Abstract
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 1) surrounded by a hyper-intense margin (zone II) and normal tissue (zone III), found in both T2 and contrast enhanced (CE) T1-weighted MR images, both immediately post-ablation and four days later. First, we compared corresponding points between manually segmented zone boundaries apparent in T2- and CE T1-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 T2 and CE T1-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 T2-weighted images than for CE T1-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 T2 weighted images and 55.5% (68.7% inter-quartile range) using CE T1-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 T2-weighted images 1.5% (38.80%) using CE T 1-weighted images. Conclusions: 1) There are no significant differences between the apparent zone boundaries in T2- and CE T 1-weighted images; 2) CNR is equal or greater for T 2-weighted images as compared to CE T1-images; and 3) both the inner and outer lesion zone volumes typically increase several days post-ablation.
Original language | English (US) |
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Pages (from-to) | 353-359 |
Number of pages | 7 |
Journal | Journal of Magnetic Resonance Imaging |
Volume | 18 |
Issue number | 3 |
DOIs | |
State | Published - Sep 1 2003 |
Externally published | Yes |
Keywords
- Contrast enhanced T-weighted images
- Image analysis
- Interventional magnetic resonance imaging
- Medical image processing
- Radiofrequency thermal ablation
- Segmentation
- T-weighted images
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging