Magnetic Resonance Fingerprinting based Thermometry (MRFT): application to ex vivo imaging near DBS leads
The purpose of this study is to demonstrate the first work of T1-based magnetic resonance thermometry using magnetic resonance fingerprinting (dubbed MRFT). We compared temperature estimation of MRFT with proton resonance frequency shift (PRFS) thermometry on ex vivo bovine muscle. We demonstrated MRFTs feasibility in predicting temperature on ex vivo bovine muscles with deep brain stimulation (DBS) lead. B0 maps generated from MRFT were compared with gold standard B0 maps near the DBS lead. All experiments were performed on a 3 Tesla whole-body GE Premier system equipped with a 21-channel receive head coil (GE Healthcare, Milwaukee, WI). Four fluoroptic probes were used to measure the temperature at the center of a cold muscle (probe 1), the room temperature water bottle (probe 2), and the center and periphery of the heated muscle (probes 3 and 4). We selected regions of interest (ROIs) around the location of the probes and used simple linear regression to generate the temperature sensitivity calibration equations that convert T1 maps and {Delta}s maps to temperature maps. We then repeated the same setup and compared MRFT, PRFS thermometry temperature estimation with gold standard probe measurements. For the MRFT experiment on DBS lead, we taped the probe to the tip of the DBS lead and used a turbo spin echo (TSE) sequence to induce heating near the lead. We selected ROIs around the tip of the lead to compare MRFT temperature estimation with probe measurements. Vendor-supplied B0 mapping sequence was acquired to compare with MRFT-generated B0 maps. We found strong linear relationships (R2>0.958) between T1 and temperature and {Delta}s and temperatures in our temperature sensitivity calibration experiment. MRFT and PRFS thermometry both accurately predict temperature (RMSE<1.55 {degrees}C) compared to probe measurements. MRFT estimated temperature near DBS lead has a similar trend as the probe temperature. Both B0 maps show inhomogeneities around the lead.