Patent Application
20180008841
The present invention relates to a particle beam therapy system that performs particle beam irradiation for cancer treatment and the like as application of a particle beam, and more particularly to a treatment planning apparatus for the therapy system.
Particle beam irradiation methods for particle beam therapy systems are roughly categorized into two methods: a broad irradiation method and a scanning irradiation method. In a wobbler method, which is one type of the broad irradiation method, a charged particle beam is spread by being scanned with scanning electromagnets in a circular pattern and is shaped to irradiate an irradiation object in accordance with the shape thereof. The scanning irradiation method is for performing irradiation by scanning a charged particle beam across an irradiation object with scanning electromagnets. In a scanning irradiation method, irradiation is generally performed with the irradiation dose being controlled for each of irradiation points. In the broad irradiation method typified by the wobbler method, on the other hand, irradiation is performed with the irradiation dose being not controlled for each of irradiation points but controlled for an irradiation region as a whole.
The wobbler method is a conventionally used irradiation method, and has a merit in that there have been many actual results in clinical practice but has a demerit in that a bolus (typically formed of resin) needs to be fabricated to mimic a distal shape of a diseased site on a patient-by-patient basis.
The scanning irradiation method, although having a merit of performing a three-dimensional irradiation with increased flexibility, has some demerits such as in that there have yet been fewer actual results in clinical practice than the broad irradiation method because the scanning irradiation method is a recent technology and in that optimization calculation takes time to formulate a treatment plan.
From a viewpoint of development of irradiation apparatuses in particle beam therapy systems, an irradiation nozzle for the wobbler method was first developed and then an irradiation nozzle for the scanning irradiation method was developed. Buyers of those days were requested to alternatively decide, as an irradiation apparatus in one treatment room, whether an irradiation nozzle for the broad irradiation method or an irradiation nozzle for the scanning irradiation method. After that, there were proposed an irradiation nozzle that achieved both broad irradiation and scanning irradiation with one irradiation nozzle, and there were also proposed a gantry that was provided with two irradiation lines (Patent Document 1), thus increasing flexibility in the treatment methods.
In an irradiation nozzle provided to one irradiation line, there is also known an irradiation nozzle that operates in either one of a broad irradiation configuration and a scanning irradiation configuration and retracts the other unused configuration not to interrupt the charged particle beam irradiation (Patent Documents 2 and 3).
Patent Document 1: JP2010-158479 A;
Patent Document 2: JP2009-236867 A;
Patent Document 3: WO2013/011583 A1
While a gantry equipped with two irradiation lines and an irradiation nozzle capable of performing the broad irradiation and the scanning irradiation with one irradiation nozzle have been thus put into practical use, usage thereof is no more than that one of the irradiation methods is alternatively determined for one patient. This poses a problem in that the demerit of the broad irradiation method still remains when the broad irradiation method is selected or the demerit of the scanning irradiation method still remains when the scanning irradiation method is selected.
In consideration of the above problem, the present invention is aimed at achieving a highly accurate and highly flexible irradiation that utilizes the respective merits of the broad irradiation and the scanning irradiation by performing these irradiations for one diseased site.
The present invention offers a treatment planning apparatus configured to formulate a treatment plan that allows a particle beam therapy system to irradiate an irradiation object with a particle beam extracted from an accelerator, by switching between a scanning irradiation from a scanning irradiation nozzle mounted with scanning irradiation use parts for the scanning irradiation that is performed while shifting the particle beam and controlling an irradiation dose imparted to each of points in the irradiation object and a broad irradiation from a broad irradiation nozzle mounted with broad irradiation use parts for the broad irradiation that is performed by controlling a total irradiation dose imparted to a region in the irradiation object, the treatment planning apparatus includes an overall data management unit configured to store a target irradiation dose distribution to be formed in the irradiation object; a broad irradiation parameter calculation unit configured to calculate operational parameters for respective devices, such as the accelerator and the broad irradiation nozzle, to operate during the broad irradiation; and a scanning irradiation parameter calculation unit configured to calculate operational parameters for the respective devices, such as the accelerator and the scanning irradiation nozzle, to operate during the scanning irradiation, wherein the broad irradiation parameter calculation unit and the scanning irradiation parameter calculation unit cooperatively calculate and determine the operational parameters for the respective devices, such as the accelerator and the broad irradiation nozzle, to operate during the broad irradiation and the operational parameters for the respective devices, such as the accelerator and the scanning irradiation nozzle, to operate during the scanning irradiation, so that the sum of irradiation doses imparted by both broad irradiation and scanning irradiation forms the target irradiation dose distribution.
