Gadolinium-Based Contrast Agent Use, Their Safety, and Practice Evolution

Precipitation of gadolinium from magnetic resonance imaging contrast agents may be the Brass tacks of toxicity

The formation of gadolinium-rich nanoparticles in multiple tissues from intravenous magnetic resonance imaging contrast agents may be the initial step in rare earth metallosis. The mechanism of gadolinium-induced diseases is poorly understood, as is how these characteristic nanoparticles are formed. Gadolinium deposition has been observed with all magnetic resonance imaging contrast agent brands. Aside from endogenous metals and acidic conditions, little attention has been paid to the role of the biological milieu in the degradation of magnetic resonance imaging contrast agents into nanoparticles. Herein, we describe the decomposition of the commercial magnetic resonance imaging contrast agents Omniscan and Dotarem in the presence of oxalic acid, a well-known endogenous compound. Omniscan dechelated rapidly and preluded measurement by the means available, while Dotarem underwent a two-step decomposition process. The decomposition of both magnetic resonance imaging contrast agents by oxalic acid formed gadolinium oxalate (Gd2[C2O4]3, Gd2Ox3). Furthermore, both observed steps of the Dotarem reaction involved the associative addition of oxalic acid. Adding protein (bovine serum albumin) increased the rate of dechelation. Displacement reactions could occur at lysosomal pH. Through these studies, we have demonstrated that magnetic resonance imaging contrast agents can be dissociated by endogenous molecules, thus illustrating a metric by which gadolinium-based contrast agents (GBCAs) might be destabilized in vivo.

Evaluating the use of lanthanide containing dendrimers for solvent paramagnetic relaxation enhancement

Paramagnetic relaxation enhancement (PRE) is widely used in biomolecular NMR spectroscopy to obtain long-range distance and orientational information for intra- or intermolecular interactions. In contrast to conventional PRE measurements, which require tethering small molecules containing either a radical or paramagnetic ion to specific sites on the target protein, solvent PRE (sPRE) experiments utilize paramagnetic cosolutes to induce a delocalized PRE effect. Compounds developed as contrast agents in magnetic resonance imaging (MRI) applications typically consist of Gd chelated by a small molecule. Coordinating these Gd-containing small molecules to larger and inert scaffolds has been shown to increase the PRE-effect and produce more effective contrast agents in MRI. Inspired by their use as MRI contrast agent, in this work we evaluate the effectiveness of using a functionalized polyamidoamine (PAMAM) dendrimer for sPRE measurements. Using ubiquitin as a model system, we measured the sPRE effect from a generation 5 PAMAM dendrimer (G5-Gd) as a function of temperature and pH and compared to conventional relaxation agents. We also demonstrated the utility of G5-Gd in sPRE studies to monitor changes in the structures of two proteins as they bind their ligands. These studies highlight the attractive properties of these macromolecular relaxation agents in biomolecular sPRE.

Diagnostics of brain tumor in the early stage: current status and future perspectives

Early diagnosis of brain tumors is challenging due to their complexity and delicate structure. Conventional imaging techniques like MRI, CT, and PET are unable to provide detailed visualization of early-stage brain tumors. Early-stage detection of brain tumors is vital for enhancing patient outcomes and survival rates. So far, several scientists have dedicated their efforts to innovating advanced diagnostic probes to efficiently cross the BBB and selectively target brain tumors for optimal imaging. The integration of these techniques presents a viable pathway for non-invasive, accurate, and early-stage tumor identification. Herein, we provide a timely update on the various imaging probes and potential challenges for the diagnosis of early-stage brain tumors. Furthermore, this review highlights the significance of integrating advanced imaging probes for improving the early detection of brain tumors, ultimately enhancing treatment outcomes. Hopefully, this review will stimulate the interest of researchers to accelerate the development of new imaging probes and even their clinical translation for improving the early diagnosis of brain tumors.

Gadolinium-Based Contrast Agents (GBCAs) for MRI: A Benefit-Risk Balance Analysis from a Chemical, Biomedical, and Environmental Point of View

Gadolinium-based contrast agents (GBCAs) have revolutionized medical imaging, enhancing the accuracy and diagnostic value of magnetic resonance imaging (MRI). The increasing use of GBCAs has raised concerns about the release of gadolinium (Gd)(III) into the environment and potential risks for human health. Initially, multiple administrations of GBCAs were associated only with nephrogenic system fibrosis disease in individuals with impaired kidney function. Even if the Gd(III) retention in tissues has not yet been correlated with any specific disease, caution is required for the extensive use of GBCAs. The concerns related to the employment of GBCAs, due to the possible deposition and retention, should be extended also to healthy individuals without renal impairments. To ensure the well-being of patients, there is a need to develop even more stable and better-performing GBCAs, new MRI approaches requiring lower doses of GBCAs and, finally, innovative methods for recovering Gd(III) from both patients' urines and the environment. This can have strong advantages for human health and for environmental sustainability, also considering Gd(III) scarcity, being a rare earth element, and the shared guideline to reduce, as much as possible, the use of rare metals.

Gadolinium (Gd)-based nanostructures as dual-armoured materials for microbial therapy and cancer theranostics

Gadolinium (Gd) nanoparticles hold significant promise in medical theranostics due to their unique properties. This review outlines the synthesis, characterisation, and applications of Gd nanostructures in combating microbial threats and advancing cancer theragnostic strategies. Synthesis methods such as co-precipitation, microemulsion, and laser ablation are discussed, alongside TEM, SEM, and magnetic characterisation. The antimicrobial efficacy of Gd nanostructures, their potential in combination therapy, and promising anticancer mechanisms are explored. Biocompatibility, toxicity, and regulatory considerations are also evaluated. Challenges, future perspectives, and emerging trends in Gd nanostructure research are highlighted, emphasising their transformative potential in medical applications.

Iron(III)-Quercetin Complex: In Vivo Acute Toxicity and Biodistribution of Novel MRI Agent

Background

The iron(III)-quercetin complex, known as "IronQ", is an innovative MRI contrast agent composed of one Fe(III) ion and two quercetin molecules. IronQ is efficiently internalized by cells, enabling T1-weighted MRI tracking. It has demonstrated therapeutic benefits in reducing inflammation in an intracerebral hemorrhage (ICH) mouse model and offers a safer alternative to gadolinium-based agents by avoiding cytotoxicity and genotoxicity. These properties make IronQ a promising candidate for safe and effective MRI contrast enhancement.

Purpose

This study aims to further the development of IronQ as an MRI contrast agent by investigating its biodistribution, pharmacokinetics, and acute toxicity in a preclinical animal model.

Methods

The relaxivity of IronQ was measured in water and whole blood phantoms. Acute toxicity was evaluated in Sprague Dawley rats administered single intraperitoneal doses of IronQ (75, 150, and 225 µmol Fe/kg BW) over a 14-day period. Pharmacokinetic studies were performed at a dose of 150 µmol Fe/kg BW, with blood iron content analyzed using ICP-OES. For in vivo biodistribution, SD rats were administered an intravenous dose of IronQ (225 µmol Fe/kg BW), followed by MR imaging using a 1.5 T scanner and subsequent tissue-ICP analysis.

Results

The longitudinal relaxivity (r1) of IronQ was measured to be 2.17 mm⁻¹s⁻¹ in ultrapure water and 3.56 mm⁻¹s⁻¹ in whole blood. Acute toxicity studies showed no mortality, morbidity, or significant biochemical changes, with histopathology confirming no irreversible organ damage. Pharmacokinetics revealed peak blood iron content at 1.1 hours post-administration and clearance within 24 hours. MRI demonstrated enhanced T1 signal intensity, particularly in the liver and kidney.

Conclusion

These findings provide valuable insights into the safety, pharmacokinetics, and imaging efficacy of IronQ, highlighting its potential as a robust and biocompatible MRI contrast agent.

