Optimization of spoiled gradient-echo phase imaging for in vivo localization of a focused ultrasound beam
✍ Scribed by Andrew H. Chung; Kullervo Hynynen; Vincent Colucci; Koichi Oshio; Harvey E. Cline; Ferenc A. Jolesz
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 888 KB
- Volume
- 36
- Category
- Article
- ISSN
- 0740-3194
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✦ Synopsis
Abstract
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~δ ϕ~) was estimated in skeletal muscle and kidney cortex in 10 rabbits. Optimized parameters included the echo time equivalent to T^*^~2~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 × 0.6 × 5 mm^3^) at power levels that are below the threshold for thermal damage of the tissue.