A treatment planning apparatus according to the present invention enables a treatment plan to be formulated in a short time and allows for constructing a particle beam therapy system that imparts irradiation doses with high accuracy to diseased sites of various shapes.
Next, the operation of the irradiation nozzle will be described. In a case of the scanning irradiation, in order to make small the beam spot size at beam irradiation points by suppressing scattering of the particle beam as far as possible, a vacuum duct is generally disposed close up to the beam irradiation points. Since the scatterer 41 is unnecessary in this case, it is retracted to the side of the beam line 100 within the vacuum duct 21. In a case of the particle beam being a proton beam, the ridge filter 42 is unnecessary for the scanning irradiation; however, a ridge filter may be used in some cases for the other particle beam, to increase the energy width slightly. For example, in a case of a heavy particle beam such as a carbon ion beam, since the beam has a very sharp Bragg peak width compared to a proton beam, a ridge filter may be used to form a spread-out Bragg peak (SOBP) in order to irradiate a certain depth width (several mm) in one scan thereby to reduce irradiation time. Note that the ridge filter is for spreading out the Bragg peak width to several mm and its bar ridge height may be shorter than the SOBP width even though the ridge filter is disposed at a position not away from the irradiation object. Accordingly, a ridge filter can be used for the heavy particle beam that is manufactured much easier than that for the broad irradiation. Furthermore, the penetration depth (penetration range) of the particle beam depends on the energy of the particle beam; hence, varying the energy of the particle beam is necessary to vary the penetration range thereof. Performing change of the energy only by energy adjustment of the accelerator poses a problem of taking time to change the energy. For that reason, a range shifter for reducing the energy of the particle beam is used in some cases to vary the energy of the particle beam. Considering the fact that the particle beam is scattered by the range shifter, the range shifter is desirably disposed as downstream as possible, in other words, in a position as close as possible to the irradiation object. Accordingly, in performing the scanning irradiation using the ridge filter 42 and the range shifter 43, they are preferably arranged as shown in
Switching from the scanning irradiation to the broad irradiation is described next.
In
After the scanning irradiation use vacuum duct 22 is dismounted, since the connection flange plane 27 becomes an end plane for the vacuum condition, a beam extraction window 23b is attached to the flange plane 27 as shown in
In this way, the broad irradiation is enabled. The bolus 44 and the patient collimator 45 can be easily mounted by attaching insertion holders therefor to the bottom face of the range shifter 43 with rails or the like. The ridge filter 42 and the range shifter 43 can be inserted using a linear translation mechanism or a rotational translation mechanism driven by air or a motor. While the scanning irradiation use vacuum duct 22 is slidably retracted in the above configuration, providing a rotatable support mechanism also allows the retraction and the insertion of the vacuum duct 22 to be switched to each other by rotating the support mechanism.
If no vacuum separation plane was provided upstream the scanning irradiation use vacuum duct 22 and the scanning irradiation use vacuum duct 22 communicated to the upstream, retraction of the scanning irradiation use vacuum duct 22 would result in breakage of the vacuum condition throughout the beam lines. In this case, it takes time to increase the degree of vacuum. Hence, the gate valve 28 is preferably disposed immediately upstream the scanning electromagnets 25. The gate valve may also be disposed in a position immediately downstream the scanning electromagnets 25. When the scanning irradiation use vacuum duct 22 is dismounted, closing the gate valve 28 allows influence to the degree of vacuum to be limited to only the downstream of the gate valve 28. At that time, configuring the gate valve 28 to have also a function of a final beam extraction window eliminates the need to attach the beam extraction window 23b anew, thereby reducing time for the switching between the broad irradiation and the scanning irradiation.
As described above, the irradiation nozzle 20 thus allows the particle beam irradiation to be switched between the scanning irradiation and the broad irradiation, as shown in
An irradiation apparatus capable of irradiation by switching between the broad irradiation and the scanning irradiation may be configured to have two irradiation lines: a first irradiation line having an irradiation nozzle for the broad irradiation and a second irradiation line having an irradiation nozzle for the scanning irradiation. Such an irradiation apparatus has already been disclosed in Patent Document 1.
