The primary purpose of this work was to evaluate the capability of nanoparticles to transform electromagnetic energy at microwave frequencies into therapeutic heating. Targeted nanoparticles, in conjunction with microwave irradiation, can increase the temperatures of the targeted area over the peripheral region. Therefore, to become clinically viable, microwave absorbing nanoparticles must first be identified, and a system to monitor the treatment must be developed. In this study, ultrasound temperature imaging was used to monitor the temperature of deep lying structures. First, a material-dependent quantity to correlate the temperature induced changes in ultrasound images (i.e. apparent time shifts) to differential temperatures was gathered for a tissue-mimicking phantom, porcine longissimus dorsi muscle, and porcine fat. Then microwave nanoabsorbers were identified using an infrared radiometer. The determined nanoabsorbers were then injected into ex-vivo porcine longissimus dorsi muscle tissue. Ultrasound imaging frames were gathered during microwave treatment of the inoculated tissue. Finally, the ultrasound frames were analyzed using the correlation between temperature and apparent shifts in ultrasound for porcine muscle tissue. The outcome was depth-resolved temperature profiles of the ex-vivo porcine muscle during treatment. The results of this study show that magnetite is a microwave nanoabsorber that increases the targeted temperature of microwave hyperthermia treatments. Overall, there is clinical potential to use microwave nanoabsorbers to increase the efficiency of microwave hyperthermia treatments. / text