JPH01214343A - Ct image applying type treatment planning apparatus - Google Patents

Abstract

PURPOSE:To determine an accurate radiation field by determining the three-dimensional shape of the radiation field by indicating a target to each CT image using a large number of CT images sliced in a predetermined thickness and calculating the tangential line from a dotted line source with respect to each target and calculating the projection shape of the target on a special plane to calculate the radiation field. CONSTITUTION:With respect to all of the CT images inputted from a CT image input part 1 and stored in a data buffer part 2, targets are inputted by a target indication means 4. The calculation of planning data becoming necessary at the time of positioning of radiation treatment is performed by an operation apparatus 3. A projection shape calculation means 6 calculates the intersecting point of the tangential line calculated by a tangential line calculation means 5 and the plane (special plane) containing the center of rotation of a radiation treatment machine and vertical to the center axis of radiation beam and forms an image, which is obtained by projecting a tumor from a radiation dose position of radiation beam in the tangential direction, on the special plane. On the basis of the projection image calculated by the projection shape calculation means 6, a radiation field having to perform radiation treatment is accurately calculated by a radiation field calculation means 7.

Description

DETAILED DESCRIPTION OF THE INVENTION C. Industrial Field of Application The present invention relates to a CT image-utilizing treatment planning device that determines an irradiation field in radiation therapy using a large number of CT images sliced to a predetermined thickness.

[Conventional technology]

Conventionally, in this type of radiation treatment planning apparatus, the radiation treatment area has been determined by the following two methods. The first method is to use a single OCT image to treat an arbitrary shape (hereinafter referred to as
The second method is to enter a target on each CT image using a large number of predetermined slice thickness OCT images, and then specify the radiation source of the radiation therapy machine. Although it is actually a point ray source, it is calculated as a line ray source, and the projection shape of each CT image target is determined to determine the irradiation field.

[Problem to be solved by the invention]

In the former case, in the method of determining the radiation treatment area using the conventional radiation treatment planning system described above, the irradiation field is determined from a single OCT image, so the overall three-dimensional shape cannot be grasped and the irradiation field becomes ambiguous. There is a drawback; in the latter case, the radiation source of the radiation therapy machine is considered a radiation source, so
Since the pseudo irradiation field is calculated as if the radiation source were located on the extension of the sliced surface of each 07 image, it is significantly inaccurate compared to the case where the radiation source is calculated as an actual point radiation source. It had the disadvantage of becoming an irradiation field.

[Means to solve the problem]

The present invention includes a CT image input unit that inputs a plurality of images sliced to a predetermined thickness, a data buffer unit that stores the input images, and a data buffer unit that inputs an arbitrary shape to be a treatment target for the OCT image. A target specifying means for specifying each CT image and registering it as a target, a tangent calculation means for calculating a tangent to a target on the 07 image from the radiation source of the radiation therapy machine, which is regarded as a point radiation source, and rotation of the radiation therapy machine. projection shape calculation means for calculating the projected shape of the target by finding the intersection with the tangent in a plane that includes the central axis and is perpendicular to the central axis of the beam of radiation irradiated from the point source; and an actual radiation treatment including the projected shape. and an irradiation field calculation means for calculating the irradiation field for use.

[For production]

The present invention uses a large number of sliced 07 images for each 0
Targets are specified in 7 images, tangents from the point ray source are determined for each target, and the projected shape of the target is determined on a special plane to calculate the irradiation field, so an accurate irradiation field can be determined.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG.
This is a CT image input unit that inputs images.

07 Images can be input by connecting the CT device online or by transferring the CT image to a medium such as a magnetic tape or floppy disk. Next, 2
is a data buffer unit that stores the input 90T image; 4
is a target specifying means for specifying an arbitrary shape to be treated with respect to the 07 image in the data buffer section and registering it as a target. 5 is a tangent calculation means for calculating a tangent to a designated target from the radiation source of the radiation therapy machine, which is considered to be a point radiation source; 6 is a beam of radiation that includes the rotation center axis of the radiation therapy machine and is irradiated from the point radiation source; Projected shape calculating means for calculating the projected shape of the target by finding the intersection with the tangent in a plane perpendicular to the central axis; 7 is an irradiation field calculating means for calculating the actual radiation treatment field including the projected shape; a is 0 used in target specification means 4.
7 is a display unit that displays images and also displays the calculation result of the actual radiation treatment irradiation field; 9 is a keyboard;

Note that 3 is a target specifying means 4. Tangent calculation means 5. Projection shape calculation means 6. It is a calculation device consisting of an irradiation field calculation means T, and stores the target designated by the target designation means 4.

