Enhancement of soft-tissue contrast in cone-beam CT using an anti-scatter grid with a sparse sampling approach
Enhancement of soft-tissue contrast in cone-beam CT using an anti-scatter grid with a sparse sampling approach
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DOI：
10.1016/j.ejmp.2020.01.004
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发表时间：
2020-02-01
影响因子：
3.4
通讯作者：
Cho, Seungryong
中科院分区：
文献类型：
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作者：
Cho, Sanghoon;Lim, Sunho;Cho, Seungryong
目的：防散射栅格可显着抑制散射，从而提高射线照相中的图像对比度。然而，其在锥束 CT 中用于提高对比度噪声比 (CNR) 的积极应用并未成功，主要是由于与光子泊松统计相关的噪声增加。本文提出了一种稀疏视图扫描方法来解决上述问题。方法：与传统的锥束CT成像框架相比，该方法减少了投影数量并增加了每个投影的曝光量，以提高图像质量，而不会给患者带来额外的辐射剂量成本。对于稀疏视图数据的图像重建，采用了通过总变差（TV）最小化正则化的自适应最速下降凸集投影（ASD POCS）算法。通过使用 GATE 的模拟研究，在投影域中评估了各种散射条件下的对比度和 CNR。然后我们用 Catphan 模型评估了 CT 图像域的对比度、分辨率和图像均匀性。还采用了具有软组织结构的头部模型来演示实际应用。还实施了基于虚拟网格的散射估计和减少，以便与真实的防散射网格进行比较。结果：在投影域评估中，与虚拟网格相比，使用防散射网格时观察到对比度和 CNR 增强。在 CT 图像域中，所提出的方法产生了明显更高的对比度和低对比度结构的 CNR，并大大改善了图像均匀性。结论：我们已经表明，所提出的方法可以提供高质量的 CBCT 图像，特别是在用于图像引导的中性剂量下增加软组织的对比度。
Purpose: Anti-scatter grids suppress the scatter substantially thus improving image contrast in radiography. However, its active use in cone-beam CT for the purpose of improving contrast-to-noise ratio (CNR) has not been successful mainly due to the increased noise related to Poisson statistics of photons. This paper proposes a sparse-view scanning approach to address the above issue.Method: Compared to the conventional cone-beam CT imaging framework, the proposed method reduces the number of projections and increases exposure in each projection to enhance image quality without an additional cost of radiation dose to patients. For image reconstruction from sparse-view data, an adaptive-steepest-descent projection-onto-convex-sets (ASD POCS) algorithm regularized by total-variation (TV) minimization was adopted. Contrast and CNR with various scattering conditions were evaluated in projection domain by a simulation study using GATE. Then we evaluated contrast, resolution, and image uniformity in CT image domain with Catphan phantom. A head phantom with soft-tissue structures was also employed for demonstrating a realistic application. A virtual grid-based estimation and reduction of scatter has also been implemented for comparison with the real anti-scatter grid.Results: In the projection domain evaluation, contrast and CNR enhancement was observed when using an anti-scatter grid compared to the virtual grid. In the CT image domain, the proposed method produced substantially higher contrast and CNR of the low-contrast structures with much improved image uniformity.Conclusion: We have shown that the proposed method can provide high-quality CBCT images particularly with an increased contrast of soft-tissue at a neutral dose for image-guidance.