Investigation of Ultrasound Properties of the Brain Under Different Thermal Conditions

The Blood Brain Barrier (BBB) is a physical barrier protecting the brain from exposure to undesired materials. Consequently, medicine cannot reach diseased regions such as tumors. Recently, a method using high intensity focused ultrasound managed to temporarily open specific areas of the BBB and this process may induce a local increase in temperature of the tissue and therefore, continuous monitoring is essential. The common approach is to perform MRI non-invasive thermal monitoring, but it is an expensive modality with limited access for patients and clinicians. Ultrasound, on the other hand, offers a hazardless modality with high availability. This study aims to study the ultrasonic properties of the brain under temperature changes. The Experiments consisted of heating bovine brain ex-vivo specimens and measuring their speed of sound (SOS) and attenuation coefficient as a function of temperature. The registered SOS and attenuation coefficient dependence on temperature indicate that there is a well-defined relation between the SOS and attenuation and the brain temperature and it can be used for developing a non-invasive ultrasound based thermal monitoring of brain treatments.