Focused ultrasound induced-blood-brain barrier opening in mouse brain receiving radiosurgery dose of radiation enhances local delivery of systemic therapy.

Investigate the temporal effects of focused ultrasound (FUS) induced blood-brain barrier (BBB) opening in post-radiotherapy mouse brains.
C57B6 mice without tumors were used to simulate the scenario after gross total resection (GTR) of brain tumor. Radiation dose of 6 Gy x five was delivered to one-hemisphere of the mouse brain. FUS-induced BBB-opening was delivered to the irradiated and non-irradiated brain and was confirmed with MRI. Dynamic MRI was performed to evaluate blood vessel permeability. Two time points were selected: acute (2 days after radiation) and chronic (31 days after radiation).
BBB opening was achieved after FUS in the irradiated field as compared to the contralateral non-irradiated brain without any decrease in permeability. In the acute group, a trend for higher gadolinium concentration was observed in radiated field.
Localized BBB-opening can be successfully achieved without loss of efficacy by FUS as early as 2 days after radiotherapy.
Adjuvant radiation after GTR is commonly used for brain tumors. Focused ultrasound facilitated BBB-opening can be achieved without loss of efficacy in the post-irradiated brain as early as 2 days after RT. This allows for further studies on early application of FUS-mediated BBB-opening.