Advances in Magnetic Resonance Imaging Contrast Agents for Biomarker Detection

Abstract

Recent advances in magnetic resonance imaging (MRI) contrast agents have provided new capabilities for biomarker detection through molecular imaging. MRI contrast agents based on the T2 exchange mechanism have more recently expanded the armamentarium of agents for molecular imaging. Compared with T1 and T2* agents, T2 exchange agents have a slower chemical exchange rate, which improves the ability to design these MRI contrast agents with greater specificity for detecting the intended biomarker. MRI contrast agents that are detected through chemical exchange saturation transfer (CEST) have even slower chemical exchange rates. Another emerging class of MRI contrast agents uses hyperpolarized 13C to detect the agent with outstanding sensitivity. These hyperpolarized 13C agents can be used to track metabolism and monitor characteristics of the tissue microenvironment. Together, these various MRI contrast agents provide excellent opportunities to develop molecular imaging for biomarker detection.

Modifying LnHPDO3A Chelates for Improved T1 and CEST MRI Applications

“…Contrast agents (CAs) are often used to increase the diagnostic information of the image by enhancing the signal intensity and the contrast between normal and diseased tissues. Although paramagnetic metal complexes (in particular of Gd III and Mn II ) and iron oxide nanoparticles (SPIO and USPIO) have been primarily used as contrast media in clinical settings, other classes of MRI CAs have been also introduced with the aim to widen the applicability of the diagnostic technique . In particular, 1 H MRI chemical exchange saturation transfer (CEST) agents, 19 F MRI probes, and hyperpolarized molecules containing heteronuclear resonances characterized by long spin–lattice relaxation time T 1 values are the MRI CAs most promising for a potential clinical translation .…”

“…Contrast agents( CAs) [1] are often used to increaset he diagnostic information of the image by enhancing the signal intensity and the contrastb etween normal and diseasedt issues.A lthoughp aramagnetic metal complexes (in particular of Gd III and Mn II ) [2] and iron oxide nanoparticles (SPIO and USPIO) [3] have been primarily used as contrast media in clinicals ettings, other classes of MRI CAs have been also introduced with the aim to widen the applicability of the diagnostic technique. [4] In particular, 1 HMRI chemical exchange saturation transfer (CEST) agents, 19 FMRI probes, and hyperpolarized molecules containing heteronuclear resonances characterized by long spin-lattice relaxation time T 1 values are the MRI CAs mostp romising for ap otential clinical translation. [5] Among these, CEST agents affect the intensity of the bulk water signal by transferring saturatedm agnetization from an exchangeable pool of protons, which are properly irradiated by ar adiofrequency field centered at their absorption frequency.T hey have the great advantage to be frequency-encoding systems, thus 1) there is no need to acquire ap re-contrast image, 2) it is possible to detect more agentsint he same image by selecting the propersaturation field, and 3) it is possible to assess parameters of pathological interest (pH, temperature, enzyme activity) by applying ar atiometrica pproach.…”

Effects of P‐gp and Bcrp as brain efflux transporters on the uptake of [18F]FPEB in the murine brain

“…Compared with PET, MRI is a nonirradiant imaging modality, which can provide high spatial resolution and excellent soft contrast tissue. However, the sensitivity is limited (micro-to millimolar), and the quantification of the absolute concentration of the contrast agent is challenging (Sinharay & Pagel, 2016;Tournier, Stieger, & Langer, 2018).…”

Hyperpolarized Porous Silicon Nanoparticles: Potential Theragnostic Material for 29Si Magnetic Resonance Imaging

“…Magnetic resonance imaging (MRI) is a powerful diagnostic tool for the noninvasive imaging of soft tissue in patients. As such, development of MRI contrast agents for targeted molecular imaging of various disease systems has increased in relevance in recent years . For example, silicon‐based nanoparticles have emerged as potential MRI contrast agents due to their biocompatibility in vivo, as well as for their flexible surface chemistry .…”

“…As such, development of MRI contrast agents for targeted molecular imaging of various disease systems has increased in relevance in recent years. [1] For example, silicon-based nanoparticles have emerged as potential MRI contrast agents due to their biocompatibility [2] in vivo, as well as for their flexible surface chemistry. [3] However, the practicality of 29 Si MR imaging and spectroscopy is somewhat limited due to the low gyromagnetic ratio (g~20 % of 1 H) and natural abundance of 29 Si nuclei (4 .7 %), which leads to insufficient sensitivity using traditional magnetic resonance methods.…”