CN103394166B - Particle-beam therapeutic apparatus and particle-beam therapeutic method - Google Patents
Particle-beam therapeutic apparatus and particle-beam therapeutic method Download PDFInfo
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Abstract
The present invention discloses a kind of particle-beam therapeutic apparatus and particle-beam therapeutic method, when the presumptive area of target volume is divided into multilamellar to irradiate particle ray along the depth direction of particle ray, performs dose modification respectively to every one deck of each layer after segmentation.
Description
The application is the applying date is " on May 13rd, 2008 ", application number is " 200880129227.9 ", is entitled as the divisional application of " particle-beam therapeutic apparatus and particle-beam therapeutic method ".
Technical field
The present invention relates to for irradiating particle ray with the particle-beam therapeutic apparatus of Therapeutic cancer etc. and particle-beam therapeutic method.
Background technology
In the known particle-beam exposure method being called as stacked irradiation, scanning irradiation, the direction of beam travel segmentation of target volume (being also only called target) along particle ray is irradiated.
In order to obtain required particle ray distribution at depth direction, need the dosage weighting of each layer of target volume to be set to desirable value.
Therefore, although perform the step of dose modification at pre-irradiation, in the prior art, SOBP (SpreadOutBraggPeak: expand bragg peak) the center this point in the depth direction distribution of biological dose carries out dose modification.
In addition, such as, in following patent documentation 1 (Japanese Patent Laid-Open 2004-358237 publication), show " Target Segmentation being become multilamellar; determine the irradiation dose of every layer ", in patent documentation 2 (Japanese Patent Laid-Open 10-314323 publication), show " Target Segmentation is become multilamellar, determines to make the uniform mode of irradiation dose of every one deck of each layer ".
In addition, in following non-patent literature 1, show " by the weight design of the small-sized ridged filter used in stacked irradiation is become Gauss distribution, thus the impact of site error between relief layer ".
In addition, about " SOBP " and " small-sized ridged filter ", after can set forth in the explanation of working of an invention mode.
Patent documentation 1: Japanese Patent Laid-Open 2004-358237 publication
Patent documentation 2: Japanese Patent Laid-Open 10-314323 publication
Non-patent literature 1:Ridgefilterdesignandoptimizationforthebroad-beamthree-dimensionalirradiationsystemforheavy-ionradiationtherapy. (design and optimization for ridged filter in the broad-beam condition 3-dimensional irradiation system of heavy particle radiotherapy) BarbaraSchaffner, TatsuakiKanai, YasuyukiFutami, andMunefumiShimbo, Med.Phys.Volume27 (4), April2000, pp716-724.
Summary of the invention
In stacked irradiation up to now, as when existing expansion is irradiated, carry out dose modification in the representative point this point at SOBP center.
On the other hand, in stacked irradiation, because equipment setting changes according to layer, therefore, nature can be expected being provided with dose modifying factor accordingly with each layer, and there are the following problems: if a bit correct at SOBP center, then insensitive to the correction coefficient of shallow-layer.
When correction coefficient being solved to each layer in actual measurement, due to the depth direction of Bragg curve change sharply, therefore, the site error more slightly arranging the position of radiacmeter will become the reason making the generation of dose modification value compared with big error, thus is difficult to carry out dose modification to each layer accurately at short notice.
In addition, " Bragg curve " represents by charged particle rays (such as, proton radiation, carbon ray etc.) till charged particle arrives, give the curve of the relative dosage in irradiated body when being irradiated on irradiated body, it has peak near most deep.
As the main cause of the site error of depth direction, have the mechanical precision of the dosage distribution measuring device used during dose modification not, the effective thickness error etc. of the material such as error that the shape of radiacmeter that uses of timing is not two dimensional surface and causes or the dose monitor in beamline.
Due to these main causes, even if originally intend to correct on the summit of Bragg curve, but also may correct the position beyond summit in reality, be difficult to the precision reaching correction coefficient.
The present invention completes to solve the problem, and its object is to provide a kind of particle-beam therapeutic apparatus of precision of dose modification when can carry out the dose modification in stacked irradiation to every one deck of each layer and can improve stacked irradiation.
