Method for correcting scattered signals caused by wedge filter and storage medium

Abstract

The correction method of the scattered signal caused by the wedge filter comprises the following steps: S10: performing air scanning by using a CT device, and calculating the relative intensity W of the scattered signal caused by the wedge filter under air scanning according to the air scanning result air ; S20: performing object scanning of a plurality of experimental objects by using the CT device, and calculating the theoretical scattered signal intensity W of the experimental objects under the object scanning in combination with the result of S10 theo ; S30: fitting the W theo of the experimental objects under the object scanning and the scattered signal intensity estimation W act of the experimental objects under the object scanning; and S40: correcting the scanning result according to the difference between the scattered signal intensity estimation W act of the actual object under the object scanning and the theoretical scattered signal intensity W theo of the actual object under the object scanning. The method can more accurately correct the scattered signal caused by the wedge filter. The application also provides a storage medium.

Description

Technical Field

[0001] This invention relates to a correction method, and more particularly to a method for correcting scattered signals caused by a wedge filter in a CT scanner. Background Technology

[0002] Wedge filters are a very common component in CT systems. They create a more uniform dose distribution within the patient's body. Because a wedge filter is a relatively strong attenuator, it generates scattered signals outside the scanned object. Although air calibration can remove some of the scattered signals caused by the wedge filter, some scattered signals will still remain within the scanned object.

[0003] Currently, the scattered signals caused by wedge filters can be removed by backscattering grids or computational model-based correction algorithms. However, these methods are highly scene-dependent and require calibration for each scene. Summary of the Invention

[0004] The purpose of this invention is to provide a method for correcting the scattered signal caused by a wedge filter, which can more accurately correct the scattered signal caused by the wedge filter.

[0005] The present invention also provides a storage medium storing a correction program for a scattering signal caused by a wedge filter, wherein the steps of a correction method for the scattering signal caused by the wedge filter are executed by a processor.

[0006] This invention provides a method for correcting scattered signals caused by a wedge filter, comprising: S10: performing an air scan using a CT scanner, and calculating the relative intensity of the scattered signal caused by the wedge filter under the air scan based on the air scan results, denoted as the relative intensity W of the air scan scattered signal. air S20: Perform object scanning on multiple experimental subjects using a CT scanner, and determine the relative intensity W of the air scan scattering signal. air The theoretical scattered signal intensity W of the experimental object under object scanning was calculated from the air scan results and the object scan results of the experimental object. theo S30: The theoretical scattering signal intensity W of the experimental object under object scanning, based on the object scanning results. theo The measured scattered signal intensity W of the experimental object under object scanning meas By performing a fitting, a fitting formula is obtained to calculate the estimated value W of the scattered signal. act S40: Using CT equipment to perform object scanning of the actual object, and based on the relative intensity W of the air scan scattering signal. air The theoretical scattered signal intensity W of the actual object under object scanning is calculated from the air scan results and the actual object's object scan results. theoBased on the fitting formula and the theoretical scattering signal intensity W of the actual object under object scanning, theo The estimated intensity W of the scattered signal of the actual object under object scanning was calculated. act The estimated W is based on the intensity of the scattered signal from the actual object during object scanning. act The theoretical scattered signal intensity W of the actual object under object scanning theo The difference correction scan results.

[0007] The method for correcting the scattered signal caused by the wedge filter provided by this invention uses air scan data as input, which makes the estimation of the scattered signal caused by the wedge filter more accurate and requires less algorithm, and is also applicable to clinical patient scans.

[0008] In another illustrative embodiment of the method for correcting the scattered signal caused by the wedge filter, step S10 includes: S11: performing CT air scans using a narrow collimator and a wide collimator respectively when using a wedge filter, and obtaining the narrow collimated scattered signal intensity I under air scan. n_air And the intensity of wide collimated air scattering signal I under air scanning b_air S12: Perform CT air scans using both narrow collimators and wide collimators without using a wedge filter, and obtain the initial signal intensity I under narrow collimation during air scans. n_p_air and air scan with wide collimation initial signal intensity I b_p_air S13: The relative intensity W of the air scan scattering signal is calculated using the following formula (1). air :

[0009] W air =(I b_air -I n_air ) / I b_air -(I b_p_air -I n_p_air ) / I b_p_air Formula (1).

[0010] In step S11, the scattered signal under air scanning with a wedge filter is first obtained. In step S12, the scattered signal under air scanning with the wedge filter is then removed. In step S13, the scattered signals obtained in steps S11 and S12 are subtracted to obtain the relative intensity, which can then be considered as the scattered signal from the wedge filter alone. Furthermore, the relative intensity of the air scanning scattered signal obtained in step S13 also eliminates the influence of different initial signal intensities caused by wide and narrow collimators.

[0011] In another illustrative embodiment of the method for correcting the scattered signal caused by the wedge filter, step S20 includes: S21: using a narrow collimator and a wide collimator to perform CT object scans on each experimental object when using a wedge filter, and obtaining the narrow collimated scattered signal intensity I under the object scan of each experimental object. n_obj and the intensity of the collimated scattered signal I under object scanning b_obj S22: The theoretical scattering signal intensity W of each experimental object under object scanning is calculated using the following formula (2). theo :W theo =W air *I b_obj / I b_air Formula (2). Step 20 After the air correction in step 10, calculate how much of the scattered signal remains after passing through the experimental object. Since the scattering caused by the experimental object is not considered, the following steps S30 and S40 are performed.

[0012] In another illustrative embodiment of the method for correcting the scattered signal caused by the wedge filter, step S30 includes: S31: calculating the measured scattered signal intensity W of each experimental object under object scanning using the following formula (3). meas :W meas =I b_obj / I b_air -I n_obj / I n_air Formula (3); and S32: Based on the measured scattering signal intensity W of the experimental object under object scanning. meas The theoretical scattered signal intensity W of the experimental object under object scanning theo The following formula (4) is fitted, where W is the measured scattering signal intensity of the experimental object under object scanning. meas W is the estimated intensity of the scattered signal under object scanning. act The fitted target value,

[0013] W act =p·W theo *G formula (4), where p is the correction factor and G is the Gaussian convolution kernel.

[0014] In another illustrative embodiment of the method for correcting the scattered signal caused by the wedge filter, step S40 includes: S41: performing a CT object scan on the actual object using a wide collimator while using a wedge filter, and obtaining the wide collimated scattered signal intensity I under the object scan of the actual object. b_obj S42: Based on the object scan of the actual object, the wide collimated scattering signal intensity I b_obj The theoretical scattering signal intensity W of the actual object under object scanning is calculated using formula (2).theo S43: Calculate the estimated intensity W of the scattered signal of the actual object under object scanning using a fitting formula. act S44: Estimate W based on the intensity of the scattered signal of the actual object under object scanning. act The theoretical scattered signal intensity W of the actual object under object scanning theo The difference correction scan results.

[0015] The narrow collimator and the wide collimator used in this invention are both commonly used devices in CT equipment. The narrow collimator refers to a collimator with an aperture of 0.5 mm or less, and the wide collimator refers to a collimator with an aperture larger than that of the narrow collimator.

[0016] In another illustrative embodiment of the method for correcting the scattered signal caused by the wedge filter, the experimental object is a CT water equivalent phantom.

[0017] The present invention also provides a storage medium storing a correction program for a scattering signal caused by a wedge filter, wherein the correction program, when executed by a processor, processes the steps of the correction method described above. Attached Figure Description

[0018] The following figures are for illustrative purposes only and do not limit the scope of the invention.

[0019] Figure 1 A flowchart illustrating an embodiment of a method for correcting scattered signals caused by a wedge filter.

[0020] Figure 2 A flowchart illustrating another implementation of a method for correcting scattered signals caused by a wedge filter.

[0021] Figure 3 The display shows the difference signal of the air scan obtained in steps S11 and S12, where the solid line represents the case of CT air scan using a narrow collimator and a wide collimator respectively when using a wedge filter, and the dashed line represents the case of CT air scan using a narrow collimator and a wide collimator respectively when not using a wedge filter.

[0022] Figure 4 In an illustrative embodiment of the method for correcting the scattered signal caused by the wedge filter, the relative intensity W of the air scan scattered signal is obtained in step S13. air .

[0023] Figure 5 This diagram illustrates the fitting process of S32 in a schematic embodiment of a method for correcting the scattered signal caused by a wedge filter, where the dashed line represents the measured scattered signal intensity W of the experimental object under object scanning. measThe solid line represents the estimated intensity W of the scattered signal of the experimental object under object scanning. act .

[0024] Figure 6A This represents a reconstructed image of a 30cm diameter CT water equivalent phantom that has not been corrected by the method of this invention.

[0025] Figure 6B This represents a reconstructed image of a 30cm diameter CT water equivalent phantom after correction using the method of this invention. Detailed Implementation

[0026] To provide a clearer understanding of the technical features, objectives, and effects of the invention, specific embodiments of the invention are now described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate components with the same or similar structures but the same function.

[0027] In this document, “illustrative” means “serving as an example, illustration or description”, and any illustration or implementation described herein as “illustrative” should not be construed as a more preferred or advantageous technical solution.

[0028] To keep the drawings simple, each drawing only schematically shows the parts related to the present invention, and they do not represent the actual structure of the product.

[0029] Figure 1 A flowchart illustrating an embodiment of a method for correcting scattered signals caused by a wedge filter. (Refer to...) Figure 1 Methods for correcting scattered signals caused by wedge filters include

[0030] S10: Perform an air scan using a CT scanner, and calculate the relative intensity of the scattered signal caused by the wedge filter under the air scan based on the air scan results. This is denoted as the relative intensity W of the air scan scattered signal. air ;

[0031] S20: Use CT equipment to perform object scans on multiple experimental subjects and calculate the relative intensity W of the air scan scattering signal. air The theoretical scattered signal intensity W of the experimental object under object scanning was calculated from the air scan results and the object scan results of the experimental object. theo The experimental subjects here can be CT water equivalent phantoms or human bodies.

[0032] S30: The theoretical scattered signal intensity W of the experimental object obtained by measuring the experimental object under object scanning based on the object scanning results. theo The measured scattered signal intensity W of the experimental object was obtained by object scanning. meas By performing a fitting, a fitting formula is obtained to calculate the estimated intensity W of the scattered signal.act ,and

[0033] S40: Use CT equipment to perform object scanning of the actual object, and calculate the relative intensity W of the air scan scattering signal. air The theoretical scattered signal intensity W of the actual object under object scanning is calculated from the air scan results and the actual object's object scan results. theo Based on the fitting formula and the theoretical scattering signal intensity W of the actual object under object scanning, theo The estimated intensity W of the scattered signal of the actual object under object scanning was calculated. act The estimated W is based on the intensity of the scattered signal from the actual object during object scanning. act The theoretical scattered signal intensity W of the actual object under object scanning theo The difference correction scan results.

[0034] Figure 2 A flowchart illustrating another illustrative implementation of a method for correcting scattered signals caused by a wedge filter. (Refer to...) Figure 2 Methods for correcting the scattered signal caused by the wedge filter include:

[0035] S11: Using a wedge filter, CT air scans were performed with both narrow and wide collimators to obtain the narrow collimated scattered signal intensity I under air scan conditions. n_air And the intensity of wide collimated air scattering signal I under air scanning b_air ;

[0036] S12: Perform CT air scans using both narrow and wide collimators without a wedge filter, and obtain the initial signal intensity I under narrow collimation during air scans. n_p_air and air scan with wide collimation initial signal intensity I b_p_air ; Figure 3 The differential signals of air scattering obtained in steps S11 and S12 are displayed. The solid lines represent CT air scans performed with narrow collimators and wide collimators when using a wedge filter, respectively, while the dashed lines represent CT air scans performed with narrow collimators and wide collimators when not using a wedge filter.

[0037] S13: Calculate the relative intensity W of the air scan scattering signal using the following formula (1). air :

[0038] W air =(I b_air -I n_air ) / I b_air -(I b_p_air -I n_p_air ) / I b_p_air Formula (1);

[0039] Figure 4 Indicates by Figure 3 Subtracting the curves from each other yields the relative intensity W of the air scan scattering signal. air .

[0040] S21: Using a wedge filter, CT scans of each experimental object were performed using both narrow and wide collimators. The results can be tabulated to obtain the narrow collimated scattering signal intensity I of each experimental object during the scan. n_obj and the intensity of the collimated scattered signal I under object scanning b_obj ;

[0041] S22: Calculate the theoretical scattered signal intensity W of each experimental object under object scanning using the following formula (2). theo :

[0042] W theo =W air *I b_obj / I b_air , formula (2);

[0043] S31: Calculate the measured scattering signal intensity W of each experimental object under object scanning using the following formula (3). meas

[0044] W meas =I b_obj / I b_air -I n_obj / I n_air , formula (3);

[0045] S32: Based on the measured scattered signal intensity W of the experimental object under object scanning. meas The theoretical scattered signal intensity W of the experimental object under object scanning theo The following formula (4) is fitted, where W is the measured scattering signal intensity of the experimental object under object scanning. meas W is the estimated intensity of the scattered signal under object scanning. act The fitted target value, W act =p·W theo *G Formula (4), where p is the scaling factor and G is the Gaussian convolution kernel;

[0046] S41: Using a wedge filter, a wide collimator is used to perform a CT scan of the actual object to obtain the wide collimated scattered signal intensity I under the object scan. b_obj ;

[0047] S42: Based on the object scan of the actual object, the wide collimated scattering signal intensity I b_objThe theoretical scattering signal intensity W of the actual object under object scanning is calculated using formula (2). theo ;

[0048] S43: Calculate the estimated scattered signal intensity W of the actual object under object scanning using a fitting formula. act ,as well as

[0049] S44: Estimate W based on the scattered signal intensity of the actual object during object scanning. act The theoretical scattered signal intensity W of the actual object under object scanning theo The difference correction scan results.

[0050] Figure 6A This represents a reconstructed image of a 30cm diameter CT water equivalent phantom that has not been corrected by the method of this invention. Figure 6B The images show reconstructed images of a 30cm diameter CT water equivalent phantom after correction using the method of this invention. It can be seen that the area indicated by the arrow shows heavier shadows in the reconstructed image of the 30cm diameter CT water equivalent phantom without correction using the method of this invention, while the shadows in the reconstructed image of the 30cm CT water equivalent phantom after correction using the method of this invention are lighter.

[0051] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0052] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent implementation schemes or modifications made without departing from the spirit of the present invention, such as combinations, divisions or repetitions of features, should be included within the scope of protection of the present invention.

Claims

1. A method for correcting scattered signals caused by a wedge filter, characterized in that, include: S10: Perform an air scan using a CT scanner, and calculate the relative intensity of the scattered signal caused by the wedge filter under the air scan based on the air scan results. This is denoted as the relative intensity of the air scan scattered signal. , S20: Perform object scanning on multiple experimental subjects using a CT scanner, and determine the relative intensity of the air scan scattering signal based on the results. The theoretical scattering signal intensity of the experimental object under object scanning was calculated from the air scan results and the object scan results of the experimental object. , S30: Based on the object scanning results of the experimental object, determine the theoretical scattering signal intensity of the experimental object under object scanning. and the measured scattering signal intensity of the experimental object under object scanning. By fitting the data, an estimate for calculating the intensity of the scattered signal is obtained. The fitting formula, and S40: Perform an object scan using a CT scanner, and determine the relative intensity of the air scan scattering signal. The theoretical scattered signal intensity of the actual object under object scanning is calculated from the air scan results and the object scan results of the actual object. Based on the fitting formula and the theoretical scattering signal intensity of the actual object under object scanning, The estimated intensity of the scattered signal of the actual object under object scanning was calculated. Estimate the intensity of the scattered signal from the actual object under object scanning. The theoretical scattering signal intensity of the actual object under object scanning. The difference correction scan results.

2. The method for correcting the scattered signal caused by the wedge filter as described in claim 1, wherein, Step S10 includes: S11: Using a wedge filter, CT air scans were performed with both narrow and wide collimators to obtain the intensity of the narrow collimated scattered signal under air scan conditions. and the intensity of wide collimated air scattering signal under air scanning , S12: Perform CT air scans using both narrow and wide collimators without a wedge filter, and obtain the initial signal intensity of the narrow collimator under air scan conditions. Initial signal intensity under wide collimation in air scan ,and S13: The relative intensity of the air scan scattering signal is calculated using the following formula (1). : Official (1).

3. The method for correcting the scattered signal caused by the wedge filter as described in claim 2, wherein, Step S20 includes: S21: Using a wedge filter, CT scans were performed on each of the experimental objects using both a narrow collimator and a wide collimator to obtain the narrow collimated scattering signal intensity of each experimental object under object scanning. and the intensity of wide collimated scattered signal under object scanning ,and S22: Calculate the theoretical scattering signal intensity of each experimental object under object scanning using the following formula (2). : Official (2).

4. The method for correcting the scattered signal caused by the wedge filter as described in claim 3, wherein, Step S30 includes: S31: Calculate the measured scattering signal intensity of each experimental object under object scanning using the following formula (3). : Formula (3), and S32: Based on the measured scattering signal intensity of the experimental object under object scanning. and the theoretical scattering signal intensity of the experimental object under object scanning. The following formula (4) is fitted, wherein the measured scattering signal intensity of the experimental object under object scanning is... As an estimate of the scattered signal intensity during object scanning The fitted target value, Official (4), Where p is the correction factor and G is the Gaussian convolution kernel.

5. The method for correcting the scattered signal caused by the wedge filter as described in claim 4, wherein, Step S40 includes: S41: Using a wedge filter, a wide collimator is used to perform a CT scan of the actual object to obtain the wide collimated scattering signal intensity of the actual object under object scanning. , S42: Based on the object scan of the actual object, the intensity of the wide collimated scattering signal is determined. The theoretical scattering signal intensity of the actual object under object scanning is calculated using the formula (2). , S43: Calculate the estimated scattering signal intensity Wact of the actual object under object scanning using the fitting formula, and S44: Estimate the intensity of the scattered signal from the actual object under object scanning. The theoretical scattering signal intensity of the actual object under object scanning. The difference correction scan results.

6. The method for correcting the scattered signal caused by the wedge filter as described in claim 1, wherein, The experimental subject was a CT water equivalent phantom.

7. A storage medium, characterized in that, The storage medium stores a correction program for the scattering signal caused by the wedge filter, which, when executed by a processor, processes the steps of the correction method according to any one of claims 1-6.

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