JP2017086169A - Particle beam irradiation apparatus, particle beam determination method, and particle beam determination program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle beam irradiation apparatus, a particle beam determination method, and a particle beam determination program capable of displaying a beam position in real time while irradiation is progressing.SOLUTION: A particle beam irradiation apparatus includes a beam generation part 11 for generating a particle beam, an emission control part 12 for controlling the emission of the particle beam, a beam scanning part 13 for two-dimensionally scanning the particle beam, a position monitor 18 in which a plurality of first linear electrodes are placed in parallel in a first direction and a plurality of second linear electrodes are placed in parallel in a second direction orthogonal to the first direction, a center-of-gravity calculation part 34 for calculating a center-of-gravity position of the particle beam from first signals output from the first linear electrodes and second signals output from the second linear electrodes, a position information output part 29 for outputting the center-of-gravity position over the range of the two-dimensional scanning, and a display part 31 connected to the position information output part 29 for displaying a trajectory of the center-of-gravity position output from the position information output part 29 as a two-dimensional distribution of the particle beam position.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a particle beam irradiation technique for irradiating an irradiation object with a heavy particle such as carbon or a particle beam such as proton.

In recent years, in particle beam therapy used for cancer treatment, development of a three-dimensional scanning irradiation method in which an affected area in a body is irradiated in a three-dimensional lattice pattern has been promoted.
Since this irradiation method can irradiate with high accuracy according to the three-dimensional shape of the affected part, exposure to normal cells can be suppressed as compared with the conventional two-dimensional irradiation method.
In the three-dimensional scanning irradiation method, first, a so-called treatment plan is performed in which a dose of a particle beam (hereinafter simply referred to as “beam”) irradiated to each lattice is determined in advance.
Then, the affected area is treated by actually irradiating the affected area with the beam according to the planned dose determined in this treatment plan.

The three-dimensional scanning irradiation method is roughly classified into a spot scanning method and a raster scanning method.
In both the spot scanning method and the raster scanning method, the beam stops at the spot until the planned dose is reached for each spot (grid point).
The beam then moves to the next spot in response to a spot switching command notifying that the planned dose has been reached.

This stopping and spot movement are sequentially repeated to complete irradiation of all the spots that need irradiation in one slice.
When irradiation of one slice is completed, the emission of the beam is temporarily stopped, and the slice is changed by changing the range of the beam.
In this way, scanning irradiation and slice change are repeated to perform irradiation over the entire three-dimensional treatment site.

A particle beam beam irradiation apparatus used for beam irradiation is provided with a position monitor that reads position coordinates of the beam passing on a coordinate plane provided perpendicular to the traveling direction of the beam.
Using this position monitor, it is determined whether or not the position coordinates of the measured beam spot are at the position specified in the treatment plan.
When the deviation of the beam spot exceeds the allowable range, an interlock signal is transmitted to the particle beam irradiation apparatus, and irradiation is temporarily stopped.

In addition, when irradiation of one slice is completed, a so-called dose profile is displayed on the display unit, in which the distribution of the beam dose irradiated to this slice is superimposed on the slice image.
By displaying the dose profile, an operator such as a doctor or a technician can confirm whether or not the irradiation to the slice was actually performed as planned.

JP 2001-33560 A JP 2011-161056 A

However, in the above-described conventional method, there is a problem that an operator such as a doctor cannot visually recognize the beam irradiation in progress.
The conventional position monitor is used for determining the transmission of an interlock signal that controls the emission of the beam, and does not have a function of allowing the operator to visually recognize the irradiation state.

Since the dose profile is displayed for each slice, it is not possible to confirm the state of the beam during irradiation depending on the display of the dose profile.
Therefore, even if the beam does not irradiate and move the spot according to the treatment plan, the operator cannot immediately grasp the abnormal situation.
That is, for example, when an abnormality occurs in the current setting of the scanning electromagnet power source, it is difficult for the operator to immediately grasp the abnormality.

  The present invention has been made in consideration of such circumstances, and a particle beam irradiation apparatus, a particle beam beam confirmation method, and a particle beam beam confirmation program capable of displaying a beam position in real time while irradiation is in progress. The purpose is to provide.

  An irradiation apparatus according to the present embodiment includes a beam generation unit that generates a particle beam, an emission control unit that controls emission of the particle beam, a beam scanning unit that two-dimensionally scans the particle beam, and a plurality of first units. A position monitor in which a plurality of linear electrodes are arranged in parallel in a first direction, and a plurality of second linear electrodes are arranged in parallel in a second direction orthogonal to the first direction; A centroid calculating unit that calculates the centroid position of the particle beam from the first signal that is output and the second signal that is output from the second linear electrode, and the centroid position over the range of two-dimensional scanning. A position information output unit for outputting, and a display unit connected to the position information output unit and displaying a locus of the center of gravity output from the position information output unit as a two-dimensional distribution of particle beam positions.

  The particle beam beam confirmation method according to the present embodiment includes a step of generating a particle beam, a step of controlling the emission of the particle beam, a step of two-dimensionally scanning the particle beam, and a parallel arrangement in a first direction. The first signal output from the first linear electrode and the second signal output from the second linear electrode arranged in parallel in the second direction orthogonal to the first direction The step of calculating the centroid position of the particle beam, the step of outputting the centroid position over the range of the two-dimensional scanning, and the locus of the centroid position during the two-dimensional scanning are directly displayed as the two-dimensional distribution of the particle beam position. Steps.

  The particle beam beam confirmation program according to the present embodiment includes a step of generating a particle beam beam, a step of controlling the emission of the particle beam beam, a step of two-dimensionally scanning the particle beam, and a parallel arrangement in a first direction. The first signal output from the first linear electrode and the second signal output from the second linear electrode arranged in parallel in the second direction orthogonal to the first direction A step of calculating a gravity center position of the particle beam, a step of outputting the gravity center position over a range of two-dimensional scanning, a step of directly displaying a locus of the gravity center position as a two-dimensional distribution of the particle beam position during the two-dimensional scanning, Is to execute.

  According to the present invention, a particle beam irradiation apparatus, a particle beam beam confirmation method, and a particle beam beam confirmation program capable of displaying a beam position in real time while irradiation is in progress are provided.

1 is a schematic external view of a particle beam irradiation apparatus according to an embodiment. The figure which shows the structural example of a strip type position monitor. The schematic block diagram of the control part of the particle beam irradiation apparatus concerning 1st Embodiment, and its peripheral device. The figure which shows an example of the display pattern of the locus | trajectory of the gravity center position of a display part. The timing chart which shows an example of the management and control of the dose and beam position in a three-dimensional raster scanning irradiation method. The schematic block diagram of the control part of the particle beam irradiation apparatus concerning 2nd Embodiment, and its peripheral device. (A) is a figure which shows an example of the display image which the particle beam beam irradiation apparatus concerning 2nd Embodiment displays, (B) is a modification of the display image which the particle beam beam irradiation apparatus concerning 2nd Embodiment displays. FIG. The flowchart which shows the particle beam beam confirmation method concerning 1st Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
(Schematic configuration)
FIG. 1 is a schematic external view of a particle beam irradiation apparatus 10 (hereinafter simply referred to as “irradiation apparatus 10”) according to an embodiment.
The irradiation apparatus 10 includes a beam generation unit 11, an emission control unit 12, a beam scanning unit 13, an X electromagnet 14a (14), a Y electromagnet 14b (14), a vacuum duct 16, a dose monitor 17, a position monitor 18, and a control unit. 19, a ridge filter 21, a range shifter 22, and the like.

The irradiation apparatus 10 is an apparatus for performing cancer treatment by irradiating, for example, a particle beam (hereinafter simply referred to as “beam”) obtained by accelerating particles such as carbon toward the affected area 24 of the cancer treatment patient 23. .
Hereinafter, the irradiation device 10 will be described as being a treatment device used for cancer treatment.
The irradiation apparatus 10 can be used for a three-dimensional scanning irradiation method in which the affected part 24 is divided into a three-dimensional lattice shape and a beam having a small diameter is sequentially irradiated to each spot (lattice point).

In the three-dimensional scanning irradiation method, first, the affected part 24 is divided into flat units called slices in the beam traveling direction (Z-axis direction in the coordinate system of FIG. 1).
Then, the affected part 24 is irradiated three-dimensionally by irradiating the two-dimensional spots (spots in the X-axis and Y-axis directions in the coordinate system in FIG. 1) of the divided slices while sequentially scanning.

  The beam generation unit 11 generates charged particles such as carbon ions and protons, and accelerates the charged particles to an energy that can reach deep into the affected part 24 with an accelerator to form a beam.