In this case, CTiji refers to a large number of 007 images obtained by slicing an area with a desired thickness such that a malignant tumor located in an arbitrary area within the patient's body is to be treated. The slice position in this CT image is usually expressed in relation to the z@ value, where the body axis extends from the feet to the head K and is defined as the z axis. The position of Z=Q is determined to be a position that passes approximately through the center of the tumor, but even if it is determined to another position, it will not affect the treatment plan.

In this case, relative coordinates are used with the center of the tumor as z=0.

Next, the operation of this embodiment will be explained.

First, the target designation means 4 uses the target designation means 4 for the 07 image input from the CT image input unit 1 and stored in the data buffer 2.
A target is input for all CT images K. Hereinafter, calculation of planning data necessary for positioning for radiation therapy is performed by the calculation device 3.

In calculating the plan data, first, the gantry rotation center position and gantry rotation angle of the radiation therapy machine are determined, and then the three-dimensional positional relationship on the treatment table when the patient is placed at a predetermined position fllc is determined. This gantry rotation center, gun)
After determining the IJ rotation angle, the shape of the treatment irradiation field is determined so that the radiation beam of the radiation therapy machine accurately irradiates the tumor affected area.

The shape of this irradiation field can be determined by using the radiation therapy machine's radiation source as a point radiation source and drawing a number of line segments tangential to the tumor affected area to obtain a treatment area that envelops the tumor area as a whole. The tangent line calculation means 5 calculates this tangent line by drawing a tangent line from the source position of the radiation beam to each target of a large number of 07 images sliced perpendicularly in the Z-axis direction, and calculating the line in the three-dimensional space of the tangent line. Find the fractional formula by calculation.

Next, the projection shape calculation means 6 calculates the intersection of the 7'C tangent obtained by the tangent calculation means 5 and a plane (hereinafter referred to as a special plane) that includes the rotation center of the radiation therapy machine and is perpendicular to the radiation beam central axis. Then, an image of the tumor projected tangentially from the source position of the radiation beam is formed on a special plane. In this case, 0
Since the 7 images are taken at predetermined intervals, they are input as the tumor shape, and the 9 targets have shapes that discretely represent the actual tumor shape. For this reason, for example, two C
The shape of the tumor existing between T images can be estimated in a pseudo-analogous manner by interpolating between the images.

Then, based on the projection image obtained by the projection shape calculation means 6, the radiation field calculation means 7 accurately calculates the radiation field in which radiation therapy should be performed.

Next, a perspective view of the 07 image is shown in a tgz diagram.

In the figure, two OCT images 10.11 sliced at a predetermined thickness each include a target 12.13. Also, among the C7 images 10.11, the 07 image generally handled by a treatment planning device has a center 0 that passes through the center of a slice of a predetermined thickness.
7 images IQa, 11a, and accordingly, the targets are 12a, 13a on the central CT image 10, 11a. 14 is a gantry rotation center axis, 15 is a point source position of the radiation beam of the radiation therapy machine at an arbitrary gantry rotation angle, 16 is a line source axis that includes the point source position 15 and is parallel to the gantry rotation center axis 14; is a point that intersects the line source axis 16 in the 07 image. 19.20 is point 17
The tangent line drawn from to the target 12a, 21.22
is the tangent line drawn from point 18 to target 131, 2
3 is a special plane that is perpendicular to the radiation beam center axis 24 and includes the gantry rotation center axis 14t; 25, 26, 27, 28 are the intersections of the tangents 19, 20, 21, 22 and the special plane 23;
29.30 is the tangent drawn from point 15 to target 12aK, 31.32 is the tangent drawn from point 15 to target 13a, 33.34 is the intersection of tangent 29.30 and special plane 23, 35. 36 is the intersection of the tangents 31 and 32 and the special plane 23. Conventionally, the point 17. on the line source 16.
18 to target 12a.

The range of the straight line connecting the tangent lines 19, 20, 21.22 drawn to 13a and the intersection points 25.26, 27.28 with the special plane 23 was determined as the irradiation field, but in reality it was drawn from the point source 15. The range of the straight line connecting the intersection points 33, 34, and 35.36 of the tangent lines 29.30 and 31.32 with the special plane 23 is the true irradiation field, and the conventional irradiation field and the true irradiation field are different. It becomes the shape.

Next, the shapes of the conventional irradiation field and the true irradiation field will be explained in detail with reference to FIG. (a) The figure shows σ image 40~
46 is a side sectional view of FIG.佽）The figure is special plane 2
Point source on 3 15. 3 is a diagram showing an irradiation field by a line radiation source 16. FIG.

