The secondary tissue damage remote from the focal spot in the last brain patient at the Brigham and Women’s Hospital in Boston raised many questions in the MRgFUS community. As the damages were produced outside focus, they are most probably due to either migration of cavitation bubble through the blood flow, or by secondary focal spots.
As tragically, a recent phase II clinical trial using Transcranial Low-Frequency Ultrasound-Mediated Thrombolysis in Brain Ischemia (TRUMBI study), was stopped prematurely because of the occurrence of a high number of intracerebral hemorrhages after tPA treatment combined with transcranial sonication. It was using a 300 kHz dual transducer array with long pulse length (765mm). In this latter case, standing waves have been shown to be present and potentially contribute to tissue damage with the use of the unfocused low frequency ultrasound device used in the TRUMBI study: this was demonstrated by a simulation study(Baron et al. 2009).
Furthermore, accurate and validated computer simulations are needed
Several different methods have been used in the past to estimate ultrasound field propagation through the (for example (Aubry et al. 2001;Aubry et al. 2003;Clement and Hynynen 2002;Clement et al. 2004;Connor and Hynynen 2004)). This study proposes to extend the use of those programs in order to investigate the pressure distribution in the brain by taking into account all the reflections that can occur in the brain case, as well as answering the degree of importance of standing waves in some areas of the brain during trans-skull ultrasound treatments of brain.
No reports found.