数字乳腺层析成像投影数据优化及校正技术研究
发布时间：2019-01-25 08:37
【摘要】：数字乳腺层析(Digital Breast Tomosynthesis,DBT)成像技术是以传统体层摄影几何原理为基础的新型体层成像技术,其主要以平板探测器数据采集及动态成像等特性为依托,运用与传统数字乳腺X线摄影设备类似的压迫板,将乳腺组织均匀挤压到探测器平面上,减少组织结构重叠。在数据采集过程中,探测器保持静止,X线源围绕压迫乳腺以某一个限定角度做弧形运动,采集有限角度内低剂量投影数据,回顾性地重建与探测器平面平行的任意断层层面的图像。相比于二维投照下的传统数字乳腺X线摄影技术,DBT成像技术更好的利用了组织结构的三维特性,其重建的断层图像有效避免了因腺体结构重叠造成的病灶掩盖的“假阳性”问题,提高图像的“可见度”,尤其对边缘轮廓、微小钙化点的显像更具优势。而相比于计算机断层成像技术(Computed Tomography,CT)的全角度数据采集方式,有限角度范围内低剂量投影数据的获取将有效降低总辐射剂量,提高断层图像的对比度分辨率。总的来说,这种新型实用的断层成像模式,既克服了传统数字乳腺X线摄影技术因组织结构重叠所带来的影响,又避免了 CT成像中投影剂量过大的问题,降低了辐射剂量对人体的损伤,可以预计,DBT成像技术在乳腺癌的筛查及诊断中均有相当广泛的应用前景。由于受到DBT成像技术特有的成像几何及乳腺软组织结构囊肿及钙化点等特殊性的制约,易造成重建图像质量的退化;受层间伪影的影响易造成组织结构模糊程度增加,影响临床的诊断与治疗。受限于设备所使用的平板探测器性能因素,易造成暗电流现象、光场不均匀分布、响应曲线不一致现象等,直接影响投影数据的质量,从而导致重建图像形成多种伪影,如环形伪影、条状伪影等。囿于上述,本文拟针对DBT成像技术限角成像的几何特性,开展投影数据角度优化的策略研究,主要包括乳腺数字体模仿真、系统矩阵校正以及投影角度分布情况对成像质量影响的研究;同时针对平板探测器投影数据采集过程性能缺陷,开展投影数据校正对DBT重建图像质量的影响研究,具体总结如下:1.仿真了一套三维数字乳腺体模,并基于DBT成像特有的成像几何对传统迭代重建所使用的系统矩阵进行校正。而后,仿真生成该体模有限角度的投影数据,使用联合代数迭代重建(Simultaneous Algebraic Reconstruction Technique,SART)的方法对仿真投影数据进行重建,比较判断重建断层图像与原始仿真体模的一致性,验证校正后用于DBT成像的投影算子的准确性。2.研究投影数据角度分布情况对DBT成像质量的影响。拟基于DBT现有的成像模式及图像重建方法,设计实验方案判断投影数据在不同角度范围、同角度范围不同投影数量及同角度范围不同角度间隔分布状态下对DBT成像图像质量的影响。使用基于Huber先验的惩罚加权最小二乘(Penalized Weighted Least-Squares,PWLS)迭代重建模型,对实验仿真的投影数据进行断层重建。3.改进并实现了 DBT图像采集过程中的投影数据校正方式,针对平板探测器的投影数据校正过程开展研究。参考传统探测器的数据校正方式,结合DBT成像过程特有的数据采集模式,对探测器所采集的投影数据进行暗场校正、光场及其增益校正等。而后,利用基于全广义变分(Toatl Generalized Variation,TGV)正则化项的PWLS迭代重建算法进行DBT图像重建,判断并总结投影数据校正过程对DBT成像的贡献。
[Abstract]:Digital Breast Toynthesis (DBT) imaging technology is a new type of body tomography technology based on the traditional computed tomography geometry, which is based on the characteristics of the data acquisition and dynamic imaging of the flat panel detector, and uses a compression plate similar to that of the traditional digital mammography equipment. the breast tissue is uniformly pressed onto the plane of the detector to reduce the overlap of the tissue structure. in the data acquisition process, the detector remains stationary and the X-ray source is in an arc-shaped movement around the compression breast at a certain angle, and the low-dose projection data in a limited angle is acquired, and an image at any fault level parallel to the plane of the detector is reconstructed retrospectively. Compared with the traditional digital mammography technique under the two-dimensional projection, the DBT imaging technology better utilizes the three-dimensional characteristics of the tissue structure, the reconstructed tomographic image effectively avoids the 鈥渇alse positive鈥，
本文编号：2414977
[Abstract]:Digital Breast Toynthesis (DBT) imaging technology is a new type of body tomography technology based on the traditional computed tomography geometry, which is based on the characteristics of the data acquisition and dynamic imaging of the flat panel detector, and uses a compression plate similar to that of the traditional digital mammography equipment. the breast tissue is uniformly pressed onto the plane of the detector to reduce the overlap of the tissue structure. in the data acquisition process, the detector remains stationary and the X-ray source is in an arc-shaped movement around the compression breast at a certain angle, and the low-dose projection data in a limited angle is acquired, and an image at any fault level parallel to the plane of the detector is reconstructed retrospectively. Compared with the traditional digital mammography technique under the two-dimensional projection, the DBT imaging technology better utilizes the three-dimensional characteristics of the tissue structure, the reconstructed tomographic image effectively avoids the 鈥渇alse positive鈥，
本文编号：2414977
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