Ultrasound Thermography: Principles, Methods, and Experimental Results

Focused ultrasound (FUS) is also gaining acceptance as a method for minimally invasive or noninvasive thermotherapy. The role of temperature feedback in thermal coagulation may be less critical than in hyperthermia applications, but knowledge of the spatial and temporal temperature distribution is certainly helpful. Energy-based applicators for noninvasive and minimally invasive thermal therapy applications are becoming increasingly more capable with sophisticated control capabilities. This chapter describes the echo shift method and discusses application of ultrasound thermography. The combined imaging/therapy system presents an excellent setup to characterize the performance of ultrasound thermography in a controlled environment. The raw time-shift estimates typically present a spatially random ripple due to RF- echo decorrelation resulting from the thermo-acoustic lens effect introduced by the heated region. The in vivo results unequivocally demonstrate that the sensitivity of the echo shift method is quite high for relatively static tissue targets even in the presence of pulsation.