Brain iron deposition after Ferumoxytol-enhanced MRI: A study of Porcine Brains

Exploring the diagnostic potential: magnetic particle imaging for brain diseases

Brain diseases are characterized by high incidence, disability, and mortality rates. Their elusive nature poses a significant challenge for early diagnosis. Magnetic particle imaging (MPI) is a novel imaging technique with high sensitivity, high temporal resolution, and no ionizing radiation. It relies on the nonlinear magnetization response of superparamagnetic iron oxide nanoparticles (SPIONs), allowing visualization of the spatial concentration distribution of SPIONs in biological tissues. MPI is expected to become a mainstream technology for the early diagnosis of brain diseases, such as cancerous, cerebrovascular, neurodegenerative, and inflammatory diseases. This review provides an overview of the principles of MPI, explores its potential applications in brain diseases, and discusses the prospects for the diagnosis and management of these diseases.

Iron oxide nanoparticles coated with bioactive materials: a viable theragnostic strategy to improve osteosarcoma treatment

Osteosarcoma (OS) is distinguished as a high-grade malignant tumor, characterized by rapid systemic metastasis, particularly to the lungs, resulting in very low survival rates. Understanding the complexities of tumor development and mutation is the need of the hour for the advancement of targeted therapies in cancer care. A significant innovation in this area is the use of nanotechnology, specifically nanoparticles, to tackle various challenges in cancer treatment. Iron oxide nanoparticles stand out in both therapeutic and diagnostic applications, offering a versatile platform for targeted drug delivery, hyperthermia, magneto-thermal therapy, and combinational therapy using modulation of ferroptosis pathways. These nanoparticles are easy to synthesize, non-toxic, biocompatible, and display enhanced circulation time within the system. They can also be easily conjugated to anti-cancer drugs, targeting agents, or genetic vectors that respond to specific stimuli or pH changes. The surface functionalization of these nanoparticles using bioactive molecules unveils a promising and effective nanoparticle system for assisting osteosarcoma therapy. This review will summarize the current conventional therapies for osteosarcoma and their disadvantages, the synthesis and modification of iron oxide nanoparticles documented in the literature, cellular targeting and uptake mechanism, with focus on their functionalization using natural biomaterials and application strategies towards management of osteosarcoma. The review also compiles the translational challenges and future prospects that must be addressed for clinical advancements of iron oxide based osteosarcoma treatment in the future.

Targeted Nanotheransotics: Integration of Preclinical MRI and CT in the Molecular Imaging and Therapy of Advanced Diseases

The integration of preclinical magnetic resonance imaging (MRI) and computed tomography (CT) methods has significantly enhanced the area of therapy and imaging of targeted nanomedicine. Nanotheranostics, which make use of nanoparticles, are a significant advancement in MRI and CT imaging. In addition to giving high-resolution anatomical features and functional information simultaneously, these multifunctional agents improve contrast when used. In addition to enabling early disease detection, precise localization, and personalised therapy monitoring, they also enable early disease detection. Fusion of MRI and CT enables precise in vivo tracking of drug-loaded nanoparticles. MRI, which provides real-time monitoring of nanoparticle distribution, accumulation, and release at the cellular and tissue levels, can be used to assess the efficacy of drug delivery systems. The precise localization of nanoparticles within the body is achievable through the use of CT imaging. This technique enhances the capabilities of MRI by providing high-resolution anatomical information. CT also allows for quantitative measurements of nanoparticle concentration, which is essential for evaluating the pharmacokinetics and biodistribution of nanomedicine. In this article, we emphasize the integration of preclinical MRI and CT into molecular imaging and therapy for advanced diseases.

Super High Contrast USPIO-Enhanced Cerebrovascular Angiography Using Ultrashort Time-to-Echo MRI

Background

Ferumoxytol (Ferahame, AMAG Pharmaceuticals, Waltham, MA) is increasingly used off-label as an MR contrast agent due to its relaxivity and safety profiles. However, its potent T2∗ relaxivity limits achievable T1-weighted positive contrast and leads to artifacts in standard MRI protocols. Optimization of protocols for ferumoxytol deployment is necessary to realize its potential.

