Development of MR Thermometry Strategies for Hyperthermia of Extremity and Breast Tumors

Abstract

Numerous studies have shown that the combination of radiation therapy and hyperthermia, when delivered at moderate temperatures (40°-45°C) for sustained times (30-90 minutes), can help to provide palliative relief and augment tumor response, local control, and survival. However, the dependence of treatment success on achieved temperature highlights the need for accurate thermal dosimetry, so that the prescribed thermal dose can be delivered to the tumor. This can be achieved noninvasively with MR thermometry. However, there are many challenges to performing MR thermometry in the breast, where hyperthermia of locally advanced breast cancer can provide a benefit. These include magnetic field system drift, fatty tissue, and breathing motion. The purpose of this research was to develop a system for the hyperthermia treatment of LABC while performing MR thermometry. A hardware system was developed for performing the hyperthermia treatment within the MR bore. Methods were developed to correct for magnetic field system drift and to correct for breath hold artifacts in MR thermometry of the tumor using measurement of field changes in fat references. Lastly, techniques were developed for measuring temperature in the fatty tissue using multi-echo fat water separation methods, reducing the error of performing MR thermometry in such tissues. All of these methods were characterized with phantom and in vivo experiments in a 1.5T MR system. The results of this research can provide the means for successful hyperthermia treatment of LABC with MR thermometry. With this thermometry, accurate thermal doses can be obtained, potentially providing improved outcomes. However, these results are not only applicable in the breast, but can also be used for improved MR thermometry in other areas of the body, such as the extremities or abdomen.