本文關鍵詞： 放射治療 CT模擬定位機 質量控制 空間分辨率　出處：《清華大學》2012年碩士論文　論文類型：學位論文

【摘要】：CT模擬定位機是放射治療的輔助設備，用來模擬放射治療的幾何條件來確定照射部位，CT模擬定位機必須是穩(wěn)定的、安全的和性能可靠的。沒有質量控制和質量保證的CT模擬定位機是毫無意義的，因此建立一套完善的質量控制方法和標準具有十分重要的意義。 論文將CT模擬定位機的質量控制大體分為三個部分：電離輻射劑量測量、影像質量評價和幾何定位精度檢測，這三個部分可以同時實施，也可以根據(jù)臨床需要建立每日、每周或每月的質量保證程序。本研究使用catphan-500型性能模體、診斷水平劑量儀等質控設備。通過大量實驗，首先研究了掃描參數(shù)對CT模擬定位機性能的影響，確定了日常質量控制中選擇的管電壓、管電流、層厚、重建算法等掃描條件，然后從質控設備的使用、檢測結果的處理等方面詳細描述了CT模擬機質量控制的實施過程。一臺合格的CT模擬定位機必須滿足以下技術指標： 1．電離輻射劑量：頭部和腹部模式劑量限值不同，在規(guī)定的掃描條件下，其加權CT劑量指數(shù)(CTDIW)頭部不超過60mGy，腹部不超過35mGy。 2．影像質量：在規(guī)定的掃描條件下，對Catphan-500型性能模體進行成像。CT值的均勻性不超過4.0HU；標準常規(guī)重建算法條件下，噪聲水平應不大于0.35%；對于多排螺旋CT，圖像之間不同層面同一中心位置的CT值偏差應不超過6.0HU；CT值線性偏差一般不超過5.0%；掃描層厚偏差不超過1.0mm（薄層掃描不超過標稱值的50%）；空間分辨率應大于5.0線對每厘米；低對比度分辨力，應能分辨密度差為1.0%的模體中直徑2.0mm的圓孔。 3．幾何定位精度：掃描床的各向移動誤差應小于1.0mm；激光定位系統(tǒng)各部分的定位誤差小于1.0mm；激光定位系統(tǒng)的重復移動最大誤差不超過1.0mm。 從腫瘤的定位、治療計劃的設計、劑量分布的計算，到計劃的模擬、實施，CT模擬定位機的應用貫穿了放射治療的全過程，它的性能直接關系到放射治療的質量。論文充分考慮國內不同型號CT模擬定位機的使用現(xiàn)狀，對常用質控設備、質控方法、技術指標等內容進行詳細的描述。根據(jù)制定的各項質量保證程序對CT模擬定位機進行定期的檢測，確保該系統(tǒng)在臨床應用中的穩(wěn)定與安全。實驗結果表明，，這套方法簡單易行，具有一定的推廣價值，為相關國家標準的制定提供了理論參考。
[Abstract]:The CT analog locator is an auxiliary device for radiotherapy. It is used to simulate the geometric conditions of radiation therapy to determine that the irradiation site must be stable. The CT analog positioning machine without quality control and quality assurance is meaningless, so it is very important to establish a set of perfect quality control methods and standards. In this paper, the quality control of CT analog positioning machine is divided into three parts: dose measurement of ionizing radiation, image quality evaluation and geometric positioning accuracy measurement. These three parts can be implemented at the same time, and can also be established daily according to clinical needs. Weekly or monthly quality assurance procedures. In this study, catphan-500 performance motifs, diagnostic horizontal dosimeter and other quality control equipment were used. Through a large number of experiments, the effect of scanning parameters on the performance of CT analog positioning machine was studied. The scanning conditions such as tube voltage, tube current, layer thickness, reconstruction algorithm and so on in daily quality control are determined, and then from the use of quality control equipment, The process of quality control of CT simulator is described in detail. A qualified CT simulator must meet the following technical specifications:. 1. Dose of ionizing radiation: the dose limits of the model of head and abdomen are different. Under the prescribed scanning conditions, the weighted CT dose index (CTDIW) does not exceed 60 mGy in the head and 35 mGyin in the abdomen. 2. Image quality: under specified scanning conditions, the uniformity of imaging. Ct value of Catphan-500 performance motif is not more than 4.0 HU. under standard conventional reconstruction algorithm, The noise level should not be greater than 0.35; for multi-row spiral CTs, the deviation of CT value between different layers in the same central position should not exceed 6.0HUU CT value linear deviation should not exceed 5.0mm generally; the thickness deviation of scanning slice should not exceed 1.0mm (thin layer scan is not more than nominal value). The spatial resolution should be greater than 5.0 lines per centimeter; The low contrast resolution should be able to distinguish circular holes with a diameter of 2.0 mm in a mode with a density difference of 1.0%. 3. Geometric positioning accuracy: the moving error of each direction of scanning bed should be less than 1.0 mm; the positioning error of every part of laser positioning system should be less than 1.0 mm; the maximum error of repeated movement of laser positioning system should not exceed 1.0 mm. From the localization of tumor, the design of treatment plan, the calculation of dose distribution, to the simulation of plan, the application of CT simulator runs through the whole process of radiotherapy. Its performance is directly related to the quality of radiotherapy. In order to ensure the stability and safety of the system in clinical application, the experimental results show that this method is simple and feasible. It has certain popularizing value and provides a theoretical reference for the formulation of relevant national standards.
【學位授予單位】：清華大學
【學位級別】：碩士
【學位授予年份】：2012
【分類號】：R318.6

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本文編號：1519472