beam and received by a detector 10. The detector 10 includes a flat panel detector 11, and the generating tube 20 includes a control unit 21 for controlling the generating tube 20, which is configured to control the amount of X-rays emitted by the generating tube 20. The flat panel detector 11 is - A set of pixels P(i,j) organized into a matrix 13 along row Li and column Cj, and configured to generate a signal based on the X-ray dose 22 that strikes the detector 10, - Circuit 30 configured to identify the payload signal based on the signal from at least one of row Li, - A transmission module 31 for sending the payload signal to a control unit for controlling the generation tube 20. Includes.

[0033] Circuit 30 is preferably an integrated circuit. However, other equivalent variations may be used. In other words, any device that identifies the payload signal based on a signal from one of the row Lis is suitable.

[0034] According to the present invention, the control method is - Step 100: Expose the flat panel detector 11 to the amount of X-rays 22 emitted by the generating tube 20 for generating the X-ray beam. - While the flat panel detector 11 is exposed to the X-ray dose 22, the step of repeatedly reading out at least one row Li of pixel P(i,j) (step 101), - Step 102: Identify the payload signal and the stray signal based on the signal from at least one readout of row Li. - Step 103: Send the payload signal to the control unit 21 for controlling the generating tube 20. Includes.

[0035] Step 101, which repeatedly reads out at least one row Li of pixel P(i,j) in matrix 13, is performed during exposure step 100. In other words, this readout step is performed when no row Li has been conventionally read out in the prior art. Specifically, in the conventional mode, the detector 10 does nothing during the exposure phase.

[0036] Furthermore, it should be noted that the readout step 101 is performed on one or more rows Li of the pixel matrix. These rows are present and contribute to the normal operation of the detector. In other words, it is not necessary to modify the pixel matrix to implement this particular step of reading out rows during X-ray exposure.

[0037] To obtain the fastest possible read step 101, it is possible to open all the rows provided in this step 101 simultaneously, which has the disadvantageous effect of combining all of the region of interest into a single information item. It is also possible to activate only one or more rows corresponding to a given region of interest.

[0038] Exposure to a pixel in exposure step 100 generates a charge in the column Cj outside pixel P(i,j) because capacitive coupling connects each column of the matrix and all pixels (transistors and photodiodes) attached to that column. Therefore, the readout of the currently exposed (step 100) pixel does not represent the level in the image in the same way as the readout after exposure step 100 is completed, i.e., a stray signal from the charge generated in the column through coupling is added. This stray signal can be substantial for each column, since coupling originates from all illuminated pixels in that column. Since the pixel of interest is generally below the patient, and many other pixels are illuminated, if the direct beam of light is illuminated without attenuation (low collimation), the stray signal can be up to 100 times the value of the payload signal. Therefore, it is essential to consider this stray signal in step 102, when identifying the (payload and stray) signals.

[0039] Step 101 involves repeatedly reading out at least one row Li of a pixel in order to identify the payload signal and the stray signal, for each row Li of at least one row Li, - Read out column Cj without activating row Li, and the first signal A n Step to obtain (Step 110), - Activate row Li and read out column Cj, then the second signal B n Step to obtain (Step 111) Includes.

[0040] Therefore, a double read is performed for each read-only row in step 101, i.e., the column is first read without activating the row (step 110), and then sample A for the nth double read. n This is obtained, and then the row is activated and the column is read again (step 111), sample B of the nth double read nThis is obtained. This double readout allows us to subtract the stray effect. These double readouts are repeated until the end of the window XRW (XRW is an abbreviation for the term X-ray window, i.e., the period before the readout phase during which the detector can receive X-photons and convert them into charge). Double readout A n and B n Based on the information obtained, the actual signal levels in the image can be estimated.

