PURPOSE: During MR-guided high-intensity focused ultrasound (HIFU) therapy, ultrasound absorption in the near field represents a safety risk and limits efficient energy deposition at the target. In this study, we investigated the feasibility of using T2 mapping to monitor the temperature change in subcutaneous adipose tissue layers. METHODS: The T2 temperature dependence and reversibility was determined for fresh adipose porcine samples. The accuracy was evaluated by comparing T2 -based temperature measurements with probe readings in an ex vivo HIFU experiment. The in vivo feasibility of T2 -based thermometry was studied during HIFU ablations in the liver in pigs and of uterine fibroids in human patients. RESULTS: T2 changed linearly and reversibly with temperature with an average coefficient of 5.2 ± 0.1 ms/°C. For the ex vivo HIFU experiment, the difference between the T2 -based temperature change and the probe temperature was <0.9°C. All in vivo experiments showed temperature-related T2 changes in the near field directly after sonications. As expected, considerable intersubject variations in the cooling times were measured in the in vivo porcine experiments. CONCLUSIONS: The reversibility and linearity of the T2 -temperature dependence of adipose tissue allows for the monitoring of the temperature in the subcutaneous adipose tissue layers.
PURPOSE: During MR-guided high-intensity focused ultrasound (HIFU) therapy, ultrasound absorption in the near field represents a safety risk and limits efficient energy deposition at the target. In this study, we investigated the feasibility of using T2 mapping to monitor the temperature change in subcutaneous adipose tissue layers. METHODS: The T2 temperature dependence and reversibility was determined for fresh adipose porcine samples. The accuracy was evaluated by comparing T2 -based temperature measurements with probe readings in an ex vivo HIFU experiment. The in vivo feasibility of T2 -based thermometry was studied during HIFU ablations in the liver in pigs and of uterine fibroids in humanpatients. RESULTS: T2 changed linearly and reversibly with temperature with an average coefficient of 5.2 ± 0.1 ms/°C. For the ex vivo HIFU experiment, the difference between the T2 -based temperature change and the probe temperature was <0.9°C. All in vivo experiments showed temperature-related T2 changes in the near field directly after sonications. As expected, considerable intersubject variations in the cooling times were measured in the in vivo porcine experiments. CONCLUSIONS: The reversibility and linearity of the T2 -temperature dependence of adipose tissue allows for the monitoring of the temperature in the subcutaneous adipose tissue layers.
Authors: Misung Han; Viola Rieke; Serena J Scott; Eugene Ozhinsky; Vasant A Salgaonkar; Peter D Jones; Peder E Z Larson; Chris J Diederich; Roland Krug Journal: Magn Reson Med Date: 2015-09-21 Impact factor: 4.668
Authors: Hans Weber; Pejman Ghanouni; Aurea Pascal-Tenorio; Kim Butts Pauly; Brian A Hargreaves Journal: Magn Reson Med Date: 2017-12-07 Impact factor: 4.668
Authors: Le Zhang; Alex Burant; Andrew McCallister; Victor Zhao; Karl M Koshlap; Simone Degan; Michael Antonacci; Rosa Tamara Branca Journal: Magn Reson Med Date: 2016-10-19 Impact factor: 4.668
Authors: Hans Weber; Valentina Taviani; Daehyun Yoon; Pejman Ghanouni; Kim Butts Pauly; Brian A Hargreaves Journal: Magn Reson Med Date: 2016-03-16 Impact factor: 4.668