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 radiofrequenc y (RF) thermal liver lesions and surrounding tissue In T2-weighted turbo sp in-echo sequences (TSE T2), short T1 inversion recovery techniques (STIR), and contrast-enhanced (CE) T1-weighted spin-echo images. Nineteen RF therma l ablations were performed on eight patients with metastatic liver tumors. After ablation, contrast-to-noise ratios (CNRs) were calculated between mea n signal amplitudes from three regions of interest (ROI) (lesion, surroundi ng edema, and normal tissue) using TSE T2-weighted, STIR, and contrast-enha nced T1-weighted (CE T1) sequences for each lesion. CNRs between the therma l lesion and normal liver tissue for both TSE T2-weighted (mean 0.9) and ST IR (2.0) Images were significantly lower than for CE T1-weighted (8.4) Imag es (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) wer e not significantly different (t-test, a = 0.05) from CNRs between lesion a nd normal tissue for CE T1-weighted images (8.4), nor was the CNR between e dema rim and normal tissue for both TSE T2-weighted (10.3) and STIR (9.8) I mages. Although the edema was not visible on CE TI-weighted images, 18 of 1 9 lesions (94.7%) were surrounded by a hyperintense rim on TSE T2-weighted or STIR images. Both TSE T2-weighted and STIR sequences represent valid tec hniques for repeatable assessment of RF thermal lesions. J. Magn. Reson. Im aging 2000; 12:584-589. (C) 2000 Wiley-Liss, Inc.