CN111714789B - Multi-blade grating and manufacturing method of grating blade thereof - Google Patents
Multi-blade grating and manufacturing method of grating blade thereof Download PDFInfo
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Abstract
The embodiment of the invention discloses a multi-leaf grating and a manufacturing method of a grating leaf thereof, wherein the multi-leaf grating comprises the following components: the grating structure comprises 2 blade groups distributed along a first direction, wherein each blade group comprises M grating blades which are arranged in a stacked mode, and each grating blade comprises a main body part and a penumbra reduction part which are connected along the first direction; the penumbra reduction part comprises an arc-shaped branch part and a rectangular branch part connecting the arc-shaped branch part and the main body part, the maximum size of the arc-shaped branch part is equal to that of the rectangular branch part in a second direction perpendicular to the first direction, the size of the rectangular branch part is larger than that of the main body part, the first direction and the second direction are parallel to the surface of the grating blade, and the arc-shaped branch parts of the two grating blades in different blade groups are oppositely arranged. In the embodiment of the invention, under the condition of equal field penumbra, the cost is saved and the volume of the whole machine is reduced; under the condition of the same volume of the whole multi-leaf grating, the field penumbra can be reduced.
Description
Technical Field
The embodiment of the invention relates to a multi-leaf grating technology, in particular to a multi-leaf grating and a grating leaf manufacturing method thereof.
Background
Multi-leaf gratings are important components of radiotherapy apparatus to deliver beam projection, and are used in dynamic therapy. Compared with static intensity modulated radiotherapy technology, the dynamic intensity modulated radiotherapy technology (including IMRT \ VMAT and the like) has obvious advantages, can improve the dose distribution level in the body of a patient, effectively reduces the radiation dose to important organs and healthy tissues, and further improves the treatment quality.
In practice, a multileaf grating presents a penumbra region. When the ray intensity emitted by the light source passes through the grating blade to reach the penumbra region, the ray intensity is attenuated by less than 80%, so that the tissues in the penumbra region can be damaged by ray radiation, and the tissues in the penumbra region are not expected to be irradiated by the light source, so that the existence of the penumbra region causes other tissues to be damaged by additional radiation. The existence of the penumbra area of the multi-leaf grating is inevitable, so the influence of the penumbra is eliminated as much as possible in design, and the smaller the penumbra area of the multi-leaf grating, namely the smaller the field penumbra, the better.
At present, through the height of increase grating blade, reduce the field penumbra of multi-leaf collimator, but this blade design can cause the whole volume increase of multi-leaf collimator, is unfavorable for the installation.
Disclosure of Invention
The embodiment of the invention provides a multi-leaf grating and a manufacturing method of a grating leaf thereof, which aim to reduce a field penumbra under the same volume of the multi-leaf grating.
The embodiment of the invention provides a multi-leaf grating, which comprises: the grating blade comprises a main body part and a penumbra reduction part which are connected along the first direction;
the penumbra-reducing section comprises an arc-shaped section and a rectangular section connecting the arc-shaped section and the main body section, the maximum size of the arc-shaped section is equal to that of the rectangular section in a second direction perpendicular to the first direction, the size of the rectangular section is larger than that of the main body section, the first direction and the second direction are both parallel to the surface of the grating blade, and the arc-shaped sections of two grating blades in different blade groups are arranged oppositely.
Furthermore, two resistance wires are mounted on the upper end surface of the grating blade along the second direction, first ends of the two resistance wires extend to the side end surface of the penumbra reduction part and are electrically connected, and second ends of the two resistance wires extend to the edge of the main body part and are disconnected;
the multileaf grating further comprises: the position detection mechanism is arranged corresponding to the blade group and comprises a circuit board and M detection units positioned on the circuit board, the circuit board penetrates through the space between two resistance wires of any one grating blade in the blade group, the M detection units and the M grating blades are respectively arranged corresponding to each other, and the detection units are used for detecting electric signals of the two resistance wires contacting with the detection units so as to determine the positions of the corresponding grating blades.
Further, the detection unit comprises a first electric brush positioned on the upper surface of the circuit board and a second electric brush positioned on the lower surface of the circuit board, the first electric brush is in electrical contact with a resistance wire positioned on the first electric brush, and the second electric brush is in electrical contact with a resistance wire positioned below the second electric brush.
Further, the position detection mechanism further includes: the blade track frame is arranged corresponding to the blade group, and the main body part of the grating blade in the blade group penetrates through the corresponding blade track frame;
the upper surface of blade track frame with the up end is adjacent has the opening, the opening is used for holding the circuit board, the upper surface of blade track frame has been seted up and has been run through the opening just follows a M through-hole group of first direction, one the through-hole group includes the edge 2 through-holes that the second direction was arranged, one 2 through-holes and one of through-hole group two resistance wires of grating blade correspond the setting, just the resistance wire passes correspondingly the through-hole.
Furthermore, the resistance wire is a nichrome wire.
Further, still include: a blade driving motor provided corresponding to the blade group; the blade driving mechanism comprises M driving motors, the M driving motors and the M grating blades are respectively and correspondingly arranged, and the driving motors are used for driving the main body parts of the corresponding grating blades to move in the blade track frame.
Based on the same inventive concept, the embodiment of the invention also provides a method for manufacturing the grating blade of the multi-blade grating, and the multi-blade grating is as described above;
the grating blade manufacturing method comprises the following steps:
calculating the number of half-layer values required by the selected blade material according to the required specification parameters of the ray leakage rate of the grating blade, and determining the height of the main body part along the second direction;
and calculating the coordinate value, the height and the arc of the arc-shaped branch of the rectangular branch in the penumbra reduction part.
Further, the air conditioner is characterized in that,
h2＝h1+w1+w2；
h2 is the height of the rectangular section, h1 is the height of the body section, w1 is the blade upper ramp thickness, and w2 is the blade lower ramp thickness.
Further, the multileaf grating comprises a light source;
calculating coordinate values of rectangular subsections in the penumbra subtraction part comprises:
establishing a plane rectangular coordinate system, wherein the origin of coordinates of the plane rectangular coordinate system is the light source, and the transverse axis of the plane rectangular coordinate system is parallel to the first direction and the longitudinal axis of the plane rectangular coordinate system is parallel to the second direction;
forming a first straight line passing through the origin of coordinates, wherein an included angle between the first straight line and the longitudinal axis is a first side beam maximum opening angle and is tangent to the arc of the arched subsection of the grating blade;
forming a second line through the origin of coordinates, the first end of the second line being located on a first side of the body portion of the grating blade and the second end being located on the arc of its arcuate subsection, the first end and the second end being spaced apart by a distance equal to the height of the body portion;
determining as a vertex of the rectangular segment an intersection of a third line passing through the first end point and a fourth line passing through the first start of the arcuate segment arc, the third line being parallel to the longitudinal axis and the fourth line being parallel to the transverse axis, the first start of the arcuate segment arc being immediately adjacent to the second end point.
Further, the grating blade is entirely located on the left side of the longitudinal axis, and the first edge of the main body portion is the lower edge thereof; alternatively, the first and second electrodes may be,
the grating blade intersects the longitudinal axis and the first edge of the body portion is an upper edge thereof.
In an embodiment of the invention, the grating blade is geometrically divided into a body portion and a penumbra-reducing portion, the penumbra-reducing portion comprising an arcuate section and a rectangular section connecting the arcuate section and the body portion, the maximum dimension of the arcuate section being equal to the dimension of the rectangular section in a second direction perpendicular to the first direction, the dimension of the rectangular section being greater than the dimension of the body portion. According to the grating blade provided by the embodiment of the invention, under the condition of the same field penumbra, the height of the main body part is reduced, so that the overall volume of the grating blade is reduced to save the cost, and the overall volume of the multi-leaf grating can be reduced; under the condition of the same overall volume of the multi-leaf grating, the increased height of the front side of the grating blade does not additionally occupy the overall space of the multi-leaf grating, and meanwhile, the increased height of the front side of the grating blade can also reduce the field penumbra and improve the treatment accuracy of the multi-leaf grating.
Drawings
To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief description will be given below of the drawings required for the embodiments or the technical solutions in the prior art, and it is obvious that the drawings in the following description, although being some specific embodiments of the present invention, can be extended and extended to other structures and drawings by those skilled in the art according to the basic concepts of the device structure, the driving method and the manufacturing method disclosed and suggested by the various embodiments of the present invention, without making sure that these should be within the scope of the claims of the present invention.
FIG. 1 is a schematic diagram of a multi-leaf grating according to an embodiment of the present invention;
FIG. 2 is a schematic view of a blade assembly;
FIG. 3 is a schematic view of the movement of the light source and the grating blade;
FIG. 4 is a schematic illustration of a penumbra region of a grating blade;
FIG. 5 is a schematic illustration of a prior art grating blade;
FIG. 6 is a schematic view of the resistance wire of the grating blade;
FIG. 7 is a schematic diagram of a multileaf grating;
FIG. 8 is a schematic view of a circuit board in the position sensing mechanism;
FIG. 9 is a schematic view of the assembly of the circuit board and the grating blade;
FIG. 10 is a schematic view of the assembly of the circuit board and the grating blade;
FIG. 11 is a schematic illustration of a method of fabricating a grating blade of a multi-leaf grating according to an embodiment of the present invention;
FIG. 12 is a schematic diagram of the calculation of the rectangular section provided by the embodiment of the present invention;
FIG. 13 is a schematic diagram illustrating the calculation of the vertex coordinates of the rectangular section according to an embodiment of the present invention;
FIG. 14 is a schematic diagram illustrating the calculation of the vertex coordinates of the rectangular section according to the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described through embodiments with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the basic idea disclosed and suggested by the embodiments of the present invention, are within the scope of the present invention.
Referring to fig. 1, a schematic diagram of a multi-leaf grating according to an embodiment of the present invention is shown, and fig. 2 is a schematic diagram of a leaf group. The multileaf grating of the present embodiment includes: the grating blade assembly comprises 2 blade groups 1 arranged along a first direction Y, wherein each blade group 1 comprises M grating blades 11 arranged in a stacked mode, and each grating blade 11 comprises a main body part 12 and a penumbra reduction part 13 which are connected along the first direction Y; the penumbra-reducing section 13 includes an arcuate section 13a and a rectangular section 13b connecting the arcuate section 13a and the body section 12, the maximum dimension H1 of the arcuate section 13a being equal to the dimension H1 of the rectangular section 13b in a second direction Z perpendicular to the first direction Y, the dimension H1 of the rectangular section 13b being greater than the dimension H2 of the body section 12, the first direction Y and the second direction Z being both parallel to the surface of the grating blade 11, the arcuate sections 13a of two grating blades 11 located in different blade groups 1 being disposed opposite each other.
In this embodiment, the multi-leaf grating includes 2 leaf sets 1 and the arcuate sections 13a of the 2 leaf sets 1 are disposed opposite to each other. In the multi-leaf grating, 1 blade group 1 includes M grating blades 11 arranged in a stacked manner, and M selectable grating blades 11 are arranged in a stacked manner along a third direction X, where the third direction X is perpendicular to the surface of the grating blade 11. In other embodiments, it is also possible to choose a multileaf grating comprising two leaf sets, each set having 2 leaf sets with arcuate sections disposed opposite each other.
The grating blade 11 is a unitary structure, and different areas of the grating blade are different in shape, and the structure of the specific grating blade 11 can be geometrically divided into a main body portion 12 and a penumbra-reducing portion 13 along the first direction Y. The penumbra-reducing section 13 may be divided into an arcuate section 13a and a rectangular section 13b connecting the arcuate section 13a and the main body section 12, wherein the arcuate section 13a is of an outwardly convex shape, and the outwardly convex end faces of the arcuate sections 13a of the two grating blades 11 located in different blade groups 1 are disposed opposite to each other. It is to be understood that the rectangular, arcuate, etc. shapes described herein are the conclusion of viewing the grating blade surface in front of the side of the grating blade that is perpendicular to the surface as the end face of the grating blade.
The multi-leaf grating is an important executive component for beam projection of the radiotherapy equipment, and the main function of the multi-leaf grating is to form a field with a shape required by treatment through independent movement of each grating leaf, wherein the smaller the penumbra of the field is, the better the penumbra of the field is. In this embodiment, the side where the bow-shaped part 13a of the grating blade 11 is located is defined as the front side of the grating blade 11, and the tail of the main body 12 of the corresponding grating blade 11 is defined as the rear side of the grating blade 11, so that the front end surface of the grating blade 11 is the convex end surface of the bow-shaped part 13a, and the arc shape thereof can ensure the consistency of the field penumbra at different positions of the grating blade, and meanwhile, the special design of the blade profile reduces the field penumbra, and improves the use effect of the multi-leaf grating in clinic.
Specifically, the field penumbra principle of the multi-leaf grating is as follows. As shown in fig. 3, no penumbra problem exists if the multi-leaf collimator satisfies two conditions, which are 1) that the light source 101 is a point light source; 2) during the movement, the front end face of the grating blade 100 completely coincides with the edge ray, for example, the grating blade 100 completely coincides with the edge ray 102a when moving to the a position, and the grating blade 100 completely coincides with the edge ray 102b when moving to the b position.
However, in practice, a multileaf grating cannot satisfy two conditions because: 1) point sources do not exist in the real world, and any light source has a certain size and geometry, so the light source shown in fig. 3 is essentially an X-ray source; 2) the condition that the front end face of the grating blade is overlapped with the edge ray requires that the grating blade does circular arc motion or equivalent compound motion, which is a scheme which can not be realized almost under the application condition of the linear accelerator, and most grating blades only do linear motion in practice.
Therefore, the multi-leaf grating has a field penumbra, and it can be understood that the smaller the field penumbra of the multi-leaf grating is, the better the field penumbra is. In order to reduce the influence of the field penumbra, the front end surface of the grating blade is often shaped like an arc.
