JP4301117B2 - Multi-leaf collimator - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a multi-leaf collimator, which is a multi-leaf collimator that regulates an irradiation field in cancer treatment using particle beams, and can significantly reduce the number of actuators required for driving while improving resolution by making the leaf thin. Simplification and cost reduction can be achieved.

  In recent years, treatments using particle beams such as proton beams and elementary particle beams have been carried out for cancer treatment, and the particle beam produced by the accelerator is processed into the shape of the cancer affected area using an irradiation field forming device. To irradiate.

  In this irradiation field forming apparatus, the particle beam emitted from the accelerator is subjected to the following operation to form a cancerous part.

 First, the particle beam emitted from the accelerator is vibrated by a wobbler electromagnet into a donut shape, and then the donut-shaped beam is made flatter by a scatterer.

  Then, the energy level is adjusted by a range shifter so as to adjust the dose peak so as to match the cancer affected area, and the beam is thickened by the ridge filter.

  Finally, the processing is completed by matching the processed beam with the shape of the cancer affected area using a collimator.

  A collimator is used to perform an operation for matching such a processed beam to the shape of the cancerous part, and one of them is a multi-leaf collimator.

  As shown in FIG. 5, for example, the multi-leaf collimator disclosed in the prior art of Patent Document 1 has a thin plate-like leaf 1 made of a material capable of shielding the particle beam B arranged in a vertical direction, and a large number of them in the horizontal direction. A pair of leaves 1 arranged side by side are opposed to each other and intersect with the particle beam B (usually orthogonal) to be arranged.

 Then, the space 2 formed by adjusting the distance between the opposing leaves 1 and the position thereof by the drive mechanism is used as an irradiation portion of the beam B, and the beam B is shielded by the other leaf 1 portions. The contour shape of the cancer affected part is reproduced by changing the positions of many leaves 1.

  In such a multi-leaf collimator, it is necessary to reciprocate and position each thin plate-like leaf, and as a driving mechanism, Patent Document 2 discloses independent driving for each leaf 1 as shown in FIG. As a mechanism, a rack 3 is provided on the upper end surface of the leaf 1, and each pinion 4 that meshes with the rack 3 of each leaf 1 is driven by each motor 5 to reciprocate. Has been.

Further, in Patent Document 3, as shown in FIG. 7, a common driving unit for a plurality of leaves 1 and a driving force of the driving unit can be transmitted to the plurality of leaves 1 at the same time. Specifically, for example, in each right leaf 1, a rack 3 is attached to the lower surface of the U-shaped cutout portion of each leaf 1 and is driven by one motor 5. Long pinions 4 can be meshed with a plurality of racks 3, and each leaf 1 can be moved up and down by a cylinder 6. The transmission of power is cut off and stopped by releasing the meshing of the two, and the positions of the plurality of leaves 1 can be held by pressing the entire leaf 1 with the brake plate 7. In each leaf on the left side, the rack is attached to the upper surface of the notch, and the mesh is disengaged by lowering each leaf.
Japanese Examined Patent Publication No. 7-67491 JP 11-216197 A JP 2002-224230 A

  When reproducing the necessary irradiation field using such a multi-leaf collimator, the accuracy of the outline of the irradiation image projected on the isocenter is affected by the thickness of the leaf and the gap between adjacent leaves, that is, the pitch. It is better that the thickness of the leaf is thin. Usually, a multi-leaf collimator is configured by arranging a large number of thin leaves.

  For this reason, if the drive mechanism for each leaf is composed of a rack, a motor, and a pinion, the same number of motors as the number of leaves must be installed side by side, which requires a large space and a large cost. There's a problem.

  On the other hand, one drive mechanism drives a plurality of leaves, the transmission of driving force is blocked by a lifting cylinder at a predetermined position, and after stopping the driving of all the leaves, it is held by one brake plate. However, although all the leaves can be driven, a lift cylinder is required for each leaf, and there is a problem that a large space and cost are required for this purpose.

  In addition, when holding all the leaves with one brake plate, the holding force tends to vary from leaf to leaf due to wear and other factors. In extreme cases, the leaf may be misaligned or cannot be held. The leaf which becomes becomes may occur.

  Furthermore, the position of the leaf is performed by an encoder that is coaxial with one motor, and even if a positional deviation occurs in one of the leaves, it is difficult to know the amount of deviation, and the positional deviation itself can be corrected. There is also the problem that it is difficult.

  The present invention has been made in view of the problems of the prior art, and reduces the number of devices required for driving while improving the resolution by reducing the leaf shape to reduce the drive mechanism and reduce the cost. Therefore, an object of the present invention is to provide a multi-leaf collimator that can easily form an irradiation field with high accuracy.

  In order to solve the above-described problems of the prior art, a multi-leaf collimator according to claim 1 of the present invention is a multi-leaf collimator that crosses the irradiation direction and opposes each other and adjusts the facing interval of a plurality of leaves to form an irradiation field. In the collimator, a member that can transmit a particle beam having an outer surface formed in the shape of the irradiation field, a pressing unit that is provided in each of the plurality of leaves and presses the tip surface of each leaf against the member. It is characterized by comprising leaf opening means for positioning the entire plurality of leaves in the fully open position.

  According to this multi-leaf collimator, the irradiation field can be easily adjusted by pressing the tip of each leaf equipped with a pressing means composed of a spring or the like to the outer surface of the member to be made in accordance with the shape of the irradiation field. The leaf opening means allows all the leaves to be opened at once, and the mechanism is simplified by reducing the number of actuators as much as possible.

Further, the multi-leaf collimator according to the present invention is configured in addition to the configuration according to claim 1, wherein the profile member is also used as a bolus for regulating the irradiation depth of the particle beam, or each leaf to the profile member is Contact detection means for detecting contact may be provided at the front end and / or rear end of each leaf.

  According to these multi-leaf collimators, it becomes possible to easily create a fake member simply by processing the outer surface when forming a bolus, and it is possible to know whether or not the irradiation field has been reliably set by the contact detection means. It becomes like this.

  According to the multi-leaf collimator according to claim 1 of the present invention, the outer surface of the profile member that can transmit the particle beam is matched with the shape of the irradiation field, and the tip of each leaf is pressed against the outer surface of the profile member. Therefore, it is possible to easily adjust the irradiation field by simply pressing the leaf without performing special position control or position detection.

  In addition, since all the leaves can be opened at once by the leaf opening means, the number of actuators can be reduced as much as possible to simplify the leaf drive mechanism.

  In addition, according to another multi-leaf collimator of the present invention, it is possible to easily create a flawless member simply by processing the outer surface during bolus formation, and whether the irradiation field can be reliably set by the contact detection means. Can know.

Hereinafter, an embodiment of a multi-leaf collimator of the present invention will be described in detail with reference to the drawings.
1A and 1B show an embodiment of a multi-leaf collimator according to the present invention. FIG. 1A is a schematic plan view of an irradiation field forming state showing a part of a right leaf, and FIG. 1B is a schematic plan view of a fully open state of the leaf. is there.

  In this multi-leaf collimator 20, a thin plate-like leaf 21 made of a material capable of shielding particle beams is arranged vertically and arranged in a large number horizontally, and the horizontally arranged leaves 21 are opposed to each other. (In the figure, only the right-sided opposing leaves are shown.), The space formed by adjusting the distance between the opposing leaves 21 and their positions by the drive mechanism 30 (in the figure, the left end of the leaves) The space formed in the part) is used as an irradiation field 22 to be a beam irradiation part, and the beam is shielded by the other leaf 21 part, and the positions (opposite intervals) of the many leaves 21 are followed by the drive mechanism 30. By changing them accordingly, the irradiation field 22 corresponding to the contour shape of the cancer affected part is reproduced.

  The follower driving mechanism 30 of the multi-leaf collimator 20 includes a member 31 having an outer surface formed in a shape corresponding to the contour to be irradiated with the particle beam, and the plurality of leaves 21 are individually provided with the tips of the leaves 21. A pressing means 32 for pressing against the profile member 31 is provided, and a leaf opening means 33 for returning all the leaves 21 pressed against the profile member 31 back to the open position (fully open position) is provided.

  The profile member 31 of the profile drive mechanism 30 is arranged so as to be sandwiched between the opposing leaves 21 and irradiates the particle beam as it is. Therefore, the profile member 31 is made of a material that can transmit the particle beam, and its outer surface 31a has a particle size. It is formed in a shape corresponding to the outline of the irradiation field to be irradiated with the line.

