Advancements in MRI Temperature Map Reconstruction for Real-Time Guidance of Thermal Therapies
The goal of the presented work is to develop robust magnetic resonance imaging (MRI) techniques to improve current and enable future applications of thermal therapies. Focused ultrasound therapy is an emerging treatment that can noninvasively heat small areas in the body to stimulate or destroy the tissue depending on the dose used. This approach has been applied to treat cancer, essential tremor, and other conditions without surgery. Fundamentally, though, current treatments are limited by the performance of available temperature monitoring methods. Tracking temperature changes is critical to performing the treatment both successfully and safely. In particular, more accurate and rapid temperature imaging throughout the tissue is needed to support these procedures. Imaging temperature changes throughout a complete area of the body during the few seconds it takes to deliver the treatment requires faster measurements. This dissertation describes methods to produce accurate heating estimates from undersampled data, which reduces measurement time. By leveraging a constrained temperature model, our approach will avoid both image aliasing artifacts and blurring in time that are incurred by other acceleration methods. To translate faster temperature imaging to focused ultrasound treatments of the brain, which are complicated by additional equipment that is also present in the image, we will adapt the first method to estimate temperature only the brain region while recovering signal from the rest of the image. To improve measurement accuracy, a fast algorithm correcting image and temperature map distortions caused by tissue heating is presented. Improved measurements will provide a more complete picture of heating in the body, which will directly translate to improvements in safety and efficacy of heating treatments. Faster temperature imaging will enable volumetric monitoring, which is needed for continuous thermal targeting across a treatment zone and for expanding the zone of currently treatable regions. More accurate temperature imaging will improve both the localization of thermal targets and measurement of the thermal rise generated. MRI-guided focused ultrasound technology has the potential for significant positive impact on patient treatment by offering both reduced tissue damage and recovery time compared to traditional surgery.