[0041] Simple subtraction from double reading (B n -A n ) alone does not provide the payload signal DS n A decisive increase could not be obtained because the dose flux was not constant throughout the exposure (step 100). In the initial phase of increasing the dose flux, the first non-zero readout A of the column n0 The level is when that column is read B n0 It is lower than when read at that time. In other words, read B n0 This is signal A n0 It contains more stray signals. Therefore, B n0 -A n0 The subtraction includes some stray signal, resulting in an increased payload signal DS. n0 This is overestimated. In contrast, when the line flux decreases, for example, after obtaining the maximum exposure ("overshoot"), signal A n1 B n1 Larger than the stray signal contained in B, therefore B n1 -A n1 In subtraction, the payload signal DS n1 Changes in this area are underestimated, or negative results are obtained.

[0042] To solve this problem, the solution proposed by the present invention assumes that the minimum exposure time is short, for example, about 1 ms, or slightly less than 0.8 ms, and that the constraint (CP constraint) that the electrical shutdown signal must reach the control unit for controlling the generator shortly after a specific signal level in the imaging device has been effectively realized, for example, less than 0.1 ms, is removed within this time. This means that a buffer delay time of 0.8 ms is obtained for analysis at the start of exposure, and after this delay time has elapsed, the constraint (CP) is again met. With respect to hazard analysis, this means that the responsibility of not overexposing the patient, which still lies with the radiation system, is mainly based on the selection of normal parameters during this initial delay time of 0.8 ms.

[0043] In the following, we assume that the main assumption (HP) is valid, which, accordingly, has a delay of 0.8 ms from the start of exposure until the point in time when the algorithm must definitively meet the constraints (CP).

[0044] Therefore, this delay time (HP) is used to reliably estimate the multiplication factor FM' between the payload signal and the stray signal for the current exposure. Specifically, this factor remains constant throughout the exposure regardless of the temporal profile of the dose flux, because it is determined entirely by the relative exposure configuration between the pixel of interest in a column and the other pixels in that column (for each column). If multiple columns are grouped together in each readout to enhance signal quality, the multiplication factor applied to this set of columns also remains constant.

[0045] For this purpose, step 102, which identifies the payload signal and the stray signal, - Step 120: Estimate the multiplication factor (FM') between the payload signal and the stray signal. - Based on the multiplication factor, the relationship is: DS' n =( A n +B n ) / (FM'+1) and S' n=cumulative(A+B) n / (FM'+1) Step 121: Estimate the payload signal using [the specified method / tool]. Includes.

[0046] More precisely, step 120, which estimates the multiplication factor FM' between the payload signal and the stray signal, - Three consecutive samples of the first signal (A n-1 ,A n ,A n+1 )=(VA) n Based on this, the second signal B n Measured value A' of the stray signal at that point in time n Step to estimate (Step 122), - Linear regression on three consecutive points {(x i ,y i Step 123 involves performing );i=1~3} to obtain the proportionality constant FP, where, ○{x i}=[cumulative(A+B) n-2 ,cumulative(A+B) n-1 ,cumulative(A+B) n ] and ○{y i}=[cumulative(B-A') n-2 ,cumulative(B-A') n-1 ,cumulative(B-A') n ] and ○Cumulative (A) n is A0 + A1 + ... + A n Equivalent to, step (step 123), - Relationship FM' = (FP) -1 Step 124: Calculate the multiplication factor using -1. Includes.

[0047] Step 122 can be performed, for example, through the following spline filter interpolation method: A' n = 1 / 16. (-1 10 7). t (VA) n .

[0048] This estimate is good when the pulse waveform is well approximated by a polynomial between the three measurement points, as is generally the case. Other filters, such as arithmetic means (0 0.5 0.5), are also acceptable. t We also conducted test (A).

[0049] Estimated value A' n The measured value of the stray signal is B n It corresponds to what it will be like at that point.

[0050] Linear regression step 123 is cumulative (A+B) n The amount is basically B n The multiplication factor is proportional to the accumulated signal level over time, and is equal to FM'+1, which is the stray signal (FM'*DS n ) and payload signal (1*DS n This is justified by the fact that it corresponds to the accumulation of B. n The stray signal added at this point is A' n This is estimated solely by the pulse, which can lead to a shift in the reproduced signal relative to the actual signal if there is a sudden change in the pulse.

