JPH0326278A - Method for controlling positioning device for radiotherapy plan - Google Patents

Abstract

PURPOSE:To correct positional deviation caused by mechanism distortion and to make cross mark projection positions coincident for right and left pointers by calculating the feeding quantity of an arm module required for moving a mark from data to a position to be projected and moving the pointers to the desired positions. CONSTITUTION:The data, which are measured and stored in a muPU 10, are concerning B and D points. On a projecting surface in the B point of 20mm, the cross mark position is 19mm and on a projecting surface in the D point of 40mm, the cross mark position is 43mm. When the pointers are moved from an A point to a C point, moving quantity (a) is calculated at first by the position information of an origin and B point stored before and behind the position, which is the purpose of the move, and next, moving quantity (b) is calculated by the position information of the B and D points. For moving quantity (p) of an arm module 7L required for moving the pointers from the A point to the C point, the condition of (p)=(a)+(b)=18.64 is established. Then, when the number of pulsed to be sent to a left side pointer moving motor 5L for moving the arm module 7L by 1mm is defined as alpha, it is enough to send the 18.64alpha of the pulses. Thus, the cross mark is projected on a reagent enough exactly for a practical use.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a positioning device for radiation therapy planning for various high-energy radiation treatments, and particularly to a method of controlling the positioning device for radiation therapy planning.

(Prior art) Since the appearance of linear accelerators for cancer treatment,
Various radiotherapy devices have appeared, and Rl (Radio
Treatment devices using high-energy radiation, such as isotope therapy devices, electron beam/X-ray therapy devices, fast neutron therapy devices, and heavy ion particle therapy devices, have been successively developed and come into use. With the development of high-energy radiation therapy with remarkable therapeutic effects, more emphasis has been placed on highly accurate treatment planning. Radiation therapy equipment has been devised and developed to accommodate higher precision treatments, and at the same time, technology has progressed rapidly in terms of actual treatment planning and application, and the importance of treatment planning has become even more recognized. Became. The overall picture of the treatment system can be considered as follows.

The first step is diagnosis, in which the location, size, shape, etc. of the affected area are accurately determined. The second step is treatment planning, which comprehensively determines the application to the patient, including the type of treatment radiation, dose, and direction of irradiation, based on the various information obtained at the time of diagnosis.

The third step is to apply the treatment, locating, confirming, and irradiating the radiation field to the patient. Fourth
This stage is the management stage, in which data from each stage of diagnosis, planning, and application is collated, recorded, and stored for use as reference for treatment planning and after the completion of treatment.

There is a strong demand for a highly accurate treatment planning device that corresponds to these four stages as an indispensable tool, and one of them is a positioning device for radiation therapy planning.

This radiation therapy planning positioning device identifies the location of the affected area to be treated with radiation therapy using X-ray CT, etc., and projects a cross mark from the top and sides of the subject's body surface using a laser beam to begin radiation therapy. This is a device that performs positioning on the body surface when performing a laser marker, and is usually called a laser marker. Hereinafter, the positioning device for radiation therapy planning will be abbreviated as a marker.

This marker projects a laser beam from the upper and side surfaces of a subject who is lying on their back or side, to determine the position on the body surface of the affected area, and to appropriately grasp the irradiation position and irradiation field during radiotherapy. This is the device. Therefore, the marker has a pointer that projects a cross mark of laser light onto the body surface of the subject, and the pointer is mounted on an arm module and is configured to be moved horizontally or vertically by a step motor. The positioning is performed by projecting a cross mark using a laser beam from a pointer at the position where the radiotherapy of the subject is to be performed, which is calculated by the workstation. FIG. 4 is a diagram showing the arrangement of the pointer and the driving section of the marker mentioned above. In the figure, 1 is a central pointer installed on the ceiling of the X-ray CT room and projects a cross mark onto the upper surface of the patient, and 2L is a central pointer installed on the left wall of the treatment room with a cross mark on the left side of the patient. 2R is a right side pointer attached to the right wall. The central pointer 1 is placed on an arm module (not shown), and the arm is moved left and right by a central pointer moving motor 3 to determine its position.

4 is provided at the end of the moving rail, and the central pointer 1
Center pointer position sensors 5L and 5R are limit switches for limiting the amount of movement that would cause the left and right side to move off the rail, respectively.
A left side pointer movement motor and a right side pointer movement motor are used to vertically move and position the arm module (not shown) on which the right side pointer 2R is mounted, and a left side pointer position sensor 6L and a right side pointer position sensor 6 are used.
R prevents the limit position from being exceeded.

