Dose reduction using a dynamic, piecewise-linear attenuator
Dose reduction using a dynamic, piecewise-linear attenuator
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DOI：
10.1118/1.4862079
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发表时间：
2014-02-01
期刊：
影响因子：
3.8
通讯作者：
Pelc, Norbert J.
中科院分区：
文献类型：
--
作者：
Hsieh, Scott S.;Fleischmann, Dominik;Pelc, Norbert J.
目的：作者最近提出了一种动态的患者前x射线衰减器，能够根据每个患者和视角定制分段线性衰减曲线。该衰减器旨在通过重新分配通量来降低散射与初级比（SPR）、动态范围和剂量。在这项工作中，作者在模拟中测试了衰减器降低剂量和SPR的能力。方法：作者选择了四种临床应用，包括常规的胸腹全视野扫描，以及针对腹主动脉瘤和胰腺的靶向重建任务。原始数据通过图像体数据集的前向投影估计。通过求解一个凸优化问题来控制动态衰减器以降低剂量，同时保持峰值方差，假设对患者解剖结构有先验知识。在有针对性的重建任务中，增加了特定区域噪声的权重。以一个带有标准衰减器（或“领结滤波器”）的系统为参考，采用凸优化管电流调制（TCM）或标准TCM启发式方法。扫描噪声用解析法确定，剂量用蒙特卡罗模拟估计。散射也使用蒙特卡罗模拟估计。动态衰减器对患者定心的敏感性也通过每隔2cm移动腹部来检测。结果：与优化中医药的参考系统相比，使用动态衰减器可使常规扫描剂量降低约30%，靶向扫描剂量降低约50%。与通常在没有先验知识的情况下使用的中医启发式相比，常规扫描的剂量减少约为50%。动态衰减器提供了重新分配噪声和方差的能力，并产生比传统领结滤波器更均匀的噪声曲线。胸腔SPR也适度降低了10%，腹部降低了24%。使用动态衰减器成像对患者居中相对不敏感，显示腹部移动6厘米时峰值方差增加17%，而固定领结滤波器的峰值方差增加82%。结论：由多个楔形组成的动态患者前x射线衰减器能够实现大量的剂量降低和适度的SPR降低。(C) 2014年美国医学物理学家协会。
Purpose: The authors recently proposed a dynamic, prepatient x-ray attenuator capable of producing a piecewise-linear attenuation profile customized to each patient and viewing angle. This attenuator was intended to reduce scatter-to-primary ratio (SPR), dynamic range, and dose by redistributing flux. In this work the authors tested the ability of the attenuator to reduce dose and SPR in simulations.Methods: The authors selected four clinical applications, including routine full field-of-view scans of the thorax and abdomen, and targeted reconstruction tasks for an abdominal aortic aneurysm and the pancreas. Raw data were estimated by forward projection of the image volume datasets. The dynamic attenuator was controlled to reduce dose while maintaining peak variance by solving a convex optimization problem, assuming a priori knowledge of the patient anatomy. In targeted reconstruction tasks, the noise in specific regions was given increased weighting. A system with a standard attenuator (or "bowtie filter") was used as a reference, and used either convex optimized tube current modulation (TCM) or a standard TCM heuristic. The noise of the scan was determined analytically while the dose was estimated using Monte Carlo simulations. Scatter was also estimated using Monte Carlo simulations. The sensitivity of the dynamic attenuator to patient centering was also examined by shifting the abdomen in 2 cm intervals.Results: Compared to a reference system with optimized TCM, use of the dynamic attenuator reduced dose by about 30% in routine scans and 50% in targeted scans. Compared to the TCM heuristics which are typically used without a priori knowledge, the dose reduction is about 50% for routine scans. The dynamic attenuator gives the ability to redistribute noise and variance and produces more uniform noise profiles than systems with a conventional bowtie filter. The SPR was also modestly reduced by 10% in the thorax and 24% in the abdomen. Imaging with the dynamic attenuator was relatively insensitive to patient centering, showing a 17% increase in peak variance for a 6 cm shift of the abdomen, instead of an 82% increase in peak variance for a fixed bowtie filter.Conclusions: A dynamic prepatient x-ray attenuator consisting of multiple wedges is capable of achieving substantial dose reductions and modest SPR reductions. (C) 2014 American Association of Physicists in Medicine.