Automatic brightness control method and device of x-ray flat panel detector and storage medium

Abstract

The application discloses an automatic brightness control method, device and storage medium of an X-ray flat panel detector, and the method comprises the following steps: setting a final target brightness B, calculating photosensitive sensitivity according to a multi-pixel mode; setting a reduction coefficient c, and adjusting B to Bc; according to c, the number of combined pixels A in the multi-pixel mode, the sensitivity coefficient, and the exposure time T in the exposure mode corresponding to B, calculating the exposure time Ta in the automatic brightness adjustment process to reach the indirect target brightness Bc; exposing and collecting an image with Ta and obtaining the image brightness; if Bc is reached, exposing and collecting an image in a single-pixel mode and with the exposure time T under the same tube current and tube voltage parameters, and if Bc is not reached, adjusting the tube current and the tube voltage to continue exposing and collecting an image with the exposure time Ta and obtaining the image brightness. In the brightness adjustment process, the application sets a reduced indirect target brightness, reduces the exposure time in combination with the multi-pixel mode, and reduces the exposure dose in the automatic brightness control.

Description

Technical Field

[0001] This invention relates to the field of X-ray machine technology, specifically to an automatic brightness control method, device, and storage medium for an X-ray flat panel detector. Background Technology

[0002] Automatic brightness control of fluoroscopic images is a specialized technology equipped in X-ray machines. When the patient's body shape and position are uncertain, the X-ray machine automatically adjusts the X-ray dose based on the brightness of the exposure image to achieve optimal image quality. To maintain the stability of the image brightness from the flat panel detector, automatic brightness control of fluoroscopic images is essential. It helps ensure X-ray imaging quality, improves clinical diagnostic efficiency, and greatly facilitates clinical operations.

[0003] However, during automatic brightness adjustment, although there are various brightness adjustment algorithms, multiple exposures and adjustments to tube current and tube voltage are necessary to meet the required image brightness. During this adjustment process, these radiations can also be harmful to patients. How to reduce the exposure dose has always been the research and design goal of X-ray exposure. Summary of the Invention

[0004] In this application, a target value for reducing brightness is set during automatic brightness adjustment, and the flat panel detector operates in multi-pixel mode. This reduces the single exposure time during automatic brightness control, thereby reducing the exposure dose during automatic brightness control. After finding suitable exposure parameters through the automatic brightness adjustment algorithm, the flat panel detector is set back to the single-pixel mode and exposure time corresponding to the final target brightness B. The resulting image is the exposure image with the set final target brightness.

[0005] An automatic brightness control method for an X-ray flat panel detector includes the following steps:

[0006] Step S1: Set the final target brightness B, set the flat panel detector to multi-pixel mode, the combined pixel number of the multi-pixel mode is A, and calculate the photosensitivity of the flat panel detector in multi-pixel mode.

[0007] Step S2: Set the brightness reduction factor c, where c is a positive number less than 1, and adjust the final target brightness B to the indirect target brightness Bc;

[0008] Step S3: Based on the reduction factor c, the number of combined pixels A in the multi-pixel mode, the sensitivity factor Δ, and the exposure time T of each frame in the exposure mode corresponding to the final target brightness B, calculate the exposure time Ta of each frame in the automatic brightness adjustment process to achieve the indirect target brightness Bc.

[0009] Step S4: Expose the acquired image using the exposure time Ta and obtain the image brightness;

[0010] Step S5: Determine whether the image brightness reaches the indirect target brightness Bc. If it does, record the exposure tube current and tube voltage parameters, adjust the flat panel detector to single-pixel mode, set the exposure time to T, and use the recorded exposure tube current and tube voltage parameters to expose and acquire the image. If it does not reach the target brightness, adjust the tube current and tube voltage and return to step S4.

[0011] Optional, A is an integer greater than or equal to 2.

[0012] Optionally, the photosensitivity in multi-pixel mode is Δ*A, where the sensitivity coefficient Δ is a number greater than 0.5 and less than or equal to 1.

[0013] Optionally, the reduction factor c is set according to the signal-to-noise ratio and grayscale resolution. The signal-to-noise ratio should be greater than 10, and the grayscale resolution should make each level of pixels in the acquired image distinguishable.

[0014] Optionally, the image acquired by the flat panel detector in the absence of X-rays is the noisy image of the flat panel. The signal-to-noise ratio of the X-ray image is obtained by dividing the indirect target brightness Bc of the exposed image by the brightness of the noisy image.

[0015] Optionally, the exposure time Ta of each frame in the automatic brightness adjustment process to achieve the indirect target brightness Bc is calculated based on the reduction factor c, the number of combined pixels A in multi-pixel mode, the sensitivity factor Δ, and the exposure time T of each frame in the exposure mode corresponding to the final target brightness B. The formula is as follows:

[0016] Ta = (T*c) / (A*Δ).

[0017] This application also provides an electronic device, including:

[0018] At least one processor; and,

[0019] A memory communicatively connected to the at least one processor; wherein,

[0020] The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the automatic brightness control method for the X-ray flat panel detector as described above.

[0021] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the automatic brightness control method for an X-ray flat panel detector as described above.

[0022] In the automatic brightness control process, this application reduces the exposure time by lowering the target brightness value and adopting a multi-pixel mode, thereby reducing the exposure dose during the automatic brightness control process, reducing X-ray damage to patients or operators, and correspondingly reducing the exposure power and the wear and tear on the X-ray source tube. Attached Figure Description

[0023] Figure 1 This is a flowchart of an automatic brightness control method for an X-ray flat panel detector using a 2-pixel mode, according to an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of single-pixel mode and multi-pixel mode according to an embodiment of the present invention.

[0025] Figure 3 A comparative diagram of exposure times in embodiments of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Figure 1 This is a flowchart of an automatic brightness control method for an X-ray flat panel detector using a 2-pixel mode. See below for reference. Figure 1 The automatic brightness control method for the X-ray flat panel detector in this embodiment includes the following steps:

[0028] Step S1: Set the final target brightness B, set the flat panel detector to multi-pixel mode (binning mode), where the number of combined pixels in this mode is A, and A is an integer greater than or equal to 2. Calculate the photosensitivity of the flat panel detector in multi-pixel mode. The applicant discovered that one factor related to image brightness is the pixel mode of the flat panel detector, which has both multi-pixel and single-pixel modes. For example... Figure 2In this model, both 2-pixel mode and 2*2-pixel mode are multi-pixel modes. In 2-pixel mode, two pixels are combined into one pixel. In this mode, due to the increased pixel area of ​​the X-ray detector, the image brightness generated by exposure integration is higher for the same exposure dose. Theoretically, the image brightness of 2*2 mode is four times that of single-pixel mode (i.e., one pixel). Therefore, multi-pixel mode can be considered a factor in image brightness adjustment. However, although the photosensitive area increases by a multiple of A, due to differences in the integrating circuit and its mode model, the photosensitivity of the flat panel detector does not increase with a multiple of A. Instead, it is also affected by a sensitivity coefficient, which is a decimal greater than 0.5 and less than or equal to 1. Let this sensitivity coefficient be Δ. Then, compared to single-pixel mode, the photosensitivity of multi-pixel mode is Δ*A. That is, the sensitivity of multi-pixel mode compared to single-pixel mode is Δ*A. Since A≥2, Δ>0.5, then Δ*A>1. Therefore, multi-pixel mode has better photosensitivity than single-pixel mode.

[0029] Step S2: Set the brightness reduction factor c, where c is a positive number less than 1, and adjust the final target brightness B to the indirect target brightness Bc.

[0030] The reduction factor *c* is determined by the signal-to-noise ratio (SNR) of the flat panel detector and the grayscale resolution during automatic brightness control. Currently, the grayscale resolution of flat panel detectors is generally 16 bits, providing grayscale values ​​from 0 to 65535. This high grayscale resolution is sufficient to provide adequate brightness for grayscale recognition. The value of *c* can be adjusted for flat panels with different SNRs and grayscale resolutions, ensuring that the panel noise does not affect automatic brightness adjustment and that the grayscale resolution meets the requirements for automatic brightness adjustment. For example, it can be set to different values ​​such as 0.5 or 0.7. This value can be obtained by experimentally acquiring images to distinguish pixels at different levels in the acquired images and analyzing the impact of the SNR on the adjustment.

[0031] The flat panel detector acquires an image in the absence of X-rays; this image is the noisy image of the flat panel. The signal-to-noise ratio (SNR) of the X-ray image can be approximated by dividing the brightness of the exposed image by the brightness of the noisy image. As mentioned earlier, in this embodiment, the indirect target brightness value for automatic brightness adjustment is Bc, and the noise brightness is Bn. Therefore, Bc / Bn can be approximated as the SNR at the target brightness state. It can be seen that the larger Bc is, the higher the image SNR and the smaller the impact of noise on accuracy, but the larger the required X-ray dose. In this embodiment, the target is that the noise impact is less than 10%, so Bc / Bn should be greater than 10, that is, the SNR should be greater than 10.

