Interferometer-based Phase-contrast X-ray Computed Tomography of Colon Cancer Specimens

Three Dimensional Visualization of Human Cardiac Conduction Tissue in Whole Heart Specimens by High-Resolution Phase-Contrast CT Imaging Using Synchrotron Radiation

BACKGROUND

The feasibility of synchrotron radiation-based phase-contrast computed tomography (PCCT) for visualization of the atrioventricular (AV) conduction axis in human whole heart specimens was tested using four postmortem structurally normal newborn hearts obtained at autopsy.

METHODS

A PCCT imaging system at the beamline BL20B2 in a SPring-8 synchrotron radiation facility was used. The PCCT imaging of the conduction system was performed with "virtual" slicing of the three-dimensional reconstructed images. For histological verification, specimens were cut into planes similar to the PCCT images, then cut into 5-μm serial sections and stained with Masson's trichrome.

RESULTS

In PCCT images of all four of the whole hearts of newborns, the AV conduction axis was distinguished as a low-density structure, which was serially traceable from the compact node to the penetrating bundle within the central fibrous body, and to the branching bundle into the left and right bundle branches. This was verified by histological serial sectioning.

CONCLUSION

This is the first demonstration that visualization of the AV conduction axis within human whole heart specimens is feasible with PCCT.

Spontaneous brain tumor imaging of aged rat by crystal X-ray interferometer-based phase-contrast X-ray CT

Background

Crystal X-ray interferometer-based phase-contrast X-ray computed tomography (C-PCCT) enables the depiction of internal structures of biological tissue without contrast agents.

Purpose

To determine the advantage of this technique in visualizing detailed morphological structures of a rare spontaneous brain tumor in an aged rat.

Material and Methods

An aged rat’s spontaneous brain tumor was imaged by C-PCCT without contrast agent. Three-dimensional (3D) images of the tumor microvasculature were reconstructed and compared with pathological pictures.

Results

C-PCCT depicted the tumor’s various pathological features clearly, e.g. its cell density and vasculature, and blood clots caused by hemorrhaging and/or hematomas. The obtained images resembled pathological pictures with a magnification of ×20 and were used to reconstruct 3D images of the tumor vascularity up to approximately 26 µm in diameter.

Conclusion

Since C-PCCT is able to depict various pathological conditions, it might be useful for cancer research.

FMT-PCCT: hybrid fluorescence molecular tomography-x-ray phase-contrast CT imaging of mouse models

The implementation of hybrid fluorescence molecular tomography (FMT) and X-ray computed tomography (CT) has been shown to be a necessary development, not only for combining anatomical with functional and molecular contrast, but also for generating optical images of high accuracy. FMT affords highly sensitive 3-D imaging of fluorescence bio-distribution, but in stand-alone form it offers images of low resolution. It was shown that FMT accuracy significantly improves by considering anatomical priors from CT. Conversely, CT generally suffers from low soft tissue contrast. Therefore utilization of CT data as prior information in FMT inversion is challenging when different internal organs are not clearly differentiated. Instead, we combined herein FMT with emerging X-ray phase-contrast CT (PCCT). PCCT relies on phase shift differences in tissue to achieve soft tissue contrast superior to conventional CT. We demonstrate for the first time FMT-PCCT imaging of different animal models, where FMT and PCCT scans were performed in vivo and ex vivo, respectively. The results show that FMT-PCCT expands the potential of FMT in imaging lesions with otherwise low or no CT contrast, while retaining the cost benefits of CT and simplicity of hybrid device realizations. The results point to the most accurate FMT performance to date.

Enhanced renal image contrast by ethanol fixation in phase-contrast X-ray computed tomography

Phase-contrast X-ray imaging using a crystal X-ray interferometer can depict the fine structures of biological objects without the use of a contrast agent. To obtain higher image contrast, fixation techniques have been examined with 100% ethanol and the commonly used 10% formalin, since ethanol causes increased density differences against background due to its physical properties and greater dehydration of soft tissue. Histological comparison was also performed. A phase-contrast X-ray system was used, fitted with a two-crystal X-ray interferometer at 35 keV X-ray energy. Fine structures, including cortex, tubules in the medulla, and the vessels of ethanol-fixed kidney could be visualized more clearly than that of formalin-fixed tissues. In the optical microscopic images, shrinkage of soft tissue and decreased luminal space were observed in ethanol-fixed kidney; and this change was significantly shown in the cortex and outer stripe of the outer medulla. The ethanol fixation technique enhances image contrast by approximately 2.7-3.2 times in the cortex and the outer stripe of the outer medulla; the effect of shrinkage and the physical effect of ethanol cause an increment of approximately 78% and 22%, respectively. Thus, the ethanol-fixation technique enables the image contrast to be enhanced in phase-contrast X-ray imaging.

Mouse blood vessel imaging by in-line x-ray phase-contrast imaging

It is virtually impossible to observe blood vessels by conventional x-ray imaging techniques without using contrast agents. In addition, such x-ray systems are typically incapable of detecting vessels with diameters less than 200 microm. Here we show that vessels as small as 30 microm could be detected using in-line phase-contrast x-ray imaging without the use of contrast agents. Image quality was greatly improved by replacing resident blood with physiological saline. Furthermore, an entire branch of the portal vein from the main axial portal vein to the eighth generation of branching could be captured in a single phase-contrast image. Prior to our work, detection of 30 microm diameter blood vessels could only be achieved using x-ray interferometry, which requires sophisticated x-ray optics. Our results thus demonstrate that in-line phase-contrast x-ray imaging, using physiological saline as a contrast agent, provides an alternative to the interferometric method that can be much more easily implemented and also offers the advantage of a larger field of view. A possible application of this methodology is in animal tumor models, where it can be used to observe tumor angiogenesis and the treatment effects of antineoplastic agents.