A prototype piecewise-linear dynamic attenuator.
A prototype piecewise-linear dynamic attenuator.
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DOI：
10.1088/0031-9155/61/13/4974
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发表时间：
2016-07-07
影响因子：
3.5
通讯作者：
Pelc NJ
中科院分区：
文献类型：
--
作者：
Hsieh SS;Peng MV;May CA;Shunhavanich P;Fleischmann D;Pelc NJ
分段线性动态衰减器已被提出作为CT扫描中的一种机制，用于在患者和应用特定的基础上个性化X射线照明。先前的模拟已经显示出在图像质量、散射和剂量目标方面的益处。我们报告的第一个原型实现。与临床系统相比，该原型在规模和速度上有所减小，并集成到具有更小视野（25 cm）和更长扫描时间（42 s）的桌面CT系统中。不锈钢楔子被加工并固定在线性执行器上，而线性执行器又由使用快速原型技术构建的框架固定。致动器由计算机控制，特征噪声约为100微米。模拟表明，在临床环境中，致动器噪声的影响可能导致仅1 HU的伪影。通过仔细设计楔形物，将环形伪影降至最低。应用了水射束硬化校正，并且扫描被准直以减少散射。我们扫描了一个16 cm的水筒体模以及一个拟人的儿科体模。重建图像中存在的伪影与该桌面系统通常看到的伪影相当。与平场参考扫描相比，显示出在降低的剂量下增加的可检测性，并且减少了条纹。在我们的图像中，伪影是适度的，进一步的改进是可能的。将在未来的设计中解决具有挑战性的临床CT环境中的机械速度和稳定性问题。
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 (42 s) 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.