(Problem to be Solved by the Invention) By the way, the left side pointer 2L and the right side pointer 2R must face the subject and project the cross mark at the same position, but each pointer 2L, 2R must There is a distance of 2 m or more from the pointer to the subject's body surface, and the cross marks made by the left and right pointers often do not match due to distortion of the pointer feeding mechanism. This state is shown in FIG. The figure shows a left side pointer 2L as an example. This example shows a case where when the left hand pointer 2L is moved upward by 200 mm, the cross mark on the object projection screen is moved by 203 mm due to the distortion of the feed mechanism. A similar situation occurs with the right side pointer 2R, and the projections of the cross marks from the left and right pointers 2L and 2R do not match.

The present invention has been made in view of the above points, and an object of the present invention is to correct the positional deviation caused by mechanical distortion of the left side pointer and right side pointer, and to make the projection positions of the cross marks of the left and right pointers coincide. The aim is to realize this.

(Means for Solving the Problems) The present invention solves the above-mentioned problems by providing a pointer mounted on an arm module provided on the upper and left and right walls for projecting marks with light onto the body surface of a subject for radiation therapy. and a drive mechanism for moving the arm module, the position of the pointer and the position of the mark corresponding to the position of the pointer as the arm module moves in units are actually measured and the data is stored in a computer. a step of calculating a feed amount of the arm module necessary to move the mark to the position to be projected based on data stored in the computer; and a step of sending a pulse to the drive mechanism from the feed amount of the arm module. The present invention is characterized in that the step of calculating the number of pulses and the step of sending a signal of the number of pulses obtained by the calculation to the drive mechanism are omitted.

(Operation) The arm module carrying the pointer is moved unit by unit, and data regarding the relationship between the light irradiation position of the pointer and the projection position of the mark is stored in the computer.

To position the radiation irradiation position, calculate the amount of arm module feed needed to move the mark to the projection position from the above data, and then send the drive signal of the obtained number of pulses to the drive mechanism to move the pointer. Move it to the desired position.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a marker used to execute a control method according to an embodiment of the present invention. In the figure, the same parts as in FIG. 4 are given the same reference numerals. In the figure, 7S is an arm module to which the center pointer 1 is attached, and is used to move the center pointer 1 to the left and right of the figure and project a cross mark onto the upper body surface of the affected area of the subject, and 7L and 7R are arm modules, respectively. This is an arm module to which left and right side pointers 2L and 2R are attached, and for moving each pointer 2L and 2R up and down. Each arm module 7S 7L, 7R has a central pointer moving motor 3. which is a step motor. It is operated by a left side pointer movement motor 5L and a right side pointer movement motor 5R, and the position of each arm module, that is, the position of each pointer 1.2L, 2R, is determined by an encoder directly connected to the motor shaft of each movement motor 3, 5L, 5R. Detected. 8 is arm module 7s, 7
A hand controller is used to set the positions of L and 7R and to turn on and off the laser tubes of each pointer.The manual information is converted into infrared rays, detected by a photodetector 9, and input manually to a microcomputer (hereinafter referred to as μPU) 10. . μPUI
O controls the turning on and off of the laser tube based on the above input;
Controls each movement motor for movement of the arm unit. Reference numeral 11 denotes a CRT that displays position information of the arm modules 7S, 7L, and 7R and the on/off state of the laser tubes. The indoor light 12 is controlled by μPUIO, and is turned off when the laser tube is on to make the cross mark clear, and is turned on when the laser tube is off. Reference numeral 13 denotes a workstation that calculates and determines the position where radiation therapy is to be performed on the subject.

Next, the operation of the apparatus configured as described above will be explained, and then a control method for making the cross marks coincide will be explained. X
The affected area is identified by performing tomography or X-ray fluoroscopy using X-ray CT (not shown), and the identified affected area is marked for therapeutic radiation irradiation from the body surface. The hand controller 8 manually inputs the position of the arm module of each pointer to the μPU 10. μPUIO controls the center pointer movement motor 3, left side pointer movement motor 5L, and right side pointer movement motor 5R, and controls the arm module 7S of the center pointer 1, the arm module 7L of the left side pointer 2L, and the arm module of the right side pointer 2R. 7R
move the cross mark for positioning radiation irradiation to the affected area from the body surface.
Projection is performed using laser beams on the left and right sides. The position of each pointer is detected by an encoder directly connected to each moving motor shaft and displayed on the CRTII. The center pointer position sensor 4, left side pointer position sensor 6L, and right side pointer position sensor 6R detect when the center pointer 1, left side pointer 2L, and right side pointer 2R reach the start and end positions, respectively, and manually input the information to μPUIO. . Next, the hand controller 8 is used to manually turn on the laser tubes of each pointer, and a cross mark is projected onto the body surface of the subject. The lighting state of this laser tube is also displayed on the CRT 11. The interior light 12 is turned off when the laser tube is turned on, that is, when the cross mark is projected.

Next, a control method for matching the cross marks on the body surface from the left side pointer 2L and the right side pointer 2R will be explained. Consider the case where the left side pointer 2L is moved in the positioning operation.

The arm module 7L is moved by 20 mm and the position error of the cross mark on the projection plane is measured.

A graph of this position error is shown in FIG. The position error information on the projection plane obtained in this way is stored in the computer as a table of the relationship between the position of the pointer and the position of the cross mark, for example.

In the implementation stage of moving the arm module 7L to correctly project the cross mark, μPUIO controls the arm module 7L in the manner described below. A graph of the relationship between the position of the arm module 7L and the position of the cross mark on the projection plane is shown in FIG. In this graph, the data actually measured and stored in μPUIO are points B and D, and the cross mark position on the projection plane of point B of 20 mm is 19 mm, and the position of the cross mark on the projection plane of point D of 40 mm. is 43 mm. When moving from point A to point C, calculate the moving distance as follows.

(1) First, the amount of movement a is determined using the positional information of the origin and point B stored before and after the target position to be moved.

(2) Next, determine the amount of movement b based on the position information of points B and D.

(3) The amount of movement p of arm module 7L required to move from point A to point C is p = ub = IL 64 (4) Number of pulses sent to left side pointer movement motor 5L to move arm module 7L by 1 mm Letting α be, it is sufficient to send a pulse of 18.64α.

By doing the above, the cross mark can be projected onto the subject with sufficient accuracy for practical use. For even more accuracy, plot points may be plotted every 10 mm. The above procedure is similarly performed for the center pointer 1 and the right side pointer 2R.

As explained above, according to this embodiment, the amount of mechanical distortion can be corrected by software, and high-precision positioning can be performed without requiring mechanical precision. Therefore, a highly accurate positioning device can be realized at low cost. Furthermore, since the correction data table is measured and inputted for each system, stable positional accuracy can be guaranteed, and errors in arm module installation can also be corrected.

The positioning control method described in this embodiment can be applied to a positioning apparatus having a similar configuration, rather than a positioning apparatus for radiation therapy planning.

(Effects of the Invention) As described in detail above, according to the present invention, the central pointer. It is now possible to correct the mechanical distortion of the left side pointer and right side pointer using software, and to match the display positions of the left and right marks, which has a great practical effect.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the method of the present invention, Fig. 2 is a graph showing the relationship between arm module movement amount and cross mark position error, and Fig. 3 is a graph showing the relationship between arm module movement amount and cross mark position error, and Fig. 3 is a diagram showing an arm for correctly moving the cross mark. FIG. 4 is an explanatory diagram for calculating the amount of movement of the module, FIG. 4 is a diagram of the arrangement of a pointer in an X-ray CT room, and FIG. 5 is an explanatory diagram of the occurrence of an error in the amount of cross mark movement due to pointer movement. 1... Center pointer 2L... Left side pointer 2R... Right side pointer 3... Center pointer movement motor 4... Center pointer position sensor 5L... Left side pointer movement motor 5R... Right side Surface pointer movement motor 6L...Left side pointer position sensor 6R...Right side pointer position sensor 7L, 7R, 7S...Arm module 8...Hand controller 10...μPU 12...Interior light 11 ...CRT

Claims (1)

[Claims] A positioning system for radiation therapy planning that includes a pointer mounted on an arm module provided on the upper and left and right walls that projects a mark with light onto the body surface of a subject for radiation therapy, and a drive mechanism for moving the arm module. In the apparatus, the step of actually measuring the position of the pointer and the position of the corresponding mark by unit movement of the arm module and storing the data in a computer, and the position where the mark is to be projected based on the data stored in the computer. a step of calculating the amount of feed of the arm module necessary to move the arm module; a step of calculating the number of pulses to be sent to the drive mechanism from the amount of feed of the arm module; and a step of sending a signal of the number of pulses obtained by the calculation to the drive mechanism. 1. A method for controlling a positioning device for radiation therapy planning, comprising the steps of: