US-12625092-B2 - Correction method for scatter signal caused by wedge filter

Abstract

A correction method for a scatter signal caused by a wedge filter includes: S 10 : performing an air scan by using CT equipment, and calculating a relative intensity W air of a scatter signal caused by a wedge filter in the air scan according to an air scan result, S 20 : performing an object scan on a plurality of experimental objects by using the CT equipment, and calculating theoretical scatter signal intensities W theo of the experimental objects in the object scan in combination with the result of S 10 , S 30 : fitting W theo of the experimental objects in the object scan and scatter signal intensity estimations W act of the experimental objects in the object scan, and S 40 : correcting the scan results according to a difference between a scatter signal intensity estimation W act of an actual object in the object scan and a theoretical scatter signal intensity W theo of the actual object in the object scan.

Inventors

• Guo Qing Zhang
• Yang Wang
• Wen Hao Chen
• Tao Tao Li
• Yi Tian

Assignees

• SIEMENS SHANGHAI MEDICAL EQUIPMENT LTD.

Dates

Publication Date

20260512

Application Date

20220824

Priority Date

20210930

Claims (7)

1. 1 . A correction method for a scatter signal caused by a wedge filter, comprising: S 10 : performing an air scan by using computed tomography (CT) equipment, and calculating a relative intensity of a scatter signal caused by a wedge filter in the air scan according to an air scan result, denoted as an air scan scatter signal relative intensity W air ; S 20 : performing an object scan on a plurality of experimental objects by using the CT equipment, and calculating theoretical scatter signal intensities W theo of the experimental objects in the object scan according to the air scan scatter signal relative intensity W air , the air scan result, and object scan results of the experimental objects; S 30 : fitting the theoretical scatter signal intensities W theo of the experimental objects in the object scan and measured scatter signal intensities W meas of the experimental objects in the object scan according to the object scan results of the experimental objects, to obtain a fitting formula for calculating a scatter signal intensity estimation W act ; and S 40 : performing an object scan on an actual object by using the CT equipment, calculating a theoretical scatter signal intensity W theo of the actual object in the object scan according to the air scan scatter signal relative intensity W air , the air scan result, and an object scan result of the actual object, calculating a scatter signal intensity estimation W act of the actual object in the object scan according to the fitting formula and the theoretical scatter signal intensity W theo of the actual object in the object scan, and correcting the scan results according to a difference between the scatter signal intensity estimation W act of the actual object in the object scan and the theoretical scatter signal intensity W theo of the actual object in the object scan.
2. 2 . The correction method for a scatter signal caused by a wedge filter according to claim 1 , wherein the step S 10 comprises: S 11 : performing a CT air scan by using a narrow collimator and a wide collimator respectively in a case that the wedge filter is used, to obtain a narrow collimated scatter signal intensity I n_air in the air scan and a wide collimated air scatter signal intensity I b_air in the air scan respectively; S 12 : performing a CT air scan by using the narrow collimator and the wide collimator respectively in a case that the wedge filter is not used, to obtain an initial narrow collimated signal intensity I n_p_air in the air scan and an initial wide collimated signal intensity I b_p_air in the air scan respectively; and S 13 : calculating the air scan scatter signal relative intensity W air by Formula (1) below: W air = ( I b ⁢ _ ⁢ air - I n ⁢ _ ⁢ air ) / I b ⁢ _ ⁢ air - ( I b ⁢ _ ⁢ p ⁢ _ ⁢ air - I n ⁢ _ ⁢ p ⁢ _ ⁢ air ) / I b ⁢ _ ⁢ p ⁢ _ ⁢ air .
3. 3 . The correction method for a scatter signal caused by a wedge filter according to claim 2 , wherein the step S 20 comprises: S 21 : performing a CT object scan on the experimental objects by using the narrow collimator and the wide collimator respectively in a case that the wedge filter is used, to obtain narrow collimated scatter signal intensities I n_obj of the experimental objects in the object scan and wide collimated scatter signal intensities I b_obj in the object scan; and S 22 : calculating the theoretical scatter signal intensities W theo of the experimental objects in the object scan by Formula (2) below: W theo = W air * I b ⁢ _ ⁢ obj / I b ⁢ _ ⁢ air .
4. 4 . The correction method for a scatter signal caused by a wedge filter according to claim 3 , wherein the step S 30 comprises: S 31 : calculating the measured scatter signal intensities W meas of the experimental objects in the object scan by Formula (3) below: W meas =I b_obj /I b_air −I n_obj /I n_air ; and S 32 : fitting Formula (4) below according to the measured scatter signal intensities W meas of the experimental objects in the object scan and the theoretical scatter signal intensities W theo of the experimental objects in the object scan, wherein the measured scatter signal intensities W meas of the experimental objects in the object scan are used as fit target values of scatter signal intensity estimations W act in the object scan, W act = p · W theo * G , wherein P is a scaling factor, and G is a Gaussian convolution kernel.
5. 5 . The correction method for a scatter signal caused by a wedge filter according to claim 4 , wherein the step S 40 comprises: S 41 : performing a CT object scan on the actual object by using the wide collimator in a case that the wedge filter is used, to obtain a wide collimated scatter signal intensity I b_obj of the actual object in the object scan; S 42 : calculating the theoretical scatter signal intensity W theo of the actual object in the object scan by Formula (2) according to the wide collimated scatter signal intensity I b_obj of the actual object in the object scan; S 43 : calculating the scatter signal intensity estimation W act of the actual object in the object scan by the fitting formula; and S 44 : correcting the scan results according to the difference between the scatter signal intensity estimation W act of the actual object in the object scan and the theoretical scatter signal intensity W theo of the actual object in the object scan.
6. 6 . The correction method for a scatter signal caused by a wedge filter according to claim 1 , wherein the experimental objects are CT water equivalent phantoms.
7. 7 . A non-transitory storage medium, storing a correction program for a scatter signal caused by a wedge filter, wherein when the correction program is executed by a processor, the steps of the correction method according to claim 1 are processed.

Description

TECHNICAL FIELD The present disclosure relates to a correction method, and in particular, to a method for correcting a scatter signal caused by a wedge filter in computed tomography (CT) equipment. BACKGROUND A wedge filter is an exceedingly common assembly in a CT system. The wedge filter may form a more even dose distribution in a patient. Because the wedge filter is a relatively strong attenuation object, the wedge filter generates scatter signals outside a scanned object. Although an air calibration can remove partial scatter signals caused by the wedge filter, some scatter signals remain in the scanned object. At present, the scatter signals caused by the wedge filter may be removed through an anti-scatter grid or a computing model-based correction algorithm, which have strong scene dependence and need to be calibrated for each scene. SUMMARY An objective of the present disclosure is to provide a correction method for a scatter signal caused by a wedge filter, which can correct a scatter signal caused by a wedge filter more accurately. The present disclosure further provides a storage medium, storing a correction program for a scatter signal caused by a wedge filter, where when the correction program is executed by a processor, the steps of the correction method for a scatter signal caused by a wedge filter are processed. The present disclosure provides a correction method for a scatter signal caused by a wedge filter, including: S10: performing an air scan by using CT equipment, and calculating a relative intensity of a scatter signal caused by a wedge filter in the air scan according to an air scan result, denoted as an air scan scatter signal relative intensity Wair: S20: performing an object scan on a plurality of experimental objects by using the CT equipment, and calculating theoretical scatter signal intensities Wtheo of the experimental objects in the object scan according to the air scan scatter signal relative intensity Wair, the air scan result, and object scan results of the experimental objects: S30: fitting the theoretical scatter signal intensities Wtheo of the experimental objects in the object scan and measured scatter signal intensities Wmeas of the experimental objects in the object scan according to the object scan results of the experimental objects, to obtain a fitting formula for calculating a scatter signal intensity estimation Wact, and S40: performing an object scan on an actual object by using the CT equipment, calculating a theoretical scatter signal intensity Wtheo of the actual object in the object scan according to the air scan scatter signal relative intensity Wair, the air scan result, and an object scan result of the actual object, calculating a scatter signal intensity estimation Wact of the actual object in the object scan according to the fitting formula and the theoretical scatter signal intensity Wtheo of the actual object in the object scan, and correcting the scan results according to a difference between the scatter signal intensity estimation Wact of the actual object in the object scan and the theoretical scatter signal intensity Wtheo of the actual object in the object scan. In the correction method for a scatter signal caused by a wedge filter provided by the present disclosure, air scan data is used as an input so that the estimation of a scatter signal caused by a wedge filter is more accurate. In addition, the method requires fewer algorithms and is also applicable to scans of clinical patients. In another exemplary implementation of the correction method for a scatter signal caused by a wedge filter, step S10 includes: S11: performing a CT air scan by using a narrow collimator and a wide collimator, respectively, in a case that the wedge filter is used, to obtain a narrow collimated scatter signal intensity In_air in the air scan and a wide collimated air scatter signal intensity Ib_air in the air scan respectively: S12: performing a CT air scan by using the narrow collimator and the wide collimator respectively in a case that the wedge filter is not used, to obtain an initial narrow collimated signal intensity In_p_air in the air scan and an initial wide collimated signal intensity Ib_p_air in the air scan respectively: and S13: calculating the air scan scatter signal relative intensity Wair by Formula (1) below: Wair=(Ib⁢_⁢air-In⁢_⁢air)/Ib⁢_⁢air-(Ib⁢_⁢p⁢_⁢air-In⁢_⁢p⁢_⁢air)/Ib⁢_⁢p⁢_⁢air.Formula⁢ (1) The scatter signal in the air scan with the wedge filter is first obtained in S11, and then the scatter signal in the air scan with the wedge filter is removed in S12. The difference between the scatter signals obtained in S11 and S12 is calculated to obtain the relative intensity in S13. It is only in this case that the obtained signal can be considered as the scatter signal of only the wedge filter. The air scan scatter signal relative intensity obtained in S13 excludes the impact of different initial signal intensities caused by both the wide collimat