JP2016050859A - Let independence peak detection method, dose distribution measurement method, and determination method of thermal fluorescent characteristic - Google Patents
Let independence peak detection method, dose distribution measurement method, and determination method of thermal fluorescent characteristic Download PDFInfo
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本発明は、高精度且つ簡易に行うことができる、ＬＥＴ非依存性ピーク検出法、線量分布測定法、並びに、熱蛍光特性の判定法に関するものである。 The present invention relates to a LET-independent peak detection method, a dose distribution measurement method, and a thermofluorescence property determination method that can be performed with high accuracy and simplicity.
ＬＥＴ（ＬＥＴ：Ｌｉｎｅａｒ Ｅｎｅｒｇｙ Ｔｒａｎｓｆｅｒ、線エネルギー付与）は、放射線、粒子線が媒質中を通過する際に媒質に与えるエネルギーであり、放射線、粒子線の種類（線質）の違いを表す指標として用いられている。
一般的に、熱蛍光の発光効率はＬＥＴに大きく依存することが知られている。
熱蛍光は簡易に検出・測定することができるため、医療現場をはじめとして幅広い分野で用いられており、その依存性を利用して、簡易にＬＥＴを算出する方法、粒子線の線量分布を測定する方法がこれまでに試みられている。例えば、非特許文献１では、ＢｅＯで観測される２つのグローピークの比からＬＥＴを算出する方法（ＨＴＲ法）が提案されている。
LET (LET: Linear Energy Transfer) is energy that is given to a medium when radiation and particle beams pass through the medium, and is used as an index representing the difference between the types of radiation and particle beams (line quality). It has been.
In general, it is known that the luminous efficiency of thermofluorescence greatly depends on LET.
Thermofluorescence can be easily detected and measured, so it is used in a wide range of fields including medical settings. By using its dependence, a method for easily calculating LET and measuring the dose distribution of particle beams There have been attempts to do so. For example, Non-Patent Document 1 proposes a method (HTR method) for calculating LET from the ratio of two glow peaks observed with BeO.
しかしながら、ＬＥＴに対して熱蛍光の発光効率が大きく変化するため、熱蛍光を用いた粒子線の線量分布の測定方法については、いまだ用いる熱蛍光体ごとに線種ごとのＬＥＴ依存性が十分に判明しておらず、実用性の点で十分ではなかった。
また、非特許文献１に記載のＨＴＲ法によって算出されるＬＥＴは誤差が大きいという問題があり、いまだ十分な実用性がなかった。
このため、高精度且つ簡易に、熱蛍光体のＬＥＴ依存性を理解し、粒子線の線量分布を判明させて、熱蛍光体の熱蛍光特性を判定できる方法が求められている。
したがって、本発明の目的は、高精度且つ簡易に、ＬＥＴ依存性を測定する方法（依存性のないピークを検出する方法）を確立して、粒子線の線量分布を判明させると共に熱蛍光体の熱蛍光特性を判定できる判定方法を提供することにある。
However, since the luminous efficiency of thermofluorescence changes greatly with respect to LET, the measurement method of the particle beam dose distribution using thermofluorescence is still sufficiently LET-dependent for each line type for each thermophosphor used. It was not known and was not sufficient in terms of practicality.
Further, there is a problem that LET calculated by the HTR method described in Non-Patent Document 1 has a large error, and has not yet been sufficiently practical.
For this reason, there is a need for a method that can understand the LET dependence of the thermophosphor with high accuracy and easily, determine the dose distribution of the particle beam, and determine the thermofluorescence characteristics of the thermophosphor.
Accordingly, an object of the present invention is to establish a method for measuring LET dependency (a method for detecting a peak having no dependency) with high accuracy and in a simple manner to clarify the dose distribution of the particle beam and An object of the present invention is to provide a determination method capable of determining the thermofluorescence characteristics.
本発明者らは、上記課題を解消すべく鋭意検討した結果、Ａｌ２Ｏ３において、粒子線を照射して得られるグロー曲線のうち特定のグローピークがＬＥＴに対する依存性が少ないことを知見し、かかる知見に基づいてこの特定のグローピークを再現性よく検出できる方法を検討するとともに検出したグローピークデータの応用方法について種々検討を行い、本発明を完成するに至った。
すなわち、本発明は以下の各発明を提供するものである。
１．熱蛍光体に粒子線を照射し、照射後の熱蛍光体を所定の昇温速度で昇温して熱蛍光特性を測定するか、特定の波長の光のみで熱蛍光特性を測定することにより、ＬＥＴ依存性のない非依存性ピークを検出するＬＥＴ非依存性ピーク検出法。
２．所定の熱蛍光体における粒子線のＬＥＴと線量分布測定法であって、
上記熱蛍光体に粒子線を照射し、照射後の熱蛍光体を所定の昇温速度で昇温して熱蛍光特性を測定するか、特定の波長の光のみで熱蛍光特性を測定することにより、ＬＥＴ依存性のない非依存性ピークを検出し、該非依存性ピークの測定値から線量分布測定を行う線量分布測定法。
As a result of intensive studies to solve the above problems, the present inventors have found that in Al 2 O 3 , a specific glow peak in a glow curve obtained by irradiating a particle beam has little dependency on LET. Based on these findings, the present inventors have studied a method capable of detecting this specific glow peak with good reproducibility and variously studied application methods of the detected glow peak data, thereby completing the present invention.
That is, the present invention provides the following inventions.
1. By irradiating the thermoluminescent material with a particle beam and measuring the thermoluminescent property by raising the temperature of the irradiated thermoluminescent material at a predetermined temperature increase rate or measuring the thermoluminescent property only with light of a specific wavelength LET-independent peak detection method for detecting an independent peak without LET dependency.
2. A particle beam LET and dose distribution measurement method for a predetermined thermophosphor,
Irradiate the thermoluminescent material with a particle beam and measure the thermoluminescent property by raising the temperature of the thermoluminescent material after irradiation at a predetermined temperature increase rate, or measure the thermoluminescent property only with light of a specific wavelength. The dose distribution measurement method which detects an independent peak without LET dependence and performs dose distribution measurement from the measured value of the independent peak.
本発明の検出法は、高精度且つ簡易にＬＥＴ依存性のない熱蛍光スペクトルを示すピークを検出でき、粒子線の線量分布や熱蛍光特性を測定する方法に適用できるものである。
本発明の線量分布測定法は、高精度且つ簡易に粒子線の線量分布を測定することができるものである。
本発明の判定法は、高精度且つ簡易に、熱蛍光体の熱蛍光特性を判定できるものである。
The detection method of the present invention can detect a peak showing a thermofluorescence spectrum that does not depend on LET with high accuracy and easily, and can be applied to a method of measuring the dose distribution and thermofluorescence characteristics of particle beams.
The dose distribution measurement method of the present invention can measure the dose distribution of particle beams with high accuracy and simplicity.
The determination method of the present invention can determine the thermoluminescent property of a thermoluminescent material with high accuracy and simplicity.
以下、本発明をさらに詳細に説明する。
〔ＬＥＴ非依存性ピーク検出法〕
本発明の検出法は、熱蛍光体に粒子線を照射し、照射後の熱蛍光体を所定の昇温速度で昇温して熱蛍光特性を測定するか、特定の波長の光のみで熱蛍光特性を測定することにより、ＬＥＴ依存性のない非依存性ピークを検出するＬＥＴ非依存性ピーク検出法である。
Hereinafter, the present invention will be described in more detail.
[LET-independent peak detection method]
In the detection method of the present invention, the thermoluminescent material is irradiated with a particle beam, and the thermoluminescent material after the irradiation is heated at a predetermined temperature increase rate to measure thermoluminescent properties, or only with light of a specific wavelength. This is a LET-independent peak detection method for detecting an independent peak without LET dependency by measuring fluorescence characteristics.
＜熱蛍光体＞
本発明の検出法に用いられる上記熱蛍光体は、粒子線により熱蛍光を発生する特性を有すれば、特に制限されず、例えば、金属酸化物を主成分としてなるセラミックスからなり、
発光中心成分を含有するもの等が挙げられる。
ここで、上記主成分とは、上記セラミックスがその全重量に対して５０重量％以上含有することを意味し、好ましくは７０重量％以上である。
上記金属酸化物は、セラミックスを形成するものであれば、特に制限されず、例えば、Ｌｉ、Ｂｅ、Ｎａ、Ｍｇ、Ａｌ、Ｋ、Ｃａ、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｇａ、Ｇｅ、Ｒｂ、Ｓｒ、Ｙ、Ｚｒ、Ｎｂ、Ｍｏ、Ｔｃ、Ｒｕ、Ｒｈ、Ｐｄ、Ａｇ、Ｃｄ、Ｉｎ、Ｓｎ、Ｓｂ、Ｃｓ、Ｂａ、Ｈｆ、Ｔａ、Ｗ、Ｒｅ、Ｏｓ、Ｉｒ、Ｐｔ、Ａｕ、Ｈｇ、Ｔｌ、Ｐｂ、Ｂｉ、Ｐｏ、Ｆｒ、Ｒａ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｐｍ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、Ａｃ、Ｔｈ、Ｐａ、Ｕ、Ｎｐ、Ｐｕ、Ａｍ、Ｃｍ、Ｂｋ、Ｃｆ、Ｅｓ、Ｆｍ、Ｍｄ、Ｎｏ、Ｌｒなどの金属の酸化物を挙げることができ、これらの金属酸化物は単体または混合物を使用することができる。具体的には、Ａｌ２Ｏ３、ＢａＳＯ４、ＬｉＦ、ＢｅＯ、ＣａＦ、Ｌｉ２Ｂ４Ｏ７、ＣａＳＯ４等からなる群より選択される化合物を挙げることができ、中でもＡｌ２Ｏ３が好ましい。
<Thermophosphor>
The thermophosphor used in the detection method of the present invention is not particularly limited as long as it has the property of generating thermofluorescence by a particle beam, and is made of, for example, a ceramic mainly composed of a metal oxide,
Examples include those containing an emission center component.
