MIT: MRI probe

2022: MRI Sensor Announcement

In late December 2022, using a new specialized magnetic resonance imaging sensor, MIT researchers showed that they could detect light deep in tissues such as the brain.

Imaging light in deep tissues is extremely difficult, since when light passes into the tissue, most of it is either absorbed or scattered. MIT specialists overcame this obstacle by developing a sensor that converts light into a magnetic signal that can be detected using magnetic resonance imaging (MRI).

MRI sensor created that sees light in the depths of the brain

This type of sensor can be used to map light emitted by optical fibers implanted in the brain, such as fibers used to stimulate neurons during optogenetic experiments. With further development, it may also prove useful for monitoring patients receiving light-based cancer treatments, the researchers said.

In order to make a photosensitive MRI probe, the researchers decided to enclose the magnetic particles in a nanoparticle called a liposome. The liposomes used in this study are made from specialized photosensitive lipids that Trauner previously developed. When these lipids are exposed to light of a certain wavelength, the liposomes become more permeable to water, or "leaky." This allows the magnetic particles inside them to interact with water and generate a signal that can be detected by MRI.

The particles, which the researchers called liposomal reporter nanoparticles (LisNRs), can transition from permeability to impermeability depending on the type of light they are exposed to. In this study, scientists created particles that become sealed when exposed to ultraviolet light and then become impermeable again when exposed to blue light. The researchers also showed that the particles could respond to other wavelengths of light. The scientists tested sensors in rat brains, namely a part of the brain called the striatum that is involved in motion planning and reward response. After introducing the particles into the striatum, the researchers were able to map the distribution of light from the optical fiber implanted nearby.

According to scientists, the fiber they used is similar to that used for optogenetic stimulation. In this regard, such sensing can be useful for researchers who conduct optogenetic experiments in the brain. In the future, this type of sensor may also be useful for monitoring patients receiving light-assisted treatment, such as photodynamic therapy, which uses laser or LED light to kill cancer cells.

For December 2022, researchers are working on similar probes that could be used to detect light emitted by luciferases -- a family of luminous proteins that are often used in biological experiments. These proteins can be used to determine whether a particular gene is activated or not.^[1]

Notes