Synchrotron microangiography with no contrast agent

Spherical alveolar shapes in live mouse lungs

Understanding how the alveolar mechanics work in live lungs is essential for comprehending how the lung behaves during breathing. Due to the lack of appropriate imaging tools, previous research has suggested that alveolar morphologies are polyhedral rather than spherical based on a 2D examination of alveoli in fixed lungs. Here, we directly observe high-resolution 3D alveoli in live mice lungs utilizing synchrotron x-ray microtomography to show spherical alveolar morphologies from the live lungs. Our measurements from x-ray microtomography show high sphericity, low packing density, big alveolar size, and low osmotic pressure, indicating that spherical alveolar morphologies are natural in living lungs. The alveolar packing fraction is quite low in live lungs, where the spherical alveoli would behave like free bubbles, while the confinement of alveolar clusters in fixed lungs would lead to significant morphological deformations of the alveoli appearing polyhedral. Direct observations of the spherical alveolar shapes will help understand and treat lung disease and ventilation.

Numerical simulation of novel concept 4D cardiac microtomography for small rodents based on all-optical Thomson scattering X-ray sources

Accurate dynamic three-dimensional (4D) imaging of the heart of small rodents is required for the preclinical study of cardiac biomechanics and their modification under pathological conditions, but technological challenges are met in laboratory practice due to the very small size and high pulse rate of the heart of mice and rats as compared to humans. In 4D X-ray microtomography (4D μCT), the achievable spatio-temporal resolution is hampered by limitations in conventional X-ray sources and detectors. Here, we propose a proof-of-principle 4D μCT platform, exploiting the unique spatial and temporal features of novel concept, all-optical X-ray sources based on Thomson scattering (TS). The main spatial and spectral properties of the photon source are investigated using a TS simulation code. The entire data acquisition workflow has been also simulated, using a novel 4D numerical phantom of a mouse chest with realistic intra- and inter-cycle motion. The image quality of a typical single 3D time frame has been studied using Monte Carlo simulations, taking into account the effects of the typical structure of the TS X-ray beam. Finally, we discuss the perspectives and shortcomings of the proposed platform.

Synchrotron radiation micro-tomography for high-resolution neurovascular network morphology investigation

There has been increasing interest in using high-resolution micro-tomography to investigate the morphology of neurovascular networks in the central nervous system, which remain difficult to characterize due to their microscopic size as well as their delicate and complex 3D structure. Synchrotron radiation X-ray imaging, which has emerged as a cutting-edge imaging technology with a high spatial resolution, provides a novel platform for the non-destructive imaging of microvasculature networks at a sub-micrometre scale. When coupled with computed tomography, this technique allows the characterization of the 3D morphology of vasculature. The current review focuses on recent progress in developing synchrotron radiation methodology and its application in probing neurovascular networks, especially the pathological changes associated with vascular abnormalities in various model systems. Furthermore, this tool represents a powerful imaging modality that improves our understanding of the complex biological interactions between vascular function and neuronal activity in both physiological and pathological states.

Q&A: Why use synchrotron x-ray tomography for multi-scale connectome mapping?

To understand how information flows and is used in the human brain, we must map neural structures at all levels, providing visualizations similar to those of Google Earth for continents, countries, cities, and streets. Unfortunately, the imaging and processing techniques currently used in connectomics projects cannot achieve complete mapping for the brains of large animals within the timespan of a typical research career. However, feasible improvements in x-ray imaging would change this situation. This Q&A discusses synchrotron x-ray tomography, an exciting new approach for in situ mapping of whole-brain wiring diagrams at multiple levels of spatial resolution.

Synchrotron X-ray imaging of pulmonary alveoli in respiration in live intact mice

Despite nearly a half century of studies, it has not been fully understood how pulmonary alveoli, the elementary gas exchange units in mammalian lungs, inflate and deflate during respiration. Understanding alveolar dynamics is crucial for treating patients with pulmonary diseases. In-vivo, real-time visualization of the alveoli during respiration has been hampered by active lung movement. Previous studies have been therefore limited to alveoli at lung apices or subpleural alveoli under open thorax conditions. Here we report direct and real-time visualization of alveoli of live intact mice during respiration using tracking X-ray microscopy. Our studies, for the first time, determine the alveolar size of normal mice in respiration without positive end expiratory pressure as 58 ± 14 (mean ± s.d.) μm on average, accurately measured in the lung bases as well as the apices. Individual alveoli of normal lungs clearly show heterogeneous inflation from zero to ~25% (6.7 ± 4.7% (mean ± s.d.)) in size. The degree of inflation is higher in the lung bases (8.7 ± 4.3% (mean ± s.d.)) than in the apices (5.7 ± 3.2% (mean ± s.d.)). The fraction of the total tidal volume allocated for alveolar inflation is 34 ± 3.8% (mean ± s.e.m). This study contributes to the better understanding of alveolar dynamics and helps to develop potential treatment options for pulmonary diseases.

Image alignment for tomography reconstruction from synchrotron X-ray microscopic images

A synchrotron X-ray microscope is a powerful imaging apparatus for taking high-resolution and high-contrast X-ray images of nanoscale objects. A sufficient number of X-ray projection images from different angles is required for constructing 3D volume images of an object. Because a synchrotron light source is immobile, a rotational object holder is required for tomography. At a resolution of 10 nm per pixel, the vibration of the holder caused by rotating the object cannot be disregarded if tomographic images are to be reconstructed accurately. This paper presents a computer method to compensate for the vibration of the rotational holder by aligning neighboring X-ray images. This alignment process involves two steps. The first step is to match the “projected feature points” in the sequence of images. The matched projected feature points in the - plane should form a set of sine-shaped loci. The second step is to fit the loci to a set of sine waves to compute the parameters required for alignment. The experimental results show that the proposed method outperforms two previously proposed methods, Xradia and SPIDER. The developed software system can be downloaded from the URL, http://www.cs.nctu.edu.tw/~chengchc/SCTA or http://goo.gl/s4AMx.

Tracking X-ray microscopy for alveolar dynamics in live intact mice

Here we report a tracking X-ray microscopy (TrXM) as a novel methodology by using upper right lung apices alveoli in live intact mice. By enabling tracking of individual alveolar movements during respiration, TrXM identifies alveolar dynamics: individual alveoli in the upper lung apices show a small size increment as 4.9 ± 0.4% (mean ± s.e.m.) during respiration while their shapes look almost invariant. TrXM analysis in alveolar dynamics would be significant for better understanding of alveolar-based diseases, for instance, ventilator induced lung injury (VILI) in acute respiratory distress syndrome (ARDS).

Gold nanoparticle contrast agents in advanced X-ray imaging technologies

Recently, there has been significant progress in the field of soft- and hard-X-ray imaging for a wide range of applications, both technically and scientifically, via developments in sources, optics and imaging methodologies. While one community is pursuing extensive applications of available X-ray tools, others are investigating improvements in techniques, including new optics, higher spatial resolutions and brighter compact sources. For increased image quality and more exquisite investigation on characteristic biological phenomena, contrast agents have been employed extensively in imaging technologies. Heavy metal nanoparticles are excellent absorbers of X-rays and can offer excellent improvements in medical diagnosis and X-ray imaging. In this context, the role of gold (Au) is important for advanced X-ray imaging applications. Au has a long-history in a wide range of medical applications and exhibits characteristic interactions with X-rays. Therefore, Au can offer a particular advantage as a tracer and a contrast enhancer in X-ray imaging technologies by sensing the variation in X-ray attenuation in a given sample volume. This review summarizes basic understanding on X-ray imaging from device set-up to technologies. Then this review covers recent studies in the development of X-ray imaging techniques utilizing gold nanoparticles (AuNPs) and their relevant applications, including two- and three-dimensional biological imaging, dynamical processes in a living system, single cell-based imaging and quantitative analysis of circulatory systems and so on. In addition to conventional medical applications, various novel research areas have been developed and are expected to be further developed through AuNP-based X-ray imaging technologies.

