The feasibility of a piecewise-linear dynamic bowtie filter
The feasibility of a piecewise-linear dynamic bowtie filter
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DOI：
10.1118/1.4789630
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发表时间：
2013-03-01
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.;Pelc, Norbert J.
目的：CT中的患者前衰减器（或“蝴蝶结滤波器”）用于根据入射到患者上的X射线束的扇形角来调制通量。传统的静态蝴蝶结滤波器仅适用于非常普通的扫描和普通患者。作者提出了一种动态蝴蝶结的设计，可以产生一个随时间变化的分段线性衰减曲线。这种动态蝴蝶结可能会减少动态范围，剂量或散射，但在这项工作中，他们专注于它的能力，以减少动态范围，这可能是特别重要的系统采用光子计数detectors.Methods：动态蝴蝶结是由一组三角形楔。每个楔块独立移动，以产生时间相关的分段线性衰减曲线。进行领结的模拟以估计六个临床数据集中的动态范围减小。通过求解凸优化问题来确定动态领结的控制，并且使用Monte Carlo技术来估计剂量。射束硬化伪影也simulated.Results：动态范围减少的因素范围从2.4到27取决于身体的一部分研究。通过动态范围最小化目标，患者的剂量可以从6%降低到33%，同时保持峰值图像噪声。根据特定的剂量降低目标，可能进一步降低剂量。束硬化伪影抑制与两个通过algorithm.Conclusions：一个动态的蝴蝶结产生一个时间依赖性，分段线性衰减配置文件是可能的，并可用于调制的扫描仪的成像任务的通量。初始模拟显示动态范围大幅减小。其他几种应用也是可能的。(C)2013年美国医学物理学家协会。[http：//dx.doi.org/10.1118/1.4789630]
Purpose: The prepatient attenuator (or "bowtie filter") in CT is used to modulate the flux as a function of fan angle of the x-ray beam incident on the patient. Traditional, static bowtie filters are tailored only for very generic scans and for the average patient. The authors propose a design for a dynamic bowtie that can produce a time-dependent piecewise-linear attenuation profile. This dynamic bowtie may reduce dynamic range, dose or scatter, but in this work they focus on its ability to reduce dynamic range, which may be particularly important for systems employing photon-counting detectors.Methods: The dynamic bowtie is composed of a set of triangular wedges. Each wedge is independently moved in order to produce a time-dependent piecewise-linear attenuation profile. Simulations of the bowtie are conducted to estimate the dynamic range reduction in six clinical datasets. The control of the dynamic bowtie is determined by solving a convex optimization problem, and the dose is estimated using Monte Carlo techniques. Beam hardening artifacts are also simulated.Results: The dynamic range is reduced by factors ranging from 2.4 to 27 depending on the part of the body studied. With a dynamic range minimization objective, the dose to the patient can be reduced from 6% to 33% while maintaining peak image noise. Further reduction in dose may be possible with a specific dose reduction objective. Beam hardening artifacts are suppressed with a two-pass algorithm.Conclusions: A dynamic bowtie producing a time-dependent, piecewise-linear attenuation profile is possible and can be used to modulate the flux of the scanner to the imaging task. Initial simulations show a large reduction in dynamic range. Several other applications are possible. (C) 2013 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4789630]