In the figure, sliced CT images 40 to 46 exist on the gantry rotation center axis 14, and the slice positions t in the Z-axis direction are Z=-6, -4°-2, 0, 2, 4, respectively. 6
It is. The targets 40T to 46T specified on the CT images 40 to 46 are expressed as side images viewed from an infinite distance on the special plane 23. In the conventional case where the source of the radiation beam is the line source axis 16, the irradiation field is determined as follows from the intersections 47 to 60 of the special plane 23 and tangents drawn from the axis 16 to the target planes 40T to 46T.

For the irradiation field, a rectangular shape (attribute area) is determined for each target, and the sum of the attribute areas is defined as the irradiation field 91. The rectangular attribute area of each target is obtained by first drawing the center axis a of the ZCT image in any two adjacent 07 images, and then drawing the left side area of the center axis a using the intersection points 47 to 60 as a reference. In some cases, the height of the target of the 07 image adjacent to the left side is set, and the right area is set to the height of the 07 image on the right side. This is the same as the rectangular shape when perpendicular lines are drawn from the intersections 47 to 60 to the central axis a of each 07 image. This rectangular shape is the R-type region, and the sum total thereof becomes the irradiation field 91. The rightmost and leftmost ends of each rectangular shape of this irradiation field 91 are set to have a shape obtained by expanding the positions of the intersections 47 to 60 from the center of the 2CT image to the left and right by 1/2 pitch of the interval of the 07 images.

Next, an explanation will be given of the irradiation field when the point radiation source 15 is used as the radiation source in this embodiment.

First, the intersection of the tangent line drawn from the point source 15 to the targets 40T to 46T and the special plane 23 is 50,57°61 to 63.6
Find 4-66.67-69.70-72, then each 07
Find the attribute area in the image. For example, in the case of the CT image 40, a rectangular area surrounded by points 80, 81, 82, and 83 is defined as an attribute area. In this way, the attribute area is determined for each 07 image, and the sum of the attribute areas is calculated as the irradiation field 9.
Set to 0. Note that the axis connecting the center point of point 80, 81 and the center point of points 82° and 83 is obtained by drawing a tangent from the point ray source 15 to the logical contour line 84, which is the outermost circumferential line of the CT image. It coincides with the line connecting the intersection points 61 and 67 with the special plane 23. This intersection 61 is on the line connecting points 80.81, and the intersection 6T is on the line connecting points 82.83. point 80 here
．． 82 is left and right Kl from the center point between the CT images! ! This is a point expanded by 1/2 of the projected slice pitch P obtained by connecting the intersection of the grain contour line 84 and the special plane 23.

In this way, it is clear that the conventional irradiation field 91 has a narrower range and a shifted position compared to the true irradiation field 90 according to this embodiment, and it is extremely inaccurate in the conventional case where the radiation source is a silver ray source. However, in this embodiment where the radiation source is a point source, an accurate radiation field can be calculated.

〔Effect of the invention〕

The present invention uses a large number of CT images drawn to a predetermined thickness, specifies a target in each 07 images, determines the tangent line from a point source for each target, determines the projected shape of the target on a special plane, and irradiates it. Since the field is calculated, the three-dimensional shape of the irradiation field can be grasped and the irradiation field can be determined as a regular N-table irradiation field, rather than the inaccurate irradiation field when the radiation source is a silver radiation source as in the past. It has the effect of being able to do the following.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a perspective view of a 07 image, and FIG. 3 is a sectional view showing a conventional irradiation field and a true irradiation field after correction. 1...Fist/CT image input unit, 2...Fist deme buffer, 3...Arithmetic unit fl, 411 fist 11 I target designation means, 5...Φ tangent calculation means, 6...Projection shape Calculation means, 7... Irradiation field calculation means, 8...φ
・Display section, 90 meetings...keyboard. Patent applicant: NEC Corporation

Claims (1)

[Claims] C inputting a plurality of CT images sliced to a predetermined thickness
a T-image input section; a data buffer section for storing input CT images; and a target specifying means for specifying an arbitrary shape to be treated as a target for each CT image in the data buffer section and registering it as a target. , a tangent calculation means for calculating a tangent to a target on a CT image from a radiation source of a radiation therapy machine, which is regarded as a point radiation source; and a beam center of radiation irradiated from the point radiation source that includes the rotation center axis of the radiation therapy machine. In the plane perpendicular to the axis,
CT characterized by comprising a projection shape calculation means for calculating the projection shape of the target by finding the intersection with the tangent line, and an irradiation field calculation means for calculating the irradiation field for actual radiation therapy including the projection shape. Image-based treatment planning device.