The presumptive area of target volume is divided into multilamellar to irradiate described particle ray along the direct of travel of particle ray by particle-beam therapeutic apparatus involved in the present invention, comprise: particle-beam exposure portion, this particle-beam exposure portion has the ridged filter that the dosage of described particle ray is carried out the dose monitor that monitors as count value and expanded by the bragg peak in each layer of described multilamellar, and forms irradiated region in described presumptive area, and treatment control part, this treatment control part controls the action in described particle-beam exposure portion, make when being set to α i by utilizing dose modification to the correction coefficient that every one deck of each layer obtains, if described count value reaches the value represented by formula (A) below, then stop the irradiation to the described particle ray of described i-th layer, be transferred to the irradiation from described i-th layer of different layer, wherein, in this dose modification, by physical dosage when i-th in described multilamellar layer being irradiated to described particle ray divided by described count value, bragg peak after being expanded by described ridged filter has flat site at least partially at physical dosage PDD curve, described flat site is formed in the mode that the width of described flat site is wider than the positional precision that can reach during described dose modification, and described correction coefficient utilizes the described dose modification carried out at described flat site and the correction coefficient obtained,
K0dMINIPEAK_PHYS (z0) Wi/ α i ... formula (A)
Wherein,
K0: for obtaining the normalisation coefft of prescribed dose,
DMINIPEAK_PHYS (z0): the value of the physical dosage PDD hump of the bragg peak after being expanded by described ridged filter in the darkest layer of the direct of travel of described particle ray,
Z0: the degree of depth of the PDD hump of the bragg peak after being expanded by described ridged filter,
Wi: to the dosage weighting of i-th in described multilamellar layer.
According to the present invention, due to the correction accuracy of shallow-layer can also be guaranteed, and the deviation of the correction coefficient of each layer being confirmed, therefore, even if when breaking down, also can systematically understand.In addition, significantly can reduce dose modification desired position precision, and the dose modification of every one deck of each layer in stacked irradiation can be performed at short notice accurately.
Thus, according to the present invention, the dose modification in stacked irradiation can be carried out to every one deck of each layer, the precision of dose modification during stacked irradiation can be improved.
Accompanying drawing explanation
Fig. 1 is the structure chart representing particle-beam therapeutic apparatus.
Fig. 2 represents state diagram when irradiating particle ray from particle-beam exposure portion to patient.
Fig. 3 represents the Bragg curve when proton radiation and carbon ray.
Fig. 4 represents the figure of the expansion bragg peak of carbon ray.
Fig. 5 is the figure of the principle for illustration of ridged filter.
Fig. 6 is the structure chart representing ridged filter erecting bed.
Fig. 7 is the structure chart of the correcting unit representing particle-beam exposure portion and radiacmeter.
Fig. 8 represents the figure of the small peak (physical dosage) of carbon ray.
Fig. 9 is the figure of the position representing check point.
Figure 10 is the figure of the small peak (biological dose) representing carbon ray.
Figure 11 is the figure of the weight of the expansion bragg peak representing carbon ray.
Figure 12 is the design example figure of the small-sized ridged filter represented involved by embodiment 3.
Figure 13 is the design example figure of the small-sized ridged filter represented involved by embodiment 3.
Figure 14 is the design example figure of the small-sized ridged filter represented involved by embodiment 3.
Label declaration
1 horizontal irradiated region forming portion 2 dose monitor
3 depth direction irradiated region forming portion 4 ridged filters
5 data processing division 21 patients
22 treatment table 61 ridged filter erecting beds
62 passing hole (by mouth) 70 radiacmeter correcting unit
71 Water ball (waterphantom) 72 radiacmeter
73 radiacmeter driving device 74 radiacmeter circuit and data processing equipments
Control part is treated in 101 treatment plan portions 102
103 particle ray generating unit 104 particle ray delivery section
105 location division, particle-beam exposure portions 106
Detailed description of the invention
Embodiment 1
Based on accompanying drawing, an embodiment of the invention example is described.
Fig. 1 is the structure chart representing particle-beam therapeutic apparatus.
As shown in Figure 1, particle-beam therapeutic apparatus is made up for the treatment of plan portion 101, treatment control part 102, particle ray generating unit 103, particle ray delivery section 104, particle-beam exposure portion 105 and location division 106 etc.
Particle-beam exposure portion 105 has the function for forming suitable irradiated region when irradiating particle ray to patient, and treatment plan portion 101 has the function in order to irradiate required dose distribution, the parameter of each equipment in particle-beam exposure portion 105 being defined as appropriate value.Location division 106 has and is fixed patient, positions target (also referred to as target volume) and the function of confirmation etc.
Treatment control part 102, based on the instruction from treatment plan portion 101, controls the action of particle ray generating unit 103, particle ray delivery section 104, particle-beam exposure portion 105 and location division 106.
Fig. 2 represents state diagram when irradiating particle ray from particle-beam exposure portion to patient.
As shown in Figure 2, particle-beam exposure portion 105 by the transverse direction be mainly used in the irradiated region of particle ray (namely, the face vertical with direction of beam travel) control the horizontal irradiated region forming portion 1 of beam, the dosage of particle ray is monitored to the dose monitor 2 of (counting), at depth direction (namely, direction of beam travel) control the depth direction irradiated region forming portion 3 of beam, the ridged filter (ridgefilter) 4 formed in depth direction irradiated region forming portion 3, and to formations such as the data processing divisions 5 that the dose data that dose monitor 2 counts processes.In addition, in fig. 2,21 is patients, and 22 is treatment table.
Next, illustrate in the control of depth direction to beam (namely, particle ray bundle).
When irradiating the beam of single energy, the dose distribution of the depth direction in patient 21 body is called PDD (PercentageDepthDose: percentage depth dose).
If by particle-beam exposure on uniform medium, then particle ray stops at a certain degree of depth according to energy when inciding in medium, the degree of depth is at this moment called range.
PDD till from dielectric surface to range presents the shape with the summit (peak) being called Bragg curve, and the part near the maximum of curve (i.e. Bragg curve) is called bragg peak.
Fig. 3 represents the Bragg curve when proton radiation and carbon ray (heavy particle ray).
In addition, in figure 3, transverse axis is the degree of depth (cm) from body surface, and the longitudinal axis is relative absorbance dosage (%).
The shape of Bragg curve is different because of the nucleic of the particle ray of irradiation, and the situation of proton radiation is compared with carbon ray, and bragg peak is wider.
In addition, carbon core can produce nuclear fission, and can not produce nuclear fission in proton radiation, therefore, does not have afterbody (namely, the afterbody of nuclear reaction) in the dose distribution of proton radiation.
Below, although set forth the situation that particle ray is carbon ray, the present invention is applicable to proton radiation, other nucleic too.
Fig. 4 represents the figure of the expansion bragg peak of carbon ray.
Namely expand in irradiation at known irradiation technique, after utilization, be called that the device of ridged filter is to expand the width of bragg peak, formed as shown in FIG. 4 be called that the identical region of dosage expanding bragg peak (SOBP) is irradiated.
The width of SOBP and the corresponding formation of thickness of the depth direction of target (target volume).
Next, the difference of the biological dose shown in key diagram 4 and physical dosage.
Dosage is defined as physical dosage and biological dosage (also referred to as effective dose) these two kinds.
Physical dosage is the energy of certain part giving target, and unit is gray(Gy) (gray, Gy).
On the other hand, biological dose is the value that the consideration of physically based deformation dosage is determined the biological impact of cell, and unit is gray(Gy) equivalent (grayequivalent, GyE).
Biological dose is such as by defining with this condition of dosage making the survival rate of cell become 10% such exposure dose equivalence produced by Co 60.
In particle-beam therapeutic, prescribed dose is defined by biological dose.
The object of SOBP makes radiation response even, distributed define by biological dose.
On the other hand, because the radiacmeter used when dose modification cannot carry out the measurement of biology effect, therefore, dose modification uses physical dosage to carry out.
Obtain biological dose from physical dosage can utilize known method to try to achieve, omit it at this and record.
The formation of SOBP make use of the device being called ridged filter.
Fig. 5 is the figure of the principle for illustration of ridged filter.
Ridged filter has the Known Species such as bar ridged filter (barridgefilter) or modulation wheel (modulationwheel) as shown in Figure 5, at this, they is referred to as ridged filter.
