Research Projects

Hyperpolarized carbon-13 metabolic MRI

Hyperpolarized carbon-13 magnetic resonance imaging (MRI) is a relatively new type of imaging study which offers novel metabolic information and contrast, unlike conventional MRI which provides primarily anatomical information.  It is particularly promising for cancer imaging applications, such as disease staging, surgical planning, and monitoring response to therapy, because it highlights functional changes in cellular activity.  UCSF has been a leader in this field, performing the first in vivo human studies in prostate cancer patients.  (Featured in a news segment from KTVU)

Hyperpolarized carbon-13 MRI requires specialized methods because, unlike conventional MRI, the signal decays rapidly and is unrecoverable.  Our group is working to develop new rapid and efficient hyperpolarized MRI methods, including dynamic metabolic imaging for localized perfusion and rate information, new contrast generation methods to distinguish metabolites in different compartments (ie blood vessels, intracellular, extracellular), and development of specialized techniques for simultaneous imaging of multiple carbon-13 agents.

Autonomous Imaging with Real-time Feedback and Calibration

Our group has recently develop methods to perform "push-button", autonomous hyperpolarized MRI scans.  The user sets up a region of interest (ROI) to be studied, and then starts the imaging acquisition with the hyperpolarized injection.  Our software will then perform all required calibrations of the experiment timing (bolus tracking) and MRI system (B0, B1 calibration), followed by a fast metabolic imaging scan.  This is built using the RTHawk Research Platform from HeartVista. 

Experiment Recordings

Dynamic Imaging Examples



Dynamic imaging provides robust measures of metabolism and also perfusion kinetics

Perfusion and Cellular Transport Imaging Examples


We can both separate flowing spins and also improve tumor contrast where there is altered cellular transport.

Lung MRI

We are working to make MRI of the lungs a viable and valuable imaging modality by eliminating need for sedation or breath-holding, and encoding breathing mechanics for unique functional information.  Since it uses MRI, there is no ionizing radiation, making this safer than CT scans which are typically used for lung imaging.  This is particularly important for pediatric applications since early exposure to ionizing radiation from CT is linked to increased cancer risk (https://www.imagegently.org/), and also allows for repeated, regular lung imaging scans without risk.


Lung imaging using UTE MRI, including resolution of the respiratory dynamics.  See more examples and explanation of how this image was created at 
https://www.youtube.com/playlist?list=PLjBt5Iq93BT9reE-1k9KMtmNeivc_YihY

Semi-Solid Tissue MRI

In conventional MRI techniques, tissues with rapid transverse relaxation times (< 2 ms) are undetectable and thus appear invisible.  These tissues are solid or semi-solid, and include cortical bone, tendons, and other connective tissues, as well as certain components of cartilage, ligaments, and myelin.  Ultrashort echo time (UTE) and Zero Echo Time (ZTE) MRI use specialized RF pulses and acquisition schemes to detect signal from these tissues.  This provides positive contrast that may be clinically valuable when observing these types of tissues.

Our group is working on techniques to improve UTE and ZTE MRI, including novel contrast generation through RF pulses and multiple echo times, accelerated acquisitions, and improved image reconstructions. We are also exploring several clinical applications of UTE and ZTE MRI, including assessing tendon quality, measuring bone density for PET/MR systems, imaging lung nodules, evaluating pulmonary disease with MRI, and imaging myelin.


Tendon, meniscus, and bone imaging using UTE and ZTE MRI

PET/MRI

Hybrid PET/MRI systems are recently introduced commercially, and combine the functional information from PET tracers with the soft-tissue contrast from MRI.  We are working on motion management, quantitatifive imaging, and lung imaging for this emerging modality.


UTE MRI allows for visualization of small pulmonary nodules with PET/MRI


Quantitative PET reconstruction in the pelvis, using a deep learning strategy for generating MR-derived attenuation maps


Quantitative PET reconstruction in the liver, using motion-resolved MRI methods for motion and attenuation correction