Reduction of noise from MR thermometry measurements during HIFU characterization procedures

Subhashish Dasgupta, Prasenjeet Das, Janaka Wansapura, Prasanna Hariharan, Ron Pratt, David Witte, Matthew R. Myers, Rupak K. Banerjee

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Magnetic resonance (MR) thermometry is a valuable method for characterizing thermal fields generated by high intensity focused ultrasound (HIFU) transducers in tissue phantoms and excised tissues. However, infiltration of noise signals generated by external rf sources into the scanner orifice limits the ability of the scanner to measure temperature rise during the heating or ablation phase. In this study, magnetic resonance interferometry (MRI) monitored HIFU ablations are performed on freshly excised porcine liver samples, at varying sonication times, 20 s, 30 s, and 40 s at a constant acoustic intensity level of 1244 W/cm2. Temperature throughout the procedure was measured using proton resonant frequency MR thermometry. Without filtering, reliable temperature measurements during the heating phase could not be obtained since temperature maps appeared blurred and analysis was impossible. Also, measurements acquired during the cooling phase decayed manifested an unrealistically slow rate of temperature decay. This abnormally slow rate was confirmed with computational results. A low-pass RC filter circuit was subsequently incorporated into the experimental setup to prevent infiltration of noise signals in the MRI orifice. This modified RC filter circuit allowed noninvasive measurement of the HIFU induced temperature rise during the heating phase followed by temperature decay during cooling. The measured data were within 13% agreement with the temperature rise computed by solving the acoustic and heat equations.

Original languageEnglish (US)
JournalJournal of Nanotechnology in Engineering and Medicine
Volume2
Issue number2
DOIs
StatePublished - May 1 2011
Externally publishedYes

Keywords

  • Characterization
  • HIFU
  • Lesion size
  • MRI
  • Temperature
  • Thermal field

ASJC Scopus subject areas

  • Materials Science(all)
  • Electrical and Electronic Engineering

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