ESTRO 2024 - Abstract Book

S905

Clinical - CNS

ESTRO 2024

Figure 1: Comparison of MRI characteristic volume calculations, on T1c and T2 fused sequences, using linear measurement method and 3-dimensional volumetric contour method. T1c measurements and volumes depicted in green, T2hypo in purple and T2hyper in red.

Results:

Thirty-four lesions were identified in 24 patients from a total of 279 lesions treated with SRS over the study period. There were 13 cases of exclusive RN, 4 cases of exclusive TR, and 15 cases of mixed pathology. Two samples from 1 patient were excluded due to a subsequent diagnosis as a primary brain tumour. The lesion quotient (T2hypo:T1c) was found to have a statistically significant difference between cases of exclusive RN or mixed pathology compared to exclusive TR, whereby a low ratio value suggestive of RN or mixed pathology. This difference was seen in both the linear measurement and 3D volumetric methods. All cases of exclusive RN had a value below 0.2, however some cases of exclusive TR or mixed pathology were also below this value. For exclusive RN compared to the groups with any element of TR, a lesion quotient of less than 0.2 has a sensitivity of 100 percent for RN using both the methods, and the specificity of only 19 percent and 21 percent for 3D volumetric and simple linear measurement methods, respectively. There was no statistically significant difference in lesion matching or oedema ratio between RN, TR, or mixed pathology in our cohort.