CN102397080B - X-ray computerized tomography system and method - Google Patents
X-ray computerized tomography system and method Download PDFInfo
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Abstract
The invention discloses an X-ray computerized tomography system and an X-ray computerized tomography method. The system comprises an X-ray tube, a collimator, a detector, a computing assembly and an adjusting assembly, and is used for shooting a plurality of circular sections of an object to be detected in the scanning direction, wherein the detector comprises a plurality of detector channels; the X-ray tube, the collimator and the detector rotate synchronously around the object to be detected; the collimator is a collimator with an adjustable opening; the computing assembly is used for computing the opening width of the collimator needed for irradiating each circular section respectively, and transmitting the opening width to the adjusting assembly; and the adjusting assembly is used for adjusting the opening of the collimator according to the opening width. The invention further discloses the X-ray computerized tomography method. Due to the adoption of the system and the method, extra exposure of the surrounding area of the objected to be detected can be reduced, and the X-ray dosage received by a patient can be reduced.
Description
Technical field
The present invention relates to medical imaging field, relate in particular to a kind of X-ray computerized tomography system and method.
Background technology
In X ray computer fault imaging (CT) system, Dose Characteristics is very important performance indications.Make the low as far as possible general rule that has become current C T system development of scanning dose.In CT system, measure territory (field of measurement, FOM) be defined as in single rotation sweep, in the process of X-ray tube rotating 360 degrees, object to be checked obtains the transverse cross-sectional area of total radiation, and it has determined the direct scanning dose that object to be checked is applied and the size of x-ray irradiation area.
The phi collimator of the fixing circular FOM of most CT system employing and constant opening (, fan beam collimator) object to be checked is scanned, wherein phi plane is the plane at human body cross section place in frame, this method will be brought the additional radiation to object to be checked peripheral region, although the X ray that human body is now accepted is still within the scope of safe dose, but we always wish do not affecting under the prerequisite of image quality, further reduce the x-ray dose that object to be checked peripheral region receives.As shown in Figure 1, while being spinal column for object to be checked, adopt the phi collimator of fixing circular FOM and constant opening to carry out CT scan, spinal column peripheral region is brought to the schematic diagram of extra exposure.In figure, when the X ray sending when X-ray tube 1 scans a spinal column cross section 13, owing to adopting the fixedly phi collimator 2 of FOM (as shown in border circular areas in figure 3, its diameter is 50cm) and constant opening, thereby bring extra exposure area 4.In fact, if the X ray that the opening of collimator can send X-ray tube according to the difference size of each cross section of object to be checked is adjusted, FOM just can with the A/F synchronization control of collimator, so just can further reduce the extra exposure that object to be checked peripheral region receives.
Pre-defined region of interest based on dynamic collimation device (Region of Interest, ROI) determines that the large submethod of FOM is a kind of prior art, and wherein ROI typically refers to the human region at diseased region place, is equivalent to object to be checked of the present invention.But this method is only to having proposed solution with fixing FOM in single rotation sweep, and do not consider size variation and the change of shape of ROI on scanning direction, wherein scanning direction is the horizontal direction of examinating couch turnover frame in CT system, vertical with phi plane, is generally z direction of principal axis.
Publication number be CN 1446517A Patent Application Publication a kind of X ray data collecting system, it adopts elliptic cross-section or circular cross-section, according to the predicted value of the standard deviation of the desired value of the standard deviation of image, image and the thickness factor, calculate the dose value that sees through the X ray in the axial predetermined angular range of subject to be checked, and be achieved by changing the tube current size of X-ray tube, but do not change the opening of collimator, according to object to be checked, in the size variation of scanning direction, correspondingly do not adjust the exposure area of object to be checked yet.
Summary of the invention
In view of this, the present invention proposes a kind of X-ray computerized tomography system and method, to reduce the extra exposure to object to be checked peripheral region, reduces the x-ray dose that patient accepts simultaneously.
Same claims
Because the present invention adjusts the A/F of collimator according to object to be checked difference size of a plurality of circular cross-sections on scanning direction, form a plurality of circular FOM (being circular cross-section) that covers object to be checked, thereby object to be checked is carried out to tomography X, this has just reduced the extra exposure to object to be checked peripheral region, has reduced the x-ray dose that patient accepts simultaneously.Meanwhile, circular cross-section of the present invention looks like to combine with the location based on profile recognition technology, thereby can according to different objects to be checked, be reduced the best setting of x-ray dose, and the A/F of collimator and the size of circular cross-section are set.Meanwhile, the diameter of circular cross-section of the present invention can also be revised according to the anatomical structure of object to be checked by user (as roentgenology technical staff), thereby further revises the A/F of collimator, avoids the projection of crossing to object to be checked.In addition, because the present invention can adopt dark slide, adjust the opening of collimator, based on existing CT system, easily realize.
Accompanying drawing explanation
Fig. 1, for the phi collimator of fixing circular FOM and constant opening, spinal column is carried out to CT scan in conventional CT scan, brings the schematic diagram of extra exposure to spinal column peripheral region.
Location picture and the outline schematic diagram thereof of spinal column when Fig. 2 lies low for simulation human body, wherein Fig. 2 A is the anteroposterior position location picture of spinal column and the schematic diagram of outline thereof, Fig. 2 B is the side locating image of spinal column and the schematic diagram of outline thereof.
Fig. 3 is respectively the anteroposterior position location picture of Fig. 2 and the external envelope schematic diagram about scanning center's line symmetry that side locating image generates, wherein Fig. 3 A is the external envelope schematic diagram about scanning center's line symmetry for the anteroposterior position location picture generation of Fig. 2 A, and Fig. 3 B is the external envelope schematic diagram about scanning center's line symmetry for the side locating image generation of Fig. 2 B.
Fig. 4 is for obtaining the schematic diagram of projection value of the diameter of each circular cross-section of spinal column according to Fig. 3.
Fig. 5 is for calculating the geometrical relationship schematic diagram of the A/F of collimator according to the projection value of the diameter of a spinal column circular cross-section.
Fig. 6, for spinal column shown in Fig. 1 is scanned with system and method for the present invention, compares the extra exposure schematic diagram that Fig. 1 reduces.
Fig. 7 is the assembly schematic diagram of CT system of the present invention.
Fig. 8 is the composition schematic diagram of the computation module of CT system of the present invention.
Fig. 9 is the flow chart of CT method for imaging of the present invention.
The specific embodiment
For making the object, technical solutions and advantages of the present invention clearer, the present invention is described in more detail by the following examples.
The present invention calculates the A/F of collimator according to object to be checked difference size of a plurality of circular cross-sections on scanning direction, and according to described A/F, adjust the opening of described collimator, thereby object to be checked is carried out to CT scan, to reduce the extra exposure to object to be checked peripheral region, reduce the x-ray dose that patient accepts simultaneously.
In the present invention, object to be checked can be certain region of human body, can be also certain organ or tissue of human body.In embodiments of the invention, object to be checked is spinal column, and scanning direction (being the horizontal direction of examinating couch turnover frame) is z direction of principal axis.Owing at present conventionally adopting phi collimator in CT system, therefore in all embodiment of the present invention, the phi collimator of take describes as example.
CT system of the present invention is used for a plurality of circular cross-sections on scanning direction to spinal column and photographs, the assembly schematic diagram of CT system of the present invention as shown in Figure 7, comprise computation module 30, adjust assembly 31, unshowned X-ray tube and detector in collimator 32 and Fig. 7, X-ray tube wherein, collimator and detector are around spinal column synchronous rotary, detector comprises a plurality of probe access, collimator 32 is the adjustable collimator of an opening, computation module 30 is for calculating the A/F that irradiates respectively the required fan beam collimator of each circular cross-section, and described A/F is sent to and adjusts assembly 31, adjust assembly 31 for adjust the opening of collimator 32 according to described A/F.The collimator 32 is here the adjustable phi collimator of embodiment split shed namely.
