ABSTRACT
The ability to use magnetic resonance (MR) for the accurate targeting of delivery of high-
intensity focused ultrasound, together with the easy depiction of tissue thermals results,
means that focused ultrasound surgery (FUS) can potentially be used in a wide variety of
applications in the body. Different inherent tissue responses to heating and variable
heating responses due to alterations in vascularity can be easily appreciated using online
thermal mapping carried out with MR in response to focused ultrasound heating. As a
result, it is relatively easy to take steps to overcome different tissue responses either
between individuals or within an individual so that a consistent and accurately placed
lesion can be produced with each sonication. Multiple alterations in the parameters of the
ultrasound deposition can be carried out such as power, spot site, cooling durations,
frequency of transducer, etc. to interact with tissue variations and keep the response
visualized in the tissues constant. Similarly, areas of subtle tissue abnormality that may
not be visualized on other modalities, such as ultrasound or computed tomography, are
frequently easily appreciated on MR and therefore complex targeting of such
abnormalities can be quite readily achieved using online MR imaging.
