Intraoperative comparison between strain elastography and pre-operative MRI features in high-grade gliomas using fusion imaging: a pilot study

Objective: To compare the elastographic patterns of high-grade gliomas (HGGs) solid portions and those of adjacent healthy brain parenchyma, on intraoperative ultrasound, with magnetic resonance image (MRI) characteristics. Methods: Clinical records and images of HGGs patients, operated between June and December 2018, were retrospectively reviewed. Fusion images were used to compare preoperative gadolinium-enhanced T1-weighted MRI/fluid-attenuated inversion recovery images (Gd-T1 MRI/FLAIR) to intraoperative strain elastography (SE). FLAIR/Gd-T1 MRI images were used to define: enhancement patterns (absent/whole lesion/peripheral) and lesions' characteristics (primary and secondary pattern, further subdivided in solid/necrotic/cystic/infiltrating). HGGs SE patterns were categorized as homogeneous/inhomogeneous, while lesions' primary and secondary patterns as stiff/intermediate/elastic. The SE motive of neighboring healthy brain parenchyma was defined similarly. Results: 18 patients (M:F, 11:7; mean age: 53 years) harboring 14 glioblastomas (77.8%, GBMs) and 4 anaplastic astrocytomas (22.2%, AAs) were compared. GBMs typically enhanced peripherally and had a primary necrotic pattern (78.6% and 64.3%, respectively), while AAs did not enhance and were solid (75% both) at T1-Gd MRI and FLAIR images. At SE AAs had a homogeneous stiff primary pattern, whereas the majority of GBMs primary patterns were heterogeneous (85.7%) and intermediate (78.6%). Conclusions: Three major SE patterns defined HGGs and adjacent healthy brain parenchyma. SE patterns varied accordingly to HGG histotypes and Gd-T1 MRI/FLAIR characteristics.