【摘要】：目的：以蒙特卡羅模擬的結(jié)果為基準(zhǔn)，評(píng)估各向異性分析算法（Anisotropic AnalyticalAlgorithm，AAA）在非均勻介質(zhì)中的計(jì)算精度。方法：建立一包含非均勻介質(zhì)（空氣、肺、脂肪、肌肉、骨）的水模體,模體大小為40cm×40cm×25cm，非均勻介質(zhì)為30cm×30cm×5cm的平板，位于水模體的5cm深度處。分別用蒙特卡羅方法、AAA算法、筆形束卷積算法（Pencil Beam Convolution，PBC算法）（作為對(duì)比）計(jì)算不同射野（1cm×1cm到10cm×10cm）、不同能量（6MV和15MV）、不同介質(zhì)中的深度劑量和離軸比并做比較。深度劑量的比較使用定義的劑量偏差和劑量偏離因子，在非均勻介質(zhì)區(qū)域和非均勻介質(zhì)后的區(qū)域進(jìn)行。離軸比的比較通過伽馬分析來實(shí)現(xiàn)。 結(jié)果：AAA算法在空氣介質(zhì)中、能量分別為6MV和15MV時(shí)，劑量偏差的范圍分別為40.37%～517.22%、42.55%～560.97%，伽馬分析通過率范圍分別為12.20%～64.63%、21.95%～65.82%，AAA算法的劑量偏差均小于PBC算法，伽馬分析通過率與PBC算法接近。AAA算法在肺介質(zhì)中、能量分別為6MV和15MV時(shí)，劑量偏差的范圍分別為-2.54%～11.63%、-0.92%～26.29%，伽馬分析通過率范圍分別為84.15%～93.90%、87.80%～100.00%，AAA算法除個(gè)別射野的劑量偏差大于PBC算法外，其它均小于PBC算法，伽馬分析通過率均大于PBC算法。AAA算法在脂肪介質(zhì)中、能量分別為6MV和15MV時(shí)，劑量偏差的范圍分別為-2.45%～-1.22%、-3.43%～1.26%，伽馬分析通過率范圍分別為93.90%～97.56%、93.90%～97.56%，AAA算法除能量為6MV、2cm×2cm射野的劑量偏差大于PBC算法外，其它均小于AAA算法，伽馬分析通過率與PBC算法接近。AAA算法在肌肉介質(zhì)中、能量分別為6MV和15MV時(shí)，劑量偏差的范圍分別為0.99%～4.03%、1.65%～4.38%，伽馬分析通過率范圍分別為92.68%～96.34%、95.12～97.56%，AAA算法除能量為15MV時(shí)、1cm×1cm射野的劑量偏差小于PBC算法外，其它均大于PBC算法，，伽馬分析通過率整體與PBC算法接近。AAA算法在骨介質(zhì)中、能量分別為6MV和15MV時(shí)，劑量偏差的范圍分別為1.68%～4.22%、1.47～2.60%，伽馬分析通過率范圍91.46%～97.56%、92.68%～97.56%，AAA算法在能量為6MV時(shí)，劑量偏差均大于PBC算法，伽馬分析通過率整體與AAA算法接近，在能量為15MV時(shí)，除個(gè)別射野的劑量偏差大于PBC算法外，其它均小于PBC算法，伽馬分析通過率均與PBC算法接近。 結(jié)論：AAA算法計(jì)算的精度在空氣、肺、脂肪介質(zhì)中高于PBC算法，而在肌肉、骨介質(zhì)中的精度略低于PBC算法。AAA算法在肺、脂肪介質(zhì)中劑量計(jì)算的結(jié)果與蒙特卡羅模擬的結(jié)果一致性較好，計(jì)算精度較高，但在空氣中的劑量計(jì)算結(jié)果與蒙特卡羅模擬的結(jié)果仍偏離較大。AAA算法在能量為6MV時(shí)、空氣介質(zhì)、肺介質(zhì)、脂肪、肌肉介質(zhì)中劑量計(jì)算的精度高于能量為15MV時(shí)，而骨介質(zhì)中劑量計(jì)算的精度總體上略低于能量為15MV時(shí)。同時(shí)，AAA算法，尤其是PBC算法在1cm×1cm射野時(shí)顯示了較差的計(jì)算精度。
[Abstract]:Aim: to evaluate the accuracy of anisotropic analysis algorithm (Anisotropic AnalyticalAlgorithm,AAA) in inhomogeneous media based on Monte Carlo simulation results. Methods: a water motif containing air, lung, fat, muscle and bone was established. The size of the model was 40cm 脳 40cm 脳 25 cm, and the heterogeneous medium was 30cm 脳 30cm 脳 5cm, which was located at the 5cm depth of the water motif. Monte Carlo method, AAA algorithm and pen-beam convolution algorithm (Pencil Beam Convolution,PBC algorithm) are used to calculate and compare the depth dose and off-axis ratio of different fields (1cm 脳 1cm to 10cm 脳 10cm), different energy (6MV and 15MV), and different medium. The depth dose is compared using the defined dose deviation and dose deviation factor in the inhomogeneous medium and the area behind the inhomogeneous medium. The off-axis ratio is compared by gamma analysis. Results: when the energy of AAA algorithm is 6MV and 15MV in air medium, the range of dose deviation is 40.37, 517.22, 42.55 and 560.97, and the passing rate of gamma analysis is 12.20 and 64.63, respectively. 21.95 the dose deviation of 65.82 AAA algorithm is smaller than that of PBC algorithm, and the passing rate of gamma analysis is close to that of PBC algorithm. When AAA algorithm is in lung medium, its energy is 6MV and 15MV, respectively. The range of dose deviations were -2.54 and 11.63- 0.92 and 26.29, respectively, and the passing rate of gamma analysis was 84.15 and 93.900.The range was 87.80 and 100.00. The dose deviation of the AAA algorithm is larger than that of the PBC algorithm, the other is smaller than that of the PBC algorithm, and the passing rate of gamma analysis is higher than that of the PBC algorithm. When the AAA algorithm is in fat medium, the energy is 6MV and 15MV, respectively. The range of dose deviation is -2.45 and 1.22 and 3.430.The passing rate of gamma analysis is 93.90,97.56and 97.90A, respectively. The energy of the AAA algorithm is 6 MV. The dose deviation of 2cm 脳 2cm field is larger than that of PBC algorithm, and the other is smaller than that of AAA algorithm. The passing rate of gamma analysis is close to that of PBC algorithm. When AAA algorithm is in muscle medium, the energy of AAA algorithm is 6MV and 15MV, respectively. The range of dose deviation is 0.99 and 4.03 and 1.65 and 4.38, respectively. The passing rate of gamma analysis is 92.68 and 96.340.95.1297.56A, except for the energy of 15MV. The dose deviation of 1cm 脳 1cm field is smaller than that of PBC algorithm, but the rest is larger than that of PBC algorithm. The overall passing rate of gamma analysis is close to that of PBC algorithm. When AAA algorithm is in bone medium, the energy of AAA algorithm is 6MV and 15MV, respectively. The dose deviation ranges from 1.68 to 4.22 and from 1.47 to 2.60. The gamma-ray analysis pass rate ranges from 91.46 to 97.56 and 92.68 to 97.56A. When the energy is 6MV, The dose deviation is larger than that of PBC algorithm, and the passing rate of gamma analysis is close to that of AAA algorithm. When the energy is 15MV, the dose deviation of individual field is larger than that of PBC algorithm, and the passing rate of gamma analysis is smaller than that of PBC algorithm. The passing rate of gamma analysis is close to that of PBC algorithm. Conclusion: the accuracy of AAA algorithm is higher than that of PBC algorithm in air, lung and fat medium, but the accuracy in muscle and bone medium is slightly lower than that in PBC algorithm. The results of dose calculation in adipose medium are in good agreement with those of Monte Carlo simulation, and the accuracy of calculation is high, but the result of dose calculation in air still deviates greatly from that of Monte Carlo simulation. AAA algorithm is used when the energy is 6MV. The accuracy of dose calculation in air medium, lung medium, fat medium and muscle medium is higher than that in 15MV medium, while that in bone medium is slightly lower than that in 15MV medium. At the same time, the AAA algorithm, especially the PBC algorithm, shows poor accuracy in the field of 1cm 脳 1cm.
【學(xué)位授予單位】：南華大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2012
【分類號(hào)】：R142

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