Treatment planning for MR-guided focused ultrasound surgery

MR-guided Focused ultrasound surgery (MRgFUS) is rapidly gaining clinical acceptance worldwide for procedures throughout the body. However, focusing abilities are still limited by scattering and refraction of ultrasound by heterogeneous tissues, often causing unpredictable results. Presently, a new treatment planning method is proposed that performs ultrasound phase-aberration correction using diagnostic pre-imaging combined with wavevector-space modeling of the ultrasound and thermal fields. The kernel of the wavevector model is described, and the ability to predict both reflective (spectral) and point-like scattering is assessed. The model is tested by propagating 1 MHz focused ultrasound through a 50 mm x 50 mm x 40 mm tissue section, with varying degrees of heterogeneity. Both spectral echoes and small scattering were successfully replicated with the model, which then could be used to predict and offset ultrasound phase distortion. It is concluded that the wavevetor-domain kernel, when similarly applied in the clinic, will result in improved and expanded treatment volumes.