CN112237434B - Method for moving focus of computer tomography apparatus, medium and computer tomography apparatus - Google Patents
Method for moving focus of computer tomography apparatus, medium and computer tomography apparatus Download PDFInfo
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- CN112237434B CN112237434B CN201910638193.6A CN201910638193A CN112237434B CN 112237434 B CN112237434 B CN 112237434B CN 201910638193 A CN201910638193 A CN 201910638193A CN 112237434 B CN112237434 B CN 112237434B
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- 238000002591 computed tomography Methods 0.000 title claims abstract description 22
- 238000000034 method Methods 0.000 title claims abstract description 19
- 230000004044 response Effects 0.000 claims abstract description 76
- 238000012935 Averaging Methods 0.000 claims abstract description 10
- 238000013459 approach Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/54—Control of apparatus or devices for radiation diagnosis
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/58—Testing, adjusting or calibrating thereof
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Abstract
The invention discloses a method for moving a focus of a computer tomography apparatus, a non-transitory computer readable medium and a computer tomography apparatus. The method for moving the focus of the computer tomography apparatus comprises: measuring module response bias at +/-N from nominal focus position; subtracting the wedge component from the module response deviation to obtain an absolute module response deviation; averaging the absolute module response deviation in one module to obtain average module response F of different focus positions; averaging the air calibration signals in a module to obtain an average module response A of air calibration data; calculating a focus moving distance D according to the average module response F of different focus positions and the average module response A of air calibration data; at the next rotational scan, the focus is moved by the focus movement distance D.
Description
Technical Field
The invention relates to a method of moving the focus of a computed tomography apparatus.
Background
Open-loop focus control works well in CT systems when the focus movement is small. However, if there is a large focus shift, a high anti-scatter grid may be problematic, the root cause of which is that there are subtle differences in the signals of neighboring modules as the focus shifts. If this difference occurs in the intermediate module, then artifacts can be created in the clinical scan.
With module sorting (module sorting), intermediate modules can be made insensitive to focus movements. However, this method is time consuming and expensive. In some cases, it may even be difficult to find enough modules that meet the module classification criteria.
Disclosure of Invention
In view of this, the present invention proposes a method of moving the focus of a computer tomography apparatus, a non-transitory computer readable medium and a computer tomography apparatus.
According to a first aspect of the present invention there is provided a method of moving a focus of a computed tomography apparatus, comprising: measuring module response bias at +/-N from nominal focus position; subtracting the wedge component from the module response deviation to obtain an absolute module response deviation; averaging the absolute module response deviation in one module to obtain average module response F of different focus positions; averaging the air calibration signals in a module to obtain an average module response A of air calibration data; calculating a focus moving distance D according to the average module response F of different focus positions and the average module response A of air calibration data; at the next rotational scan, the focus is moved by the focus movement distance D.
In an embodiment, the rootCalculating the focal movement distance D from the average module response F of the different focal positions and the average module response a of the air calibration data includes calculating the focal movement distance D according to the following equation: d=2n×a 0 /F 0 Wherein F 0 Is the average module response of the different focus positions of the edge module, A 0 Is the average module response of the air calibration data for that edge module.
According to a second aspect of the present invention there is provided a non-transitory computer readable medium storing instructions executable by one or more processors, the instructions being executable to: measuring module response bias at +/-N from nominal focus position; subtracting the wedge component from the module response deviation to obtain an absolute module response deviation; averaging the absolute module response deviation in one module to obtain average module response F of different focus positions; averaging the air calibration signals in a module to obtain an average module response A of air calibration data; calculating a focus moving distance D according to the average module response F of different focus positions and the average module response A of air calibration data; at the next rotational scan, the focus is moved by the focus movement distance D.
In one embodiment, calculating the focus movement distance D from the average module response F of the different focus positions and the average module response a of the air calibration data includes calculating the focus movement distance D according to the following equation: d=2n×a 0 /F 0 Wherein F 0 Is the average module response of the different focus positions of the edge module, A 0 Is the average module response of the air calibration data for that edge module.
According to a third aspect of the present invention there is provided a computer tomography apparatus comprising a non-transitory computer readable medium as described above.
The method of moving the focus of a computer tomography apparatus, the non-transitory computer readable medium and the computer tomography apparatus of the present invention can obtain an accurate focus position and are easy to integrate in a scanning procedure. With this approach, the module classification on the detector side will become faster and easier. The method can reduce effort in the production process of the data processing system and improve focus stability during clinical individual scans, thus improving image quality.
Drawings
The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail preferred embodiments thereof with reference to the attached drawings in which:
fig. 1 is a flow chart of a method of moving the focus of a computed tomography apparatus according to an embodiment of the invention.
FIG. 2 is a block response bias for different focus positions according to an embodiment of the invention.
FIG. 3 is an absolute module response bias for different focus positions according to an embodiment of the invention.
FIG. 4 is an average module response for different focus positions according to an embodiment of the invention.
FIG. 5 is an average module response of air calibration data according to an embodiment of the invention.
