Micro- and nanobubbles have been used in ultrasound imaging to highlight diseased tissue, specifically
tumors, to aid physicians in detecting disease. These bubbles can also be filled with therapeutic drugs, and
popped using ultrasound energy when they are at the desired location. While these bubble-based contrast
agents make tumors easier to see on ultrasound images, it can still be challenging to recognize anatomical
structures in ultrasound images due to the relatively poor soft tissue contrast of this modality. Ultrasound
imaging is also limited in penetration depth at the higher frequencies needed for imaging, which can make
some applications including body imaging challenging. On the other hand, Magnetic Resonance Imaging (MRI)
is able to image large organs such as the liver with exquisite contrast and complete coverage. The drawback of
MRI is that its low sensitivity makes the detection of small cancerous lesions challenging, and treatment of the
tumor cannot be initiated non-invasively with MRI.
The goal of this project is to explore the use of ultrasound-activated nanobubbles as a switchable MRI contrast
agent to enable the rapid and effective detection and treatment of metastatic disease. Here, the effect of the
presence of micro- and/or nanobubbles, both with and without the application of ultrasound energy, on the MRI
signal will be tested. We hypothesize that the mere presence of small bubbles will have little impact on the MRI
signal, but that the MRI signal can be dramatically altered on a rapid timescale by applying ultrasound energy
to the bubbles. The formulation of the bubbles will be revisited to maximize their ability to alter the surrounding
magnetic field and thus affect the MRI signal, and various forms of MRI data collection will be tested to enable
rapid localization of the bubbles. Note that the switchable nature of this contrast agent, which is truly unique in
MRI, will have a profound impact on how the MRI data can be collected, opening the door for innovative
strategies for acquiring data and generating images. This exploratory project will pave the way for testing of
this novel switchable MRI contrast agent in vivo for robust detection and efficient treatment of small metastatic
tumors. Note that the team includes an expert on nanobubble design for ultrasound contrast agents, an MRI
physicist renowned for developing innovative data collection and image reconstruction methods, and a second
MRI physicist who has both the experience in combined MRI/ultrasound and access to the tools needed to
perform this work.