JP2001129104A - Multi-leaf collimator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a multi-collimator which has difficulty in precise positional detection since positional detection by pulses from an encoder can be deviated from the true position of leaf blocks by long-period driving of the multi-collimator since there is back lash between a gear and a rack part since the gear is revolved by the revolution of a motor to move the leaf blocks by the rack part 18 to be fitted with the gear in the positional detection of the leaf blocks 10 of the multi-collimator. SOLUTION: A pair of leaf blocks are overlapped in a direction vertical to a moving direction, plural resistors which are arrayed mutually in contact with adjacent ones in the moving direction and are different from each other in specific resistance are provided on each leaf block, and by a pair of electrodes fixed respectively in contact with the resistors of the different specific resistances, fixed voltage is applied to the resistor between the pair of electrodes to measure a current value or a resistance value corresponding to the resistor to detect the position of each leaf block.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-leaf collimator according to a radiotherapy apparatus, and more particularly to the detection of the position of a leaf block in a multi-leaf collimator.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram of a leaf drive mechanism of a multi-leaf collimator disclosed in Japanese Patent Application Laid-Open No. 11-216197. In FIG. 8, the multi-leaf collimator is configured by arranging a large number of pairs of a pair of leaf blocks 1 which can be separated from and contact with each other, in a direction perpendicular to the driving direction. When the motor 3 attached to the frame 2 is rotated, the gear 4 rotates and the leaf block 1 provided with the rack portion 5 meshing with the gear 4 is driven. Generate a signal. Since the moving distance of the leaf block 1 is proportional to the number of pulses, the moving distance, that is, the position of the leaf block 1 can be detected by counting the number of pulses.

[0003]

As described above, the conventional position detection of the leaf block 10 is performed by the rotation of the motor 20 so that the gear 19 rotates and meshes with the gear 19.
8 to move the leaf block 10
Since there is a backlash between the rack 9 and the rack unit 18, there is a possibility that a long time driving of the multi-collimator causes a difference between the position detection by the pulse from the encoder 22 and the true position of the leaf block 10. There is a problem that it is difficult to detect a position with high accuracy. Further, when the number of leaf blocks 10 increases, it is required to reduce the size of components such as motors, gears, and racks, so that it is difficult to accurately detect the position with the same configuration as in the related art. .

Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to provide a novel multi-leaf collimator capable of accurately detecting the positions of a plurality of leaf blocks in a multi-leaf collimator. I do.

[0005]

According to a first aspect of the present invention, there is provided a multi-leaf collimator in which a pair of leaf blocks extending in a moving direction of moving away from or approaching each other are overlapped in a direction perpendicular to the moving direction. A leaf block group, a driving unit for driving each leaf block of the leaf block group in the moving direction, and a plurality of adjacent blocks arranged in contact with each other in the moving direction on the leaf blocks and having different resistivity from each other. A resistor, a pair of electrodes fixed in contact with a resistor having a different resistivity, and applying a constant voltage to the resistor between the pair of electrodes to obtain a current value or a resistance value corresponding to the resistor. It comprises a measuring means for measuring and a detecting means for detecting the position of the leaf block related to the measurement based on the current value or resistance value of the measuring means.

In the multi-leaf collimator according to a second aspect of the present invention, the driving means includes a rack portion provided on an upper surface or a lower surface of a through hole formed in each leaf block.
The leaf blocks are moved by driving gears meshing with the rack. Claim 3 of the present invention
The multi-leaf collimator according to (1) is provided with a stopping means for comparing the value measured by the measuring means with a fixed value, and stopping the driving means when the measured value exceeds the fixed value.

In the multi-leaf collimator according to a fourth aspect of the present invention, the stopping means is provided in each of the pair of leaf blocks.