Research progress of nitroxide radical-based MRI contrast agents: from structure design to application

Magnetic resonance imaging (MRI) remains a cornerstone of diagnostic imaging, offering unparalleled insights into anatomical structures and pathological conditions. Gadolinium-based contrast agents have long been the standard in MRI enhancement, yet concerns over nephrogenic systemic fibrosis have spurred interest in metal-free alternatives. Nitroxide radical-based MRI contrast agents (NO-CAs) have emerged as promising candidates, leveraging their biocompatibility and imaging capabilities. This review summaries the latest advancements in NO-CAs, focusing on synthesis methodologies, influencing effects of structures of NO-CAs on relaxation efficiency and their applications across various clinical contexts. Comprehensive discussions encompass small molecular, polymeric, and nano-sized NO-CAs, detailing their unique properties and potential clinical utilities. Despite challenges, NO-CAs represent a dynamic area of research poised to revolutionize MRI diagnostics. This review serves as a critical resource for researchers and practitioners seeking to navigate the evolving landscape of MRI contrast agents.

Unenhanced magnetic resonance imaging for the evaluation of sonographically indeterminate ovarian and adnexal masses

Objective

To investigate the accuracy of magnetic resonance imaging (MRI) in classifying sonographically indeterminate ovarian and adnexal masses.

Materials and Methods

This was a retrospective cross-sectional study of the unenhanced pelvic MRI scans of 243 patients with a collective total of 336 adnexal and ovarian masses.

Results

Unenhanced MRI showed a sensitivity of 97.7%, a specificity of 86.4%, and an accuracy of 93.8%. The area under the ROC curve was 0.944 (95% CI: 0.913-0.974).

Conclusion

Our results show that an unenhanced MRI protocol can be used to classify adnexal masses, especially in clinical settings in which the intravenous administration of gadolinium-based contrast is not safe and should be avoided.

Composite Contrast Enhancement of Hydrogel-Based Implants for Photon-Counting Computed Tomography Studies

Hydrogels have a wide range of medical applications, including use within implantable systems. However, when used in implants, their visibility under conventional medical imaging techniques is limited, creating safety risks for patients. In the current work, we assessed the possibility of enhancing hydrogels using Ln-based contrasting agents to facilitate their visualization in photon-counting computed tomography (PCCT). The contrast enhancement of gelatin, polyacrylamide (PAM), and silicone shells of implants was assessed. A novel synthetic route for producing cross-linked nanosized Ln2O3 with polyacrylamide was proposed and discussed in detail. Several prototypes of silicone implants, including silicone shell and gelatin or PAM filling with different combinations of contrasting agents, were produced and assessed in phantom PCCT studies.

Application of rare earth elements in dual-modality molecular probes

The unique 4f subshell electronic structure of rare earth elements endows them with exceptional properties in electrical, magnetic, and optical domains. These properties include prolonged fluorescence lifetimes, large Stokes shifts, distinctive spectral bands, and strong resistance to photobleaching, making them ideal for the synthesis of molecular probes. Each imaging technique possesses unique advantages and specific applicabilities but also inherent limitations due to its operational principles. Dual-modality molecular probes effectively address these limitations, particularly in applications involving high-resolution Magnetic Resonance Imaging (MRI) such as MRI/OI, MRI/PET, MRI/CT, and MRI/US. This review summarizes the applications, advantages, challenges, and current research status of rare earth elements in these four dual imaging modalities, providing a theoretical basis for the future development and application of rare earth elements in the field of dual-modality molecular probes.

Contribution of Magnetic Resonance Imaging Studies to the Understanding of Cerebral Malaria Pathogenesis

Cerebral malaria (CM), the most lethal clinical syndrome of Plasmodium falciparum infection, mostly affects children under 5 in sub-Saharan Africa. CM is characterized by seizures and impaired consciousness that lead to death in 15-20% of cases if treated quickly, but it is completely fatal when untreated. Brain magnetic resonance imaging (MRI) is an invaluable source of information on the pathophysiology of brain damage, but, due to limited access to scanners in endemic regions, only until very recently have case reports of CM patients studied with advanced MRI methods been published. The murine model of experimental cerebral malaria (ECM) shares many common features with the human disease and has been extensively used to study the pathogenic mechanisms of the neurological syndrome. In vivo MRI studies on this model, the first of which was published in 2005, have contributed to a better understanding of brain lesion formation in CM and identified disease markers that were confirmed by MRI studies published from 2013 onwards in pediatric patients from endemic areas. In this review, we recapitulate the main findings and critically discuss the contributions of MRI studies in the ECM model to the understanding of human CM.

Method for detection of cerebral blood flow in neurointensive care using longitudinal arterial spin labeling MRI

Cerebral blood flow (CBF) is carefully monitored in the Neurointensive Care Unit (NICU) to prevent secondary brain insults in patients who have suffered subarachnoid hemorrhage. Including absolute MRI measurements of CBF in the NICU monitoring protocol could add valuable information and potentially improve patient outcomes. This is particularly feasible at Linköping University Hospital, which uniquely has an MRI scanner located in the NICU, enabling longitudinal CBF measurements while eliminating medical transportation risks. Arterial spin labeling is a subtraction-based MRI technique that can measure CBF globally in the brain without the use of contrast agents, and thus is suitable for repeated measurements over short time periods. Therefore, this work aims to develop and implement a methodological workflow for the acquisition, analysis, absolute quantification, and visualization of longitudinal arterial spin labeling MRI measurements acquired in the clinical NICU setting. At this initial stage, the workflow was implemented and tested using acquired test-retest data and longitudinal data from two healthy participants. Subsequently, the workflow was tested in clinical practice on an intubated and ventilated patient monitored in the NICU after suffering a subarachnoid hemorrhage. To ensure accurate day-to-day comparisons between the repeated measurements, the selection of processing and analysis methods aimed to obtain CBF maps in absolute units of ml/min/100g. These CBF maps were quantified using both the FMRIB Software Library and an openly available flow territory atlas. The test-retest data showed small variations (4.4 ml/min/100g between sessions), and the longitudinal measurement resulted in low CBF variability over 12 days. Despite the greater complexity of clinical data, the quantification and chosen visualization tools proved helpful in interpreting the results. In conclusion, this workflow including repeated MRI measurements could help detect changes in CBF between different measurement days and complement other conventional monitoring techniques in the NICU.

Diagnostic CT cystography with diluted gadolinium-based contrast: A viable alternative to an iodinated contrast-based cystogram

Patients with reported history of severe iodinated contrast reaction are not uncommon in daily practice. Iodinated contrast is most frequently administered intravenously (IV) for CT scans but is also used intraluminally during urologic procedures and postoperatively to assess for leaks. Providers often are unaware that patients with prior iodinated contrast allergy after IV administration are still at risk for a reaction during intraluminal administration. We present a case of a patient with history of iodinated severe contrast allergy, in which CT cystography using a gadolinium-based-contrast agent was safely performed as an alternative to iodinated-based-cystography to evaluate for a postoperative leak.

Optimizing pseudo-spiral sampling for abdominal DCE MRI using a digital anthropomorphic phantom

PURPOSE

For reliable DCE MRI parameter estimation, k-space undersampling is essential to meet resolution, coverage, and signal-to-noise requirements. Pseudo-spiral (PS) sampling achieves this by sampling k-space on a Cartesian grid following a spiral trajectory. The goal was to optimize PS k-space sampling patterns for abdomin al DCE MRI.

METHODS

The optimal PS k-space sampling pattern was determined using an anthropomorphic digital phantom. Contrast agent inflow was simulated in the liver, spleen, pancreas, and pancreatic ductal adenocarcinoma (PDAC). A total of 704 variable sampling and reconstruction approaches were created using three algorithms using different parametrizations to control sampling density, halfscan and compressed sensing regularization. The sampling patterns were evaluated based on image quality scores and the accuracy and precision of the DCE pharmacokinetic parameters. The best and worst strategies were assessed in vivo in five healthy volunteers without contrast agent administration. The best strategy was tested in a DCE scan of a PDAC patient.

RESULTS

The best PS reconstruction was found to be PS-diffuse based, with quadratic distribution of readouts on a spiral, without random shuffling, halfscan factor of 0.8, and total variation regularization of 0.05 in the spatial and temporal domains. The best scoring strategy showed sharper images with less prominent artifacts in healthy volunteers compared to the worst strategy. Our suggested DCE sampling strategy also showed high quality DCE images in the PDAC patient.

CONCLUSION

Using an anthropomorphic digital phantom, we identified an optimal PS sampling strategy for abdominal DCE MRI, and demonstrated feasibility in a PDAC patient.