Here, the first irradiation nozzle 210 is mounted with broad irradiation use parts, and the second irradiation nozzle 220 is mounted with scanning irradiation use parts. The broad irradiation is performed when the delivery line is switched to the first irradiation line, and the scanning irradiation is performed when the delivery line is switched to the second irradiation line. When the irradiation line is switched to the first irradiation line or to the second irradiation line, no rotation of the gantry allows the broad irradiation and the scanning irradiation to be performed respectively from directions different by 180 degrees. In addition, when the irradiation line is switched, for example, from the first irradiation line to the second irradiation line, rotation of the gantry by 180 degrees allows the broad irradiation and the scanning irradiation to be performed from the same direction.
As described above, the broad irradiation and the scanning irradiation can be performed for one and the same patient, using an irradiation nozzle such as the irradiation nozzle 20, shown in FIGS. 2 and 3, configured to be able to perform the broad irradiation and the scanning irradiation by switching parts provided to the irradiation nozzle, or the irradiation apparatus 200, shown in
While a dose monitor is provided in the irradiation nozzle to measure an irradiation dose of the particle beam during both scanning irradiation and broad irradiation, the way of controlling the dose is different between the scanning irradiation and the broad irradiation. The scanning irradiation is performed by controlling particle beam irradiation doses imparted to respective irradiation points in a scanning irradiation region while shifting the particle beam, as with, for example, a spot scanning irradiation method in which irradiation is performed by repeating stop and shift of the particle beam. While the broad irradiation is performed such as using the wobbler method in which the particle beam is spread by being scanned in a circular pattern or using a scattering method in which the particle beam is spread by being not shifted but scattered with a scatterer, either broad irradiation method does not control irradiation doses imparted to respective irradiation points in a broad irradiation region but controls the overall irradiation dose imparted to the entire broad irradiation region.
Next, a method of formulating a treatment plan is described, in which a target irradiation dose distribution is formed by imparting the sum of a broad irradiation dose and a scanning irradiation dose to the same irradiation object, i.e., a diseased site using the irradiation apparatus capable of switching between the scanning irradiation and the broad irradiation described above.
For example, the broad irradiation region 2 is set so as to be inscribed in the irradiation region 1. Briefly explaining, since this setting leaves in the irradiation region 1 an unirradiated region other than the broad irradiation region 2, the region needs to be set as the scanning irradiation region 3 to be irradiated by the scanning irradiation. More strictly speaking, in the region to which an irradiation dose is imparted by the broad irradiation, there partially exist portions whose doses are unreached to their respective target irradiation doses. In any case, a target irradiation dose distribution Ds(x, y, z) to be formed by the scanning irradiation can be calculated by subtracting a target irradiation dose distribution Db formed in the broad irradiation region by the broad irradiation from the target irradiation dose distribution D in the entire irradiation region, as expressed by the following Eq. (1):
D
s(x,y,z)=D(x,y,z)−Db(x,y,z) (1).
As a result, the irradiation region 1 can be divided into (1) a region irradiated only by the broad irradiation, (2) regions irradiated only by the scanning irradiation, and (3) regions (indicated by irradiation regions 4 shown in
Formulation of a treatment plan based on a conventional scanning irradiation needs to solve an optimization problem to determine an irradiation angle, an irradiation dose for each irradiation point, further a scanning path (scanning trajectory) connecting each irradiation point, and the like to form the target irradiation dose distribution D in the entire irradiation region 1. A treatment plan formulated by the treatment planning apparatus according to the present invention only needs to solve an optimization problem for the target scanning irradiation dose distribution Ds calculated from the Eq. (1), thus reducing calculation time for the optimization. In addition, a conventional optimization technique (calculation algorism) can be used, as a matter of course, to form the target scanning irradiation dose distribution Ds.
As described before, the irradiation dose imparted by the broad irradiation is a so-called “fixed irradiation dose”, and shortages of doses to be imparted by the scanning irradiation is “unfixed irradiation doses”. Accordingly, the optimization is, in principle, to approximate the unfixed irradiation doses to the target irradiation doses as close as possible.
When starting treatment for a patient, i.e., starting the particle beam irradiation, the irradiation nozzle is, for example, first mounted with the parts for the broad irradiation, and then the respective devices are operated in accordance with their broad irradiation parameters sent from the overall device management apparatus 14, so that the broad irradiation dose distribution Db is formed in the diseased site. After that, the irradiation nozzle is mounted with the parts for the scanning irradiation, and then the respective devices are operated in accordance with their scanning irradiation parameters sent from the overall device management apparatus 14, so that the scanning irradiation dose distribution Ds is formed in the diseased site. By both irradiations, the irradiation dose distribution D=Db+Ds is imparted to the diseased site. Since the irradiation dose distribution only needs to satisfy D=Db+Ds, it is no matter which the broad irradiation or the scanning irradiation is performed first in order.
