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Towards MRI temperature mapping in real time-the proton resonance frequency method with undersampled radial MRI and nonlinear inverse reconstruction.

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Zhang,  Z.
Biomedical NMR Research GmbH, MPI for biophysical chemistry, Max Planck Society;

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Michaelis,  T.
Biomedical NMR Research GmbH, MPI for biophysical chemistry, Max Planck Society;

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Frahm,  J.
Biomedical NMR Research GmbH, MPI for biophysical chemistry, Max Planck Society;

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Citation

Zhang, Z., Michaelis, T., & Frahm, J. (2017). Towards MRI temperature mapping in real time-the proton resonance frequency method with undersampled radial MRI and nonlinear inverse reconstruction. Quantitative Imaging in Medicine and Surgery, 7(2), 251-258. doi:10.21037/qims.2017.03.03.


Cite as: http://hdl.handle.net/11858/00-001M-0000-002D-5A6F-B
Abstract
Background: Optimal control of minimally invasive interventions by hyperthermia requires dynamic temperature mapping at high temporal resolution. Methods: Based on the temperature-dependent shift of the proton resonance frequency (PRF), this work developed a method for real-time MRI thermometry which relies on highly undersampled radial FLASH MRI sequences with iterative image reconstruction by regularized nonlinear inversion (NLINV). As a first step, the method was validated with use of a temperature phantom and ex vivo organs (swine kidney) subjected to heating by warm water or a pulsed laser source. Results: The temperature maps obtained by real-time PRF MRI demonstrate good accuracy as independently controlled by fiber-optic temperature sensors. Moreover, the dynamic results demonstrate both excellent sensitivity to single laser pulses (20 ms duration, 6 J energy output) and high temporal resolution, i.e., 200 ms acquisition times per temperature map corresponding to a rate of 5 frames per second. In addition, future extensions to in vivo applications were prepared by addressing the breathingrelated motion problem by a pre-recorded library of reference images representative of all respiratory states. Conclusions: The proposed method for real-time MRI thermometry now warrants further developments towards in vivo MRI monitoring of thermal interventions in animals.