Zhang Ran, Qin Bin, Ge Yongshuai, Whiting Bruce, Li Ke, Villanueva Flordeliza, Chen Guang-Hong
Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI.
Department of Medicine, University of Pittsburgh, PA.
Proc SPIE Int Soc Opt Eng. 2016 Feb-Mar;9783. Epub 2016 Mar 22.
One of the most exciting aspects of the grating based x-ray differential phase contrast (DPC) acquisition method is the concurrent generation of the so-called dark field (DF) signal, along with the classical absorption signal and the novel DPC signal. The DF signal is associated with local distribution of small angle scatterers in an image object, while the absorption signal and DPC signal are often used to characterize the relatively uniform structure of the image object. Besides the endogenous image contrast, exogenous contrast media are often used in x-ray imaging to locally enhance the image signal. This paper proposes a potential contrast medium for DF signal enhancement: microbubbles (MBs). MBs have already been developed for clinical use in ultrasound imaging, and recent experimental studies have shown that MBs may also enhance the DF signal, although it remained unclear how the physical characteristics of the MBs quantitatively impact the DF signal. In this paper, a systematic study was performed to investigate the quantitative relationships between the DF signal and the following properties of MBs: size, concentration, shell thickness, size uniformity, and whether gold nanoparticles were attached. The experimental results demonstrated that, an increased MB size (about 4 microns) may generate a stronger DF signal for our DPC imaging system; additionally, a moderately increased shell thickness and the use of gold nanoparticles on the shell surface also resulted in further enhancement of the DF signal. These findings may provide critical information needed for using MBs as the contrast agent of x-ray DF imaging.
基于光栅的X射线差分相衬（DPC）采集方法最令人兴奋的一个方面是，在产生经典吸收信号和新型DPC信号的同时，还会同时产生所谓的暗场（DF）信号。DF信号与图像对象中小角度散射体的局部分布有关，而吸收信号和DPC信号通常用于表征图像对象相对均匀的结构。除了内源性图像对比度外，X射线成像中还经常使用外源性造影剂来局部增强图像信号。本文提出了一种用于增强DF信号的潜在造影剂：微泡（MBs）。MBs已被开发用于超声成像的临床应用，最近的实验研究表明，MBs也可能增强DF信号，尽管尚不清楚MBs的物理特性如何定量影响DF信号。本文进行了一项系统研究，以探讨DF信号与MBs的以下特性之间的定量关系：尺寸、浓度、壳厚度、尺寸均匀性以及是否附着金纳米颗粒。实验结果表明，对于我们的DPC成像系统，增加MB尺寸（约4微米）可能会产生更强的DF信号；此外，适度增加壳厚度以及在壳表面使用金纳米颗粒也会导致DF信号进一步增强。这些发现可能为将MBs用作X射线DF成像的造影剂提供所需的关键信息。
