A dedicated automated injection system for dynamic contrast-enhanced MRI experiments in mice

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Pharmacokinetics

Background:

• Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) is crucial for assessing tissue perfusion and vascularity.
• Accurate delivery of contrast agents (CA) in small animals is challenging due to small volumes and anatomical constraints.

Purpose of the Study:

• To develop and validate a reproducible small-animal DCE-MRI setup for precise CA injection (<100 μL) in mice.
• To evaluate the system's performance in measuring pharmacokinetic parameters in resting muscle and tumor tissues.

Main Methods:

• A novel CA injection system using MR-compatible syringe pumps and microbore tubing was designed to minimize dead volume (<10 μL).
• The setup was tested in CB-17 SCID mice with orthotopic neuroblastoma, delivering diluted Gd-DTPA CA via retro-orbital injections.
• DCE-MRI measurements were performed, followed by pharmacokinetic analysis.

Main Results:

• The CA injection system demonstrated successful delivery in 19 of 24 experiments with minimal bolus dispersion.
• Pharmacokinetic parameters (K(trans), k(ep), v(e), v(p)) obtained from DCE-MRI in resting muscle and tumor tissues were consistent with previously reported values.
• The system proved effective for DCE-MRI in mice with significant tumor burden.

Conclusions:

• A reproducible DCE-MRI setup with short injection lines and low dead volume was successfully developed and implemented.
• The system is versatile and can be utilized at various field strengths with appropriate fringe field management (<40 mT).