Abstract
We investigated the feasibility of using echo-shifted fast low-angle shot (FLASH) for temperature-monitored thermotherapeutic procedures in a 0.2 T interventional magnetic resonance (MR) scanner. Based on the proton resonance frequency shift technique, modified echo-shifted FLASH has sufficiently high signal-to-noise ratio to provide accurate temperature maps with short scan times, i.e., 5 seconds in phantoms (TR = 20.5 msec; effective TE = 30 msec; one echo shift; NSA = 2) and ex vivo experiments (TR = 19.4 msec; effective TE = 28.9 msec; one echo shift; NSA = 2) and 3 seconds (TR = 19.4 msec; effective TE = 28.9 msec, one echo shift; NSA 1) for an in vivo case. The proton resonance frequency shifts with temperature observed in a 0.2 T MR scanner using this sequence were -0.0072 ppm/°C (temperature uncertainty = ±2.5°C) for polyacrylamide phantoms and -0.0086 ppm/°C (temperature uncertainty = ± 1°C) for ex vivo bovine liver. These experiments demonstrated that echo-shifted FLASH is a viable method for low- field temperature despite the decreased signal and decreased phase sensitivity compared with its counterpart in a 1.5 T MR imaging system. The improved temporal resolution of temperature images, now possible in low- field interventional MR systems using echo-shifted FLASH will allow clinicians more accurate monitoring of interstitial ablation in MR-guided interventional procedures.
Original language | English (US) |
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Pages (from-to) | 138-145 |
Number of pages | 8 |
Journal | Journal of Magnetic Resonance Imaging |
Volume | 9 |
Issue number | 1 |
DOIs | |
State | Published - Jan 1999 |
Externally published | Yes |
Keywords
- Echo- shifted FLASH
- Interventional MRI
- Low-field imaging
- MR thermometry
- Proton resonance frequency shift
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging