CN107362463B

CN107362463B - Collimator, radiation system and selection method of collimator blades

Info

Publication number: CN107362463B
Application number: CN201710671277.0A
Authority: CN
Inventors: 李贵; 刘娟; 刘艳芳
Original assignee: Shanghai United Imaging Healthcare Co Ltd
Current assignee: Shanghai United Imaging Healthcare Co Ltd
Priority date: 2014-05-28
Filing date: 2014-05-28
Publication date: 2020-03-31
Anticipated expiration: 2034-05-28
Also published as: CN104795122B; CN107362463A; CN104795122A

Abstract

A collimator, a radiation system and a selection method of collimator blades are provided. The collimator comprises more than two blades which are oppositely arranged in two arrays, and each array comprises more than one blade; the blade comprises an extension structure body, wherein the extension structure body comprises a first end and a second end which are oppositely arranged along an extension direction, and the end surface shape of the first end is a first curve shape. By setting the shape of the end surface of the first end of the collimator blade into the first curve shape, the change of the generated penumbra can be more uniform, and the first curve-shaped collimator can be more beneficial to radiotherapy.

Description

Collimator, radiation system and selection method of collimator blades

The application is a divisional application of Chinese patent application with application number 201410231053.4, entitled selection method of collimator, radiation system and collimator blade, which is filed in the Chinese patent office on 28 th 05 month in 2014.

Technical Field

The invention relates to the technical field of medical equipment, in particular to a collimator, a radiation system and a selection method of collimator blades.

Background

Collimators are medical devices used to create a conformal radiation field, i.e., to limit the extent to which therapeutic radiation from a radiation source impinges on the surface of a patient's body, thereby protecting the patient's normal organs or tissues from radiation. Collimators have a wide range of applications in the field of radiotherapy.

Collimators typically comprise a plurality of leaves arranged in two arrays, forming pairs of opposed leaves. Each vane of a pair of vanes is movable away from or towards the other vane of the pair, and adjacent vanes of both arrays may define one or more voids after being positioned. The vanes can block part of rays of the radioactive source, and rays which are not blocked pass through the gaps defined by the vanes to irradiate the body surface of the patient. Through the movement of the blades, a radiation field meeting the requirements can be generated.

When rays which are not blocked by the blades irradiate the body surface of the patient, a penumbra is generated. The larger the penumbra, the greater the radiation to which the normal organ or tissue of the patient is exposed. The uneven change of the penumbra is not favorable for correcting the radiation field. However, the conventional collimator has a problem that the penumbra is large and the variation of the penumbra is not uniform.

Disclosure of Invention

The embodiment of the invention solves the problems that the existing collimator generates a larger penumbra and the penumbra changes unevenly.

In order to solve the above problems, an embodiment of the present invention provides a collimator, including two or more blades, where the blades are oppositely disposed in two arrays, and each array includes one or more blades; the blade includes an extension structure, the extension structure includes along relative first end and the second end that sets up of extending direction, first end shape is first curve, first curve is the smooth curve of curvature radius from the summit along extending direction grow gradually, the shape of first curve with the position at summit is confirmed by the penumbra length that has different summits or the corresponding of the blade of the end shape of different curvature radius.

Optionally, the first curve comprises: the curve used for representing the even function and the curve after the curve used for representing the even function is translated or rotated.

Optionally, the first curve is a parabola, a hyperbolic cosine curve, or an arc on an ellipse connecting two endpoints of the short axis.

Optionally, the first curve is a curve representing a linear combination of a plurality of even functions.

Optionally, the extension structure is a planar extension sheet.

Optionally, each said array comprises two or more blades.

Optionally, the extending structure body is provided with a concave-convex structure, and the concave-convex structures of two adjacent blades are mutually inserted. Optionally, each said array comprises a vane.

Optionally, the determining of the shape of the first curve and the position of the vertex by the penumbra lengths corresponding to end-face-shaped blades having different vertices or different radii of curvature comprises:

determining a first bending degree according to the penumbra length corresponding to the first end surface with the shape of the curve with different curvature radiuses,

and determining the first curve according to the corresponding penumbra length when the shape of the first end surface is a curve with a first bending degree and the vertex of the curve is positioned at different positions in the direction vertical to the symmetry axis of the curve.

determining a first curvature radius according to the corresponding penumbra length when the shape of the first end surface is the circular arc with different curvature radii,

determining a first bending degree according to a penumbra length corresponding to a curve with a first curvature radius at a vertex and different bending degrees when the first end surface is in a shape,

determining the first vertex according to the corresponding penumbra length when the first end surface is shaped into a curve with a first curvature radius and a first bending degree and the vertex of the curve is positioned at different positions vertical to the symmetry axis direction of the curve,

the first curve is a curve having a first vertex and a first degree of curvature, and the radius of curvature at the first vertex is the first radius of curvature.

An embodiment of the present invention further provides a radiation system, including: a radiation source for generating radiation, and a collimator as described above, the first ends of the leaves of the collimator being adjacent the end of the other array opposite the array in which the leaves are located, the leaves, when positioned, defining a gap through which radiation generated by the radiation source passes to impinge on the target area.

The embodiment of the invention also provides a method for selecting the blades of the multi-blade collimator, which comprises the following steps:

a. determining a first radius of curvature:

under the condition of the same radioactive source, obtaining a first penumbra curve corresponding to blades with arc-shaped end surfaces with different curvature radiuses when the blades move, wherein the intersection point of a symmetry axis of the arc and the arc is an origin point;

selecting a first penumbra curve with a smaller numerical value and more gradual change in the first penumbra curve, wherein the curvature radius of the selected first penumbra curve is a first curvature radius;

b. determining a first degree of bending:

under the condition of the same radioactive source, obtaining a second penumbra curve which corresponds to the blades of a second curve end face with different bending degrees and an original point as a vertex when the blades move, wherein the second curve is a smooth curve with the curvature radius gradually increasing from the vertex along the extending direction, the curvature radius at the vertex is a first curvature radius, and the difference value of the curvature radius of two adjacent sampling points on the second curve is the same;

selecting a second penumbra curve with a smaller numerical value and more gradual change in the second penumbra curve, wherein the bending degree of the second curve corresponding to the selected second penumbra curve is the first bending degree;

c. determining a first vertex:

under the condition of the same radioactive source, obtaining a third penumbra curve which corresponds to the movement of a blade of a third curve end face with the first curvature radius as the curvature radius of the vertex and different vertexes, wherein the vertex of the third curve is arranged on a coordinate axis which passes through the origin and is vertical to a symmetrical axis of the third curve, the third curve is a smooth curve with the curvature radius gradually increasing from the vertex along the extending direction, and the bending degree of the third curve is the same as the first bending degree;

selecting a third penumbra curve with smaller numerical value and more gradual change in the third penumbra curve, wherein the vertex corresponding to the selected third penumbra curve is a first vertex;

d: determining a first curve:

the method comprises the step of taking a blade of a first curve end face which is provided with the first vertex and the curvature radius of the first vertex is a first curvature radius as a blade of the collimator, wherein the first curve is a smooth curve with the curvature radius gradually increasing from the vertex along the extending direction, and the bending degree of the first curve is the same as the first bending degree.

Optionally, the first curve, the second curve, and the third curve are all curves for representing even functions or curves obtained by translating or rotating the curves for representing even functions.

Optionally, the first curve, the second curve, and the third curve are all parabolas, hyperbolic cosine curves, or arcs connecting two endpoints of the short axis on an ellipse.

The embodiment of the invention also provides a collimator blade selection method, which comprises the following steps:

a. determining a first radius of curvature:

determining a first curvature radius according to the corresponding penumbra length when the shape of the first end face of the blade is circular arcs with different curvature radii;

b. determining a first degree of bending:

determining a first bending degree according to a penumbra length corresponding to a curve with a first curvature radius at a vertex and different bending degrees when the shape of the first end face of the blade is the vertex;

c. determining a first vertex:

determining a first vertex according to the corresponding penumbra length when the shape of the first end surface of the blade is a curve with a first curvature radius and a first bending degree, and the vertex of the curve is positioned at different positions in the direction vertical to the symmetry axis of the curve;

d: determining a first curve:

the method comprises the step of taking a blade of a first curve end face which is provided with a first vertex and the curvature radius of the first vertex is the first curvature radius as a blade of the collimator, wherein the first curve is a smooth curve with the curvature radius gradually increasing from the vertex along the extending direction, and the bending degree of the first curve is the same as the first bending degree.

Compared with the prior art, the technical scheme of the embodiment of the invention has the following advantages:

through setting up the terminal surface shape of the first end of blade into first curvilinear figure, can make the blade when blocking the ray irradiation at patient's body surface, for the blade of present straight line shape terminal surface shape, the length of shining produced penumbra reduces, and for the blade of present circular arc plus tangent line shape terminal surface shape, produced penumbra changes more evenly. Therefore, the multi-leaf collimator in the embodiment of the invention is more beneficial to radiotherapy.

Drawings

FIG. 1 is a schematic view of a radiation system in an embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of a collimator leaf in an embodiment of the invention;

FIG. 3 is a flow chart of a method for selecting collimator leaves in an embodiment of the invention;

FIG. 4 is a graph of penumbra data obtained according to the method of FIG. 3.

Detailed Description

In practical application, the size of the penumbra generated during irradiation has a certain relationship with the shape of the end surface of the collimator blade near one end of the other array opposite to the array where the blade is located, and one end of the blade near the other array opposite to the array where the blade is located is taken as the first end of the blade.

At present, the end surface shape of the first end of the blade is generally set to the following two types:

first, referring to chinese patent application No. 201220426615.7, the end shape of the first end of the blade is configured as a straight end. Because the curvature of the linear end face is 0, and the curvatures of the two ends of the blade, which are in contact with the linear end face, are larger, along with the linear motion of the blade, when the radiation generated by the radiation source is irradiated to the two ends of the blade, which are in contact with the linear end face, from the linear end face of the blade, the curvature of the position where the radiation is irradiated on the blade is suddenly changed to be larger at the position where the radiation is in contact with the linear end face, so that the change of the generated penumbra is not uniform, and the radiation treatment is not facilitated. Moreover, the average length of the penumbra produced by the blades with the shape of a straight end face is also larger, thereby causing the normal organs or tissues of the patient to be subjected to larger radiation;

second, referring to U.S. patent publication No. 5166531, the end surface of the first end of the blade is formed to be arranged in a circular-arc plus-tangential line shape. Because the camber of circular arc terminal surface department is unchangeable, and the camber of tangent line terminal surface department reduces earlier afterwards to the one end of keeping away from the circular arc from the one end with the circular arc contact, consequently, along with the rectilinear motion of blade, when the produced ray of radiation source shines tangent line terminal surface department by circular arc terminal surface department, produced penumbra increases earlier, reduces again, and the later increases again, and the camber change of circular arc plus tangent line shape terminal surface is discontinuous promptly, leads to produced penumbra to change inhomogeneous, is unfavorable for proofreaying and correct the radiation field.

In view of the above problems, embodiments of the present invention provide a collimator in which an end surface of a first end of a leaf of the collimator has a first curved shape. Thus, in a specific application, the collimator of the embodiment of the invention has the blades with smaller and more uniform penumbra length compared with the blades with the linear end surface shape. Moreover, compared with the blades with the shape of the arc plus tangent line end surface, the blades of the collimator in the embodiment of the invention have more uniform change of the generated penumbra. Therefore, the collimator in the embodiment of the invention is more beneficial to the radiation treatment.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

As shown in fig. 1, an embodiment of the present invention provides a radiation system. The radiation system comprises a gantry 10. A radiation source 120 and a collimator system 130 are disposed on the head 110 of the gantry 10. Wherein the collimator is arranged inside said collimator system 130. Radiation source 120 may generate radiation 140 for radiation treatment of a patient.

In a specific implementation, the patient is placed on an examination couch 150. As the couch 150 moves, the radiation 140 passes through the conformal radiation field formed by the collimator and impinges on the target region, thereby enabling radiation treatment of the focal site in the patient.

As shown in fig. 2, in the embodiment of the present invention, the collimator includes more than two blades 20. The blade 20 includes an extension structure 210. The extension structure 210 includes a first end 220 and a second end 230 oppositely disposed in an extension direction. The end surface of the first end 220 is shaped like a first curve, and the first curve is a smooth curve with a curvature radius gradually increasing from a vertex along an extending direction.

The end face shape of the first end 220 is set to be a first curve shape, and compared with the existing end face shape of the first end 220 which is set to be a straight line shape, because the curvature radius of the end face of the first curve shape is larger than 0, when rays generated by a radioactive source are irradiated onto two ends of the blade, which are contacted with the first end, from the end face of the first end in the linear motion of the blade, the change of the curvature radius is relatively small, so that the change of the generated penumbra is relatively small, namely the change of the penumbra is more uniform. Moreover, since the curvature radius of the first curve gradually increases from the vertex in the extending direction, the average length of the generated penumbra can be made smaller in the linear motion of the blade having the first curved end face than that of the blade having the linear end face.

Compared with the prior art that the end surface shape of the first end 220 is a circular arc plus tangent line shape, the end surface shape of the first end 220 is set to be a first curve shape, and the curvature radius of the end surface of the first curve shape is continuously changed, so that the change of the generated penumbra is more uniform.

In a specific implementation, the blades 20 are arranged in two arrays, forming pairs of opposing blades 20. The first end 220 of each blade 20 is disposed proximate to an end of the other array opposite the array in which the blade 20 is disposed. Each pair of opposing blades 20 moves in a direction perpendicular to the centerline 1402 (see fig. 1). The gaps defined by the leaves 20 when positioned can form a conformal radiation field, which can enable the radiation 140 (see fig. 1) generated by the radiation source to irradiate the target area more accurately.

In a particular implementation, the first curve may include a curve representing an even function. For example, the first curve may be a parabola, a hyperbolic cosine curve, or an arc on an ellipse connecting two end points of the short axis. The first curve may further include a curve in which the curve representing the even function is transformed by translation or rotation. For example, the first curve may be a curve obtained by translating or rotating a parabola, a curve obtained by translating or rotating a hyperbolic cosine curve, or a curve obtained by translating or rotating an arc connecting two end points of a short axis on an ellipse.

The curve representing the even function may be a curve representing one even function, or may be a curve representing a linear combination of a plurality of even functions. The curve for representing the even function after the translation or rotation transformation may be a curve for representing the even function after the translation or rotation transformation, or a plurality of curves for representing the even function after the translation or rotation transformation are linearly combined.

The shape of the end surface of the second end 230 may be any shape, and is not limited herein. For example, the end surface shape of the second end 230 may be set to the same shape as the end surface shape of the first end 220.

The shape of the extension structure 210 may be any shape, and is not limited here. For example, the extension structures 210 are planar extension pieces. Wherein the planar extension may be rectangular.

In a specific implementation, in the two arrays where the blades are located, each array may have only one blade, or may have two or more blades. When each array has two or more blades, the extension structure 210 may be provided with a concave-convex structure, so that the concave-convex structures between two adjacent blades of the same array are inserted into each other to better meet the requirements of treatment.

As shown in fig. 3, the embodiment of the present invention further provides a collimator blade selecting method, in which, in the case of setting the shape of the first end surface of the collimator blade to be in the first curve shape, from the blades of the first curve end surface having different vertexes or curvature radii, the blades with relatively small penumbra lengths and relatively uniform changes are selected to better meet the requirements of treatment. The method may include: a step a; determining a first radius of curvature; step b: determining a first degree of bending; step c: determining a first vertex; and step d: a first curve is determined.

In a specific implementation, the step a may include

steps

310 and 320, where:

step 310: under the condition of the same radioactive source, obtaining a first penumbra curve corresponding to the moving blade with a circular arc end surface without curvature radius, wherein the intersection point of the symmetrical axis of the circular arc and the circular arc is an origin.

As the curvature radius of any point on the circular arc is the same, the intersection point of the symmetry axis of the circular arc and the circular arc is set as the origin, and different circular arcs can be obtained by selecting different curvature radii. The blades with different circular arc end surfaces can generate penumbra in the moving process. And measuring penumbra values generated at different positions of the blade to obtain a plurality of first penumbra curves.

It should be noted that, in a commonly used two-dimensional (or three-dimensional) rectangular coordinate system, there are two (or three) coordinate axes perpendicular to each other. The origin is an intersection of coordinate axes, the coordinate is (0, 0) (or (0, 0, 0)), and the origin divides the coordinate axes into two segments, with the coordinate on one side of the origin being a positive value and the coordinate on the other side being a negative value.

Fig. 4 is a penumbra curve corresponding to different positions of the collimator blade, wherein the abscissa in fig. 4 represents the distance from the blade to the center line of the radiation source, and the ordinate represents the penumbra value corresponding to the blade moving to different positions. As shown in fig. 4, when the radius of curvature is equal to 5.5cm, the first penumbra curve obtained is data line 1. When the radius of curvature is equal to 6cm, the first penumbra curve obtained is data line 2. When the radius of curvature is equal to 6.25cm, the first penumbra curve obtained is data line 3.

Step 320: and selecting a first penumbra curve with smaller numerical value and more gradual change in the first penumbra curve, wherein the curvature radius of the selected first penumbra curve is a first curvature radius.

From the plurality of first penumbra curves obtained in step 310, a first penumbra curve with a smaller penumbra value and a more gradual change is selected.

As shown in fig. 4, the data line 1, the data line 2, and the data line 3 have a first semi-curved line with a small numerical value and a gentle change as the data line 2, and the curvature radius corresponding to the vertex of the first semi-curved line is 6cm, that is, the first curvature radius is 6 cm.

The step b may include

steps

330 and 340, wherein:

step 330: under the condition of the same radioactive source, a second penumbra curve which corresponds to the blades of a second curve end face with different bending degrees and an original point as a vertex is obtained when the blades move, the second curve is a smooth curve with the curvature radius gradually increased from the vertex along the extending direction, the curvature radius at the vertex is a first curvature radius, and the difference value of the curvature radius between two adjacent sampling points on the second curve is the same.

In an embodiment of the invention, the vertex is the point on the curve with the smallest radius of curvature. When the curve is a curve representing an even function or a curve obtained by transforming the curve representing the even function by translation or rotation, the vertex is a point on the second curve, which is intersected with the symmetry axis of the second curve. The interval of the radii of curvature at the vertices is not limited and can be selected by one skilled in the art as desired.

The degree of curvature is different, i.e. the radius of curvature of each curve varies differently. And sampling the second curve at equal intervals, and setting the second curves with different bending degrees by taking the original point as the vertex and enabling the curvature radius at the vertex to be the first curvature radius when the difference value of the curvature radii of two adjacent sampling points is the same. And measuring the penumbra value generated by the blade with the second curve-shaped end surface when the blade moves, and connecting the penumbra values of the blade at different positions to obtain a corresponding second penumbra curve.

Step 340: and selecting a second penumbra curve with smaller numerical value and more gradual change in the second penumbra curve, wherein the bending degree of the second curve corresponding to the selected second penumbra curve is the first bending degree.

Selecting a second penumbra curve with a smaller penumbra value and a smoother change from the plurality of second penumbra curves obtained in step 330. And taking the bending degree of the second curve corresponding to the selected second penumbra curve as the first bending degree.

Step c may include

steps

350 and 360, wherein:

step 350: under the condition of the same radioactive source, obtaining a third penumbra curve which corresponds to the blades of a third curve end face with the first curvature radius as the curvature radius of the vertex and different vertexes when the blades move, wherein the vertexes of the third curve are arranged on a coordinate axis which passes through the origin and is perpendicular to a symmetry axis of the third curve, the third curve is a smooth curve with the curvature radius gradually increasing from the vertexes along the extending direction, and the bending degree of the third curve is the same as the first bending degree.

In step 330, a second penumbra curve with a smaller penumbra value and a more gradual change is selected from the second penumbra curves obtained in step 320, and the third curve is set according to the degree of curvature of the second curve corresponding to the obtained second penumbra curve. And selecting different vertex positions by taking the first curvature radius as the curvature radius of the vertex of the third curve, so that a plurality of third curves with the same bending degree but different vertex positions can be obtained.

In a specific implementation, the vertex of the third curve is set on a coordinate axis passing through the origin and perpendicular to the symmetry axis of the third curve, that is, the abscissa or the ordinate of the vertex of the third curve is set to 0. And if the coordinate axis which passes through the origin and is perpendicular to the symmetry axis of the third curve is an X axis, the vertical coordinate of the vertex of the third curve is 0. And if the coordinate axis which passes through the origin and is perpendicular to the symmetry axis of the third curve is the Y axis, the abscissa of the vertex of the third curve is 0.

Taking a coordinate axis passing through the origin and perpendicular to the symmetry axis of the third curve as an Y axis as an example, a coordinate axis passing through the origin and parallel to the symmetry axis of the third curve at this time is an X axis, and the third curve can be determined according to the obtained first curvature radius and the selected vertex position. And measuring the penumbra value generated by the blade with the third curve-shaped end surface when the blade moves, and connecting the penumbra values of the blade at different positions to obtain a corresponding second penumbra curve.

As shown in fig. 4, when the first curvature radius is 6cm, the abscissa of the vertex is 0, and the ordinate is 0.10cm, the corresponding second penumbra curve is the data line 4. When the first curvature radius is 6cm, the abscissa of the vertex is 0, and the ordinate is 0.07cm, the corresponding second penumbra curve is the data line 5.

Step 360: and selecting a third penumbra curve with smaller numerical value and more gradual change in the third penumbra curve, wherein the vertex corresponding to the selected third penumbra curve is the first vertex.

As shown in fig. 4, the data lines 4 and 5 have a smaller value and a more gradual third penumbra curve as the data line 5. The vertex corresponding to the data line 5 is taken as a first vertex, that is, the abscissa of the first vertex is 0, and the ordinate is 0.07 cm.

After determining the first radius of curvature by step a, the first degree of curvature by step b and the first vertex by step c, performing step d to determine a first curve, wherein step d comprises:

step 370: and taking the blade of the first curve-shaped end face which has the first curvature radius and the curvature radius of the first vertex is the first curvature radius as the blade of the collimator, wherein the first curve is a smooth curve with the curvature radius gradually increasing from the vertex along the extending direction, and the bending degree of the first curve is the same as the first bending degree.

According to the first radius of curvature determined in step 320, the first degree of curvature determined in step 340, and the first vertex determined in step 360, a first curve may be determined, and the determined first curve shape may be used as the end shape of the first end of the collimator blade, so that the generated penumbra may be smaller and the variation may be more uniform.

In a specific implementation, the first curve, the second curve, and the third curve may be all curves representing even functions, may be all curves representing even functions after translation or rotation transformation, may be a part of curves representing even functions, and another part of curves representing even functions after translation or rotation transformation, and are not limited herein.

Wherein, the curve for representing the even function can be a parabola, a hyperbolic cosine curve or an arc on an ellipse connecting two endpoints of the short axis. For example, the first curve, the second curve and the third curve may all be parabolas, hyperbolic cosine curves or arcs connecting two endpoints of the short axis on an ellipse.

In specific implementation, a medical accelerator can be selected as the radiation source. The radioactive sources used for obtaining the first penumbra curve and the second penumbra curve may be the same or different, and are set by the person skilled in the art, which is not limited herein.

By applying the method for selecting the collimator blades provided by the embodiment of the invention, the blades with the first curve shape which can generate smaller and more uniformly-changed penumbra can be selected, so that the generated penumbra is close to a constant, and the radiation therapy is more favorably carried out.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. The collimator is characterized by comprising more than two blades, wherein the blades are oppositely arranged in two arrays, each array comprises more than one blade, each blade comprises an extension structure body, the extension structure body comprises a first end and a second end which are oppositely arranged along the extension direction, the end surface shape of the first end is a first curve, the first curve is a smooth curve of which the curvature radius is gradually increased from the vertex along the extension direction, the shape of the first curve and the position of the vertex are determined by the penumbra length corresponding to the blades of the end surface shapes with different vertexes or different curvature radii, and the collimator comprises the following steps:

2. The collimator of claim 1, wherein the first curve comprises a curve representing an even function and a curve obtained by translating or rotating the curve representing the even function.

3. The collimator of claim 2, wherein the first curve is a parabola, a bi-cosine curve, or an arc on an ellipse connecting two endpoints of a short axis.

4. The collimator of claim 2, wherein the first curve is a curve representing a linear combination of a plurality of even functions.

5. The collimator of claim 1, wherein each of the arrays comprises two or more leaves, the extension structure has a relief structure, and the reliefs of two adjacent leaves are mutually included.

6. The collimator of claim 1, wherein each of said arrays comprises a leaf.

7. The collimator of claim 1, wherein the shape of the first curve and the location of the apex determined by the penumbra lengths corresponding to vanes having end face shapes with different apices or different radii of curvature comprises:

determining a first curvature radius 'according to the penumbra length corresponding to the first end face in the case that the shape of the first end face is circular arcs with different curvature radii'

determining a first vertex according to the corresponding penumbra length when the first end surface is shaped into a curve with a first curvature radius and a first bending degree and the vertex of the curve is positioned at different positions vertical to the symmetry axis direction of the curve,

8. An irradiation system comprising a source of radiation for generating radiation and a collimator according to any one of claims 1 to 7, the collimator having first ends of the leaves adjacent one end of the other array opposite the array in which the leaves are located, the leaves being adapted to define a gap when positioned, the radiation source generating radiation which passes through the gap defined by the leaves of the collimator to impinge on a target area.

9. A method for selecting collimator blades is characterized by comprising the following steps:

a. determining a first radius of curvature:

determining a first curvature radius according to the corresponding penumbra length when the shape of the first end surface of the blade is circular arcs with different curvature radii:

b. determining a first bending degree, namely determining a curve with a first curvature radius at the vertex and different bending degrees according to the shape of the first end face of the blade

Determining a first degree of curvature from the corresponding penumbra length:

c. determining a first vertex:

determining the first vertex according to the corresponding penumbra length when the first end surface of the blade is shaped into a curve with a first curvature radius and a first bending degree and the vertex of the curve is positioned at different positions in the direction perpendicular to the symmetry axis of the curve:

d, determining a first curve: