Performance Evaluation of a Differential Phase-contrast Cone-beam (DPC-CBCT) System for Soft Tissue Imaging.
Performance Evaluation of a Differential Phase-contrast Cone-beam (DPC-CBCT) System for Soft Tissue Imaging.
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DOI：
10.1117/12.878492
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发表时间：
2011-03-16
期刊：
影响因子：
--
通讯作者：
Cai W
中科院分区：
文献类型：
--
作者：
Yu Y;Ning R;Cai W
微分相衬（DPC）技术有望成为X射线CT成像领域的下一个突破口。利用长期被忽视的X射线相位信息，微分相位衬度（DPC）技术有可能在不增加X射线剂量的情况下为我们提供更高对比度的CT扫描投影图像。虽然传统的基于吸收的X射线成像在区分软组织方面不是很有效，但是微分相位对比（DPC）作为一种新的方法在软组织成像中的对比噪声比（CNR）方面具有很大的潜力。为了验证和研究DPC技术在锥束CT成像方案中的应用，本实验室设计并构建了一种新型台式微焦点DPC锥束CT DPC-CBCT系统，用于软组织成像。DPC-CBCT系统由微焦点X射线管（焦斑8 μm）、高分辨率探测器、旋转体模保持器和两个光栅（相位光栅和分析光栅）组成。该检测器系统具有荧光屏、光纤耦合单元和有效像素间距为22.5微米的CMOS芯片。光学元件被对准以最小化意外的莫尔图案，并且系统参数，包括管电压（或等效的X射线光谱）、光栅之间的距离、源到物体的距离和物体到检测器的距离被选择为在旋转系统中应用是可行的。该系统进行了测试，两个简单的phantoms的性能评估。重建三维体积相位系数。在相同X射线剂量水平条件下，将该系统的性能与传统的吸收CT的对比噪声比（CNR）进行了比较。
Differential phase-contrast (DPC) technique is promising as the next breakthrough in the field of X-ray CT imaging. Utilizing the long ignored X-ray phase information, Differential phase-contrast (DPC) technique has the potential of providing us with projection images with higher contrast in a CT scan without increasing the X-ray dose. While traditional absorption-based X-ray imaging is not very efficient at differentiating soft tissues, differential phase-contrast (DPC) is promising as a new method to boast the quality of the CT reconstruction images in term of contrast noise ratio (CNR) in soft tissue imaging. In order to validate and investigate the use of DPC technique in cone-beam CT imaging scheme, a new bench-top micro-focus DPC-based cone-beam computed tomography DPC-CBCT system has been designed and constructed in our lab for soft tissue imaging. The DPC-CBCT system consists of a micro-focus X-ray tube (focal spot 8 μm), a high-resolution detector, a rotating phantom holder and two gratings, i.e. a phase grating and an analysis. The detector system has a phosphor screen, an optical fiber coupling unit and a CMOS chip with an effective pixel pitch of 22.5 microns. The optical elements are aligned to minimize unexpected moiré patterns, and system parameters, including tube voltage (or equivalently X-ray spectrum), distances between gratings, source-to-object distance and object-to-detector distance are chosen as practicable to be applied in a rotating system. The system is tested with two simple phantoms for performance evaluation. 3-D volumetric phase-coefficients are reconstructed. The performance of the system is compared with conventional absorption-based CT in term of contrast noise ratio (CNR) under the condition of equal X-ray dose level.
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