CN105769231B - A kind of ray tracing method of beam-defining clipper on Z axis - Google Patents
A kind of ray tracing method of beam-defining clipper on Z axis Download PDFInfo
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- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/02—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
- A61B6/03—Computed tomography [CT]
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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
- A61B6/40—Arrangements for generating radiation specially adapted for radiation diagnosis
- A61B6/4021—Arrangements for generating radiation specially adapted for radiation diagnosis involving movement of the focal spot
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Abstract
The present invention relates to a kind of ray tracing method of beam-defining clipper on Z axis, the step of ray trace includes: the detector data of all reference channels for each view that beam-defining clipper reads multi-Slice CT Scanner；The detector data is divided into two groups along Z-direction；Calculate separately out average value, the standard variance of two groups of detector datas；Obtain the standard variance normalized value of two groups of detector datas；Fine tuning distance of the beam-defining clipper opening on Z axis is calculated according to the standard variance normalized value；The standard variance of the A group detector data is compared with the standard variance of the B group detector data, determines moving direction of the beam-defining clipper opening on Z axis；Beam-defining clipper controls two leaf according to the moving direction and finely tunes distance described in synchronizing moving on Z axis, completes ray trace of the beam-defining clipper on Z axis.The present invention can control beam-defining clipper mobile tracking x-ray source in the Z-axis direction, avoid meaningless X-ray injury.
Description
Technical field
The present invention relates to the technical fields of radiodiagnosis, and in particular to a kind of ray tracing method of beam-defining clipper on Z axis.
Background technique
Computed tomograph scanner system (CT) during the scanning process, due to generate X-ray anode target rotation shake and
Expanding with heat and contract with cold for anode target surface will lead to the offset of focus so that anode target surface 101 (focus) generate X-ray beam in Z axis
Random offset occurs.X-ray beam is irradiated to detector 104 after the histoorgan 103 of beam-defining clipper opening 102 and human body
On.Even if small offset, can also be generated on human body/detector after geometry amplifies larger inclined in spatial resolution
It moves, referring to fig. 4.These will cause image quality decrease in the X-ray beam that Z-direction generates random offset, cause indirectly
Meaningless x-ray bombardment.
Summary of the invention
The object of the present invention is to provide a kind of ray tracing method of beam-defining clipper on Z axis, based in current CT system
Beam-defining clipper can control beam-defining clipper mobile tracking x-ray source in the Z-axis direction, make to be irradiated to the X-ray beam on detector and just cover
Beamwidth needed for lid.
The purpose of the present invention is what is realized by following technical proposals: a kind of ray tracing method of beam-defining clipper on Z axis, institute
The step of stating ray trace include:
A, beam-defining clipper reads the detector data of all reference channels of each view of multi-Slice CT Scanner；
B, the detector data is divided into A group detector data and B group detector data along Z-direction；
C, the average value of the A group detector data and the average value of the B group detector data are calculated separately out；
D, the standard variance for going out A group detector data according to the mean value calculation of the A group detector data, according to described
The mean value calculation of B group detector data goes out the standard variance of B group detector data；
E, the standard variance of the standard variance of the A group detector data and the B group detector data is normalized, is obtained
To standard variance normalized value；
F, fine tuning distance of the beam-defining clipper opening on Z axis is calculated according to the standard variance normalized value；By the A group
The standard variance of detector data is compared with the standard variance of the B group detector data, determines beam-defining clipper opening in Z axis
On moving direction；
G, beam-defining clipper controls two leaf according to the moving direction and finely tunes distance described in synchronizing moving on Z axis, completes
Ray trace of the beam-defining clipper on Z axis；
The standard variance normalized value of=two groups of detector datas of the fine tuning distance and the product of beam-defining clipper opening.
Further, the standard variance of the A group detector data is greater than the standard variance of the B group detector data,
Beam-defining clipper opening is mobile to the direction where B group detector on Z axis；The standard variance of the A group detector data is less than institute
The standard variance of B group detector data is stated, beam-defining clipper opening is mobile to the direction where A group detector on Z axis.
Further, the reference channel is located at the outermost end of every row's detector.
Further, the reference channel cannot be blocked during CT scan, if be blocked, beam-defining clipper is according to institute
The CT empirical value for stating reference channel judges, and abnormal to upper System Reports.
Further, the beam-defining clipper opening width remains unchanged during CT scan.
The invention has the following advantages over the prior art:
The present invention can accurately obtain the shake of the ray in Z-direction, and control beam-defining clipper mobile tracking in the Z-axis direction
X-ray source is precisely limited the X-ray that x-ray source issues, and allows it just through the position and organ for needing to scan, maximum
Reduce to limit dosage suffered by patient.To realize bulb focus, beam-defining clipper, detector keeps high consistency, avoids meaningless
X-ray injury.
The present invention is described in detail below in conjunction with the drawings and specific embodiments.
Detailed description of the invention
Fig. 1 is the ray trace schematic diagram of present pre-ferred embodiments；
Fig. 2 is the structural schematic diagram of beam-defining clipper；
Fig. 3 is x-ray focus tracking effect figure；
Fig. 4 is the schematic diagram of x-ray focus offset.
Specific embodiment
Referring to Fig. 1, Fig. 2, a kind of the step of ray tracing method of beam-defining clipper on Z axis, the ray trace, includes:
A, beam-defining clipper reads the detector data of all reference channels 1 of each view of multi-Slice CT Scanner；
In the present embodiment, multi-Slice CT Scanner has 32 row's detectors, and every row's detector has 8 reference channels, in total 256 ginsengs
Examine channel.As shown in the table.
The reference channel at least needing to have ray trace in the side of every row's detector refers to every layer of multi-detector
The quantity in channel is the amount doesn't matter, and quantity is more, and the precision of control is better.One view be exactly all channels in detector all
Acquisition is primary, including reference channel.
Further, the reference channel is located at the outermost end of every row's detector.
B, the detector data is divided into A group detector data and B group detector data along Z-direction；
In the present embodiment, by above-mentioned detector data along Z-direction, it is divided into two groups from the center of Z axis, the 1st row
~the 16 row is set as A group, and A group detector data has 128；17th row~the 32nd row is set as B group, B group detector data
There are 128.The same data volume of two groups of detector datas is all N=128.
C, the average value of the A group detector data and the average value of the B group detector data are calculated separately out；
Mean_A=(data1+data2+…+dataN)÷N；
Mean_B=(dataN+1+dataN+2+…+data2N)÷N；N=128.
D, the standard variance for going out A group detector data according to the mean value calculation of the A group detector data, according to described
The mean value calculation of B group detector data goes out the standard variance of B group detector data；
σ _ A and σ _ B reflects the dispersion degree of two groups of detector datas.The measure value of dispersion degree is bigger, illustrate this two
The otherness of group detector data is bigger, and basic reason is exactly that the position of beam-defining clipper opening deviation occurs, so as to cause entrance
The ray on detector both sides is not balanced.
When standard variance σ _ A and σ _ B relatively when, illustrate two groups of reference channels of A, B receive x-ray dose basic one
Sample.The position of beam-defining clipper control opening just makes X-ray pass through human organ and is irradiated on detector, and there is no X to penetrate
The problem of line is deflected to which group in two groups of A, B, i.e., there is no meaningless radiohazards for the be irradiated to human organ of X-ray.
E, the standard variance of the standard variance of the A group detector data and the B group detector data is normalized, is obtained
To standard variance normalized value；
G=(| σ _ A- σ _ B |) ÷ (σ _ A+ σ _ B).
F, fine tuning distance of the beam-defining clipper opening 2 on Z axis is calculated according to the standard variance normalized value；By the A
The standard variance of group detector data is compared with the standard variance of the B group detector data, determines that beam-defining clipper opening 2 exists
Moving direction on Z axis；
In the present embodiment, the standard variance of the A group detector data is greater than the standard side of the B group detector data
Difference, beam-defining clipper opening are (downward) mobile to the direction where B group detector on Z axis；The standard side of the A group detector data
Difference be less than the B group detector data standard variance, beam-defining clipper be open on Z axis to where A group detector direction (to
On) mobile.
σ _ A > σ _ B, then it is mobile to B group detector direction.
σ _ A < σ _ B, then it is mobile to A group detector direction.
G, beam-defining clipper controls two leaf according to the moving direction and finely tunes distance described in synchronizing moving on Z axis, completes
Ray trace of the beam-defining clipper on Z axis.
The standard variance normalized value of fine tuning=two groups of detector datas of distance and the product of beam-defining clipper opening, Dist=G
×W.The unit of beam-defining clipper opening actual size, which is subject to, controls precision, generally as unit of micron.
Beam-defining clipper should set opening width in advance before CT scan, and the opening width of beam-defining clipper is protected during CT scan
It holds constant.On the one hand the control of beam-defining clipper openings of sizes is completed by the motor and code-disc of beam-defining clipper itself, on the other hand
It is also whether suitable come the size for judging beam-defining clipper gap by receiving the CT value of X-ray from detector end reference channel.
Beam-defining clipper main function is to limit the ray issued from x-ray source, the people for allowing it to scan just through needs
The dosage that body region and organ, as far as possible reduction patient are subject to.
Referring to fig. 2, the basic structure of beam-defining clipper has
A) 3: two self-movement leaf of leaf are placed in parallel, and the gap between two leaf parallel edges is that X-ray passes through
Place, and other places can be blocked by leaf.For different scanning demands, the size in gap can pass through two leaf
Relative motion is adjusted.
B) motor 4 and driving device: by transmission device, leaf movement is dragged.
C) encoder: the feedback device of leaf move distance.
D) limiter: the extreme position of detection leaf movement.
E) transmission device: including slideway 5, sliding block 6, lead screw 7, belt 8, motor drives leaf to move by transmission device.
Further, the reference channel cannot be blocked during CT scan, if be blocked, beam-defining clipper is according to institute
The CT empirical value for stating reference channel judges, and abnormal to upper System Reports.
Referring to Fig. 3, the test done in 32 row's CT systems, every 20 view do primary translation tracking adjustment.Horizontal axis indicates
The number of view, the longitudinal axis are the distance for translating tracking adjustment.It can be seen from the figure that the distance of translation tracking adjustment initial stage adjustment
It is bigger, when the distance for being adjusted to adjust after about 240~260 view is just obviously shortened, illustrate beam-defining clipper with
The offset of x-ray focus on track.
The content of the present embodiment is merely preferred embodiments of the present invention, but protection scope of the present invention is not limited to
In this, anyone skilled in the art within the technical scope of the present disclosure, the variation that can readily occur in or
Replacement, should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with the guarantor of claims
It protects subject to range.
Claims (2)
1. a kind of ray tracing method of beam-defining clipper on Z axis, it is characterised in that: the step of ray trace includes:
A, beam-defining clipper reads the detector data of all reference channels of each view of multi-Slice CT Scanner；
B, the detector data is divided into A group detector data and B group detector data along Z-direction；
C, the average value of the A group detector data and the average value of the B group detector data are calculated separately out；
D, the standard variance for going out A group detector data according to the mean value calculation of the A group detector data, according to the B group
The mean value calculation of detector data goes out the standard variance of B group detector data；
E, the standard variance of the standard variance of the A group detector data and the B group detector data is normalized, is marked
Quasi- normalized square mean value；
F, fine tuning distance of the beam-defining clipper opening on Z axis is calculated according to the standard variance normalized value；The A group is detected
The standard variance of device data is compared with the standard variance of the B group detector data, determines beam-defining clipper opening on Z axis
Moving direction；
G, beam-defining clipper controls two leaf according to the moving direction and finely tunes distance described in synchronizing moving on Z axis, completes limit beam
Ray trace of the device on Z axis；
The standard variance normalized value of=two groups of detector datas of the fine tuning distance and the product of beam-defining clipper opening.
2. ray tracing method according to claim 1, it is characterised in that: the standard variance of the A group detector data
Greater than the standard variance of the B group detector data, beam-defining clipper opening is mobile to the direction where B group detector on Z axis；Institute
The standard variance for stating A group detector data is less than the standard variance of the B group detector data, and beam-defining clipper opening is on Z axis to A
Direction where group detector is mobile.
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| US4991189A (en) * | 1990-04-16 | 1991-02-05 | General Electric Company | Collimation apparatus for x-ray beam correction |
| JP3554400B2 (en) * | 1995-03-10 | 2004-08-18 | ジーイー横河メディカルシステム株式会社 | Offset correction method and X-ray CT apparatus |
| US6310938B1 (en) * | 1999-08-27 | 2001-10-30 | General Electric Company | Methods and apparatus for calibrating CT x-ray beam tracking loop |
| JP3964615B2 (en) * | 2000-11-09 | 2007-08-22 | ジーイー・メディカル・システムズ・グローバル・テクノロジー・カンパニー・エルエルシー | Collimator control method and apparatus, and X-ray CT apparatus |
| JP2002238885A (en) * | 2001-02-02 | 2002-08-27 | Ge Medical Systems Global Technology Co Llc | Method and program for controlling position of x-ray focal point, and x-ray ct apparatus and x-ray tube |
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Address after: 100176 1st floor, building 8, 11 Kangding street, Beijing Economic and Technological Development Zone, Daxing District, Beijing Patentee after: Sinovision Technology (Beijing) Co.,Ltd. Address before: 100176 floor 1, Yuehong building, No.13, Yongchang North Road, Beijing Economic and Technological Development Zone, Daxing District, Beijing Patentee before: SAINUO WEISHENG TECHNOLOGY (BEIJING) Co.,Ltd. |