Fig. 8 is the composition schematic diagram of the computation module of CT system of the present invention.In Fig. 8, computation module 30 comprises circular cross-section computing module 310 and A/F computing module 320.Wherein circular cross-section computing module 310 for the diameter that calculates respectively each circular cross-section the projection value on detector, and send the projection value of described diameter to A/F computing module 320; A/F computing module 320, for according to the projection value of described diameter, calculates the A/F that irradiates respectively the required fan beam collimator of each circular cross-section, and described A/F is sent to and adjusts assembly 31.Particularly, circular cross-section computing module 310 comprises again number of active lanes computing unit 311 and comparing unit 312.Wherein:
Number of active lanes computing unit 311, for locating picture and side locating image according to the anteroposterior position of spinal column, calculate the probe access number that a plurality of cross sections of spinal column on z direction of principal axis cover respectively on two width location pictures, and send described comparing unit 312 to as width projection value and thickness projection value.
When Fig. 2 has illustrated that object to be checked is spinal column, simulated anteroposterior position location picture and outline and side locating image and the outline thereof of spinal column when human body lies low.Wherein Fig. 2 A is human body while lying low, and X-ray tube irradiates spinal column at 90 degree or 270 degree (being vertical direction), obtains the schematic diagram of anteroposterior position (A.P) the location picture of spinal column.Fig. 2 B is human body while lying low, and X-ray tube irradiates spinal column at 0 degree or 180 degree (being horizontal direction), obtains the schematic diagram of location, side position (Lat) picture of spinal column.The abscissa of this two width figure is all that unit is mm along the axial scanning position of z, the number of active lanes of vertical coordinate for covering on detector, and unit is passage number.Region 16 in this two width figure is spinal column, 18Wei thoracic cavity, region.In addition, in Fig. 2 A, in the outline 19 of the A.P of spinal column 16 location picture and Fig. 2 B, the outline 17 of the Lat location picture of spinal column 16 is all obtained based on profile recognition technology by CT system, compare doctor and according to A.P location picture and Lat location picture, carry out the method for rough estimate spinal column profile, the profile recognition technology of CT system can obtain more accurate spinal column profile, thereby can preferably reduce the extra exposure of X ray to spinal column peripheral region while making spinal column carry out CT scan.
After obtaining the outline 19 of A.P location picture and the outline 17 of Lat location picture of spinal column 16, each cross section that just (1) calculates spinal column 16 on z direction of principal axis according to the following formula probe access number of covering respectively on two width location pictures.
V
AP(z)＝n
AP，U(z)-n
AP，L(z)+1
V
Lat(z)＝n
Lat，U(z)-n
Lat，L(z)+1 (1)
V wherein
aP(z) be width projection value, V
lat(z) be thickness projection value, z is that each cross section of spinal column 16 is at the axial position coordinates of z.As shown in Figure 5, for calculate the geometrical relationship schematic diagram of the A/F of collimator according to the projection value of the diameter of a spinal column circular cross-section.Region 13 in Fig. 5 is the spinal column cross section 13 shown in Fig. 1, and the circular FOM at these spinal column cross section 13 places is circular cross-section 12.Width projection value V
aP(z) be to obtain the number of active lanes that a cross section 13 of spinal column 16 covers on detector on z direction of principal axis, n according to the outline 19 of A.P location picture
aP, Uand n (z)
aP, L(z) be respectively upper end channel number 51 and the lower end channel number 52 of the probe access that covers of this cross section 13.
Comparing unit 312, for more described cross section width projection value and thickness projection value separately, gets the greater in the two as the projection value of described diameter, and sends the projection value of described diameter to A/F computing module 320.
By following formula (2), obtain the projection value of described diameter.
W
E(z)＝max{V
AP(z)，V
Lat(z)} (2)
The function that wherein max is maximizing, W
e(z) be the projection value of described diameter.As can be seen from Figure 5, the width projection value V of spinal column cross section 13
aP(z) > thickness projection value V
lat(z) (although in Fig. 5 the thickness projection value of not shown spinal column cross section 13), so V
aP(z) be the projection value W of the diameter of the circular cross-section 12 corresponding with this cross section 13
e(z), i.e. included passage between channel number 51 and channel number 52, as shown in Reference numeral 14.
In addition, due to the corresponding circular cross-section of each cross section, so the z coordinate at the cross section place z coordinate at the circular cross-section place corresponding with this cross section namely.
Further, circular cross-section computing module 310 comprises again external envelope generation unit 313, be used to anteroposterior position location picture and the side locating image of spinal column to generate respectively one about the external envelope of scanning center's line symmetry, and using the external envelope that anteroposterior position is located picture as described anteroposterior position location, look like, the external envelope of side locating image sends number of active lanes computing unit 311 to as described side locating image.
As shown in Figure 2, be the anteroposterior position location picture of spinal column and the schematic diagram of outline and side locating image and outline thereof thereof.Because anteroposterior position location is not necessarily symmetrical about scanning center's line as outline and side locating image outline, as shown in Figure 2 B, the outline 17 of the side locating image of spinal column is not symmetrical about scanning center's line (as shown in the chain-dotted line in Fig. 2 B), in Fig. 2 A, the outline 19 of the anteroposterior position of spinal column location picture is roughly symmetrical about scanning center's line (as shown in the chain-dotted line in Fig. 2 A), and the X-ray beam that X-ray tube sends is conventionally symmetrical about scanning center's line, so when the X-ray beam about scanning center's line symmetry scans object to be checked as shown in Figure 2 B, will cause the peripheral region of a part of object to be checked to accept the extra exposure of X ray, another part object to be checked still has sub-fraction not receive the exposure of X ray.Therefore be necessary for anteroposterior position location picture and side locating image and generate respectively one about the external envelope of scanning center's line symmetry.This symmetrical external envelope can realize by external envelope function or the program of CT system, can more completely comprise object to be checked.
External envelope generation unit 313 is respectively the anteroposterior position location picture of Fig. 2 and the external envelope about scanning center's line symmetry of side locating image generation as shown in Figure 3.Wherein Fig. 3 A is the external envelope schematic diagram about scanning center's line symmetry for the anteroposterior position location picture generation of Fig. 2 A, and Fig. 3 B is the external envelope schematic diagram about scanning center's line symmetry for the side locating image generation of Fig. 2 B.The abscissa of Fig. 3 A and 3B is all that unit is mm along the axial scanning position of z, and vertical coordinate is all the number of active lanes covering on detector, and unit is passage number.The dotted line of Fig. 3 A is that CT system is the external envelope B about scanning center's line symmetry of the anteroposterior position location picture generation of spinal column
aP, the dotted line of Fig. 3 B is that CT system is the external envelope B about scanning center's line symmetry of the side locating image generation of spinal column
lat.
Then, external envelope generation unit 313 is located anteroposterior position the external envelope B of picture
aPexternal envelope B as described anteroposterior position location picture, side locating image
aPas described side locating image, send number of active lanes computing unit 311 to.
Number of active lanes computing unit 311 calculates according to the anteroposterior position location picture from external envelope generation unit 313 and side locating image the probe access number that each cross section covers respectively on two width location pictures, and sends described comparing unit 312 to as width projection value and thickness projection value.Comparing unit 312 according to formula (2) relatively width projection value and thickness projection value result as shown in Figure 4, for obtain the schematic diagram of projection value of the diameter of each circular cross-section of spinal column according to Fig. 3.Wherein abscissa is along the axial scanning position of z, and unit is mm, the number of active lanes of vertical coordinate for covering on detector, and unit is passage number, the projection value W of the diameter of the circular cross-section that solid line is spinal column on detector
e(z), dotted line is the external envelope B of spinal column anteroposterior position location picture
aP, dotted line is the external envelope B of spinal column side locating image
lat.Width projection value V when spinal column cross section
aP(z) > thickness projection value V
lat(z) time, the projection value curve W of diameter
e(z) get the external envelope B of anteroposterior position location picture in external envelope generation unit 313
aP, as the width projection value V of spinal column cross section
aP(z) < thickness projection value V
lat(z) time, the projection value W of diameter
e(z) curve is got the external envelope B of side locating image in external envelope generation unit 313
lat.In Fig. 4, just illustrating intuitively W
e(z) plots changes and B
aPor B
latunanimously, in fact according to formula (2) W
e(z) should with B
aPwidth projection value V
aPor B (z)
latthickness projection value V
lat(z) equate, but in diagram, can cause these three curves clearly to distinguish, therefore here only to W
e(z) plots changes illustrates.