  The emission control unit 12 controls on / off of emission of the generated beam based on a control signal output from the control unit 19.

The beam scanning unit 13 deflects the beam in the X direction and the Y direction, and scans the slice surface in two dimensions.
The beam scanning unit 13 controls the excitation current of the X electromagnet 14a that scans in the X direction and the Y electromagnet 14b that scans in the Y direction.

  The dose monitor 17 monitors, for example, the dose of the irradiated beam by measuring the charge ionized by the particle beam passing through the housing.

The position monitor 18 measures the position of the scanned beam.
Here, FIG. 2 is a diagram illustrating a configuration example of the strip-type position monitor 18.
The position monitor 18 includes a strip type in which a plurality of strip electrodes 20 (collecting electrodes 20) are arranged, or a multi-wire type in which a plurality of wire electrodes are arranged.

As shown in FIG. 2, the strip-type position monitor 18 includes a plurality of strip electrodes 20 (a plurality of first linear electrodes) arranged in parallel in the X-axis direction (first direction). The electrodes 20 (a plurality of second linear electrodes) are arranged in parallel in the Y-axis direction (second direction orthogonal to the first direction).
By applying a potential to the high-voltage electrode 20c by the high-voltage power source 27, the surrounding strip-shaped electrode 20 through which the beam has passed collects charged particles generated by the ionization action according to the generation distribution, whereby a current flows through each strip. .

The control unit 19 (FIG. 1) controls the entire irradiation apparatus 10.
The control unit 19 monitors the dose of each spot on the basis of the output of the dose monitor 17 in the dose monitoring unit 25, for example, on / off control of beam emission of the emission control unit 12, and beam scanning to the beam scanning unit 13. Instruction, control of the range shift amount accompanying the slice change of the range shifter 22 and the like are performed.

For example, an abnormality may occur in the current setting of the scanning electromagnet power supply, or the beam position may be shifted in the upstream portion from the beam generation unit 11 to the emission control unit 12.
When such a beam shift or current setting abnormality occurs, a shift occurs between the specified position on the position monitor 18 specified in the treatment plan and the actual position coordinates.
In this case, an interlock signal is transmitted by the position monitoring unit 28 (FIG. 3) provided in the control unit 19, and the treatment irradiation is temporarily interrupted.
In the control unit 19 shown in FIG. 1, various functional blocks related to control of the dose monitoring unit 25, the emission control unit 12, the beam scanning unit 13, and the range shifter 22 are omitted.

The ridge filter 21 is provided for diffusing a sharp peak of the dose in the body depth direction called a Bragg peak.
The ridge filter 21 used in the three-dimensional scanning irradiation method is configured by juxtaposing a plurality of aluminum rod-like members having a substantially isosceles cross section.
The diffusion of the Bragg peak is adjusted by adjusting the shape of the isosceles triangle to adjust the path length difference when the beam passes through the isosceles triangle.

The range shifter 22 controls the range of the beam in the traveling direction (Z-axis direction) to change the range of the body and change the affected slice to be irradiated.
The range shifter 22 changes the combination of attenuation plates 22a of various thicknesses such as acrylic plates, and changes the energy of the beam passing through the range shifter 22, that is, the range of the body.
As a method for switching the range of the body, there is a method in which the energy of the beam itself is changed by controlling the upstream device without using the range shifter 22.

(First embodiment)
FIG. 3 is a schematic configuration diagram of the control unit 19 and its peripheral devices of the irradiation apparatus 10 according to the first embodiment.
Various functional blocks related to control of the dose monitoring unit 25, the emission control unit 12, the beam scanning unit 13, and the range shifter 22 are omitted.

  As shown in FIGS. 1 to 3, the irradiation apparatus 10 according to the first embodiment further includes a position information output unit 29 that outputs the center of gravity position G over a range of two-dimensional scanning, and a position information output unit 29. And a display unit 31 that displays the gravity center position G output from the position information output unit 29 as a two-dimensional distribution of particle beam positions.

In the collecting electrode 20 (20 a, 20 b) of the position monitor 18, for example, each channel of about 120 ch is connected to the center of gravity calculation unit 34 via the current evaluation circuit 32.
The current evaluation circuit 32 includes, for example, an I / V conversion unit 33, an amplification unit 35, an integration unit 36, and an ADC circuit 37 (hereinafter simply referred to as “ADC 37”).