Anthropogenic gadolinium contaminations in the marine environment and its ecological implications

Due to the widespread application in medicine and industry of anthropogenic gadolinium (Gdanth), the widespread of Gd anomaly in surface water has leading to disruption of the natural Gd geochemical cycle. However, challenges related to the identification and quantification of Gdanth, assessment of its impacts on marine ecosystems, and exploration of strategies for mitigating its adverse effects still exist. Meanwhile, as the major source of the Gdanth, the environmental geochemical behavior of Gd-based contrast agents (GBCAs), which are used in medical diagnostics in magnetic resonance imaging (MRI), are still poorly understood. In this review, we 1) analyzed Gd anomalies in samples from published literature worldwide, confirmed their prevalence (81.25% for sea and lake water, 72.73% for river water), 2) demonstrated that the third-order polynomial method is the preferred approach for the detection of Gdanth in surface seawater, 3) outlined the species and applications of Gdanth and its impacts on marine environment, 4) explored the process of GBCAs influx into the ocean and demonstrated the concentration of Gdanth in coral samples was mainly affected by terrestrial input GBCAs (63.75%) through Pearson correlation analysis and principle component analysis, 5) proposed effective management strategies for GBCAs at all stages from production to release into the ocean, 6) formulated an expectation for future research on marine Gdanth.

Deep Learning Virtual Contrast-Enhanced T1 Mapping for Contrast-Free Myocardial Extracellular Volume Assessment

BACKGROUND

The acquisition of contrast-enhanced T1 maps to calculate extracellular volume (ECV) requires contrast agent administration and is time consuming. This study investigates generative adversarial networks for contrast-free, virtual extracellular volume (vECV) by generating virtual contrast-enhanced T1 maps.

METHODS AND RESULTS

This retrospective study includes 2518 registered native and contrast-enhanced T1 maps from 1000 patients who underwent cardiovascular magnetic resonance at 1.5 Tesla. Recent hematocrit values of 123 patients (hold-out test) and 96 patients from a different institution (external evaluation) allowed for calculation of conventional ECV. A generative adversarial network was trained to generate virtual contrast-enhanced T1 maps from native T1 maps for vECV creation. Mean and SD of the difference per patient (ΔECV) were calculated and compared by permutation of the 2-sided t test with 10 000 resamples. For ECV and vECV, differences in area under the receiver operating characteristic curve (AUC) for discriminating hold-out test patients with normal cardiovascular magnetic resonance versus myocarditis or amyloidosis were tested with Delong's test. ECV and vECV showed a high agreement in patients with myocarditis (ΔECV: hold-out test, 2.0%±1.5%; external evaluation, 1.9%±1.7%) and normal cardiovascular magnetic resonance (ΔECV: hold-out test, 1.9%±1.4%; external evaluation, 1.5%±1.2%), but variations in amyloidosis were higher (ΔECV: hold-out test, 6.2%±6.0%; external evaluation, 15.5%±6.4%). In the hold-out test, ECV and vECV had a comparable AUC for the diagnosis of myocarditis (ECV AUC, 0.77 versus vECV AUC, 0.76; P=0.76) and amyloidosis (ECV AUC, 0.99 versus vECV AUC, 0.96; P=0.52).

CONCLUSIONS

Generation of vECV on the basis of native T1 maps is feasible. Multicenter training data are required to further enhance generalizability of vECV in amyloidosis.

The safety of magnetic resonance imaging contrast agents

Gadolinium-based contrast agents are increasingly used in clinical practice. While these pharmaceuticals are verified causal agents in nephrogenic systemic fibrosis, there is a growing body of literature supporting their role as causal agents in symptoms associated with gadolinium exposure after intravenous use and encephalopathy following intrathecal administration. Gadolinium-based contrast agents are multidentate organic ligands that strongly bind the metal ion to reduce the toxicity of the metal. The notion that cationic gadolinium dissociates from these chelates and causes the disease is prevalent among patients and providers. We hypothesize that non-ligand-bound (soluble) gadolinium will be exceedingly low in patients. Soluble, ionic gadolinium is not likely to be the initial step in mediating any disease. The Kidney Institute of New Mexico was the first to identify gadolinium-rich nanoparticles in skin and kidney tissues from magnetic resonance imaging contrast agents in rodents. In 2023, they found similar nanoparticles in the kidney cells of humans with normal renal function, likely from contrast agents. We suspect these nanoparticles are the mediators of chronic toxicity from magnetic resonance imaging contrast agents. This article explores associations between gadolinium contrast and adverse health outcomes supported by clinical reports and rodent models.

Near-cure in patients with Gadolinium deposition disease undergoing intravenous DTPA chelation

Purpose

To demonstrate and evaluate factors contributing to near-cures in patients with Gadolinium Deposition Disease (GDD) undergoing intravenous (IV) DTPA chelation.

Methods

Patients who had undergone or are currently undergoing DTPA chelation for GDD were included in this report based on their medical records that showed their perceived improvement was at least 80% back to normal. A survey was developed that included factors commonly reported by patients treated in one clinic to determine if these 'near-cured' (pre-MRI baseline health) individuals possessed certain factors and lacked others. The anonymized survey was emailed to these individuals by the principal treating physician, the only investigator not blinded to the subjects. This report describes clinical documentation of patient status and their underlying factors in individuals treated by the primary author, and no research was performed. The survey was sent to sixteen individuals; Fourteen patients completed it (10 females; 41.1 ± 11.2 y/o).

Results

The most common factor was the administration of ≤5 lifetime doses of a Gadolinium-Based Contrast Agents (GBCA) (12/14). Unconfounded agents triggering GDD were seen in nine subjects. Most subjects (12/14) initiated chelation in the first year after the causative GBCA, and most (11/14) underwent ≤10 chelations with DTPA. Good healthcare status prior to MRI was observed in 5 subjects. The majority (11/14) described their immune status as strong. Severe physical disability prior to chelation was seen in 1.

Conclusion

Subjects with GDD can experience near-cure with IV DTPA chelation. Factors surveyed that predict near-cure include the start of chelation in the first year, few GBCA administrations, and good health status before MRI with GBCA injection. Nonetheless, a few patients with predictors of less successful outcomes still experienced near-cure.

Role of advanced MRI sequences for thyroid lesions assessment. A narrative review

Despite not being the first imaging modality for thyroid gland assessment, Magnetic Resonance Imaging (MRI), thanks to its optimal tissue contrast and spatial resolution, has provided some advancements in detecting and characterizing thyroid abnormalities. Recent research has been focused on improving MRI sequences and employing advanced techniques for a more comprehensive understanding of thyroid pathology. Although not yet standard practice, advanced MRI sequences have shown high accuracy in preliminary studies, correlating well with histopathological results. They particularly show promise in determining malignancy risk in thyroid lesions, which may reduce the need for invasive procedures like biopsies. In this line, functional MRI sequences like Diffusion Weighted Imaging (DWI), Dynamic Contrast-Enhanced MRI (DCE-MRI), and Arterial Spin Labeling (ASL) have demonstrated their potential usefulness in evaluating both diffuse thyroid conditions and focal lesions. Multicompartmental DWI models, such as Intravoxel Incoherent Motion (IVIM) and Diffusion Kurtosis Imaging (DKI), and novel methods like Amide Proton Transfer (APT) imaging or artificial intelligence (AI)-based analyses are being explored for their potential valuable insights into thyroid diseases. This manuscript reviews the critical physical principles and technical requirements for optimal functional MRI sequences of the thyroid and assesses the clinical utility of each technique. It also considers future prospects in the context of advanced MR thyroid imaging and analyzes the current role of advanced MRI sequences in routine practice.

