T2*-relaxivity contrast imaging: first results.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biomedical Engineering
• Medical Imaging Physics

Background:

• Dynamic contrast-enhanced MRI (DCE-MRI) is a standard technique for tumor imaging.
• Existing methods like plasma volume and interstitial volume lack detailed structural information.
• Novel contrast generation methods are needed to enhance MRI's diagnostic capabilities.

Purpose of the Study:

• To introduce and validate T2*- relaxivity contrast imaging (RCI) as a novel MRI technique.
• To assess the accuracy and precision of RCI-derived parameters (r*2,vasc and r*2,EES).
• To compare RCI's ability to characterize tumor structure against traditional DCE-MRI parameters.

Main Methods:

• Development of T2*- relaxivity contrast imaging (RCI) for MRI.
• Generation of images reflecting relaxivities r*2,vasc and r*2,EES.
• Noise sensitivity assessment using simulation studies.
• Application of RCI to five colorectal tumor xenografts in nude mice.

Main Results:

• RCI-derived parameters (r*2,vasc and r*2,EES) demonstrated accuracy and precision comparable to plasma and interstitial volumes.
• Significant differences in mean relaxivity values were observed (r*2,vasc=10.9±2.9 mM(-1) s(-1), r*2,EES=15.6±2.6 mM(-1) s(-1)).
• RCI images revealed distinct tumor structures compared to plasma volume and interstitial volume maps, with weak correlations (r=0.67 and r=0.52, respectively).

Conclusions:

• T2*- relaxivity contrast imaging (RCI) is a feasible MRI technique.
• RCI provides supplementary information on tumor vasculature and extracellular space.
• RCI offers a novel approach for characterizing tumor microenvironment and structure.