UCSF

Magnetic Resonance Spectroscopic Imaging or MRSI is a noninvasive medical imaging modality the combines the principles of magnetic resonance imaging and spectroscopy to measure relative concentrations of metabolites in an array of voxels throughout the brain. Primary brain tumors are typically aggressive lesions that are difficult to treat and have a relatively poor prognosis for many patients. By showing metabolically active infiltrative tumor that can look similar to surrounding tissues on conventional MR images, MRSI allows for a more accurate definition of the extent of the disease. Despite those benefits, MRSI has not been widely used to care for patients with brain tumors. Two major difficulties encountered in implementing MRSI in a clinical setting are limited coverage and difficulty in prescription.

The goal of this dissertation work was to make MRSI more useful in the clinical setting. Several new techniques have been developed to automate MRSI prescription and acquisition, improve the coverage of the brain and ensure high quality data. They included automated placement of outer volumes suppression (OVS) bands for suppression of the subcutaneous lipid signal, placement of the excitation volume or slice and automated oblique shimming.

These techniques were validated on healthy volunteers and patients with brain tumors. They allowed the acquisition of MRSI data from a much larger brain volumes than the conventional methods and resulted in more comprehensive and consistent MRSI datasets while maintaining high data quality.

The results of this work show that automated prescription can help solve two of the most significant problems with brain PRESS MRSI acquisitions: limited brain coverage and difficulty in prescription. The improved coverage will be useful for evaluating heterogeneous and infiltrative tumors, which are difficult to evaluate with current protocols. It should make possible a more accurate assessment of the progression of tumors in serial studies. The use of this technique reduced the need for extensive operator training, thus facilitating wider utilization of MRSI in the clinical setting. The automated MRSI protocols have been implemented in the ongoing clinical research studies and used to acquire data from hundreds of patients with brain tumors.