When we come across the term ultrasound, what usually comes to mind is a gray-scaled fetal image. Ultrasound imaging is widely used in various medicine branches, including: cardiology, gynecology, and oncology. Although a less familiar application, ultrasound can also be utilized for tissue temperature elevation. By focusing the ultrasound beams into a specific focal point, hyperthermia is induced. Such effect can be highly desirable for producing thermal coagulation to a cancerous tissue [1].
Since the heated region must be well defined, the healthy tissue unharmed, and the temperature elevated to a certain range, real time feedback is essential. The current state of the art for high spatial and temporal resolution thermometry is magnetic resonance imaging (MRI). It provides anatomical images, combined with overlaid temperature rise maps, extracted from temperature-dependent magnetic properties (such as the proton resonance frequency) [2].
As numerous tumor-related applications of MRI-guided focused ultrasound are currently FDA approved, extensive research is performed on additional medical conditions [3]. In a fascinating TED talk given by Dr. Yoav Medan [4], an utterly illegible sentence, written by a person suffering from essential tremor, is presented. Remarkably, during the same day, following an MRI-guided focused ultrasound procedure, the hand-writing becomes perfectly legible, clear evidence of the rapid improvement of the patient’s condition. An evident benefit of the described therapeutic approach is its noninvasiveness, preventing surgical complications, and minimizing recovery time.
On the student’s prospective, this exciting and developing field, which encompasses both imaging and therapy and requires understanding of physical effects as well as medical physiology, seems as an attractive discipline to explore.
References
- Roberts, “Magnetic resonance-guided focused ultrasound for uterine fibroids,” Seminars in interventional radiology, vol. 25, pp. 394-405, 2008.
- V. Rieke and K. Butts Pauly, “MR thermometry,” Journal of Magnetic Resonance Imaging, vol. 27, pp. 376-390, 2008.
- D. L. Miller, N. B. Smith, M. R. Bailey, G. J. Czarnota, K. Hynynen, and I. R. S. Makin, “Overview of therapeutic ultrasound applications and safety considerations,” Journal of Ultrasound in Medicine, vol. 31, pp. 623-634, 2012.
- Y. Medan. “Ultrasound surgery—healing without cuts“, In: TED Talks. TED Conferences,LLC; 2011.