In vivo imaging in experimental spinal cord injury – Techniques and trends

Introduction

Traumatic Spinal Cord Injury (SCI) is one of the leading causes of disability in the world. Treatment is limited to supportive care and no curative therapy exists. Experimental research to understand the complex pathophysiology and potential mediators of spinal cord regeneration is essential to develop innovative translational therapies. A multitude of experimental imaging methods to monitor spinal cord regeneration in vivo have developed over the last years. However, little literature exists to deal with advanced imaging methods specifically available in SCI research.

Research Question

This systematic literature review examines the current standards in experimental imaging in SCI allowing for in vivo imaging of spinal cord regeneration on a neuronal, vascular, and cellular basis.

Material and Methods

Articles were included meeting the following criteria: experimental research, original studies, rodent subjects, and intravital imaging. Reviewed in detail are microstructural and functional Magnetic Resonance Imaging, Micro-Computed Tomography, Laser Speckle Imaging, Very High Resolution Ultrasound, and in vivo microscopy techniques.

Results

Following the PRISMA guidelines for systematic reviews, 689 articles were identified for review, of which 492 were sorted out after screening and an additional 104 after detailed review. For qualitative synthesis 93 articles were included in this publication.

Discussion and Conclusion

With this study we give an up-to-date overview about modern experimental imaging techniques with the potential to advance the knowledge on spinal cord regeneration following SCI. A thorough knowledge of the strengths and limitations of the reviewed techniques will help to optimally exploit our current experimental armamentarium in the field.

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In vivo imaging is essential to enhance the understanding of SCI pathophysiology.

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Multiple experimental imaging methods have evolved over the past years.

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Detailed review of in vivo (f)MRI, μCT, VHRUS, and Microcopy in experimental SCI.

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Experimental imaging allows for longitudinal examination to the cellular level.

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Knowledge of the strengths and limitations is essential for future research.

The Correlation between Targeted Contrast-Enhanced Ultrasound Imaging and Tumor Neovascularization of Ovarian Cancer Xenografts in Nude Mice

In order to explore the correlation between targeted contrast-enhanced ultrasound imaging and tumor neovascularization of ovarian cancer xenografts in nude mice, a total of 49 nude mice were selected and randomly divided into 1-week group, 2-week group, 3-week group, 4-week group, 5-week group, 6-week group, and 7-week group according to their ovarian cancer xenografts' growth time, with 7 ovarian cancer xenografts in each group. After preparing antibody-carrying targeted contrast agent, each group of xenografts performed normal and targeted contrast ultrasound examinations to obtain peak intensity, time to peak, and other imaging parameters; then, those ovarian cancer xenografts were sacrificed for pathological analysis: the neovascular density and antibody expression of the cancer xenografts at different stages were observed and counted, and the correlation between targeted contrast-enhanced ultrasound parameters and tumor neovascular densities of the ovarian cancer xenografts was analyzed. The results show that the peak intensities of targeted contrast ultrasound imaging are greater than that of ordinary ultrasound imaging in the 2-, 3-, 4-, and 5-week groups with statistically significant differences (P < 0.05); the time to peak of targeted contrast ultrasound imaging is shorter than that of ordinary ultrasound imaging in the 2-, 3-, 4-, and 5-week groups with statistically significant differences (P < 0.05); there is a positive correlation between the peak intensities of targeted contrast ultrasound imaging and tumor neovascular densities of the ovarian cancer xenografts in the 2-, 3-, and 4-week group (r 2 = 0.645, r 3 = 0.668, and r 4 = 0.693, P < 0.05); there is a negative correlation between the time to peak of targeted contrast ultrasound imaging and tumor neovascular densities of the ovarian cancer xenografts in the 2-, 3-, and 4-week groups (r 2 = -0.669, r 3 = -0.692, and r 4 = -0.704, P < 0.05). Therefore, the targeted contrast-enhanced ultrasound imaging parameters have a certain correlation with tumor neovascular density of ovarian cancer xenografts in nude mice and this correlation is more significant in the early stage of ovarian cancer; hence, targeted contrast-enhanced ultrasound imaging may provide a new method, new idea, and new basis for the diagnosis of early ovarian cancer.

Quantitative Measurement of Erythrocyte Aggregation as a Systemic Inflammatory Marker by Ultrasound Imaging: A Systematic Review

This systematic review is aimed at answering two questions: (i) Is erythrocyte aggregation a useful biomarker in assessing systemic inflammation? (ii) Does quantitative ultrasound imaging provide the non-invasive option to measure erythrocyte aggregation in real time? The search was executed through bibliographic electronic databases CINAHL, EMB Review, EMBASE, MEDLINE, PubMed and the grey literature. The majority of studies correlated elevated erythrocyte aggregation with inflammatory blood markers for several pathologic states. Some studies used "erythrocyte aggregation" as an established marker of systemic inflammation. There were limited but promising articles regarding the use of quantitative ultrasound spectroscopy to monitor erythrocyte aggregation. Similarly, there were limited studies that used other ultrasound techniques to measure systemic inflammation. The quantitative measurement of erythrocyte aggregation has the potential to be a routine clinical marker of inflammation as it can reflect the cumulative inflammatory dynamics in vivo, is relatively simple to measure, is cost-effective and has a rapid turnaround time. Technologies like quantitative ultrasound spectroscopy that can measure erythrocyte aggregation non-invasively and in real time may offer the advantage of continuous monitoring of the inflammation state and, thus, may help in rapid decision making in a critical care setup.