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- Title
Temperature imaging of laser-induced thermotherapy (LITT) by MRI: evaluation of different sequences in phantom.
- Authors
Bazrafshan, Babak; Hübner, Frank; Farshid, Parviz; Hammerstingl, Renate; Paul, Jijo; Vogel, Vitali; Mäntele, Werner; Vogl, Thomas
- 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 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 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 (EPI), −1.15 ± 0.03 °C (FLASH), −1.49 ± 0.03 °C (IRTF), −1.21 ± 0.03 °C (SRTF), and −2.52 ± 0.12 °C (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 method sequences, FLASH showed the highest accuracy and robustness.
- Subjects
MEDICAL imaging systems; THERMOTHERAPY; MEDICAL lasers; PROTON magnetic resonance; FIBER optics; PHYSICAL therapy; MEDICAL radiology
- Publication
Lasers in Medical Science, 2014, Vol 29, Issue 1, p173
- ISSN
0268-8921
- Publication type
Academic Journal
- DOI
10.1007/s10103-013-1306-5