However, MRI guidance is expensive, labor-intensive, and of lower spatial resolution in some cases. Sonographic (ultrasound) guidance provides the benefit of imaging using the same form of energy that is being used for therapy. The advantage of this is that the acoustic window can be verified with sonography. Therefore, if the target cannot be well visualised with sonography, then it is unlikely that FUS therapy will be effective. Temperature monitoring using small molecule library screening sonography is not yet available [2]. Inhibitors,research,lifescience,medical InSightec manufactures the ExAblate2000 which uses MRI for extracorporeal treatment of uterine fibroids (FDA-approved) with significant success, and extensive current

research focuses on investigating its application in other parts of the body [7, 8]. ExAblate technologies are Inhibitors,research,lifescience,medical used for prostate cancer or bone metastasis (ExAblate 2100 Conformal Bone System); these applications are currently under development by InSightec. The Ablatherm HIFU/US consists of a transrectal probe for prostate treatment

and has CE mark approval [9]. The Sonablate 500, an ultrasound guided system uses a transrectal probe to carry out prostate cancer focal ablation Inhibitors,research,lifescience,medical [10]. The Sonalleve HIFU/MR is an MR compatible device developed to examine a series of applications as fibroids and other body sites [11]. A recently introduced device is the transcranial MR-guided focused ultrasound. This is a hemispheric phased-array transducer (ExAblate Neuro; InSightec Ltd., Tirat Carmel, Israel) with each element driven separately, providing individual correction of skull distortion as well as electronic steering. The device received CE Mark for neurological disorders Inhibitors,research,lifescience,medical recently (December 2012). The device has been used for the treatment of neuropathic pain essential tremor and there is also evidence of possible application for brain tumours [12, 13]. Essential tremor noninterventional functional neurosurgery treatment has shown

an immense potential of transcranial MRgFUS application to induce lesions focally and treat patients Inhibitors,research,lifescience,medical nonsurgically [14]. 2. Fundamentals of Focused Ultrasound Treatments Ultrasound propagates as mechanical vibrations that induce molecules within the medium to oscillate around their positions in the direction of the wave propagation. The molecules form compressions and rarefactions that propagate the wave. The ultrasound energy is decreased others exponentially through the tissue. The decrease in acoustic energy per unit distance travelled is called “attenuation.” The rate of energy flow through a unit area, normal to the direction of the wave propagation, is called acoustic intensity. At 1MHz the ultrasound wave is attenuated about 50% while it propagates through 7cm of tissue. The attenuated energy is transformed into temperature elevation in the tissue [15, 16]. Ultrasound is transmitted from one soft tissue layer to another.