JP2019141331A - Particle beam irradiation system and irradiation planning device - Google Patents

Abstract

To provide a particle beam irradiation system by a scanning irradiation method, capable of forming a radiation dose distribution as planned, and allowing for shortening of an irradiation time compared to a conventional method.SOLUTION: The particle beam irradiation system comprises: target monitoring devices 35,36 measuring a position of a target 26; and a control system 7. The control system 7 performs: such a tracking irradiation that an exciting current value of scanning electromagnets 31,32 is corrected on the basis of a signal from the target monitoring devices; and such a gate irradiation that depth of the target 26 is calculated on the basis of a signal from the target monitoring devices, and the target 26 is irradiated with charged particle beams when the depth of the target 26 is in a previously set depth permission range. The control system 7 performs the tracking irradiation when the depth of the target 26 measured by the target monitoring devices falls within in a depth permission range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a particle beam irradiation system for irradiating a target with a particle beam such as a proton beam or a carbon beam, and an irradiation planning apparatus for creating an irradiation plan for the particle beam.

  For the purpose of not only reducing the irradiation time and reducing the time load on the irradiation target but also improving the irradiation accuracy, Patent Document 1 discloses an accelerator for emitting a charged particle beam and a charge emitted from the accelerator. In a particle beam irradiation system having an irradiation device that irradiates a particle beam with an irradiation object that is scanned multiple times, the irradiation object is divided in the beam axis direction and corresponds to the size of each scan region Beam intensity modulation means for supplying the irradiation dose by modulating the beam intensity from the accelerator, and each irradiation dose supplied by the charged particle beam modulated by the beam intensity modulation means, the displacement amount of the periodic fluctuation of the irradiation target is And means for scanning each scanning region in a gate period within a predetermined phase.

  Further, Patent Document 2 relates to an apparatus and method for irradiating a patient's ulcer tissue by means of an ion beam, a polarizing device that scans the ion beam in the slice direction and in the plane direction, and the depth direction and depth of the ion beam. An ion beam control device for directional scanning is provided, and an electromagnetically driven ion destruction device is equipped with a depth scanning adaptive device that adapts to the ion beam range, which is faster than the accelerator energy control device. And the movement of the patient is monitored by motion detection means for detecting temporal and positional changes of the ulcer in the processing space, and the controller is adapted to change the temporal and positional changes of the location of the ulcer tissue in the processing space. Depth method to adjust the polarization device, ion beam direction and ion beam range respectively when scanning ulcer tissue Controlling the adaptation device, it has been described.

  Patent Document 3 discloses a charged particle irradiation system and an irradiation planning apparatus that can shorten the irradiation time (treatment time) and form a planned dose distribution in a particle beam irradiation system using a scanning irradiation method. The system corrects the excitation current value of the scanning magnet based on the signal from the moving body tracking device, which is the target monitoring device, and irradiates the irradiation target with the charged particle beam, and the irradiation device based on the signal from the target monitoring device. It is described that gate irradiation for controlling irradiation start and irradiation stop of a charged particle beam to be irradiated is performed.

JP 2008-154627 A JP 2004-504121 A JP 2013-198579 A

  A method of irradiating a patient with cancer or the like with a charged particle beam (particle beam) is known. Such a particle beam irradiation system that irradiates a particle beam generally includes a charged particle generator, a beam transport system, and a treatment room.

  In the particle beam irradiation system using the scanning irradiation method, when the charged particle beam accelerated by the charged particle beam generator reaches the irradiation device in the treatment room through the beam transport system, it is scanned by the scanning electromagnet there, so A dose distribution suitable for the shape of the affected area is formed.

  By the way, when a target such as an affected part moves by breathing or the like, it becomes difficult to form a dose distribution planned in advance. Therefore, as a method of forming a dose distribution as planned, Patent Document 1 discloses a method called gate irradiation. Gate irradiation is a method of irradiating a particle beam when the target is in a predetermined position (exit permission range).

  Patent Document 2 discloses a method called tracking irradiation. The tracking irradiation is a method of changing the position of the charged particle beam in accordance with the movement of the target by changing at least one of the excitation amount of the scanning electromagnet and the thickness of the energy absorber.

  Patent Document 3 discloses a method of combining gate irradiation as described in Patent Document 1 and tracking irradiation as described in Patent Document 2.

  However, in the gate irradiation as described in Patent Document 1, it is necessary to reduce the emission permission range in order to form a dose distribution as planned. As the emission permission range is reduced, there is a problem that the time during which the particle beam can be emitted toward the target becomes shorter and the irradiation time (treatment time) becomes longer.

  Further, in tracking irradiation as described in Patent Document 2, when scanning is performed by changing the excitation amount of the scanning electromagnet, the target moves in the depth direction or the water equivalent thickness up to the target changes. There is a problem that the Bragg peak cannot be formed at the position and the planned dose distribution cannot be formed.

  Further, since the thickness of the energy absorber is changed in accordance with the movement of the affected area, there is a problem that the charged particle beam is scattered by the energy absorber to increase the size of the charged particle beam. As the size of the charged particle beam increases, the penumbra increases and the uniformity of dose distribution deteriorates.

  Further, with the method of combining gate irradiation and tracking irradiation described in Patent Document 3, it is possible to irradiate a planned dose distribution in a short time. However, since the gate range is set in the direction perpendicular to the beam axis in advance, it has been revealed by the present inventors that there is still room for shortening the irradiation time.

  An object of the present invention is to provide a particle beam irradiation system and an irradiation plan capable of forming a dose distribution as planned in a particle beam irradiation system using a scanning irradiation method and reducing the irradiation time as compared with the conventional method. Is to provide a device.

