LAUSR

Simple Summary Reliable insight into tumor microvasculature is important for monitoring disease progression and treatment response. Vessel size imaging (VSI), an emerging MRI technique, has shown great potential in revealing accurate information about microvasculature in gliomas. However, the technique has rarely been used in the clinical setting, as investigated here. Of note, our work was only aimed at non-enhancing tumors. This sets our work apart from other studies investigating tumor microvasculature, typically including enhancing tumors, i.e., tumors in which angiogenesis is already evident macroscopically. Additionally, our findings are of potential clinical relevance for differentiating the most aggressive tumor subtype, glioblastoma, from two other glioma subtypes: oligodendroglioma and astrocytoma. This is particularly challenging when there is no contrast enhancement. Abstract In this study, we used the vessel size imaging (VSI) MRI technique to characterize the microvasculature features of three subtypes of adult-type diffuse glioma lacking enhancement. Thirty-eight patients with confirmed non-enhancing glioma were categorized into three subtypes: Oligo (IDH-mut&1p/19q-codeleted), Astro (IDH-mut), and GBM (IDH-wt). The VSI technique provided quantitative maps of cerebral blood volume (CBV), microvasculature (µCBV), and vessel size for each patient. Additionally, tissue samples of 21 patients were histopathologically analyzed, and microvasculature features were quantified. Both MRI- and histology-derived features were compared across the three glioma subtypes with ANOVA or Kruskal–Wallis tests. Group averages of CBV, μCBV, and vessel size were significantly different between the three glioma subtypes (p < 0.01). Astro (IDH-mut) had a significantly lower CBV and µCBV compared to Oligo (IDH-mut&1p/19q-codeleted) (p = 0.004 and p = 0.001, respectively), and a higher average vessel size compared to GBM (IDH-wt) (p = 0.01). The histopathological analysis showed that GBM (IDH-wt) possessed vessels with more irregular shapes than the two other subtypes (p < 0.05). VSI provides a good insight into the microvasculature characteristics of the three adult-type glioma subtypes even when lacking enhancement. Further investigations into the specificity of VSI to differentiate glioma subtypes are thus warranted.