Hyperacute thermal lesions: MR imaging evaluation of development in the brain.

Abstract

To determine the natural time course of development of hyperacute thermal lesions in the brain. Ten interstitial lesions were created in five rabbit brains with a radio-frequency probe; an electrode-tip temperature of 80 degrees C was maintained for 60 seconds. Continuous fast spin-echo magnetic resonance (MR) imaging was used to follow lesion development for a minimum of 30 minutes. Temporal variations in lesion size and signal intensity were examined. Findings in final images were correlated with histologic findings. Images demonstrated a focal hyperintense zone, which developed into an expanding ring of edema surrounding a necrotic center in about 10 minutes. Quantitative analysis revealed a 23% +/- 6 (standard deviation) increase in average signal intensity of the edema layer and a 152% +/- 41 increase in overall lesion size. Full development of a thermal lesion is delayed for a period of minutes. Clinical implications of this effect should be considered when MR imaging-guided thermal ablation is performed.