Here, the main component means that the ceramic is contained in an amount of 50% by weight or more based on the total weight, and preferably 70% by weight or more.
The metal oxide is not particularly limited as long as it forms ceramics. For example, Li, Be, Na, Mg, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Cs, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, Fr, Ra, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Examples of the metal oxide include Yb, Lu, Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, and Lr. Can be used alone or as a mixture. Specifically, a compound selected from the group consisting of Al 2 O 3 , BaSO 4 , LiF, BeO, CaF, Li 2 B 4 O 7 , CaSO 4 and the like can be mentioned, and among them, Al 2 O 3 is preferable. .
本明細書において、上記発光中心成分とは、放射線や粒子線を照射した熱蛍光体において励起され光を放出する成分をいう。
上記発光中心成分は、特に制限されず、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｙ、Ｚｒ、Ｎｂ、Ｍｏ、Ｐｄ、Ａｇ、Ｈｆ、Ｔａ、Ｗ、Ｒｅ、Ｏｓ、Ｉｒ、Ｐｔ、Ａｕ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｐｍ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ及びＬｕからなる群より選ばれる少なくとも一つの金属元素を挙げることができる。
上記金属酸化物と上記発光中心成分との配合割合は、両者の重量の合計量を１００とした場合に、金属酸化物：発光中心成分＝９０〜９９．９９９：０．００１〜１０とするのが好ましい。
なお、上記熱蛍光体は、熱蛍光特性を示す市販のものを用いることもできる。市販のものとしては、例えば、セラミックス（型名：Ａ４７６、京セラ社製（（Ａｌ２Ｏ３含有量９６％））などが挙げられる。
In the present specification, the luminescent center component refers to a component that is excited and emitted by a thermoluminescent material irradiated with radiation or particle beams.
The emission center component is not particularly limited, and Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Pd, Ag, Hf, Ta, W, Re At least one metal element selected from the group consisting of Os, Ir, Pt, Au, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. Can be mentioned.
The blending ratio of the metal oxide and the emission center component is set to metal oxide: luminescence center component = 90 to 99.999: 0.001 to 10 when the total weight of both is 100. Is preferred.
In addition, the commercially available thing which shows a thermoluminescent characteristic can also be used for the said thermoluminescent substance. Examples of commercially available products include ceramics (model name: A476, manufactured by Kyocera Corporation ((Al 2 O 3 content: 96%)).
＜粒子線＞
本発明の検出法で用いられる上記粒子線は、特に制限されず、例えば、アルファ線、ベータ線、陽電子線、陽子線、Ｈｅ、Ｃ、Ｎｅ、Ｓｉ、Ａｒ、Ｆｅなどの重イオン線、中性子線などが挙げられる。
<Particle beam>
The particle beam used in the detection method of the present invention is not particularly limited, and examples thereof include alpha rays, beta rays, positron rays, proton rays, heavy ion rays such as He, C, Ne, Si, Ar, Fe, and neutrons. Examples include lines.
＜照射＞
上記粒子線の照射の方法は、特に制限されず、公知の方法で照射を行うことができ、例えば、放射線医学総合研究所のＨＩＭＡＣなどを用いて行うことができる。
上記粒子線の照射量は、特に制限されないが、 １ 〜 ２０ Ｇｙであると好ましい。
<Irradiation>
The particle beam irradiation method is not particularly limited, and irradiation can be performed by a known method, for example, using HIMAC of the National Institute of Radiological Sciences.
The irradiation amount of the particle beam is not particularly limited, but is preferably 1 to 20 Gy.
＜検出＞
本発明の検出法においては、検出する際に、照射後の熱蛍光体を所定の昇温速度で昇温して熱蛍光特性を測定する手法（手法１）と、照射後の熱蛍光体を特定の波長の光のみで熱蛍光特性を測定する手法（手法２）とのいずれかを用いる。
以下、両者について説明する。
（手法１）
手法１について図１を参照して具体的に説明する。
図１は、上記熱蛍光体（型名：Ａ４７６、京セラ社製（Ａｌ２Ｏ３含有量９６％のセラミックス））に、Ｘ線、Ｈｅ線、Ｃ線、Ｎｅ線を同線量（２０Ｇｙ）の照射をし、照射後の熱蛍光体を所定の昇温温度で昇温して熱蛍光特性を測定した結果の一例である。
この場合の熱蛍光特性は、発光量を温度の関数で表すいわゆるグロー曲線の特性である。
なお、照射した粒子線・放射線のＬＥＴは、Ｎｅ線＞Ｃ線＞Ｈｅ線＞Ｘ線である。
図１に示すように、図１のＢに示すピークは、その強度がＬＥＴの大きさとは逆にＮｅ線＜Ｃ線＜Ｈｅ線＜Ｘ線であり、ＬＥＴに依存的であることがわかる。
一方、図１のＡに示すピークは、照射した粒子線・放射線の線種に関わらず、同程度のピーク強度を示しており、ＬＥＴ依存性のない非依存性ピークであることがわかる。
ここで、上記の「同程度」とは、ピーク強度がおよそ ±３％以内の範囲内にあることをいう。
上記所定の昇温速度は、０．５℃／秒以下であるのが好ましく、０．１℃／秒以下であるとより好ましい。このような昇温速度で温度を上昇させてグロー曲線の測定を行うことにより、ピークを高精度に測定することができ、ピークごとの異同を明確に把握することができる。換言すると、このような昇温速度にて温度を上昇させることによって初めてＬＥＴ依存性のピークの存在が明らかになったのであって、この昇温速度が本発明の特徴点であると言える。
また、上記の測定温度の範囲は、特に制限されないが、通常、室温〜４００℃である。
なお、上記測定に用いられる装置は、上記の所定の昇温速度に制御が可能であれば、特に制限されず、例えば、実施例に示すような光子の数を計数するフォトンカウンティングヘッドと、昇温装置と、遮光された測定部とを備える装置等を用いることができる。
<Detection>
In the detection method of the present invention, when detecting, a method (method 1) of measuring the thermoluminescent property by increasing the temperature of the thermoluminescent material after irradiation at a predetermined temperature increase rate, and the thermoluminescent material after irradiation. Any one of the methods (method 2) for measuring the thermofluorescence characteristics using only light of a specific wavelength is used.
Hereinafter, both will be described.
(Method 1)
The method 1 will be specifically described with reference to FIG.
FIG. 1 shows the above-mentioned thermophosphor (type name: A476, manufactured by Kyocera Corporation (Al 2 O 3 content 96% ceramics)) with X-rays, He rays, C rays, Ne rays at the same dose (20 Gy). It is an example of the result of irradiating and measuring the thermoluminescent property by heating the irradiated thermophosphor at a predetermined temperature rise.
The thermoluminescent property in this case is a so-called glow curve property in which the amount of light emission is expressed as a function of temperature.
The LET of the irradiated particle beam / radiation is Ne line> C line> He line> X ray.
As shown in FIG. 1, the peak shown in FIG. 1B has an intensity that is Ne line <C line <He line <X ray contrary to the magnitude of LET, and is dependent on LET.
On the other hand, the peak shown in A of FIG. 1 shows the same peak intensity regardless of the type of irradiated particle beam / radiation, indicating that it is an independent peak without LET dependency.
Here, the above “same degree” means that the peak intensity is within a range of about ± 3%.
The predetermined heating rate is preferably 0.5 ° C./second or less, and more preferably 0.1 ° C./second or less. By measuring the glow curve by increasing the temperature at such a rate of temperature increase, the peak can be measured with high accuracy, and the difference between the peaks can be clearly grasped. In other words, the presence of a LET-dependent peak was clarified only by increasing the temperature at such a temperature increase rate, and it can be said that this temperature increase rate is a feature of the present invention.
Moreover, the range of said measurement temperature is although it does not restrict | limit in particular, Usually, it is room temperature-400 degreeC.
The apparatus used for the measurement is not particularly limited as long as it can be controlled to the predetermined temperature increase rate. For example, a photon counting head for counting the number of photons as shown in the examples, an ascending An apparatus or the like that includes a temperature device and a light-shielded measurement unit can be used.
（手法２）
手法２は、照射後の熱蛍光体を特定の波長の光のみで熱蛍光特性を測定する手法である。
上記の特定の波長は、例えば、Ａｌ２Ｏ３（Ａ４７６）の熱蛍光体においては、６９３ｎｍである。
この際用いることができる上記光学フィルターは、一般的に使用されるバンドパスフィルター、ロングパスフィルターなど公知のものを用いることができ、検出する波長により適宜変更されうるものである。
(Method 2)
Method 2 is a method of measuring the thermoluminescent properties of the irradiated thermophosphor with only light of a specific wavelength.
The specific wavelength is, for example, 693 nm in the Al 2 O 3 (A476) thermophosphor.
As the optical filter that can be used in this case, a known filter such as a generally used band-pass filter or long-pass filter can be used, and can be appropriately changed depending on the wavelength to be detected.
以上の説明のとおり、本発明の検出法は高精度且つ簡易にＬＥＴ依存性のないスペクトるピークを検出することができる。
また、本発明の検出法は、ＬＥＴを測定する方法、粒子線の線量分布を測定する方法に好適に適用することができ、これらの方法を高精度且つ簡易に実行することを可能にする。
As described above, the detection method of the present invention can detect a spectral peak without LET dependency with high accuracy and ease.
Moreover, the detection method of the present invention can be suitably applied to a method for measuring LET and a method for measuring the dose distribution of particle beams, and makes it possible to execute these methods with high accuracy and simplicity.
〔線量分布測定法〕
次に、本発明の線量分布測定法を説明する。
以下の説明においては上述の検出法と異なる点を中心に説明する。特に説明しない点については上述の説明が適宜適用される。
[Dose distribution measurement method]
Next, the dose distribution measuring method of the present invention will be described.
The following description will focus on differences from the detection method described above. The above description is appropriately applied to points that are not particularly described.
本発明の線量分布測定法は、所定の熱蛍光体における粒子線の線量分布測定法であって、
上記熱蛍光体に粒子線を照射し、照射後の熱蛍光体を所定の昇温速度で昇温して熱蛍光特性を測定するか、特定の波長の光のみで熱蛍光特性を測定することにより、ＬＥＴ依存性のない非依存性ピークを検出し、該非依存性ピークの測定値から線量分布測定を行う線量分布測定法である。
The dose distribution measurement method of the present invention is a particle beam dose distribution measurement method in a predetermined thermophosphor,
Irradiate the thermoluminescent material with a particle beam and measure the thermoluminescent property by raising the temperature of the thermoluminescent material after irradiation at a predetermined temperature increase rate, or measure the thermoluminescent property only with light of a specific wavelength. Is a dose distribution measurement method in which an independent peak having no LET dependency is detected and a dose distribution is measured from the measured value of the independent peak.
粒子線を照射してから非依存性ピークを検出するまでは上述の「検出法」と同様であるので、線量分布測定を行う工程について図１を参照して説明する。 Since it is the same as the above-mentioned “detection method” from the irradiation of the particle beam to the detection of the independent peak, the step of measuring the dose distribution will be described with reference to FIG.
例えば、図１に示す条件の場合、図１のＡに示すピークは、上述したように、その発光強度が、ＬＥＴにほとんど依存しないため、ＬＥＴによる補正をすることなく粒子線の線量分布を示すことになる。
すなわち、図１のＡに示すピークの測定値はＬＥＴに依存しないものであるため、このピークを検出すれば、このピークがＬＥＴによる補正をする必要がないため、単位面積中におけるピーク強度の分布を測定すれば、どの部分で線量がどの程度であるかを正確に測定することができる（単位面積当たりの線量分布）。
このように本発明の線量分布測定法は、ＬＥＴに依存しないピークに基づいて線量の分布を測定する方法であるため。補正をすることなく粒子線の線量分布を正確に取得できる。
For example, in the case of the condition shown in FIG. 1, the peak shown in A of FIG. 1 shows the dose distribution of the particle beam without correction by LET because the emission intensity hardly depends on LET as described above. It will be.
That is, since the measured value of the peak shown in FIG. 1A does not depend on LET, if this peak is detected, it is not necessary to correct this peak by LET. By measuring, it is possible to accurately measure in what part the dose is (dose distribution per unit area).
As described above, the dose distribution measurement method of the present invention is a method of measuring the dose distribution based on the peak independent of LET. The dose distribution of the particle beam can be accurately acquired without correction.
〔熱蛍光特性判定法〕
次に、本発明の判定法を説明する。
以下の説明においては上述の検出法、線量分布測定法と異なる点を中心に説明する。特に説明しない点については上述の説明が適宜適用される。
[Thermal fluorescence characteristics judgment method]
Next, the determination method of the present invention will be described.
In the following description, differences from the above-described detection method and dose distribution measurement method will be mainly described. The above description is appropriately applied to points that are not particularly described.
本発明の判定法は、熱蛍光体の熱蛍光測定値を補正するに際して、該熱蛍光体のＬＥＴ依存性を求めて該ＬＥＴ依存性をもって補正し、線質及び線量に対する正確な熱蛍光特性を求める熱蛍光特性の判定法であって、
上記熱蛍光体における所定の昇温速度での１５０〜２００℃における熱蛍光特性を測定し、ＬＥＴ依存性のないピークを特定し、
上記熱蛍光体の測定値における上記のＬＥＴ依存性のないピーク以外のピークについて、補正を行うことを特徴とする判定法である。
In the determination method of the present invention, when correcting the thermofluorescence measurement value of the thermophosphor, the LET dependency of the thermophosphor is obtained and corrected with the LET dependency, and an accurate thermofluorescence characteristic with respect to the radiation quality and dose is obtained. A method for determining a desired thermoluminescent property,
Measure the thermofluorescence characteristics at 150 to 200 ° C. at a predetermined rate of temperature rise in the thermophosphor, identify the peak without LET dependency,
In the determination method, correction is performed for peaks other than the peak having no LET dependency in the measurement value of the thermoluminescent material.
