Focus Correction in MR thermography for Precise Targeting in Focused Ultrasound Thalamotomy

Abstract

Purpose: To adjust the location of the ablation focus by correcting the spatial discrepancy induced by temperature changes between the target coordinate and the hotspot as seen in MR thermography. Methods: A two-step correction procedure was used to account for the chemical and k-space shifts. The first step corrected the spatial shift pixel by pixel using the field map around the focus. The second step calculated the temperature-induced TE variation map to compensate for the center location offset of the focus. Results: The approximately 1mm shift caused by chemical shift and k-space center offset was adjusted using the field map and TE error map. The mean temperature error was reduced to -0.05{\deg}C, as opposed to -0.11{\deg}C obtained using only a chemical shift correction. Conclusion: Correcting for the spatial shifts of hotspots caused by field gradients and k-space shifts in temperature changes can ensure precise targeting in FUS thalamotomy.