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Sub‐acute changes in lesion conspicuity and geometry following MR‐guided radiofrequency ablation
Author(s) -
Lazebnik Roee S.,
Weinberg Brent D.,
Breen Michael S.,
Lewin Jonathan S.,
Wilson David L.
Publication year - 2003
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.10352
Subject(s) - nuclear medicine , medicine , lesion , magnetic resonance imaging , contrast to noise ratio , anatomy , geometry , radiology , mathematics , pathology , image quality , image (mathematics) , artificial intelligence , computer science
Purpose To evaluate MR signal and lesion zone volume evolution through the sub‐acute phase following image‐guided radiofrequency (RF) thermal ablation. Materials and Methods For many tissues, including muscle and liver, thermal lesions that result from RF heating have a characteristic two‐boundary appearance featuring an inner core (zone I) surrounded by a hyper‐intense margin (zone II) and normal tissue (zone III), found in both T 2 and contrast enhanced (CE) T 1 ‐weighted MR images, both immediately post‐ablation and four days later. First, we compared corresponding points between manually segmented zone boundaries apparent in T 2 ‐ and CE T 1 ‐weighted images. Second, we examined the contrast‐to‐noise ratio (CNR) between all zone combinations. Third, we quantified the volume of zone I, zone II, and the entire lesion using a three‐dimensional lesion geometry model fitted to segmented images. Results On a slice‐by‐slice basis, no statistically significant differences were found between zone boundaries apparent in T 2 and CE T 1 ‐weighted images. The contrast to noise ratio (CNR) of zone I vs. zone II, zone I vs. background muscle, and zone II vs. background muscle was always equal or greater for T 2 ‐weighted images than for CE T 1 ‐weighted images. In addition, by day four, zone II significantly increased in intensity compared to background muscle. The median Zone I volume increase was 44.2% (42.6%) using T 2 weighted images and 55.5% (68.7% interquartile range) using CE T 1 ‐ weighted images. This expansion likely corresponds to an enlargement of the ablated, coagulative necrosis, region. The median Zone II volume increase was 15.0% (42.6%) using T 2 ‐ weighted images 1.5% (38.8%) using CE T 1 ‐weighted images. Conclusions 1) There are no significant differences between the apparent zone boundaries in T 2 ‐ and CE T 1 ‐weighted images; 2) CNR is equal or greater for T 2 ‐weighted images as compared to CE T 1 ‐images; and 3) both the inner and outer lesion zone volumes typically increase several days post‐ablation. J. Magn. Reson. Imaging 2003;18:353–359. © 2003 Wiley‐Liss, Inc.