Fig. 5 is the concept map for illustration of ridged filter, and in reality, ridge is more.Ridged filter 4 is made up of the region with different-thickness and width.
Particle ray by different thickness, has different ranges according to the position difference passed through thus.
Such as, if the particle ray that water equivalent range is 30cm is the part of 5cm by the water-equivalent thickness of ridged filter, then the range of this particle ray is about 25cm according to water equivalent.
Conveniently make, in practice, the thickness of ridged filter 4 is designed to step-like, in units of step, controls the ratio of the population of water-equivalent thickness range.
Further, this ratio is called weight.
Such as, if the thickness widening ridged filter 4 is the width of 5cm part according to water equivalent, then the ratio with the particle ray being about the range of 25cm according to water equivalent can be increased.
By suitably selecting weight based on this known method, thus the ridged filter that the SOBP that can design the peak identical with having biological dose is corresponding.
Fig. 6 is the structure chart representing ridged filter erecting bed, and ridged filter 4 is arranged on ridged filter erecting bed 61 as shown in Figure 6.Adopt following structure: on this ridged filter erecting bed (ridged filter replacement platform) 61, common ridged filter and multiple small-sized ridged filter etc. can be installed simultaneously, and change easily.
In addition, if be arranged through hole (by mouth) 62 in a certain position of this ridged erecting bed 61 in advance, then unmodulated particle ray can be irradiated.
So far, be called that the irradiation technique expanding irradiation is recorded to existing, but as known irradiation technique unlike this, have the method (with reference to above-mentioned document 1) being called stacked irradiation.
In the method, target volume is divided into the region of depth direction, namely there is the layer of one fixed width, and irradiate these regions successively respectively.Now, the width of layer is without the need to being fixing.
As the method for the degree of depth of adjustment layer, have by changing method that the energy being positioned at the accelerator of particle ray generating unit 103 carries out adjusting and by inserting the method these two kinds that the certain thickness plate being called the requirement of range shift unit being positioned at particle-beam exposure portion 105 carries out adjusting.
When irradiating particle ray, although also can by Bragg curve same as before, irradiations of staggering with a certain step unit, if the width of bragg peak is narrower, then step width attenuates, and number of steps increase, becomes numerous and diverse.
Therefore, adopt and have a mind to expand bragg peak and widen step width a little, carry out the method for irradiating thus.As step width, use more than 2mm ~ about 10mm.
Now, the bragg peak after expanding is called small peak, the device for the formation of this small peak is called small-sized ridged filter.
At present, propose and used small-sized ridged filter in stacked irradiation, or used the small peak with smooth weight, or used the small peak with the weight of Gauss distribution.
But, in existing motion, " smooth ", " Gauss distribution " are all the discussion to weighting function itself, and do not mention PDD (PercentageDepthDose: the percentage depth dose) shape of physical dosage, also do not mention and make the easy this purpose of dose modification transfiguration.
Thus, in existing motion, even if the weight of small-sized ridged filter is smooth, the physical dosage distribution of small peak also can not be smooth, needs correctly to determine which part in small peak corrects.
In addition, there is dose modification value produces significant error problem because of the micro-locality error of depth direction.
Next, the dose modification method in stacked irradiation is described.
In stacked irradiation, the weight of the relative dosage of each layer, i.e. each layer needs to irradiate according to the output of the Rapid Dose Calculation performed in treatment plan portion 101 in advance.If like this, then required PDD cannot do not obtained.
Such management is carried out: based on the count value of dose monitor 2 being arranged on particle-beam exposure portion 105, the dosage giving each layer is carried out according to plan in particle-beam therapeutic apparatus.
That is, when irradiating certain one deck, the dosage giving this layer being converted to the counting of dose monitor 2, temporarily stopping when this count value reaches desirable value irradiating, counting being reset, is transferred to the irradiation of lower one deck.
But the count value due to dose monitor 2 is arbitrary unit, therefore, generally direct managing physical dosage or biological dose is come without count value.
One of its reason is: when the device setting changing particle-beam exposure portion 105 according to illuminate condition, cannot ensure that count value and physical dosage exist fixed relationship all the time.
Replace, utilize device as shown in Figure 7, under required irradiated region condition, to the count value of radiacmeter 72 correction dose monitor 2.
