Magneto-Caloric MRI Particles

Magnetic resonance imaging (MRI) is widely used as a noninvasive clinical diagnostic tool that uses a magnetic field and radio waves to create the detailed images of cells/tissues/organs within the body. However, conventional MRI contrast agents in typical MRI magnetic fields show very weak dependence of magnetization with respect to temperature or magnetic field. A magneto-caloric material provides an alternative to gadoliniumbased contrast agents used for MRI.

Researchers at HHMI’s Janelia Research Campus and the National Institutes of Health have developed the use of magneto-caloric materials as switchable and tunable contrast agents for MRI based on the observation that magneto-caloric materials have a sharp transition of magnetization at physiological temperatures and typical MRI magnetic fields. As an example, Iron-Rhodium (FeRh), a proto-typical magneto-caloric material, was tested as a MRI contrast agent. A typical FeRh disk sample exhibits a sharp transition from an antiferromagnetic to a ferromagnetic state over physiologically relevant temperatures (Fig. 1).

Fig. 1 Magnetic moment vs. temperature of FeRh disk sample at various constant DC bias magnetic fields

Further, the sample exhibits a sharp transition at large DC magnetic field values and around physiologically relevant temperatures (Fig. 2). These results clearly show that FeRh has MRI contrast changes due to the temperature tunable magnetic state of the material in the MRI compatible magnetic field range and physiologically relevant temperature range.

Fig. 2 Magnetic moment vs. magnetic field of FeRh disk sample at various constant temperatures

Advantages:

• Magneto-caloric materials have sharp magnetic phase transitions at typical physiological temperatures and in the presence of the large DC magnetic field values associated with MRI machines, making them uniquely suitable for the development of novel MRI contrast agents.
• Magneto-caloric materials can be made to be a switchable MRI contrast agent, allowing magnetocaloric materials to be sharply visible or invisible in typical MRI procedures by small changes in temperature or magnetic field.
• Magneto-caloric materials can be made to be a tunable MRI contrast agent using various material science techniques such as alloying and doping.

Applications:

• MRI

Opportunity:

Commercial License or Non-Profit Research