For example, the integration unit 36 that stores the electric charge collected by each channel as an electric quantity may be omitted depending on the type of the irradiation apparatus 10.
The signal output from each channel is amplified by the current evaluation circuit 32, converted into an appropriate signal form, and sent to the centroid calculating unit 34.
The two collection electrodes 20 (20a, 20b) are connected to the corresponding current evaluation circuits 32, respectively.

The center-of-gravity calculation unit 34 is configured by, for example, an FPGA (Field Programmable Gate Array).
The center-of-gravity calculation unit 34 calculates the center of gravity G (Xc, Yc) for each of the two collecting electrodes 20 (20a, 20b) by calculating the center of gravity.
The center-of-gravity calculation unit 34 can assume that the beam spot having a spread is at one point of the center-of-gravity position G.

The calculated barycentric position G (Xc, Yc) is compared with a predetermined position setting value (Xr, Yr) in the position monitoring unit 28.
If these differences (Xc−Xr or Yc−Yr) exceed the allowable range, it is determined that the position is abnormal, an interlock signal is generated, and beam emission is stopped.
In addition, a position information output unit 29 is connected to the gravity center calculation unit 34.
The position information output unit 29 converts the barycentric position G calculated by the barycenter calculating unit 34 such as a serial signal converter or an analog signal converter into a signal that can be displayed on the display unit 31.

The center of gravity calculation unit 34 is connected to a dose profile calculation unit 38.
The dose profile calculation unit 38 temporarily stores information regarding the dose profile 30 and the gravity center position G output from the gravity center calculation unit 34.
When irradiation by scanning of one slice is completed, a beam trajectory and a dose are output as a dose profile 30 on the display unit 31 so as to overlap the slice image.

Further, the position information output unit 29 is directly connected to the display unit 31 without going through the dose profile calculation unit 38.
Then, the position information output unit 29 continuously outputs the gravity center position G to the display unit 31 over the range of two-dimensional scanning.
The display unit 31 displays the gravity center position G output from the position information output unit 29 as a two-dimensional distribution of beam positions.

Here, FIG. 4 is a diagram illustrating an example of a display pattern of the locus of the center of gravity position G of the display unit 31.
As shown in FIG. 4, by outputting the gravity center position G to the display unit 31, it is possible to change the viewing angle of the beam being scanned while moving the spot on the slice.
The display time of each spot where the beam is stopped is adjusted by a display time adjustment unit 39 connected to the display unit 31.

Each spot through which the beam has passed is displayed on the display unit 31 for a few seconds and fades out from the screen.
By specifying the display time and fading out the old trajectory, the latest trajectory can be visually recognized even if the trajectory overlaps several times. Since the irradiation time per slice of the particle beam therapy system is about 1 second, the time for fading out is preferably 0.1 second to 1 second that is the same as or shorter than the irradiation time per slice and can be visually recognized. ing.

Next, the particle beam verification method according to the first embodiment will be described with reference to the flowchart of FIG. 8 (refer to FIGS. 1 to 3 as appropriate).
First, the affected part 24 is virtually divided into a plurality of slices with respect to the beam axis, and one of the divided slices is selected.
First, for example, the slice at the deepest position of the affected part 24 is selected.
Further, the combination of the incident energy of the beam and the attenuation plate 22a in the range shifter 22 is selected and set according to the position of the selected slice (S11).

Next, the number M of spots to be irradiated with the beam and the position (Xi, Yi) [i = 1 to M] of the beam according to the affected part shape in the deepest slice, that is, the spot to be irradiated is selected (S12).
At the same time, the beam scanning unit 13 sets the beam direction at the spot position (Xi, Yi) on the slice.

Then, beam emission is started (S13).
The energy output of the beam output from the beam scanning unit 13 is expanded in the Z-axis direction by the ridge filter 21 so that the in-vivo range distribution width corresponds to the slice width.

Here, FIGS. 5A to 5G are timing charts showing an example of management and control of dose and beam position in the three-dimensional raster scanning irradiation method.
The excitation currents of the two electromagnets shown in FIGS. 5A and 5B correspond to the position setting values in the biaxial directions (X, Y).
Since the three-dimensional raster scanning irradiation method is used, the beam is continuously emitted as shown in FIG.