  The present invention includes a plurality of means for solving the above-described problems. For example, the present invention includes an accelerator that generates and emits a charged particle beam, and a scanning electromagnet that scans the charged particle beam. An irradiation device for irradiating the target with the charged particle beam, a target monitoring device for measuring the position of the target, and correcting the excitation current value of the scanning electromagnet based on a signal from the target monitoring device. Tracking the target to irradiate the target, and the target depth is calculated based on a signal from the target monitoring device, and the charged particle beam is calculated when the target depth is within a predetermined depth permission range. A control device that performs gate irradiation, and the control device performs the tracking irradiation when the depth of the target measured by the target monitoring device is within the depth permission range. The features.

  ADVANTAGE OF THE INVENTION According to this invention, in the particle beam irradiation system by a scanning irradiation method, dose distribution as planned can be formed, and irradiation time can be shortened compared with the conventional method. Problems, configurations, and effects other than those described above will be clarified by the following description of examples.

It is a figure which shows the whole schematic structure of the particle beam irradiation system of this invention. It is a block diagram which shows the structure of the irradiation control apparatus with which the particle beam irradiation system of this invention is equipped. It is a figure which shows the dose distribution of the depth direction obtained when a single particle beam is irradiated to irradiation object. It is a figure which shows dose distribution of the depth direction obtained when the irradiation object is irradiated with a plurality of particle beams. It is a figure which shows dose distribution of the horizontal direction obtained when a particle beam is irradiated to irradiation object. It is a conceptual diagram which shows the irradiation parameter memorize | stored in a database. It is the flowchart which showed the procedure which irradiates a particle beam by the particle beam irradiation system of this invention. It is the flowchart which showed a part of procedure which irradiates a particle beam by the particle beam irradiation system of this invention. It is the flowchart which showed a part of procedure which irradiates a particle beam by the conventional particle beam irradiation system.

  Hereinafter, an embodiment of a particle beam irradiation system of the present invention that performs gate irradiation and tracking irradiation by a scanning electromagnet and an irradiation plan apparatus suitable for the system will be described with reference to FIGS.

  First, configurations of the particle beam irradiation system and the irradiation planning apparatus will be described with reference to FIGS. 1 to 5. FIG. 1 is a diagram showing an overall schematic configuration of a particle beam irradiation system. FIG. 2 is a block diagram showing a configuration of an irradiation control device provided in the particle beam irradiation system. FIG. 3A is a diagram showing a dose distribution in the depth direction obtained when a single particle beam is irradiated on the irradiation target, and FIG. 3B is a dose in the depth direction obtained when a plurality of particle beams are irradiated on the irradiation target. FIG. 4 is a diagram showing a dose distribution in the lateral direction obtained when a particle beam is irradiated on an irradiation target. FIG. 5 is a conceptual diagram showing irradiation parameters stored in the database.

  As shown in FIG. 1, the particle beam irradiation system of the present embodiment includes a charged particle beam generator 1, a beam transport system 2, a treatment room 17, a control system 7, and an irradiation planning device 41.

  The charged particle beam generation apparatus 1 is an apparatus that generates and emits a charged particle beam, and includes a linac 3 including an ion source and a previous stage charged particle beam acceleration apparatus, and a synchrotron 4. The synchrotron 4 has a high frequency application device 5 and an acceleration device 6.

  The high-frequency application device 5 includes a high-frequency application electrode 8 and a high-frequency application power source 9 that are arranged in the orbit of the synchrotron 4. The high frequency application electrode 8 and the high frequency application power source 9 are connected by a switch. The acceleration device 6 includes a high-frequency acceleration cavity disposed in the orbit of the particle beam and a high-frequency power source that applies high-frequency power to the high-frequency acceleration cavity. An exit deflector 11 connects the synchrotron 4 and the beam transport system 2.

  The beam transport system 2 includes a beam path 12, a quadrupole electromagnet, and deflection electromagnets 13, 14, 15, and 16. The beam path 12 is connected to an irradiation device 21 installed in the treatment room 17.

  A substantially cylindrical gantry 18 is installed in the treatment room 17.

  The gantry 18 is provided with deflection electromagnets 15 and 16 that are a part of the beam transport system 2, an irradiation device 21 that irradiates a target 26 with a charged particle beam, X-ray generators 35 and 36, and X-ray detectors 37 and 38. Has been. A treatment bed called a couch 24 is installed inside the gantry 18 in order to install the irradiation target 25.

  The gantry 18 has a structure that can be rotated by a motor. The deflection electromagnets 15 and 16, the irradiation device 21, the X-ray generation devices 35 and 36, and the X-ray detectors 37 and 38 rotate with the rotation of the gantry 18. The rotation of the gantry 18 and each device are linked to this movement, so that the irradiation target 25 can be irradiated with the particle beam from any direction within a plane perpendicular to the rotation axis of the gantry 18.

  The irradiation device 21 provided in the gantry 18 includes scanning electromagnets 31 and 32, a position monitor 34, and a dose monitor 33 inside. In the particle beam irradiation system of this embodiment, the irradiation device 21 includes two scanning electromagnets 31 and 32, and deflects the charged particle beam in two directions (X direction and Y direction) in a plane perpendicular to the traveling direction ( The target 26 is irradiated with the charged particle beam by changing the irradiation position.

  The position monitor 34 measures the position of the particle beam and the spread of the particle beam. The dose monitor 33 measures the amount of irradiated particle beam.

  The first X-ray generator 35 and the second X-ray generator 36 are installed in the gantry 18 and generate fluoroscopic X-rays. A flat panel type first X-ray detector 37 and a second X-ray detector 38 are installed at the tip of the irradiation port of the irradiation device 21. The X-ray detector 37 detects an X-ray signal from the X-ray generator 35, and the X-ray detector 38 detects an X-ray signal from the X-ray generator 36.

