Visualization of rodent brain tumor angiogenesis and effects of antiangiogenic treatment using 3D ΔR2-μMRA

Large Scale in vivo Acquisition, Segmentation and 3D Reconstruction of Cortical Vasculature using μ Doppler Ultrasound Imaging

The brain is composed of a dense and ramified vascular network of arteries, veins and capillaries of various sizes. One way to assess the risk of cerebrovascular pathologies is to use computational models to predict the physiological effects of reduced blood supply and correlate these responses with observations of brain damage. Therefore, it is crucial to establish a detailed 3D organization of the brain vasculature, which could be used to develop more accurate in silico models. To this end, we have adapted our functional ultrasound imaging platform, previously designed for recording large scale activity, to enable rapid and reproducible acquisition, segmentation and reconstruction of the cortical vasculature. For the first time, it allows us to digitize the cortical ∼ 100 - μ m3 spatial resolution. Unlike most available strategies, our approach can be performed in vivo within minutes. Moreover, it is easy to implement since it requires neither exogenous contrast agents nor long post-processing time. Therefore, we performed a cortex-wide reconstruction of the vasculature and its quantitative analysis, including i) classification of descending arteries versus ascending veins in more than 1500 vessels/animal and ii) rapid estimation of their length. Importantly, we confirmed the relevance of our approach in a model of cortical stroke, which allows rapid visualization of the ischemic lesion. This development contributes to extending the capabilities of ultrasound neuroimaging to better understand cerebrovascular pathologies such as stroke, vascular cognitive impairment and brain tumors, and is highly scalable for the clinic.

Impact of the immune molecular profile of the tumor microenvironment on the prognosis of NSCLC

The present study aimed to clarify the association between macrophages, tumor neo-vessels and programmed cell death-ligand 1 (PD-L1) in the tumor microenvironment and the clinicopathological features of patients with non-small cell lung cancer (NSCLC), and to explore the prognostic factors of stromal features in NSCLC. To determine this, tissue microarrays containing samples of 92 patients with NSCLC were studied using immunohistochemistry and immunofluorescence. The quantitative data demonstrated that in tumor islets, the number of CD68⁺ and CD206⁺ tumor-associated macrophages (TAMs) was 8-348 (median, 131) and 2-220 (median, 52), respectively (P<0.001). In tumor stroma, the number of CD68⁺ and CD206⁺ TAMs was 23-412 (median, 169) and 7-358 (median, 81), respectively (P<0.001). The number of CD68⁺ TAMs in each location of the tumor islets and tumor stroma was significantly higher than that of CD206⁺ TAMs, and they were significantly correlated (P<0.0001). The quantitative density of CD105 and PD-L1 in tumor tissues was 19-368 (median, 156) and 9-493 (median, 103), respectively. Survival analysis revealed that a high density of CD68⁺ TAMs in tumor stroma and islets and a high density of CD206⁺ TAMs and PD-L1 in tumor stroma were associated with worse prognosis (both P<0.05). Collectively, the survival analysis demonstrated that the high-density group was related to a worse prognosis regardless of combined neo-vessels and PD-L1 expression with the CD68⁺ TAMs in tumor islets and stroma, or CD206⁺ TAMs in tumor islets and stroma. To the best of our knowledge, the present study was the first to provide a multi-component combined prognostic survival analysis of different types of macrophages in different regions with tumor neo-vessels and PD-L1, which demonstrated the importance of macrophages in tumor stroma.

An artificial intelligence framework and its bias for brain tumor segmentation: A narrative review

BACKGROUND

Artificial intelligence (AI) has become a prominent technique for medical diagnosis and represents an essential role in detecting brain tumors. Although AI-based models are widely used in brain lesion segmentation (BLS), understanding their effectiveness is challenging due to their complexity and diversity. Several reviews on brain tumor segmentation are available, but none of them describe a link between the threats due to risk-of-bias (RoB) in AI and its architectures. In our review, we focused on linking RoB and different AI-based architectural Cluster in popular DL framework. Further, due to variance in these designs and input data types in medical imaging, it is necessary to present a narrative review considering all facets of BLS.

APPROACH

The proposed study uses a PRISMA strategy based on 75 relevant studies found by searching PubMed, Scopus, and Google Scholar. Based on the architectural evolution, DL studies were subsequently categorized into four classes: convolutional neural network (CNN)-based, encoder-decoder (ED)-based, transfer learning (TL)-based, and hybrid DL (HDL)-based architectures. These studies were then analyzed considering 32 AI attributes, with clusters including AI architecture, imaging modalities, hyper-parameters, performance evaluation metrics, and clinical evaluation. Then, after these studies were scored for all attributes, a composite score was computed, normalized, and ranked. Thereafter, a bias cutoff (AP(ai)Bias 1.0, AtheroPoint, Roseville, CA, USA) was established to detect low-, moderate- and high-bias studies.

CONCLUSION

The four classes of architectures, from best-to worst-performing, are TL > ED > CNN > HDL. ED-based models had the lowest AI bias for BLS. This study presents a set of three primary and six secondary recommendations for lowering the RoB.

One-pot synthesis of carboxymethyl-dextran coated iron oxide nanoparticles (CION) for preclinical fMRI and MRA applications

Superparamagnetic iron-oxide nanoparticles are robust contrast agents for magnetic resonance imaging (MRI) used for sensitive structural and functional mapping of the cerebral blood volume (CBV) when administered intravenously. To date, many CBV-MRI studies are conducted with Feraheme, manufactured for the clinical treatment of iron-deficiency. Unfortunately, Feraheme is currently not available outside the United States due to commercial and regulatory constraints, making CBV-MRI methods either inaccessible or very costly to achieve. To address this barrier, we developed a simple, one-pot recipe to synthesize Carboxymethyl-dextran coated Iron Oxide Nanoparticles, namely, “CION”, suitable for preclinical CBV-MRI applications. Here we disseminate a step-by-step instruction of our one-pot synthesis protocol, which allows CION to be produced in laboratories with minimal cost. We also characterized different CION-conjugations by manipulating polymer to metal stoichiometric ratio in terms of their size, surface chemistry, and chemical composition, and shifts in MR relaxivity and pharmacokinetics. We performed several proof-of-concept experiments in vivo, demonstrating the utility of CION for functional and structural MRI applications, including hypercapnic CO₂ challenge, visual stimulation, targeted optogenetic stimulation, and microangiography. We also present evidence that CION can serve as a cross-modality research platform by showing concurrent in vivo optical and MRI measurement of CBV using fluorescent-labeled CION. The simplicity and cost-effectiveness of our one-pot synthesis method should allow researchers to reproduce CION and tailor the relaxivity and pharmacokinetics according to their imaging needs. It is our hope that this work makes CBV-MRI more openly available and affordable for a variety of research applications.

Triple-negative breast cancer: new treatment strategies in the era of precision medicine

Triple-negative breast cancer (TNBC) remains the most aggressive cluster of all breast cancers, which is due to its rapid progression, high probabilities of early recurrence, and distant metastasis resistant to standard treatment. Following the advances in cancer genomics and transcriptomics that can illustrate the comprehensive profiling of this heterogeneous disease, it is now possible to identify different subclasses of TNBC according to both intrinsic signals and extrinsic microenvironment, which have a huge influence on predicting response to established therapies and picking up novel therapeutic targets for each cluster. In this review, we summarize basic characteristics and critical subtyping systems of TNBC, and particularly discuss newly found prospective targets and relevant medications, which were proved promising in clinical trials, thus shedding light on the future development of precision treatment strategies.

Cerebrovascular MRI in the mouse without an exogenous contrast agent

PURPOSE

To assess the effect of a variety of anesthetic regimes on T 2 ∗ -weighted MRI of the mouse brain and to determine the optimal regimes to perform T 2 ∗ -weighted MRI of the mouse cerebrovasculature without a contrast agent.

METHODS

Twenty mice were imaged with a 3D T 2 ∗ -weighted sequence under isoflurane, dexmedetomidine, or ketamine-xylazine anesthesia with a fraction of inspired oxygen varied between 10% and 95% + 5% CO2 . Some mice were also imaged after an injection of an iron oxide contrast agent as a positive control. For every regime, whole brain vessel conspicuity was visually assessed and the apparent vessel density in the cortex was quantified and compared.

RESULTS

The commonly used isoflurane anesthetic leads to poor vessel conspicuity for fraction of inspired oxygen higher or equal to 21%. Dexmedetomidine and ketamine-xylazine enable the visualization of a significantly larger portion of the vasculature for the same breathing gas. Under isoflurane anesthesia, the fraction of inspired oxygen must be lowered to between 10% and 14% to obtain similar vessel conspicuity. Initial results on automatic segmentation of veins and arteries using the iron oxide positive control are also reported.

CONCLUSION

T 2 ∗ -weighted MRI in combination with an appropriate anesthetic regime can be used to visualize the mouse cerebrovasculature without a contrast agent. The differences observed between regimes are most likely caused by blood-oxygen level dependent effects, highlighting the important impact of the anesthetic regimes on cerebral blood oxygenation of the mouse brain at rest.

Micro-imaging of Brain Cancer Radiation Therapy Using Phase-contrast Computed Tomography

PURPOSE

Experimental neuroimaging provides a wide range of methods for the visualization of brain anatomic morphology down to subcellular detail. Still, each technique-specific detection mechanism presents compromises among the achievable field-of-view size, spatial resolution, and nervous tissue sensitivity, leading to partial sample coverage, unresolved morphologic structures, or sparse labeling of neuronal populations and often also to obligatory sample dissection or other sample invasive manipulations. X-ray phase-contrast imaging computed tomography (PCI-CT) is an experimental imaging method that simultaneously provides micrometric spatial resolution, high soft-tissue sensitivity, and ex vivo full organ rodent brain coverage without any need for sample dissection, staining or labeling, or contrast agent injection. In the present study, we explored the benefits and limitations of PCI-CT use for in vitro imaging of normal and cancerous brain neuromorphology after in vivo treatment with synchrotron-generated x-ray microbeam radiation therapy (MRT), a spatially fractionated experimental high-dose radiosurgery. The goals were visualization of the MRT effects on nervous tissue and a qualitative comparison of the results to the histologic and high-field magnetic resonance imaging findings.

METHODS AND MATERIALS

MRT was administered in vivo to the brain of both healthy and cancer-bearing rats. At 45 days after treatment, the brain was dissected out and imaged ex vivo using propagation-based PCI-CT.

RESULTS

PCI-CT visualizes the brain anatomy and microvasculature in 3 dimensions and distinguishes cancerous tissue morphology, necrosis, and intratumor accumulation of iron and calcium deposits. Moreover, PCI-CT detects the effects of MRT throughout the treatment target areas (eg, the formation of micrometer-thick radiation-induced tissue ablation). The observed neurostructures were confirmed by histologic and immunohistochemistry examination and related to the micro-magnetic resonance imaging data.

CONCLUSIONS

PCI-CT enabled a unique 3D neuroimaging approach for ex vivo studies on small animal models in that it concurrently delivers high-resolution insight of local brain tissue morphology in both normal and cancerous micro-milieu, localizes radiosurgical damage, and highlights the deep microvasculature. This method could assist experimental small animal neurology studies in the postmortem evaluation of neuropathology or treatment effects.

Impact of Blood Vessel Quantity and Vascular Expression of CD133 and ICAM-1 on Survival of Glioblastoma Patients

Glioblastoma (GB) is the most angiogenic tumor. Nevertheless, antiangiogenic therapy has not shown significant clinical efficacy. The aim of this study was to assess blood vessel characteristics on survival of GB patients. Surgically excised GB tissues were histologically examined for overall proportion of glomeruloid microvascular proliferation (MP) and the total number of blood vessels. Also, immunohistochemical vascular staining intensities of CD133 and ICAM-1 were determined. Vessel parameters were correlated with patients' overall survival. The survival time depended on the number of blood vessels (p = 0.03) but not on the proportion of MP. Median survival times for patients with low (<median) and high (≥median) number of blood vessels were 9.0 months (95% CI: 7.5–10.5) and 12.0 months (95% CI: 9.3–14.7). Also, median survival times for patients with low (<median) and high (≥median) vascular expression level of CD133 were 9.0 months (95% CI: 8.0–10.1) and 12.0 months (95% CI: 10.3–13.7). In contrast, the staining intensity of vascular ICAM-1 did not affect survival. In multivariate analysis, the number of blood vessels emerged as an independent predictor for longer overall survival (HR: 2.4, 95% CI: 1.2–5.0, p = 0.02). For success in antiangiogenic therapy, better understanding about tumor vasculature biology is needed.

UTE-ΔR2 -ΔR2 * combined MR whole-brain angiogram using dual-contrast superparamagnetic iron oxide nanoparticles

The ability to visualize whole-brain vasculature is important for quantitative in vivo investigation of vascular malfunctions in cerebral small vessel diseases, including cancer, stroke and neurodegeneration. Transverse relaxation-based ΔR2 and ΔR2 * MR angiography (MRA) provides improved vessel-tissue contrast in animal deep brain with the aid of intravascular contrast agents; however, it is susceptible to orientation dependence, air-tissue interface artifacts and vessel size overestimation. Dual-mode MRA acquisition with superparamagnetic iron oxide nanoparticles (SPION) provides a unique opportunity to systematically compare and synergistically combine both longitudinal (R1 ) and transverse (ΔR2 and ΔR2 *) relaxation-based MRA. Through Monte Carlo (MC) simulation and MRA experiments in normal and tumor-bearing animals with intravascular SPION, we show that ultrashort TE (UTE) MRA acquires well-defined vascularization on the brain surface, minimizing air-tissue artifacts, and combined ΔR2 and ΔR2 * MRA simultaneously improves the sensitivity to intracortical penetrating vessels and reduces vessel size overestimation. Consequently, UTE-ΔR2 -ΔR2 * combined MRA complements the shortcomings of individual angiograms and provides a strategy to synergistically merge longitudinal and transverse relaxation effects to generate more robust in vivo whole-brain micro-MRA. Copyright © 2016 John Wiley & Sons, Ltd.

Functional assessment of glioma pathogenesis by in vivo multi-parametric magnetic resonance imaging and in vitro analyses

Gliomas are aggressive brain tumors with poor prognosis. In this study, we report a novel approach combining both in vivo multi-parametric MRI and in vitro cell culture assessments to evaluate the pathogenic development of gliomas. Osteopontin (OPN), a pleiotropic factor, has been implicated in the formation and progression of various human cancers, including gliomas, through its functions in regulating cell proliferation, survival, angiogenesis, and migration. Using rat C6 glioma model, the combined approach successfully monitors the acquisition and decrease of cancer hallmarks. We show that knockdown of the expression of OPN reduces C6 cell proliferation, survival, viability and clonogenicity in vitro, and reduces tumor burden and prolongs animal survival in syngeneic rats. OPN depletion is associated with reduced tumor growth, decreased angiogenesis, and an increase of tumor-associated metabolites, as revealed by T2-weighted images, diffusion-weighted images, K^trans maps, and 1H-MRS, respectively. These strategies allow us to define an important role of OPN in conferring cancer hallmarks, which can be further applied to assess the functional roles of other candidate genes in glioma. In particular, the non-invasive multi-parametric MRI measurement of cancer hallmarks related to proliferation, angiogenesis and altered metabolism may serve as a useful tool for diagnosis and for patient management.

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

Background

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

Purpose

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

Material and Methods

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

Results

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

Conclusion

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

High-resolution structural and functional assessments of cerebral microvasculature using 3D Gas ΔR2*-mMRA

The ability to evaluate the cerebral microvascular structure and function is crucial for investigating pathological processes in brain disorders. Previous angiographic methods based on blood oxygen level-dependent (BOLD) contrast offer appropriate visualization of the cerebral vasculature, but these methods remain to be optimized in order to extract more comprehensive information. This study aimed to integrate the advantages of BOLD MRI in both structural and functional vascular assessments. The BOLD contrast was manipulated by a carbogen challenge, and signal changes in gradient-echo images were computed to generate ΔR2* maps. Simultaneously, a functional index representing the regional cerebral blood volume was derived by normalizing the ΔR2* values of a given region to those of vein-filled voxels of the sinus. This method is named 3D gas ΔR2*-mMRA (microscopic MRA). The advantages of using 3D gas ΔR2*-mMRA to observe the microvasculature include the ability to distinguish air-tissue interfaces, a high vessel-to-tissue contrast, and not being affected by damage to the blood-brain barrier. A stroke model was used to demonstrate the ability of 3D gas ΔR2*-mMRA to provide information about poststroke revascularization at 3 days after reperfusion. However, this technique has some limitations that cannot be overcome and hence should be considered when it is applied, such as magnifying vessel sizes and predominantly revealing venous vessels.