Imaging Cells and Tissues with Refractive Index Radiology

Abstract

Can individual cells, including live cells, be imaged using hard x rays? Common wisdom until now required sophisticated staining techniques for this task. We show instead that individual cells and cell details can be detected in culture solution and tissues with no staining and no other contrast-enhancing preparation. The sample examined can be much thicker than for many other microscopy techniques without sacrificing the capability to resolve cells. The key factor in our approach is the use of a coherent synchrotron source and of contrast mechanisms based on the refractive index. The first successful tests were conducted on a variety of cell systems including skin and internal leaf cells, mouse neurons, rabbit fibroblast cells, and human tumor cells.

In vivo real-time vessel imaging and ex vivo 3D reconstruction of atherosclerotic plaque in apolipoprotein E-knockout mice using synchrotron radiation microscopy

“…Hwu's report demonstrated that the volume rendered 3D structure of the aorta could differentiate the individual cells [4]. However, the 3 D images in the present study were not yet at the same level as optical microscopy, with some blurring.…”

“…The present results are based on the differences in the refractive index, which enhance the conventional absorption contrast by X-ray sources with high coherence, which produces a sharp enhancement of the edge in the image [4]. As the previous report, a synchrotron X-ray used in the present study had unmonochromatic synchrotron beams and a simple detector system, differently from other synchrotron radiation systems, to implement this type of edge enhancement and to image extremely fine details [7].…”

“…Addition- ally, although classical methods, such as optical confocal microscopy or scanning microscopy, are accurate, they are restricted to the investigation of tissue volume within a depth of a few hundreds of micrometers because the illuminating radiation has a limited penetration ability. However, a hard X-ray microscopic imaging in the present study made it possible to examine thicker samples in a more realistic environment, which required no staining or other special preparations [4].…”

“…Previous report showed that refractive index imaging based on coherent X-rays using unmonochromatized synchrotron X-ray could produce clear images at the cell and sometimes subcellular level without staining [4]. Additionally, images could be taken in real time [4].…”

Potential for Imaging Engineered Tissues with X-Ray Phase Contrast

“…Individual neurons and fibroblasts could be identified within thin collagen gels in the absence of any exogenous contrast using propagation-based PC imaging. 56,62 Propagation-based CT has also been shown to allow the identification of single chondrocytes within cartilage lacuna. The volume of a single cell could be used to estimate cell density within a region of articular cartilage from CT images.…”