  Therefore, for example, when used for radiotherapy for cancer, the tracing member 31 is manufactured each time according to the shape of the cancer of each patient.

  As shown in FIG. 2, this tracing member 31 is also used as a bolus 41 that regulates the irradiation depth of the particle beam, the outer surface 31a is processed into the contour shape of the irradiation field, and the irradiation depth is inside. If the concave portion 41a for adjusting the height is processed, it is only necessary to add the processing of the outer surface to the manufacture of the conventional bolus, and it is possible to manufacture the profile member 31 easily and without greatly increasing the number of manufacturing steps. Can do.

  Next, the pressing means 32 for positioning each leaf 21 by pressing against such a profile member 31 is, for example, a rear end surface of each leaf 21 mounted on the case main body 23 of the multi-leaf collimator 20 so as to be reciprocally movable. The guide rods 21a are coupled to each other, and a spring 32a is attached between the rear end face of each leaf 21 and the case main body 23 along the guide rods 21a, and urged to push forward.

  Note that the pressing means 32 is not limited to the case where the spring 32a is attached to the guide rod 21a, but may be constituted by a fluid pressure cylinder such as an air cylinder using compressed air.

  Each leaf 21 is automatically pressed against the follower member 31 by sandwiching the follower member 31 between the opposing surfaces of the respective leaf 21 provided with the pressing means 32, and position control of each leaf 21 is performed. Therefore, the irradiation field 22 can be easily adjusted.

  In this follow-up drive mechanism 30, a flange portion 21b is provided at the end of the guide rod 21a of each leaf 21 as a leaf opening means 33 for setting each leaf 21 to an open position (fully open position). An open plate 33a is disposed on the inner side so that the guide rod 21a can be slid therethrough, and a rod 33c of a fluid pressure cylinder 33b for opening driving is connected to the open plate 33a.

  Therefore, as shown in FIG. 1B, the flange portion 21b resists the spring 32a regardless of the position of each leaf 21 by extending the rod 33c of the fluid pressure cylinder 33b of the leaf opening mechanism 33 so as to push it out. And all the leaves 21 can be brought into the open position.

  In the following drive mechanism 30 of the multi-leaf collimator 20 configured as described above, the irradiation field is set by operating and positioning each leaf 21 as follows.

  First, in order to hold each leaf 21 in the open position, the rod 33c of the fluid pressure cylinder 33b of the leaf opening means 33 is extended so as to push it out, and the flange portion 21b resists the spring 32a regardless of the position of each leaf 21. All the leaves 21 are held in the open position.

Next, the member 31 that follows the predetermined position of the case main body 23 of the multi-leaf collimator 20 is set.
Thereafter, the rod 33c of the fluid pressure cylinder 33b of the leaf opening means 33 common to each leaf 21 is contracted to make the leaf 21 free, and pressed against the profile member 31 by the spring 32a of the pressing means 32 of each leaf 21. To do.

  Thereby, the front end surface of each leaf 21 is pressed against the outer side surface 31a of the leveling member 31 to form the irradiation field 22.

  When this profile member 31 is also used as the bolus 41, as shown in FIG. 2B, the outer surface of the bolus 41 functions as the profile member 31, and at the same time, the irradiation depth of the particle beam at the recess 41a. Can be regulated.

  Thereafter, the particle beam is irradiated, and the cancer affected area is irradiated by the irradiation field 22 along the contour shape of the side surface 31a in addition to the profile member 31. When this particle beam is irradiated, irradiation is performed through the follower member 31, so that the irradiation intensity at the irradiation source is set in consideration of the decrease in the follower member 31.

  After the irradiation is completed in this way, the rod 33c of the fluid pressure cylinder 33b of the leaf opening means 33 is extended to push back all the leaves 21 through the opening plate 33a, so that all the leaves 21 are opened. Hold on.

  According to the follower driving mechanism 30 of the multi-leaf collimator 20 as described above, the irradiation field 22 can be formed simply by using the follower member 31 and pressing each leaf 21 against the member 21 by the pressing means 32. The system can be simplified, the position detection is not required, and the control system is simplified.

  In addition, the installation space for the drive mechanism 30 can be reduced, and the cost can be reduced by making the device compact.

  Furthermore, since all the leaves can be opened by one leaf opening means 33, the leaf 21 can be easily set to the fully open position, and the mechanism for this can be simplified.

  Further, by using the profile member 31 also as the bolus 41 for controlling the irradiation depth, the profile member can be manufactured by processing the outer surface simultaneously with the manufacture of the bolus 41, thereby reducing the number of manufacturing steps as much as possible. be able to.

In the follower driving mechanism 30 of the multi-leaf collimator 20 as described above, each leaf 21 needs to be surely pressed against and contacted with the outer surface 31a of the follower member 31.
Therefore, contact detection means 50 for detecting the contact of the leaf 21 with the profile member 31 is provided.

  As the contact detecting means 50, for example, as shown in FIG. 3, a spherical contact 51 is mounted in a recess formed at the tip of each leaf 21 so as to protrude forward by a spring 52, and is attached to the back of the contact 51. An ON-OFF switch 53 is provided.

  Thereby, when the leaf 21 comes into contact with the profile member 31, the contact 51 of the contact detection means 50 is pushed against the spring 52, and the ON-OFF switch 53 is turned ON to detect this.

  Further, as shown in FIG. 4, the contact detecting means 50 is formed such that a similar concave portion is formed at the rear end portion of the leaf 21, and the contact 54 is projected forward by a spring 55 at the tip end portion of the guide rod 21 a of the leaf 21. And an ON-OFF switch 56 is provided on the back of the contact 54. The spring 55 is a weaker spring than the spring 32a of the pressing means 32.

  Thus, the leaf 21 is pushed forward by the spring 32a of the pressing means 32 until the follower member 31 comes into contact with the leaf 21, and when the leaf 21 comes into contact with the follower member 31, the contact 54 of the contact detecting means 50 is moved to the spring. It is pushed against 55, and the ON-OFF switch 56 is turned on to detect this.

  By providing such a contact detection means 50, it is possible to easily detect the contact between the leaf 21 and the member 31 and to detect the position of each leaf 21 easily, In particular, the signal lines can be reduced and the restriction on the transmission distance can be relaxed as compared with the case of detection by an encoder or the like.

  The contact detection means is not limited to the ON / OFF switch, but can be constituted by other pressure sensors, and not only at the front end or the rear end of the leaf but also at both. It may be provided, and the reliability can be further improved.

  In the above embodiment, the description of the configuration such as the arrangement of the leaves 21 is omitted, but the configuration is not limited at all. It is.

1 is a schematic plan view of an irradiation field forming state showing a part of a right leaf, and (b) is a schematic plan view of a leaf in a fully open state according to an embodiment of a multi-leaf collimator of the present invention. It is the longitudinal cross-sectional view of the bolus which shared the tracing member concerning one Embodiment of the multi-leaf collimator of this invention, and explanatory drawing of the use condition. It is one schematic sectional drawing and operation | movement explanatory drawing of the contact detection means concerning other one Embodiment of the multi-leaf collimator of this invention. It is another schematic sectional drawing of the contact detection means concerning other one Embodiment of the multi-leaf collimator of this invention. It is the side view and top view of the conventional leaf collimator. It is explanatory drawing of the drive mechanism of the conventional leaf collimator. It is explanatory drawing of the drive mechanism of the conventional leaf collimator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 Multi-leaf collimator 21 Leaf 21a Guide rod 21b Flange part 22 Irradiation field 23 Case main body 30 Profile drive mechanism 31 Profile member 31a Outer side surface 32 Pressing means 32a Spring 33 Leaf release means 33a Release plate 33b Fluid pressure cylinder 33c Rod 41 Bolus 41a Recessed part 50 Contact detection means 51, 54 Contact 52, 55 Spring 53, 56 ON-OFF switch

Claims (3)

In a multi-leaf collimator that crosses the irradiation direction and opposes each other and adjusts the facing interval of a plurality of leaves to form an irradiation field,
A member capable of transmitting a particle beam having an outer surface formed in the shape of the irradiation field; a pressing means provided on each of the plurality of leaves to press the tip surface of each leaf against the member; and the plurality of leaves A multi-leaf collimator comprising leaf opening means for positioning the whole in a fully open position.   2. The multi-leaf collimator according to claim 1, wherein the profile member is also used as a bolus for regulating the irradiation depth of the particle beam. The multi-leaf collimator according to claim 1 or 2, wherein contact detection means for detecting contact of each leaf with the profile member is provided at a front end portion and / or a rear end portion of each leaf.

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