Apoptosis in ultrasound-produced threshold lesions in the rabbit brain

Focused ultrasound (US) surgery has been used to induce high temperature el evations in tissue to coagulate the proteins and kill the tissue. The intro duction of noninvasive online temperature monitoring has made it possible t o induce well-controlled thermal exposures. In this study, we used magnetic resonance imaging (MRI) thermometry to monitor thermal exposures near the threshold of tissue damage, and then investigated if apoptosis was induced. Rabbit brains were sonicated with an eight-sector phased array to create a large region of uniform temperature elevation at the end of a 30-s sonicat ion. Histological examination demonstrated that apoptosis was induced in so me cells. At 4 h after the sonications, the apoptotic cells constituted 9 /- 7% of identifiable cells. By 48 h after the sonications, the number of a poptotic cells had increased up to 17 +/- 9%. The impact of this finding fo r therapy needs to be explored further. (E-mail: kullervo@bwh.harvard.edu) (C) 2001 World Federation for Ultrasound in Medicine & Biology.