A multi-leaf collimator according to a fifth aspect of the present invention is a multi-leaf collimator comprising a leaf block group in which a pair of leaf blocks extending in a moving direction that are separated from or approaching each other are overlapped in a direction perpendicular to the moving direction. A driving unit for driving each leaf block of the leaf block group in the moving direction, an encoder for generating a pulse signal corresponding to the driving of the driving unit, and a position of the leaf block by counting the pulse signal by the encoder Detecting means, a plurality of resistors having different resistivities arranged adjacent to each other in the moving direction on the leaf blocks, and a resistor having a different resistivity. A fixed voltage is applied to a pair of electrodes fixed by applying a constant voltage to a resistor between the pair of electrodes, and a current value or resistance corresponding to the resistor is applied. , A second detecting means for detecting the position of the leaf block based on a current value or a resistance value by the measuring means, and comparing the detected value of the first and second detecting means with the leaf. Comparing means for specifying the position of the block.

According to a sixth aspect of the present invention, there is provided a multi-leaf collimator provided with an interlock circuit for stopping the driving means when each of the detected values by the first and second detecting means exceeds a predetermined range. Things.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The detection of the position of a leaf block in a multi-leaf collimator according to a first embodiment of the present invention will be described below. FIG. 1 is an explanatory diagram for describing position detection of a leaf block. In FIG. 1, reference numeral 10 denotes one leaf block, in which a number of leaf blocks are arranged in a direction perpendicular to the plane of the paper. Reference numeral 23 denotes a plurality of resistors, which are arranged on the upper surface of each leaf block 10 so as to be in contact with each other without any gap along the moving direction of the leaf block 10. As shown in the plan view of FIG. 2, the plurality of resistors 23 for one leaf block 10 have different resistivity from each other. For example, the leaf blocks 10 are arranged along the moving direction so that the resistivity monotonically increases or monotonically decreases. Such a resistor 23 is arranged in each of the plurality of leaf blocks 10. Reference numeral 11 denotes a pair of electrodes, which are in contact with the resistor 23 and fixed by fixing means (not shown). The distance between the pair of electrodes 11 is set to be larger than the length of each resistor 23 in the moving direction. 51 is a pair of electrodes 1
A power supply 50 for applying a voltage to 1 is an ammeter for measuring a current flowing through the pair of electrodes 11 to the resistor 23 between the electrodes 11. Reference numeral 20 denotes a motor, and reference numeral 19 denotes a gear. The gear 19 meshes with a rack portion engraved on the lower surface of the leaf block 10, and moves the leaf block by driving the motor 20. In FIG. 1, one system of position detection means is provided for each leaf block as described above, but a configuration in which a plurality of such position detection means are provided for each leaf block may be employed. In this case, more accurate position information can be obtained by comparing values obtained by detecting the positions of the plurality of systems and performing appropriate correction. Further, the configuration for moving the leaf block 10 may be a configuration as shown in FIG. In FIG. 3, reference numerals 18 denote holes penetrating the side surfaces of many leaf blocks 10, and a rack portion meshing with the gear 19 is formed on the upper surface of these holes. Of course, a rack may be formed on the lower surface of these holes. Thus, the leaf block 10 is moved by the rotation of the gear 19.

The gear 19 is rotated by the drive of the motor 20, and the gear 19 meshes with a rack section engraved on the leaf block 10 to move the leaf block 10. At this time, a current flows from the power supply 51 to the resistor 23 through the electrode 11, and the current at this time is measured by the ammeter 50. Since the resistance value of each resistor 23 has a unique value, the leaf block 1 depends on the current value of the ammeter 50.
Identify the position of 0. The position of the leaf block 10 is specified by, for example, the position of the leaf block 10 and the ammeter 50.
The measured current value is previously associated with the current value, and this is stored in the storage means. When the drive of the motor 20 is stopped when the current value obtained by the ammeter 50 reaches a predetermined current value,
The leaf block 10 can be stopped at a position corresponding to the current value. Alternatively, a resistance value between the electrodes 11 may be measured, and the position of the leaf block 10 may be detected in accordance with the resistance value. On the other hand, when the leaf block 10 is stopped at a certain position, the ammeter 5
By measuring the current value according to 0, the position of the leaf block 10 can be detected. The information of the position of the leaf block 10 detected in this way is output as image information to a cathode ray tube monitor or the like, and at the same time, an image of the tumor is output, and it is possible to confirm the coincidence between the tumor and the irradiation field of the multi-leaf collimator. As shown in FIG. 3, each leaf block 10 may be moved by engaging a gear 19 with a rack portion engraved on the upper surface or the lower surface of the hole 18. In this case, the size of the multi-leaf collimator can be reduced. It is particularly useful when using a large number of leaf blocks.

Next, a second embodiment of the present invention will be described.
This will be described with reference to FIG. 4, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and a description thereof will not be repeated. FIG.
, 22 is an encoder of the motor 20;
A pulse signal is generated according to the rotation of the rotating shaft of the motor 20. Therefore, if the amount of movement of the leaf block 10 is determined by one rotation of the rotating shaft of the motor 20, the amount of movement, that is, the position of the leaf block 10 can be detected by counting this pulse signal. In the second embodiment,
The leaf block 10 based on the counting of such pulse signals
Of the leaf block 10 by detecting the position of the resistor and measuring the value of the current flowing through the resistor 23 described in the first embodiment.
And the detection of the position. In FIG.
Reference numeral 53 denotes a comparison device that compares the above two detected values. If these detected values are very close, the position of the leaf block 10 is highly reliable. Actually, if these values are within a predetermined range, the position of the leaf block is detected by any one or the average value of these. If these values do not fall within the predetermined ranges, it is determined that there is a backlash between the gear 19 and the rack portion, and a correction amount in consideration of the backlash is added to detect the position of the leaf block with higher accuracy. it can. However, if those values exceed a predetermined range, an unexpected serious failure may occur. Therefore, an interlock circuit 55 is provided as shown in FIG.
By operating the interlock circuit 55, the driving of the multi-leaf collimator can be stopped, and the generation of radiation can be stopped. In FIG. 4, the case where the above-described two detecting means are used in combination with each leaf block has been described. However, it is needless to say that a plurality of two detecting means may be provided in each leaf block. In this case, the reliability at the position of the leaf block 10 can be further improved by further comparing the values of the positions of the plural systems.

Next, a third embodiment of the present invention will be described.
This will be described with reference to FIG. FIG. 5 shows a pair of leaf blocks 1
0 is an explanatory diagram for detecting the position of each leaf block 10 and preventing collision due to movement of each leaf block 10. The detection of the position of each leaf block 10 is provided with a resistor 23, an electrode 11, an ammeter 50, a gear 19, and the like for each leaf block 10, and is the same as that of FIG. In FIG. 5, reference numeral 53 denotes a comparison device. When each leaf block 10 moves in a direction approaching each other, if both leaf blocks 10 move any more, the current value of each leaf block 10 at the time of collision with each other. Is stored as a limit value. When the current value at the position of each leaf block 10 is input from each ammeter 50 to the comparison device 53, the comparison device 53 always compares these current values with the stored limit value, and these current values are When the limit is exceeded,
A stop signal for stopping the driving of the corresponding motor 20 is output. Upon receiving the stop signal, the motor 20 immediately stops its drive, and the leaf block 10 stops its movement. Thus, it is possible to prevent the pair of leaf blocks 10 from colliding with each other, so that the leaf blocks 10 can be prevented from being damaged.

Next, a fourth embodiment of the present invention will be described.
This will be described with reference to FIG. In FIG. 6, 53 is a comparison device, and 55 is an interlock circuit. The comparison device 53 is
When detecting that the current value of the ammeter 50 is abnormal for some reason, the comparison device 53 operates the interlock circuit 55. This abnormal value may correspond to a value that cannot be taken such that the current value far exceeds a current value determined by the voltage value of the power supply 51 and the resistance value of the resistor 23 within a certain range. At this time, the interlock circuit 5
Numeral 5 stops driving of the multi-leaf collimator, and further stops generation of radiation. 6, other configurations are the same as those described with reference to FIG.