（ピークの特定）
ピークの特定に際して、ＬＥＴ非依存性のピークの検出は、上述の本発明の検出法と同様に行うことができるが、その際の昇温温度範囲は、昇温速度での１５０〜２００℃である。この温度範囲とすることにより、正確にＬＥＴ依存性のないピークを特定することができる。
また、上記ＬＥＴ依存性あるピークは、ＬＥＴ依存性のないピークを検出した後で、対象である熱蛍光体の熱蛍光測定を行い、得られた結果からＬＥＴ依存性のないピークを除外してピークを確認することで把握することができる。具体的には、上述の図１の例では、図１のＢに示すピークである。
(Peak identification)
In the peak identification, the LET-independent peak can be detected in the same manner as the detection method of the present invention described above, but the temperature increase temperature range is 150 to 200 ° C. at the temperature increase rate. is there. By setting this temperature range, it is possible to accurately identify a peak having no LET dependency.
The LET-dependent peak is determined by detecting the peak without LET dependence and then measuring the thermofluorescence of the target thermophosphor, and excluding the peak without LET dependence from the obtained results. This can be determined by checking the peak. Specifically, in the example of FIG. 1 described above, the peak is indicated by B in FIG.
（ＬＥＴの算出）
上述の工程で把握されたＬＥＴ依存性のないピークとそれ以外のＬＥＴ依存性のあるピークとの比を、あらかじめ線種ごとの線量が判明している照射を行い、線種ごとに算出し、得られた比に基づいてＬＥＴを算出する。
(Calculation of LET)
The ratio of the peak without LET dependency obtained in the above process and the other peak with LET dependency is irradiated with the dose for each line type previously determined, and calculated for each line type. LET is calculated based on the obtained ratio.
以下、本発明について実施例及び比較例を示してさらに具体的に説明するが本発明はこれらに何ら制限されるものではない。 EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not restrict | limited to these at all.
〔実施例１〕
（熱蛍光体）
熱蛍光体として、Ａｌ２Ｏ３含有量９６％のセラミックス（商品名：Ａ４７６、京セラ社製）、大きさ（縦 １０ ｍｍ×横 １０ ｍｍ×厚さ １ ｍｍ）を用いた。
[Example 1]
(Thermophosphor)
As the thermoluminescent material, ceramics having a Al 2 O 3 content of 96% (trade name: A476, manufactured by Kyocera Corporation) and size (vertical 10 mm × width 10 mm × thickness 1 mm) were used.
（粒子線・放射線の照射）
それぞれ別々の上記熱蛍光体に対して、２０ＧｙのＸ線、Ｈｅ線、Ｃ線、Ｎｅ線を照射した。
Ｘ線の照射は、ＬＩＮＡＣ（Ｖａｒｉａｎ社製）を用いて行った、
Ｈｅ線、Ｃ線、Ｎｅ線の照射は、ＨＩＭＡＣ（放射線医学総合研究所）を用いて行った。
(Particle beam / radiation irradiation)
20 Gy X-rays, He rays, C rays, and Ne rays were irradiated to each of the above-described thermophosphors.
X-ray irradiation was performed using LINAC (manufactured by Varian).
Irradiation of He line, C line, and Ne line was performed using HIMAC (Radiological Research Institute).
（グロー曲線の測定）
放射線、または、粒子線を照射した熱蛍光体の熱蛍光特性を調べるため、グロー曲線を調べた。
グロー曲線は、図２に示すフォトンカウンティングヘッド（商品名：H11890-210、浜松ホトニクス社製）と、昇温装置（型名：ＳＣＲ−ＳＨＱ−Ａ、坂口電熱社製）と、遮光された測定部としての暗箱と、制御用のソフトウェアーがインストールされているコンピュータ（図示せず）とを備える装置で、下記条件にて測定を行った。
条件：
昇温速度：０．１３℃／ｍｉｎ
測定温度：室温〜４００℃
光学フィルター：なし
得られた結果を図１に示す。
その結果、図１のＡに示すＬＥＴ依存性のない非依存性ピークが検出された。
なお、図１のＡに示すピーク時の温度は １６５ ℃、発光強度は ６×１０４ 、Ｂのピーク時の温度は ２５０ ℃であり、発光強度は ２〜３×１０４ 、Ｃのピーク時の温度は ３１５ ℃であり、発光強度は １．５〜２．２×１０４ であった。
図１のＡに示すピークは、照射した粒子線・放射線のＬＥＴに関係なく強度がほぼ一定であった。
図１のＢ及びＣに示すピークは、ＬＥＴの大きさとは、逆に発光強度が、Ｎｅ線＜Ｃ線＜Ｈｅ線＜Ｘ線の関係であった。
この結果から、図１のＡに示すピークは、発光強度がＬＥＴにほとんど依存しないため、補正をすることなく粒子線の線量分布が取得できることがわかる。
(Measurement of glow curve)
In order to investigate the thermoluminescent property of the thermoluminescent material irradiated with radiation or particle beam, the glow curve was examined.
