Investigation of the Characteristics of New, Uniform, Extremely Small Iron-Based Nanoparticles as T1 Contrast Agents for MRI

Abstract

Objective:The purpose of this study was to evaluate the magnetic resonance (MR) characteristics and applicability of new, uniform, extremely small iron-based nanoparticles (ESIONs) with 3-4-nm iron cores using contrast-enhanced magnetic resonance angiography (MRA). Materials and Methods: Seven types of ESIONs were used in phantom and animal experiments with 1.5T, 3T, and 4.7T scanners. The MR characteristics of the ESIONs were evaluated via phantom experiments. With the ESIONs selected by the phantom experiments, animal experiments were performed on eight rabbits. In the animal experiments, the in vivo kinetics and enhancement effect of the ESIONs were evaluated using half-diluted and non-diluted ESIONs. The between-group differences were assessed using a linear mixed model. A commercially available gadolinium-based contrast agent (GBCA) was used as a control. Results: All ESIONs showed a good T1 shortening effect and were applicable for MRA at 1.5T and 3T. The relaxivity ratio of the ESIONs increased with increasing magnetic field strength. In the animal experiments, the ESIONs showed peak signal intensity on the first-pass images and persistent vascular enhancement until 90 minutes. On the 1-week follow-up images, the ESIONs were nearly washed out from the vascular structures and organs. The peak signal intensity on the first-pass images showed no significant difference between the non-diluted ESIONs with 3-mm iron cores and GBCA (p = 1.000). On the 10-minutes post-contrast images, the non-diluted ESIONs showed a significantly higher signal intensity than did the GBCA (p < 0.001). Conclusion:In the phantom experiments, the ESIONs with 3-4-nm iron oxide cores showed a good T1 shortening effect at 1.5T and 3T. In the animal experiments, the ESIONs with 3-nm iron cores showed comparable enhancement on the first-pass images and superior enhancement effect on the delayed images compared to the commercially available GBCA at 3T.

Optimization of micelle-encapsulated extremely small sized iron oxide nanoparticles as a T1 contrast imaging agent: biodistribution and safety profile

“…Additionally, relaxivity tends to decrease with increasing magnetic field strength. Studies indicate that the change in r1 relaxivity of ESIONs from 1.5T to 3T is approximately a 10–30% decrease [ 38 ]. Therefore, it is anticipated that the r1 relaxivity of our encapsulated ESIONs might be around 2 to 3 mM − 1s − 1 at 3T.…”

Challenges and advances for glioma therapy based on inorganic nanoparticles

“…Among the nanomaterials used as magnetic sensitizers, IONPs have been extensively studied because of their high longitudinal and transverse relaxation values, superior imaging performance, and low cytotoxicity [ 111 ]. Numerous works have confirmed that iron oxide nanoparticles have promising applications as MRI T1/T2/T2∗ contrast agents [ [112] , [113] , [114] ]. IONPs can enhance the cellular internalization of tumor cells and active phagocytes to improve the visualization of intracranial tumors within healthy brain tissue and slow down the clearance of tumor sites [ 115 ] so as to better depict glioma boundaries [ 116 ].…”