Dual-contrast dynamic MRI-DOT for small animal imaging

Area of Science:

• Biomedical Imaging
• Medical Physics
• Oncology

Background:

• Accurate differentiation of benign and malignant lesions is crucial for effective cancer treatment.
• Current imaging techniques have limitations in providing comprehensive information about tissue characteristics.

Purpose of the Study:

• To develop and validate a hybrid Magnetic Resonance Imaging (MRI) and Diffuse Optical Tomography (DOT) system for simultaneous, spatially resolved kinetic analysis of optical and MR contrast agents.
• To assess the feasibility of using complementary enhancement kinetics from an optical agent (indocyanine green) and an MR agent (gadolinium-DTPA) for improved lesion characterization.

Main Methods:

• A combined MR-DOT animal imaging system with an MR-compatible fiber optic interface was utilized.
• Dynamic imaging was performed in rats with R3230 AC breast cancer tumors, acquiring 32 optical and 30 MR images over ten minutes.
• Indocyanine green (ICG) and gadolinium-DTPA (Gd-DTPA) were injected simultaneously, and contrast enhancement kinetics were analyzed.

Main Results:

• Both MR and DOT imaging demonstrated significantly higher average contrast agent enhancement in tumor regions compared to non-tumor regions (up to 10-fold for MRI, 3-fold for DOT).
• The hybrid system successfully co-registered MR and DOT data in space and time, enabling dynamic kinetic analysis.
• Distinct enhancement patterns were observed between the plasma protein-binding optical agent (ICG) and the small molecular MR agent (Gd-DTPA).

Conclusions:

• The hybrid MR-DOT imaging system is a feasible platform for dynamic, spatially resolved kinetic analysis of contrast agents.
• Complementary kinetic information from optical and MR agents holds promise for enhancing the differentiation of benign and malignant lesions.
• This study represents a critical first step towards the clinical translation of this advanced hybrid imaging technology.