Implementation and evaluation of an expectation maximization reconstruction algorithm for gamma emission breast tomosynthesis.
Implementation and evaluation of an expectation maximization reconstruction algorithm for gamma emission breast tomosynthesis.
复制标题
伽玛发射乳腺断层合成的期望最大化重建算法的实现和评估。
DOI：
10.1118/1.4764480
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发表时间：
2012
期刊：
影响因子：
3.8
通讯作者：
Williams,MarkB
中科院分区：
文献类型：
--
作者：
Gong,Zongyi;Klanian,Kelly;Patel,Tushita;Sullivan,Olivia;Williams,MarkB
目的我们正在开发一种双模态断层合成乳腺扫描仪，其中X射线透射断层合成和伽马发射断层合成在共同配置中对乳腺依次进行。在这两种模式中，从轻度压迫乳房的一侧在小于180°的角度范围内获得投影数据，导致不完整和不对称的采样。这项工作的目的是实施和评估的最大似然期望最大化（MLEM）重建算法的γ发射乳腺断层摄影合成（GEBT）。MethodsA结合蒙特卡罗模拟和幻影实验被用来测试的MLEM算法GEBT。该算法利用从X射线乳腺断层合成扫描获得的先验信息，部分补偿不完整的角度采样，并执行衰减校正（AC）和分辨率恢复（RR）。测量系统空间分辨率、图像伪影、病变对比度和信噪比（SNR）作为图像质量优值。为了测试重建算法的鲁棒性并评估校正技术对角度范围变化的相对影响，使用45°、90°和135°的采集角度范围进行了模拟和实验。为了进行比较，一个单一的投影包含相同的总计数作为完整的GEBT扫描也获得模拟平面乳腺cystigraphy.ResultsThe重建的GEBT图像的面内空间分辨率是独立的源位置内的重建体积和独立的采集角度范围。对于45°采集，深度维度（乳房压迫方向）的空间分辨率随着源深度的增加（距准直器表面的距离增加）而降低。将采集角度范围从45°增加到135°，既大大降低了这种深度依赖性，又将平均深度尺寸分辨率从10.8 mm提高到4.8 mm。135°采集导致近各向同性、空间均匀的3D分辨率，半峰全宽约为4.3 mm。背景非均匀性（杯状）伪影主要来自小角度范围采集的角度不完整性，但主要来自较大角度范围的伽马射线衰减。然而，如果同时应用先验信息正则化和AC，则可以在很大程度上消除背景伪影。通过AC和RR的组合，也可以显著减少随着病变深度增加而造成的病变体素值的人为降低。在使用可压缩明胶乳房体模的实验中，根据采集角度、伽马相机轨迹和病变位置，GEBT中的病变对比度和SNR分别比平面乳房造影高约2.6-8.8倍和2.3-5.6倍。此外，在平面乳腺X线摄影中观察到的随着病变深度的增加，病变对比度和SNR的强烈降低可以在很大程度上克服GEBT.ConclusionsThe作者已经证明了一种有前途的基于EM的重建方案用于GEBT。与平面乳腺造影相比，GEBT提供了上级和更低的位置依赖性病变对比度、病变SNR和空间分辨率，以及更准确的病变与背景活动浓度比量化。
PurposeWe are developing a dual modality tomosynthesis breast scanner in which x‐ray transmission tomosynthesis and gamma emission tomosynthesis are performed sequentially with the breast in a common configuration. In both modalities projection data are obtained over an angular range of less than 180° from one side of the mildly compressed breast resulting in incomplete and asymmetrical sampling. The objective of this work is to implement and evaluate a maximum likelihood expectation maximization (MLEM) reconstruction algorithm for gamma emission breast tomosynthesis (GEBT).MethodsA combination of Monte Carlo simulations and phantom experiments was used to test the MLEM algorithm for GEBT. The algorithm utilizes prior information obtained from the x‐ray breast tomosynthesis scan to partially compensate for the incomplete angular sampling and to perform attenuation correction (AC) and resolution recovery (RR). System spatial resolution, image artifacts, lesion contrast, and signal to noise ratio (SNR) were measured as image quality figures of merit. To test the robustness of the reconstruction algorithm and to assess the relative impacts of correction techniques with changing angular range, simulations and experiments were both performed using acquisition angular ranges of 45°, 90° and 135°. For comparison, a single projection containing the same total number of counts as the full GEBT scan was also obtained to simulate planar breast scintigraphy.ResultsThe in‐plane spatial resolution of the reconstructed GEBT images is independent of source position within the reconstructed volume and independent of acquisition angular range. For 45° acquisitions, spatial resolution in the depth dimension (the direction of breast compression) is degraded with increasing source depth (increasing distance from the collimator surface). Increasing the acquisition angular range from 45° to 135° both greatly reduces this depth dependence and improves the average depth dimension resolution from 10.8 to 4.8 mm. The 135° acquisition results in a near‐isotropic, spatially uniform 3D resolution of approximately 4.3 mm full width at half maximum. Background nonuniformity (cupping) artifacts arise primarily from angular incompleteness for small angular range acquisition but primarily from gamma ray attenuation at larger angular range. However, background artifacts can be largely eliminated if both prior information regularization and AC are applied. An artificial decrease in lesion voxel value with increasing lesion depth can also be substantially reduced through a combination of AC and RR. In experiments using compressible gelatin breast phantoms, lesion contrast and SNR are about 2.6–8.8 times and 2.3–5.6 times higher, respectively, in GEBT than in planar breast scintigraphy depending on the acquisition angle, the gamma camera trajectory, and the lesion location. In addition, the strong reduction in lesion contrast and SNR with increasing lesion depth that is observed in planar breast scintigraphy can be largely overcome in GEBT.ConclusionsThe authors have demonstrated a promising EM‐based reconstruction scheme for use in GEBT. Compared to planar breast scintigraphy GEBT provides superior and less position‐dependent lesion contrast, lesion SNR, and spatial resolution as well as more accurate quantification of lesion‐to‐background activity concentration ratio.
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影响因子：
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影响因子：
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DOI：
--
发表时间：
1996
期刊：
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影响因子：
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DOI：
10.1093/jnci/92.13.1081
发表时间：
2000-07-05
期刊：
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影响因子：
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作者：
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通讯作者：
White, E