Fast MR thermometry using an echo-shifted sequence with simultaneous multi-slice imaging
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Real-time monitoring is important for the safety and effectiveness of high-intensity focused ultrasound (HIFU) therapy. Magnetic resonance imaging is the preferred imaging modality for HIFU monitoring, with its unique capability of temperature imaging. For real-time temperature imaging, higher temporal resolution and larger spatial coverage are needed. In this study, a sequence based on the echo-shifted RF-spoiled gradient echo (GRE) with simultaneous multi-slice (SMS) imaging was designed for fast temperature imaging.
A phantom experiment was conducted to evaluate the accuracy of the echo-shifted sequence using a fluorescent fiber thermometer as reference. The temperature uncertainty of the echo-shifted sequence was compared with the traditional GRE sequence at room temperature through the ex vivo porcine muscle. Finally, the ex vivo porcine liver tissue experiment using HIFU heating was performed to demonstrate that the spatial coverage was increased without decreasing temporal resolution.
The echo-shifted sequence had a better temperature uncertainty performance compared with the traditional GRE sequence with the same temporal resolution. The ex vivo heating experiment confirmed that by combining the SMS technique and echo-shifted sequence, the spatial coverage was increased without decreasing the temporal resolution while maintaining high temperature measurement precision.
The proposed technique was validated as an effective real-time method for monitoring HIFU therapy.
KeywordsMagnetic resonance imaging Thermometry Simultaneous multi-slice imaging Echo-shifted sequence
This work was supported by the Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province (no. 2014B030301013), the National Natural Science Foundation (nos. 81327801, 81527901, 11574039, and 11504401), and the Shenzhen Science and Technology Research Program (nos. JCYJ20150630114942317 and JCYJ20150521094519487). The authors sincerely thank Jianhong Wen, De Meng, Chao Wang, and Zongwei Xu for their technical support in the experiments.
YP: protocol development, data collection, and analysis. CZ: sequence design test, protocol development, and data analysis. YQ: data analysis. CT and QW: data collection and analysis. RJ: data collection or management. CC: data analysis. DL: data analysis. HZ: data analysis. FL: protocol development and data analysis. XL: protocol development and data analysis.
Compliance with ethical standards
Conflict of interest
All authors declare that they have no conflicts of interest.
The study was performed in compliance with ethical standards.
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