Complete Transposition of the Great Arteries in the Pediatric Field: A Multimodality Imaging Approach

The complete transposition of the great arteries (C-TGA) is a congenital cardiac anomaly characterized by the reversal of the main arteries. Early detection and precise management are crucial for optimal outcomes. This review emphasizes the integral role of multimodal imaging, including fetal echocardiography, transthoracic echocardiography (TTE), cardiovascular magnetic resonance (CMR), and cardiac computed tomography (CCT) in the diagnosis, treatment planning, and long-term follow-up of C-TGA. Fetal echocardiography plays a pivotal role in prenatal detection, enabling early intervention strategies. Despite technological advances, the detection rate varies, highlighting the need for improved screening protocols. TTE remains the cornerstone for initial diagnosis, surgical preparation, and postoperative evaluation, providing essential information on cardiac anatomy, ventricular function, and the presence of associated defects. CMR and CCT offer additional value in C-TGA assessment. CMR, free from ionizing radiation, provides detailed anatomical and functional insights from fetal life into adulthood, becoming increasingly important in evaluating complex cardiac structures and post-surgical outcomes. CCT, with its high-resolution imaging, is indispensable in delineating coronary anatomy and vascular structures, particularly when CMR is contraindicated or inconclusive. This review advocates for a comprehensive imaging approach, integrating TTE, CMR, and CCT to enhance diagnostic accuracy, guide therapeutic interventions, and monitor postoperative conditions in C-TGA patients. Such a multimodal strategy is vital for advancing patient care and improving long-term prognoses in this complex congenital heart disease.

Is non-contrast MRI sufficient to detect meningioma residue after surgery?

BACKGROUND

Contrast-enhanced magnetic resonance imaging (MRI) is the imaging modality routinely used to follow up patients who have undergone surgical resection of brain meningiomas. There are growing concerns about the massive use of gadolinium-based contrast agents (GBCA). Our aim was to evaluate the performance of a new imaging protocol, performed without GBCA injection, in the detection of tumoral residue or local recurrence after surgery of parafalcine and convexity meningiomas.

MATERIALS AND METHODS

Only adult patients with a documented resected parafalcine or convexity meningioma were included. We performed a dedicated MRI protocol that included non-contrast and post-contrast sequences. The presence or absence of residue on the unenhanced sequences was independently recorded by three observers: first blindly, then in comparison with a baseline enhanced MRI examination.

RESULTS

A total of 51 patients were included. 37 of them featured a tumor residue on the reference enhanced sequence. Overall, an average of 32 of 37 (87%) residues were identified on the unenhanced sequences that were blindly reviewed; and more than 34 of 37 (93%) were identified with the help of the comparative baseline enhanced examination, with a high sensitivity. The missed cases were related to small residues.

CONCLUSION

Unenhanced MRI sequences are highly sensitive and specific in identifying a tumor residue or a local recurrence in the post operative follow up of brain meningiomas. Sensitivity is even higher with the help of a comparative baseline enhanced MRI examination, whatever the strength of magnetic field.

Advances in MRI: Peptide and peptidomimetic-based contrast agents

Magnetic resonance imaging (MRI) is a common medical imaging technique that provides three-dimensional body images. MRI contrast agents improve image contrast by raising the rate of water proton relaxation in specific tissues. Peptides and peptidomimetics act as scaffolds for MRI imaging agents because of their increased size and offer the possibility to engine a higher hydration value within the design. The design of a new Gd-based contrast agent must take into account high stability constants to avoid free Gd(III), with the subsequent nephrotoxicity, and high relaxivity values. This review analyzes various synthetic approaches, reports studies of relaxometric parameters, and focuses on the description and application of Gd(III)-chelates based on peptide and peptidomimetic scaffolds. In addition, the X-ray molecular structures of three DOTA complexes will be reported to emphasize the necessity of using the X-ray diffraction analysis to identify the coordination sphere of the metals and the mechanism of action of the compounds.

Combined free-running four-dimensional anatomical and flow magnetic resonance imaging with native contrast using Synchronization of Neighboring Acquisitions by Physiological Signals

BACKGROUND

Four-dimensional (4D) flow magnetic resonance imaging (MRI) often relies on the injection of gadolinium- or iron-oxide-based contrast agents to improve vessel delineation. In this work, a novel technique is developed to acquire and reconstruct 4D flow data with excellent dynamic visualization of blood vessels but without the need for contrast injection. Synchronization of Neighboring Acquisitions by Physiological Signals (SyNAPS) uses pilot tone (PT) navigation to retrospectively synchronize the reconstruction of two free-running three-dimensional radial acquisitions, to create co-registered anatomy and flow images.

METHODS

Thirteen volunteers and two Marfan syndrome patients were scanned without contrast agent using one free-running fast interrupted steady-state (FISS) sequence and one free-running phase-contrast MRI (PC-MRI) sequence. PT signals spanning the two sequences were recorded for retrospective respiratory motion correction and cardiac binning. The magnitude and phase images reconstructed, respectively, from FISS and PC-MRI, were synchronized to create SyNAPS 4D flow datasets. Conventional two-dimensional (2D) flow data were acquired for reference in ascending (AAo) and descending aorta (DAo). The blood-to-myocardium contrast ratio, dynamic vessel area, net volume, and peak flow were used to compare SyNAPS 4D flow with Native 4D flow (without FISS information) and 2D flow. A score of 0-4 was given to each dataset by two blinded experts regarding the feasibility of performing vessel delineation.

RESULTS

Blood-to-myocardium contrast ratio for SyNAPS 4D flow magnitude images (1.5 ± 0.3) was significantly higher than for Native 4D flow (0.7 ± 0.1, p < 0.01) and was comparable to 2D flow (2.3 ± 0.9, p = 0.02). Image quality scores of SyNAPS 4D flow from the experts (M.P.: 1.9 ± 0.3, E.T.: 2.5 ± 0.5) were overall significantly higher than the scores from Native 4D flow (M.P.: 1.6 ± 0.6, p = 0.03, E.T.: 0.8 ± 0.4, p < 0.01) but still significantly lower than the scores from the reference 2D flow datasets (M.P.: 2.8 ± 0.4, p < 0.01, E.T.: 3.5 ± 0.7, p < 0.01). The Pearson correlation coefficient between the dynamic vessel area measured on SyNAPS 4D flow and that from 2D flow was 0.69 ± 0.24 for the AAo and 0.83 ± 0.10 for the DAo, whereas the Pearson correlation between Native 4D flow and 2D flow measurements was 0.12 ± 0.48 for the AAo and 0.08 ± 0.39 for the DAo. Linear correlations between SyNAPS 4D flow and 2D flow measurements of net volume (r2 = 0.83) and peak flow (r2 = 0.87) were larger than the correlations between Native 4D flow and 2D flow measurements of net volume (r2 = 0.79) and peak flow (r2 = 0.76).

CONCLUSION

The feasibility and utility of SyNAPS were demonstrated for joint whole-heart anatomical and flow MRI without requiring electrocardiography gating, respiratory navigators, or contrast agents. Using SyNAPS, a high-contrast anatomical imaging sequence can be used to improve 4D flow measurements that often suffer from poor delineation of vessel boundaries in the absence of contrast agents.

Preclinical Safety Assessment of Gadopiclenol: A High-Relaxivity Macrocyclic Gadolinium-Based MRI Contrast Agent

OBJECTIVE

Gadopiclenol is a new high-relaxivity macrocyclic gadolinium-based contrast agent for magnetic resonance imaging of the central nervous system and other body regions. The product has been approved by US Food and Drug Administration and is currently being evaluated by European Medicines Agency. For risk assessment of the single diagnostic use in humans, the safety profile of gadopiclenol was evaluated with a series of preclinical studies.

MATERIALS AND METHODS

With exception of dose-ranging studies, all safety pharmacology and toxicology studies were performed in compliance with Good Laboratory Practice principles. Safety pharmacology studies were conducted to assess potential effects on cardiovascular (in vitro and in dogs), respiratory (in rats and guinea pigs), neurological (in rats), and renal endpoints (in rats). Toxicology studies were also performed to investigate acute toxicity (in rats and mice), extended single-dose (in rats and dogs) and repeated-dose toxicity (in rats and dogs), reproductive (in rats), developmental (in rats and rabbits) and juvenile toxicity (in rats), as well as genotoxicity (in vitro and in rats), local tolerance (in rabbits), potential immediate hypersensitivity (in guinea pigs), and potential tissue retention of gadolinium (in rats).

