本文選題：重離子治癌 + 點(diǎn)掃描��； 參考：《中國科學(xué)院大學(xué)(中國科學(xué)院近代物理研究所)》2016年博士論文

【摘要】：相比于傳統(tǒng)光子放療,重離子束放射治療具有物理學(xué)和生物學(xué)兩方面的優(yōu)勢:一是重離子束具有獨(dú)特的倒轉(zhuǎn)深度劑量分布(Bragg峰);二是傳能線密度(linear energy transfer,LET)和相對生物學(xué)效應(yīng)(relative biological effectiveness,RBE)在Bragg峰區(qū)較高,在坪區(qū)LET較小。因此重離子束在殺死腫瘤細(xì)胞的同時(shí)保護(hù)了正常組織細(xì)胞,達(dá)到精準(zhǔn)放療。目前運(yùn)用于重離子放射治療的束流配送系統(tǒng)有被動(dòng)式束流配送方式和主動(dòng)式束流配送方式兩種�；谥鲃�(dòng)式束流配送方式有柵掃描和點(diǎn)掃描照射方法。點(diǎn)掃描照射方法中,采用橫向和縱向尺寸比較寬的筆形束不利于腫瘤靶區(qū)的三維適形,而采用橫向和縱向尺寸比較窄的筆形束會(huì)大大增加掃描點(diǎn)數(shù)目,延長劑量優(yōu)化時(shí)間,并且對照射參數(shù)控制精度的要求較高。為解決以上矛盾,本文提出了在橫向和縱向上采用兩種尺寸筆形束的組合式點(diǎn)掃描照射方法:利用橫向尺寸(束斑FWHM、sigma)較小、縱向尺寸(初級SOBP的FWHM)較窄的碳離子筆形束對腫瘤靶區(qū)邊緣進(jìn)行照射,利用橫向尺寸(束斑FWHM、sigma)較大、縱向尺寸(初級SOBP的FWHM)較寬的碳離子筆形束對腫瘤靶區(qū)邊緣進(jìn)行照射。便于該照射方法中兩種尺寸碳離子筆形束的靈活切換,本文還提出了沿束流配送方向傾斜微型脊形過濾器來調(diào)節(jié)筆形束縱向尺寸和插入不同厚度散射體改變筆形束橫向尺寸的方法�；贖IRFL裝置CSR深部腫瘤治療終端的主動(dòng)式點(diǎn)掃描束流配送系統(tǒng),利用蒙特卡羅模擬工具SHIELDHIT-HIT12A模擬研究發(fā)現(xiàn):束流配送距離越短,束斑FWHM越小,但劑量均勻性越差;微型脊形過濾器結(jié)構(gòu)周期是影響劑量均勻性的關(guān)鍵因素,周期越小,劑量平坦度越好。因此,在HIRFL裝置重離子治療終端將真空窗設(shè)置在距等中心距離小于125cm、采用結(jié)構(gòu)周期為2mm微型脊形過濾器時(shí),碳離子筆形束的束斑FWHM和靶區(qū)的劑量均勻性可以滿足放射治療的臨床要求。在優(yōu)化后的重離子主動(dòng)式點(diǎn)掃描束流配送系統(tǒng)下,本文建立了點(diǎn)掃描照射方法的碳離子筆形束數(shù)據(jù)庫。通過蒙特卡羅工具SHIELDHIT12A模擬和MATLAB擬合等獲得了碳離子筆形束射程-能量關(guān)系、物理吸收劑量隨深度的分布和束斑sigma隨深度的分布。根據(jù)LQ模型,利用劑量平均LET和LET對α、β的依賴關(guān)系計(jì)算了HSG細(xì)胞存活率為0.1時(shí)碳離子筆形束的相對生物學(xué)效應(yīng)。通過碳離子筆形束物理吸收劑量隨深度的分布和相對生物學(xué)效應(yīng)最終計(jì)算出碳離子筆形束生物有效劑量隨深度的分布。傾斜微型脊形過濾器30度,45度和60度可分別將初級SOBP寬度展寬到原來的約1.16倍,1.42倍和2倍,達(dá)到靈活調(diào)節(jié)碳離子筆形束的縱向尺寸的效果。在束流配送系統(tǒng)的真空窗下游插入0.15mm~0.4mm不同厚度Ta散射體可以將180MeV/u~360MeV/u能量碳離子束束斑sigma從3mm放大到5mm,有效調(diào)節(jié)碳離子筆形束的橫向尺寸(束斑FWHM、sigma)。傾斜微型脊形過濾器和插入不同厚度Ta散射體的的操作可以在加速器改變束流能量時(shí)執(zhí)行,因此這種筆形束參數(shù)的被動(dòng)式調(diào)節(jié)方法不會(huì)額外增加放射治療時(shí)間。本論文通過蒙特卡羅模擬和理論計(jì)算建立了大小束斑筆形束組合式點(diǎn)掃描照射方法。該方法中橫向尺寸較小、縱向尺寸較窄的小束斑碳離子筆形束和橫向尺寸較大、縱向尺寸較寬的大束斑碳離子筆形束之間切換是通過傾斜微型脊形過濾器60度和插入不同厚度的散射體的方式獲得的。相比傳統(tǒng)單一大束斑筆形束點(diǎn)掃描照射方法和單一小束斑筆形束的點(diǎn)掃描照射方法,大小束斑筆形束組合式點(diǎn)掃描照射方法具有:較小的劑量半影和較小劑量遠(yuǎn)端跌落距離、照射參數(shù)精度易于控制、劑量均勻性穩(wěn)健性好和治療時(shí)間短等優(yōu)勢。
[Abstract]:Compared to traditional photon radiotherapy, heavy ion beam radiotherapy has two advantages in physics and biology: first, heavy ion beam has a unique reverse depth dose distribution (Bragg peak); two is the energy transmission line density (linear energy transfer, LET) and the relative biological effect (relative biological effectiveness, RBE) in the Bragg peak region is higher, The LET is smaller in the Ping area. So the heavy ion beam protects the tumor cells and protects the normal tissue cells to achieve accurate radiotherapy. The current beam distribution system used in heavy ion radiation therapy has two kinds of passive beam distribution and active beam distribution. Based on the active beam distribution, there are grid scanning and point scanning illumination. In the point scanning method, the pen shaped beam with wide transverse and longitudinal dimensions is not conducive to the three-dimensional conform of the tumor target area. The number of scanning points will be increased greatly by using the narrow transverse and longitudinal dimensions, and the dose optimization time is prolonged, and the requirements of the control precision of the reference number are higher. In order to solve the above contradiction, In this paper, a combined point scanning method of two sizes of pencil beams is proposed in the transverse and longitudinal directions: the transverse size (beam spot FWHM, sigma) is smaller, and the longitudinal size (primary SOBP FWHM) is smaller than the narrow carbon ion beam to irradiate the edge of the tumor target area. The transverse size (the beam spot FWHM, sigma) is larger and the longitudinal size (primary SOBP). FWHM) a wide carbon ion pencil beam irradiates the edge of the tumor target area. It is convenient for the flexible switching of two kinds of carbon ion beam in the irradiation method. This paper also proposes that the longitudinal size of the pencil shaped beam is adjusted along the direction of the distribution of the beam in the beam distribution direction and the transverse size of the pen shaped beam is changed by inserting different thickness scatters. Method. The active point scanning beam distribution system based on the treatment terminal of the HIRFL CSR deep tumor treatment terminal, using the Monte Carlo simulation tool SHIELDHIT-HIT12A simulation study found that the shorter the beam distribution distance, the smaller the beam spot FWHM, the worse the dose uniformity; the period of the micro ridge filter is the key factor affecting the dose uniformity, and the cycle is the key factor. The better the dose flatness is, the better. Therefore, when the distance of the vacuum window is set at the distance of the center of the distance less than 125cm and the structure cycle is 2mm minitype ridge filter, the dose uniformity of the beam spot FWHM of the carbon ion pencil beam and the target area can meet the clinical requirement of the radiation therapy in the HIRFL device. In the point scanning beam distribution system, a carbon ion beam database with point scanning irradiation is established in this paper. Through the Monte Carlo tool SHIELDHIT12A simulation and MATLAB fitting, the relationship between the beam range and energy of the carbon ion beam is obtained, the distribution of the physical absorbed dose with the depth and the distribution of the beam spot Sigma with the depth. The use of the LQ model is used. The dependence of the average dose of LET and LET on alpha and beta was calculated for the relative biological effect of the carbon ion pencil beam with the HSG cell survival rate of 0.1. The distribution of the effective dose of the carbon ion pencil beam with the depth distribution was calculated by the physical absorption dose of the carbon ion beam and the relative biological effects. The filter 30 degrees, 45 degrees and 60 degrees can widen the primary SOBP width to about 1.16 times, 1.42 times and 2 times, respectively, to adjust the longitudinal size of the carbon ion pencil beam flexibly. The 180MeV/u~360MeV/u energy carbon beam spot Sigma can be sigma from 3mm in the downstream of the vacuum window of the beam distribution system. It is amplified to 5mm to effectively regulate the transverse size of the carbon ion pencil beam (beam spot FWHM, sigma). The operation of the inclined micro ridge filter and the insertion of different thickness Ta scatterers can be performed at the accelerator's beam energy. Therefore, the passive adjustment method of this pencil beam parameter will not increase the time of radiation therapy. This paper is adopted in this paper. Monte Carlo simulation and theoretical calculation set up a small beam spot beam combination point scanning irradiation method. In this method, the small transverse size, the narrow longitudinal size of the small beam spot carbon ion beam and the larger transverse size, the wide beam spot carbon ion beam with a wider longitudinal dimension are 60 degrees through the inclined micro ridge filter. Compared with the traditional single large beam spot beam point scanning method and the single beam spot pencil beam point scanning irradiation method, the size beam spot pencil beam combination point scanning method has the smaller dose penumbra and the smaller dose distal drop distance, and the precision of the irradiation parameter is easy to control. The system has the advantages of good uniformity, good stability and short treatment time.

【學(xué)位授予單位】：中國科學(xué)院大學(xué)(中國科學(xué)院近代物理研究所)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：R730.55

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本文編號(hào)：1862092