Evaluation of the increase in permeability of the blood–brain barrier during tumor progression after pulsed focused ultrasound

Feng-Yi Yang¹,*, Hsin-Ell Wang¹,*, Guan-Liang Lin¹, Hui-Hsien Lin¹, Tai-Tong Wong<sup>2

1</sup>Department of Biomedical Imaging and Radiological Sciences, School of Biomedical Science and Engineering, National Yang-Ming University, ²Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan
*These authors contributed equally to this work

Purpose: The purpose of this study was to evaluate the permeability of the blood–brain barrier after sonication by pulsed high-intensity focused ultrasound and to determine if such an approach increases the tumor:ipsilateral brain permeability ratio.
Materials and methods: F98 glioma-bearing Fischer 344 rats were injected intravenously with Evans blue with or without blood–tumor barrier disruption induced by transcranial pulsed high-intensity focused ultrasound. Sonication was applied at a frequency of 1 MHz with a 5% duty cycle and a repetition frequency of 1 Hz. The permeability of the blood–brain barrier was assessed by the extravasation of Evans blue. Contrast-enhanced magnetic resonance images were used to monitor the gadolinium deposition path associated with transcranial pulsed high-intensity focused ultrasound, and the influencing size and location was also investigated. In addition, whole brain histological analysis was performed. The results were compared by two-tailed unpaired t-test.
Results: The accumulation of Evans blue in brains and the tumor:ipsilateral brain permeability ratio of Evans blue were significantly increased after pulsed high-intensity focused ultrasound exposure. Evans blue injection followed by sonication showed an increase in the tumor:ipsilateral brain ratio of the target tumors (9.14:1) of about 2.23-fold compared with the control tumors (x4.09) on day 6 after tumor implantation. Magnetic resonance images showed that pulsed high-intensity focused ultrasound locally enhances the permeability of the blood–tumor barrier in the glioma-bearing rats.
Conclusion: This method could allow enhanced synergistic effects with respect to other brain tumor treatment regimens.

Keywords: focused ultrasound, blood–brain barrier, permeability, brain tumor, glioma

This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution - Non Commercial (unported, v3.0) License. By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms.