Illustration of the Blood-Brain Barrier (image) Purdue University Share Print E-Mail Caption This illustration shows the components of the blood-brain barrier, a collection of blood vessels that filters what goes in and out of the brain. The blood-brain barrier is the greatest obstacle when it comes to treating cancer that has spread to the brain. Credit Daniel Hertzberg Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.