Bedside trans-burr hole dynamic contrast-enhanced ultrasound (DCE-US) and ultrasound localization microscopy (ULM) in relapsed glioblastoma - a retrospective comparative case series.

PURPOSE: Although contrast-enhanced ultrasound (CEUS) and dynamic CEUS (DCE-US) are well established in other oncologic entities, their use in neuro-oncology has been limited by the acoustic inaccessibility of the brain through the intact skull. This study investigates the feasibility of the use of DCE-US and ultrasound localization microscopy (ULM) in patients with glioblastoma multiforme (GBM), by utilizing the craniotomy burr hole as an acoustic window.

MATERIALS AND

METHODS

CEUS data from n=8 patients with newly diagnosed or relapsed GBM were retrospectively analyzed. All patients underwent CEUS via the craniotomy burr hole in the bedside setting, and perfusion analysis was conducted on stored cine loops. DCE-US parameters - time-to-peak (TTP), area under the curve (AUC), wash-in AUC, and washout AUC - were analyzed in three region-of-interest (ROI) zones: tumor center, margin, and adjacent normal brain. Next, ULM algorithms were applied to multiple frames to reconstruct the GBM tumor microvasculature.

RESULTS

Trans-burr hole imaging was feasible in all patients. Differences in TTP, AUC, washout AUC, and signal gradient were observed between the lesion center and both the margin and normal brain tissue, while the margin and the normal brain did not differ. Lesion-center AUC values were significantly higher in confirmed tumor recurrence (n=4) than in reactive gliosis (n=2). Recurrent tumors showed homogeneous, well-defined enhancement, whereas non-tumorous lesions appeared heterogeneous and ill-defined. ULM enabled quantification and visualization of directivity, velocity, and density maps corresponding to tumor anatomy and microbubble dynamics.

CONCLUSION

DCE-US and ULM via the post-surgical burr hole offer a promising, noninvasive tool for perfusion assessment and relapse evaluation in GBM follow-up.