In addition, Fig. 7 is the structure chart of the correcting unit representing particle-beam exposure portion 105 and radiacmeter.
As shown in Figure 7, radiacmeter correcting unit 70 is made up of Water ball (namely, dosimetry tank) 71, radiacmeter 72, radiacmeter driving device 73, radiacmeter circuit and data processing equipment 74 and support 75.
For radiacmeter 72, use the radiacmeter ensureing to correct, correct operation is carried out to each patient (each treatment plan).
The count value that the value can measured in dose modification has the physical dosage measured by radiacmeter 72, dose monitor 2 is measured, the ratio of these two numerical value is correction coefficient, i.e. Gy/count (the every count value of gray(Gy)).
In radiacmeter 72, only measure physical dosage owing to not measuring biological dose, therefore, physical dosage is corrected.
Although prescribed dose biological dose defines, but as long as the PDD owing to precomputing the physical dosage suitable with it, dose modification and the management for the treatment of exposure dose just can with the PDD of physical dosage for object perform, therefore, when dose modification without the need to considering biological dose.
Then, imagine concrete example to be illustrated.
Such as, if carried out stacked irradiation to the spherical object that diameter is 75mm.
If assuming that the step of layer is 2.5mm, then want the 75mm in depth of shine direction, need 29 layers.
In existing stacked irradiation, dose modification a bit, has been carried out in the center of the overall SOBP formed when irradiating all 29 layers.
This is the content of the design based on existing expansion irradiation.
If represent by mathematical expression, then provided by following formula at the physical dosage at SOBP center.
DSOBP_PHYS(zC)＝K0·∑dMINIPEAK_PHYS(zC+zi)·Wi
In addition, in above formula, " DSOBP_PHYS (zC) " is the function representing that SOBP distributes, and is the physical dosage represented with gray(Gy).
" dMINIPEAK_PHYS " is the physical dosage PDD curve of small peak.
ZC represents the center of SOBP, and zi represents the shift amount of i-th layer.Σ represent all layers, namely to i=1,29 and.
In addition, Wi is set to and meets ∑ Wi=1 and the weight of carrying out standardized each layer.
K0 is normalisation coefft, and its value is defined as being consistent from the prescribed dose irradiated the once physical dosage obtained that converts with utilizing DSOBP_PHYS (zC).
In above formula, if the PDD curve of small peak is only shifted according to the layer irradiated, curve shape is constant, represents with by the formula after dMINIPEAK_PHYS (zC+zi) function superposition.
Even if in the invalid situation of this supposition, as long as to function mark subscript i, conclusion would not change.
Such as, with the prescribed dose at SOBP center for 5GyE and when having outputed prescription to irradiation, if the physical dosage DSOBP_PHYS (zC) at SOBP center is such as 2.05Gy, then correction coefficient alpha 0 can be write as following formula.
DSOBP_PHYS(zC)＝
α0·K0·∑{dMINIPEAK_PHYS(zC+zi)·Wi/α0}＝2.05Gy
Now, " K0 ∑ { dMINIPEAK_PHYS (zC+zi) Wi/ α 0} " is equivalent to the count value measured by dose monitor, and the unit of α 0 is the unit Gy/count of the correction coefficient determined in dose modification.
Although to herein illustrating existing bearing calibration, in the present invention, carry out the correction of each layer respectively.
Now, can be described by following formula at the physical dosage of any degree of depth z.
DSOBP_PHYS(z)＝
K0·∑{αi·dMINIPEAK_PHYS(z+zi)·Wi/αi}
At this, definition:
Di(z)＝K0·αi·dMINIPEAK_PHYS(z+zi)·Wi/αi。
If the degree of depth on the PDD summit of the darkest layer is defined as z0, then in each layer displacement after peak the degree of depth by
zpeak＝z0－zi
Provide.
According to the present invention, when zpeak corrects, correction coefficient alpha i by
αi＝Di(z0－zi)/{K0·dMINIPEAK_PHYS(z0)·Wi/αi}
Provide, K0dMINIPEAK_PHYS (z0) Wi/ α i is equivalent to the count value measured by dose monitor.
Like this, in existing bearing calibration, correction coefficient and Gy/count only define one, and on the other hand, in bearing calibration involved in the present invention, the quantity of correction coefficient equals the number of plies, and this point is different.In the conventional method, owing to only a bit determining correction coefficient at SOBP center, therefore, the probability that the Gy/count of every layer is different is not considered.
In the conventional method, each layer is made contributions with different weights to a corrected value.
This weight and the physical dosage contributed relative to each layer of zC
K0·dSOBP_PHYS(zC+zi)·Wi
Be directly proportional.
For the layer that dSOBP_PHYS (zC+zi) or Wi is less, correction coefficient is to DSOBP_PHYS (zC) dull.
Discuss below this considers.
I.e. " layer less due to Wi is less for the contribution of dosage, therefore, to those layers without the need to correctly determining correction coefficient ".
But this is contrary with the basic conception based on actual measurement determination correction coefficient.
If to shallow-layer without the need to determining correction coefficient separately, so, following prerequisite should be had: even if when illuminate condition changes, the value of Wi does not also depend on actual measurement, and calculates by means of only calculating, and just can obtain enough reliabilities.Particularly, for the layer more shallow than zC, participate in correcting by means of only the afterbody produced because of nuclear fission.
That is, in existing bearing calibration, for the situation not having the PDD of the afterbody of nuclear fission that proton radiation is such, the layer more shallow than zC does not all participate in correcting.And, even contribute less layer at zC, sometimes also can increase in the contribution of other degree of depth.
Therefore, the position that the correction of each layer that the present invention is such is desirably in the peak of each layer is carried out, can the precision that corrects of increasing dose, and obtains the understanding of system.
As mentioned above, the invention is characterized in, each layer is corrected respectively, but due to narrower at the width of actual (particularly the situation of carbon ray) middle bragg peak, therefore, be sometimes difficult to correct on the summit of the bragg peak of each layer.
Thus, as another feature of the present invention, as shown in Figure 8, the physical dosage distribution of the small-sized ridged filter used when carrying out stacked irradiation forms maximum and smooth region.
In addition, Fig. 8 represents the figure of the small peak (physical dosage) of carbon ray.
It is important in this that, in physical dosage distribution, form the flat site of PDD.
The width of this PDD par is orientated as the width of small peak.The width of small peak needs to be greater than the positional precision that can reach when dose modification.Although the width of small peak and the step width of layer also can be identical, do not need identical.
The check point of each layer is schematically shown at Fig. 9.
In fig .9, in order to easily observe the curve of small peak, draw spaced apart for curve, but in practice, the flat of small peak is adjacent or overlap.
The design of this small-sized ridged filter can use known maneuver.
Such as, the shape of physical dosage PDD can be measured in advance, the curve after making PDD curve shift according to the thickness of ridged filter is added with a certain weight, best weight is set to form required flat site.
In existing bearing calibration, correct after each layer being needed to the depth location of correct grasp bragg peak, therefore, at timing, correct after needing cautiously Bragg curve to be mapped to depth direction.
Relative to the precision required by reality, the mechanical precision of dose modification measuring system is inadequate sometimes.
Or, namely enablely obtaining enough mechanical precisions, also needing time and skill to obtain high accuracy at every turn.
Thus, in the prior art, it is unpractical for using bragg peak to carry out correction respectively to each layer.Such as, in the bragg peak of carbon ray, even if depth direction only has the site error of only 1mm, physical dosage also can change more than twice, but, if forming width is the small peak of 2mm, then significantly can relax allowable error.
As mentioned above, if according to the present embodiment, even if when then carrying out dose modification to every one deck of each layer in stacked irradiation, also can implement with high accuracy at short notice.
Because the PDD of each layer that dose modification uses has the smooth small peak of physical dosage, so, as long as correct the setting position of radiacmeter that uses in small peak, which position can, therefore, significantly can reduce position accuracy demand during measurement.
Next, set forth the above-mentioned small-sized ridged filter of use and carry out treatment irradiation.
If form smooth summit in physical dosage distribution, then the summit of biological dose distribution is uneven, forms the shape shown in Figure 10.
But, by making the width of each layer fully narrow and being overlapped by these layers, thus, in biological dose, also can SOBP be formed.
Such as, also can be that the small peak of 5mm overlaps with the step width of 2.5mm by width.