[0051] The idea of ​​a three-point regression makes it possible to offset this shift, provided that there are periods of less "fluctuations" in the pulse that persist over several double-readout periods (i.e., there are no line bundles that should ideally remain constant).

[0052] Therefore, using the proportionality coefficient FP obtained by the linear regression described above, the relationship is: FM'+1=(FP) -1 , in other words, FM'=(FP) -1 Using -1, it becomes possible to obtain an estimated multiplication factor FM'.

[0053] The correlation coefficient CC of the regression is sufficiently close to 1 (for example, |1-CC|<10 -5 If it is considered to be ), then FM can be considered to be robustly estimated by FM'.

[0054] When the correlation coefficient CC is not close enough to 1, steps 122 and 123 are repeated by changing from n to n + 1 while verifying that the delay time obtained by the main hypothesis (HP) is not exceeded.

[0055] When the multiplication factor is estimated with sufficient confidence, B n the estimated value DS’ of the level of the payload signal DS n added each time at B n can be obtained using the formula DS’ n =(A n +B n ) / (FM’ + 1).

[0056] Also, thereby, thus S’ n = cumulative (A + B) n / (FM’ + 1) is also obtained.

[0057] This payload signal is transmitted to the control unit that controls the generating tube.

[0058] Finally, the exposure control method according to the invention advantageously includes step 104 of adapting the X-ray dose 22 emitted by the generating tube 20 based on the payload signal transmitted to the control unit 21 for controlling the generating tube 20. Thereby, thus, it is ensured that the patient receives the correct X-ray dose in order to obtain a high-quality image without causing unnecessary overexposure.

[0059] The present invention provides a solution based on an algorithm for correcting the capacitive coupling between pixels and columns.

[0060] <00003-seven]] These steps have shown good results in simulations (Figures 2 and 3). The situation is more favorable in the case of short pulses because the dose rate is higher and each sample has a good signal-to-noise ratio. This is good news because the critical situation seen from the client tends to be the situation using short pulses.

[0061] On the other hand, in the case of a long pulse (several tens of ms), the dose rate can be low, and the signal-to-noise ratio deteriorates for each readout. To overcome this problem, apart from adding multiple columns (averaging effect), it is proposed to define a longer readout time increment using the information on the duration of the X-ray window (XRW) passed to the detector within the frame request, while simultaneously maintaining the objective of making the estimated signal error less than 10%.

[0062] Step 103 of transmitting the payload signal to the control unit for controlling the generating tube can be performed through wired transmission or wireless transmission, preferably through RF transmission. Generally, it is necessary to have high-speed transmission with minimal latency and good control. Therefore, although Wi-Fi and Bluetooth links are applicable with respect to the present invention, they are less suitable.

[0063] The information is preferably transmitted in real time. The information regarding the signal level at time B obtained in step 102 n should be transmitted to the control unit 21 for controlling the generating tube 20 with a delay of less than 0.1 ms with respect to time B. n The algorithm for performing step 102 is implemented in an FPGA integrated circuit. Since its principle does not require a large number of calculations, most of this constraint regarding the delay relates to step 103 of transmitting the information from the integrated circuit to the control unit. In the case of a wired link, there are particularly no problems. In the case of an RF wireless link, it becomes much more difficult.

[0064] If the delay associated with the RF link is longer than 0.1 ms, it is possible to contemplate the step of extrapolating the information supplied in step 102, in which case it is conditioned that it is timestamped and the transmitter (transmission module) and receiver (control unit) elements are pre-synchronized.

[0065] FIG. 4 schematically shows a radiation assembly 51 according to the present invention. The radiation assembly 51 - A generating tube 20 for generating an X-ray beam, and including a control unit 21 for controlling the generating tube 20, configured to control the amount of X-rays 22 emitted by the generating tube 20. - A detector 10 including a flat panel detector 11, wherein the flat panel detector 11 is ○ A set of pixels P(i,j) organized into a matrix 13 along rows Li and columns Cj (similar to the detector shown in Figure 2), and configured to generate a signal based on the X-ray dose 22 that strikes the detector 10. Circuit 30 configured to identify the payload signal based on signals from several rows of Li, ○Transmission module 31 for transmitting the payload signal to the control unit 21 for controlling the generation tube 20 Detector 10 Includes.

