Guojun Xu1,2, Zhiyong Zhao1,3,2, Kedi Xu4,5, Junming Zhu6, Anna W Roe7, Bin Xu7, Xiaotong Zhang7, Jianqi Li8, Dongrong Xu9. 1. Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai, 200062, China. 2. Molecular Imaging and Neuropathology Division, Columbia University Department of Psychiatry and New York State Psychiatric Institute, 1051 Riverside Drive, Unit 42, New York, NY, 10032, USA. 3. Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, 310027, China. 4. Qiushi Academy for Advanced Studies (QAAS), Zhejiang University, Hangzhou, 310027, China. 5. Department of Biomedical Engineering, Key Laboratory of Biomedical Engineering of Education Ministry, Zhejiang University, Hangzhou, China. 6. Neurosurgery Department, The Second Affiliated Hospital of Zhejiang University, Hangzhou, 310006, China. 7. Interdisciplinary Institute of Neuroscience and Technology, Qiushi Academy for Advanced Studies, Zhejiang University, Hangzhou, 310029, China. 8. Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai, 200062, China. jqli@phy.ecnu.edu.cn. 9. Molecular Imaging and Neuropathology Division, Columbia University Department of Psychiatry and New York State Psychiatric Institute, 1051 Riverside Drive, Unit 42, New York, NY, 10032, USA. dx2103@columbia.edu.
Abstract
PURPOSE: The present study aimed to evaluate magnetic resonance (MR) thermometry using proton resonance frequency shift (PRFS) during laser-induced thermotherapy (LITT), and to compare the results of using different sequences at a field strength of 7-Tesla to identify the optimal for use in ablation so that the surrounding healthy tissues may be protected from damaging in real time. MATERIALS AND METHODS: LITT was applied to agarose gel phantoms and ex-vivo porcine brains. We reconstructed both magnitude and phase images to perform MR thermometry based on PRFS methods. We tested four different sequences: a gradient-echo (GRE), a segmented gradient-echo echoplanar imaging (EPI-GRE), a fast-low angle shot (FLASH), and a true fast imaging with steady precession (TRUFI). Temperature was monitored and verified using a fiber-optic thermometry device. RESULTS: All sequences showed good linear correlations (R = 0.97-0.99) between the measured temperature and the calculated MR-thermometry measurements. The phantom/porcine brain experiments revealed the temperature precisions at 1.53/0.69 °C (GRE), 0.61/0.43 °C (EPI-GRE), 1.64/1.32 °C (FLASH), and 0.58/1.52 °C (TRUFI), respectively. Furthermore, we performed a Bland-Altman analysis and the temperature accuracies were found to be - 1.32/- 0.60 °C (GRE), 0.42/- 0.33 °C (EPI-GRE), - 1.28/- 0.98 °C (FLASH), and 0.14/0.46 °C (TRUFI) in the phantom/porcine brain experiments, respectively. CONCLUSIONS: Our experiments recommend that EPI-GRE sequence be the best of the all sequences for MR temperature imaging with PRFS in the LITT on 7 T magnetic resonance imaging (MRI) systems because of its relatively higher precision and accuracy.
PURPOSE: The present study aimed to evaluate magnetic resonance (MR) thermometry using proton resonance frequency shift (PRFS) during laser-induced thermotherapy (LITT), and to compare the results of using different sequences at a field strength of 7-Tesla to identify the optimal for use in ablation so that the surrounding healthy tissues may be protected from damaging in real time. MATERIALS AND METHODS: LITT was applied to agarose gel phantoms and ex-vivo porcine brains. We reconstructed both magnitude and phase images to perform MR thermometry based on PRFS methods. We tested four different sequences: a gradient-echo (GRE), a segmented gradient-echo echoplanar imaging (EPI-GRE), a fast-low angle shot (FLASH), and a true fast imaging with steady precession (TRUFI). Temperature was monitored and verified using a fiber-optic thermometry device. RESULTS: All sequences showed good linear correlations (R = 0.97-0.99) between the measured temperature and the calculated MR-thermometry measurements. The phantom/porcine brain experiments revealed the temperature precisions at 1.53/0.69 °C (GRE), 0.61/0.43 °C (EPI-GRE), 1.64/1.32 °C (FLASH), and 0.58/1.52 °C (TRUFI), respectively. Furthermore, we performed a Bland-Altman analysis and the temperature accuracies were found to be - 1.32/- 0.60 °C (GRE), 0.42/- 0.33 °C (EPI-GRE), - 1.28/- 0.98 °C (FLASH), and 0.14/0.46 °C (TRUFI) in the phantom/porcine brain experiments, respectively. CONCLUSIONS: Our experiments recommend that EPI-GRE sequence be the best of the all sequences for MR temperature imaging with PRFS in the LITT on 7 T magnetic resonance imaging (MRI) systems because of its relatively higher precision and accuracy.
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