Methods

We present first-in-human clinical results of the Quantitative Ultrashort Time-to-Echo Contrast Enhanced (QUTE-CE) MRA technique using the superparamagnetic iron oxide nanoparticle agent ferumoxytol for vascular imaging of the head/brain in 15 subjects at 3.0T. The QUTE-CE MRA method was implemented on a 3T scanner using a stack-of-spirals 3D Ultrashort Time-to-Echo sequence. Time-of-flight MRA and standard TE T1-weighted (T1w) images were also collected. For comparison, gadolinium-enhanced blood pool phase images were obtained retrospectively from clinical practice. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and intraluminal signal heterogeneity (ISH) were assessed and compared across approaches with Welch's two-sided t-test.

Results

Fifteen volunteers (54 ± 17 years old, 9 women) participated. QUTE-CE MRA provided high-contrast snapshots of the arterial and venous networks with lower intraluminal heterogeneity. QUTE-CE demonstrated significantly higher SNR (1707 ± 226), blood-tissue CNR (1447 ± 189), and lower ISH (0.091 ± 0.031) compared to ferumoxytol T1-weighted (551 ± 171; 319 ± 144; 0.186 ± 0.066, respectively) and time-of-flight (343 ± 104; 269 ± 82; 0.190 ± 0.016, respectively), with p < 0.001 in each comparison. The high CNR increased the depth of vessel visualization. Vessel lumina were captured with lower heterogeneity.

Conclusion

Quantitative Ultrashort Time-to-Echo Contrast-Enhanced MR angiography provides approximately 5-fold superior contrast with fewer artifacts compared to other contrast-enhanced vascular imaging techniques using ferumoxytol or gadolinium, and to noncontrast time-of-flight MR angiography, for clinical vascular imaging. This trial is registered with NCT03266848.

Use of metal-based contrast agents for in vivo MR and CT imaging of phagocytic cells in neurological pathologies

The activation of phagocytic cells is a hallmark of many neurological diseases. Imaging them in their 3-dimensional cerebral environment over time is crucial to better understand their role in disease pathogenesis and to monitor their potential therapeutic effects. Phagocytic cells have the ability to internalize metal-based contrast agents both in vitro and in vivo and can thus be tracked by magnetic resonance imaging (MRI) or computed tomography (CT). In this review article, we summarize the different labelling strategies, contrast agents, and in vivo imaging modalities that can be used to monitor cells with phagocytic activity in the central nervous system using MRI and CT, with a focus on clinical applications. Metal-based nanoparticle contrast agents such as gadolinium, gold and iron are ideal candidates for these applications as they have favourable magnetic and/or radiopaque properties and can be fine-tuned for optimal uptake by phagocytic cells. However, they also come with downsides due to their potential toxicity, especially in the brain where they might accumulate. We therefore conclude our review by discussing the pitfalls, safety and potential for clinical translation of these metal-based neuroimaging techniques. Early results in patients with neuropathologies such as multiple sclerosis, stroke, trauma, cerebral aneurysm and glioblastoma are promising. If the challenges represented by safety issues are overcome, phagocytic cells imaging will be a very valuable tool for studying and understanding the inflammatory response and evaluating treatments that aim at mitigating this response in patients with neurological diseases.

How to stop using gadolinium chelates for magnetic resonance imaging: clinical-translational experiences with ferumoxytol

Gadolinium chelates have been used as standard contrast agents for clinical MRI for several decades. However, several investigators recently reported that rare Earth metals such as gadolinium are deposited in the brain for months or years. This is particularly concerning for children, whose developing brain is more vulnerable to exogenous toxins compared to adults. Therefore, a search is under way for alternative MR imaging biomarkers. The United States Food and Drug Administration (FDA)-approved iron supplement ferumoxytol can solve this unmet clinical need: ferumoxytol consists of iron oxide nanoparticles that can be detected with MRI and provide significant T1- and T2-signal enhancement of vessels and soft tissues. Several investigators including our research group have started to use ferumoxytol off-label as a new contrast agent for MRI. This article reviews the existing literature on the biodistribution of ferumoxytol in children and compares the diagnostic accuracy of ferumoxytol- and gadolinium-chelate-enhanced MRI. Iron oxide nanoparticles represent a promising new class of contrast agents for pediatric MRI that can be metabolized and are not deposited in the brain.

Magnetic particle imaging for assessment of cerebral perfusion and ischemia

Stroke is one of the leading worldwide causes of death and sustained disability. Rapid and accurate assessment of cerebral perfusion is essential to diagnose and successfully treat stroke patients. Magnetic particle imaging (MPI) is a new technology with the potential to overcome some limitations of established imaging modalities. It is an innovative and radiation-free imaging technique with high sensitivity, specificity, and superior temporal resolution. MPI enables imaging and diagnosis of stroke and other neurological pathologies such as hemorrhage, tumors, and inflammatory processes. MPI scanners also offer the potential for targeted therapies of these diseases. Due to lower field requirements, MPI scanners can be designed as resistive magnets and employed as mobile devices for bedside imaging. With these advantages, MPI could accelerate and improve the diagnosis and treatment of neurological disorders. This review provides a basic introduction to MPI, discusses its current use for stroke imaging, and addresses future applications, including the potential for clinical implementation. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease.

Ferumoxytol-enhanced ultrashort TE MRA and quantitative morphometry of the human kidney vasculature

PURPOSE

To evaluate the feasibility of Quantitative Ultrashort-Time-to-Echo Contrast-Enhanced (QUTE-CE) MRA using ferumoxytol as a contrast agent for abdominal angiography in the kidney.

METHODS

Four subjects underwent ferumoxytol-enhanced MRA with the 3D UTE Spiral VIBE WIP sequence at 3 T. Image quality metrics were quantified, specifically the blood Signal-to-Noise Ratio (SNR), blood-tissue Contrast-to-Noise Ratio (CNR) and Intraluminal Signal Heterogeneity (ISH) from both the aorta and inferior vena cava (IVC). Morphometric analysis of the vessels was performed using manual approach and semi-automatic approach using Vascular Modeling ToolKit (VMTK). Image quality and branching order were compared between QUTE-CE MRA and the Gadolinium (Gd) CEMRA reference image.

RESULTS

QUTE-CE MRA provides a bright blood snapshot that delineates arteries and veins equally in the same scan. The maximum SNR and CNR values were 3,282 ± 1,218 and 1,295 ± 580, respectively - significantly higher than available literature values using other CEMRA techniques. QUTE-CE MRA had lower ISH and depicted higher vessel branching order (7th vs 3rd) within the kidney compared to a standard dynamic clinical Gd CEMRA scan. Morphometric analysis yielded quantitative results for the total kidney volume, total cyst volume and for diameters of the branching arterial network down to the 7^th branch. Vessel curvature was significantly increased (p < 0.001) in the presence of a renal cyst compared to equivalent vessels in normal kidney regions.

CONCLUSION

QUTE-CE MRA is feasible for kidney angiography, providing greater detail of kidney vasculature, enabling quantitative morphometric analysis of the abdominal and intra-renal vessels and yielding metrics relevant to vascular diseases while using a contrast agent ferumoxytol that is safe for CKD patients.

Intraoperative assessment and postsurgical treatment of prostate cancer tumors using tumor-targeted nanoprobes

Successful visualization of prostate cancer (PCa) tumor margins during surgery remains a major challenge. The visualization of these tumors during surgery via near infrared fluorescence (NIRF) imaging would greatly enhance surgical resection, minimizing tumor recurrence and improving outcome. Furthermore, chemotherapy is typically administered to patients after surgery to treat any missed tumor tissue around the surgical area, minimizing metastasis and increasing patient survival. For these reasons, a theranostics fluorescent nanoparticle could be developed to assist in the visualization of PCa tumor margins, while also delivering chemotherapeutic drug after surgery.

Methods: Ferumoxytol (FMX) conjugated to the fluorescent dye and PCa targeting agent, heptamethine carbocyanine (HMC), yielded the HMC-FMX nanoprobe that was tested in vitro with various PCa cell lines and in vivo with both subcutaneous and orthotopic PCa mouse models. Visualization of these tumors via NIRF imaging after administration of HMC-FMX was performed. In addition, delivery of chemotherapeutic drug and their effect on tumor growth was also assessed.

Results: HMC-FMX internalized into PCa cells, labeling these cells and PCa tumors in mice with near infrared fluorescence, facilitating tumor margin visualization. HMC-FMX was also able to deliver drugs to these tumors, reducing cell migration and slowing down tumor growth.

Conclusion: HMC-FMX specifically targeted PCa tumors in mice allowing for the visualization of tumor margins by NIRF imaging. Furthermore, delivery of anticancer drugs by HMC-FMX effectively reduced prostate tumor growth and reduced cell migration in vitro. Thus, HMC-FMX can potentially translate into the clinic as a nanotheranostics agent for the intraoperative visualization of PCa tumor margins, and post-operative treatment of tumors with HMC-FMX loaded with anticancer drugs.