[0066] Circuit 30 may be an integrated circuit. The integrated circuit may be any circuit suitable for performing calculations. For example, but not limited to, it may be an FPGA (an abbreviation for "Field-Programmable Gate Array," which stands for Programmable Logic Array). The integrated circuit performs the step of analyzing data in a dedicated row to extract signal level information at a given point in time. The information is routed directly via a wired link or via a wireless link (RF option) to a control unit for controlling the generator.

[0067] The transmitting module 31 for transmitting the payload signal to the control unit 21 for controlling the generator tube 20 may be a wired transmitting module or a wireless transmitting module, preferably an RF transmitting module. It transmits signal information at a given time to the receiver module of the generator tube. The receiver module receives signal level information at a given time, converts it into an electrical signal, and supplies it to the control unit for controlling the X-ray generator.

[0068] Figure 5 illustrates the principle of row positioning and repeated readout of the matrix of a readout-only detector according to the present invention. Only the rows relevant to the repeated readout step 101 are shown (top of the figure). These are existing rows already present in the detector matrix. Measurements are indicated by indicators to illustrate possible exemplary embodiments. In this figure, three rows are used in step 101. There may be only one row, two rows, or more. These rows are read out as quickly and continuously as possible during the X-ray window 60 (reference number 61 represents the X-ray emission window). To confirm representative values, it is essential to read out columns without activating the rows (step 110) and then read out columns with the rows activated. This means that during the X-ray window, step 110 and then step 111 (i.e., rows are activated and columns are read out) are performed alternately.

[0069] Figure 6 shows the simulation results of exposure including a sharp increase in radiation levels in an implementation of the method according to the present invention.

[0070] Figure 7 shows the simulation results of exposure including a gradual increase in radiation exposure in an implementation of the method according to the present invention.

[0071] In these two figures, you can see the simulated pulse waveform in the upper right. Cumulative (AB) n Cumulative (B-A') according to the calculation n The graph is shown in the lower left. In the lower right, you can see the verification results of the calculation of the estimated value according to the elapsed time, and within that, the actual payload signal (represented by a solid line) and the cumulative value (A+B) which is non-zero as long as CC is sufficiently close to 1. n The payload signal estimated using / (FM'+1) (represented by a triangle) and the cumulative value of the estimate (B-A'). n There is a way to determine what it will look like (shown by a dashed line).

[0072] In Figure 6, Sample A n and B nThis is simulated with a multiplication factor FM=100. It can be seen that linear regression can function at an early stage, at the second triple point.

[0073] In Figure 7, Sample A n and B n This is simulated with a multiplication factor FM=10.

[0074] These two figures demonstrate the effectiveness of the proposed solution to the capacitive coupling problem.

[0075] The present invention proposes a method for controlling exposure in real time, which has the advantage of being implementable without any physical modification or specific adjustment of the photodiode matrix (high-speed readout of an existing dedicated row of the panel during exposure). The signal level within the region of interest in the image is analyzed in real time. Step 102 solves the significant problem of coupling between the signal of interest and stray signals emanating from areas illuminated without collimation.

[0076] Finally, this method is compatible with transmission without wired connections, expanding the possibilities for use in mobile radiography or in portable cassette mode in radiology rooms.

[0077] The proposed solution provides real-time signal levels. This involves analyzing the signal level in the region of interest of an image in real time using the detector panel directly without any modification. Furthermore, the proposed solution describes an algorithm-based method for resolving the critical problem of coupling between the signal of interest and stray signals emanating from areas illuminated without collimation. Finally, the proposed solution can be implemented without wired connections, thereby enabling execution on mobile radiation systems or in portable cassette mode in radiation rooms. [Explanation of Symbols]