[0032] Step S3: Based on the reduction factor c, the number of combined pixels A in multi-pixel mode, the sensitivity factor Δ, and the exposure time T of each frame in the exposure mode corresponding to the final target brightness B, calculate the exposure time Ta of each frame in the automatic brightness adjustment process to achieve the indirect target brightness Bc. The specific formula is as follows:

[0033] Ta=(T*c) / (A*Δ). (1)

[0034] Figure 3 This is a diagram illustrating exposure time and dose, showing the difference in exposure time and dose for each frame. The area formed by the pulses represents the dose. From Figure 3 As can be seen, reducing the exposure time can reduce the X-ray dose.

[0035] Based on the physical characteristics of X-ray flat panel detectors, the image brightness of each frame is directly proportional to the X-ray dose of the corresponding exposure frame, while the X-ray dose of a single frame is directly proportional to the exposure time of that frame and the X-ray tube current. The tube current is determined by the temperature of the cathode filament. Changing the filament temperature requires a considerable amount of time; generally, it takes more than 500ms to change the filament temperature to achieve the desired tube current, which negatively impacts the user experience. Therefore, adjusting the tube current is not within the scope of this embodiment. This embodiment recalculates the exposure time Ta based on the exposure time T reduced by a factor of c, combined with the photosensitivity.

[0036] Step S4: Expose the acquired image using the exposure time Ta and obtain the image brightness.

[0037] Step S5: Determine whether the image brightness reaches the indirect target brightness value Bc. If it does, record the exposure tube current and tube voltage parameters, adjust the flat panel detector to single-pixel mode, set the exposure time to T, and use the recorded exposure tube current and tube voltage parameters to expose and acquire the image. If the indirect target brightness value Bc is not reached, adjust the exposure dose (adjust the tube current and tube voltage) and return to step S4.

[0038] In the automatic brightness adjustment process, the exposure time is Ta. In multi-pixel mode, if the tube current and tube voltage parameters with the exposure time Ta satisfy the indirect target brightness Bc, then when switching to single-pixel mode, the exposure time T is performed with the same tube current and tube voltage parameters, and the image brightness will satisfy the final target brightness B according to the relationship in Formula 1 above.

[0039] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications are all within the protection scope of the claims of the present invention.

Claims

1. An automatic brightness control method for an X-ray flat panel detector, characterized in that, Includes the following steps: Step S1: Set the final target brightness B, set the flat panel detector to multi-pixel mode, the combined pixel number of the multi-pixel mode is A, and calculate the photosensitivity of the flat panel detector in multi-pixel mode. Step S2: Set the brightness reduction factor c, where c is a positive number less than 1. Adjust the final target brightness B to the indirect target brightness Bc using the brightness reduction factor c. Step S3: Based on the reduction factor c, the number of combined pixels A in the multi-pixel mode, the sensitivity factor Δ, and the exposure time T of each frame in the exposure mode corresponding to the final target brightness B, calculate the exposure time Ta of each frame in the automatic brightness adjustment process to achieve the indirect target brightness Bc. Step S4: Expose the acquired image using the exposure time Ta and obtain the image brightness; Step S5: Determine whether the image brightness reaches the indirect target brightness Bc. If it does, record the exposure tube current and voltage parameters, adjust the flat panel detector to single-pixel mode, set the exposure time to T, and perform image acquisition using the recorded exposure tube current and voltage parameters. If the target brightness is not reached, adjust the tube current and voltage and return to step S4. A is an integer greater than or equal to 2. The photosensitivity in multi-pixel mode is Δ*A, where the sensitivity coefficient Δ is a number greater than 0.5 and less than or equal to 1. The reduction factor *c* is set based on the signal-to-noise ratio (SNR) and grayscale resolution. The SNR should be greater than 10, and the grayscale resolution should ensure that pixels at each level in the acquired image are distinguishable. The exposure time Ta of each frame in the automatic brightness adjustment process to achieve the indirect target brightness Bc is calculated based on the reduction factor c, the number of combined pixels A in multi-pixel mode, the sensitivity factor Δ, and the exposure time T of each frame in the exposure mode corresponding to the final target brightness B. The formula is as follows: Ta = (T*c) / (Δ*A).

2. The automatic brightness control method for an X-ray flat panel detector according to claim 1, characterized in that, An image acquired by a flat panel detector in the absence of X-rays is a noisy image of the flat panel. The signal-to-noise ratio of the X-ray image is obtained by dividing the indirect target brightness Bc of the exposed image by the brightness of the noisy image.

3. An electronic device, characterized in that, include: At least one processor; as well as, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions executable by the at least one processor, which, when executed by the at least one processor, enables the at least one processor to perform the automatic brightness control method for the X-ray flat panel detector as described in any one of claims 1 to 2.

4. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the automatic brightness control method for the X-ray flat panel detector as described in any one of claims 1 to 2.

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