The glow curve is measured with a photon counting head (trade name: H11890-210, manufactured by Hamamatsu Photonics) shown in FIG. 2, a temperature raising device (model name: SCR-SHQ-A, manufactured by Sakaguchi Electric Heat), and light-shielded measurement. The measurement was performed under the following conditions using an apparatus including a dark box as a unit and a computer (not shown) in which control software is installed.
conditions:
Temperature increase rate: 0.13 ° C./min
Measurement temperature: room temperature to 400 ° C
Optical filter: None
The obtained results are shown in FIG.
As a result, an independent peak having no LET dependency shown in A of FIG. 1 was detected.
The peak temperature shown in A of FIG. 1 is 165 ° C., the emission intensity is 6 × 10 4 , the peak temperature of B is 250 ° C., and the emission intensity is 2 × 3 × 10 4 , at the peak of C. The temperature was 315 ° C., and the emission intensity was 1.5 to 2.2 × 10 4 .
The intensity of the peak shown in FIG. 1A is almost constant regardless of the LET of the irradiated particle beam / radiation.
In contrast to the LET size, the peaks shown in B and C in FIG. 1 have a relationship of emission intensity of Ne line <C line <He line <X ray.
From this result, it can be understood that the dose distribution of the particle beam can be acquired without correction because the peak shown in A of FIG. 1 has almost no dependency on the LET emission intensity.
〔実施例２〕
Ｘ線、Ｎｅ線に対するグロー曲線の線量応答性を測定した。
粒子線・放射線の照射量を変えた以外は、実施例１と同様にして、グロー曲線を測定した。
なお、粒子線・放射線の照射量は、１，２、５、１０、２０Ｇｙで行った。
その結果を、図３（Ｘ線）、図４（Ｎｅ線）に示す。
また、Ｘ線を２０Ｇｙ照射したときと、Ｎｅ線を２０Ｇｙ照射したときと、のグロー曲線を比較した結果を図５に示す。
また、図３、図４それぞれのＡ及びＢに示すピークにおける発光強度を比較した結果を図６に示す。
[Example 2]
The dose response of the glow curve to X-rays and Ne rays was measured.
A glow curve was measured in the same manner as in Example 1 except that the irradiation amount of the particle beam / radiation was changed.
The particle beam / radiation dose was 1, 2, 5, 10, 20 Gy.
The results are shown in FIG. 3 (X-ray) and FIG. 4 (Ne-line).
In addition, FIG. 5 shows a result of comparison of glow curves when X-ray irradiation is performed with 20 Gy and Ne irradiation is performed with 20 Gy.
In addition, FIG. 6 shows the result of comparing the emission intensity at the peaks shown in A and B of FIGS. 3 and 4, respectively.
結果から、図３、図４に示すように、照射した線量に依存的に、発光強度が増加しているのがわかる。
また、図５に示す結果から、図中にＡで示すピークの発光強度は、照射した線種に依存しないことがわかる。すなわち、本方法により、ＬＥＴ依存性のない非依存性ピークが検出されたのがわかる。図６に示す結果からも、照射する線量を変化させても、同様の現象が起こるのがわかる。すなわち、照射する線量を変化させても、本方法により、ＬＥＴ依存性のない非依存性ピークが検出されたのがわかる。
次に、上述の測定値を用いてＬＥＴを算出した。
ＬＥＴの算出に際しては、まずグローピークＡとグローピークＢのＴＬ強度／線量の関係を求める。図７にＸ線、Ｈｅ線、Ｃ線及びＮｅ線の４種の線種に対するピークＡの面積と線量との関係、すなわちピークＡのＴＬ強度／線量、及びこれら４種の線種に対するピークＢの面積と線量との関係、すなわちピークＢのＴＬ強度／線量のを示す。なお、６ＭＶのＸ線のＬＥＴは０．２ｅＶ／μｍ、１５０ＭｅＶ／ｕのＨｅ線のＬＥＴは２ｅＶ／μｍ、２９０ＭｅＶ／ｕのＣ線のＬＥＴは１３．２ｅＶ／μｍ、４００ＭｅＶ／ｕのＮｅ線のＬＥＴは３５ｅＶ／μｍであった。
図７に示すようにグローピークＡとＢのＬＥＴ依存性の違いが確認できる。この違い、すなわちＴＬ強度比を用いることでＬＥＴを算出できる。ＬＥＴを算出するには、図８に示すようにグローピークＢ／Ａの値とＬＥＴとの関係をあらかじめグラフ化して求めておく。ついで、実際の測定値から得られるグローピークＢ／Ａの値をこのグラフに当てはめることでＬＥＴの値を求めることができる。
たとえば、図８に示すＮｅのグローピークＢ／ＡとＬＥＴとの関係グラフから、グローピークＢ／Ａの実測値が０．４であった場合、ＬＥＴは１ｋｅＶ／μｍとなることが判る。
このように本発明の線量分布測定法を用いた検出器を作成すると、かかる検出器は、グローピークＡのＴＬ強度と線量の関係から線量を算出し、グローピークＢ／ＡからＬＥＴを算出できる、ハイブリット検出器となる。
From the results, as shown in FIGS. 3 and 4, it can be seen that the emission intensity increases depending on the irradiated dose.