[0078] 10 detectors 11 Flat panel detector 12 First circuit board 13 Queues 14 Contact pads 15-line addressing unit 16-column reading unit 17. Second circuit board 18 connection points 20 Generating tube 21 Control Unit 22 X-ray dose 30 circuits 31 Transmitter Module 40 Areas of Interest 50 Radiography Assembly 51 Radiation Assembly 60 X-ray windows 61 X-ray emission window 100 exposure steps 101 Reading Step 102 steps 103 steps 104 steps 110 steps 111 Steps 120 steps 121 steps 122 steps 123 Linear Regression Step 124 steps

Claims

1. A method for controlling exposure in real time to the amount of X-rays emitted by a generating tube (20) for generating an X-ray beam and received by a detector (10) including a flat panel detector (11), wherein the generating tube (20) includes a control unit (21) for controlling the generating tube (20) and configured to control the amount of X-rays emitted by the generating tube (20), and the flat panel detector (11) is a. A set of pixels (P(i,j)) organized into a matrix (13) along rows (Li) and columns (Cj), and configured to generate a signal based on the X-ray dose (22) that strikes the detector (10), b. A circuit (30) configured to identify a payload signal based on the signals from at least one of the rows (Li), c. A transmitting module (31) for transmitting the payload signal to the control unit for controlling the generation tube (20). The control method includes, - Step (100) of exposing the flat panel detector (11) to the amount of X-rays emitted by the generating tube (20) for generating an X-ray beam, - While the flat panel detector (11) is exposed to the X-ray dose, step (101) repeatedly reads out at least one row (Li) of the pixel (P(i,j)), - Step (102) of identifying the payload signal and the stray signal based on the signal from the at least one readout of the row (Li), - Step (103) of transmitting the payload signal to the control unit (21) for controlling the generating tube (20) In a method including, the step (101) of repeatedly reading at least one row (Li) of the pixels, - Step (110) of reading the column (Cj) without activating the row Li to obtain the first signal An. - Step (111) to activate row Li and read column (Cj) to obtain the second signal Bn. The step (102) of including and identifying the payload signal and the stray signal is, - Step (120) of estimating the multiplication coefficient (FM') between the payload signal and the stray signal, - Based on the multiplication factor mentioned above, the relationship is: DS' ｎ = (A ｎ + B ｎ ) / (FM' + 1) and S' ｎ = cumulative(A + B) ｎ / (FM' + 1) (where DS' ｎ is the level of the payload signal, S' ｎ is the payload signal, and cumulative(A + B) ｎ is the signal level accumulated over time of B ｎ ((A0 + B0) + (A1 + B1) + (A2 + B2) ··· + (An + Bn))) (121) Step of estimating the payload signal using The step (120) of including and estimating the multiplication factor (FM') between the payload signal and the stray signal is, - Three consecutive samples of the first signal (A ｎ－１ , A ｎ , A ｎ＋１ ) = (VA) ｎ Based on the above, the second signal B ｎ The measured value A' of the stray signal at that point in time. ｎ Step (122) to estimate, - Linear regression {(x)} at three consecutive points ｉ , y ｉ Step (123) is to obtain the proportionality constant FP by performing the procedure i = 1 to 3, where, ○{x ｉ }=[cumulative (A+B) ｎ－２ , cumulative (A+B) ｎ－１ , cumulative (A+B) ｎ ] and ○ { ｉ }=[cumulative (BA') ｎ－２ , cumulative (B-A') ｎ－１ , cumulative (B-A') ｎ ] and ○Cumulative (A) ｎ is, A ０ +A １ +... +A ｎ Equivalent to step (123), - Relationship FM' = (FP) －１ Step (124) to calculate the multiplication factor using -1 A method characterized by including [a certain element].

2. A method for controlling exposure according to claim 1, further comprising the step (104) of adapting the amount of X-rays emitted by the generating tube (20) based on the payload signal transmitted to the control unit (21) for controlling the generating tube (20).

3. The method for controlling exposure according to claim 1 or 2, wherein the step (103) of transmitting the payload signal to the control unit for controlling the generating tube is performed via wired transmission.

4. The method for controlling exposure according to claim 1 or 2, wherein the step (103) of transmitting the payload signal to the control unit for controlling the generating tube is performed via wireless transmission.

5. The method for controlling exposure according to claim 4, wherein the wireless transmission is RF transmission.

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