Temperature measurement using echo-shifted FLASH at low field for interventional MRI

Yiu Cho Chung, Jeffrey L. Duerk, Ajit Shankaranarayanan, Monika Hampke, Elmar M. Merkle, Jonathan S. Lewin

Research output: Contribution to journalArticle

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 languageEnglish (US)
Pages (from-to)138-145
Number of pages8
JournalJournal of Magnetic Resonance Imaging
Volume9
Issue number1
DOIs
StatePublished - Jan 1 1999

Keywords

  • Echo- shifted FLASH
  • Interventional MRI
  • Low-field imaging
  • MR thermometry
  • Proton resonance frequency shift

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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