3D micro-CT imaging of the postmortem brain

Revealing the three-dimensional murine brain microstructure by contrast-enhanced computed tomography

To improve our understanding of the brain microstructure, high-resolution 3D imaging is used to complement classical 2D histological assessment techniques. X-ray computed tomography allows high-resolution 3D imaging, but requires methods for enhancing contrast of soft tissues. Applying contrast-enhancing staining agents (CESAs) ameliorates the X-ray attenuating properties of soft tissue constituents and is referred to as contrast-enhanced computed tomography (CECT). Despite the large number of chemical compounds that have successfully been applied as CESAs for imaging brain, they are often toxic for the researcher, destructive for the tissue and without proper characterization of affinity mechanisms. We evaluated two sets of chemically related CESAs (organic, iodinated: Hexabrix and CA4+ and inorganic polyoxometalates: 1:2 hafnium-substituted Wells-Dawson phosphotungstate and Preyssler anion), for CECT imaging of healthy murine hemispheres. We then selected the CESA (Hexabrix) that provided the highest contrast between gray and white matter and applied it to a cuprizone-induced demyelination model. Differences in the penetration rate, effect on tissue integrity and affinity for tissue constituents have been observed for the evaluated CESAs. Cuprizone-induced demyelination could be visualized and quantified after Hexabrix staining. Four new non-toxic and non-destructive CESAs to the field of brain CECT imaging were introduced. The added value of CECT was shown by successfully applying it to a cuprizone-induced demyelination model. This research will prove to be crucial for further development of CESAs for ex vivo brain CECT and 3D histopathology.

High-resolution micro-CT for 3D infarct characterization and segmentation in mice stroke models

Characterization of brain infarct lesions in rodent models of stroke is crucial to assess stroke pathophysiology and therapy outcome. Until recently, the analysis of brain lesions was performed using two techniques: (1) histological methods, such as TTC (Triphenyltetrazolium chloride), a time-consuming and inaccurate process; or (2) MRI imaging, a faster, 3D imaging method, that comes at a high cost. In the last decade, high-resolution micro-CT for 3D sample analysis turned into a simple, fast, and cheaper solution. Here, we successfully describe the application of brain contrasting agents (Osmium tetroxide and inorganic iodine) for high-resolution micro-CT imaging for fine location and quantification of ischemic lesion and edema in mouse preclinical stroke models. We used the intraluminal transient MCAO (Middle Cerebral Artery Occlusion) mouse stroke model to identify and quantify ischemic lesion and edema, and segment core and penumbra regions at different time points after ischemia, by manual and automatic methods. In the transient-ischemic-attack (TIA) mouse model, we can quantify striatal myelinated fibers degeneration. Of note, whole brain 3D reconstructions allow brain atlas co-registration, to identify the affected brain areas, and correlate them with functional impairment. This methodology proves to be a breakthrough in the field, by providing a precise and detailed assessment of stroke outcomes in preclinical animal studies.

Preclinical Models of Brain Metastases in Breast Cancer

Breast cancer remains a leading cause of mortality among women worldwide. Brain metastases confer extremely poor prognosis due to a lack of understanding of their specific biology, unique physiologic and anatomic features of the brain, and limited treatment strategies. A major roadblock in advancing the treatment of breast cancer brain metastases (BCBM) is the scarcity of representative experimental preclinical models. Current models are predominantly based on the use of animal xenograft models with immortalized breast cancer cell lines that poorly capture the disease’s heterogeneity. Recent years have witnessed the development of patient-derived in vitro and in vivo breast cancer culturing systems that more closely recapitulate the biology from individual patients. These advances led to the development of modern patient-tissue-based experimental models for BCBM. The success of preclinical models is also based on the imaging technologies used to detect metastases. Advances in animal brain imaging, including cellular MRI and multimodality imaging, allow sensitive and specific detection of brain metastases and monitoring treatment responses. These imaging technologies, together with novel translational breast cancer models based on patient-derived cancer tissues, represent a unique opportunity to advance our understanding of brain metastases biology and develop novel treatment approaches. This review discusses the state-of-the-art knowledge in preclinical models of this disease.

Avoiding artefacts in MicroCT imaging of collagen scaffolds: Effect of phosphotungstic acid (PTA)-staining and crosslink density

X-ray micro-computed tomography (μ-CT) can be used to provide both qualitative and quantitative information on the structure of three-dimensional (3D) bioactive scaffolds. When performed in a dry state, μ-CT accurately reflects the structure of collagen-based scaffolds, but imaging in a wet state offers challenges with radiolucency. Here we have used phosphotungstic acid (PTA) as a contrast agent to visualise fully hydrated collagen scaffolds in a physiologically relevant environment. A systematic investigation was performed to understand the effects of PTA on the results of μ-CT imaging by varying sample processing variables such as crosslinking density, hydration medium and staining duration.

Immersing samples in 0.3% PTA solution overnight completely stained the samples and the treatment provided a successful route for μ-CT analysis of crosslinked samples. However, significant structural artefacts were observed for samples which were either non-crosslinked or had low levels of crosslinking, which had a heterogeneous interior architecture with collapsed pores at the scaffold periphery. This work highlights the importance of optimising the choice of processing and staining conditions to ensure accurate visualisation for hydrated 3D collagen scaffolds in an aqueous medium.

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Important new insights on artefact prevention in scaffold imaging.

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First time μ-CT imaging of a hydrated collagen scaffold is reported.

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Optimisation of the use of phosphotungstic acid in μ-CT imaging.

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Correlation between crosslinking degree and artefact creation is established.

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A solution to processing and staining issues is highlighted.

Multiscale imaging of the rat brain using an integrated diceCT and histology workflow

Advancements in tissue visualization techniques have spurred significant gains in the biomedical sciences by enabling researchers to integrate their datasets across anatomical scales. Of particular import are techniques that enable the interpolation of multiple hierarchical scales in samples taken from the same individuals. In this study, we demonstrate that two-dimensional histology techniques can be employed on neural tissues following three-dimensional diffusible iodine-based contrast-enhanced computed tomography (diceCT) without causing tissue degradation. This represents the first step toward a multiscale pipeline for brain visualization. We studied brains from adolescent male Sprague-Dawley rats, comparing experimental (diceCT-stained then de-stained) to control (without diceCT) brains to examine neural tissues for immunolabeling integrity, compare somata sizes, and distinguish neurons from glial cells within the telencephalon and diencephalon. We hypothesized that if experimental and control samples do not differ significantly in morphological cell analysis, then brain tissues are robust to the chemical, temperature, and radiation environments required for these multiple, successive imaging protocols. Visualizations for experimental brains were first captured via micro-computed tomography scanning of isolated, iodine-infused specimens. Samples were then cleared of iodine, serially sectioned, and prepared again using immunofluorescent, fluorescent, and cresyl violet labeling, followed by imaging with confocal and light microscopy, respectively. Our results show that many neural targets are resilient to diceCT imaging and compatible with downstream histological staining as part of a low-cost, multiscale brain imaging pipeline.

A fully segmented 3D anatomical atlas of a lizard brain

As the relevance of lizards in evolutionary neuroscience increases, so does the need for more accurate anatomical references. Moreover, the use of magnetic resonance imaging (MRI) in evolutionary neuroscience is becoming more widespread; this represents a fundamental methodological shift that opens new avenues of investigative possibility but also poses new challenges. Here, we aim to facilitate this shift by providing a three-dimensional segmentation atlas of the tawny dragon brain. The tawny dragon (Ctenophorus decresii) is an Australian lizard of increasing importance as a model system in ecology and, as a member of the agamid lizards, in evolution. Based on a consensus average 3D image generated from the MRIs of 13 male tawny dragon heads, we identify and segment 224 structures visible across the entire lizard brain. We describe the relevance of this atlas to the field of evolutionary neuroscience and propose further experiments for which this atlas can provide the foundation. This advance in defining lizard neuroanatomy will facilitate numerous studies in evolutionary neuroscience. The atlas is available for download as a supplementary material to this manuscript and through the Open Science Framework (OSF; https://doi.org/10.17605/OSF.IO/UJENQ ).

Illuminating the Brain With X-Rays: Contributions and Future Perspectives of High-Resolution Microtomography to Neuroscience

The assessment of three-dimensional (3D) brain cytoarchitecture at a cellular resolution remains a great challenge in the field of neuroscience and constant development of imaging techniques has become crucial, particularly when it comes to offering direct and clear obtention of data from macro to nano scales. Magnetic resonance imaging (MRI) and electron or optical microscopy, although valuable, still face some issues such as the lack of contrast and extensive sample preparation protocols. In this context, x-ray microtomography (μCT) has become a promising non-destructive tool for imaging a broad range of samples, from dense materials to soft biological specimens. It is a new supplemental method to be explored for deciphering the cytoarchitecture and connectivity of the brain. This review aims to bring together published works using x-ray μCT in neurobiology in order to discuss the achievements made so far and the future of this technique for neuroscience.

Contrast enhanced X-ray computed tomography imaging of amyloid plaques in Alzheimer disease rat model on lab based micro CT system

Amyloid plaques are small (~ 50 μm), highly-dense aggregates of amyloid beta (Aβ) protein in brain tissue, supposed to play a key role in pathogenesis of Alzheimer’s disease (AD). Plaques´ in vivo detection, spatial distribution and quantitative characterization could be an essential marker in diagnostics and evaluation of AD progress. However, current imaging methods in clinics possess substantial limits in sensitivity towards Aβ plaques to play a considerable role in AD screening. Contrast enhanced X-ray micro computed tomography (micro CT) is an emerging highly sensitive imaging technique capable of high resolution visualization of rodent brain. In this study we show the absorption based contrast enhanced X-ray micro CT imaging is viable method for detection and 3D analysis of Aβ plaques in transgenic rodent models of Alzheimer’s disease. Using iodine contrasted brain tissue isolated from the Tg-F344-AD rat model we show the micro CT imaging is capable of precise imaging of Aβ plaques, making possible to further analyze various aspects of their 3D spatial distribution and other properties.

Micro-computed tomography utility for estimation of intraparenchymal spinal cord cystic lesions in small animals

Precise assessment of spinal cord cystic lesions is crucial to formulate effective therapeutic strategies, yet histological assessment of the lesion remains the primary method despite numerous studies showing inconsistent results regarding estimation of lesion size via histology. On the other hand, despite numerous advances in micro-computed tomography (micro-CT) imaging and analysis that have allowed precise measurements of lesion size, there is not enough published data on its application to estimate intraspinal lesion size in laboratory animal models. This work attempts to show that micro-CT can be valuable for spinal cord injury research by demonstrating accurate estimation of syrinx size and compares between micro-CT and traditional histological analysis. We used a post-traumatic syringomyelia rat model to compare micro-CT analysis to conventional histological analysis. The study showed that micro-CT can detect lesions within the spinal cord very similar to histology. Importantly, micro-CT appears to provide more accurate estimates of the lesions with more measures (e.g., surface area), can detect compounds within the cord, and can be done with the tissue of interest (spinal cord) intact. In summary, the experimental work presented here provides one of the first investigations of the use of micro-CT for estimating the size of intraparenchymal cysts and detecting materials within the spinal cord. All animal procedures were approved by the University of Akron Institutional Animal Care and Use Committee (IACUC) (protocol # LRE 16-05-09 approved on May 14, 2016).

Scalable method for micro-CT analysis enables large scale quantitative characterization of brain lesions and implants

Anatomic evaluation is an important aspect of many studies in neuroscience; however, it often lacks information about the three-dimensional structure of the brain. Micro-CT imaging provides an excellent, nondestructive, method for the evaluation of brain structure, but current applications to neurophysiological or lesion studies require removal of the skull as well as hazardous chemicals, dehydration, or embedding, limiting their scalability and utility. Here we present a protocol using eosin in combination with bone decalcification to enhance contrast in the tissue and then employ monochromatic and propagation phase-contrast micro-CT imaging to enable the imaging of brain structure with the preservation of the surrounding skull. Instead of relying on descriptive, time-consuming, or subjective methods, we develop simple quantitative analyses to map the locations of recording electrodes and to characterize the presence and extent of hippocampal brain lesions.

ViceCT and whiceCT for simultaneous high-resolution visualization of craniofacial, brain and ventricular anatomy from micro-computed tomography

Up to 40% of congenital diseases present disturbances of brain and craniofacial development resulting in simultaneous alterations of both systems. Currently, the best available method to preclinically visualize the brain and the bones simultaneously is to co-register micro-magnetic resonance (µMR) and micro-computed tomography (µCT) scans of the same specimen. However, this requires expertise and access to both imaging techniques, dedicated software and post-processing knowhow. To provide a more affordable, reliable and accessible alternative, recent research has focused on optimizing a contrast-enhanced µCT protocol using iodine as contrast agent that delivers brain and bone images from a single scan. However, the available methods still cannot provide the complete visualization of both the brain and whole craniofacial complex. In this study, we have established an optimized protocol to diffuse the contrast into the brain that allows visualizing the brain parenchyma and the complete craniofacial structure in a single ex vivo µCT scan (whiceCT). In addition, we have developed a new technique that allows visualizing the brain ventricles using a bilateral stereotactic injection of iodine-based contrast (viceCT). Finally, we have tested both techniques in a mouse model of Down syndrome, as it is a neurodevelopmental disorder with craniofacial, brain and ventricle defects. The combined use of viceCT and whiceCT provides a complete visualization of the brain and bones with intact craniofacial structure of an adult mouse ex vivo using a single imaging modality.

Connections between the internal and the external capsules and the globus pallidus in the sheep: A dichromate stain X-ray microtomographic study

Sheep are recognized as useful species for translational neurodegeneration research, in particular for the study of Huntington disease. There is a lack of information regarding the detailed anatomy and connections of the basal ganglia of sheep, in normal myeloarchitectonics and in tract-tracing studies. In this work, the organization of the corticostriatal projections at the level of the putamen and globus pallidus (GP) are explored. For the first time, the myeloarchitectonic pattern of connections between the internal (IC) and the external (EC) capsules with the GP have been investigated in the sheep. Formaldehyde-fixed blocks of the striatum were treated with a metallic stain containing potassium dichromate and visualized using micro-CT (µ-CT). The trivalent chromium (Cr3+), attached to myelin phospholipids, imparts a differential contrast to the grey and white matter compartments, which allows the visualization of myelinated fascicles in µ-CT images. The fascicles were classified according to their topographical location in dorsal supreme fascicles (X, Y, apex) arising from the IC and EC; pre-commissurally, basal fascicles connecting the ventral part of the EC with the lateral zone of the ventral pallidum (VP) and, post-commissurally, superior (Z₁ ), middle (Z₂ ) and lower (Z₃ ) fascicles, connecting at different levels the EC with the GP. The results suggest that the presumptive cortical efferent and afferent fibres to the pallidum could be organized according to a dorsal to ventrolateral topography in the sheep, similar to that seen in other mammals. The proposed methodology has the potential to delineate the myeloarchitectonic patterns of nervous systems and tracts.

X-ray microtomography is a novel method for accurate evaluation of small-bowel mucosal morphology and surface area

The often poorly orientated small-bowel mucosal biopsies taken for the diagnostics of celiac disease and other intestinal disorders are prone to misinterpretation. Furthermore, conventional histopathology has suboptimal sensitivity for early histopathological changes observed in short-term challenge studies. X-ray microtomography (micro-CT) is a promising new method for accurate imaging of human-derived biological samples. Here, we report that micro-CT could be utilized to create virtual reconstructions of endoscopically obtained intestinal biopsies. The formed digital 3D images enabled selection of always optimal cutting angles for accurate measurement of the mucosal damage and revealed diagnostic lesions in cases interpreted as normal with conventional histomorphometry. We also demonstrate that computer-assisted point cloud analysis can be used to calculate biologically meaningful surface areas of the biopsies in different stages of mucosal damage with excellent replicability and correlation with other disease parameters. We expect the improved diagnostic accuracy and capability to measure the surface areas to provide a powerful tool for the diagnostics of intestinal diseases and for future clinical and pharmaceutical trials.

Finite element analysis and three-dimensional reconstruction of tonotopically aligned human auditory fiber pathways: A computational environment for modeling electrical stimulation by a cochlear implant based on micro-CT

The application of cochlear implants can be studied with computational models. The electrical potential distribution induced by an implanted device is evaluated with a volume conductor model, which is used as input for neuron models to simulate the reaction of cochlear neurons to micro-stimulation. In order to reliably predict the complex excitation profiles it is vital to consider an accurate representation of the human cochlea geometry including detailed three-dimensional pathways of auditory neurons reaching from the organ of Corti through the cochlea-volume. In this study, high-resolution micro-CT imaging (Δx = Δy = Δz = 3 μm) was used to reconstruct the pathways of 30 tonotopically organized nerve fiber bundles, distributed over eight octaves (11500-40 Hz). Results of the computational framework predict: (i) the peripheral process is most sensitive to cathodic stimulation (CAT), (ii) in many cases CAT elicits spikes in the peripheral terminal at threshold but with larger stimuli there is a second spike initiation site within the peripheral process, (iii) anodic stimuli (ANO) can excite the central process even at threshold, (iv) the recruitment of fibers by electrodes located in the narrowing middle- and apical turn is complex and impedes focal excitation of low frequency fibers, (v) degenerated cells which lost the peripheral process are more sensitive to CAT when their somata are totally covered with 2 membranes of a glial cell but they become ANO sensitive when the myelin covering is reduced.

MicroCT optimisation for imaging fascicular anatomy in peripheral nerves

BACKGROUND

Due to the lack of understanding of the fascicular organisation, vagus nerve stimulation (VNS) leads to unwanted off-target effects. Micro-computed tomography (microCT) can be used to trace fascicles from periphery and image fascicular anatomy.

NEW METHOD

In this study, we present a simple and reproducible method for imaging fascicles in peripheral nerves with iodine staining and microCT for the determination of fascicular anatomy and organisation.

RESULTS

At the determined optimal pre-processing steps and scanning parameters, the microCT protocol allowed for segmentation and tracking of fascicles within the nerves. This was achieved after 24 hours and 120 hours of staining with Lugol's solution (1% total iodine) for rat sciatic and pig vagus nerves, respectively, and the following scanning parameters: 4 μm voxel size, 35 kVp energy, 114 μA current, 4 W power, 0.25 fps in 4 s exposure time, 3176 projections and a molybdenum target.

COMPARISON WITH EXISTING METHOD(S)

This optimised method for imaging fascicles provides high-resolution, three-dimensional images and full imaging penetration depth not obtainable with methods typically used such as histology, magnetic resonance imaging and optical coherence tomography whilst obviating time-consuming pre-processing methods, the amount of memory required, destruction of the samples and the cost associated with current microCT methods.

CONCLUSION

The optimised microCT protocol facilitates segmentation and tracking of the fascicles within the nerve. The resulting segmentation map of the functional anatomical organisation of the vagus nerve will enable selective VNS ultimately allowing for the avoidance of the off-target effects and improving its therapeutic efficacy.

Investigation on the validity of 3D micro-CT imaging in the fish brain

BACKGROUND

Micro-computed tomography (CT) is a non-invasive technique that is used to obtain three-dimensional (3D) images of tissue structure in small animals. Compared with extensive mammal studies, few 3D imaging studies of fish have been conducted using micro-CT. An optimized method for imaging fish tissue structure is necessary, because they have adapted to diverse environments via functional and structural specialization.

NEW METHOD

Brains of three species with different sizes and habitats were fixed in 4% paraformaldehyde and immersed in non-ionic iodinated contrast agent (Iopamiron). We examined the relationship between Iopamiron concentration and immersion time to determine universally optimal conditions for use in fish.

RESULTS

We reconstructed 3D images of whole fish brains from cross-sections of brains from the Malabar grouper (Epinephelus malabaricus), bastard halibut (Paralichthys olivaceus), and threespot wrasse (Halichoeres trimaculatus). Developmental changes in brain structure were observed in the bastard halibut. Most brain regions of the threespot wrasse were distinguishable, although inner regions of the brain were less visible.

COMPARISON WITH EXISTING METHODS

Histological techniques are typically used to observe fish brain structure, despite its drawbacks in terms of tissue sample preparation (shrinkage and distortion) and image capture (3D image constriction). The technique examined in the present study solves these problems and allows for the simultaneous handling of multiple specimens.

CONCLUSION

Micro-CT imaging is suitable for observing the surfaces and inner structures of fish of various species.

Bone Marrow Adipose Tissue Quantification by Imaging

PURPOSE OF REVIEW

The significance and roles of marrow adipose tissue (MAT) are increasingly known, and it is no more considered a passive fat storage but a tissue with significant paracrine and endocrine activities that can cause lipotoxicity and inflammation.

RECENT FINDINGS

Changes in the MAT volume and fatty acid composition appear to drive bone and hematopoietic marrow deterioration, and studying it may open new horizons to predict bone fragility and anemia development. MAT has the potential to negatively impact bone volume and strength through several mechanisms that are partially described by inflammaging and lipotoxicity terminology. Evidence indicates paramount importance of MAT in age-associated decline of bone and red marrow structure and function. Currently, MAT measurement is being tested and validated by several techniques. However, purpose-specific adaptation of existing imaging technologies and, more importantly, development of new modalities to quantitatively measure MAT are yet to be done.

Comparative analysis of sample preparation protocols of soft biological tissues for morphometric studies using synchrotron-based X-ray microtomography

The spread of microtomography as a tool for visualization of soft tissues has had a significant impact on a better understanding of complex biological systems. This technique allows a detailed three-dimensional quantitative view of the specimen to be obtained, correlating its morphological organization with its function, providing valuable insights on the functionality of the tissue. Regularly overlooked, but of great importance, proper sample mounting and preparation are fundamental for achieving the highest possible image quality even for the high-resolution imaging systems currently under development. Here, a quantitative analysis compares some of the most common sample-mounting strategies used for synchrotron-based X-ray microtomography of soft tissues: alcoholic-immersion, paraffin-embedding and critical-point drying. These three distinct sample-mounting strategies were performed on the same specimen in order to investigate their impact on sample morphology regardless of individual sample variation. In that sense, the alcoholic-immersion strategy, although causing less shrinkage to the tissue, proved to be the most unsuitable approach for a high-throughput high-resolution imaging experiment due to sample drifting. Also, critical-point drying may present some interesting advantages regarding image quality but is also incompatible with a high-throughput experiment. Lastly, paraffin-embedding is shown to be the most suitable strategy for current soft tissue microtomography experiments. Such detailed analysis of biological sample-mounting strategies for synchrotron-based X-ray microtomography are expected to offer valuable insights on the best approach for using this technique for 3D imaging of soft tissues and following morphometric analysis.

OptiJ: Open-source optical projection tomography of large organ samples

The three-dimensional imaging of mesoscopic samples with Optical Projection Tomography (OPT) has become a powerful tool for biomedical phenotyping studies. OPT uses visible light to visualize the 3D morphology of large transparent samples. To enable a wider application of OPT, we present OptiJ, a low-cost, fully open-source OPT system capable of imaging large transparent specimens up to 13 mm tall and 8 mm deep with 50 µm resolution. OptiJ is based on off-the-shelf, easy-to-assemble optical components and an ImageJ plugin library for OPT data reconstruction. The software includes novel correction routines for uneven illumination and sample jitter in addition to CPU/GPU accelerated reconstruction for large datasets. We demonstrate the use of OptiJ to image and reconstruct cleared lung lobes from adult mice. We provide a detailed set of instructions to set up and use the OptiJ framework. Our hardware and software design are modular and easy to implement, allowing for further open microscopy developments for imaging large organ samples.

Development of a contrast-enhanced micro computed tomography protocol for the oval squid (Sepioteuthis lessoniana) brain

Coleoid cephalopods (squid, cuttlefish, and octopus) have a well-developed and complex central nervous system. Its absolute size is the largest among invertebrates, and the brain-to-body mass ratio is larger than that of fish and reptiles and equivalent to that of birds and mammals. Although a number of histological studies have been conducted on the brains of cephalopods, most of them used a light microscope or an electron microscope, which show the microstructure of the brain, but often cannot image the whole brain instantaneously. Of late, micro computed tomography (CT) has gained popularity for imaging animal brains because it allows for noninvasive three-dimensional (3D) reconstruction and preprocessing that are not cumbersome. To perform micro-CT on cephalopod brains, we first tested conditions suitable for preprocessing, paying special attention to staining conditions that would provide high contrast images. Four agents, iodine in 99.5% ethanol, iodine potassium iodide in water (IKI), phosphotungstic acid in 70% ethanol, and nonionic iodinated contrast agent in water, were tested at various concentrations and durations on brain of juvenile oval squid. To evaluate the quality of staining, we calculated the contrast ratio of the two-dimensional (2D) images and compared 3D segmentation of the best and worst 2D images. We concluded that 3% IKI staining for 7 days was the best combination to enhance the images contrast of the oval squid brain, in which each brain lobe was clearly detected and 3D segmentation of the whole brain was possible. The wider applicability of this preprocessing method for micro-CT of the brains of other cephalopods is discussed.

Anatomy Visualizations Using Stereopsis: Current Methodologies in Developing Stereoscopic Virtual Models in Anatomical Education

Technology for developing three-dimensional (3D) virtual models in anatomical sciences education has seen a great improvement in recent years. Various data used for creating stereoscopic virtual models have also been constantly improving. This paper focuses specifically on the methodologies of creating stereoscopic virtual models and the techniques and materials used in developing stereoscopic virtual models from both our previous studies and other published literature. The presentation and visualization of stereoscopic models are highlighted, and the benefits and limitations of stereoscopic models are discussed. The practice of making 3D measurements on the lengths, angles, and volumes of models can potentially be used to help predict typical measurement parameters of anatomical structures and for the placement of surgical instruments. Once stereoscopic virtual models have been constructed, their visualization and presentation can be implemented in anatomy education and clinical surgical trainings.

Micro-computed tomography: a new diagnostic tool in postmortem assessment of brain anatomy in small fetuses

PURPOSE

The aim of our study was to evaluate the postmortem micro-CT anatomy of early fetal human fetal brains, either in situ or isolated.

METHODS

We studied 12 ex vivo specimens, 9 whole human fetuses (9-18 GW), and 3 isolated samples (16-26 GW). Specimens were fixed in formalin, then immersed in Lugol solution. Images were evaluated by two neuroradiologists. The depiction of CNS structures was defined based on the comparison between micro-CT images and a reference histologic anatomical Atlas of human brain development.

RESULTS

Micro-CT provided informative high-resolution brain images in all cases, with the exception of one case (9 weeks) due to advanced maceration. All major CNS structures (i.e., brain hemispheres, layering, ventricles, germinal neuroepithelium, basal ganglia, corpus callosum, major cranial nerves, and structures of the head and neck) were recognizable.

CONCLUSIONS

Micro-CT imaging of the early fetal brain is feasible and provides high-quality images that correlate with the histological Atlas of the human brain, offering multiplanar and volumetric images that can be stored and shared for clinical, teaching, and research purposes.

Contrast-Enhanced MicroCT for Virtual 3D Anatomical Pathology of Biological Tissues: A Literature Review

To date, the combination of histological sectioning, staining, and microscopic assessment of the 2D sections is still the golden standard for structural and compositional analysis of biological tissues. X-ray microfocus computed tomography (microCT) is an emerging 3D imaging technique with high potential for 3D structural analysis of biological tissues with a complex and heterogeneous 3D structure, such as the trabecular bone. However, its use has been mostly limited to mineralized tissues because of the inherently low X-ray absorption of soft tissues. To achieve sufficient X-ray attenuation, chemical compounds containing high atomic number elements that bind to soft tissues have been recently adopted as contrast agents (CAs) for contrast-enhanced microCT (CE-CT); this novel technique is very promising for quantitative "virtual" 3D anatomical pathology of both mineralized and soft biological tissues. In this paper, we provided a review of the advances in CE-CT since the very first reports on the technology to date. Perfusion CAs for in vivo imaging have not been discussed, as the focus of this review was on CAs that bind to the tissue of interest and that are, thus, used for ex vivo imaging of biological tissues. As CE-CT has mostly been applied for the characterization of musculoskeletal tissues, we have put specific emphasis on these tissues. Advantages and limitations of multiple CAs for different musculoskeletal tissues have been highlighted, and their reproducibility has been discussed. Additionally, the advantages of the "full" 3D CE-CT information have been pinpointed, and its importance for more detailed structural, spatial, and functional characterization of the tissues of interest has been shown. Finally, the remaining challenges that are still hampering a broader adoption of CE-CT have been highlighted, and suggestions have been made to move the field of CE-CT imaging one step further towards a standard accepted tool for quantitative virtual 3D anatomical pathology.

A step towards valid detection and quantification of lung cancer volume in experimental mice with contrast agent-based X-ray microtomography

Tumor volume is a parameter used to evaluate the performance of new therapies in lung cancer research. Conventional methods that are used to estimate tumor size in mouse models fail to provide fast and reliable volumetric data for tumors grown non-subcutaneously. Here, we evaluated the use of iodine-staining combined with micro-computed tomography (micro-CT) to estimate the tumor volume of ex vivo tumor-burdened lungs. We obtained fast high spatial resolution three-dimensional information of the lungs, and we demonstrated that iodine-staining highlights tumors and unhealthy tissue. We processed iodine-stained lungs for histopathological analysis with routine hematoxylin and eosin (H&E) staining. We compared the traditional tumor burden estimation performed manually with H&E histological slices with a semi-automated method using micro-CT datasets. In mouse models that develop lung tumors with well precise boundaries, the method that we describe here enables to perform a quick estimation of tumorous tissue volume in micro-CT images. Our method overestimates the tumor burden in tumors surrounded by abnormal tissue, while traditional histopathological analysis underestimates tumor volume. We propose to embed micro-CT imaging to the traditional workflow of tumorous lung analyses in preclinical cancer research as a strategy to obtain a more accurate estimation of the total lung tumor burden.

A micro-CT-based method for quantitative brain lesion characterization and electrode localization

Lesion verification and quantification is traditionally done via histological examination of sectioned brains, a time-consuming process that relies heavily on manual estimation. Such methods are particularly problematic in posterior cortical regions (e.g. visual cortex), where sectioning leads to significant damage and distortion of tissue. Even more challenging is the post hoc localization of micro-electrodes, which relies on the same techniques, suffers from similar drawbacks and requires even higher precision. Here, we propose a new, simple method for quantitative lesion characterization and electrode localization that is less labor-intensive and yields more detailed results than conventional methods. We leverage staining techniques standard in electron microscopy with the use of commodity micro-CT imaging. We stain whole rat and zebra finch brains in osmium tetroxide, embed these in resin and scan entire brains in a micro-CT machine. The scans result in 3D reconstructions of the brains with section thickness dependent on sample size (12-15 and 5-6 microns for rat and zebra finch respectively) that can be segmented manually or automatically. Because the method captures the entire intact brain volume, comparisons within and across studies are more tractable, and the extent of lesions and electrodes may be studied with higher accuracy than with current methods.

Dual-energy micro-CT for quantifying the time-course and staining characteristics of ex-vivo animal organs treated with iodine- and gadolinium-based contrast agents

Chemical staining of soft-tissues can be used as a strategy to increase their low inherent contrast in X-ray absorption micro-computed tomography (micro-CT), allowing to obtain fast three-dimensional structural information of animal organs. Though some staining agents are commonly used in this context, little is known about the staining agents' ability to stain specific types of tissues; the times necessary to provide a sufficient contrast; and the effect of staining solution in distorting the tissue. Here we contribute to studies of animal organs (mouse heart and lungs) using staining combined with dual-energy micro-CT (DECT). DECT was used in order to obtain an additional quantitative measure for the amount of staining agents within the sample in 3D maps. Our results show that the two staining solutions used in this work diffuse differently in the tissues studied, the staining times of some tens of minutes already produce high-quality micro-CT images and, at the concentrations applied in this work, the staining solutions tested do not cause relevant tissue distortions. While one staining solution provides images of the general morphology of the organs, the other reveals organs' features in the order of a hundred micrometers.

Therapeutic Effect of Astroglia-like Mesenchymal Stem Cells Expressing Glutamate Transporter in a Genetic Rat Model of Depression

Recent studies have proposed that abnormal glutamatergic neurotransmission and glial pathology play an important role in the etiology and manifestation of depression. It was postulated that restoration of normal glutamatergic transmission, by enhancing glutamate uptake, may have a beneficial effect on depression. We examined this hypothesis using unique human glial-like mesenchymal stem cells (MSCs), which in addition to inherent properties of migration to regions of injury and secretion of neurotrophic factors, were differentiated to express high levels of functional glutamate transporters (excitatory amino acid transporters; EAAT). Additionally, gold nanoparticles (GNPs), which serve as contrast agents for CT imaging, were loaded into the cells for non-invasive, real-time imaging and tracking of MSC migration and final location within the brain. MSC-EAAT (2×10⁵; 10 μl) were administered (i.c.v.) to Flinder Sensitive Line rats (FSLs), a genetic model for depression, and longitudinal behavioral and molecular changes were monitored. FSL rats treated with MSC-EAAT showed attenuated depressive-like behaviors (measured by the forced swim test, novelty exploration test and sucrose self-administration paradigm), as compared to controls. CT imaging, Flame Atomic Absorption Spectroscopy analysis and immunohistochemistry showed that the majority of MSCs homed specifically to the dentate gyrus of the hippocampus, a region showing structural brain changes in depression, including loss of glial cells. mRNA and protein levels of EAAT1 and BDNF were significantly elevated in the hippocampus of MSC-EAAT-treated FSLs. Our findings indicate that MSC-EAATs effectively improve depressive-like manifestations, possibly in part by increasing both glutamate uptake and neurotropic factor secretion in the hippocampus.

The effect of nanoparticle size on the ability to cross the blood-brain barrier: an in vivo study

AIM

Our goal was to develop an efficient nanoparticle-based system that can overcome the restrictive mechanism of the blood-brain barrier (BBB) by targeting insulin receptors and would thus enable drug delivery to the brain.

METHODS

Insulin-coated gold nanoparticles (INS-GNPs) were synthesized to serve as a BBB transport system. The effect of nanoparticle size (20, 50 and 70 nm) on their ability to cross the BBB was quantitatively investigated in Balb/C mice.

RESULTS

The most widespread biodistribution and highest accumulation within the brain were observed using 20 nm INS-GNPs, 2 h post injection. In vivo CT imaging revealed that particles migrated to specific brain regions, which are involved in neurodegenerative and neuropsychiatric disorders.

CONCLUSION

These findings promote the optimization of nanovehicles for transport of drugs through the BBB. The insulin coating of the particles enabled targeting of specific brain regions, suggesting the potential use of INS-GNPs for delivery of various treatments for brain-related disorders.

Measurement of multispectral scattering properties in mouse brain tissue

We present the scattering properties of mouse brain using multispectral diffraction phase microscopy. Typical diffraction phase microscopy was incorporated with the broadband light source which offers the measurement of the scattering coefficient and anisotropy in the spectral range of 550-900 nm. The regional analysis was performed for both the myeloarchitecture and cytoarchitecture of the brain tissue. Our results clearly evaluate the multispectral scattering properties in the olfactory bulb and corpus callosum. The scattering coefficient measured in the corpus callosum is about four times higher than in the olfactory bulb. It also indicates that it is feasible to realize the quantitative phase microscope in near infrared region for thick brain tissue imaging.

Label-free, multi-scale imaging of ex-vivo mouse brain using spatial light interference microscopy

Brain connectivity spans over broad spatial scales, from nanometers to centimeters. In order to understand the brain at multi-scale, the neural network in wide-field has been visualized in detail by taking advantage of light microscopy. However, the process of staining or addition of fluorescent tags is commonly required, and the image contrast is insufficient for delineation of cytoarchitecture. To overcome this barrier, we use spatial light interference microscopy to investigate brain structure with high-resolution, sub-nanometer pathlength sensitivity without the use of exogenous contrast agents. Combining wide-field imaging and a mosaic algorithm developed in-house, we show the detailed architecture of cells and myelin, within coronal olfactory bulb and cortical sections, and from sagittal sections of the hippocampus and cerebellum. Our technique is well suited to identify laminar characteristics of fiber tract orientation within white matter, e.g. the corpus callosum. To further improve the macro-scale contrast of anatomical structures, and to better differentiate axons and dendrites from cell bodies, we mapped the tissue in terms of its scattering property. Based on our results, we anticipate that spatial light interference microscopy can potentially provide multiscale and multicontrast perspectives of gross and microscopic brain anatomy.

Brain Distribution and Efficacy of the Brain Penetrant PI3K Inhibitor GDC-0084 in Orthotopic Mouse Models of Human Glioblastoma

Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults. Limited treatment options have only marginally impacted patient survival over the past decades. The phophatidylinositol 3-kinase (PI3K) pathway, frequently altered in GBM, represents a potential target for the treatment of this glioma. 5-(6,6-Dimethyl-4-morpholino-8,9-dihydro-6H-[1,4]oxazino[4,3-e]purin-2-yl)pyrimidin-2-amine (GDC-0084) is a PI3K inhibitor that was specifically optimized to cross the blood-brain barrier. The goals of our studies were to characterize the brain distribution, pharmacodynamic (PD) effect, and efficacy of GDC-0084 in orthotopic xenograft models of GBM. GDC-0084 was tested in vitro to assess its sensitivity to the efflux transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) and in vivo in mice to evaluate its effects on the PI3K pathway in intact brain. Mice bearing U87 or GS2 intracranial tumors were treated with GDC-0084 to assess its brain distribution by matrix-assisted laser desorption ionization (MALDI) imaging and measure its PD effects and efficacy in GBM orthotopic models. Studies in transfected cells indicated that GDC-0084 was not a substrate of P-gp or BCRP. GDC-0084 markedly inhibited the PI3K pathway in mouse brain, causing up to 90% suppression of the pAkt signal. MALDI imaging showed GDC-0084 distributed evenly in brain and intracranial U87 and GS2 tumors. GDC-0084 achieved significant tumor growth inhibition of 70% and 40% against the U87 and GS2 orthotopic models, respectively. GDC-0084 distribution throughout the brain and intracranial tumors led to potent inhibition of the PI3K pathway. Its efficacy in orthotopic models of GBM suggests that it could be effective in the treatment of GBM. GDC-0084 is currently in phase I clinical trials.

Micro-computed tomography in murine models of cerebral cavernous malformations as a paradigm for brain disease

BACKGROUND

Cerebral cavernous malformations (CCMs) are hemorrhagic brain lesions, where murine models allow major mechanistic discoveries, ushering genetic manipulations and preclinical assessment of therapies. Histology for lesion counting and morphometry is essential yet tedious and time consuming. We herein describe the application and validations of X-ray micro-computed tomography (micro-CT), a non-destructive technique allowing three-dimensional CCM lesion count and volumetric measurements, in transgenic murine brains.

NEW METHOD

We hereby describe a new contrast soaking technique not previously applied to murine models of CCM disease. Volumetric segmentation and image processing paradigm allowed for histologic correlations and quantitative validations not previously reported with the micro-CT technique in brain vascular disease.

RESULTS

Twenty-two hyper-dense areas on micro-CT images, identified as CCM lesions, were matched by histology. The inter-rater reliability analysis showed strong consistency in the CCM lesion identification and staging (K=0.89, p<0.0001) between the two techniques. Micro-CT revealed a 29% greater CCM lesion detection efficiency, and 80% improved time efficiency.

COMPARISON WITH EXISTING METHOD

Serial integrated lesional area by histology showed a strong positive correlation with micro-CT estimated volume (r(2)=0.84, p<0.0001).

CONCLUSIONS

Micro-CT allows high throughput assessment of lesion count and volume in pre-clinical murine models of CCM. This approach complements histology with improved accuracy and efficiency, and can be applied for lesion burden assessment in other brain diseases.

Extending two-dimensional histology into the third dimension through conventional micro computed tomography

Histological examination achieves sub-micrometer resolution laterally. In the third dimension, however, resolution is limited to section thickness. In addition, histological sectioning and mounting sections on glass slides introduce tissue-dependent stress and strain. In contrast, state-of-the-art hard X-ray micro computed tomography (μCT) systems provide isotropic sub-micrometer resolution and avoid sectioning artefacts. The drawback of μCT in the absorption contrast mode for visualising physically soft tissue is a low attenuation difference between anatomical features. In this communication, we demonstrate that formalin-fixed paraffin-embedded human cerebellum yields appropriate absorption contrast in laboratory-based μCT data, comparable to conventional histological sections. Purkinje cells, for example, are readily visible. In order to investigate the pros and cons of complementary approaches, two- and three-dimensional data were manually and automatically registered. The joint histogram of histology and the related μCT slice allows for a detailed discussion on how to integrate two-dimensional information from histology into a three-dimensional tomography dataset. This methodology is not only rewarding for the analysis of the human cerebellum, but it also has relevance for investigations of tissue biopsies and post-mortem applications. Our data indicate that laboratory-based μCT as a modality can fill the gap between synchrotron radiation-based μCT and histology for a variety of tissues. As the information from haematoxylin and eosin (H&E) stained sections and μCT data is related, one can colourise local X-ray absorption values according to the H&E stain. Hence, μCT data can correlate and virtually extend two-dimensional (2D) histology data into the third dimension.

Optimal Contrast Agent Staining of Ligaments and Tendons for X-Ray Computed Tomography

X-ray computed tomography has become an important tool for studying the microstructures of biological soft tissues, such as ligaments and tendons. Due to the low X-ray attenuation of such tissues, chemical contrast agents are often necessary to enhance contrast during scanning. In this article, the effects of using three different contrast agents—iodine potassium iodide solution, phosphotungstic acid and phosphomolybdic acid—are evaluated and compared. Porcine anterior cruciate ligaments, patellar tendons, medial collateral ligaments and lateral collateral ligaments were used as the basis of the study. Three samples of each of the four ligament/tendon types were each assigned a different contrast agent (giving a total of twelve samples), and the progression of that agent through the tissue was monitored by performing a scan every day for a total period of five days (giving a total of sixty scans). Since the samples were unstained on day one, they had been stained for a total of four days by the time of the final scans. The relative contrast enhancement and tissue deformation were measured. It was observed that the iodine potassium iodide solution penetrated the samples fastest and caused the least sample shrinkage on average (although significant deformation was observed by the time of the final scans), whereas the phosphomolybdic acid caused the greatest sample shrinkage. Equations describing the observed behaviour of the contrast agents, which can be used to predict optimal staining times for ligament and tendon X-ray computed tomography, are presented.

Diffusible iodine-based contrast-enhanced computed tomography (diceCT): an emerging tool for rapid, high-resolution, 3-D imaging of metazoan soft tissues

Morphologists have historically had to rely on destructive procedures to visualize the three‐dimensional (3‐D) anatomy of animals. More recently, however, non‐destructive techniques have come to the forefront. These include X‐ray computed tomography (CT), which has been used most commonly to examine the mineralized, hard‐tissue anatomy of living and fossil metazoans. One relatively new and potentially transformative aspect of current CT‐based research is the use of chemical agents to render visible, and differentiate between, soft‐tissue structures in X‐ray images. Specifically, iodine has emerged as one of the most widely used of these contrast agents among animal morphologists due to its ease of handling, cost effectiveness, and differential affinities for major types of soft tissues. The rapid adoption of iodine‐based contrast agents has resulted in a proliferation of distinct specimen preparations and scanning parameter choices, as well as an increasing variety of imaging hardware and software preferences. Here we provide a critical review of the recent contributions to iodine‐based, contrast‐enhanced CT research to enable researchers just beginning to employ contrast enhancement to make sense of this complex new landscape of methodologies. We provide a detailed summary of recent case studies, assess factors that govern success at each step of the specimen storage, preparation, and imaging processes, and make recommendations for standardizing both techniques and reporting practices. Finally, we discuss potential cutting‐edge applications of diffusible iodine‐based contrast‐enhanced computed tomography (diceCT) and the issues that must still be overcome to facilitate the broader adoption of diceCT going forward.

Synthesis and microstructural properties of the scaffold based on a 3-(trimethoxysilyl)propyl methacrylate–POSS hybrid towards potential tissue engineering applications

The biomimetic organic–inorganic scaffold with the chemical composition, structural dimensions, topography, and microstructural properties that fulfills the requirements for hard-tissue engineering was developed.

Clinical utility of postmortem microcomputed tomography of the fetal heart: diagnostic imaging vs macroscopic dissection

OBJECTIVES

Congenital cardiac malformations are commonly identified at perinatal autopsy, which can be challenging in fetuses of early gestation and in macerated fetuses. Our objective was to examine fetal complex congenital heart disease by microcomputed tomography (micro-CT), using standard autopsy as the gold standard.

METHODS

In this ethically approved study, ex-vivo isolated fetal heart and fetal heart-lung blocks underwent iodine preparation prior to micro-CT, and were fixed in formalin after the micro-CT examination. Images were acquired using a microfocus-CT scanner with individual specimen image optimization. Twenty-one indices assessed normally at autopsy were evaluated for each dataset. Cardiac dissection was performed using a dissecting microscope within 24 h of the micro-CT examination.

RESULTS

We examined six fetal hearts, comprising five with complex congenital cardiac malformations at a gestational age of 17-23 weeks and an anatomically normal heart of 23 weeks' gestation for reference. All specimens demonstrated excellent internal contrast at micro-CT examination, and the correct overall diagnosis was made in all cases. There was agreement for 114/126 indices assessed on micro-CT and at autopsy dissection (overall concordance of 95.8% (95% CI, 90.5-98.2%)). Micro-CT was particularly useful in the assessment of ventricular morphology in macerated fetuses.

CONCLUSIONS

Micro-CT of small ex-vivo fetal specimens can provide highly accurate three-dimensional rendering of complex congenital fetal heart disease. This approach represents a significant advance in postmortem imaging and confirms the potential of this technology for non-invasive examination of small fetuses and organs.

Complementary use of bioluminescence imaging and contrast-enhanced micro-computed tomography in an orthotopic brain tumor model

Small animal models are crucial to link molecular discoveries and implementation of clinically relevant therapeutics in oncology. Using these models requires noninvasive imaging techniques to monitor disease progression and therapy response. Micro-computed tomography (CT) is less studied for the in vivo monitoring of murine intracranial tumors and traditionally suffers from poor soft tissue contrast, whereas bioluminescence imaging (BLI) is known for its sensitivity but is not frequently employed for quantifying tumor volume. A widely used orthotopic glioblastoma multiforme (GBM) tumor model was applied in nude mice, and tumor growth was evaluated by BLI and contrast-enhanced microCT imaging. A strong correlation was observed between CT volume and BLI-integrated intensity (Pearson coefficient (r)  =  .85, p  =  .0002). Repeated contouring of contrast-enhanced microCT-delineated tumor volumes achieved an intraobserver average pairwise overlap ratio of 0.84 and an average tumor volume coefficient of variance of 0.11. MicroCT-delineated tumor size was found to correlate with tumor size obtained via histologic analysis (Pearson coefficient (r)  =  .88, p  =  .005). We conclude that BLI intensity can be used to derive tumor volume but that the use of both contrast-enhanced microCT and BLI provides complementary tumor growth information, which is particularly useful for modern small animal irradiation devices that make use of microCT and BLI for treatment planning, targeting, and monitoring.

Variation in Brain Morphology of Intertidal Gobies: A Comparison of Methodologies Used to Quantitatively Assess Brain Volumes in Fish

When correlating brain size and structure with behavioural and environmental characteristics, a range of techniques can be utilised. This study used gobiid fishes to quantitatively compare brain volumes obtained via three different methods; these included the commonly used techniques of histology and approximating brain volume to an idealised ellipsoid, and the recently established technique of X-ray micro-computed tomography (micro-CT). It was found that all three methods differed significantly from one another in their volume estimates for most brain lobes. The ellipsoid method was prone to over- or under-estimation of lobe size, histology caused shrinkage in the telencephalon, and although micro-CT methods generated the most reliable results, they were also the most expensive. Despite these differences, all methods depicted quantitatively similar relationships among the four different species for each brain lobe. Thus, all methods support the same conclusions that fishes inhabiting rock pool and sandy habitats have different patterns of brain organisation. In particular, fishes from spatially complex rock pool habitats were found to have larger telencephalons, while those from simple homogenous sandy shores had a larger optic tectum. Where possible we recommend that micro-CT be used in brain volume analyses, as it allows for measurements without destruction of the brain and fast identification and quantification of individual brain lobes, and minimises many of the biases resulting from the histology and ellipsoid methods.

Gene delivery to the spinal cord using MRI-guided focused ultrasound

Non-invasive gene delivery across the blood-spinal cord barrier (BSCB) remains a challenge for treatment of spinal cord injury and disease. Here, we demonstrate the use of magnetic resonance image-guided focused ultrasound (MRIgFUS) to mediate non-surgical gene delivery to the spinal cord using self-complementary adeno-associated virus serotype 9 (scAAV9). scAAV9 encoding green fluorescent protein (GFP) was injected intravenously in rats at three dosages: 4 × 10(8), 2 × 10(9) and 7 × 10(9) vector genomes per gram (VG g(-1)). MRIgFUS allowed for transient, targeted permeabilization of the BSCB through the interaction of focused ultrasound (FUS) with systemically injected Definity lipid-shelled microbubbles. Viral delivery at 2 × 10(9) and 7 × 10(9) VG g(-1) leads to robust GFP expression in FUS-targeted regions of the spinal cord. At a dose of 2 × 10(9) VG g(-1), GFP expression was found in 36% of oligodendrocytes, and in 87% of neurons in FUS-treated areas. FUS applications to the spinal cord could address a long-term goal of gene therapy: delivering vectors from the circulation to diseased areas in a non-invasive manner.

Potential and limitations of X-Ray micro-computed tomography in arthropod neuroanatomy: a methodological and comparative survey

Classical histology or immunohistochemistry combined with fluorescence or confocal laser scanning microscopy are common techniques in arthropod neuroanatomy, and these methods often require time-consuming and difficult dissections and sample preparations. Moreover, these methods are prone to artifacts due to compression and distortion of tissues, which often result in information loss and especially affect the spatial relationships of the examined parts of the nervous system in their natural anatomical context. Noninvasive approaches such as X-ray micro-computed tomography (micro-CT) can overcome such limitations and have been shown to be a valuable tool for understanding and visualizing internal anatomy and structural complexity. Nevertheless, knowledge about the potential of this method for analyzing the anatomy and organization of nervous systems, especially of taxa with smaller body size (e.g., many arthropods), is limited. This study set out to analyze the brains of selected arthropods with micro-CT, and to compare these results with available histological and immunohistochemical data. Specifically, we explored the influence of different sample preparation procedures. Our study shows that micro-CT is highly suitable for analyzing arthropod neuroarchitecture in situ and allows specific neuropils to be distinguished within the brain to extract quantitative data such as neuropil volumes. Moreover, data acquisition is considerably faster compared with many classical histological techniques. Thus, we conclude that micro-CT is highly suitable for targeting neuroanatomy, as it reduces the risk of artifacts and is faster than classical techniques.

In vivo micro-CT imaging of untreated and irradiated orthotopic glioblastoma xenografts in mice: capabilities, limitations and a comparison with bioluminescence imaging

Small animal imaging is of increasing relevance in biomedical research. Studies systematically assessing the diagnostic accuracy of contrast-enhanced in vivo micro-CT of orthotopic glioma xenografts in mice do not exist. NOD/SCID/γc(-/-) mice (n = 27) underwent intracerebral implantation of 2.5 × 10(6) GFP-Luciferase-transduced U87MG cells. Mice underwent bioluminescence imaging (BLI) to detect tumor growth and afterwards repeated contrast-enhanced (300 µl Iomeprol i.v.) micro-CT imaging (80 kV, 75 µAs, 360° rotation, 1,000 projections, 33 s scan time, resolution 40 × 40 × 53 µm, 0.5 Gy/scan). Presence of tumors, tumor diameter and tumor volume in micro-CT were rated by two independent readers. Results were compared with histological analyses. Six mice with tumors confirmed by micro-CT received fractionated irradiation (3 × 5 Gy every other day) using the micro-CT (5 mm pencil beam geometry). Repeated micro-CT scans were tolerated well. Tumor engraftment rate was 74 % (n = 20). In micro-CT, mean tumor volume was 30 ± 33 mm(3), and the smallest detectable tumor measured 360 × 620 µm. The inter-rater agreement (n = 51 micro-CT scans) for the item tumor yes/no was excellent (Spearman-Rho = 0.862, p < 0.001). Sensitivity and specificity of micro-CT were 0.95 and 0.71, respectively (PPV = 0.91, NPV = 0.83). BLI on day 21 after tumor implantation had a sensitivity and specificity of 0.90 and 1.0, respectively (PPV = 1.0, NPV = 0.5). Maximum tumor diameter and volume in micro-CT and histology correlated excellently (tumor diameter: 0.929, p < 0.001; tumor volume: 0.969, p < 0.001, n = 17). Irradiated animals showed a large central tumor necrosis. Longitudinal contrast enhanced micro-CT imaging of brain tumor growth in live mice is feasible at high sensitivity levels and with excellent inter-rater agreement and allows visualization of radiation effects.

Nanoparticle-based CT imaging technique for longitudinal and quantitative stem cell tracking within the brain: application in neuropsychiatric disorders

A critical problem in the development and implementation of stem cell-based therapy is the lack of reliable, noninvasive means to image and trace the cells post-transplantation and evaluate their biodistribution, final fate, and functionality. In this study, we developed a gold nanoparticle-based CT imaging technique for longitudinal mesenchymal stem cell (MSC) tracking within the brain. We applied this technique for noninvasive monitoring of MSCs transplanted in a rat model for depression. Our research reveals that cell therapy is a potential approach for treating neuropsychiatric disorders. Our results, which demonstrate that cell migration could be detected as early as 24 h and up to one month post-transplantation, revealed that MSCs specifically navigated and homed to distinct depression-related brain regions. We further developed a noninvasive quantitative CT ruler, which can be used to determine the number of cells residing in a specific brain region, without tissue destruction or animal scarification. This technique may have a transformative effect on cellular therapy, both for basic research and clinical applications.

Revival of forgotten characters and modern imaging techniques help to produce a robust phylogeny of the Diplopoda (Arthropoda, Myriapoda)

The external and internal anatomy of millipedes (Diplopoda) is poorly known compared to some of the other myriapod and arthropod groups. Due to both language barriers, which hindered the assessment of the character-rich older literature, and non-phylogenetic thinking, our knowledge of morphological characters useful for phylogenetic work diminished over the last decades. Here, a new character matrix with 64 characters, mainly derived from old literature data, is used to reconstruct a phylogeny of Diplopoda. As a tool to further our knowledge about the morphology of the different millipede orders, we show how micro-computer tomography (μCT) can be used to assess and illustrate specific parts of the Platydesmida. With the advent of μCT it is now possible to analyse many taxa and characters in a comparatively short time. A focus is put on potential phylogenetically useful characters. Our results support a Verhoeffian classification of the Diplopoda: Polyxenida + Chilognatha. Pentazonia are the sistergroup to the Helminthomorpha. Colobognatha form the sistergroup to Eugnatha, the latter split into monophyletic Juliformia and Polydesmida + Nematophora.

Contrasting of biological samples for X-ray synchrotron microtomography

The method of contrasting with iodine ions was developed to obtain high-resolution 3D images of large biological specimens using a synchrotron X-ray microtomography unit. It was shown that the samples (late mouse embryos) treated with 50% Lugol solution with addition of 25% ethanol for 48 h followed by a 48-h washout in phosphate buffered saline had maximum contrast and lowest compression artifacts. Processing of samples by this protocol allowed detecting zones of active proliferation. Incubation of brain samples for 120 h in 7.6% meglumine/sodium diatrizoate without washout ensured the best contrast during myelin identification.

A coming of age: advanced imaging technologies for characterising the developing mouse

The immense challenge of annotating the entire mouse genome has stimulated the development of cutting-edge imaging technologies in a drive for novel information. These techniques promise to improve understanding of the genes involved in embryo development, at least one third of which have been shown to be essential. Aligning advanced imaging technologies with biological needs will be fundamental to maximising the number of phenotypes discovered in the coming years. International efforts are underway to meet this challenge through an integrated and sophisticated approach to embryo phenotyping. We review rapid advances made in the imaging field over the past decade and provide a comprehensive examination of the relative merits of current and emerging techniques. The aim of this review is to provide a guide to state-of-the-art embryo imaging that will enable informed decisions as to which technology to use and fuel conversations between expert imaging laboratories, researchers, and core mouse production facilities.

Design and implementation of a custom built optical projection tomography system

Optical projection tomography (OPT) is an imaging modality that has, in the last decade, answered numerous biological questions owing to its ability to view gene expression in 3 dimensions (3D) at high resolution for samples up to several cm³. This has increased demand for a cabinet OPT system, especially for mouse embryo phenotyping, for which OPT was primarily designed for. The Medical Research Council (MRC) Technology group (UK) released a commercial OPT system, constructed by Skyscan, called the Bioptonics OPT 3001 scanner that was installed in a limited number of locations. The Bioptonics system has been discontinued and currently there is no commercial OPT system available. Therefore, a few research institutions have built their own OPT system, choosing parts and a design specific to their biological applications. Some of these custom built OPT systems are preferred over the commercial Bioptonics system, as they provide improved performance based on stable translation and rotation stages and up to date CCD cameras coupled with objective lenses of high numerical aperture, increasing the resolution of the images. Here, we present a detailed description of a custom built OPT system that is robust and easy to build and install. Included is a hardware parts list, instructions for assembly, a description of the acquisition software and a free download site, and methods for calibration. The described OPT system can acquire a full 3D data set in 10 minutes at 6.7 micron isotropic resolution. The presented guide will hopefully increase adoption of OPT throughout the research community, for the OPT system described can be implemented by personnel with minimal expertise in optics or engineering who have access to a machine shop.