發(fā)布時(shí)間：2018-02-20 16:42

  本文關(guān)鍵詞： 放射治療 CT模擬定位機(jī) 質(zhì)量控制 空間分辨率　出處：《清華大學(xué)》2012年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：CT模擬定位機(jī)是放射治療的輔助設(shè)備，用來(lái)模擬放射治療的幾何條件來(lái)確定照射部位，CT模擬定位機(jī)必須是穩(wěn)定的、安全的和性能可靠的。沒(méi)有質(zhì)量控制和質(zhì)量保證的CT模擬定位機(jī)是毫無(wú)意義的，因此建立一套完善的質(zhì)量控制方法和標(biāo)準(zhǔn)具有十分重要的意義。 論文將CT模擬定位機(jī)的質(zhì)量控制大體分為三個(gè)部分：電離輻射劑量測(cè)量、影像質(zhì)量評(píng)價(jià)和幾何定位精度檢測(cè)，這三個(gè)部分可以同時(shí)實(shí)施，也可以根據(jù)臨床需要建立每日、每周或每月的質(zhì)量保證程序。本研究使用catphan-500型性能模體、診斷水平劑量?jī)x等質(zhì)控設(shè)備。通過(guò)大量實(shí)驗(yàn)，首先研究了掃描參數(shù)對(duì)CT模擬定位機(jī)性能的影響，確定了日常質(zhì)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(zhì)控設(shè)備的使用、檢測(cè)結(jié)果的處理等方面詳細(xì)描述了CT模擬機(jī)質(zhì)量控制的實(shí)施過(guò)程。一臺(tái)合格的CT模擬定位機(jī)必須滿足以下技術(shù)指標(biāo)： 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(quán)CT劑量指數(shù)(CTDIW)頭部不超過(guò)60mGy，腹部不超過(guò)35mGy。 2．影像質(zhì)量：在規(guī)定的掃描條件下，對(duì)Catphan-500型性能模體進(jìn)行成像。CT值的均勻性不超過(guò)4.0HU；標(biāo)準(zhǔn)常規(guī)重建算法條件下，噪聲水平應(yīng)不大于0.35%；對(duì)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(yīng)不超過(guò)6.0HU；CT值線性偏差一般不超過(guò)5.0%；掃描層厚偏差不超過(guò)1.0mm（薄層掃描不超過(guò)標(biāo)稱(chēng)值的50%）；空間分辨率應(yīng)大于5.0線對(duì)每厘米；低對(duì)比度分辨力，應(yīng)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(dòng)誤差應(yīng)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(fù)移動(dòng)最大誤差不超過(guò)1.0mm。 從腫瘤的定位、治療計(jì)劃的設(shè)計(jì)、劑量分布的計(jì)算，到計(jì)劃的模擬、實(shí)施，CT模擬定位機(jī)的應(yīng)用貫穿了放射治療的全過(guò)程，它的性能直接關(guān)系到放射治療的質(zhì)量。論文充分考慮國(guó)內(nèi)不同型號(hào)CT模擬定位機(jī)的使用現(xiàn)狀，對(duì)常用質(zhì)控設(shè)備、質(zhì)控方法、技術(shù)指標(biāo)等內(nèi)容進(jìn)行詳細(xì)的描述。根據(jù)制定的各項(xiàng)質(zhì)量保證程序?qū)T模擬定位機(jī)進(jìn)行定期的檢測(cè)，確保該系統(tǒng)在臨床應(yīng)用中的穩(wěn)定與安全。實(shí)驗(yàn)結(jié)果表明，，這套方法簡(jiǎn)單易行，具有一定的推廣價(jià)值，為相關(guān)國(guó)家標(biāo)準(zhǔn)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(xué)位授予單位】：清華大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2012
【分類(lèi)號(hào)】：R318.6

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本文編號(hào)：1519472