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MR temperature mapping of focused ultrasound surgery
Author(s) -
Cline Harvey E.,
Hynynen Kullervo,
Hardy Christopher J.,
Watkins Ronald D.,
Schenck John F.,
Jolesz Ferenc A.
Publication year - 1994
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910310608
Subject(s) - transducer , thermal diffusivity , ultrasound , materials science , biomedical engineering , temperature gradient , magnetic resonance imaging , ultrasonic sensor , nuclear magnetic resonance , acoustics , physics , radiology , medicine , quantum mechanics
Deep lying soft tissue tumors may be treated by a nonincisional surgical procedure executed inside an MR imaging system using a thermal effect delivered by a focused ultrasound transducer. A prototype system is constructed to assess MRI thermal monitoring and the localization of the heat zone in muscle. The temperature distribution of the focal spot is imaged with MRI while mechanically moving the transducer with an hydraulic 3‐axis positioner. Acoustic power is applied with a spherical shell transducer using 1‐ to 10‐s duration pulses at frequencies of 1.5 MHz to selectively coagulate tissue at 60‐70°C. The procedure is monitored with a series of fast second gradient echo, T 1 ‐weighted, temperature sensitive MR sequences. Acquisitions are optimized for high temperature sensitive images that yield the thermal diffusivity, heat flow time constant and the focal spot size in muscle. MR temperature maps of muscle provide localization and dosimetry both in the focal region and near field.