  There is a target 26 in the irradiation target 25, and a dose distribution that covers the target 26 is formed in the irradiation target 25 by irradiating the particle beam. Here, in the case of treatment of cancer or the like, the irradiation target 25 is a person and the target 26 is a tumor.

  A control system 7 provided in the particle beam irradiation system of the present embodiment will be described with reference to FIG.

  The control system 7 shown in FIG. 1 includes a database 42 as a storage device, a central control device 46, an accelerator control device 47, an irradiation control device 48, and a moving object tracking device 49.

  The X-ray CT apparatus 40 is an apparatus that images the target 26 in the irradiation target 25 and has a function of creating a CT image for each phase of movement when the target 26 moves periodically. In particular, when the irradiation target 25 is a person, a CT image for each respiratory phase of the irradiation target 25 can be acquired.

  The irradiation plan apparatus 41 is an apparatus that creates an irradiation plan for irradiating the target 26 with a charged particle beam based on the CT image for each phase imaged by the X-ray CT apparatus 40. Details thereof will be described later.

  The database 42 is connected to an irradiation planning device 41 connected to the X-ray CT apparatus 40, and records irradiation plan data necessary for irradiation created by the irradiation planning device 41.

  The central controller 46 is connected to an accelerator controller 47, an irradiation controller 48, and a moving body tracking device 49. The central controller 46 is connected to the database 42. The central controller 46 receives data from the database 42 and controls the operation by transmitting necessary information to the accelerator controller 47, the irradiation controller 48, and the moving body tracking device 49.

  The accelerator controller 47 is connected to the charged particle beam generator 1, the beam transport system 2, and the gantry 18, and controls them.

  The irradiation controller 48 controls the scanning electromagnet power supply 48 a that excites the scanning electromagnets 31 and 32 and processes signals from the monitors in the irradiation device 21. The detailed configuration will be described later.

  The moving body tracking device 49 is connected to the X-ray generators 35 and 36 and the X-ray detectors 37 and 38, and controls these operations.

  In the present embodiment, the target monitoring device that measures the position of the target 26 includes X-ray generation devices 35 and 36, X-ray detectors 37 and 38, and a moving body tracking device 49.

  The irradiation control device 48 of the control system 7 of the present embodiment corrects the excitation current value of the scanning electromagnets 31 and 32 based on the signal from the target monitoring device, and irradiates the target 26 with the charged particle beam, and target monitoring. Based on the signal from the apparatus, the depth of the target 26 is calculated, and when the depth of the target 26 is within a predetermined depth permission range, control necessary for performing irradiation with a gate that irradiates a charged particle beam is executed. To do. In this embodiment, the irradiation control device 48 performs the operation of each device in the system so as to perform the tracking irradiation when it is determined that the depth of the target 26 measured by the target monitoring device is within the depth permission range. Control. Details of the irradiation control device 48 will be described below with reference to FIG.

  As shown in FIG. 2, the irradiation control device 48 is connected to a position monitor 34 and a dose monitor 33 in the irradiation device, and controls these operations. Moreover, it is connected with the moving body tracking device 49 and the accelerator control device 47, and communicates with these devices.

  The irradiation controller 48 includes a scanning electromagnet power supply 48a for exciting the scanning electromagnets 31 and 32, a depth table memory 48b, a depth permission range memory 48c, a position memory 48f, a dose memory 48h, a coordinate processing circuit 48d, an irradiation control circuit 48g, And a position monitoring circuit 48e.

  The scanning electromagnet power supply 48a includes an additional current memory 48a2, an excitation current memory 48a3, and an electromagnet control circuit 48a1.

  3A and 3B, the relationship between the depth of the target 26 and the energy of the particle beam when the surface of the irradiation target 25 in the particle beam irradiation system according to this embodiment is used as a reference will be described. 3A and 3B are diagrams in which the horizontal axis indicates the depth of the target 26 and the vertical axis indicates the dose of the particle beam.

  FIG. 3A shows the dose distribution that a single energy particle beam forms in an irradiation object as a function of depth. The peak in FIG. 3A is called a Bragg peak. The position of the Bragg peak depends on the energy of the particle beam. Therefore, the position of the Bragg peak can be adjusted by adjusting the energy of the particle beam, and the particle beam of an appropriate dose can be irradiated to the desired depth of the target 26.

  The target 26 has a thickness in the depth direction, but the Bragg peak is a sharp peak. Therefore, by irradiating several energy particle beams at an appropriate intensity ratio and superimposing the Bragg peaks, as shown in FIG. 3B, a uniform height having the same thickness as the target 26 in the depth direction is obtained. A dose region (SOBP) is formed.

  With reference to FIG. 4, the relationship between the lateral extent of the target 26 in the direction perpendicular to the beam axis (the direction of the XY plane) and the particle beam will be described. In FIG. 4, the horizontal axis indicates the lateral extent of the target 26, and the vertical axis indicates the dose at the irradiation spot. The direction perpendicular to the beam axis is called the transverse direction.

  After reaching the irradiation device 21, the particle beam is scanned by the two scanning electromagnets 31 and 32 that are vertically arranged to reach a desired position in the lateral direction. The lateral spread of the particle beam can be approximated by a Gaussian distribution shape. Therefore, by arranging Gaussian distributions at equal intervals and setting the distance therebetween to about the standard deviation of the Gaussian distribution, the added distribution has a uniform region as shown in FIG. The Gaussian distribution dose distribution arranged in this way is called a spot. By scanning the particle beam and arranging a plurality of spots at equal intervals, a uniform dose distribution in the lateral direction as shown in FIG. 4 can be formed.

  As described above, a uniform irradiation field can be formed by the beam scanning in the horizontal direction by the scanning electromagnets 31 and 32 and the movement of the Bragg peak in the depth direction by changing the beam energy. The unit of the irradiation field that is irradiated with the same energy and spreads in the horizontal direction by scanning the particle beam by the scanning electromagnets 31 and 32 is called a slice.

  Returning to FIG. 1, the irradiation planning device 41 determines irradiation parameters, a depth table, a depth permission range, a gantry angle, and irradiation target position information necessary for irradiation before irradiating the target 26 with the particle beam. FIG. 5 shows the structure of irradiation parameters.

  As shown in FIG. 5, the irradiation parameter determined by the irradiation planning device 41 is composed of the slice number N and N slice data. A slice represents a set of spots irradiated with the same energy. The slice data includes slice number i, energy Ei, spot number Ni, and Ni spot data. The spot data includes a spot number j, an irradiation position (Xij, Yij), and a target irradiation amount Dij. These irradiation parameters are determined by the procedure as follows, for example.

  Before planning, the irradiation object 25 is imaged in advance by the X-ray CT apparatus 40, and a CT image of the irradiation object 25 for n phases is created. The X-ray CT apparatus 40 transmits the created CT image to the irradiation planning apparatus 41.

  The irradiation planning device 41 displays the received image data on the screen of a display device (not shown). The operator selects a CT image having a reference phase from the CT images for each phase. For example, when considering the movement of the target 26 due to respiration, the expiration phase is selected.

  The operator designates a region to be irradiated so as to cover the target 26 on the selected CT image and a region (important organ) that is desired to suppress the irradiation of the particle beam as much as possible. The irradiation planning device 41 determines and determines the installation position, gantry angle, and irradiation parameters of the irradiation object 25 that can form a dose distribution in the designated area.

  That is, the irradiation planning apparatus 41 determines the irradiation target installation position and the gantry angle based on the irradiation target information input by the operator, and then divides the target 26 (affected site) into a plurality of slices in the depth direction, and the necessary slices. The number N is determined.

  When the irradiation target 25 is installed at the irradiation target installation position, the irradiation planning device 41 calculates an image projected on the X-ray detectors 37 and 38 and uses it as irradiation target position information. Moreover, the irradiation plan apparatus 41 calculates | requires the energy Ei of the ion beam suitable for irradiation according to the depth of each slice (slice number i).

  The irradiation planning device 41 further determines the number of irradiation spots Ni, the spot number j, the irradiation position (Xij, Yij) of each spot, and the target irradiation amount Dij of each spot according to the shape of each slice. To do.

  The irradiation plan apparatus 41 calculates | requires the dose distribution when the irradiation object 25 is irradiated with each determined value, and displays the calculated | required dose distribution on a display apparatus.

  Next, the irradiation plan apparatus 41 calculates | requires the depth table in which the depth permission range which is the conditions which perform tracking irradiation used when tracking irradiation and gate irradiation are performed, and the depth information of the target 26 were recorded.

  On the path of the spot formed by the spot of spot number j of slice number i, the water equivalent thickness from the body surface to the shallow boundary of the target 26 is defined as Wij. The depth permission range is registered for each spot and is set to Wij ± δ. Here, δ is a constant, but may be a common value for all spots, or a different value may be used for each slice.

  The depth table is determined using CT images of all phases. First, the position of the target 26 on the CT image is specified for each phase. Next, the difference from the target position at the reference phase is calculated for each phase. An amount obtained by projecting this difference in consideration of the irradiation direction of the particle beam is a correction amount for water equivalent thickness calculation tracked by the scanning electromagnets 31 and 32. By adding this correction amount for water equivalent thickness calculation to the irradiation position of each spot, the water equivalent thickness from the body surface on the spot path to the shallow boundary of the target 26 is obtained.

  By calculating this calculation for all combinations of spots and phases, a table for each spot is obtained. That is, if the phase number is k, the water equivalent thickness from the body surface on the spot path at the phase k to the shallow boundary of the target 26 is the depth for the spot of the spot number j of the slice number i. The table is Wijk.

  The data of the depth table Wijk created in this way is created for the number of gantry angles.

  Furthermore, the data of the depth table Wijk created by the number of gantry angles includes information on whether or not an important organ exists on the path.

  The created irradiation parameters, gantry angle, irradiation target position information, depth permission range, and depth table Wijk are transmitted to the database 42 and recorded in the database 42.

<Irradiation procedure>
A procedure for forming a dose distribution on the irradiation target 25 using the irradiation parameters, depth permission range, depth table Wijk, irradiation target installation information and gantry angle created by the above procedure will be described below with reference to FIGS. explain. FIG. 6 is a flowchart showing a procedure of irradiating the particle beam by the particle beam irradiation system. FIG. 7 is a flowchart showing the details of a part of the procedure for irradiating the particle beam shown in FIG. 6, and FIG. 8 is a flowchart showing the details of a part of the procedure for irradiating the particle beam by the conventional particle beam irradiation system. .

  When the operator presses the irradiation preparation start button on the console connected to the central control unit 46, the central control unit 46 sets the installation position of the irradiation target 25, the gantry angle depth allowable range, the depth table Wijk, and the irradiation from the database 42. Receive parameters.

  The central controller 46 transmits energy information and a gantry angle described in the irradiation parameters to the accelerator controller 47, and transmits a depth permission range, a depth table, and irradiation parameters to the irradiation controller 48.

  The accelerator controller 47 prepares excitation patterns for the scanning electromagnets 31 and 32 for emitting a charged particle beam having energy designated by the central controller 46.

  In the irradiation control device 48, the depth permission range, the depth table Wijk, and the irradiation parameter received from the central control device 46 are set in each memory. More specifically, the irradiation position is recorded in the position memory 48f, the target irradiation amount is recorded in the dose memory 48h, the depth permission range is recorded in the depth permission range memory 48c, and the depth table is recorded in the depth table memory 48b. Further, the excitation current values of the scanning electromagnets 31 and 32 obtained from the irradiation position and energy are recorded in the excitation current memory 48a3 of the scanning electromagnet power supply 48a.

  The irradiation object 25 is placed on the couch 24 and fixed.

  After the irradiation object 25 is fixed, the target 26 in the irradiation object 25 is seen through using the X-ray generators 35 and 36 and the X-ray detectors 37 and 38 in order to confirm that the irradiation object 25 is installed at the planned position. . The fluoroscopic image and the image of the irradiation target position information are compared, and a deviation amount from the planned position is calculated. According to the deviation amount, the couch 24 is moved to adjust the position of the irradiation object 25.

  After adjusting the position of the irradiation object 25 with respect to the couch 24, the angle of the gantry 18 is set. When the operator presses the gantry rotation button on the console connected to the central controller 46, the accelerator controller 47 rotates the gantry 18 to the gantry angle described in the irradiation parameters.

  After the rotation of the gantry 18 is completed, the operator presses an irradiation start button on the console. When the irradiation start button is pressed, irradiation is started according to the procedure shown in FIG.

  As shown in FIG. 6, first, irradiation is started from a spot with energy number i = 1 and spot number j = 1 (step S201). The moving body tracking device 49 controls the X-ray generators 35 and 36 and the X-ray detectors 37 and 38 to start measuring the position of the target 26. The accelerator controller 47 controls the charged particle beam generator 1 to accelerate the particle beam to energy E1 with energy number i = 1.

  The moving body tracking device 49 controls the X-ray generators 35 and 36 to generate X-rays at a constant interval (for example, 30 Hz). The moving body tracking device 49 calculates the position (target coordinates) of the target 26 using the images acquired from the X-ray detectors 37 and 38, and transmits the target coordinates to the coordinate processing circuit 48d.

  In order to make it easier to specify the position of the target 26, a marker such as a metal sphere is inserted in advance in the vicinity of the target 26, and instead of measuring the position of the target 26, the position of the marker may be measured. Good. Since the marker is easily reflected in the fluoroscopic image, the position of the target 26 can be measured with high accuracy. In addition, when measuring the position of the target 26 directly without a marker, the effect that the effort which inserts a marker can be saved is acquired.

  Next, an acceleration signal is transmitted from the central controller 46 to the accelerator controller 47. The accelerator controller 47 accelerates the particle beam by controlling the ion source, linac 3 and synchrotron 4 (step S202). The particle beam generated in the ion source is accelerated by the linac 3 and is incident on the synchrotron 4. The incident particle beam is accelerated to the energy E1 for applying the high frequency from the acceleration device 6 and irradiating the first slice number. When the acceleration of the particle beam is completed, an acceleration completion signal is transmitted from the accelerator controller 47 to the irradiation controller 48.

  Next, the irradiation control device 48 that has received the acceleration completion signal prepares for spot irradiation (step S203). Details of the processing in step S203 will be described with reference to FIG.

  When the irradiation control circuit 48g in the irradiation control device 48 receives the acceleration completion signal, the irradiation control circuit 48g transmits a spot setting signal to the coordinate processing circuit 48d, the position monitoring circuit 48e, and the electromagnet control circuit 48a1.

  When the coordinate processing circuit 48d receives the spot setting signal, the coordinate processing circuit 48d reads the depth permission range and the depth table Wijk of the spot of i = 1, j = 1 from the depth permission range memory 48c and the depth table memory 48b (step S203A2). ). As a premise, the coordinate processing circuit 48d receives the target coordinates from the moving body tracking device 49 at a constant cycle (step S203A1), and uses the Wijk for the phase k with the closest received target coordinates as the depth of the target 26. refer.

  Then, it is determined whether or not the referenced Wijk is within the depth permission range Wij ± δ (step S203A3). When it is determined that it is within the permitted range, the process proceeds to step S203A4, and the irradiation control circuit 48g determines whether or not an important organ is present on the particle beam passage route from the body surface to the target 26 ( Step S203A4). When it is determined that there is no important organ, the emission permission signal is continuously transmitted to the irradiation control circuit 48g until the depth goes out of the depth permission range.

  On the other hand, when it is not determined in step S203A3 that it is within the permitted range or when it is determined in step S203A4 that an important organ is present, the process returns to step S203A1.

  The coordinate processing circuit 48d transmits the latest target coordinates to the position monitoring circuit 48e. Further, the coordinate processing circuit 48d calculates an additional current value from the latest target coordinates and the irradiation energy, and records the calculated additional current value in the additional current memory 48a2 of the scanning electromagnet power supply 48a.

  The position monitoring circuit 48e receives the target coordinates from the coordinate processing circuit 48d and records them as the target coordinates of the spot where i = 1 and j = 1.

  The electromagnet control circuit 48a1 calculates the sum of the additional current value recorded in the additional current memory 48a2 and the exciting current value corresponding to the spot of i = 1 and j = 1 recorded in the exciting current memory 48a3. Is the excitation current value. The electromagnet control circuit 48a1 excites the scanning electromagnets 31 and 32 with an excitation current value obtained by controlling the scanning electromagnet power supply 48a. When the setting of the current value of the scanning electromagnet power supply 48a is completed, the electromagnet control circuit 48a1 transmits an electromagnet setting completion signal to the irradiation control circuit 48g of the irradiation controller 48. These current values are set for both the scanning electromagnet 32 corresponding to the X axis and the scanning electromagnet 31 corresponding to the Y axis.