A/F computing module 320, for according to the projection value of the diameter of described comparing unit 312, calculates the A/F that irradiates respectively the required fan beam collimator of each circular cross-section, and described A/F is sent to and adjusts assembly 31.
In Fig. 5, illustrated to calculate according to the projection value of the diameter of a spinal column circular cross-section geometrical relationship of the A/F of collimator.A/F computing module 320 is first according to W
e(z) by following formula (3), calculate the X ray fan beam angle β that irradiates circular cross-section 12
open(z).
Wherein, β
open(z) be described X ray fan beam angle, as shown in the angle 7 in Fig. 5, N is the total number of channels of detector 5, and β is the fan-shaped angle of the maximum of X-ray beam, and as shown in the angle 6 in Fig. 5, it covers N passage of detector.
Then, A/F computing module 320 is again according to β
open(z) by following formula (4), calculate the A/F W of phi collimator 21
open(z).
W
open(z)＝β
open(z)·D
fc (4)
As shown in Figure 5, wherein, D
fcthe distance 9 from the focus of X-ray tube to phi collimator, W
open(z) be the A/F 8 of phi collimator 21.Certainly the A/F of phi collimator also can calculate with additive method, but the method that the present invention proposes is comparatively simple.
Further, computation module 30 also comprises correcting module 330, for according to the X ray fan beam angle β of A/F computing module 320
open(z) calculate the diameter D of circular cross-section 12
fOM(z), and by this diameter D
fOM(z) and with the Breadth Maximum of the corresponding cross section 13 of this circular cross-section 12 in anatomical structure compare, according to comparative result, revise the A/F of phi collimator 21, and the A/F of correction is sent to and adjusts assembly 31.
As shown in Figure 5, wherein, D
f0it is the distance 10 from the focus of X-ray tube 1 to scanning center.D
fOM(z) be the size of the diameter of circular cross-section 12.Certain D
fOM(z) also can calculate with additive method, but the method that the present invention proposes is comparatively simple.
Then, correcting module 330 is again by diameter D
fOM(z) and with the Breadth Maximum of the corresponding cross section 13 of this circular cross-section 12 in anatomical structure compare, and according to comparative result, revise the A/F W of phi collimator 21
open(z).If D
fOM(z) be greater than described Breadth Maximum, according to described Breadth Maximum, reduce D
fOM(z), and correspondingly reduce A/F W
open(z), to avoid projection; If D
fOM(z) be less than described Breadth Maximum, according to described Breadth Maximum, increase D
fOM(z), and correspondingly increase A/F W
open(z), to cover this circular cross-section 12 completely.After aforesaid operations, obtain the A/F W ' of phi collimator correction
open(z), and by W '
open(z) send to and adjust assembly 31.
Next the adjustment assembly in Fig. 7 31 is just according to the A/F W ' of the correction from computation module 30
open(z) adjust the opening of collimator 32.Preferably, collimator 32 comprises plurality of vanes, and the spacing of described blade is adjustable, so just can be according to W '
open(z) by adjustment assembly, directly adjusted the spacing of the blade of phi collimator.But this design has changed original design of phi collimator, more complicated in implementation.
Alternately, the present inventor proposes a kind of design that increases dark slide on collimator, according to W '
open(z) thus by adjusting assembly, adjust dark slide and reach the object of adjusting collimator opening.Because phi collimator in prior art is constant opening, the present invention only need cover its part opening by dark slide, can reach the object that changes its A/F.The adjustable design of collimator blade is compared in this design, owing to not needing to change original design of collimator simpler in implementation, also provide cost savings.
Adjust assembly according to W '
open(z) adjust in the following manner dark slide: when a certain circular cross-section is scanned, can select a large opening of phi collimator in conventional CT system, it can expose completely to this circular cross-section, then adjust assembly according to the W ' receiving
open(z) adjust dark slide, thereby the part opening that makes dark slide cover phi collimator reaches the object that changes phi collimator A/F, along with the examinating couch of CT system moves to frame direction, adjust assembly and receive next A/F W '
open(z
0) (z
0position coordinates for next circular cross-section), then according to W '
open(z
0) adjust dark slide, if W '
open(z
0) < W '
open(z), make dark slide move towards the direction that phi collimator A/F is diminished, if W '
open(z
0) > W '
open(z), make dark slide move towards making phi collimator A/F become large direction, so just realized adjustment assembly and according to the A/F of the correction from computation module, adjusted the object of the opening of collimator.
Adjust assembly 31 further also for adjusting the folding speed of the opening of collimator 32.
In actual mechanical process, the folding speed of phi collimator opening also can have influence on the size of actual circular cross-section and the actual extra exposure reducing number.No matter change the A/F of phi collimator by dark slide or the direct spacing of adjusting blade, the folding speed of phi collimator opening all will match with the speed of rotation of X-ray tube and the stepping of examinating couch, could farthest reduce extra exposure like this.If the speed of rotation when X-ray tube is that 1s/ turns, when each tomoscanning sick bed stepping is 1mm, adopt system of the present invention to carry out CT scan to cervical region, it is slow that the folding speed that can find phi collimator opening is compared folding speed soon, the extra exposure that can reduce more, what but this minimizing neither no maximum, after the folding speed of phi collimator opening reaches a special speed, extra exposure no longer continues to reduce.If the speed of rotation when X-ray tube is that 1s/ turns, each tomoscanning sick bed stepping is 1mm, when object to be checked is cervical region, when the folding speed of phi collimator opening reaches 4mm/s, then continues to increase folding speed, and has just no longer reduced in extra exposure region.In practical operation, adjust assembly and first will obtain the folding speed of phi collimator opening and the relation between the extra exposure of minimizing, then according to this relation and the extra exposure that needs to reduce, adjust the folding speed of phi collimator opening.This has guaranteed to reduce largely extra exposure, lower to the mechanical performance requirement of CT system again, is unlikely to too much to increase the cost of system.
The present invention also provides a kind of X ray computer tomography method, described method to spinal column a plurality of circular cross-sections on scanning direction photograph, be illustrated in figure 9 the flow chart of CT method for imaging of the present invention, comprise step 701-704.
In this step, described at number of active lanes computing unit 311, after obtaining the outline of A.P location picture and the outline of Lat location picture of spinal column, according to formula (1), calculate each cross section of spinal column on z direction of principal axis and at two width, locate the probe access number covering respectively on the outline of pictures, obtain width projection value V
aPand thickness projection value V (z)
lat(z).Step 702, relatively the width projection value V of each cross section
aPand thickness projection value V (z)
lat(z), get the greater in the two as the projection value W of the diameter of this circular cross-section
e(z).
In this step, can obtain by formula (2) the projection value W of the diameter of circular cross-section
e(z).
In this step, can calculate according to formula (3) (4) A/F of phi collimator.
Described adjustment comprises: by changing the spacing of blade of described collimator or the dark slide being added on collimator, adjust described opening.In the adjustment assembly 31 of CT system of the present invention, understand specifically these two kinds of adjustment modes, repeat no more here.
Step 704 also further comprises the folding speed of the opening of adjusting phi collimator.
Here, first obtain the folding speed of phi collimator opening and the relation between the extra exposure of minimizing, then according to this relation and the extra exposure that needs to reduce, adjust the folding speed of the opening of phi collimator.This is existing illustrating in the adjustment assembly 31 of CT system of the present invention, repeats no more here.
