title: Temperature imaging of laser-induced thermotherapy (LITT) by MRI: evaluation of different sequences in phantom.
abstract: The purpose of this study was to evaluate magnetic resonance (MR) temperature imaging of the laser-induced thermotherapy (LITT) comparing the proton resonance frequency (PRF) and T 1 thermometry methods. LITT was applied to a liver-mimicking acrylamide gel phantom. Temperature rise up to 70 °C was measured using a MR-compatible fiber-optic thermometer. MR imaging was performed by a 1.5-T scanner utilizing fast gradient echo sequences including a segmented echo planar imaging (seg-EPI) sequence for PRF and the following sequences for T 1 method: fast low-angle shot (FLASH), inversion recovery turbo flash (IRTF), saturation recovery turbo flash (SRTF), and true fast imaging (TRUFI). Temperature-induced change of the pixel values in circular regions of interest, selected on images under the temperature probe tip, was recorded. For each sequence, a calibration constant could be determined to be -0.0088 ± 0.0002 ppm °C(-1) (EPI), -1.15 ± 0.03 °C(-1) (FLASH), -1.49 ± 0.03 °C(-1) (IRTF), -1.21 ± 0.03 °C(-1) (SRTF), and -2.52 ± 0.12 °C(-1) (TRUFI). These constants were evaluated in further LITT experiments in phantom comparing the calculated temperatures with the fiber optic-measured ones; temperature precisions of 0.60 °C (EPI), 0.81 °C (FLASH), 1.85 °C (IRTF), 1.95 °C (SRTF), and 3.36 °C (TRUFI) were obtained. Furthermore, performing the Bland-Altman analysis, temperature accuracy was determined to be 0.23 °C (EPI), 0.31 °C (FLASH), 1.66 °C (IRTF), 1.19 °C (SRTF), and 3.20 °C (TRUFI). In conclusion, the seg-EPI sequence was found to be more convenient for MR temperature imaging of LITT due to its relatively high precision and accuracy. Among the T 1 method sequences, FLASH showed the highest accuracy and robustness.
authors.affiliation: Institute for Diagnostic and Interventional Radiology, J.W. Goethe-University Hospital, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany, babak.bazrafshan@kgu.de.
authors.forename: Babak
authors.initials: B
authors.lastname: Bazrafshan
authors.forename: Frank
authors.initials: F
authors.lastname: Hübner
authors.forename: Parviz
authors.initials: P
authors.lastname: Farshid
authors.forename: Renate
authors.initials: R
authors.lastname: Hammerstingl
authors.forename: Jijo
authors.initials: J
authors.lastname: Paul
authors.forename: Vitali
authors.initials: V
authors.lastname: Vogel
authors.forename: Werner
authors.initials: W
authors.lastname: Mäntele
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Vogl
mesh_terms: D000818:Animals; D005336:Fiber Optic Technology; D005782:Gels; D006801:Humans; D006979:Hyperthermia, Induced / Q000379:methods*; D053685:Laser Therapy / Q000379:methods*; D008099:Liver / Q000601:surgery; D008113:Liver Neoplasms / Q000556:secondary / Q000628:therapy; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D008954:Models, Biological; D019047:Phantoms, Imaging; D034421:Sus scrofa; D013696:Temperature; D013817:Thermography / Q000379:methods* / Q000706:statistics & numerical data
chemical_list: D005782:Gels
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