Although in the darker side of small peak, dosage sharply declines, if become to have a mind to make its rust by small-sized ridged design for filtration elements, then flatness can be improved.
On the other hand, darker side when forming SOBP generally expects that biological dose as far as possible sharply declines.
If investigate the weight for the formation of each layer of uniform SOBP, then can know, shown in Figure 11, near the bottommost layer of dose distribution (the irregular region of the weight in figure), weight sharply changes, but, be called flat-top (plateau) forefoot area (the stable region of the weight in figure) in, weight can not change substantially.(non-patent literature 1 with reference to disclosing above)
Therefore, by the small-sized ridged filter these two kinds being used for making the dose distribution of bottommost layer to become the special small-sized ridged filter of bottommost layer sharply and to be applicable to the more smooth region (part for flat-top) of weight is before this used, thus the flatness of SOBP can be improved and guarantee the abruptness of PDD.
So far, although set forth premised on the uniformity guaranteeing SOBP, except smooth SOBP, sometimes also expect to make the dose distribution that the dosage of SOBP core is higher.
Sometimes the higher cancerous cell of radiation resistant is there is because of tumor at central part, in this case, the irradiation that the dosage that is different, that make core of desired amount distribution is sometimes higher.
In this case, bearing calibration involved in the present invention and treatment illuminating method also can be tackled.
Although above, stacked irradiation is set forth, to irradiate narrow beam, be called as mode that scanning irradiates and also can fit and use the same method.
In scanning is irradiated, on the stacked basis of depth direction, narrow beam (namely, particle ray) is also made laterally to overlap.
Even if in this case, also by using narrow beam to form small peak at depth direction, thus dose modification is easily carried out.
Now, as the device forming small peak, be suitable for modulation wheel.This is because narrow beam is difficult to collide equably on bar ridged filter.
When using bar ridged filter, need the spacing making ridge narrower.
Because the ridge of filter can be thinner, therefore, be easier to the spacing of ridge to make narrow.
Or, also can consider bar ridged filter is vibrated, control beam and collide equably on bar ridged filter.
Due to the same with the situation of stacked irradiation, also by having a mind to the dosage of side darker for small peak to slow down improve flatness, therefore, by the ridged filter that uses bottommost layer special and the special ridged filter these two kinds of flat-top simultaneously, the abruptness of PDD need not be sacrificed, also can obtain flatness.
As described above, particle-beam therapeutic apparatus involved by present embodiment, when the presumptive area of target volume is divided into multilamellar to irradiate particle ray along the depth direction of particle ray, performs dose modification respectively to every one deck of each layer after segmentation.
In addition, particle-beam therapeutic apparatus involved by present embodiment is when the presumptive area of target volume is divided into multilamellar to irradiate particle ray along the depth direction of particle ray, every one deck of each layer after segmentation is performed respectively to the particle-beam therapeutic apparatus of dose modification, physical dosage for depth direction distributes, described each layer width at least partially, small-sized ridged filter is used to form the certain region of dosage, to carry out dose modification.
In addition, particle-beam therapeutic apparatus involved by present embodiment is when the presumptive area of target volume is divided into multilamellar to irradiate particle ray along the depth direction of particle ray, every one deck of each layer after segmentation is performed respectively to the particle-beam therapeutic apparatus of dose modification, physical dosage for depth direction distributes, described each layer width at least partially, use small-sized ridged filter to form the certain region of dosage, these each layers are overlapped and irradiates described target volume.
Embodiment 2
Next, embodiment 2 is recorded.
Although set forth the example all corrected each layer in embodiment 1, imposing a condition of each equipment of particle-beam therapeutic apparatus can not produce large change to every layer, but one deck only changes a bit.
Therefore, along with the accumulation of radiation response, no longer need each correction all performing each layer of setting forth in embodiment 1 at all layers.
Now can consider measurement point spaced apart.
In addition, as mentioned above, the check point shown in Fig. 9 present spaced apart after state.
For layer spaced apart, the corrected value former state from this layer of nearest check point this point can be considered to quote, or the multiple correction execution points near using carry out interpolation to corrected value.
As interpolating method, several known method such as linear fitting or Multinomial fitting can be considered.
