Thermal lesion conspicuity following interstitial radiofrequency thermal tumor ablation in humans: A comparison of STIR, turbo spin-echo T2-weighted,and contrast-enhanced T1-weighted MR images at 0.2 T

The purpose of this study was to, compare the contrast between radiofrequen cy (RF) thermal liver lesions and surrounding tissue in T2-weighted turbo s pin-echo sequences (TSE T2), short TI inversion recovery techniques (STIR), and contrast-enhanced (CE); TI-weighted spin-echo images. Nineteen RF ther mal ablations were performed on eight patients with metastatic liver tumors . After ablation, contrast-to-noise ratios (CNRs) were calculated between m ean signal amplitudes from three regions of interest (ROI) (lesion, surroun ding edema, and normal tissue) using TSE T2-weighted, STIR, and contrast-en hanced T1-weighted (CR T1) sequences for each lesion. CNRs between the ther mal lesion and normal liver tissue for both TSE T2-weighted (mean 0.9) and STIR (2.0) images were significantly lower than for CE T1-weighted (8.4) im ages, (t-test, alpha = 0.05). However, CNRs between edema rim and the core of the thermal lesion for both TSE T2-weighted (8.1) and STIR images (7.2) were not significantly different (t-test, a = 0.05) from CNRs between lesio n and normal tissue for CE T1-weighted images (8.4), nor was the CNR betwee n edema rim and normal tissue for both TSR T2-weighted (10.3) and STIR (9.8 ) images. Although the edema was not visible on CE T1-weighted Images, 18 o f 19 lesions (94.7%) were surrounded by a hyperintense rim on TSE T2-weight ed or STIR images. Both TSE T2-weighted and STIR sequences represent valid techniques for repeatable assessment of RF thermal lesions. (C) 2000 Wiley- Liss, Inc.