1. Correction of motion-induced susceptibility artifacts and B0 drift during proton resonance frequency shift-based MR thermometry in the pelvis with background field removal methods
- Author
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Hendrik Thijmen Mulder, Paul Baron, Mingming Wu, Gerard C. van Rhoon, Eduardo Coello, Marion I. Menzel, Axel Haase, Radiotherapy, and Radiology & Nuclear Medicine
- Subjects
Materials science ,Full Papers—Imaging Methodology ,Phase (waves) ,Context (language use) ,Thermometry ,Imaging phantom ,susceptibility ,030218 nuclear medicine & medical imaging ,Pelvis ,03 medical and health sciences ,0302 clinical medicine ,Nuclear magnetic resonance ,Region of interest ,motion ,Dielectric heating ,Humans ,Radiology, Nuclear Medicine and imaging ,background field removal ,MR thermometry ,Artifact (error) ,Full Paper ,hyperthermia ,Magnetic Resonance Imaging ,ddc ,Body region ,Radio frequency ,B0 drift ,Protons ,Artifacts ,030217 neurology & neurosurgery - Abstract
Purpose The linear change of the water proton resonance frequency shift (PRFS) with temperature is used to monitor temperature change based on the temporal difference of image phase. Here, the effect of motion-induced susceptibility artifacts on the phase difference was studied in the context of mild radio frequency hyperthermia in the pelvis. Methods First, the respiratory-induced field variations were disentangled from digestive gas motion in the pelvis. The projection onto dipole fields (PDF) as well as the Laplacian boundary value (LBV) algorithm were applied on the phase difference data to eliminate motion-induced susceptibility artifacts. Both background field removal (BFR) algorithms were studied using simulations of susceptibility artifacts, a phantom heating experiment, and volunteer and patient heating data. Results Respiratory-induced field variations were negligible in the presence of the filled water bolus. Even though LBV and PDF showed comparable results for most data, LBV seemed more robust in our data sets. Some data sets suggested that PDF tends to overestimate the background field, thus removing phase attributed to temperature. The BFR methods even corrected for susceptibility variations induced by a subvoxel displacement of the phantom. The method yielded successful artifact correction in 2 out of 4 patient treatment data sets during the entire treatment duration of mild RF heating of cervical cancer. The heating pattern corresponded well with temperature probe data. Conclusion The application of background field removal methods in PRFS-based MR thermometry has great potential in various heating applications and body regions to reduce motion-induced susceptibility artifacts that originate outside the region of interest, while conserving temperature-induced PRFS. In addition, BFR automatically removes up to a first-order spatial B0 drift.
- Published
- 2020