乳腺专用CT剂量和图像质量的定量研究

发布时间：2018-06-08 07:29

本文选题：乳腺专用CT + 滤片　；参考：《兰州大学》2015年硕士论文

【摘要】：乳腺癌作为女性常见的恶性肿瘤之一,死亡率仅次于肺癌,是女性中第一高发的肿瘤,严重地威胁着她们的身心健康乃至生命。据欧美资料表明,通过乳腺普查,可使乳腺癌的死亡率下降30%一40%,然而,在我国,普查出的乳腺癌前病变患者不足20%,所以,乳腺癌的早期发现、早期诊断和早期治疗对提高患者的治愈率、降低死亡率具有十分重要的意义。目前,X射线钼靶成像是比较有效的乳腺普查手段,但只能以二维DR (Digital Radiography)图像显示乳腺的三维结构,成像方向上组织信息互相叠加,立体定位准确性差,不利于较小病灶的检出；乳腺专用CT与常规CT不同,它只针对乳腺结构进行高分辨率断层扫描,无需像钼靶检查时挤压受检者的乳房,提高了舒适性,重建得到自然状态下清晰的乳腺结构的三维影像,克服了钼靶二维成像中组织信息相互叠加的缺陷。在乳腺专用CT(DBCT,Dedicated Breast Computer Tomography)系统中,图像质量和人体所受辐射剂量是倍受关注的两个重要因素,论文首先通过SPEKTR软件包实现多能光谱的光子通量能谱模拟,使用基于蒙特卡洛方法的GATE模拟软件设定了在相同粒子数目条件下多能光谱照射相同尺寸的内置钙化点和肿块乳腺模体,用FBP重建算法重建乳腺模体图像,并且得到乳腺模体内辐射剂量的分布,通过对辐射剂量和图像信噪比等的计算,定义了品质因子M和剂量效率η描述辐射剂量和图像质量之间的关系。论文进一步分析模拟了球管电压为20kV-150kV下每间隔10kV时的图像和剂量,使用最优电压值进行后续对滤片的研究；论文中设计了两种平板滤片和两种异形滤片,对比不同滤片参数条件下的图像质量,确定了一个适合110mm直径常规乳腺模体的滤片形状。研究结果表明：选择合理的管电压值能够获得较好的剂量效率,并且通过优化滤片的形状可以在保证图像质量的同时降低人体所受剂量,为乳腺专用CT的临床应用提供重要参考。
[Abstract]:Breast cancer is one of the most common malignant tumors in women, and its mortality is second only to lung cancer. Breast cancer is the most common cancer in women, which seriously threatens their physical and mental health and even their lives. According to European and American data, breast cancer mortality can be reduced by 30% to 40% through mammary gland screening. However, in our country, fewer than 20 patients with precancerous lesions have been diagnosed, so the early detection of breast cancer. Early diagnosis and early treatment are of great significance to improve the cure rate and reduce the mortality rate. At present, X-ray molybdenum target imaging is an effective method for mammary gland screening, but only 2D Dr digital radiographyimage can show the three-dimensional structure of mammary gland. The tissue information on the imaging direction is superimposed on each other, and the accuracy of stereotactic positioning is poor, which is not conducive to the detection of smaller lesions. Special CT is different from conventional CT in that it only carries out high-resolution tomography for the structure of the mammary gland, without squeezing the breast of the subject when it is examined with molybdenum target, which improves the comfort, and reconstructs the three-dimensional image of the mammary gland structure clearly in the natural state. The defect of superposition of tissue information in two dimensional imaging of molybdenum target is overcome. Image quality and radiation dose to human body are two important factors in breast dedicated CTD DBCTast computer Tomography.Firstly, the photon flux spectrum simulation of multi-energy spectrum is realized by SPEKTR software package. The gate simulation software based on Monte Carlo method is used to set up the built-in calcification points and breast motifs of the same size under the condition of the same number of particles, and to reconstruct the mammary motif images with FBP reconstruction algorithm. The distribution of radiation dose in mammary gland is obtained. By calculating the radiation dose and image signal-to-noise ratio, the relationship between radiation dose and image quality is defined by the definition of quality factor M and dose efficiency 畏 to describe the relationship between radiation dose and image quality. In this paper, the image and dose of the spherical tube voltage at 20kV-150 kV / 10kV interval are simulated, and the optimal voltage value is used to follow up the study of the filter, and two kinds of flat filter and two special-shaped filters are designed in this paper. By comparing the image quality with different filter parameters, a filter shape suitable for conventional mammary gland motifs with 110mm diameters was determined. The results show that a better dose efficiency can be obtained by selecting a reasonable tube voltage value, and by optimizing the shape of the filter, the quality of the image can be guaranteed and the dose to the human body can be reduced at the same time. It provides an important reference for the clinical application of mammary gland special CT.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：R737.9;TP391.41

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