183MR Susceptibility-Weighted Imaging (SWI) Complements Conventional Contrast Enhanced Imaging for Melanoma Gamma Knife Radiosurgery Planning
Section snippets
Purpose/Objectives
Detection of brain metastases from melanoma benefits from the sensitivity of susceptibility weighted imaging (SWI) to deoxyhemoglobin and melanin-related paramagnetic tissue effects. In some cases, SWI can clarify lesions difficult to diagnose primarily on MPRAGE due to hemorrhage and disruption. Though its imperfect spatial fidelity makes SWI alone unsuitable for radiosurgery planning, its extreme sensitivity to blood products suggests its utility as a qualitative aid for screening pts at the
Materials/Methods
8 pts with melanoma metastatic to the brain undergoing Gamma Knife radiosurgery underwent target imaging on a 3T MRI scanner. Axial SWI and double-dose, contrast-enhanced MPRAGE 3D data sets were obtained with the stereotactic localizer and coordinate frame. Both data sets were imported into Gamma Plan Version 9 and co-registered. Lesions on both imaging data sets were analyzed primarily using the SWI to screen for lesions that could be confirmed on MPRAGE images. The radiosurgery plan was
Results
11 procedures in 8 pts treated between 11/2011 and 8/2012 form this report. For each procedure, the mean number of lesions visualized on MPRAGE was 6.9 (1–28) and on SWI was 4.7 (1–21). Of the 76 total lesions identified by MPRAGE, SWI visualized 52 (68%) but failed to visualize 24 (32%) of the lesions. The SWI-identified lesions were more visible in 32 of 76 (42%) lesions. For 25 lesions, the greater visibility on SWI compared to MPRAGE was due to their larger imaging footprint (mean 223%
Conclusions
SWI sequences will identify a significant proportion of lesions also seen on conventional radiosurgery planning scans. Moreover, many (42%) of lesions are more visible on SWI than on the conventional planning sequences largely due to the lesions' larger imaging footprint but also their increased visibility on SWI. While SWI sequences alone are insufficient for radiosurgery planning, they can be a useful and complementary adjunct to conventional planning scans for pts with metastatic melanoma.
Author Disclosure Block
J.V. Kuo: None. J. Huang: None. M.E. Linskey: None.