Magnetic Resonance Imaging (MRI) Contrast Agents for Tumor Diagnosis

Abstract

This review focuses on MRI contrast agents for tumor diagnosis. Several types of low molecular weight Gd3+-based complexes and dextran-coated superparamagnetic iron oxide (SPIO) nanoparticles have been used for clinical tumor diagnosis as longitudinal relaxation time (T1) and transverse relaxation time (T2) MRI contrast agents, respectively. To further improve the sensitivity of MRI, new types of chelates for T1 MRI contrast agents and combination of low molecular weight T1 MRI contrast agents with different types of carriers have been investigated. Different types of materials for forming secure coating layers of SPIO and novel superparamagnetic particles with higher relaxivity values have been explored. Various types of ligands were applied to improve the capability to target tumor for both T1 and T2 contrast agents. Furthermore, MRI contrast agents for detection of tumor metabolism were also pursued.

Targeting and in vivo imaging of non-small–cell lung cancer using nebulized multimodal contrast agents

“…These peculiar properties of tumor tissue are known to facilitate passive targeting and accumulation of diagnostic or therapeutic nanoparticles in tumors. As a matter of fact, tumor signal enhancement using gadolinium-based contrast agents is a common approach in clinical and preclinical MRI for improving the detection and the delineation of cancerous tissue (20,23,32). However, contrast enhancement of tumors located in the lung can be severely hampered by motion artifacts and unmatched magnetic susceptibility between air and tissues (6,7,(10)(11)(12).…”

Low SAR 31P (multi‐echo) spectroscopic imaging using an integrated whole‐body transmit coil at 7T

“…However, MRI focuses on morphological changes whilst metabolic changes occur prior to any observable structural alterations, creating opportunities for MRSI. 26,27 In our T 1 -weighted 31 P MRSI focusing on P i , we choose two T R and flip angle combinations, which remained close to and deviated from the optimal Ernst angle condition for cytosolic P i , allowing for T 1 weighting with the latter condition. Other metabolites are T 1 weighted in both situations; however, the weighting is amplified for PCr, PME and PDE, with T 1 relaxation rates of the order of several seconds (≥3.1 s), whereas the optimal Ernst angle condition is almost met for the βand γ-ATP resonances, with T 1 relaxation rates of around 1800 ms in the high flip angle experiment.…”

“…In conventional proton MRI, T 2 is an important biomarker to discriminate tumor from healthy tissue, aiding in diagnosis and disease prognosis. However, MRI focuses on morphological changes whilst metabolic changes occur prior to any observable structural alterations, creating opportunities for MRSI . T 2 contrast in MRSI, however, is still not available in the clinic but may increase insight into diseases when used as a biomarker including relaxation information for each metabolite separately.…”

Silica nanoparticle-based dual imaging colloidal hybrids: cancer cell imaging and biodistribution

“…[31][32][33][34][35][36][37][38][39][40] Timely multi-functional MR imaging contrast-enhancing nanoparticles have been studied in biomedical applications. [41][42][43][44][45][46][47][48][49][50][51][52] With the above in mind, we designed silica nanoparticles to have a dual imaging mode, ie, (MR) imaging and fluorescent optical imaging. Poly(ethylene glycol) (PEG) and PEG-containing block copolymers, with very flexible and hydrophilic properties, were conjugated onto the silica nanoparticles to enable them to escape uptake by the mononuclear phagocyte system.…”