As described above, the treatment planning apparatus 10 formulates a treatment plan for both broad irradiation and scanning irradiation to form a target irradiation dose distribution in a diseased site, and a particle beam irradiation is performed in accordance with the treatment plan. This brings about the following effects. The broad irradiation is a conventionally used irradiation method and has a merit in that there are many actual results in clinical practice; however, since broad irradiation regions are difficult to conform respectively to various shape diseased sites, a bolus is necessary for a broad irradiation region to conform to a diseased site shape on a patient-by-patient basis. In contrast to that, the scanning irradiation is capable of forming various irradiation regions and various irradiation dose distributions by controlling the parameters for the respective devices; however, optimization calculation for the scanning irradiation takes time in formulating a treatment plan. According to Embodiment 1 of the present invention, the broad irradiation imparts an irradiation dose to a large portion of an irradiation region and the scanning irradiation imparts irradiation doses to irradiation points in the remaining portions, which are mainly peripheral portions. This reduces the scanning irradiation regions thereby reducing time to formulate a treatment plan, and brings about an effect of being able to imparting irradiation doses to a diseased site having various shapes with high accuracy. Furthermore, the scanning irradiation can be performed in a short time, thus facilitating performing the scanning irradiation, for example, with so-called respiration synchronizing control, i.e., during a less movement phase of a diseased site in the respiration cycles. Performing the scanning irradiation with the respiration synchronizing control brings about an effect of being able to impart irradiation doses with higher accuracy.
In Embodiment 1, no bolus is used in the broad irradiation. A bolus is usually fabricated for the range of the particle beam to conform to the shape of a diseased site, i.e., fabricated to adjust the energy distribution of the particle beam to the range conforming to a lower portion shape (distal shape) of a diseased site. A broad irradiation using a bolus allows for forming an irradiation dose distribution in conformity to a distal shape of a diseased site. However, irradiation from one direction is difficult to form an irradiation dose distribution in conformity to both distal and proximal shapes of a diseased site, i.e., the shape of the entire diseased site. Hence, a target irradiation dose distribution has been formed in the entire diseased site by a so-called multi-port irradiation such that irradiations are performed from, for example, an upper direction using a bolus for the distal shape and from the lower direction using a bolus for the proximal shape.
In Embodiment 2, the broad irradiation is performed using a bolus, for example, a bolus for distal shape that forms an irradiation dose distribution in an irradiation region whose shape is the same as a distal shape of only a portion of an irradiation object, and the scanning irradiation is performed to impart irradiation doses to a portion to which the broad irradiation cannot impart an irradiation dose. A schematic illustration of the irradiations is shown in
In this case, it is sufficient to form an irradiation dose distribution only in the region proximal to the incident side of the particle beam by the scanning irradiation, thus allowing a treatment plan for the scanning irradiation to be formulated in a shorter time than Embodiment 1. Moreover, each irradiation of the scanning irradiation can be performed in a short time, thus facilitating performing the scanning irradiation, for example, in synchronism with respiration. Performing the scanning irradiation in synchronism with respiration brings about an effect of being able to impart irradiation doses with higher accuracy.
In Embodiment 2, the broad irradiation is performed using a bolus conforming to a distal shape of a portion of a diseased site. Conventionally, a bolus has been fabricated, each time on a patient-by-patient basis, as a patient-specific bolus conforming to the diseased site of a patient. Embodiment 3 is characterized in that the broad irradiation is performed not using a patient-specific bolus but using a bolus that is selected to approximate to a distal shape of a diseased site among a plurality of device-specific different shape boluses prepared beforehand. The plurality of different shaped boluses is referred here to as versatile boluses.
This reduces the scanning irradiation region 3 compared to Embodiment 1 that performs the broad irradiation without using a bolus, thus allowing a treatment plan for the scanning irradiation to be formulated in a further shorter time than Embodiment 1. Moreover, each irradiation of the scanning irradiation can be performed in a short time, thus facilitating performing the scanning irradiation, for example, in synchronism with respiration. Performing the scanning irradiation in synchronism with respiration brings about an effect of being able to impart an irradiation dose with higher accuracy.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/061085 | 4/9/2015 | WO | 00 |
