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[...]the real problem is the potential harm associated with the procedure (See supplementary material). The main information we aimed to obtain concerned (1) the attitude towards the need for a dialysis session after the administration of a contrast agent, (2) the timing with respect to the contrast examination, (3) the duration of the dialysis session and the attitude towards residual diuresis. [See PDF for image] Fig. 1 a Distribution of responses regarding dedicated dialysis sessions after iodinated contrast agent administration. b Distribution of responses regarding dedicated dialysis sessions after gadolinium contrast agent administration Concerning dialysis patients undergoing magnetic resonance imaging (MRI), thirty-two (64%) centers administer a specific dialysis session after gadolinium exposure, as indicated in the ESUR guideline (Fig. 1b), and 29 of these, (90%) carry out hemodialysis as soon as possible after contrast agent infusion. Competing interests On behalf of all authors, the corresponding author states that there is no conflict of interest, no competing interest.

Medical imaging is routine in the diagnosis and staging of a wide range of medical conditions. In particular, magnetic resonance imaging (MRI) is critical for visualizing soft tissue and organs, with over 60 million MRI procedures performed each year worldwide. About one-third of these procedures are contrast-enhanced MRI, and gadolinium-based contrast agents (GBCAs) are the mainstream MRI contrast agents used in the clinic. GBCAs have shown efficacy and are safe to use with most patients; however, some GBCAs have a small risk of adverse effects, including nephrogenic systemic fibrosis (NSF), the untreatable condition recently linked to gadolinium (Gd) exposure during MRI with contrast. In addition, Gd deposition in the human brain has been reported following contrast, and this is now under investigation by the US Food and Drug Administration (FDA). To address a perceived need for a Gd-free contrast agent with pharmacokinetic and imaging properties comparable to GBCAs, we have designed and developed zwitterion-coated exceedingly small superparamagnetic iron oxide nanoparticles (ZES-SPIONs) consisting of ∼3-nm inorganic cores and ∼1-nm ultrathin hydrophilic shell. These ZES-SPIONs are free of Gd and show a high T₁ contrast power. We demonstrate the potential of ZES-SPIONs in preclinical MRI and magnetic resonance angiography.

Gadolinium-based contrast agents (GBCAs) have transformed magnetic resonance imaging (MRI) by facilitating the use of contrast-enhanced MRI to allow vital clinical diagnosis in a plethora of disease that would otherwise remain undetected. Although over 500 million doses have been administered worldwide, scientific research has documented the retention of gadolinium in tissues, long after exposure, and the discovery of a GBCA-associated disease termed nephrogenic systemic fibrosis, found in patients with impaired renal function. An understanding of the pharmacokinetics in humans and animals alike are pivotal to the understanding of the distribution and excretion of gadolinium and GBCAs, and ultimately their potential retention. This has been well studied in humans and more so in animals, and recently there has been a particular focus on potential toxicities associated with multiple GBCA administration. The purpose of this review is to highlight what is currently known in the literature regarding the pharmacokinetics of gadolinium in humans and animals, and any toxicity associated with GBCA use.

Magnetic resonance imaging (MRI) has revolutionized medical imaging diagnostics with the advantages of non-invasive nature, absence of ionizing radiation, unrestricted penetration depth, high-resolution imaging of soft tissues, organs and blood vessels, and multi-parameter and multi-sequence imaging. Contrast agents (CAs) are crucial for enhancing image quality, detecting molecular-level changes, and providing comprehensive diagnostic information in contrast enhanced MRI. However, the performance of clinical Gd-based CAs represents a limitation to the improvement of MRI sensitivity, specificity, and versatility, thereby impeding the achievement of satisfactory imaging outcomes. In recent years, the development of magnetic nanoparticle-based CAs has emerged as a promising avenue to enhance the capabilities of MRI. Here, we review the advances in magnetic nanoparticle-based MRI CAs, including blood pool CAs, biochemically-targeted CAs, stimulus-responsive CAs, and ultra-high field MRI CAs, as well as the use of CAs for cell labeling and tracking. Additionally, we offer insights into the future prospects and challenges associated with the integration of these nanoparticles into clinical practice.

Magnetic Resonance Imaging (MRI) is a powerful, noninvasive and nondestructive technique, capable of providing three-dimensional (3D) images of living organisms. The use of magnetic contrast agents has allowed clinical researchers and analysts to significantly increase the sensitivity and specificity of MRI, since these agents change the intrinsic properties of the tissues within a living organism, increasing the information present in the images. Advances in nanotechnology and materials science, as well as the research of new magnetic effects, have been the driving forces that are propelling forward the use of magnetic nanostructures as promising alternatives to commercial contrast agents used in MRI. This review discusses the principles associated with the use of contrast agents in MRI, as well as the most recent reports focused on nanostructured contrast agents. The potential applications of gadolinium- (Gd) and manganese- (Mn) based nanomaterials and iron oxide nanoparticles in this imaging technique are discussed as well, from their magnetic behavior to the commonly used materials and nanoarchitectures. Additionally, recent efforts to develop new types of contrast agents based on synthetic antiferromagnetic and high aspect ratio nanostructures are also addressed. Furthermore, the application of these materials in theragnosis, either as contrast agents and controlled drug release systems, contrast agents and thermal therapy materials or contrast agents and radiosensitizers, is also presented.

