Optimization of spoiled gradient-echo phase imaging for in vivo localization of a focused ultrasound beam

Andrew H. Chung, Kullervo Hynynen, Vincent Colucci, Koichi Oshio, Harvey E. Cline, Ferenc A. Jolesz

Research output: Contribution to journalArticle

154 Citations (Scopus)


The parameters of a spoiled gradient-echo (SPGR) pulse sequence have been optimized for in vivo localization of a focused ultrasound beam. Temperature elevation was measured by using the proton resonance frequency shift technique, and the phase difference signal-to-noise ratio (SNR(Δφ)) was estimated in skeletal muscle and kidney cortex in 10 rabbits. Optimized parameters included the echo time equivalent to T2* of the tissue, the longest repetition time possible with a 20-s sonication, and the flip angle equivalent to the Ernst angle. Optimal SPGR phase imaging can detect a sonication beam with a peak phase difference of 0.55 radian, which corresponds to a temperature elevation of 7.3°C. The sonication beam can be localized within one voxel (0.6 x 0.6 x 5 mm3) at power levels that are below the threshold for thermal damage of the tissue.

Original languageEnglish
Pages (from-to)745-752
Number of pages8
JournalMagnetic Resonance in Medicine
Issue number5
Publication statusPublished - 1996 Nov 1
Externally publishedYes



  • focused ultrasound surgery
  • noninvasive thermometry
  • optimization
  • phase imaging

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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