| Description |
Focused ultrasound (FUS) therapy is a noninvasive ablation technique currently with FDA approval to treat several maladies including uterine fibroids, palliation of bone metastases, prostate cancer, and essential tremor. Due to its noninvasive nature, magnetic resonance-guided focused ultrasound (MRgFUS) is an attractive alternative to surgical cancer therapy, and it has the additional benefit of lacking the debilitating side effects associated with radiation or chemotherapy. MR guidance provides anatomical imaging and near real-time temperature measurement for monitoring treatment safety and thermal dose delivery. Early stage human trials are currently underway using MRgFUS to noninvasively treat breast cancer. By focusing the ultrasound waves into a small region, MRgFUS can selectively heat precise locations in deep tissues. This makes it possible to thermally ablate tumors while sparing healthy tissue. While phase aberration effects that distort the ultrasound beam's focus, decrease peak beam intensity, and cause heating in unwanted regions are well documented for transcranial treatments, their effects on heterogeneous soft tissues, such as the breast, are less known. This work evaluates the effect of phase aberrations in breast MRgFUS treatments and employs a correction technique to make procedures more efficient by reducing heating in normal tissues and increasing the energy deposited in the desired focal region. This evaluation has been performed through simulations and controlled iv phantom studies, and finally extended and validated in heterogeneous anatomicallymimicking breast phantoms. Because MRgFUS is still in its infancy, protocols and methods have yet to be established for a complete and consistent thermal therapy. The work presented in this dissertation aids in clarifying aspects of MRgFUS thermal therapy by providing quantitative and qualitative guidelines for clinicians to use with breast cancer treatment planning, and also by providing phantoms for quality assurance testing. Also, the development of MRgFUS-specific tissue-mimicking phantoms allows for verification of the safety and efficacy of therapeutic techniques used by researchers and clinicians. In combination, the methods developed for this dissertation improve MRgFUS treatment planning and verification, and assist the clinical adoption of MRgFUS thermal therapies. |
