Three-dimensional anisotropic adaptive filtering of projection data for noise reduction in cone beam CT
Three-dimensional anisotropic adaptive filtering of projection data for noise reduction in cone beam CT
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DOI：
10.1118/1.3633901
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发表时间：
2011-11-01
期刊：
影响因子：
3.8
通讯作者：
Fahrig, Rebecca
中科院分区：
文献类型：
--
作者：
Maier, Andreas;Wigstrom, Lars;Fahrig, Rebecca
目的：将快速旋转的C形臂支架与数字平板相结合，可在介入治疗室中获取三维数据。然而，由于硬件尚未针对CT成像进行优化，因此图像质量仍然受到一定程度的限制。自适应各向异性滤波能够通过降低噪声水平和辐射剂量来改善图像质量，而不会引入明显的模糊。通过在3D重建之前应用该滤波，与在图像域中的处理相比，减少了噪声引起的条纹伪影。方法：使用3D各向异性自适应滤波来处理沿物体周围圆形轨迹采集的2DX光图像集合。在将输入数据排列到3D空间(2D投影+角度)之后，使用一组不同方向的过滤器来估计结构的方向。利用得到的局部取向张量表示来控制各向异性滤波。低通滤波仅沿结构应用，以保持与这些结构垂直的高空间频率分量。对所提出的算法的评估包括使用AXIOM ARTIS DTA C-ARM系统(德国Forchheim的西门子公司Healthcare Sector)获取的数值模拟、模型实验和体内数据。比较了有无自适应滤波的空间分辨率和噪声水平。结果：自适应各向异性滤波算法通过将噪声水平降低一半(某些区域的标准差从74HU降低到30HU)，显著提高了低对比度检测能力。在调制传递函数(MTF)分析中，几乎没有观察到高对比度空间分辨率的下降。虽然该算法计算密集，但使用NVIDIA的CUDA接口的硬件加速使处理速度提高了8.9倍(从1336到150 S)。结论：自适应各向异性滤波具有显著提高图像质量和/或降低使用锥束CT获取3D图像数据所需的辐射剂量的潜力。(C)2011年美国医学物理学家协会。[DOI：10.1118/1.3633901]
Purpose: The combination of quickly rotating C-arm gantry with digital flat panel has enabled the acquisition of three-dimensional data (3D) in the interventional suite. However, image quality is still somewhat limited since the hardware has not been optimized for CT imaging. Adaptive anisotropic filtering has the ability to improve image quality by reducing the noise level and therewith the radiation dose without introducing noticeable blurring. By applying the filtering prior to 3D reconstruction, noise-induced streak artifacts are reduced as compared to processing in the image domain.Methods: 3D anisotropic adaptive filtering was used to process an ensemble of 2D x-ray views acquired along a circular trajectory around an object. After arranging the input data into a 3D space (2D projections + angle), the orientation of structures was estimated using a set of differently oriented filters. The resulting tensor representation of local orientation was utilized to control the anisotropic filtering. Low-pass filtering is applied only along structures to maintain high spatial frequency components perpendicular to these. The evaluation of the proposed algorithm includes numerical simulations, phantom experiments, and in-vivo data which were acquired using an AXIOM Artis dTA C-arm system (Siemens AG, Healthcare Sector, Forchheim, Germany). Spatial resolution and noise levels were compared with and without adaptive filtering. A human observer study was carried out to evaluate low-contrast detectability.Results: The adaptive anisotropic filtering algorithm was found to significantly improve low-contrast detectability by reducing the noise level by half (reduction of the standard deviation in certain areas from 74 to 30 HU). Virtually no degradation of high contrast spatial resolution was observed in the modulation transfer function (MTF) analysis. Although the algorithm is computationally intensive, hardware acceleration using Nvidia's CUDA Interface provided an 8.9-fold speed-up of the processing (from 1336 to 150 s).Conclusions: Adaptive anisotropic filtering has the potential to substantially improve image quality and/or reduce the radiation dose required for obtaining 3D image data using cone beam CT. (C) 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3633901]