X-ray intravital microscopy for functional imaging in rat hearts using synchrotron radiation coronary microangiography

An X-ray intravital microscopy technique was developed to enable in vivo visualization of the coronary, cerebral, and pulmonary arteries in rats without exposure of organs and with spatial resolution in the micrometer range and temporal resolution in the millisecond range. We have refined the system continually in terms of the spatial resolution and exposure time. X-rays transmitted through an object are detected by an X-ray direct-conversion type detector, which incorporates an X-ray SATICON pickup tube. The spatial resolution has been improved to 6 μm, yielding sharp images of small arteries. The exposure time has been shortened to around 2 ms using a new rotating-disk X-ray shutter, enabling imaging of beating rat hearts. Quantitative evaluations of the X-ray intravital microscopy technique were extracted from measurements of the smallest-detectable vessel size and detection of the vessel function. The smallest-diameter vessel viewed for measurements is determined primarily by the concentration of iodinated contrast material. The iodine concentration depends on the injection technique. We used ex vivo rat hearts under Langendorff perfusion for accurate evaluation. After the contrast agent is injected into the origin of the aorta in an isolated perfused rat heart, the contrast agent is delivered directly into the coronary arteries with minimum dilution. The vascular internal diameter response of coronary arterial circulation is analyzed to evaluate the vessel function. Small blood vessels of more than about 50 μm diameters were visualized clearly at heart rates of around 300 beats/min. Vasodilation compared to the control was observed quantitatively using drug manipulation. Furthermore, the apparent increase in the number of small vessels with diameters of less than about 50 μm was observed after the vasoactive agents increased the diameters of invisible small blood vessels to visible sizes. This technique is expected to offer the potential for direct investigation of mechanisms of vascular dysfunctions.

Growth patterns for acervuli in human pineal gland

Acervuli are calcified concretions in the pineal gland (PG). Particularly interesting are their incidence and size, which are believed to affect neurological disorders and many physiological functions of PG such as regulating circadian rhythm. Despite long investigations for a century, detailed growth mechanism of acervuli has yet to be studied. Here we study the growth morphology of acervuli in human PGs by a direct visualization in 3-dimension (3-D) using a synchrotron X-ray imaging method. For an entire PG, non-aggregated acervuli show Gaussian distribution in size with 47±28 µm. The 3-D volume rendered images of acervuli reveal that the bumpy surfaces developed by lamination result in the mulberry-like structure. In addition, coalescence of multiple acervuli leads to large-scale lamination on the whole aggregate. We suggest a novel hypothesis on the growth patterns of acervuli by their nucleation density (N_d): i) mulberry-like structure at low N_d, and ii) large-scale lamination on an aggregate at high N_d.

Gold: a versatile tool for in vivo imaging

Imaging for diagnostics or for evaluating the efficacy of a particular drug constitutes a key challenge, and a topical area of research in nanomedicine. There has been a tremendous effort devoted to the evaluation of a variety of contrast agents, and gold nanomaterials due to their inherent and geometrically induced optical properties, have offered significant potential for in vivo imaging. The gold based nanostructures that are most commonly employed for biological imaging include nano-spheres, -rods, -shells, -cages and -stars. This feature article provides an overview of the current state of research in utilizing these gold nano-architectures in imaging, with particular emphasis on modalities such as two-photon luminescence, computed tomography, optical coherence tomography, near infrared and photoacoustic imaging.

X-ray imaging of tumor growth in live mice by detecting gold-nanoparticle-loaded cells

We show that sufficient concentrations of gold nanoparticles produced by an original synthesis method in EMT-6 and CT-26 cancer cells make it possible to detect the presence, necrosis and proliferation of such cells after inoculation in live mice. We first demonstrated that the nanoparticles do not interfere with the proliferation process. Then, we observed significant differences in the tumor evolution and the angiogenesis process after shallow and deep inoculation. A direct comparison with pathology optical images illustrates the effectiveness of this approach.

X-ray phase contrast for CO2 microangiography

We demonstrate a laboratory method for imaging small blood vessels using x-ray propagation-based phase-contrast imaging and carbon dioxide (CO(2)) gas as a contrast agent. The limited radiation dose in combination with CO(2) being clinically acceptable makes the method promising for small-diameter vascular visualization. We investigate the possibilities and limitations of the method for small-animal angiography and compare it with conventional absorption-based x-ray angiography. Photon noise in absorption-contrast imaging prevents visualization of blood vessels narrower than 50 µm at the highest radiation doses compatible with living animals, whereas our simulations and experiments indicate the possibility of visualizing 20 µm vessels at radiation doses as low as 100 mGy. Experimental computed tomography of excised rat kidney shows blood vessels of diameters down to 60 µm with improved image quality compared to absorption-based methods. With our present prototype x-ray source, the acquisition time for a tomographic dataset is approximately 1 h, which is long compared to the 1-20 min common for absorption-contrast micro-CT systems. Further development of the liquid-metal-jet microfocus x-ray sources used here and high-resolution x-ray detectors shows promise to reduce exposure times and make this high-resolution method practical for imaging of living animals.

Gold nanoparticles as high-resolution X-ray imaging contrast agents for the analysis of tumor-related micro-vasculature

BACKGROUND

Angiogenesis is widely investigated in conjunction with cancer development, in particular because of the possibility of early stage detection and of new therapeutic strategies. However, such studies are negatively affected by the limitations of imaging techniques in the detection of microscopic blood vessels (diameter 3-5 μm) grown under angiogenic stress. We report that synchrotron-based X-ray imaging techniques with very high spatial resolution can overcome this obstacle, provided that suitable contrast agents are used.

RESULTS

We tested different contrast agents based on gold nanoparticles (AuNPs) for the detection of cancer-related angiogenesis by synchrotron microradiology, microtomography and high resolution X-ray microscopy. Among them only bare-AuNPs in conjunction with heparin injection provided sufficient contrast to allow in vivo detection of small capillary species (the smallest measured lumen diameters were 3-5 μm). The detected vessel density was 3-7 times higher than with other nanoparticles. We also found that bare-AuNPs with heparin allows detecting symptoms of local extravascular nanoparticle diffusion in tumor areas where capillary leakage appeared.

CONCLUSIONS

Although high-Z AuNPs are natural candidates as radiology contrast agents, their success is not guaranteed, in particular when targeting very small blood vessels in tumor-related angiography. We found that AuNPs injected with heparin produced the contrast level needed to reveal--for the first time by X-ray imaging--tumor microvessels with 3-5 μm diameter as well as extravascular diffusion due to basal membrane defenestration. These results open the interesting possibility of functional imaging of the tumor microvasculature, of its development and organization, as well as of the effects of anti-angiogenic drugs.

Complete microscale profiling of tumor microangiogenesis: a microradiological methodology reveals fundamental aspects of tumor angiogenesis and yields an array of quantitative parameters for its characterization

Complete profiling would substantially facilitate the fundamental understanding of tumor angiogenesis and of possible anti-angiogenesis cancer treatments. We developed an integrated synchrotron-based methodology with excellent performances: detection of very small vessels by high spatial resolution (~1 μm) and nanoparticle contrast enhancement, in vivo dynamics investigations with high temporal resolution (~1 ms), and three-dimensional quantitative morphology parametrization by computer tracing. The smallest (3-10 μm) microvessels were found to constitute >80% of the tumor vasculature and exhibit many structural anomalies. Practical applications are presented, including vessel microanalysis in xenografted tumors, monitoring the effects of anti-angiogenetic agents and in vivo detection of tumor vascular rheological properties.

Altered branching patterns of Purkinje cells in mouse model for cortical development disorder

Disrupted cortical cytoarchitecture in cerebellum is a typical pathology in reeler. Particularly interesting are structural problems at the cellular level: dendritic morphology has important functional implication in signal processing. Here we describe a combinatorial imaging method of synchrotron X-ray microtomography with Golgi staining, which can deliver 3-dimensional(3-D) micro-architectures of Purkinje cell(PC) dendrites, and give access to quantitative information in 3-D geometry. In reeler, we visualized in 3-D geometry the shape alterations of planar PC dendrites (i.e., abnormal 3-D arborization). Despite these alterations, the 3-D quantitative analysis of the branching patterns showed no significant changes of the 77 ± 8° branch angle, whereas the branch segment length strongly increased with large fluctuations, comparing to control. The 3-D fractal dimension of the PCs decreased from 1.723 to 1.254, indicating a significant reduction of dendritic complexity. This study provides insights into etiologies and further potential treatment options for lissencephaly and various neurodevelopmental disorders.

Potential for imaging engineered tissues with X-ray phase contrast

As the field of tissue engineering advances, it is crucial to develop imaging methods capable of providing detailed three-dimensional information on tissue structure. X-ray imaging techniques based on phase-contrast (PC) have great potential for a number of biomedical applications due to their ability to provide information about soft tissue structure without exogenous contrast agents. X-ray PC techniques retain the excellent spatial resolution, tissue penetration, and calcified tissue contrast of conventional X-ray techniques while providing drastically improved imaging of soft tissue and biomaterials. This suggests that X-ray PC techniques are very promising for evaluation of engineered tissues. In this review, four different implementations of X-ray PC imaging are described and applications to tissues of relevance to tissue engineering reviewed. In addition, recent applications of X-ray PC to the evaluation of biomaterial scaffolds and engineered tissues are presented and areas for further development and application of these techniques are discussed. Imaging techniques based on X-ray PC have significant potential for improving our ability to image and characterize engineered tissues, and their continued development and optimization could have significant impact on the field of tissue engineering.

Real time observation of mouse fetal skeleton using a high resolution X-ray synchrotron

The X-ray synchrotron is quite different from conventional radiation sources. This technique may expand the capabilities of conventional radiology and be applied in novel manners for special cases. To evaluate the usefulness of X-ray synchrotron radiation systems for real time observations, mouse fetal skeleton development was monitored with a high resolution X-ray synchrotron. A non-monochromatized X-ray synchrotron (white beam, 5C1 beamline) was employed to observe the skeleton of mice under anesthesia at embryonic day (E)12, E14, E15, and E18. At the same time, conventional radiography and mammography were used to compare with X-ray synchrotron. After synchrotron radiation, each mouse was sacrificed and stained with Alizarin red S and Alcian blue to observe bony structures. Synchrotron radiation enabled us to view the mouse fetal skeleton beginning at gestation. Synchrotron radiation systems facilitate real time observations of the fetal skeleton with greater accuracy and magnification compared to mammography and conventional radiography. Our results show that X-ray synchrotron systems can be used to observe the fine structures of internal organs at high magnification.

Synchrotron X-ray bioimaging of bone regeneration by artificial bone substitute of MegaGen Synthetic Bone and hyaluronate hydrogels

Synchrotron X-ray bioimaging was successfully carried out to observe bone regeneration by a novel artificial bone substitute of bioactive MegaGen Synthetic Bone (MGSB) and hyaluronate (HA) hydrogels. A biphasic calcium phosphate of MGSB was prepared by chemical precipitation method, with a porous spherical morphology. On the basis of the fact that HA plays important roles in bone regeneration and promotes the differentiation, vascularization, and migration of stem cells, HA-cystamine (CYS) hydrogels with cleavable disulfide linkages were prepared to supply HA continuously for effective bone regeneration by their controlled degradation in vivo. Among seven different samples using Bio-OSS®, MGSB, and/or several kinds of HA hydrogels, MGSB/HA-CYS hydrogels resulted in the most significant bone regeneration in the calvarial critical bone defect of New Zealand white rabbits. Histological and histomorphometric analyses revealed that the bone regeneration by MGSB/HA-CYS hydrogels was as high as 43%, occupying 71% of the bone defect area with MGSB in the form of a calvarial bone plate in 4 weeks. After that, MGSB was bioabsorbed and replaced gradually with regenerated bones as observed in 8 weeks. Synchrotron X-ray imaging clearly confirmed the effective bone regeneration by MGSB/HA-CYS hydrogels, showing three-dimensional micron-scale morphologies of regenerated bones interconnected with MGSB. In addition, sequential nondestructive synchrotron X-ray tomographic analysis results from anterior to posterior of the samples were well matched with the histomorphometric analysis results. The clinically feasible artificial bone substitutes of MGSB/HA-CYS hydrogels will be investigated further for various bone tissue engineering applications using the synchrotron X-ray bioimaging systems.

Lung cancer and angiogenesis imaging using synchrotron radiation

Early detection of lung cancer is the key to a cure, but a difficult task using conventional x-ray imaging. In the present study, synchrotron radiation in-line phase-contrast imaging was used to study lung cancer. Lewis lung cancer and 4T1 breast tumor metastasis in the lung were imaged, and the differences were clearly shown in comparison to normal lung tissue. The effect of the object-detector distance and the energy level on the phase-contrast difference was investigated and found to be in good agreement with the theory of in-line phase-contrast imaging. Moreover, 3D image reconstruction of lung tumor angiogenesis was obtained for the first time using a contrast agent, demonstrating the feasibility of micro-angiography with synchrotron radiation for imaging tumor angiogenesis deep inside the body.

Enhancement of irradiation effects on cancer cells by cross-linked dextran-coated iron oxide (CLIO) nanoparticles

We investigated iron oxide nanoparticles with two different surface modifications, dextran coating and cross-linked dextran coating, showing that their different internalization affects their capability to enhance radiation damage to cancer cells. The internalization was monitored with an ultrahigh resolution transmission x-ray microscope (TXM), indicating that the differences in the particle surface charge play an essential role and dominate the particle-cell interaction. We found that dextran-coated iron oxide nanoparticles cannot be internalized by HeLa and EMT-6 cells without being functionalized with amino groups (the cross-linked dextran coating) that modify the surface potential from -18 mV to 13.4 mV. The amount of cross-linked dextran-coated iron oxide nanoparticles uptaken by cancer cells reached its maximum, 1.33 x 10(9) per HeLa cell, when the co-culture concentration was 40 microg Fe mL(-1) or more. Standard tests indicated that these internalized nanoparticles increased the damaging effects of x-ray irradiation, whereas they are by themselves biocompatible. These results could lead to interesting therapy applications; furthermore, iron oxide also produces high contrast for magnetic resonance imaging (MRI) in the diagnosis and therapy stages.

Phase contrast microradiography of mouse lung using synchrotron X-ray: correlation with optical microscopy

PURPOSE

The purpose of this study is to evaluate the feasibility of phase contrast X-ray microtomography and microradiography, using a polychromatic synchrotron X-ray, for analysis of the mouse lung microstructure.

MATERIALS AND METHODS

Normal mice were used for experiments. Some of the mouse lungs were prepared by the lung fixation-inflation method. The resulting sponge-like inflated lung samples were used for microtomography. The remaining mouse lungs were cut into 10 microm sections and were used for microradiography and optical microscopic correlation. The experiments on mouse lung samples were performed at the 7B2 beamline of the Pohang Light Source in Korea.

RESULTS

Phase contrast X-ray microtomography of inflated lung samples showed individual alveolar structure on 3-D reconstruction. Phase contrast microradiographs of thin lung samples showed microstructure of lung, such as alveoli and bronchioles, and were well correlated with optical microscopic images.

CONCLUSIONS

The results indicate that the phase contrast X-ray microtomography and microradiography using polychromatic synchrotron X-ray is feasible for evaluation of microstructure of the lung.

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.

A new method for investigation of the hair shaft: hard X-ray microscopy with a 90-nm spatial resolution

Various methods have been used to investigate the hair shaft. In the ultrastructural hair field, scanning and transmission electron microscopies are widely used investigative methods, but they have some technical limitations. Recently, X-ray microscopes with sub-micron spatial resolution have emerged as useful instruments because they offer a unique opportunity to observe the interior of an undamaged sample in greater detail. In this report, we examined damaged hair shaft tips using hard X-ray microscopy with a 90 nm spatial resolution. The results of this study suggest that hard X-ray microscopy is an alternative investigative method for hair morphology studies.

Ex vivo imaging of basal cell carcinoma using synchrotron phase-contrast X-ray microscopy

BACKGROUND/AIMS

There is a need for development of non-invasive methods to improve early diagnosis and screening of suspected malignant lesions. Phase-contrast X-ray microscopy (PCXM) has potential to reveal the structures inside soft tissues, and fine details can be observed without any staining or contrast-enhancing cell preparation. We aimed to investigate the possibility that PCXM can be used to explore the microscopic details of basal cell carcinoma (BCC).

METHODS

Paraffin blocks of specimens from patients with basal cell carcinoma were cut with 30 microm thickness for PCXM imaging. Experiments were performed at the International Consortium of Phase Contrast Imaging and Radiology (ICPCIR) (7B2) beamline of the Pohang light source in Korea. The PCXM images were achieved by using coherent hard X-rays from a synchrotron source with no monochromatization.

RESULTS

We could obtain images with clear edge enhancement by PCXM. The images taken with this technique showed clear anatomic details of organelles in normal skin such as epidermis, dermis and skin appendages. Most of cancerous lesions were clearly differentiated from adjacent normal tissues and the images closely corresponded to those obtained with low-magnification optical microscopy.

CONCLUSION

In this pilot study, we successfully demonstrated that synchrotron PCXM could be used for radiological imaging of BCC with great anatomic details.

Imaging of renal and prostate carcinoma with refractive index radiology

AIM

Having better edge enhancement and penetrating power, refractive index radiology is suitable for the imaging of weakly absorbing objects such as tissue specimens. In this study the potential of refractive index radiology was evaluated for the imaging of renal cell carcinoma (RCC) and prostate cancer (PCA).

METHODS

Specimens were cut in 3 mm and 4 microm thickness for X-ray radiology and hematoxylin and eosin (HE) staining, respectively. Radiographic images of RCC and PCA were obtained using the synchrotron hard X-rays from the 7B2 beam-line of the Pohang Light Source (PLS). The imaging technique applied was phase-contrast radiology based on the refraction enhancement mechanism. The resulting radiographic images were analyzed in correlation with those of optical microscopy.

RESULTS

Using unmonochromatized hard X-rays, it was possible to obtain images with clear edge enhancement and relatively large field of view (6 cm x 6 cm). Even with overlapping signals from thick samples (more than 700-fold thicker than microscopic images), radiographic images clearly showed histological information of organelles in normal kidney such as glomeruli, tubules, and collecting ducts. Histological information of RCC including tumor subtypes and minute changes such as cystic degeneration could be identified without difficulty. The radiographic images of the prostate were comparable with those of low magnification optical microscopy, providing good visualization of normal microstructures such as adenoma, smooth muscle, and normal glands, or differentiation of tiny tumors from surrounding normal tissues.

CONCLUSIONS

These results suggest the potential of refractive index radiology to provide a new way of imaging biological tissues with low absorption contrast such as RCC and PCA.

Phase contrast radiography of Lewy bodies in Parkinson disease

Parkinson's disease (PD), defined as a neurodegenerative disorder, is characterized by the loss of dopaminergic neurons and the presence of Lewy bodies in neurons. Morphological study of Lewy bodies is important to identify the causes and the processes of PD. Here, we investigate a possibility of phase contrast radiography using coherent synchrotron X-rays to explore the microscopic details of Lewy bodies in thick (approximately 3 mm) midbrain tissues. Autopsied midbrain tissues of a PD patient were sliced in 3 mm thickness and then examined using synchrotron X-rays from the 7B2 beamline of the Pohang Light Source. Refraction-enhanced phase contrast radiography and microtomography were adopted to identify dark core and dim edge of Lewy bodies in neurons. The morphology of Lewy bodies was clearly revealed by the phase contrast radiography in very thick (3 mm) midbrain tissues without any staining treatment. Three-dimensional volume rendered microtomography of the autopsied midbrain tissues demonstrates striking evidence that several Lewy bodies are agglomerated by dim edges in a neuron. We suggest that the phase contrast radiography could be a useful tool to morphologically investigate the causes or the processes in PD.

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

BACKGROUND

To examine the pathophysiology of atherosclerosis, imaging the vascular wall and pathology without tissue damage is required. We used the unmonochromatized synchrotron X-ray to acquire in vivo real-time and ex vivo images of atherosclerotic lesions in apo E-knockout mice without contrast agents or staining.

METHODS

In the five apo E-knockout mice (apo E-/-, 12, 24, 32, 48, 62-week-old, 3 males) and age/sex matched five wild type mice on cow diets, we acquired in vivo real-time images of thoracic aorta without contrast agents and then, the central arterial trees were dissected intact. Ex vivo synchrotron images with tomographic reconstruction were done and compared with the corresponding pathology.

RESULTS

For all living animals, in vivo real-time images of thoracic aorta could be acquired without contrast agents but could not identify the atherosclerotic lesions. Ex vivo images accurately determined aortic wall and atherosclerotic plaque without staining in comparison to histopathology according to the AHA classification (r=0.84, p<0.001). The volume rendered 3 D images of plaque showed central cholesterol clefts as matched with optical images.

CONCLUSIONS

The combination of synchrotron enhanced X-ray microscopy and genetically engineered hyperlipidemic animals would be a useful tool to investigate the changes of advanced atherosclerotic lesions.

In vivo X-ray angiography in the mouse brain using synchrotron radiation

BACKGROUND AND PURPOSE

We, for the first time, performed in vivo x-ray angiography in the mouse brain using SPring-8, a third-generation synchrotron radiation facility.

METHODS

A thin PE-50 tube was placed in the unilateral external carotid artery in adult male C57BL/6J mice. While maintaining the blood flow in the internal carotid artery, 33 muL of contrast agent was injected and then selective angiography of the hemisphere was performed.

RESULTS

The average diameters of cerebral artery were as follows: 142.5+/-7.90 microm in middle cerebral artery, 138.3+/-9.35 microm in anterior cerebral artery, 120.5+/-5.53 microm in posterior cerebral artery, and 162.6+/-10.87 microm in internal carotid artery (n=5). To demonstrate the changes in diameter, we induced hypercapnia and detected the dilatation of the vessels between 121% and 124% of the original diameters (n=5). We also repeated angiography in the mice before and after intracarotid injection of vasodilatation drugs papaverine hydrochloride, ATP disodium, and fasudil hydrochloride hydrate and demonstrated the chronological changes in the diameters in each artery at 1, 5, 15, and 30 minutes after injection (n=1 for each drug).

CONCLUSIONS

Using only a minimum volume of the contrast agent, synchrotron radiation enables us to study x-ray angiography in the mouse brain. The morphology of the vessels can be clearly observed under physiological conditions. The diameters and their changes can also be successfully studied in vivo.

Imaging cells and tissues with refractive index radiology

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.