Targeting accuracy of transcranial magnetic resonance-guided high-intensity focused ultrasound brain therapy: a fresh cadaver model Laboratory investigation

Object. This work aimed at evaluating the accuracy of MR-guided high-intensity focused ultrasound (MRgHIFU) brain therapy in human cadaver heads. Methods. Eighteen heads of fresh human cadavers were removed with a dedicated protocol preventing intracerebral air penetration. The MR images allowed determination of the ultrasonic target: a part of the thalamic nucleus ventralis intermedius implicated in essential tremor. Osseous aberrations were corrected with simulation-based time reversal by using CT data from the heads. The ultrasonic session was performed with a 512-element phased-array transducer system operating at 1 MHz under stereotactic conditions with thermometric real-time MR monitoring performed using a 1.5-T imager. Results. Dissection, imaging, targeting, and planning have validated the feasibility of this human cadaver model. The average temperature elevation measured by proton resonance frequency shift was 7.9 degrees C +/- 3 degrees C. Based on MRI data, the accuracy of MRgHIFU is 0.4 +/- 1 mm along the right/left axis, 0.7 +/- 1.2 mm along the dorsal/ventral axis, and 0.5 +/- 2.4 mm in the rostral/caudal axis. Conclusions. Despite its limits (temperature, vascularization), the human cadaver model is effective for studying the accuracy of MRgHIFU brain therapy. With the 1-MHz system investigated here, there is millimetric accuracy. (http://thejns.org/doi/abs/10.3171/2013.1.JNS12559)