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 T-1-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. Wedemonstrated MRFT's feasibility in predicting temperature on ex vivo bovine muscles with deep brain stimulation (DBS) lead. B-0 maps generated from MRFT were compared with gold standard B-0 maps near the DBS lead. MRFT and PRFS estimated temperatures were compared in the presence of motion. All experiments were performed on a 3 Tesla whole-body GE Premier system 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 T-1 maps and Delta s maps to temperature maps. Wethen repeated the same setup and compared MRFT and 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 sequence to induce heating near the lead. We selected ROIs around the tip of the lead to compare MRFT temperature estimation with probe measurements and compared with PRFS temperature estimation. Vendor supplied B-0 mapping sequence was acquired to compare with MRFT-generated B-0 maps. We found strong linear relationships (R-2> 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 B-0 maps show inhomogeneities around the lead. MRFT estimated temperature is less sensitive to motion.

Automated summary

The study aims to demonstrate the first application of T-1-based magnetic resonance thermometry using magnetic resonance fingerprinting (MRFT). The temperature estimation of MRFT is compared with proton resonance frequency shift (PRFS) thermometry on ex vivo bovine muscle. The feasibility of MRFT in predicting temperature on ex vivo bovine muscles with deep brain stimulation (DBS) lead is shown.