Clinical evaluation of MR temperature monitoring of laser-induced thermotherapy in human liver using the proton-resonance-frequency method and predictive models of cell death

Purpose: To assess the feasibility, precision, and accuracy of real‐time temperature mapping (TMap) during laser‐induced thermotherapy (LITT) for clinical practice in patients liver with a gradient echo (GRE) sequence using the proton resonance frequency (PRF) method. Materials and Methods: LITT was performed on 34 lesions in 18 patients with simultaneous real‐time visualization of relative temperature changes. Correlative contrast‐enhanced T1‐weighted magnetic resonance (MR) images of the liver were acquired after treatment using the same slice positions and angulations as TMap images acquired during LITT. For each slice, TMap and follow‐up images were registered for comparison. Afterwards, segmentation based on temperature (T) >52°C on TMap and based on necrosis seen on follow‐up images was performed. These segmented structures were overlaid and divided into zones where the TMap was found to either over‐ or underestimate necrosis on the postcontrast images. Regions with T>52°C after 20 minutes were defined as necrotic tissue based on data received from two different thermal dose models. Results: The average intersecting region of TMap and necrotic zone was 87% ± 5%, the overestimated 13% ± 4%, and the underestimated 13% ± 5%. Conclusion: This study demonstrates that MR temperature mapping appears reasonably capable of predicting tissue necrosis on the basis of indicating regions having greater temperatures than 52°C and could be used to monitor and adjust the thermal therapy appropriately during treatment. J. Magn. Reson. Imaging 2011;33:704–712. © 2011 Wiley‐Liss, Inc.