Abstract #1802

Analysis of Focused Ultrasound Hotspot Appearance on EPI and Spiral MR Imaging

Sonal Josan¹, Andrew B. Holbrook,¹², Elena Kaye,^1,3, Christine Law,^1,3, Kim Butts Pauly¹

¹Radiology, Stanford University, Stanford, CA, United States; ²Bioengineering, Stanford University, Stanford, CA, United States; ³Electrical Engineering, Stanford University, Stanford, CA, United States

MR thermometry relies on the proton resonance frequency shift with temperature, which can produce off-resonance artifacts in EPI and spiral sequences. This work analyzed the appearance of the focused ultrasound (FUS) hotspot on several EPI and Spiral trajectory designs through simulations and FUS experiments. The distortion of the FUS spot with single shot EPI or Spiral imaging can be severe for the high temperature changes used in ablation, and may lead to under-estimation of the peak temperature. Multi-shot sequences can be used to reduce the shifts/distortion to a tolerable level.