JP5693876B2 - Particle beam irradiation apparatus and particle beam irradiation program - Google Patents

Description

  The present invention relates to a particle beam irradiation technique for performing treatment by irradiating an affected area such as cancer with a charged particle beam.

With respect to malignant tumors such as cancer, particle beam irradiation treatment methods using charged particle beams of carbon and protons have attracted attention due to excellent features such as high therapeutic effects, few side effects, and reduction of burden on the body. According to this treatment method, cancer cells can be aimed at the charged particle beam emitted from the accelerator, the influence on normal cells can be minimized, and the cancer cells can be killed.
In this treatment method, a conventionally applied particle beam irradiation method called an expanded beam method enlarges the charged particle beam diameter to be larger than the affected part size and restricts the irradiation region with a collimator so as to match the affected part shape.
However, this expanded beam method has difficulty in making the irradiation region exactly match the three-dimensional shape of the affected area, and has a limit in reducing the influence on normal cells around the affected area.

  Therefore, a technique called a three-dimensional scanning irradiation method, in which a charged particle beam is incident on a spot obtained by dividing an affected area into three-dimensional lattice points with high accuracy, has been developed. According to this three-dimensional irradiation method, it becomes possible to match the irradiation region to the affected region with high accuracy, and the exposure to normal cells can be suppressed (for example, Patent Document 1).

JP 2008-237687 A

  In the three-dimensional scanning irradiation method, it is desired to increase the speed of spot switching. In order to improve the spot switching speed, a method of improving the speed of the current for exciting the deflection magnetic field applying means can be considered. However, if the speed of the excitation current is increased too much, the overshoot of the spot with respect to the target arrival point becomes large and the accuracy of spot switching decreases, so there is a limit to the speed improvement.

  On the other hand, after the dose of a charged particle beam incident on one spot reaches a specified value, the delay in the output of a switching instruction for aiming the charged particle beam at the next spot is also a factor that hinders the speed of spot switching. As mentioned.

  The present invention has been made in consideration of such circumstances, and has the stability and certainty of spot switching, and the particle beam irradiation that realizes high speed spot switching by reducing the output delay of the spot switching instruction. The purpose is to provide technology.

  In the particle beam irradiation apparatus, an accumulation unit that accumulates parameters corresponding to each of a plurality of m-th spots in the subject represented by a natural number m, and a current that is output to the deflection magnetic field applying unit with each parameter as a target An excitation unit that switches and sequentially enters charged particle beams to the plurality of m-th spots, and dose integration that outputs a first signal when the dose of charged particle beams incident on the m-1 spot reaches a specified value. Unit, an acquisition unit for acquiring the parameter corresponding to the (m + 1) th spot from the storage unit in synchronization with the output of the first signal, and the parameter corresponding to the mth spot previously acquired by the acquisition unit And a switching instruction unit that outputs the signal to the excitation unit in synchronization with the first signal.

  ADVANTAGE OF THE INVENTION According to this invention, the particle beam irradiation technique which has the stability and certainty of spot switching, and shortens the output delay of the spot switching instruction | indication and implement | achieves high-speed spot switching is provided.

The block diagram which shows embodiment of the charged particle beam irradiation apparatus which concerns on this invention. A table showing parameters corresponding to each of the m-th spot (m: natural number). The timing chart which shows operation | movement of the component of the charged particle beam irradiation apparatus which concerns on this invention. The timing chart which shows operation | movement of the component of the charged particle beam irradiation apparatus which concerns on this invention. The timing chart which shows operation | movement of the component of the charged particle beam irradiation apparatus which concerns on this invention. The flowchart which shows operation | movement of the charged particle beam irradiation apparatus which concerns on this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, a charged particle beam irradiation apparatus 10 (hereinafter simply referred to as apparatus 10) includes a charged particle gun 11 that emits charged particles in the Z-axis direction, and a first deflection magnetic field that deflects the charged particles in the X direction. Applying means 12x (12), second deflecting magnetic field applying means 12y (12) for deflecting the charged particles in the Y direction, dose detecting section 13 for detecting the dose of the charged particles, dose integrating section 14, and charging A gun control unit 15 that controls the energy of charged particles emitted from the particle gun 11, a first excitation unit 30x (30) that outputs an excitation current to the first deflection magnetic field applying unit 12x, and a second deflection magnetic field applying unit 12y The second excitation unit 30y (30) that outputs the excitation current to the control unit 20 and the control unit 20 that controls the intensity and timing of the excitation current output by the excitation unit 30 are configured.
In addition, since the structure of the 2nd excitation part 30y is the same as the 1st excitation part 30x, detailed description is abbreviate | omitted in drawing.

