The enhancing component of the left parietal tumour has reduced in size. The punctate foci of subependymal enhancement and the expansile T2 hyperintensity along the splenium of the corpus callosum are unchanged. The previously seen vasogenic oedema surrounding the tumour has markedly improved.
The tumour again demonstrates a rim of low ADC values, with persistently elevated cerebral blood volume. MR spectroscopy again demonstrates markedly elevated choline within the enhancing tumour and moderately elevated choline in the non-enhancing T2 hyperintense region. Of note, there is also elevated choline in the regions that are no longer T2 hyperintense.
Small areas of blood product (intrinsic high T1 signal).
Conclusion: The reduction of vasogenic oedema and enhancement is likely due to bevacizumab-mediated change in blood-brain barrier permeability. The actual size of the viable tumour (based on the diffusion imaging, perfusion characteristics, and spectroscopy finding) has only modestly reduced. Overall, appearances are dominated by pseudoresponse.