[0015]

As described above, according to the present invention, the position of each leaf block can be accurately detected by measuring the current value or the resistance value flowing through the resistor provided on the leaf block in the multi-leaf collimator. The consistency between the tumor and the irradiation field of the multi-leaf collimator can be further ensured.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a configuration of a multi-leaf collimator according to the present invention.

FIG. 2 is an explanatory diagram for explaining a configuration of a resistor provided in a leaf block of the multi-leaf collimator according to the present invention.

FIG. 3 is an explanatory diagram for explaining another configuration of the multi-leaf collimator according to the present invention.

FIG. 4 is an explanatory diagram for explaining another configuration of the multi-leaf collimator according to the present invention.

FIG. 5 is an explanatory diagram for explaining another configuration of the multi-leaf collimator according to the present invention.

FIG. 6 is an explanatory diagram for explaining another configuration of the multi-leaf collimator according to the present invention.

FIG. 7 is an explanatory diagram for explaining another configuration of the multi-leaf collimator according to the present invention.

FIG. 8 is an explanatory diagram for explaining a configuration of a conventional multi-leaf collimator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Leaf block 11 Electrode 18 Rack part 19 Gear 20 Motor 23 Resistor 50 Ammeter 51 Power supply 53 Comparison device 55 Interlock circuit

Claims (6)

[Claims] 1. A leaf block group in which a pair of leaf blocks extending in a moving direction that is separated from or approaching each other are overlapped in a direction perpendicular to the moving direction, and each leaf block of the leaf block group is moved in the moving direction. And a plurality of resistors having different resistivities arranged adjacent to each other in the moving direction on the respective leaf blocks, and a resistor having a different resistivity is fixed in contact with each other. A pair of electrodes, measuring means for applying a constant voltage to a resistor between the pair of electrodes and measuring a current value or a resistance value corresponding to the resistor, and measuring the current value or the resistance value by the measuring means. A multi-leaf collimator comprising: a detection unit that detects a position of a leaf block related to measurement. 2. The driving device according to claim 1, wherein a rack portion is provided on an upper surface or a lower surface of a through hole formed in each of the leaf blocks, and each of the leaf blocks is moved by driving a gear meshing with the rack portion. The multi-leaf collimator according to claim 1. 3. A stopping means for comparing a value measured by said measuring means with a constant value and stopping said driving means when the measured value exceeds said constant value. 2. The multi-leaf collimator according to 1. 4. The multi-leaf collimator according to claim 3, wherein said stopping means is provided in each of said pair of leaf blocks. 5. A leaf block group in which a pair of leaf blocks extending in a moving direction that is separated from or approaching each other are overlapped in a direction perpendicular to the moving direction, and each leaf block of the leaf block group is moved in the moving direction. A driving means for driving the driving means, an encoder for generating a pulse signal corresponding to the driving of the driving means, a first detecting means for detecting the position of the leaf block by counting the pulse signals by the encoder, A plurality of resistors having different resistivities arranged adjacent to each other in the moving direction on each leaf block, a pair of electrodes respectively contacted and fixed to the resistors having different resistivities, Measuring means for applying a constant voltage to the resistor between the electrodes to measure a current value or a resistance value corresponding to the resistor; Is a second detecting means for detecting the position of the leaf block by a resistance value, and the first and second detecting means
And a comparing means for comparing the detection values of said detecting means to specify the position of the leaf block. 6. An interlock circuit according to claim 5, further comprising an interlock circuit for stopping said driving means when each detected value of said first and second detecting means exceeds a predetermined range. Multi-leaf collimator.