When installing corrective system, following function can be embedded in advance in the control system of corrective system: user can select to be use all layer as check point, or spaced apartly to correct.
In addition, when spaced apart, user can be made can to select position spaced apart, interpolation algorithm etc.
According to present embodiment, then can shorten the time required for correction further.
As described above, the feature of the particle-beam therapeutic apparatus involved by present embodiment is, only performs dosage measurement to a part of layer selected from the multilamellar after segmentation.
Embodiment 3
Next, embodiment 3 is recorded.
Figure 12 ~ Figure 14 is the figure of the design example for illustration of the small-sized ridged filter involved by present embodiment.
In fig. 12, the physical dosage be provided with for carrying out dose modification to the part before bragg peak distributes smooth part.
What darker than it dashdotted partial design became to make bragg peak is weighted to Gauss distribution, thus, can carry out more reposefully with overlapping of the layer darker than this layer.
In fig. 13, the physical dosage be provided with for only carrying out dose modification to the core of bragg peak distributes smooth part.
What flat was designed so that bragg peak is weighted to Gauss distribution, thus, can carry out more reposefully with the layer darker than this layer and overlapping of more shallow layer.
In addition, in fig. 14, small design ridged filter, the physical dosage making to reproduce in most deep the dose distribution smooth with biological dose as shown in Figure 4 corresponding distributes (representing with dotted line), further, in physical dosage distribution, there is flat site.
In particle-beam therapeutic, because the weight of the dosage in most deep is higher, therefore, by use this especially for most deep dose distribution and carried out optimized small-sized ridged filter, even if for the Segmentation Number that the layer of depth direction is less, also correctly dose distribution can be reproduced.
Like this, in the present embodiment, can by small-sized ridged filter smooth for physical dosage and other dose distribution shape combined, thus, the coincidence transfiguration of layer can be made easy, or can the Segmentation Number of reduction layer.
Industrial practicality
The present invention is applicable to realize a kind of dose modification that can carry out every one deck of each layer in stacked irradiation, the particle-beam therapeutic apparatus of the precision of dose modification when improving stacked irradiation.
Claims (2)
1. a particle-beam therapeutic apparatus, the presumptive area of target volume is divided into multilamellar to irradiate described particle ray along the direct of travel of particle ray by this particle-beam therapeutic apparatus, it is characterized in that, comprising:
Particle-beam exposure portion, this particle-beam exposure portion has the ridged filter that the dosage of described particle ray is carried out the dose monitor that monitors as count value and expanded by the bragg peak in each layer of described multilamellar, and forms irradiated region in described presumptive area; And
Treatment control part, this treatment control part controls the action in described particle-beam exposure portion, make when being set to α i by utilizing dose modification to the correction coefficient that each layer obtains, if described count value reaches the value represented by formula (A) below, then stop the irradiation to the described particle ray of described i-th layer, be transferred to the irradiation from described i-th layer of different layer, wherein, in this dose modification, by physical dosage when i-th in described multilamellar layer being irradiated to described particle ray divided by described count value
Bragg peak after being expanded by described ridged filter has flat site at least partially at physical dosage PDD curve, described flat site is formed in the mode that the width of described flat site is larger than the positional precision that can reach during described dose modification, and described correction coefficient utilizes the described dose modification carried out at described flat site and the correction coefficient obtained
K0dMINIPEAK_PHYS (z0) Wi/ α i ... formula (A)
Wherein,
K0: for obtaining the normalisation coefft of prescribed dose,
DMINIPEAK_PHYS (z0): the value of the physical dosage PDD hump of the bragg peak after being expanded by described ridged filter in the darkest layer of the direct of travel of described particle ray,
Z0: the degree of depth of the PDD hump of the bragg peak after being expanded by described ridged filter,
Wi: to the dosage weighting of i-th in described multilamellar layer.
2. particle-beam therapeutic apparatus as claimed in claim 1, is characterized in that, described treatment control part, according to the output of the Rapid Dose Calculation performed by treatment plan portion in advance, sets the target dose irradiated each layer of described multilamellar.
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| WO2006005059A2 (en) * | 2004-06-30 | 2006-01-12 | Lexitek, Inc. | High resolution proton beam monitor |
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