High resolution breast MRI [electronic resource]

Breast cancer is the second leading cause of female cancer death in the United States with an average lifetime risk of 1 in 8. Early detection of the disease and subsequent treatment increase the chance of survival. X-ray mammography is the standard imaging technique for breast cancer screening, but it is difficult to identify malignant lesions in women with dense breasts using x-ray mammography. Dynamic-contrast-enhanced (DCE) magnetic resonance imaging (MRI) has provided high sensitivity for breast cancer diagnosis due to its excellent soft tissue contrast, but there have been varied reports on its specificity. A recent study with a small surface coil has shown that high spatial and temporal resolution breast DCE MRI can improve sensitivity and specificity of ductal carcinoma in situ diagnosis by visualizing smaller scale features such as ductal and periductal enhancement. However, a small surface coil is not suitable for screening or bilateral staging exams where volumetric coverage of both breasts is necessary. Conversely, many commercially-available breast coils offer volumetric coverage of the breasts, but the large coil elements limit the signal-to- noise ratio (SNR) and thus the ability to increase spatial and temporal resolution with high parallel imaging acceleration factors. To address these concerns, we have designed and developed a custom-fitted 18-channel, bilateral breast radiofrequency (RF) coil array for providing high-resolution images in clinically-feasible scan times. The purpose of this work was three-fold: outline the construction process of a high- SNR custom-fitted array, benchmark its performance compared to a commercial design, and evaluate its utility for high-resolution clinical breast MRI. By placing a chain of overlapping small coil elements close to the tissue, we were able to obtain high SNR over the entire breast volume for medium-sized women. To reduce the overall exam time, we laid the coil elements in a geometry that facilitated bidirectional parallel imaging. Comparing the custom-fitted array to a commercially-available 8-channel breast array, the results show 3.6 times higher average SNR and superior parallel imaging quality for the custom-fitted array in volunteers. Using parallel imaging and taking advantage of the SNR benefits from the 18-channel coil array, we clinically demonstrated a 10-fold improvement in spatial resolution over the current Stanford Hospital protocol. We have conducted a clinical study comparing the diagnostic quality of high-resolution scans with the 18-channel array versus lower resolution scans in patients with suspicious lesions on mammography. The initial findings show that the improved resolution enables better depiction of overall lesion morphology and tissue interfaces. In summary, we have presented a method for constructing an 18-channel custom-fitted breast RF array and demonstrated its SNR and parallel imaging benefits. In a clinical setting, our initial findings show improved morphology characterization in high-resolution exams with the 18-channel array.

Keywords: Bioengineering.
Advisor: Hargreaves Brian Andrew primary advisor. Thesis advisor
Daniel Bruce (Bruce Lewis) advisor. Thesis advisor
Gold Garry E.