腹部仿真變形體模的制作及其在變形配準驗證中的應用
發(fā)布時間：2019-01-18 16:35
【摘要】：多年來,變形圖像配準(Deformation Image Registration,DIR)方法在自適應放射治療(Adaptive Radiation Therapy,ART)中的應用發(fā)展已經(jīng)進行了很多努力。然而,我們需要回答一個更為緊迫的問題就是如何評估在ART背景下的這些DIR方法的不確定性和驗證其準確性。本研究希望制作一個腹部仿真變形體模,和提供一種可定量評價DIR算法幾何精度和劑量疊加精度的腹部變形體模制作方法,該體�？蓪θ梭w器官變形造成的解剖結(jié)構的復雜變化進行模擬。本研究提出的體模是一個腹部仿真變形體模,體模包含的模擬器官有軟組織、肝臟、腎臟、脾臟、胃、椎骨和兩個轉(zhuǎn)移腫瘤。所有的器官模具都使用來自一個卵巢癌病人的輪廓線進行3D打印成陰模所得到。器官模具塑造了由PVC樹脂粉和對苯二甲酸二辛酯增塑劑不同混合比例的混合物制成的可變形材料。不同密度的軟聚氯乙烯(Polyvinylchlorid,PVC)可以通過多項式擬合曲線得到,該多項式描述了 CT值與PVC樹脂粉-增塑劑混合比例之間的關系。剛性的椎骨通過模具塑形白水泥和纖維素紙漿的混合物制成。將所有模擬器官按照它們的解剖位置放置在一個中空的假人容器里,用模擬肌肉和脂肪平均CT值的變形材料進行密封,最后得到一個腹部體模。195塊1mm3的橡膠立方體作為驗證DIR幾何精度和劑量疊加精度的標記點均勻地嵌入到體模里。為了促進劑量測定驗證,在平行體模上下方向的位置上挖掘兩通道用于電離室插入。使用來自一個開源DIR工具包(DIRART)的三種DIR算法測試了該體模用于基于器官標記點的DIR精度驗證和體內(nèi)劑量測定驗證的可行性。制作的變形材料展示了很好的彈性特性和CT值隨時間推移是穩(wěn)定的,證明這是變形體模的一種滿意材料。該變形體模的內(nèi)部模擬器官具有與真實人體器官相似的CT值,三維解剖結(jié)構和空間位置關系,體模的CT圖像跟真實病人的CT圖像高度相似且對比度明顯,在圖像上可清晰區(qū)分各器官的輪廓和標記點的位置。測量的劑量跟治療計劃系統(tǒng)(treatment planning system,TPS)上計算的劑量顯示了一個很好的一致性。應用該體模進行基于標記點的精度分析驗證了使用體模評估器官方面的DIR精度的可行性。在這項工作中,我們設計和制作了一個3D腹部仿真變形體模,描述了關于體模制作的詳細步驟,包括變形材料配方、器官模塑、標記點嵌入等等,測試了體模的性能,例如變形材料的彈性和CT值隨時間推移的穩(wěn)定性,還證明這體模驗證DIR精度的可行性。正如實驗結(jié)果顯示,體模制作過程簡單,體模材料便宜和不需要專門工具制作。任何機構可以根據(jù)這些步驟制作一個相同或者相似的體模,作為DIR質(zhì)量保證的一個常規(guī)工具。
[Abstract]:Over the years, many efforts have been made in the application of deformable image registration (Deformation Image Registration,DIR) in adaptive radiation therapy (Adaptive Radiation Therapy,ART). However, we need to answer a more urgent question: how to evaluate the uncertainty and verify the accuracy of these DIR methods in the context of ART. The purpose of this study is to make an abdominal simulated deformable model and to provide a method to quantitatively evaluate the geometric accuracy and dose superposition accuracy of the DIR algorithm. The phantom can simulate the complex changes of anatomical structure caused by the deformation of human organs. The phantom proposed in this study is an abdominal phantom containing soft tissue, liver, kidney, spleen, stomach, vertebrae and two metastatic tumors. All organ molds are obtained by 3D printing negative models using contour lines from a ovarian cancer patient. A deformable material was molded by a mixture of PVC resin powder and dioctyl terephthalate plasticizer. Soft polyvinyl chloride (Polyvinylchlorid,PVC) with different densities can be obtained by polynomial fitting curve. The polynomial describes the relationship between CT value and the ratio of PVC resin powder to plasticizer. Rigid vertebrae are made from a mixture of molded white cement and cellulose pulp. All the simulated organs were placed in a hollow dummy container in accordance with their anatomical position and sealed with a deformable material that mimicked the average CT value of muscle and fat. Finally, an abdominal phantom and a rubber cube of 1mm3 are obtained as marks to verify the geometric accuracy of DIR and the accuracy of dose superposition, which are uniformly embedded into the phantom. In order to facilitate dosimetry verification, two channels were excavated in the position parallel to the upper and lower directions of the phantom for the insertion of the ionization chamber. Three DIR algorithms from an open source DIR toolkit (DIRART) were used to test the feasibility of using the phantom to verify the accuracy of DIR based on organ marker points and in vivo dosimetry. The deformable materials show good elastic properties and the CT value is stable over time. It is proved that the deformable material is a satisfactory material for the deformable model. The internal simulated organ of the model has the CT value similar to that of the real human organ, the three-dimensional anatomical structure and the spatial position relation. The CT image of the phantom is highly similar to the CT image of the real patient and the contrast is obvious. The contour of each organ and the location of the marking point can be clearly distinguished on the image. The measured dose shows a good consistency with the dose calculated on the treatment planning system (treatment planning system,TPS. The feasibility of using the phantom to evaluate the DIR accuracy of organs is verified by using the mark-based accuracy analysis. In this work, we designed and made a 3D abdominal simulation deformable model, and described the detailed steps for the fabrication of the phantom, including the formulation of the deformable material, the molding of the organ, the embedding of the marking points, and so on, and tested the performance of the phantom. For example, the elasticity of deformed materials and the stability of CT values over time, and the feasibility of verifying the accuracy of DIR by this model is also proved. As the experimental results show, the fabrication process is simple, the material is cheap and no special tools are needed. Any organization can make an identical or similar phantom based on these steps as a general tool for DIR quality assurance.
【學位授予單位】：南方醫(yī)科大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TP391.41;R815
本文編號：2410899
[Abstract]:Over the years, many efforts have been made in the application of deformable image registration (Deformation Image Registration,DIR) in adaptive radiation therapy (Adaptive Radiation Therapy,ART). However, we need to answer a more urgent question: how to evaluate the uncertainty and verify the accuracy of these DIR methods in the context of ART. The purpose of this study is to make an abdominal simulated deformable model and to provide a method to quantitatively evaluate the geometric accuracy and dose superposition accuracy of the DIR algorithm. The phantom can simulate the complex changes of anatomical structure caused by the deformation of human organs. The phantom proposed in this study is an abdominal phantom containing soft tissue, liver, kidney, spleen, stomach, vertebrae and two metastatic tumors. All organ molds are obtained by 3D printing negative models using contour lines from a ovarian cancer patient. A deformable material was molded by a mixture of PVC resin powder and dioctyl terephthalate plasticizer. Soft polyvinyl chloride (Polyvinylchlorid,PVC) with different densities can be obtained by polynomial fitting curve. The polynomial describes the relationship between CT value and the ratio of PVC resin powder to plasticizer. Rigid vertebrae are made from a mixture of molded white cement and cellulose pulp. All the simulated organs were placed in a hollow dummy container in accordance with their anatomical position and sealed with a deformable material that mimicked the average CT value of muscle and fat. Finally, an abdominal phantom and a rubber cube of 1mm3 are obtained as marks to verify the geometric accuracy of DIR and the accuracy of dose superposition, which are uniformly embedded into the phantom. In order to facilitate dosimetry verification, two channels were excavated in the position parallel to the upper and lower directions of the phantom for the insertion of the ionization chamber. Three DIR algorithms from an open source DIR toolkit (DIRART) were used to test the feasibility of using the phantom to verify the accuracy of DIR based on organ marker points and in vivo dosimetry. The deformable materials show good elastic properties and the CT value is stable over time. It is proved that the deformable material is a satisfactory material for the deformable model. The internal simulated organ of the model has the CT value similar to that of the real human organ, the three-dimensional anatomical structure and the spatial position relation. The CT image of the phantom is highly similar to the CT image of the real patient and the contrast is obvious. The contour of each organ and the location of the marking point can be clearly distinguished on the image. The measured dose shows a good consistency with the dose calculated on the treatment planning system (treatment planning system,TPS. The feasibility of using the phantom to evaluate the DIR accuracy of organs is verified by using the mark-based accuracy analysis. In this work, we designed and made a 3D abdominal simulation deformable model, and described the detailed steps for the fabrication of the phantom, including the formulation of the deformable material, the molding of the organ, the embedding of the marking points, and so on, and tested the performance of the phantom. For example, the elasticity of deformed materials and the stability of CT values over time, and the feasibility of verifying the accuracy of DIR by this model is also proved. As the experimental results show, the fabrication process is simple, the material is cheap and no special tools are needed. Any organization can make an identical or similar phantom based on these steps as a general tool for DIR quality assurance.
【學位授予單位】：南方醫(yī)科大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TP391.41;R815
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