Temperature Mapping During MR-Guided Cryoablation Using a FLORET UTE Sequence

Motivation: Frozen tissue has a rapid T2* decay and low net magnetization. It thus appears as a signal void in most MR images. As tissue necrosis only happens between -20 and -40 °C it is not possible to distinguish between frozen and necrotic tissue during MR-guided cryoablation. Goal(s): Our goal was to estimate temperatures in frozen tissue. Approach: To encounter the rapid T2* decay we implemented an ultrashort echo-time sequence with a FLORET readout and estimated the temperature from the signal intensity. Results: Our method provided a good temperature accuracy combined with a high temporal resolution. Impact: During MR-guided cryoablation of tumors the proposed method could be used for therapy monitoring. It could thus enable a safer and more targeted way of destroying the tumor but not too much of the surrounding healthy tissue.