Further, the results shown in FIG. 5 show that the emission intensity of the peak indicated by A in the figure does not depend on the irradiated line type. That is, it can be seen that an independent peak having no LET dependency was detected by this method. From the results shown in FIG. 6, it can be seen that the same phenomenon occurs even when the irradiation dose is changed. That is, it can be seen that an independent peak having no LET dependency was detected by this method even when the irradiation dose was changed.
Next, LET was calculated using the above measured values.
In calculating LET, first, the relationship between TL intensity / dose of glow peak A and glow peak B is obtained. FIG. 7 shows the relationship between the area and dose of peak A for four types of X-ray, He-line, C-line, and Ne-line, that is, the TL intensity / dose of peak A, and peak B for these four types of lines. 3 shows the relationship between the area and dose, that is, the TL intensity / dose of peak B. Note that 6 MV X-ray LET is 0.2 eV / μm, 150 MeV / u He line LET is 2 eV / μm, 290 MeV / u C line LET is 13.2 eV / μm, 400 MeV / u Ne line. LET was 35 eV / μm.
As shown in FIG. 7, the difference in the LET dependency between the glow peaks A and B can be confirmed. LET can be calculated by using this difference, that is, the TL intensity ratio. In order to calculate LET, the relationship between the value of the glow peak B / A and LET is obtained by graphing in advance as shown in FIG. Next, the value of LET can be obtained by applying the value of the glow peak B / A obtained from the actual measurement value to this graph.
For example, it can be seen from the graph of the relationship between Ne glow peak B / A and LET shown in FIG. 8 that when the measured value of glow peak B / A is 0.4, LET is 1 keV / μm.
Thus, when a detector using the dose distribution measurement method of the present invention is created, such a detector can calculate the dose from the relationship between the TL intensity of the glow peak A and the dose, and can calculate the LET from the glow peak B / A. It becomes a hybrid detector.
以上から、本発明の検出法は、高精度且つ簡易に、ＬＥＴを測定する方法、粒子線の線量分布を測定する方法に適用できるものであることがわかる。
また、本発明の線量分布測定法は、高精度且つ簡易に粒子線の線量分布を測定することができるものであることがわかる。
また、本発明の判定法は、高精度且つ簡易に、ＬＥＴを測定する方法、粒子線の線量分布を測定する方法に適用できるものであることがわかる。
From the above, it can be seen that the detection method of the present invention can be applied to a method for measuring LET and a method for measuring the dose distribution of particle beams with high accuracy and simplicity.
Moreover, it turns out that the dose distribution measuring method of this invention can measure the dose distribution of a particle beam with high precision and simply.
It can also be seen that the determination method of the present invention can be applied to a method for measuring LET and a method for measuring the dose distribution of particle beams with high accuracy and simplicity.
Claims (2)
上記熱蛍光体に粒子線を照射し、照射後の熱蛍光体を所定の昇温速度で昇温して熱蛍光特性を測定するか、特定の波長の光のみで熱蛍光特性を測定することにより、ＬＥＴ依存性のない非依存性ピークを検出し、該非依存性ピークの測定値からＬＥＴと線量分布測定を行う線量分布測定法。 A method for measuring a dose distribution of a particle beam in a predetermined thermophosphor,
Irradiate the thermoluminescent material with a particle beam and measure the thermoluminescent property by raising the temperature of the thermoluminescent material after irradiation at a predetermined temperature increase rate, or measure the thermoluminescent property only with light of a specific wavelength. A dose distribution measurement method for detecting an independent peak having no LET dependence and performing LET and dose distribution measurement from the measured value of the independent peak.
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