A Polymer-Based Magnetic Resonance Tracer for Visualization of Solid Tumors by .sup.13C Spectroscopic Imaging

• Published in: PloS one Vol. 9; no. 7
• Main Authors: Suzuki, Yoshikazu, Iida, Mitsuru, Miura, Iwao, Inubushi, Toshiro, Morikawa, Shigehiro
• Format: Journal Article
• Language: English
• Published: Public Library of Science 09.07.2014
• Subjects: Diagnostic imaging; Polymer industry; Polymers; Polyols; Tracers (Biology); Tumors
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0102132

Morphological imaging precedes lesion-specific visualization in magnetic resonance imaging (MRI) because of the superior ability of this technique to depict tissue morphology with excellent spatial and temporal resolutions. To achieve lesion-specific visualization of tumors by MRI, we investigated the availability of a novel polymer-based tracer. Although the .sup.13 C nucleus is a candidate for a detection nucleus because of its low background signal in the body, the low magnetic resonance sensitivity of the nucleus needs to be resolved before developing a .sup.13 C-based tracer. In order to overcome this problem, we enriched polyethylene glycol (PEG), a biocompatible polymer, with .sup.13 C atoms. .sup.13 C-PEG40,000 (.sup.13 C-PEG with an average molecular weight of 40 kDa) emitted a single .sup.13 C signal with a high signal-to-noise ratio due to its ability to maintain signal sharpness, as was confirmed by in vivo investigation, and displayed a chemical shift sufficiently distinct from that of endogenous fat. .sup.13 C-PEG40,000 intravenously injected into mice showed long retention in circulation, leading to its effective accumulation in tumors reflecting the well-known phenomenon that macromolecules accumulate in tumors because of leaky tumor capillaries. These properties of .sup.13 C-PEG40,000 allowed visualization of tumors in mice by .sup.13 C spectroscopic imaging. These findings suggest that a technique based on .sup.13 C-PEG is a promising strategy for tumor detection.