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A prototype piecewise-linear dynamic attenuator

机译：原型分段 - 线性动态衰减器

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摘要

The piecewise-linear dynamic attenuator has been proposed as a mechanism in CT scanning for personalizing the x-ray illumination on a patient-and application-specific basis. Previous simulations have shown benefits in image quality, scatter, and dose objectives. We report on the first prototype implementation. This prototype is reduced in scale and speed and is integrated into a tabletop CT system with a smaller field of view (25 cm) and longer scan time (42s) compared to a clinical system. Stainless steel wedges were machined and affixed to linear actuators, which were in turn held secure by a frame built using rapid prototyping technologies. The actuators were computer-controlled, with characteristic noise of about 100 microns. Simulations suggest that in a clinical setting, the impact of actuator noise could lead to artifacts of only 1 HU. Ring artifacts were minimized by careful design of the wedges. A water beam hardening correction was applied and the scan was collimated to reduce scatter. We scanned a 16 cm water cylinder phantom as well as an anthropomorphic pediatric phantom. The artifacts present in reconstructed images are comparable to artifacts normally seen with this tabletop system. Compared to a flat-field reference scan, increased detectability at reduced dose is shown and streaking is reduced. Artifacts are modest in our images and further refinement is possible. Issues of mechanical speed and stability in the challenging clinical CT environment will be addressed in a future design.
机译：分段 - 线性动态衰减器已经提出作为CT扫描中的机制，用于在患者和特定于应用的基础上个性化X射线照明。以前的模拟显示了图像质量，散射和剂量目标中的好处。我们报告了第一个原型实施。与临床系统相比，该原型以尺度和速度降低，并集成到具有较小视野（25cm）和更长的扫描时间（42s）的桌面CT系统中。不锈钢楔形机加工并固定在线致动器，又通过使用快速原型技术构建的框架保持安全。执行器是计算机控制的，特征噪声约为100微米。模拟表明，在临床环境中，执行器噪音的影响可能导致仅为1胡的伪影。通过仔细设计楔子，最小化环形伪影。施加水束硬化校正，并准直扫描以减少散射。我们扫描了16厘米的水瓶幻影以及拟人的小儿幽灵。在重建的图像中存在的伪像与通常用该桌面系统看到的伪像相当。与平场参考扫描相比，示出了减少剂量的增加的可检测性，并且减少了条纹。在我们的图像中是适度的文物，并且可以进一步改进。在未来的设计中将解决挑战性临床CT环境中的机械速度和稳定性问题。

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