Detailed Description
The present invention will be further described in detail with reference to the following examples, in order to make the objects, technical solutions and advantages of the present invention more apparent.
Fig. 1 is a flow chart of a method 100 of moving a focus of a computed tomography apparatus according to an embodiment of the invention. The method 100 of moving the focus of a computed tomography apparatus includes step S102, step S104, step S106, step S108, step S110, and step S112.
In step S102, the module response bias at +/-N from the nominal focus position is measured. N has length units. FIG. 2 is a block response bias for different focus positions according to an embodiment of the invention. The curve shown in fig. 2 includes not only the signal difference of the module but also wedge information.
In step S104, the wedge component is subtracted from the module response deviation to obtain an absolute module response deviation. FIG. 3 is an absolute module response bias for different focus positions according to an embodiment of the invention.
Since the above-mentioned response has homogeneity in one module, in order to reduce noise, in step S106, the absolute module response deviation is averaged in one module, resulting in an average module response F of different focal positions. FIG. 4 is an average module response for different focus positions according to an embodiment of the invention.
In step S108, the air calibration signal is averaged in one module to obtain an average module response a of the air calibration data. FIG. 5 is an average module response of air calibration data according to an embodiment of the invention. During a patient scan, the signal of the edge channel is evaluated to determine if it is covered by the patient. If not covered, the signal will be air calibrated and averaged in one module.
In step S110, a focus movement distance D is calculated from the average module response F of the different focus positions and the average module response a of the air calibration data. In the present embodiment, the focal point movement distance D is calculated according to the following equation:
D＝2N*A 0 /F 0 wherein F 0 Is the average module response of the different focus positions of the edge module, A 0 Is the average module response of the air calibration data for that edge module.
To ensure F 0 Larger, preferably modules with larger response deviations are placed in an outer position.
In step S112, the focus is moved by the focus movement distance D at the next rotational scanning.
According to a second aspect of the present invention there is also provided a non-transitory computer readable medium storing instructions executable by one or more processors, the instructions being executed to implement step S102, step S104, step S106, step S108, step S110 and step S112.
According to a third aspect of the present invention, there is also provided a computer tomography apparatus, the above-mentioned non-transitory computer readable medium.
The method of moving the focus of a computer tomography apparatus, the non-transitory computer readable medium and the computer tomography apparatus of the present invention can obtain an accurate focus position and are easy to integrate in a scanning procedure. With this approach, the module classification on the detector side will become faster and easier. The method can reduce effort in the production process of the data processing system and improve focus stability during clinical individual scans, thus improving image quality.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (5)
1. A method of moving a focal point of a computed tomography apparatus, comprising:
measuring a module response bias at focus deviation +/-N from a nominal focus position, N having length units;
subtracting the wedge component from the module response deviation to obtain an absolute module response deviation;
averaging the absolute module response deviation in one module to obtain average module response F of different focus positions;
averaging the air calibration signals in a module to obtain an average module response A of air calibration data;
calculating a focus moving distance D according to the average module response F of different focus positions and the average module response A of air calibration data;
at the next rotational scan, the focus is moved by the focus movement distance D.
2. The method of claim 1, wherein calculating the focal distance D from the average module response F of the different focal positions and the average module response a of the air calibration data comprises calculating the focal distance D according to the following equation:
D＝2N*A 0 /F 0 wherein F 0 Is the average module response of the different focus positions of the edge module, A 0 Is the average module response of the air calibration data for that edge module.
3. A non-transitory computer-readable medium storing instructions executable by one or more processors, the instructions being executable to:
measuring a module response bias at focus deviation +/-N from a nominal focus position, N having length units;
subtracting the wedge component from the module response deviation to obtain an absolute module response deviation;
averaging the absolute module response deviation in one module to obtain average module response F of different focus positions;
averaging the air calibration signals in a module to obtain an average module response A of air calibration data;
calculating a focus moving distance D according to the average module response F of different focus positions and the average module response A of air calibration data;
at the next rotational scan, the focus is moved by the focus movement distance D.
4. The non-transitory computer-readable medium of claim 3, wherein calculating the focal distance D from the average module response F for the different focal positions and the average module response a for the air calibration data comprises calculating the focal distance D according to:
D＝2N*A 0 /F 0 wherein F 0 Is the average module response of the different focus positions of the edge module, A 0 Is the average module response of the air calibration data for that edge module.
5. A computer tomography apparatus comprising the non-transitory computer readable medium of claim 3 or 4.
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| JPH1189826A (en) * | 1997-09-17 | 1999-04-06 | Shimadzu Corp | X-ray ct system |
| CN1552288A (en) * | 2003-12-18 | 2004-12-08 | 沈阳东软数字医疗***股份有限公司 | Method for correcting bulb focus offset of CT machine |
| CN1895172A (en) * | 2005-07-07 | 2007-01-17 | 西门子公司 | Method for focus adjustment in a ct apparatus |
| JP2007014608A (en) * | 2005-07-08 | 2007-01-25 | Hitachi Medical Corp | X-ray ct apparatus |
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