Further, CT method for imaging of the present invention also comprises step 705, for anteroposterior position location picture and the side locating image of spinal column generates respectively one about the external envelope of scanning center's line symmetry, as shown in Figure 3, and anteroposterior position is located to the external envelope B of picture
aPexternal envelope B as described anteroposterior position location picture, side locating image
latas described side locating image.
In the external envelope generation unit 313 of CT system of the present invention, illustrated that the two width location pictures for spinal column generate reason and the effect about the external envelope of scanning center's line symmetry, repeat no more here.In this step, the anteroposterior position location picture that CT system is spinal column by an external envelope function or program generates an external envelope about scanning center's line symmetry, for spinal column side locating image also generates the external envelope of Guan Yigeyu scanning center line symmetry, and anteroposterior position is located to the external envelope B of picture
aPexternal envelope B as described anteroposterior position location picture, side locating image
latas described side locating image.
Further, CT method for imaging of the present invention also comprises step 706.
In this step, can calculate by formula (5) the diameter D of circular cross-section 12
fOM(z).Certain D
fOM(z) also can calculate with additive method, but the method that the present invention proposes is comparatively simple.The A/F of how revising phi collimator according to comparative result has been described in the correcting module 330 of CT system of the present invention, has repeated no more here.
With system and method for the present invention, object to be checked is carried out to tomoscan, can greatly reduce the extra exposure to object to be checked peripheral region.When Fig. 6 scans spinal column cross section 13 for employing system and method for the present invention, the schematic diagram of the extra exposure of minimizing.In figure, CT system precomputes the A/F of phi collimator 21 according to spinal column cross section 13, thereby correspondingly adjust the opening of collimator 21 to scan, so compare the prior art shown in Fig. 1, system and method of the present invention can reduce extra exposure region 42, has also just reduced the x-ray dose that region 42 is accepted.
The foregoing is only preferred embodiment of the present invention, in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
Claims (12)
1. an X-ray computerized tomography system that comprises X-ray tube, collimator and detector, being used for a plurality of circular cross-sections on scanning direction to object to be checked photographs, described detector comprises a plurality of probe access, described X-ray tube, collimator and detector rotate around object synchronization to be checked, it is characterized in that, described collimator is the adjustable collimator of an opening, and described system also comprises computation module and adjustment assembly, wherein
Described computation module, for calculating the A/F that irradiates respectively the required collimator of each circular cross-section, and sends described A/F to described adjustment assembly;
Described adjustment assembly, for adjusting the opening of described collimator according to described A/F;
Described computation module comprises circular cross-section computing module and A/F computing module, wherein
Described circular cross-section computing module, the projection value for the diameter that calculates respectively each circular cross-section on detector, and send the projection value of described diameter to described A/F computing module;
Described A/F computing module, for according to the projection value of described diameter, calculates and irradiates respectively the A/F of the required collimator of each circular cross-section, and send described A/F to described adjustment assembly;
Described circular cross-section computing module comprises number of active lanes computing unit and comparing unit, wherein
Described number of active lanes computing unit, for locating picture and side locating image according to the anteroposterior position of object to be checked, calculate the probe access number that a plurality of cross sections of object to be checked on scanning direction cover respectively on two width location pictures, and send described comparing unit to as width projection value and thickness projection value;
Described comparing unit, for more described cross section width projection value and thickness projection value separately, gets the greater in the two as the projection value of the diameter of described circular cross-section, and sends the projection value of described diameter to described A/F computing module.
2. system according to claim 1, is characterized in that, described circular cross-section computing module further comprises:
External envelope generation unit, be used to anteroposterior position location picture and the side locating image of object to be checked to generate respectively one about the external envelope of scanning center's line symmetry, and using the external envelope that anteroposterior position is located picture as described anteroposterior position location, look like, the external envelope of side locating image sends described number of active lanes computing unit to as described side locating image.
3. system according to claim 1, is characterized in that, described computation module further comprises:
Correcting module, for receiving the A/F of described A/F computing module, calculate the diameter of described circular cross-section, and the Breadth Maximum in the anatomical structure of this circular cross-section compares by described diameter and object to be checked, according to comparative result, revise described A/F, and send the A/F of correction to described adjustment assembly.
4. system according to claim 1, is characterized in that, described collimator comprises plurality of vanes, and the spacing of described blade is adjusted by adjusting assembly.
5. system according to claim 1, is characterized in that, described collimator comprises dark slide, and described dark slide is adjusted by adjusting assembly.
6. system according to claim 1, is characterized in that, described adjustment assembly is further used for adjusting according to the relation between the folding speed of described collimator opening and the extra exposure of minimizing the folding speed of described opening.
7. an X ray computer tomography method, described method to object to be checked a plurality of circular cross-sections on scanning direction photograph, comprise the steps:
Calculate the A/F that irradiates respectively the required collimator of each circular cross-section;
According to described A/F, adjust the opening of described collimator;
Described calculating A/F comprises:
The projection value of the diameter that calculates respectively each circular cross-section on detector;
According to the projection value of described diameter, calculate the A/F that irradiates respectively the required collimator of each circular cross-section;
The projection value of described calculated diameter comprises:
According to the anteroposterior position location picture of object to be checked, calculate respectively the probe access number that a plurality of cross sections of object to be checked on scanning direction cover, obtain a plurality of width projection values, according to the side locating image of object to be checked, calculate respectively the probe access number that described cross section covers, obtain a plurality of thickness projection values;
More described cross section width projection value and thickness projection value separately, gets the greater in the two as the projection value of the diameter of described circular cross-section.
8. method according to claim 7, is characterized in that, the projection value of described calculated diameter further comprises:
For anteroposterior position location picture and the side locating image of object to be checked generates respectively one about the external envelope of scanning center's line symmetry, the external envelope that anteroposterior position is located to picture looks like as described anteroposterior position location, the external envelope of side locating image is as described side locating image.
9. method according to claim 7, is characterized in that, calculates the A/F of described collimator according to following formula,
Wherein, z is the position coordinates of a circular cross-section on scanning direction, W
open(z) be the A/F of described collimator, W
e(z) be the projection value of the diameter of this circular cross-section, the total number of channels that N is detector, β is for covering the X ray fan beam angle of N probe access, D
fcfor the distance of X-ray tube focus to described collimator.
10. method according to claim 7, is characterized in that, described calculating A/F further comprises:
Calculate the diameter of described circular cross-section, and the Breadth Maximum in the anatomical structure of this circular cross-section compares by described diameter and object to be checked, according to comparative result, revises described A/F.
11. methods according to claim 7, is characterized in that, described adjustment comprises: by changing the spacing of blade of described collimator or the dark slide being added on described collimator, adjust described opening.
12. methods according to claim 7, is characterized in that, described adjustment further comprises the folding speed of adjusting described opening according to the relation between the folding speed of described collimator opening and the extra exposure of minimizing.
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| CN102783960A (en) * | 2012-08-24 | 2012-11-21 | 北京东方惠尔图像技术有限公司 | Beam limitation adjusting device and beam limitation adjusting method of rays and imaging device |
| CN108022272B (en) * | 2016-10-28 | 2021-12-21 | 卡尔蔡司X射线显微镜公司 | Computer program and CT system for segmentation and spectrum based metal artifact reduction |
| CN107928693B (en) * | 2017-11-29 | 2020-12-11 | 上海联影医疗科技股份有限公司 | Method and system for determining opening position of collimator of imaging device |
| CN111887883A (en) * | 2019-05-05 | 2020-11-06 | 有方（合肥）医疗科技有限公司 | X-ray imaging apparatus and X-ray imaging method |
| CN116018181A (en) * | 2020-08-21 | 2023-04-25 | 上海联影医疗科技股份有限公司 | System and method for dynamic multi-leaf collimator tracking |
| CN111956249B (en) * | 2020-09-07 | 2024-02-02 | 上海联影医疗科技股份有限公司 | Mammary gland X-ray scanning equipment and scanning method |
| CN117084706A (en) * | 2023-10-07 | 2023-11-21 | 北京富通康影科技有限公司 | Three-source CT-based locating plate scanning and 3D contour estimation method thereof |
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