  The irradiation control circuit 48g transmits an extraction start signal to the accelerator control device if the extraction permission signal is still received when the electromagnet setting completion signal is received (step S203A5). On the other hand, if the irradiation control circuit 48g has not received the extraction permission signal when receiving the electromagnet setting completion signal, the irradiation control circuit 48g waits to receive the extraction permission signal again. A spot reset signal is transmitted to the position monitoring circuit 48e and the electromagnet control circuit 48a1.

  Upon receiving the spot reset signal, the coordinate processing circuit 48d transmits the latest target coordinates to the position monitoring circuit 48e, and transmits an additional current value corresponding to the latest coordinates to the additional current memory 48a2 of the scanning electromagnet power supply 48a.

  When the position monitoring circuit 48e receives the spot reset signal, the position monitoring circuit 48e re-records the target coordinates received from the coordinate processing circuit 48d as target coordinates of i = 1 and j = 1.

  When the electromagnet control circuit 48a1 receives the spot reset signal, the electromagnet control circuit 48a1 sets the sum of the latest additional current value overwritten by the coordinate processing circuit 48d and the excitation current value of i = 1, j = 1 in the scanning electromagnet. When the setting is completed, the electromagnet control circuit 48a1 transmits an electromagnet setting completion signal to the irradiation control circuit 48g.

  The irradiation control circuit 48g repeats the same operation until it receives the emission permission signal when it receives the electromagnet setting completion signal.

  The irradiation control circuit 48g receives the emission permission signal when it receives the electromagnet setting completion signal, and when it is determined that there is no important organ on the path of the particle beam from the body surface to the target 26, the accelerator controller 47 An emission start signal is transmitted to.

  Next, the accelerator control device 47 that has received the emission start signal controls the high frequency application device 5 to apply a high frequency to the particle beam. The particle beam to which the high frequency is applied passes through the output deflector 11, passes through the beam path 12, and reaches the irradiation device 21 in the treatment room 17. The particle beam is scanned by the scanning electromagnets 31 and 32 in the irradiation device 21, passes through the position monitor 34 and the dose monitor 33, reaches the irradiation target 25, and gives a dose to the target 26 (step S204).

  The amount of the particle beam that has reached the target 26 is detected by the dose monitor 33 and counted by the irradiation control circuit 48g. The irradiation control circuit 48g compares the count of the signal from the dose monitor 33 with the value of the dose memory 48h. When the count reaches the target dose recorded in the dose memory 48h, an irradiation stop signal is sent to the accelerator controller 47. Output.

  The accelerator control device 47 that has received the emission stop signal controls the high frequency application device 5 to stop the application of the high frequency and stop the extraction. The irradiation control circuit 48g transmits a spot completion signal to the position monitoring circuit 48e. The position monitoring circuit 48e adds the target coordinates received from the coordinate processing circuit 48d and the value of the irradiation position recorded in the position memory 48f, calculates the difference between the position detected by the position monitor 34, and the difference is less than the threshold value. Make sure that

  Next, it is determined whether or not there is a spot for which irradiation has not been completed among spots existing in the same slice (step S205). If it is determined that there is an incomplete spot, that is, if the spot number j is j <Ni, the process returns to step S203 to irradiate the j + 1-th spot. On the other hand, if it is determined that all spots of the same slice have been irradiated, that is, if j = Ni, the process proceeds to step S206.

  Next, a deceleration signal is transmitted from the central controller 46 to the accelerator controller 47 (step S206). The accelerator control device 47 that has received the deceleration signal decelerates the particle beam, and enters a state where a new particle beam can enter from the linac 3.

  Next, it is determined whether there is a layer for which irradiation has not been completed (step S207). If it is determined in this step that there is an incomplete layer, that is, if i <N, the process returns to step S202 to irradiate the i + 1th layer. On the other hand, if it is determined that the irradiation of all layers is completed, that is, if i = N, the process proceeds to step S208, and the irradiation is completed.

  Here, for comparison, details of the steps in the above-described Patent Document 3 corresponding to step S203 shown in FIG. 6 will be described with reference to FIG.

  As shown in FIG. 8, in the prior art, the coordinate processing circuit receives the target coordinates from the moving body tracking device at a constant cycle (step S203P1), and the latest received target coordinates are within the emission permission range. (Step S203P2), when it is determined that it is within the permitted range, the process proceeds to step S204P that executes spot irradiation, and when it is not determined that it is within the permitted range, the process is performed. It returns to S203P1.

  In such a conventional technique, a rectangular parallelepiped emission permission range is determined when an irradiation plan is created. Then, whether or not the tracking irradiation is executed is determined based on whether or not the coordinates of the target acquired in parallel with the irradiation are within a predetermined emission permission range.

  However, the target depth does not always change from the time of the irradiation plan creation until the actual irradiation. For this reason, in the technique described in Patent Document 3, in addition to the problem that there is room for shortening the irradiation time for setting the gate range in the vertical direction as described above, the position of the target measured at the time of irradiation Even within the permitted emission range, the depth of the irradiation position is not limited to the high accuracy as planned, and there is room for further improvement in irradiation accuracy for the first time by the present inventors' investigation. It became clear. In such a conventional technique, as long as it is determined whether or not to perform tracking irradiation based on whether or not the target coordinates are within a predetermined extraction permission range, in order to keep irradiation accuracy high, It became clear for the first time that it was necessary to narrow the depth direction and there was room for further shortening of treatment time.

  On the other hand, when performing gate irradiation based on whether or not the depth information of the target 26 acquired at the time of irradiation is within the depth permission range, as in the present embodiment shown in FIG. Even if the depth of the target 26 is changed before the irradiation, the tracking irradiation is performed when it is determined that the depth of the target 26 acquired in parallel with the irradiation is equivalent to a predetermined depth permission range. Therefore, the irradiation accuracy can be kept high and the depth allowable range can be widened. For this reason, it is possible to secure a long irradiation time and to shorten the treatment time.

  By the irradiation performed according to the above procedure, a dose distribution as planned can be formed in a short time.

  Next, the effect of the present embodiment will be described.

  The particle beam irradiation system of the present embodiment described above includes the charged particle beam generator 1 that generates and emits a charged particle beam, and scanning electromagnets 31 and 32 that scan the charged particle beam. A target monitoring device including an irradiation device 21 that irradiates the target 26, X-ray generation devices 35 and 36, X-ray detectors 37 and 38 that measure the position of the target 26, and a moving body tracking device 49, and a signal from the target monitoring device The depth of the target 26 is calculated by correcting the excitation current value of the scanning electromagnets 31 and 32 based on the above and calculating the depth of the target 26 based on the tracking irradiation that irradiates the target 26 with the charged particle beam and the signal from the target monitoring device. , And a control system 7 that performs gate irradiation for irradiating a charged particle beam when the value is within a predetermined depth permission range. The control system 7 controls the target 26 measured by the target monitoring device. And it performs tracking irradiation when is in the depth permitted range of.

  Moreover, the irradiation plan apparatus 41 which produces the irradiation plan for irradiating the target 26 with a charged particle beam of a present Example scans a charged particle beam based on the signal from the target monitoring apparatus which measures the position of the target 26. The depth of the target 26 is calculated based on the tracking irradiation for irradiating the target 26 with the charged particle beam by correcting the excitation current values of the electromagnets 31 and 32 and the signal from the target monitoring device. A depth table in which the depth information of the target 26 is recorded is used in advance when performing gate irradiation for irradiating a charged particle beam when the depth is within the allowable depth range.

  In this way, for the movement of the target 26 in the direction perpendicular to the beam axis, the amount of excitation of the scanning electromagnets 31 and 32 can be corrected to irradiate the target 26 with the particle beam as planned. When the depth of the target 26 differs from the planned depth by a certain level or more, the particle beam can be irradiated to the target depth as planned by stopping the irradiation of the particle beam. Therefore, in the particle beam irradiation system based on the scanning irradiation method, the time during which the particle beam can be irradiated can be lengthened compared to the conventional case, and the irradiation time (treatment time) can be shortened.

  Moreover, as described above, the depth of the target 26 is not necessarily changed between the time when the irradiation plan is created and before the actual irradiation, but the depth of the target 26 acquired at the time of irradiation as in this embodiment. By performing gate irradiation depending on whether the information is within the depth permission range, it is possible to keep irradiation accuracy high after ensuring a long irradiation time, and it is possible to shorten the treatment time. Also has the effect.

  Further, since the depth is the water equivalent thickness from the body surface of the irradiation target 25 having the target 26 to the target 26, even when the range of the particle beam changes due to the change of the water equivalent thickness to the target 26. Since the tracking irradiation is executed under the condition (timing) in which the water equivalent thickness is equal, the dose distribution as planned can be formed in a short time, and the treatment can be completed in a shorter time.

  Further, the control system 7 does not perform the tracking irradiation even when the depth of the target 26 is within the depth allowable range when the important organ is on the path of the charged particle beam. Since it is possible to suppress the irradiation of the particle beam to the organ, it is possible to suppress the itch that causes an undesirable event to the important organ due to the irradiation of the particle beam.

<Others>
In addition, this invention is not restricted to said Example, A various deformation | transformation and application are possible. The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.

  For example, although the method of measuring the position of the target 26 during irradiation has been described, the positional relationship between the position of the target 26 and the surface of the irradiation target 25 is obtained in advance, and the target 26 is based on the signal on the surface of the irradiation target 25. It is possible to determine the depth of the gate and perform gate control and tracking control. For the body surface position, it is desirable to use a monitoring monitor different from the target monitoring device, for example, a measuring device capable of measuring the movement of the body surface position, such as a laser distance meter or a stereo camera. Also in this case, as in the above-described embodiment, the emission permission signal is output when the depth of the target 26 measured in real time is within the depth permission range.

  The method for specifying the position of the target 26 is not limited to X-rays, and electromagnetic waves and ultrasonic waves can be used.

  In the above-described embodiment, a method of creating a depth table in advance before treatment has been described. However, the depth of the target 26 uses a value measured in real time using other information such as a body surface position. Is possible. Also in this case, the emission permission signal is output when the depth of the target 26 measured in real time is within the depth permission range.

  In the above-described embodiment, the water equivalent thickness from the body surface of the irradiation target 25 to the target 26 is used as the depth, but an index other than the water equivalent thickness can be used. For example, when the periphery of the target 26 can be approximated as water, the distance from the body surface of the irradiation target 25 to the target 26 can be used instead of the water equivalent thickness.

  In the above-described embodiment, only the depth of the target 26 is described as a reference for gate irradiation. However, the absolute position of the target 26, the distance from the body surface of the irradiation target 25 to the target 26, the body surface of the irradiation target 25 At least one of the water equivalent thicknesses from the target 26 to the target 26 can be used alone or in combination to determine whether irradiation is possible.

  As described above, at least one of the depth, the water equivalent thickness from the body surface of the irradiation target 25 to the target 26, or the distance from the body surface of the irradiation target 25 to the target 26 is the gate irradiation condition. By performing the tracking irradiation when it is within the permitted range, the irradiation time of the particle beam with respect to the target 26 can be secured longer, and the treatment time can be further shortened.

  In addition, by using a monitoring monitor different from the target monitoring device for monitoring the position of the irradiation target 25 on the body surface, the depth information acquisition method of the target 26 can be increased, and the depth determination accuracy is improved. And redundancy can be ensured.

  In the above-described embodiment, the depth of the target 26 is from the body surface of the irradiation target 25 to the boundary on the shallow side of the target 26. However, the boundary on the deep side of the target 26 or an arbitrary point inside the target 26 is used. Can be any distance up to.

  In the above embodiment, the coordinate processing circuit 48d transmits new information for each spot. This is because the time for irradiating one spot is as short as several ms, and the distance that the target 26 moves during that time can be substantially ignored. However, the excitation current value can be changed in accordance with the position of the target 26 by updating the additional current memory 48a2 while irradiating one spot. When the irradiation time of one spot is long, it is effective to change the excitation current value even during spot irradiation.

  Further, in the above-described embodiment, the coordinate processing circuit 48d controls the emission permission timing and the additional current value based on the coordinates of the target 26 received from the moving body tracking device 49. However, the coordinate processing circuit 48d can predict the position of the target 26 using the coordinates of the target 26 received from the moving body tracking device 49. By predicting the position, it is possible to avoid the delay of the emission permission timing and the additional current value due to the processing time of the control system 7. Further, by predicting, the emission permission timing and the additional current value can be controlled in a cycle shorter than the X-ray imaging cycle, and the irradiation time can be further shortened.

  Further, in the above-described embodiment, a method of scanning the scanning electromagnets 31 and 32 after entering the emission permission state is described. However, the scanning electromagnet power supply 48a can update the excitation amount at a constant cycle regardless of the emission permission state. In this case, it is desirable that the coordinate processing circuit 48d updates the additional current memory 48a2 at a cycle equivalent to the cycle for updating the excitation amount. This cycle can be equivalent to the cycle in which the coordinate information is sent from the moving object tracking device 49. Further, this cycle can be made shorter than the cycle in which the coordinate information is transmitted from the moving body tracking device 49 by using the coordinates predicted based on the coordinate information transmitted from the moving body tracking device 49.

  Thus, even when it is not in the emission permission state, the additional current value is transmitted to the scanning electromagnet power supply 48a, and scanning is always performed in accordance with the movement of the target 26, until the particle beam is emitted after the emission permission signal is transmitted. Can be shortened.

  In the above-described embodiment, the spot scanning for stopping the emission of the particle beam for each spot has been described as an example. However, the present invention can also be applied to the raster scanning and the line scanning that do not stop the emission of the particle beam.

  In the above-described embodiment, the gantry 18 that rotates 360 degrees has been described as an example. However, the present invention can be similarly applied to a particle beam irradiation apparatus that does not have a gantry that rotates 180 degrees. it can.

  Moreover, although the case where the accelerator of the charged particle beam generator 1 is a synchrotron has been described as an example, various accelerators of a cyclotron type or a synchrocyclotron type can be used as the accelerator. For example, in the case of a cyclotron, the emission indicates that the beam is emitted from the cyclotron toward the transport system.

1 ... charged particle beam generator (accelerator)
7. Control system (control device)
17 ... treatment room 21 ... irradiation device 25 ... irradiation object 26 ... target 31, 32 ... scanning electromagnet 35, 36 ... X-ray generator (target monitoring device)
37, 38 ... X-ray detector (target monitoring device)
40 ... X-ray CT apparatus 41 ... Irradiation planning apparatus 42 ... Database 46 ... Central controller 47 ... Accelerator controller 48 ... Irradiation controller 48a ... Scanning magnet power supply 48a1 ... Electromagnet control circuit 48a2 ... Additional current memory 48a3 ... Excitation current memory 48b Depth table memory 48c Depth permission range memory 48d Coordinate processing circuit 48e Position monitoring circuit 48f Position memory 48g Irradiation control circuit 48h Dose memory 49 Moving object tracking device (target monitoring device)

Claims (7)

An accelerator that generates and emits a charged particle beam;
An irradiation device having a scanning electromagnet for scanning the charged particle beam, and irradiating the target with the charged particle beam;
A target monitoring device for measuring the position of the target;
Tracking irradiation for irradiating the target with the charged particle beam by correcting the excitation current value of the scanning electromagnet based on the signal from the target monitoring device, and calculating the depth of the target based on the signal from the target monitoring device And a control device that performs gate irradiation for irradiating the charged particle beam when the depth of the target is within a predetermined depth permission range, and
The particle beam irradiation system, wherein the control device performs the tracking irradiation when the depth of the target measured by the target monitoring device is within the depth permission range. The particle beam irradiation system according to claim 1,
The depth is either a water equivalent thickness from the irradiation target surface having the target to the target or a distance from the irradiation target surface to the target. The particle beam irradiation system according to claim 1,
As for the gate irradiation, at least one of the depth, the water equivalent thickness from the irradiation target surface having the target to the target, or the distance from the irradiation target surface to the target is within each permitted range. The tracking irradiation is performed when the particle beam irradiation system. In the particle beam irradiation system according to claim 2 or 3,
The particle beam irradiation system characterized by using a monitoring monitor different from the target monitoring apparatus for monitoring the position of the irradiation target surface. The particle beam irradiation system according to claim 1,
A particle beam irradiation system, further comprising: an irradiation planning device that previously creates a depth table in which the depth information of the target is recorded. The particle beam irradiation system according to claim 1,
The control device does not perform the tracking irradiation even when the depth of the target is within the depth permission range when an important organ is present on the passage path of the charged particle beam. The particle beam irradiation system. An irradiation planning device for creating an irradiation plan for irradiating a target with a charged particle beam,
Tracking irradiation for irradiating the target with the charged particle beam by correcting an excitation current value of a scanning magnet that scans the charged particle beam based on a signal from a target monitoring device that measures the position of the target, and the target monitoring device The depth of the target is used when performing gate irradiation for irradiating the charged particle beam when the depth of the target is calculated based on a signal from the target and the depth of the target is within a predetermined depth permission range. An irradiation planning apparatus, wherein a depth table in which depth information is recorded is created in advance.

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