Computed tomography (CT), a diagnostic tool with clinical application, comprehensive coverage, and low cost, is used in hospitals worldwide. However, CT imaging fails to distinguish soft tissues from normal organs and tumors because their mass attenuation coefficients are similar. Various CT contrast agents have been developed in recent years to improve the sensitivity and contrast of imaging. Here, we review the progress of nanomaterial-based CT contrast agents and their applications in image-guided therapy. The CT contrast agents are classified according to their components; gold (Au)-based, bismuth (Bi)-based, lanthanide (Ln)-based, and transition metal (TM)-based nanomaterials are discussed. CT image-guided therapy of diseases, including photothermal therapy (PPT), photodynamic therapy (PDT), chemotherapy, radiotherapy (RT), gas therapy, sonodynamic therapy (SDT), immunotherapy, starvation therapy, gene therapy (GT), and microwave thermal therapy (MWTT), are reviewed. Finally, the perspectives on the CT contrast agents and their biomedical applications are discussed.

In medical domain, diseases in critical internal organs are generally inspected using invasive/non-invasive imaging techniques. Magnetic resonance imaging (MRI) is one of the commonly considered imaging approaches to confirm the abnormality in various internal organs. After recording the MRI, an appropriate image processing exercise is to be implemented to investigate and infer the severity of the disease and its location. This paper proposes a semi-automated tool to investigate the medical MRI captured with contrast improved T1 modality (T1C). This technique considers the integration of Bat algorithm (BA) and Tsallis based thresholding along with region growing (RG) segmentation. Proposed approach is tested on RGB/gray scale images of brain and breast MRI recorded along with a contrast agent. After mining the infected region, its texture features are extracted with Haralick function to assess the surface details of abnormal section. Performance of RG is confirmed against other segmentation methods, such as level set (LS), principal component analysis (PCA) and watershed. The clinical significance of the proposed technique is also validated using the brain images of BRATS recorded using T1C modality. The experiment outcome confirms that, the implemented procedure provides better values of Jaccard (87.41%), Dice (90.36%), sensitivity (98.27%), specificity (97.72%), accuracy (97.53%) and precision (95.85%) for the considered BRATS brain MRI.

Magnetic nanoparticles (MNPs), either paramagnetic or superparamagnetic depending on their composition and size, have been thoroughly studied as magnetic resonance imaging (MRI) contrast agents using in vitro and in vivo biomedical preclinical studies, while some are clinically used. Their magnetic properties responsible in some cases for high magnetization values, together with large surface area-to-volume ratios and the possibility of surface functionalization, have been used in MRI-based diagnostic and theranostics applications. MNPs are usually used as positive (T1) or negative (T2) MRI contrast agents, causing brightening or darkening of selected regions in MRI images, respectively. This review focusses on recent developments and optimization of MNPs containing Gd, Mn, Fe and other lanthanide ions which may function as dual-mode T1–T2 MRI contrast agents (DMCAs). They induce positive or negative contrast in the same MRI scanner upon changing its operational mode between T1-weighted and T2-weighted pulse sequences. The type of contrast they induce depends critically on their r2/r1 relaxivity ratio, which for DMCAs should be in the 2–10 range of values. After briefly discussing the basic principles of paramagnetic relaxation in MNPs, in this review, the basic strategies for the rational design of DMCAs are presented and typical examples are discussed, including in vivo preclinical applications: (1) the use of NPs with a single type of contrast material, Gd- or Mn-based NPs or superparamagnetic NPs with appropriate size and magnetization to provide T2 and T1 contrast; and (2) inclusion of both types of T1 and T2 contrast materials in the same nanoplatform by changing their relative positions.

This review article presents the state-of-the-art in the major imaging modalities supplying relevant information on patient health by real-time monitoring to establish an accurate diagnosis and potential treatment plan. We draw a comprehensive comparison between all imagers and ultimately end with our focus on two main types of scanners: X-ray CT and MRI scanners. Numerous types of imaging probes for both imaging techniques are described, as well as reviewing their strengths and limitations, thereby showing the current need for the development of new diagnostic contrast agents (CAs). The role of nanoparticles in the design of CAs is then extensively detailed, reviewed and discussed. We show how nanoparticulate agents should be promising alternatives to molecular ones and how they are already paving new routes in the field of nanomedicine.

Molecular imaging enables us to non-invasively visualize cellular functions and biological processes in living subjects, allowing accurate diagnosis of diseases at early stages. For successful molecular imaging, a suitable contrast agent with high sensitivity is required. To date, various nanoparticles have been developed as contrast agents for medical imaging modalities. In comparison with conventional probes, nanoparticles offer several advantages, including controllable physical properties, facile surface modification and long circulation time. In addition, they can be integrated with various combinations for multimodal imaging and therapy. In this opinion piece, we highlight recent advances and future perspectives of nanomaterials for molecular imaging. This article is part of the themed issue ‘Challenges for chemistry in molecular imaging’.