RESULTS

Safety pharmacology studies conducted at high intravenous (IV) doses showed a satisfactory tolerance of gadopiclenol in the main body systems. After either single or repeated IV dosing (14 and 28 days) in rats and dogs, gadopiclenol was well tolerated even at high doses. The no-observed-adverse-effect level values (ie, the highest experimental dose without adverse effects) representing between 8 times in rats and 44 times in dogs (based on the exposure), the exposure achieved in humans at the intended diagnostic dose, provide a high safety margin. No or only minor and reversible effects on body weight, food consumption, clinical signs, clinical pathology parameters, or histology were observed at the highest doses. The main histological finding consists in renal tubular vacuolations (exacerbated after repeated exposure), which supports a well-known finding for this class of compounds that has no physiological consequence on kidney function. Reproductive toxicity studies showed no evidence of effects on reproductive performance, fertility, perinatal and postnatal development in rats, or reproductive development in rats or rabbits. The safety profile of gadopiclenol in juvenile rats was satisfactory like in adults. Gadopiclenol was not genotoxic in vitro in the Ames test, a mouse lymphoma assay, and a rat in vivo micronucleus test. There were no signs of local intolerance at the injection site after IV and intra-arterial administration in rabbits. However, because of minor signs of intolerance after perivenous administration, misadministration must be avoided. Gadopiclenol exhibited no signs of potential to induce immediate hypersensitivity in guinea pigs.

CONCLUSIONS

High safety margins were observed between the single diagnostic dose of 0.05 mmol/kg in humans and the doses showing effects in animal studies. Gadopiclenol is, therefore, well tolerated in various species (mice, rats, dogs, rabbits, and guinea pigs). All observed preclinical data support the clinical approval.

The Role of Multimodality Imaging in Patients with Congenital Heart Disease and Infective Endocarditis

Infective endocarditis (IE) represents an important medical challenge, particularly in patients with congenital heart diseases (CHD). Its early and accurate diagnosis is crucial for effective management to improve patient outcomes. Multimodality imaging is emerging as a powerful tool in the diagnosis and management of IE in CHD patients, offering a comprehensive and integrated approach that enhances diagnostic accuracy and guides therapeutic strategies. This review illustrates the utilities of each single multimodality imaging, including transthoracic and transoesophageal echocardiography, cardiac computed tomography (CCT), cardiovascular magnetic resonance imaging (CMR), and nuclear imaging modalities, in the diagnosis of IE in CHD patients. These imaging techniques provide crucial information about valvular and intracardiac structures, vegetation size and location, abscess formation, and associated complications, helping clinicians make timely and informed decisions. However, each one does have limitations that influence its applicability.

Safety of Magnetic Resonance Imaging in Pregnancy

Magnetic resonance imaging is being increasingly used to diagnose and follow up a variety of medical conditions in pregnancy, both for maternal and fetal indications. However, limited data regarding its safe use in pregnancy may be a source of anxiety and avoidance for both patients and their healthcare providers. In this review, we critically discuss the main safety concerns of Magnetic Resonance Imaging (MRI) in pregnancy including energy deposition, acoustic noise, and use of contrast agents, supported by data from animal and human studies. Use of maternal sedatives and concerns related to occupational exposure in pregnant personnel are also addressed. Exposure to gadolinium-based contrast agents and sedation for MRI during pregnancy should be avoided whenever feasible.

Multimodality Imaging Assessment of Tetralogy of Fallot: From Diagnosis to Long-Term Follow-Up

Tetralogy of Fallot (TOF) is the most common complex congenital heart disease with long-term survivors, demanding serial monitoring of the possible complications that can be encountered from the diagnosis to long-term follow-up. Cardiovascular imaging is key in the diagnosis and serial assessment of TOF patients, guiding patients' management and providing prognostic information. Thorough knowledge of the pathophysiology and expected sequalae in TOF, as well as the advantages and limitations of different non-invasive imaging modalities that can be used for diagnosis and follow-up, is the key to ensuring optimal management of patients with TOF. The aim of this manuscript is to provide a comprehensive overview of the role of each modality and common protocols used in clinical practice in the assessment of TOF patients.

Fe(III) T1 MRI Probes Containing Phenolate or Hydroxypyridine-Appended Triamine Chelates and a Coordination Site for Bound Water

Fe(III) complexes containing a triamine framework and phenolate or hydroxypyridine donors are characterized and studied as T1 MRI probes. In contrast to most Fe(III) MRI probes of linear chelates reported to date, the ligands reported here are pentadentate to give six-coordinate complexes with a coordination site for inner-sphere water. The crystal structure of the complex containing unsubstituted phenolate donors, Fe(L1)Cl, shows a six-coordinate iron center and contains a chloride ligand that is displaced in water. Two additional derivatives are sufficiently water-soluble for study as MRI probes, including a complex with a hydroxypyridine group, Fe(L2), and a hydroxybenzoic acid group, Fe(L3). The pH potentiometric titrations give protonation constants of 7.2 and 7.5 for Fe(L2) and Fe(L3), respectively, which are assigned to deprotonation of the bound water. Changes in the electronic absorbance spectra of the complexes as a function of pH are consistent with the deprotonation of phenol pendants at acidic pH values. However, the inner-sphere water ligand of Fe(L2) and Fe(L3) does not exchange rapidly on the NMR timescale at pH 6.0 or 7.4, as shown by variable-temperature 17O NMR spectroscopy. The pH-dependent proton relaxivity profiles show a maximum in relaxivity at a near-neutral pH, suggesting that exchange of the protons of the bound water is an important contribution. Competitive binding studies with ethylenediaminetetraacetic acid (EDTA) show effective stability constants for Fe(L2) and Fe(L3) at pH 7.4 with log K values of 21.1 and 20.5, respectively. These two complexes are kinetically inert in carbonate phosphate buffer at 37 °C for several hours but transfer iron to transferrin. Fe(L2) and Fe(L3) show enhanced contrast in T1-weighted imaging analyses in BALB/c mice. These studies show that Fe(L2) clears through mixed renal and hepatobiliary routes, while Fe(L3) has a similar pharmacokinetic clearance profile to a macrocyclic Gd(III) contrast agent.

Expression of GRP78 and its copartners in HEK293 and pancreatic cancer cell lines (BxPC-3/PANC-1) exposed to MRI and CT contrast agents

Endoplasmic reticulum (ER) stress-associated chaperones trigger a defense mechanism called as unfolded protein response (UPR) which can manage apoptosis and be determinative in cell fate. Both anticancer drug effects and potential toxicity effects of magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents were aimed to be evaluated. For this purpose, we investigated expression profiles of endoplasmic reticulum stress-associated chaperone molecules in human pancreatic tumor lines BxPC-3 and PANC-1 and control human embryonic kidney cells 293 (HEK293) induced with a variety of gadolinium and iohexol contrast agents. Protein expression levels of ER stress-associated chaperones (master regulator: GRP78/Bip and its copartners: Calnexin, Ero1, PDI, CHOP, IRE1α and PERK) were evaluated with Western blotting. Expression levels at mRNA level were also assessed for GRP78/Bip and CHOP with real-time PCR. Induction of cells was carried out with four different Gd-based contrast agents (GBCAs): (Dotarem, Optimark, Primovist and Gadovist) and two different iohexol agents (Omnipol, Omnipaque). CT contrast agents tested in the study did not result in significant ER stress in HEK293 cells. However, they do not seem to have theranostic potential in pancreas cancer through ER pathway. The potential efficiency of macrocyclic MRI contrast agents to provoke apoptosis via ER stress-associated chaperones in BxPC-3 cells lends credibility for their future theranostic use in pancreas cancer as long as undesired toxicity effects were carefully considered. ER stress markers and/or contrast agents seem to have promising potential to be translated into the clinical practice to manage pancreas cancer progression.

Exploring Gadolinium-Based Contrast Media for Retrograde Pyelography in the Context of Iodine Allergy

Iodinated contrast media can rarely cause severe allergic reactions during nonvascular urologic imaging procedures. Alternatives like gadolinium-based contrast may help mitigate this risk in susceptible patients. A 66-year-old woman with a documented iodine allergy presented with an obstructing stone in the right ureter. To avoid the risk of an allergic reaction, the decision was made to use an alternative non-iodinated contrast agent for retrograde pyelography prior to ureteral stent placement. Gadobenate dimeglumine, an MRI contrast agent, was diluted 50:50 with saline and utilized successfully to provide adequate opacification for safe stent placement without adverse reaction. The patient underwent repeat pyelography with gadobenate dimeglumine one month later during ureteroscopy without complication. This case demonstrates that diluted gadobenate can serve as an effective alternative to iodinated contrast media in patients at high risk of reaction to iodine-containing agents. While severe reactions to iodinated contrast are uncommon in nonvascular urologic procedures, they can still occur even with premedication. Gadolinium-based agents have been reported to provide sufficient opacification for most urologic interventions, though inferior radiographically to iodinated contrast. Further study on gadolinium efficacy and safety in this setting is warranted. However the present case supports gadobenate dimeglumine as a viable option for retrograde pyelography when allergy risk precludes iodinated contrast use.

The Role of Multimodality Imaging in Pediatric Cardiomyopathies

Cardiomyopathies are a heterogeneous group of myocardial diseases representing the first cause of heart transplantation in children. Diagnosing and classifying the different phenotypes can be challenging, particularly in this age group, where cardiomyopathies are often overlooked until the onset of severe symptoms. Cardiovascular imaging is crucial in the diagnostic pathway, from screening to classification and follow-up assessment. Several imaging modalities have been proven to be helpful in this field, with echocardiography undoubtedly representing the first imaging approach due to its low cost, lack of radiation, and wide availability. However, particularly in this clinical context, echocardiography may not be able to differentiate from cardiomyopathies with similar phenotypes and is often complemented with cardiovascular magnetic resonance. The latter allows a radiation-free differentiation between different phenotypes with unique myocardial tissue characterization, thus identifying the presence and extent of myocardial fibrosis. Nuclear imaging and computed tomography have a complementary role, although they are less used in daily clinical practice due to the concern related to the use of radiation in pediatric patients. However, these modalities may have some advantages in evaluating children with cardiomyopathies. This paper aims to review the strengths and limitations of each imaging modality in evaluating pediatric patients with suspected or known cardiomyopathies.

Magnetic Resonance Imaging in Clinical Trials of Diabetic Kidney Disease

Chronic kidney disease (CKD) associated with diabetes mellitus (DM) (known as diabetic kidney disease, DKD) is a serious and growing healthcare problem worldwide. In DM patients, DKD is generally diagnosed based on the presence of albuminuria and a reduced glomerular filtration rate. Diagnosis rarely includes an invasive kidney biopsy, although DKD has some characteristic histological features, and kidney fibrosis and nephron loss cause disease progression that eventually ends in kidney failure. Alternative sensitive and reliable non-invasive biomarkers are needed for DKD (and CKD in general) to improve timely diagnosis and aid disease monitoring without the need for a kidney biopsy. Such biomarkers may also serve as endpoints in clinical trials of new treatments. Non-invasive magnetic resonance imaging (MRI), particularly multiparametric MRI, may achieve these goals. In this article, we review emerging data on MRI techniques and their scientific, clinical, and economic value in DKD/CKD for diagnosis, assessment of disease pathogenesis and progression, and as potential biomarkers for clinical trial use that may also increase our understanding of the efficacy and mode(s) of action of potential DKD therapeutic interventions. We also consider how multi-site MRI studies are conducted and the challenges that should be addressed to increase wider application of MRI in DKD.

Fatal Allergic Reaction to Gadolinium Contrast

Gadolinium-based contrast agents (GBCA) have been used to enhance the sensitivity and specificity of disease diagnoses. They have excellent safety profiles. However, rare adverse events may happen. We present a case of severe fatal allergic reaction to GBCA in a 35-year-old patient.

Fluid-Attenuated Inversion Recovery Sequence with Fat Suppression for Assessment of Ankle Synovitis without Contrast Enhancement: Comparison with Contrast-Enhanced MRI

The purpose of this study was to investigate the feasibility of the fluid-attenuated inversion recovery sequence with fat suppression (FLAIR-FS) for the assessment of ankle synovitis without contrast enhancement. FLAIR-FS and contrast-enhanced, T1-weighted sequences (CE-T1) of 94 ankles were retrospectively reviewed by two radiologists. Grading of synovial visibility (four-point scale) and semi-quantitative scoring of synovial thickness (three-point scale) were performed in four compartments of the ankle in both sequences. Synovial visibility and thickness in FLAIR-FS and CE-T1 images were compared, and agreement between both sequences was assessed. Synovial visibility grades and synovial thickness scores for FLAIR-FS images were lower than those for CE-T1 images (reader 1, p = 0.016, p < 0.001; reader 2, p = 0.009, p < 0.001). Dichotomized synovial visibility grades (partial vs. full visibility) were not significantly different between both sequences. The agreement in synovial thickness scores between the FLAIR-FS and CE-T1 images was moderate to substantial (κ = 0.41-0.65). The interobserver agreement between the two readers was fair for synovial visibility (κ = 0.27-0.32) and moderate to substantial for synovial thickness (κ = 0.54-0.74). In conclusion, FLAIR-FS is a feasible MRI sequence for the evaluation of ankle synovitis without contrast enhancement.

Contrast Agent Dose Reduction in MRI Utilizing a Generative Adversarial Network in an Exploratory Animal Study

OBJECTIVES

The aim of this study is to use virtual contrast enhancement to reduce the amount of hepatobiliary gadolinium-based contrast agent in magnetic resonance imaging with generative adversarial networks (GANs) in a large animal model.

METHODS

With 20 healthy Göttingen minipigs, a total of 120 magnetic resonance imaging examinations were performed on 6 different occasions, 50% with reduced (low-dose; 0.005 mmol/kg, gadoxetate) and 50% standard dose (normal-dose; 0.025 mmol/kg). These included arterial, portal venous, venous, and hepatobiliary contrast phases (20 minutes, 30 minutes). Because of incomplete examinations, one animal had to be excluded. Randomly, 3 of 19 animals were selected and withheld for validation (18 examinations). Subsequently, a GAN was trained for image-to-image conversion from low-dose to normal-dose (virtual normal-dose) with the remaining 16 animals (96 examinations). For validation, vascular and parenchymal contrast-to-noise ratio (CNR) was calculated using region of interest measurements of the abdominal aorta, inferior vena cava, portal vein, hepatic parenchyma, and autochthonous back muscles. In parallel, a visual Turing test was performed by presenting the normal-dose and virtual normal-dose data to 3 consultant radiologists, blinded for the type of examination. They had to decide whether they would consider both data sets as consistent in findings and which images were from the normal-dose study.

RESULTS

The pooled dynamic phase vascular and parenchymal CNR increased significantly from low-dose to virtual normal-dose (pooled vascular: P < 0.0001, pooled parenchymal: P = 0.0002) and was found to be not significantly different between virtual normal-dose and normal-dose examinations (vascular CNR [mean ± SD]: low-dose 17.6 ± 6.0, virtual normal-dose 41.8 ± 9.7, and normal-dose 48.4 ± 12.2; parenchymal CNR [mean ± SD]: low-dose 20.2 ± 5.9, virtual normal-dose 28.3 ± 6.9, and normal-dose 29.5 ± 7.2). The pooled parenchymal CNR of the hepatobiliary contrast phases revealed a significant increase from the low-dose (22.8 ± 6.2) to the virtual normal-dose (33.2 ± 6.1; P < 0.0001) and normal-dose sequence (37.0 ± 9.1; P < 0.0001). In addition, there was no significant difference between the virtual normal-dose and normal-dose sequence. In the visual Turing test, on the median, the consultant radiologist reported that the sequences of the normal-dose and virtual normal-dose are consistent in findings in 100% of the examinations. Moreover, the consultants were able to identify the normal-dose series as such in a median 54.5% of the cases.

CONCLUSIONS

In this feasibility study in healthy Göttingen minipigs, it could be shown that GAN-based virtual contrast enhancement can be used to recreate the image impression of normal-dose imaging in terms of CNR and subjective image similarity in both dynamic and hepatobiliary contrast phases from low-dose data with an 80% reduction in gadolinium-based contrast agent dose. Before clinical implementation, further studies with pathologies are needed to validate whether pathologies are correctly represented by the network.

Imaging in metastatic breast cancer, CT, PET/CT, MRI, WB-DWI, CCA: review and new perspectives

BACKGROUND

Breast cancer is the most frequent cancer in women and remains the second leading cause of death in Western countries. It represents a heterogeneous group of diseases with diverse tumoral behaviour, treatment responsiveness and prognosis. While major progress in diagnosis and treatment has resulted in a decline in breast cancer-related mortality, some patients will relapse and prognosis in this cohort of patients remains poor. Treatment is determined according to tumor subtype; primarily hormone receptor status and HER2 expression. Menopausal status and site of disease relapse are also important considerations in treatment protocols.

MAIN BODY

Staging and repeated evaluation of patients with metastatic breast cancer are central to the accurate assessment of disease extent at diagnosis and during treatment; guiding ongoing clinical management. Advances have been made in the diagnostic and therapeutic fields, particularly with new targeted therapies. In parallel, oncological imaging has evolved exponentially with the development of functional and anatomical imaging techniques. Consistent, reproducible and validated methods of assessing response to therapy is critical in effectively managing patients with metastatic breast cancer.

CONCLUSION

Major progress has been made in oncological imaging over the last few decades. Accurate disease assessment at diagnosis and during treatment is important in the management of metastatic breast cancer. CT (and BS if appropriate) is generally widely available, relatively cheap and sufficient in many cases. However, several additional imaging modalities are emerging and can be used as adjuncts, particularly in pregnancy or other diagnostically challenging cases. Nevertheless, no single imaging technique is without limitation. The authors have evaluated the vast array of imaging techniques - individual, combined parametric and multimodal - that are available or that are emerging in the management of metastatic breast cancer. This includes WB DW-MRI, CCA, novel PET breast cancer-epitope specific radiotracers and radiogenomics.

Cardiovascular Magnetic Resonance from Fetal to Adult Life-Indications and Challenges: A State-of-the-Art Review

Cardiovascular magnetic resonance (CMR) imaging offers a comprehensive, non-invasive, and radiation-free imaging modality, which provides a highly accurate and reproducible assessment of cardiac morphology and functions across a wide spectrum of cardiac conditions spanning from fetal to adult life. It minimises risks to the patient, particularly the risks associated with exposure to ionising radiation and the risk of complications from more invasive haemodynamic assessments. CMR utilises high spatial resolution and provides a detailed assessment of intracardiac and extracardiac anatomy, ventricular and valvular function, and flow haemodynamic and tissue characterisation, which aid in the diagnosis, and, hence, with the management of patients with cardiac disease. This article aims to discuss the role of CMR and the indications for its use throughout the different stages of life, from fetal to adult life.

New Contrast Enhancement Method for Multiple Sclerosis Lesion Detection

Multiple sclerosis (MS) is one of the most serious neurological diseases. It is the most frequent reason of non-traumatic disability among young adults. MS is an autoimmune disease wherein the central nervous system wrongly destructs the myelin sheath surrounding and protecting axons of nerve cells of the brain and the spinal cord which results in presence of lesions called plaques. The damage of myelin sheath alters the normal transmission of nerve flow at the plaques level, consequently, a loss of communication between the brain and other organs. The consequence of this poor transmission of nerve impulses is the occurrence of various neurological symptoms. MS lesions cause mobility, vision, cognitive, and memory disorders. Indeed, early detection of lesions provides an accurate MS diagnosis. Consequently, and with the adequate treatment, clinicians will be able to deal effectively with the disease and reduce the number of relapses. Therefore, the use of magnetic resonance imaging (MRI) is primordial which is proven as the relevant imaging tool for early diagnosis of MS patients. But, low contrast MRI images can hide important objects in the image such lesions. In this paper, we propose a new automated contrast enhancement (CE) method to ameliorate the low contrast of MRI images for a better enhancement of MS lesions. This step is very important as it helps radiologists in confirming their diagnosis. The developed algorithm called BDS is based on Brightness Preserving Dynamic Fuzzy Histogram Equalization (BPDFHE) and Singular Value Decomposition with Discrete Wavelet Transform (SVD-DWT) techniques. BDS is dedicated to improve the low quality of MRI images with preservation of the brightness level and the edge details from degradation and without added artifacts or noise. These features are essential in CE approaches for a better lesion recognition. A modified version of BDS called MBDS is also implemented in the second part of this paper wherein we have proposed a new method for computing the correction factor. Indeed, with the use of the new correction factor, the entropy has been increased and the contrast is greatly enhanced. MBDS is specially dedicated for very low contrast MRI images. The experimental results proved the effectiveness of developed methods in improving low contrast of MRI images with preservation of brightness level and edge information. Moreover, performances of both proposed BDS and MBDS algorithms exceeded conventional CE methods.

Magnetic particle based MRI thermometry at 0.2 T and 3 T

This study provides insight into the advantages and disadvantages of using ferrite particles embedded in agar gel phantoms as MRI temperature indicators for low-magnetic field scanners. We compare the temperature-dependent intensity of MR images at low-field (0.2 T) to those at high-field (3.0 T). Due to a shorter T₁ relaxation time at low-fields, MRI scanners operating at 0.2 T can use shorter repetition times and achieve a significant T₂^⁎ weighting, resulting in strong temperature-dependent changes of MR image brightness in short acquisition times. Although the signal-to-noise ratio for MR images at 0.2 T MR is much lower than at 3.0 T, it is sufficient to achieve a temperature measurement uncertainty of about ±1.0 °C at 37 °C for a 90 μg/mL concentration of magnetic particles.

Polymeric Metal Contrast Agents for T1-Weighted Magnetic Resonance Imaging of the Brain

Imaging plays an integral role in diagnostics and treatment monitoring for conditions affecting the brain; enhanced brain imaging capabilities will improve upon both while increasing the general understanding of how the brain works. T₁-weighted magnetic resonance imaging is the preferred modality for brain imaging. Commercially available contrast agents, which are often required to render readable brain images, have considerable toxicity concerns. In recent years, much progress has been made in developing new contrast agents based on the magnetic features of gadolinium, iron, or magnesium. Nanotechnological approaches for these systems allow for the protected integration of potentially harmful metals with added benefits like reduced dosage and improved transport. Polymeric enhancement of each design further improves biocompatibility while allowing for specific brain targeting. This review outlines research on polymeric nanomedicine designs for T₁-weighted contrast agents that have been evaluated for performance in the brain.

Cardiac Magnetic Resonance Fingerprinting: Potential Clinical Applications

PURPOSE OF REVIEW

Cardiac magnetic resonance fingerprinting (cMRF) has developed as a technique for rapid, multi-parametric tissue property mapping that has potential to both improve cardiac MRI exam efficiency and expand the information captured. In this review, we describe the cMRF technique, summarize technical developments and in vivo reports, and highlight potential clinical applications.

RECENT FINDINGS

Technical developments in cMRF continue to progress rapidly, including motion compensated reconstruction, additional tissue property quantification, signal time course analysis, and synthetic LGE image generation. Such technical developments can enable simplified CMR protocols by combining multiple evaluations into a single protocol and reducing the number of breath-held scans. cMRF continues to be reported for use in a range of pathologies; however barriers to clinical implementation remain. Technical developments are described in this review, followed by a focus on potential clinical applications that they may support. Clinical translation of cMRF could shorten protocols, improve CMR accessibility, and provide additional information as compared to conventional cardiac parametric mapping methods. Current needs for clinical implementation are discussed, as well as how those needs may be met in order to bring cMRF from its current research setting to become a viable tool for patient care.

The onset of rare earth metallosis begins with renal gadolinium-rich nanoparticles from magnetic resonance imaging contrast agent exposure

The leitmotifs of magnetic resonance imaging (MRI) contrast agent-induced complications range from acute kidney injury, symptoms associated with gadolinium exposure (SAGE)/gadolinium deposition disease, potentially fatal gadolinium encephalopathy, and irreversible systemic fibrosis. Gadolinium is the active ingredient of these contrast agents, a non-physiologic lanthanide metal. The mechanisms of MRI contrast agent-induced diseases are unknown. Mice were treated with a MRI contrast agent. Human kidney tissues from contrast-naïve and MRI contrast agent-treated patients were obtained and analyzed. Kidneys (human and mouse) were assessed with transmission electron microscopy and scanning transmission electron microscopy with X-ray energy-dispersive spectroscopy. MRI contrast agent treatment resulted in unilamellar vesicles and mitochondriopathy in renal epithelium. Electron-dense intracellular precipitates and the outer rim of lipid droplets were rich in gadolinium and phosphorus. We conclude that MRI contrast agents are not physiologically inert. The long-term safety of these synthetic metal-ligand complexes, especially with repeated use, should be studied further.

The Use of Stress Cardiovascular Imaging in Pediatric Population

Although not frequent in the pediatric population, ischemia could occur in children due to several congenital and acquired disease. Stress imaging is key for the non-invasive evaluation of myocardial abnormalities and perfusion defect in this clinical setting. Moreover, beyond ischemia assessment, it can provide complementary diagnostic and prognostic information in valvular heart disease and cardiomyopathies. When performed using cardiovascular magnetic resonance, it could detect, in addition, myocardial fibrosis and infarction, increasing the diagnostic yield. Several imaging modalities are currently available for the evaluation of stress myocardial perfusion. Advances in technologies have also increased the feasibility, safety and availability of these modalities in the pediatric age group. However, despite the established role of stress imaging and its increasing use in daily clinical practice, there are currently no specific guidelines, and little data are available in the literature on this topic. The aim of this review is to summarize the most recent evidence on pediatric stress imaging and its clinical application with a focus on the advantages and limitations of each imaging modality currently available.

Heavily Gd-Doped Non-Toxic Cerium Oxide Nanoparticles for MRI Labelling of Stem Cells

Recently, human mesenchymal stem cells (hMSc) have attracted a great deal of attention as potential therapeutic agents in the treatment of socially significant diseases. Despite substantial advances in stem-cell therapy, the biological mechanisms of hMSc action after transplantation remain unclear. The use of magnetic resonance imaging (MRI) as a non-invasive method for tracking stem cells in the body is very important for analysing their distribution in tissues and organs, as well as for ensuring control of their lifetime after injection. Herein, detailed experimental data are reported on the biocompatibility towards hMSc of heavily gadolinium-doped cerium oxide nanoparticles (Ce_0.8Gd_0.2O_2-x) synthesised using two synthetic protocols. The relaxivity of the nanoparticles was measured in a magnetic field range from 1 mT to 16.4 T. The relaxivity values (r₁ = 11 ± 1.2 mM^-1 s^-1 and r₁ = 7 ± 1.2 mM^-1 s^-1 in magnetic fields typical of 1.5 and 3 T MRI scanners, respectively) are considerably higher than those of the commercial Omniscan MRI contrast agent. The low toxicity of gadolinium-doped ceria nanoparticles to hMSc enables their use as an effective theranostic tool with improved MRI-contrasting properties.

Superparamagnetic Iron Oxide Nanoparticles (SPION): From Fundamentals to State-of-the-Art Innovative Applications for Cancer Therapy

Despite significant advances in cancer therapy over the years, its complex pathological process still represents a major health challenge when seeking effective treatment and improved healthcare. With the advent of nanotechnologies, nanomedicine-based cancer therapy has been widely explored as a promising technology able to handle the requirements of the clinical sector. Superparamagnetic iron oxide nanoparticles (SPION) have been at the forefront of nanotechnology development since the mid-1990s, thanks to their former role as contrast agents for magnetic resonance imaging. Though their use as MRI probes has been discontinued due to an unfavorable cost/benefit ratio, several innovative applications as therapeutic tools have prompted a renewal of interest. The unique characteristics of SPION, i.e., their magnetic properties enabling specific response when submitted to high frequency (magnetic hyperthermia) or low frequency (magneto-mechanical therapy) alternating magnetic field, and their ability to generate reactive oxygen species (either intrinsically or when activated using various stimuli), make them particularly adapted for cancer therapy. This review provides a comprehensive description of the fundamental aspects of SPION formulation and highlights various recent approaches regarding in vivo applications in the field of cancer therapy.

PI3K-AKT-Targeting Breast Cancer Treatments: Natural Products and Synthetic Compounds

Breast cancer is the most commonly diagnosed cancer in women. The high incidence of breast cancer, which is continuing to rise, makes treatment a significant challenge. The PI3K-AKT pathway and its downstream targets influence various cellular processes. In recent years, mounting evidence has shown that natural products and synthetic drugs targeting PI3K-AKT signaling have the potential to treat breast cancer. In this review, we discuss the role of the PI3K-AKT signaling pathway in the occurrence and development of breast cancer and highlight PI3K-AKT-targeting natural products and drugs in clinical trials for the treatment of breast cancer.

Aerosolised micro and nanoparticle: formulation and delivery method for lung imaging

Purpose

The application of contrast and tracing agents is essential for lung imaging, as indicated by the wide use in recent decades and the discovery of various new contrast and tracing agents. Different aerosol production and pulmonary administration methods have been developed to improve lung imaging quality. This review details and discusses the ideal characteristics of aerosol administered via pulmonary delivery for lung imaging and the methods for the production and pulmonary administration of dry or liquid aerosol.

Methods

We explored several databases, including PubMed, Scopus, and Google Scholar, while preparing this review to discover and obtain the abstracts, reports, review articles, and research papers related to aerosol delivery for lung imaging and the formulation and pulmonary delivery method of dry and liquid aerosol. The search terms used were "dry aerosol delivery", "liquid aerosol delivery", "MRI for lung imaging", "CT scan for lung imaging", "SPECT for lung imaging", "PET for lung imaging", "magnetic particle imaging", "dry powder inhalation", "nebuliser", and "pressurised metered-dose inhaler".

Results

Through the literature review, we found that the critical considerations in aerosol delivery for lung imaging are appropriate lung deposition of inhaled aerosol and avoiding toxicity. The important tracing agent was also found to be Technetium-99m (^99mTc), Gallium-68 (⁶⁸Ga) and superparamagnetic iron oxide nanoparticle (SPION), while the essential contrast agents are gold, iodine, silver gadolinium, iron and manganese-based particles. The pulmonary delivery of such tracing and contrast agents can be performed using dry formulation (graphite ablation, spark ignition and spray dried powder) and liquid aerosol (nebulisation, pressurised metered-dose inhalation and air spray).

Conclusion

A dual-imaging modality with the combination of different tracing or contrast agents is a future development of aerosolised micro and nanoparticles for lung imaging to improve diagnosis success.

Graphical abstract

Microvascular morphology alteration using relaxation rate change with gadolinium-based magnetic resonance imaging contrast agent in patients with Alzheimer's disease

Background

Conventional magnetic resonance imaging (MRI) techniques cannot demonstrate microvascular alterations in mild Alzheimer's disease (AD). Thus, the diagnosis of microvascular pathology commonly relies on postmortem. The purpose of this study was to evaluate alterations of microvascular structures in patients with AD using a 3T clinical MRI system with a commercially available contrast agent.

Methods

Eleven patients with AD and 11 cognitively normal (CN) controls were included in this cross-sectional prospective study. R2 and R2* relaxation rate changes (∆R2 and ∆R2*) before and after a Gadolinium (Gd)-based contrast agent injection were calculated from images obtained with a multi-echo turbo spin-echo sequence and multi-echo gradient-echo sequence to obtain microvascular index maps of blood volume fraction (BVf), mean vessel diameter (mVD), vessel size index (VSI), mean vessel density (Q), and microvessel-weighted imaging (MvWI). Two-sample t-test was used to compare those values between the two groups. Correlation analysis was performed to evaluate the relationship between those values and age.

Results

BVfs at the corpus callosum and at the thalamus were significantly increased in the AD group (P=0.024 and P=0.005, respectively). BVf at the gray matter (P=0.020) and white matter area (P=0.012) were also significantly increased in the AD group compared with the CN group. MvWIs at the hippocampus and parahippocampal gyrus were significantly increased in the AD group compared with the CN group (P=0.020 and P=0.006, respectively). Voxel-based analysis showed both mVD and VSI were significantly decreased at the prefrontal lobe in the AD group. Q were not significant difference between CN and AD groups. MvWI were significantly positively correlated with age.

Conclusions

Microvascular index was a useful non-invasive method to evaluate microvascular morphology alteration. The microvascular morphology of AD was manifested as increasing BVf and microvessel-weighted.