The apparatus 10 configured as described above sequentially enters charged particle beams on the spots (1 to n) set on the slice surfaces 41, 42, and 43 of the affected area 40 of the subject (not shown). It is something to be made.
Here, the total number of irradiation spots is n, and the natural number n represented by 1 ≦ m ≦ n is a variable indicating an arbitrary spot. Then, a serial number is assigned like the m-th spot (m: natural number) according to the order in which the charged particle beam is incident with the spot at the start of irradiation as the first spot.

Next, the relationship between the depth of the affected area 40 where the charged particle beam enters and the energy of the charged particle beam will be described.
The charged particle beam loses kinetic energy when passing through the subject and decreases its speed, and when it decreases to a certain speed due to resistance almost inversely proportional to the square of the speed, it stops suddenly. In the vicinity of the stop point of the charged particle beam, a large dose called a Bragg peak is generated.

Each m-th spot is set to be the position of the Bragg peak of the charged particle beam. The position of this Bragg peak depends on the energy of the charged particle beam.
For this purpose, a plurality of slice planes 41, 42, and 43 are set in the XY plane orthogonal to the charged particle beam emission direction (Z axis) in the affected area 40. Then, the position of the slice surfaces 41, 42, and 43 on which the charged particle beam enters is changed by changing the energy emitted from the charged particle gun 11 by the gun control unit 15. As another method of changing the positions of the slice surfaces 41, 42, 43, there is a method of reducing the energy of the charged particle beam by inserting a plastic plate or the like in front of the subject.

The charged particle gun 11 includes an ion source (not shown), a charged particle beam generator (linac), and an accelerator (synchrotron).
Ions generated by the ion source (for example, proton ions (or carbon ions)) are accelerated by the linac and further accelerated by being given energy by the synchrotron.
The charged particle beam is emitted to the subject after the energy is increased to, for example, 100 to 200 MeV.

Although not described in detail, the gun control unit 15 includes means for changing the energy of the charged particle beam emitted from the charged particle gun 11 and means for stopping emission of the charged particle beam from the subject. Have.
The charged particle gun 11 continuously emits the charged particle beam from before the stable charged particle beam enters the spot 1 until the charged particle beam finishes entering the spot n, as shown in the uppermost stage of FIG. doing.
Further, in the drawing, the energy output of the charged particle beam is described constant over the entire period, but may be set to an optimum value that differs for each spot.

The deflecting magnetic field applying means 12 (FIG. 1) forms a magnetic field between the exciting coils 30 by applying an electric current to the pair of opposed coils. The charged particle beam passing through the magnetic field is bent in the X-axis direction and the Y-axis direction by the Lorentz force, and is incident on a spot at an arbitrary position on the slice surface 41.
Then, by changing the intensity of the current applied to the excitation unit 30 and changing the magnetic field intensity, the aim of the spot on which the charged particle beam is incident is switched.

Here, the curve shown at the bottom of FIG. 3 shows the deflection magnetic field applying means 12 when the charged particle beam is switched to each spot (m−2, m−1, m, m + 1, m + 2) and incident. The response of the supplied current is shown.
By quickly switching the spots, the intensity of the charged particle beam can be increased and irradiation to the affected area 40 can be completed in a short time, the burden on the patient can be reduced, and the number of patients can be increased. .

Further, while the charged particle beam is being irradiated, the position of the affected area is constantly changing due to breathing or the like. However, by quickly switching the spot, the deviation between the affected area 40 and the actual irradiation position can be reduced.
In order to realize such a quick spot switching, it is desirable that the current response shows a broken line profile, but in reality, it shows a response delay or a transient response as shown in the figure.

The dose integrating unit 14 (FIG. 1) integrates the dose of the charged particle beam detected by the dose detecting unit 13 as shown in the second stage of FIG. 3, and the dose of the charged particle beam incident on the aiming spot. When the signal reaches the specified value q, the first signal s1 is output to the control unit 20.
Simultaneously with the output of the first signal s1, the integration is reset and the integration is repeated until the charged particle beam dose reaches the specified value q again.
The prescribed value q of the charged particle beam dose is prescribed for each spot, as shown in the second row of FIG. 2, and is stored in the parameter accumulating unit 21 (FIG. 1).

  As described above, by operating the dose integrating unit 14, even if the intensity of the charged particle beam fluctuates, the dose incident on each aimed spot can be set to a desired value. Moreover, since the prescribed value q can be set for each spot, an intensity distribution can be given to the charged particle beam irradiated to the affected area 40.

The control unit 20 includes a parameter storage unit 21, a parameter acquisition unit 22, a parameter switching instruction unit 23, a switchability determination unit 24, and a current value display unit 25.
The first excitation unit 30x and the second excitation unit 30y (hereinafter simply referred to as the excitation unit 30) include a current generator 33 that supplies current to the deflection magnetic field applying unit 12, and current detection that detects the supplied current value. A comparator 35 that compares the supplied current value with the target value, and an AD conversion unit 37 that replaces the supplied current value with a display signal.

By configuring the control unit 20 in this way, an instruction to switch the aim of the spot on which the charged particle beam is incident is given to the excitation unit 30 using the first signal s1 output from the dose integrating unit 14 as a trigger. .
The excitation unit 30 switches the current supplied to the deflection magnetic field applying unit 12 to the current target value (FIG. 2) of the parameter corresponding to the aiming spot.

  By repeating such an operation, charged particle beams are sequentially incident on a plurality of spots in the affected area 40 shown in FIG. When irradiation with charged particle beams to all spots on a slice 41 is completed, the energy of the charged particle beam is changed by the gun control unit 15 so that the Bragg peak is positioned in the next slice 42. In this manner, such irradiation is repeated for all slices 41, 42, 43 obtained by dividing the affected area 40 in the depth direction, and irradiation of the entire affected area is completed.

  As shown in FIG. 2, the storage unit 21 stores parameters corresponding to each of a plurality of m-th spots in the subject represented by a natural number m. As will be described later, this parameter is a transmission signal p in which a current target value and a control constant for one vertical column are combined into one transmission signal p, which is finally sent to the excitation unit 30, and the prescribed dose value is a dose integration unit 14. Sent to. Further, these parameters are determined based on data such as the irradiation position, irradiation amount, irradiation energy, and characteristics of the irradiation apparatus of the charged particle beam created in the treatment plan for each patient.

In this embodiment, the parameters include the control constants of the excitation unit 30 (the five values in FIG. 2) in addition to the current target value (third and fourth stages in FIG. 2) of the current that the excitation unit 30 supplies to the deflection magnetic field applying means 12. , Sixth stage) or a prescribed value q of charged particle beam dose (second stage in FIG. 2).
Here, the purpose of the control constant of the excitation unit 30 is to eliminate the response delay of the rise in the current profile shown at the bottom of FIG. 3 and the transient response after reaching the target value.

The acquisition unit 22 (FIG. 1) refers to FIG. 3, and the first signal instructing that the dose of the charged particle beam incident on the (m−1) -th spot reaches the specified value q and switches the aim to the m-th spot. The parameter corresponding to the (m + 1) th spot is acquired from the storage unit 21 in synchronization with the output of s1.
Then, the acquisition unit 22 calculates the parameter acquired from the storage unit 21 into a transmission signal p * for the switching instruction unit 23 to transmit to the excitation unit 30 and transmits it to the switching instruction unit 23.

The switching instruction unit 23 outputs the transmission signal p of the parameter corresponding to the m-th spot previously acquired by the acquisition unit 22 to the excitation unit 30 in synchronization with the first signal s1 received from the dose integration unit 14. .
As described above, the parameter acquisition unit 22 and the switching instruction unit 23 work together to eliminate the delay in the spot aiming switching instruction. That is, when the acquisition unit 22 is not used, the actual current supply in the excitation unit 30 is performed only during the period from when the acquisition unit 22 receives the first signal s1 to when the calculation is performed and the transmission signal p * is transmitted. Will be delayed.
According to the present embodiment, since it is not necessary to calculate the parameter to the transmission signal p in the switching instruction unit 23, when the first signal s1 is received from the dose integrating unit 14, the parameter transmission signal p is immediately converted to the excitation unit 30. Can contribute to high-speed switching of spot aiming.

The current generator 33 receives the parameter transmission signal p from the switching instruction unit 23 and supplies the deflection magnetic field applying means 12 with a current for moving the charged particle beam to the next spot.
Switching of the current supplied to the deflection magnetic field applying means 12 is performed by the operation of a switching element (not shown) constituting the current generator 33.

The current detector 35 detects the value of the current supplied from the current generator 33 to the deflecting magnetic field applying means 12, and specifically outputs a profile shown in the fourth row of FIG.
When the current value detected by the current detector 35 reaches around the current target value (FIG. 2) included in the parameter transmission signal p, as shown in the fifth row of FIG. The second signal s2 is output.

As shown in FIG. 1, the determination unit 24 receives the first signal s1 from the dose integration unit 14 and the second signal s2 from the comparison unit 36, and outputs the parameter transmission signal p in the switching instruction unit 23. Whether or not is possible is determined.
Specifically, as illustrated in FIG. 4, after the switch instruction unit 23 outputs the parameter transmission signal p for the m-th spot, the next m + 1-th signal is output prior to the second signal s <b> 2 from the comparison unit 36. The first signal s1 for the spot may be output.

In such a case, since the charged particle beam is not actually incident on the m-th spot, the charged particle beam is synchronized with the second signal s2 output after the first signal s1 with respect to the m + 1-th spot. The switching instruction unit 23 outputs the transmission signal p for the spot to the excitation unit 30.
As shown in the sixth row of FIG. 4, such an operation is performed when the determination unit 24 inputs either the first signal s <b> 1 or the second signal s <b> 2, and a binary signal alternately indicating true / false. The parameter transmission signal p is output to the excitation unit 30 in synchronization with the true signal.
Alternatively, in such a case (when the first signal s1 is output prior to the second signal s2), the illustration of the drawing is omitted, but the gun control unit 15 is informed of the charged particle beam to the subject. Incident may be stopped.
Accordingly, the charged particle beam can be accurately incident on the aiming spot, and the treatment can be interrupted when there is a concern that the exposure dose of the patient increases.

Further, as shown in the lowermost stage of FIG. 4, after the transmission signal p of the previous parameter is output from the switching instruction unit 23, the interval is shorter than the interval v in which stable operation of current switching in the excitation unit 30 is ensured. In some cases, the next transmission signal p may be output.
In such a case, the determination unit 24 prevents the excitation unit 30 from switching the current in synchronization with the output of the next parameter, and instructs the gun control unit 15 to apply the charged particle beam to the subject. Stop the incidence.

This is because if the switching frequency of the current supplied from the current generator 33 continues to be high, the load on the switching element increases and may cause heat generation, deterioration, and damage. According to the present embodiment, the current switching frequency in the current generator 33 is limited, and further, the operation exceeding the performance of the switching element is prevented by stopping the emission of the charged particle beam, and the soundness of the high-speed switching of the current is improved. Can be maintained.
Note that this determination is not necessarily performed when the current target values before and after switching are the same, or when it is clear that switching of current does not increase the load of the switching element. Further, the interval v at which stable operation of current switching is ensured can be determined according to the state of heat generation of the switching element or can be changed as appropriate.

The AD conversion unit 37 converts an analog signal indicating a current value into a digital signal in synchronism with the output of the parameter transmission signal p from the switching instruction unit 23, as shown in the lowermost stage of FIG. Here, the AD conversion unit 37 holds the analog value of the current detector 35 at the time of transmission of the transmission signal p, and digitally converts it. The period u is the time required for this digital conversion, and the converted current value r is transmitted to the current value display unit 25.
According to this, it is possible to read the current value without disturbing the high-speed conversion of the current, and it is possible to grasp the accurate reached value of the current. Then, it can be determined whether or not the charged particle beam is accurately incident on the aimed spot.

The operation of the apparatus 10 will be described based on FIG. 6 (see FIG. 1 as appropriate).
First, the affected area 40 of the subject is determined and a spot on which a charged particle beam is incident is set (S11). Then, parameters (FIG. 2) such as a prescribed value q of the charged particle beam dose and a current target value of the excitation unit 30 are set for each spot and stored in the storage unit 21 (S12).

Next, the current supplied to the deflection magnetic field applying means 12 is adjusted in the excitation unit 30 so that the charged particle beam is aimed at the m-th spot (S13), and the charged particle gun 11 is operated to bring the charged particle beam into the subject. Incident incidence (S14; Yes, S15). At this time, the excitation unit 30 controls the current supplied to the deflection magnetic field applying means 12 so that it converges to the parameter current target value within a short time.
And the excitation part 30 continues supplying an electric current until the dose of the charged particle beam which injected into this aiming spot reaches the regulation value q in the dose integration part 14 (S16: No).

Then, when the dose of the charged particle beam reaches the specified value q, the dose integrating unit 14 outputs the first signal s1 (S17). At this time, if the second signal s2 has already been output from the excitation unit 30, it is clear that the current supplied by the excitation unit 30 has already reached the target value, and thus the process proceeds to the next determination (S18: Yes). ).
Furthermore, if the interval at which the first signal s1 is output satisfies the interval v at which the stable operation of the current generator 33 is ensured (S19: Yes), a parameter transmission signal for the next spot from the switching instruction unit 23. p is sent to the excitation unit 30 (S20).

  If the second signal s2 is not output and the first signal s1 is continuously output (S18: No solid line), or if the switching frequency of the excitation unit 30 is high and the operation is determined to be unstable (S19: No solid line). ), The incidence of the charged particle beam from the charged particle gun 11 is stopped (S23). Alternatively, after waiting for time (S18, S19: No broken line), a spot switching instruction is given (S20).

Next, in order to determine whether the incident position of the charged particle beam coincides with the aimed spot or not, at the timing when the parameter transmission signal p is transmitted from the switching instruction unit 23, the current detector 35 The detected analog signal is converted into a digital signal and displayed (S21).
Then, the aim of the charged particle beam is adjusted to the next spot (S22: No, S14: No) and repeated until irradiation of all the spots is completed (S22: Yes).

In the above description, the present invention is not limited to the above-described embodiment, and can be appropriately modified and implemented within the scope of the common technical idea.
For example, the charged particle beam irradiation apparatus 10 can also realize each unit as a function program by a computer, and can also function as a particle beam irradiation program by combining the function programs.

  DESCRIPTION OF SYMBOLS 10 ... Charged particle beam irradiation apparatus, 11 ... Charged particle gun, 12 (12x, 12y) ... Deflection magnetic field provision means, 13 ... Dose detection part, 14 ... Dose integration part, 15 ... Gun control part, 20 ... Control part, 21 ... Accumulation part, 22 ... Acquisition part, 23 ... Switching instruction part, 24 ... Determination part, 25 ... Current value display part, 30x (30) ... First excitation part (excitation part), 30y (30) ... Second excitation part (Excitation unit), 33 ... current generator, 35 ... current detector, 36 ... comparison unit, 37 ... AD conversion unit, 40 ... affected area, 41, 42, 43 ... slice plane, s1 ... first signal, s2 ... Second signal, p ... transmission signal.

Claims (8)

An accumulator that accumulates parameters corresponding to each of a plurality of m-th spots in the subject represented by a natural number m;
An excitation unit that sequentially switches the current output to the deflecting magnetic field applying unit with each parameter as a target and causes charged particle beams to sequentially enter the plurality of m-th spots;
A dose integrating unit that outputs a first signal when the dose of the charged particle beam incident on the (m-1) -th spot reaches a specified value;
An acquisition unit that acquires the parameter corresponding to the (m + 1) th spot from the storage unit in synchronization with the output of the first signal;
A particle beam irradiation apparatus comprising: a switching instruction unit that outputs the parameter corresponding to the m-th spot previously acquired by the acquisition unit to the excitation unit in synchronization with the first signal. In the particle beam irradiation apparatus of Claim 1,
The excitation unit includes a comparison unit that outputs a second signal indicating that the output current has reached the input parameter.
When the first signal is output prior to the second signal after the previous parameter is output from the switching instruction unit, the second signal is output in synchronization with the second signal output after the first signal. A particle beam irradiation apparatus comprising: a determination unit that outputs a next parameter. In the particle beam irradiation apparatus according to claim 2,
The determination unit stops the incidence of the charged particle beam on the subject when the first signal is output prior to the second signal. The particle beam irradiation apparatus according to any one of claims 1 to 3,
The excitation unit includes an AD conversion unit that converts an analog signal indicating the value of the current into a digital signal in synchronization with the output of the parameter from the switching instruction unit. In the particle beam irradiation apparatus of any one of Claims 1-4,
When the next parameter is output at an interval shorter than the interval at which stable operation of current switching in the excitation unit is ensured after the previous parameter is output from the switching instruction unit, the excitation unit The particle beam irradiation apparatus is characterized in that the switching of the current synchronized with the output of is not executed. In the particle beam irradiation apparatus of Claim 5,
Furthermore, the particle beam irradiation apparatus characterized by stopping the incident of the charged particle beam to the subject. The particle beam irradiation apparatus according to any one of claims 1 to 6,
In addition to the target value of the current output from the excitation unit, the parameter includes a control constant of the excitation unit or a prescribed value of the dose of the charged particle beam. Computer
Means for accumulating a parameter corresponding to each of a plurality of m-th spots in a subject represented by a natural number m;
Means for switching the current output to the deflecting magnetic field applying means for each of the parameters as a target and causing charged particle beams to sequentially enter the plurality of m-th spots;
Means for outputting the first signal when the dose of the charged particle beam incident on the (m-1) th spot reaches a specified value;
Means for obtaining the parameter corresponding to the (m + 1) th spot from among the accumulated ones in synchronization with the output of the first signal;
The parameters of the particle beam irradiation program in synchronization with the first signal, characterized in that to function as a means for Ru is between the target corresponding to the m spot is acquired first.

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