As shown in fig. 4, two sides of the light emitted from the light source 101 are tangent to the arcs of the front end surfaces of the two grating blades 100, a full-bright area 103 is located inside the two tangent lines, and the full-bright area 103 corresponds to a treatment area, i.e., a focus area, in clinical practice. The external ray intensities of the two tangents gradually attenuate with the increase of the ray passing through the thickness of the grating blade 100, the area with the ray intensity attenuation less than 80% is defined as a penumbra area 104, the area outside the penumbra area 104 is defined as a whole-dark area 105, and the area with the ray intensity attenuation more than 80% is defined as a whole-dark area 105. Clinically, when the intensity of the radiation emitted by the light source 101 reaches the dark area 105 through the grating blade 100, the intensity is attenuated by more than 80%, so that the tissues in the dark area 105 are hardly damaged by the radiation; when the intensity of the radiation emitted by the light source 101 reaches the penumbra region 104 through the grating blade 100, the intensity is attenuated by less than 80%, so that the tissue in the penumbra region 104 is damaged by the radiation, and the tissue in the penumbra region 104 is not expected to be irradiated by the light source 101. Based on this, the presence of the penumbra region 104 may cause additional radiation damage to other tissues, which may have a more adverse effect on the human body if the damaged tissue is a vital organ or sensitive tissue.
The size of the penumbra region 104 in the X direction is defined herein as the field penumbra. Since the existence of the penumbra of the multileaf grating is unavoidable, the influence of the penumbra should be eliminated as much as possible in design, and the smaller the penumbra area of the multileaf grating, i.e., the smaller the field penumbra, the better.
In this embodiment, the maximum dimension H1 of the arcuate section 13a is equal to the dimension H1 of the rectangular section 13b in a second direction Z perpendicular to the first direction Y, the dimension H1 of the rectangular section 13b being greater than the dimension H2 of the body portion 12, both the first direction Y and the second direction Z being parallel to the surface of the grating blade 11. The height is increased only at the front portion of the grating blade 11, and the field penumbra can be reduced as viewed from the field penumbra, equivalent to the increase in the overall height of the grating blade 11. In the prior art, the whole height of the blade needs to be increased to achieve the same field penumbra effect. The dimension of the grating blade in the second direction Z may be defined herein as the height of the grating blade.
Fig. 5 shows a grating blade provided in the prior art, in which the overall height of the grating blade 100 is kept uniform and equal to H1. Referring to fig. 1, the present embodiment provides a grating blade 11 having a maximum height of the arcuate section 13a equal to H1, a body portion 12 having a height H2, and H2 less than H1. The grating blade 11 shown in fig. 1 and the grating blade 100 shown in fig. 3 can achieve the same field penumbra.
Based on this, the material of grating blade is mostly the tungsten alloy, and this raw and other materials are very expensive, and under the condition of equal field penumbra, compared with prior art, the grating blade 11 that this embodiment provided is small, has practiced thrift the cost from the material. Under the condition of the same field penumbra, the height of the front side of the grating blade 11 provided by the embodiment is equal to that of the existing grating blade, and the height of the main body part 12 of the grating blade 11 provided by the embodiment is smaller than that of the existing grating blade, so that the overall volume of the grating blade 11 in the embodiment is reduced, and the overall volume of the multi-leaf grating can be reduced. Under the condition of the same complete volume of the multi-leaf collimator, the height is only increased on the front side of the collimator blade 11 in the embodiment, the increased height does not additionally occupy the complete machine space of the multi-leaf collimator, and the increased height can reduce the field penumbra of the collimator blade 11.
Therefore, the multi-leaf grating provided by the embodiment can be applied to a linear accelerator treatment head, the installation space of the multi-leaf grating on the linear accelerator treatment head can be saved under the condition of the same field penumbra, or the field penumbra of the multi-leaf grating in the linear accelerator treatment head can be reduced under the condition of the same installation space, and the reduction of the field penumbra means that the treatment is more accurate and has great significance for clinic. It should be noted that, according to the actual simulation estimation, the field penumbra of the grating blade 11 according to the present embodiment is reduced by about 50% compared to the conventional grating blade under the condition of the same height of the main body portion (for example, H2).
In an embodiment of the invention, the grating blade is geometrically divided into a body portion and a penumbra-reducing portion, the penumbra-reducing portion comprising an arcuate section and a rectangular section connecting the arcuate section and the body portion, the maximum dimension of the arcuate section being equal to the dimension of the rectangular section in a second direction perpendicular to the first direction, the dimension of the rectangular section being greater than the dimension of the body portion. According to the grating blade provided by the embodiment of the invention, under the same field penumbra condition, the height of the main body part is reduced, so that the overall volume of the grating blade is reduced to save cost, and the overall volume of a multi-leaf grating can be reduced; under the condition of the same overall volume of the multi-leaf grating, the increased height of the front side of the grating blade does not additionally occupy the overall space of the multi-leaf grating, and meanwhile, the increased height of the front side of the grating blade can also reduce the field penumbra and improve the treatment accuracy of the multi-leaf grating.
For example, on the basis of the above technical solution, as shown in fig. 6 to 10, two resistance wires 11a are mounted on the upper end surface of the optional grating blade 11 along the second direction Z, first ends of the two resistance wires 11a extend to the side end surface 13c of the penumbra reduction portion 13 and are electrically connected, and second ends of the two resistance wires 11a extend to the edge of the main body portion 13 and are disconnected; the multileaf grating further comprises: the position detection mechanism 2 is arranged corresponding to the blade group 1, the position detection mechanism 2 comprises a circuit board 21 and M detection units 22 positioned on the circuit board 21, the circuit board 21 penetrates through two resistance wires 11a of any one grating blade 11 in the blade group 1, the M detection units 22 and the M grating blades 11 are respectively arranged correspondingly, and the detection units 22 are used for detecting electric signals of the two resistance wires 11a contacted with the detection units to determine the position of the corresponding grating blade 11.
As described above, the two resistance wires 11a mounted on the upper end surface of the grating blade 11 include two in number, one end of the two resistance wires 11a being electrically connected and the other end being electrically disconnected, wherein the two resistance wires 11a are electrically connected at the side end surface 13c of the penumbra-reducing section 13. The position detection mechanism 2 comprises a circuit board 21, and after assembly, the circuit board 21 passes through the space between the upper and lower resistance wires 11a of each grating blade 11 in the blade group 1. The detection units 22 on the circuit board 21 are arranged in one-to-one correspondence with the grating blades 11, and after assembly, the detection units 22 are in close contact with the upper and lower resistance wires 11a of one corresponding grating blade 11 to keep electrical connection. When the position of the grating blade 11 changes, the detecting unit 22 electrically contacting the resistance wire 11a of the grating blade 11 can detect the resistance change of the resistance wire 11a, and the resistance change of the resistance wire 11a corresponds to the position change of the grating blade 11. The circuit board 21 has a position detection-related detection circuit that acquires an electric signal detected by the detection unit 22, and determines position information of the grating blade 11 corresponding to the detection unit 22 based on the electric signal.
The optional detection unit 22 includes a first brush 22a on the upper surface of the circuit board 21 and a second brush 22b on the lower surface of the circuit board 21, the first brush 22a being in electrical contact with a resistance wire 11a located thereon, and the second brush 22b being in electrical contact with a resistance wire 11a located therebelow. One detecting unit 22 includes two brushes on the upper and lower surfaces of the circuit board 21, which are in contact with the upper and lower resistance wires 11a corresponding thereto, respectively. After assembly, the upper and lower surface brushes can be in close contact with the corresponding upper and lower resistance wires 11a to keep electrical connection. The circuit board 21 is electrically connected to the brushes, and can detect a change in resistance of the resistance wire 11a corresponding to a change in position of the grating blade 11.
The selectable-position detecting mechanism 2 further includes: the blade track frame 23 is arranged corresponding to the blade group 1, and the main body part of the grating blade 11 in the blade group 1 penetrates through the corresponding blade track frame 23; the upper surface adjacent with the up end of blade track frame 23 has opening 23a, and opening 23a is used for holding circuit board 21, and the upper surface of blade track frame 23 is seted up and is run through opening 23a and follow M through-hole group of first direction Y, and a through-hole group includes 2 through-holes 23b of arranging along second direction Z, and 2 through-holes 23b of a through-hole group correspond the setting with two resistance wire 11a of a grating blade 11, and resistance wire 11a passes corresponding through-hole 23 b.
In this embodiment, the blade rail frame 23 is a column-type hollow frame, the column-type frame is square, and the main body of each grating blade 11 in the blade group 1 can pass through the hollow interior of the blade rail frame 23. The upper end surface referred to herein is an upper end surface of the grating blade 11 along the second direction Z, the upper end surface is provided with an upper resistance wire 11a and a lower resistance wire 11a, the opening 23a of the blade rail frame 23 is an opening 23a which is provided on one side frame body of the blade rail frame 23 and vertically penetrates through the frame body, and the circuit board 21 is accommodated in the opening 23 a. The extending direction of the through hole 23b on the frame body of the blade rail frame 23 is parallel to the extending direction of the resistance wire 11a, and the resistance wire 11a of the grating blade 11 passes through the frame body of the blade rail frame 23 and the opening 23a through the through hole 23b on the frame body of the blade rail frame 23. Therefore, the blade track frame 23 and the through holes 23b thereon can limit the displacement of the main body part of the grating blade 11 in the blade track frame 23, and the circuit board 21 accommodated in the opening 23a after the displacement can detect the position information of each grating blade 11.
The optional resistance wire 11a is a nichrome wire. The resistance wire 11a is a metal wire with high resistivity, and should have certain strength and wear resistance, so a nichrome wire is preferred.
The optional multi-leaf grating further comprises: a blade driving motor 3 provided corresponding to the blade group 1; the blade driving mechanism 3 includes M driving motors 31, the M driving motors 31 and M grating blades 11 are respectively disposed correspondingly, and the driving motors 31 are used for driving the main body of the corresponding grating blade 11 to move in the blade track frame 23. In this embodiment, one driving motor 31 is disposed corresponding to one grating blade 11, and the driving motor 31 drives the corresponding grating blade 11 to displace in the first direction Y. The optional blade driving motor 3 further comprises a shielding plate 32, and the shielding plate 32 can shield the coupling influence of the driving motor 31 on the grating blade 11.
In the embodiment of the invention, under the condition of equal field penumbra, the height of the main body part is reduced, the cost of the grating blade can be saved, and the whole volume of the multi-leaf grating can be reduced; under the condition of the same overall volume of the multi-leaf grating, the increased height of the front side of the grating blade does not additionally occupy the overall space of the multi-leaf grating, and meanwhile, the increased height of the front side of the grating blade can also reduce the field penumbra and improve the treatment accuracy of the multi-leaf grating.
Based on the same inventive concept, the embodiment of the invention also provides a method for manufacturing the grating blade of the multi-blade grating, the multi-blade grating can be selected from the multi-blade grating described in any embodiment, and the multi-blade grating can be applied to the medical field, in particular to a linear accelerator treatment head.
As shown in fig. 11, a method for manufacturing a grating blade of a multi-leaf grating according to an embodiment of the present invention includes:
and S1, calculating the number of half-layer values required by the selected blade material according to the required specification parameters of the ray leakage rate of the grating blade, and determining the height of the main body part along the second direction.
In this embodiment, the design of the main body portion of the grating blade is related to the required specification of the leakage rate of the radiation of the grating blade, wherein the number of half-layers required for the selected grating blade material is calculated according to the required specification of the leakage rate of the radiation of the multi-leaf grating. The leakage rate of the radiation refers to the ratio of the residual radiation dose to the total incident dose after the radiation intensity is attenuated after a specific radiation passes through a shielding material (namely a grating blade). The half-thickness value is the thickness of the shielding material (i.e., the height along the second direction Z) required for a particular radiation to pass through the shielding material with half the attenuation of the radiation intensity. In practice, the ray leakage rate requirement specification parameters are required parameters set by a worker according to treatment needs; when the material of the grating blade is determined, the half-layer value of the grating blade is determined, and the half-layer values of different materials may be different.
For example, the radiation leakage rate of the grating blade requires a specification parameter of 1%, that is, after a specific radiation passes through the grating blade, the radiation intensity is attenuated to 1% of the original radiation intensity, and the number of half-layer values is n.
Then, n is log (0.01)/log (0.5),
the calculation shows that n is 6.64,
rounding to yield n ═ 7.
Therefore, according to the half-layer value number n and the half-layer value of the shielding material, the height of the theme part of the grating blade along the second direction Z can be calculated. For example, if the material of the grating blade is tungsten alloy, the half-value of the tungsten alloy is 10mm, and the number of half-values is 7, the height H2 of the main body portion of the grating blade is 10 × 7 — 70 mm.
S2, calculating the coordinate value, height and arc of the arc-shaped part of the rectangular part in the penumbra reduction part. The height of the rectangular section is greater than the height of the main body portion.
Alternative H1 ═ H2+ w1+ w 2; h1 is the height of the rectangular subsection, H2 is the height of the main body section, w1 is the blade upper layer ramp thickness, and w2 is the blade lower layer ramp thickness. The thickness of the blade upper layer slide way is the vertical distance between the upper end face of the rectangular subsection in the penumbra reduction part and the upper end face of the main body part. The thickness of the lower blade layer slide way is the vertical distance between the lower end face of the rectangular subsection in the penumbra reduction part and the lower end face of the main body part. The height H1 of the penumbra-reducing section is equal to the height H2 of the body section plus the upper ramp thickness w1 and the lower ramp thickness w2 of the grating blade. For example: the thickness of the upper layer slide way and the lower layer slide way is 10mm, and H1 is 70+10 × 2 is 90 mm.
The arc parameters of the arc-shaped parts of the grating blades are geometric parameters designed and optimized according to a multi-blade grating end face shape design method, wherein the end face shape design method comprises a cutting line analysis method, a Monte Carlo simulation method and the like, and the geometric parameters of the arc comprise the circle center position, the radius size and the like.
The optional multileaf grating comprises a light source; as shown in fig. 12, calculating the coordinate values of the rectangular sections in the penumbra-subtracted section includes:
s21, establishing a plane rectangular coordinate system, wherein the origin of coordinates of the plane rectangular coordinate system is a light source, and the horizontal axis of the plane rectangular coordinate system is parallel to the first direction and the longitudinal axis of the plane rectangular coordinate system is parallel to the second direction;
s22, forming a first straight line passing through the origin of coordinates, wherein the included angle between the first straight line and the longitudinal axis is the maximum opening angle of the first side beam and is tangent to the arc of the arc subsection of the grating blade;
s23, forming a second straight line passing through the origin of coordinates, wherein the first end point of the second straight line is positioned on the first side of the main body part in the grating blade, the second end point is positioned on the arc of the arc-shaped subsection of the grating blade, and the distance between the first end point and the second end point is equal to the height of the main body part;
s24, defining an intersection of a third line passing through the first end point and a fourth line passing through the first start of the arcuate segment arc as a vertex of the rectangular segment, the third line being parallel to the longitudinal axis and the fourth line being parallel to the transverse axis, the first start of the arcuate segment arc being immediately adjacent to the second end point.
The whole selectable grating blade is positioned on the left side of the longitudinal axis, and the first edge of the main body part is the lower edge of the main body part; alternatively, the grating blade intersects the longitudinal axis and the first edge of the body portion is an upper edge thereof.
The horizontal axis of the rectangular plane coordinate system is a first direction Y and the vertical axis of the rectangular plane coordinate system is a second direction Z.
Calculating the upper left coordinate value as shown in figure 13, where the grating blade 11 is located entirely to the left of the longitudinal axis Z and the first edge of the body portion is the lower edge thereof, the height H2 of the body portion and the arc parameters of the arcuate section can be determined from the above steps. The calculation process is as follows:
1) the light source passing point, i.e. the coordinate origin O, is taken as a first straight line 41, an included angle θ 1 between the first straight line 41 and the longitudinal axis Z is a first side beam maximum opening angle, so that the circular arc of the arcuate section 13a of the grating blade 11 is tangent to the first straight line 41, wherein the first side beam maximum opening angle is a known parameter or a preset parameter.
2) The light source passing point O is made into a second straight line 42, such that a first end point a of the second straight line 42 is located at the lower side of the main body portion of the grating blade 11 and a second end point B is located on the arc of the arcuate branch portion 13a thereof, and the distance between the connecting lines of the first end point a and the second end point B is equal to the height H2 of the main body portion.
3) The first end point a is formed as a third straight line 43 parallel to the longitudinal axis Z, the first starting point C of the arc of the arcuate segment 13a is formed as a fourth straight line 44 parallel to the transverse axis Y, and the intersection D of the third straight line 43 and the fourth straight line 44 is defined as a vertex of the rectangular segment, wherein the first starting point C of the arc of the arcuate segment 13a is immediately adjacent to the second end point B. The coordinates of A, B, C and D point can be calculated by mathematical analysis.
Calculating the lower right angle coordinate as shown in figure 14, where the grating blade 11 intersects the longitudinal axis Z and the first edge of the body portion is its upper edge, the height H2 of the body portion and the arc parameters of the arcuate section can be determined from the above steps. The calculation process is as follows:
1) the light source passing point, i.e. the origin of coordinates O, is taken as a first straight line 51, an included angle θ 2 between the first straight line 51 and the longitudinal axis Z is a second side beam maximum opening angle, so that the circular arc of the arcuate section 13a of the grating blade 11 is tangent to the first straight line 51, wherein the second side beam maximum opening angle is a known parameter or a preset parameter.
2) The light source passing point O is made into a second straight line 52, such that a first end point a of the second straight line 52 is located at the upper side of the main body portion of the grating blade 11 and a second end point B is located on the arc of the arcuate branch portion 13a thereof, and the distance between the connecting lines of the first end point a and the second end point B is equal to the height H2 of the main body portion.
3) The first end point a defines a third line 53 parallel to the longitudinal axis Z, the first origin C of the arc of the arcuate segment 13a defines a fourth line 54 parallel to the transverse axis Y, and the intersection D of the third line 53 and the fourth line 44 defines a vertex of the rectangular segment, with the first origin C of the arc of the arcuate segment 13a being immediately adjacent the second end point B. The coordinates of A, B, C and D point can be calculated by mathematical analysis.
The calculated spacing of C and D from the structure shown in fig. 13 is CD1 and the calculated spacing of C and D from the structure shown in fig. 14 is CD2, the CD maximum is taken as the width of the rectangular subsection in the first direction Y. If CD1 is smaller than CD2, the value of CD2 is taken as the width of the rectangular subsection in the first direction Y. The arc shape of the arcuate branch 13a is known, the height H1 of the arcuate branch 13a and thus the width of the rectangular branch in the second direction Z is equal to H1.
The combination of the arc-shaped part and the rectangular part is the shape of the penumbra eliminating part, and the combination of the shape and the main body part is the shape of the grating blade.
In the embodiment of the invention, under the condition of equal field penumbra, the height of the main body part is reduced, the cost of the grating blade can be saved, and the whole volume of the multi-leaf grating can be reduced; under the condition of the same complete machine volume of the multi-leaf grating, the height of the front side of the grating blade is increased, the complete machine space of the multi-leaf grating is not additionally occupied, meanwhile, the increased height of the part can also reduce the field penumbra, and the treatment accuracy of the multi-leaf grating is improved.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in some detail by the above embodiments, the invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the invention, and the scope of the invention is determined by the scope of the appended claims.
Claims (8)
1. A multileaf grating, comprising: the grating blade comprises a main body part and a penumbra reduction part which are connected along the first direction;
the penumbra-reducing section comprises an arcuate section and a rectangular section connecting the arcuate section and the body section, the maximum dimension of the arcuate section is equal to the dimension of the rectangular section in a second direction perpendicular to the first direction, the dimension of the rectangular section is greater than the dimension of the body section, the first direction and the second direction are both parallel to the surface of the grating blade, and the arcuate sections of two grating blades in different blade groups are oppositely arranged;
the grating blade manufacturing method comprises the following steps:
calculating the number of half-layer values required by the selected blade material according to the required specification parameters of the ray leakage rate of the grating blade, and determining the height of the main body part along the second direction;
calculating the coordinate value and the height of a rectangular subsection in the penumbra reduction part and the circular arc of an arched subsection;
the multileaf grating further comprises a light source;
wherein calculating the coordinate values of the rectangular sections in the penumbra-subtracted section comprises:
establishing a plane rectangular coordinate system, wherein the origin of coordinates of the plane rectangular coordinate system is the light source, and the transverse axis of the plane rectangular coordinate system is parallel to the first direction and the longitudinal axis of the plane rectangular coordinate system is parallel to the second direction;
forming a first straight line passing through the origin of coordinates, wherein an included angle between the first straight line and the longitudinal axis is a first side beam maximum opening angle and is tangent to the arc of the arched subsection of the grating blade;
forming a second line through the origin of coordinates, the first end of the second line being located on a first side of the body portion of the grating blade and the second end being located on the arc of its arcuate subsection, the first end and the second end being spaced apart by a distance equal to the height of the body portion;
determining as a vertex of the rectangular segment an intersection of a third line passing through the first end point and a fourth line passing through the first start of the arcuate segment arc, the third line being parallel to the longitudinal axis and the fourth line being parallel to the transverse axis, the first start of the arcuate segment arc being immediately adjacent to the second end point.
2. The multileaf grating according to claim 1, wherein two resistance wires are mounted on the upper end surface of the grating blade in the second direction, first ends of the two resistance wires extend to the side end surface of the penumbra reduction part and are electrically connected, and second ends of the two resistance wires extend to the edge of the main body part and are disconnected;
the multileaf grating further comprises: the position detection mechanism is arranged corresponding to the blade group and comprises a circuit board and M detection units positioned on the circuit board, the circuit board penetrates through the space between two resistance wires of any one grating blade in the blade group, the M detection units and the M grating blades are respectively arranged corresponding to each other, and the detection units are used for detecting electric signals of the two resistance wires contacting with the detection units so as to determine the positions of the corresponding grating blades.
3. The electrical multi-leaf collimator as claimed in claim 2, wherein the detecting unit comprises a first brush located on the upper surface of the circuit board and a second brush located on the lower surface of the circuit board, the first brush being in electrical contact with a resistance wire located thereon, and the second brush being in electrical contact with a resistance wire located therebelow.
4. The multileaf grating of claim 3, wherein the position detection mechanism further comprises: the blade track frame is arranged corresponding to the blade group, and the main body part of the grating blade in the blade group penetrates through the corresponding blade track frame;
the upper surface of blade track frame with the up end is adjacent has the opening, the opening is used for holding the circuit board, the upper surface of blade track frame has been seted up and has been run through the opening just follows a M through-hole group of first direction, one the through-hole group includes the edge 2 through-holes that the second direction was arranged, one 2 through-holes and one of through-hole group two resistance wires of grating blade correspond the setting, just the resistance wire passes correspondingly the through-hole.
5. The multileaf grating of claim 4, wherein the resistive wire is a nichrome wire.
6. The multileaf grating of claim 4, further comprising: a blade driving motor provided corresponding to the blade group; the blade driving motors comprise M driving motors, the M driving motors and the M grating blades are respectively and correspondingly arranged, and the driving motors are used for driving the main body parts of the corresponding grating blades to move in the blade track frame.
7. The multileaf grating of claim 1,
h2＝h1+w1+w2；
h2 is the height of the rectangular section, h1 is the height of the body section, w1 is the blade upper ramp thickness, and w2 is the blade lower ramp thickness.
8. The multileaf grating of claim 1 wherein the grating leaf is generally located to the left of the longitudinal axis, the first edge of the body portion being a lower edge thereof; alternatively, the first and second electrodes may be,
the grating blade intersects the longitudinal axis, and the first edge of the body portion is an upper edge thereof.
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