A new paramagnetically shifted imaging probe for MRI.

Area of Science:

• Biomedical Imaging
• Chemical Engineering
• Materials Science

Background:

• Magnetic Resonance Imaging (MRI) is a powerful non-invasive imaging technique.
• Development of targeted contrast agents enhances MRI sensitivity and specificity.
• Paramagnetic contrast agents are crucial for molecular imaging applications.

Purpose of the Study:

• To develop and characterize a novel paramagnetic contrast agent for molecular imaging by MRI.
• To enable direct MRI detection of the contrast agent independent of tissue water signals.
• To explore the potential for physiological monitoring using this new agent.

Main Methods:

• A dysprosium(III) complex with tert-butyl reporter groups was synthesized.
• The complex was characterized in phantoms and imaged in mice at 7 Tesla using 3D gradient echo and MRSI sequences.
• Biokinetics and temperature dependence of the agent were assessed in vivo.

Main Results:

• The contrast agent exhibited fast T1 relaxation (8 ms) and a large paramagnetic shift (>60 ppm).
• High sensitivity was achieved due to fast relaxation and short repetition times.
• Direct, frequency-selective excitation and acquisition of the agent were demonstrated, with a detection limit of ~23 µM.
• In vivo biokinetics were monitored with 62 s temporal resolution.
• The temperature dependence of the paramagnetic shift was utilized to examine tissue temperature variations.

Conclusions:

• A new MRI contrast agent was successfully developed and characterized.
• The agent demonstrates potential for sensitive molecular imaging and real-time physiological monitoring.
• The study highlights the utility of paramagnetic agents for advanced MRI applications, including temperature sensing.