Noise, sampling, and the number of projections in cone-beam CT with a flat-panel detector.
Noise, sampling, and the number of projections in cone-beam CT with a flat-panel detector.
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DOI：
10.1118/1.4875688
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发表时间：
2014-06
期刊：
影响因子：
3.8
通讯作者：
Z. Zhao;G. Gang;J. Siewerdsen
中科院分区：
文献类型：
--
作者：
Z. Zhao;G. Gang;J. Siewerdsen
目的 研究平板探测器锥束 CT (CBCT) 中投影视图数量对图像噪声的影响。方法通过实验（使用呈现均匀介质的模型以及统计驱动的“杂波”）和理论上（使用描述 CBCT 噪声的级联系统模型）解决了 CBCT 系统设计和操作中的这一相当基本的考虑因素，以阐明量子噪声 (σ(Q))、电子噪声 (σ(E)) 和视图混叠 (σ(view)) 的影响因素。分析包括对噪声、噪声功率谱和调制传递函数的研究，作为投影数量 (N(proj))、剂量 (D(tot)) 和体素大小 (b(vox)) 的函数。结果结果揭示了在固定总剂量下图像噪声和 N(proj) 之间的非单调关系：对于所考虑的 CBCT 系统，由于 N(proj) <~200 范围内视图采样效应的减少，噪声随着 N(proj) 的增加而减少，高于该范围，由于电子噪声的增加，噪声随着 N(proj) 的增加而增加。视图采样效果被证明取决于对象的异质性，与 κ/f(β) 形式的幂律解剖杂波存在直接分析关系，并且单个噪声分量（σ(Q)、σ(E) 和 σ(view)）的通用模型证明与 N(proj)、D(tot) 和 b(vox) 中广泛范围内的测量结果一致。结论 这项工作以展示不同噪声成分（即量子噪声、电子噪声和视图采样噪声）的作用的方式阐明了 CBCT 噪声的相当基本的元素。对于具有平板探测器 (FPD) 的 CBCT 相当典型的配置，分析揭示了 N(proj) ~ 250-350 范围内的“最佳点”（即最小噪声），由于 FPD 中的电子噪声相对较高，N(proj) 比典型的多探测器 CT 低近一个数量级。该分析以包括物体（“杂波”）和成像链（包括探测器模糊和电子噪声的非理想性）方面的方式明确关联视图混叠和量子噪声，为 CBCT 系统设计和操作中普遍持有的直觉和启发法提供更严格的基础。
PURPOSE To investigate the effect of the number of projection views on image noise in cone-beam CT (CBCT) with a flat-panel detector. METHODS This fairly fundamental consideration in CBCT system design and operation was addressed experimentally (using a phantom presenting a uniform medium as well as statistically motivated "clutter") and theoretically (using a cascaded systems model describing CBCT noise) to elucidate the contributing factors of quantum noise (σ(Q)), electronic noise (σ(E)), and view aliasing (σ(view)). Analysis included investigation of the noise, noise-power spectrum, and modulation transfer function as a function of the number of projections (N(proj)), dose (D(tot)), and voxel size (b(vox)). RESULTS The results reveal a nonmonotonic relationship between image noise and N(proj) at fixed total dose: for the CBCT system considered, noise decreased with increasing N(proj) due to reduction of view sampling effects in the regime N(proj) <~200, above which noise increased with N(proj) due to increased electronic noise. View sampling effects were shown to depend on the heterogeneity of the object in a direct analytical relationship to power-law anatomical clutter of the form κ/f(β)--and a general model of individual noise components (σ(Q), σ(E), and σ(view)) demonstrated agreement with measurements over a broad range in N(proj), D(tot), and b(vox). CONCLUSIONS The work elucidates fairly basic elements of CBCT noise in a manner that demonstrates the role of distinct noise components (viz., quantum, electronic, and view sampling noise). For configurations fairly typical of CBCT with a flat-panel detector (FPD), the analysis reveals a "sweet spot" (i.e., minimum noise) in the range N(proj) ~ 250-350, nearly an order of magnitude lower in N(proj) than typical of multidetector CT, owing to the relatively high electronic noise in FPDs. The analysis explicitly relates view aliasing and quantum noise in a manner that includes aspects of the object ("clutter") and imaging chain (including nonidealities of detector blur and electronic noise) to provide a more rigorous basis for commonly held intuition and heurism in CBCT system design and operation.