• Elizabeth A Dick, Paul Wragg, Rita Joarder, Michael de Jode, Gabrielle Lamb, Stuart Gould, and Wladyslaw M W Gedroyc.
• Department of Interventional MRI, St. Mary's Hospital, Imperial College of Science, Technology and Medicine, Praed Street, London W2 1NY, UK.
• J Magn Reson Imaging. 2003 Feb 1; 17 (2): 197-205.

PurposeTo prove the hypothesis that T1-weighted (T1W) thermal mapping is reliable and achievable in magnetic resonance (MR)-guided laser tumor ablation.Materials And MethodsNear real-time gray and color-scale T1W thermal maps in 111 MR-guided laser thermal ablations (LTA) of liver, kidney, and uterine tumors were studied. After laser fiber placement, near real-time gray and color-scale thermal maps were produced. Previous work showed T1 signal is inversely proportional to temperature below 55 degrees C (the point of irreversible necrosis).ResultsThermal mapping was successful in 84% of uterine, 74% of hepatic, and 20% of renal ablations. For hepatic and uterine tumors, size and conspicuity of thermal lesions were significantly greater on subtracted colorized images rather than gray-scale raw image mapping (P = 0.001, paired Student's t-test). Patient movement (N = 24), fiber charring N = 2), magnetic field distortion, and reconstruction errors (N = 2) caused mapping failure. For both renal and hepatic tumors, comparison of near real-time T1W colorized thermal map and follow up gadolinium-enhanced MR imaging revealed moderate correlation (Pearson correlation coefficient of 0.55 and 0.5, respectively).ConclusionIn hepatic, renal, and uterine thermal maps, the color scale produced significantly greater sized lesions with significantly greater conspicuity than the gray scale. T1W thermal mapping was reliable and successfully achieved in 73.7% of procedures, and predicted the ablated area of the tumor moderately well.Copyright 2003 Wiley-Liss, Inc.

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