When the dose (dose monitor integrated dose, FIG. 5D) measured by the dose monitor 17 reaches a set value, a dose expiration signal (FIG. 5E) is output from the dose monitor 25.
Upon receiving this dose expiration signal, the excitation current is changed, and when the excitation current reaches a set value, the excitation current value is held.
The irradiation point of the beam moves in accordance with the transmission of the dose expiration signal shown in FIG.

In the integration unit 36, as shown in FIGS. 5F and 5G, for each channel of the position monitor 18, the integration is stopped, the data is read, and the integrated charge is cleared by the signal generated by the dose expiration signal. The integration starts continuously.
The amount of charge to be integrated is regarded as the sum of the collected charge generated while moving the irradiation point and the collected charge generated by the beam irradiated to the stop irradiation point.

The irradiation dose for the spot (Xi, Yi) is monitored by the dose monitor 17 and the dose monitor 25 (FIG. 5D).
The integrated value of the charge obtained by the integrating unit 36 based on FIGS. 5F and 5G is transmitted to the gravity center calculating unit 34.

The center-of-gravity position G on the two-dimensional coordinates calculated by the center-of-gravity calculation unit 34 is continuously displayed in real time on the display unit 31 by the position information output unit 29 during the progress of beam extraction (S14).
Each position coordinate through which the beam has passed is displayed on the display unit 31 for a time defined by the display time adjustment unit 39 and then fades out.
That is, the trajectory of the displayed beam fades out from the screen in order from the oldest as shown in FIG.

When the irradiation dose for the target spot reaches the planned dose, a dose expiration signal (FIG. 5E) is output to the control unit 19, and the beam moves to the next spot (S15).
This process is repeated until the final spot of the target slice (S16: NO: to S12).

When irradiation with respect to one slice is completed (S16: YES), beam emission is temporarily stopped (S17).
Then, an image of the slice irradiated with the beam is displayed on the display unit 31 as a dose profile together with the beam irradiation locus.
The above operation is repeated until the final slice is reached (S18: NO: to S11).
When the irradiation of the last slice is completed (S18: YES), the output related to the locus of the center of gravity position G from the position information output unit 29 is stopped (S19), and the operation ends.

  As described above, according to the irradiation apparatus 10 according to the first embodiment, the position of the beam can be displayed in real time while the irradiation is in progress.

(Second Embodiment)
FIG. 6 is a schematic configuration diagram of the control unit 19 and its peripheral devices of the irradiation apparatus 10 according to the second embodiment.
FIG. 7A is a diagram illustrating an example of a display image displayed by the irradiation apparatus 10 according to the second embodiment.

As illustrated in FIG. 6, the irradiation apparatus 10 according to the second embodiment includes an affected part shape holding unit 43 that holds data regarding the outline 42 of the affected part 24.
The affected part shape holding part 43 is connected to the display part 31 and the dose monitoring part 25, for example, and displays the outline 42 of the affected part 24 on the display part 31 in synchronization with slice switching (S17 to S19).
The outline 42 of the affected area 24 is, for example, a slice cross-sectional image 44 of the affected area 24 created in advance during a treatment plan.

By displaying the outline 42 of the affected part 24 that has been irradiated along with the locus of the center of gravity G, the operator can more accurately grasp the state of work.
For example, as shown in FIG. 7A, the slice cross-sectional image 44 and the beam trajectory image 46 are displayed side by side.

FIG. 7B is a diagram showing a modification of the display image displayed by the irradiation apparatus 10 according to the second embodiment.
More preferably, the coordinate system of the outline 42 of the affected part 24 and the coordinate system of the locus of the center of gravity G are overlapped and displayed as the locus image 47 with the affected part outline.
Thus, by displaying the coordinate system of the outline 42 of the affected area 24 together with the coordinate system of the locus of the center of gravity position G and the coordinate system of the outline 42 of the affected area 24, which position of the affected area 24 is irradiated, It can be grasped more specifically.

  In FIG. 6, as an example, the affected part shape holding unit 43 is connected to the display unit 31 and the dose monitoring unit 25, but may be connected to other devices depending on the type of data on the affected part shape to be held. .

Since the second embodiment has the same structure and operation procedure as those of the first embodiment except that the outline 42 of the affected part 24 is displayed together with the center of gravity position G, redundant description is omitted.
Also in the drawings, portions having a common configuration or function are denoted by the same reference numerals, and redundant description is omitted.

As described above, according to the irradiation apparatus 10 according to the second embodiment, in addition to the effects of the first embodiment, it can be displayed together with the outline 42 of the affected part 24, so that the state of the beam during the irradiation is more specific. Can grasp.
Furthermore, by displaying the coordinate system of the outline 42 of the affected part 24 and the coordinate system of the position monitor 18 in an overlapping manner, it is possible to more accurately grasp which part of the affected part 24 is being scanned.

  According to the irradiation apparatus 10 of at least one embodiment described above, the information on the barycentric position G of the beam measured and calculated by the position monitor 18 is directly output to the display unit 31, so that the irradiation of the beam can be performed while the irradiation is in progress. The position can be displayed in real time.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention.
These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the scope of the invention.
These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Particle beam irradiation apparatus (irradiation apparatus), 11 ... Beam generation part, 12 ... Ejection control part, 13 ... Beam scanning part, 14a ... Electromagnet for X, 14b ... Electromagnet for Y, 16 ... Vacuum duct, 17 ... Dose Monitor, 18 ... Position monitor, 19 ... Control unit, 20 ... Collection electrode (strip-shaped electrode), 21 ... Ridge filter, 22 (22a) ... Range shifter (attenuation plate), 23 ... Cancer treatment patient, 24 ... Diseased part, 25 ... Dose monitoring unit, 27 ... high voltage power supply, 28 ... position monitoring unit, 29 ... position information output unit, 30 ... dose profile, 31 ... display unit, 32 ... current evaluation circuit, 33 ... V conversion unit, 34 ... centroid calculation unit, 35 ... amplifying unit, 36 ... integrating unit, 37 ... ADC circuit, 38 ... dose profile calculating unit, 39 ... display time adjusting unit, 40 ... timing circuit, 42 ... outer, 43 ... affected part shape holding unit, 44 ... slice section Image, 46 ... image, 47 ... diseased shell with path image, G ... center-of-gravity position.

Claims (7)

A beam generator for generating a particle beam;
An emission control unit for controlling the emission of the particle beam;
A beam scanning unit for two-dimensionally scanning the particle beam;
A position monitor in which a plurality of first linear electrodes are arranged in parallel in a first direction and a plurality of second linear electrodes are arranged in parallel in a second direction orthogonal to the first direction;
A centroid calculating unit that calculates a centroid position of the particle beam from the first signal output from the first linear electrode and the second signal output from the second linear electrode;
A position information output unit that outputs the position of the center of gravity over the range of the two-dimensional scanning;
A particle beam irradiation, comprising: a display unit connected to the position information output unit and displaying a locus of the center of gravity output from the position information output unit as a two-dimensional distribution of particle beam position. apparatus. The particle beam irradiation apparatus according to claim 1, further comprising: a display time adjusting unit that adjusts a time for displaying the gravity center position on the display unit. The particle beam is irradiated to an affected area of a cancer treatment patient,
The particle beam irradiation apparatus according to claim 1, wherein an outline of the affected part is displayed on the display unit together with a locus of the center of gravity. 4. The particle beam irradiation apparatus according to claim 3, wherein a coordinate system of an outline of the affected part is displayed so as to coincide with a coordinate system of the center of gravity position. The particle beam irradiation apparatus according to claim 3 or 4, wherein an outline of the affected part is a slice cross-sectional image of the affected part. Generating a particle beam;
Controlling the emission of the particle beam;
Two-dimensionally scanning the particle beam;
A first signal output from the first linear electrodes arranged in parallel in the first direction and an output from the second linear electrodes arranged in parallel in the second direction orthogonal to the first direction Calculating the position of the center of gravity of the particle beam from the second signal,
Outputting the center-of-gravity position over the range of the two-dimensional scan;
Directly displaying the locus of the center of gravity position as a two-dimensional distribution of particle beam positions during the two-dimensional scanning. On the computer,
Generating a particle beam;
Controlling the emission of the particle beam;
Scanning the particle beam two-dimensionally;
A first signal output from the first linear electrodes arranged in parallel in the first direction and an output from the second linear electrodes arranged in parallel in the second direction orthogonal to the first direction Calculating a gravity center position of the particle beam from the second signal
Outputting the center of gravity position over the range of the two-dimensional scan;
A particle beam confirmation program for executing the step of directly displaying the locus of the center of gravity position as a two-dimensional distribution of particle beam positions during the two-dimensional scanning.