Local brain tissue pressure monitoring based on subharmonic-assisted pressure estimation combined with shear wave...

Traumatic brain injury (TBI) is the leading cause of mortality and disability among young people. There is an urgent clinical need for a noninvasive method that can accurately measure the local pressure in damaged brain tissue, which is of great significance for real-time monitoring of TBI progression, timely intervention, and improving the survival rate of TBI patients.

We proposed a noninvasive local brain tissue pressure (BTP) measurement technique combining subharmonic-assisted pressure estimation (SHAPE) and shear wave elastography (SWE) in a craniectomy rat model. Nonlinear subharmonic scattering signals from microbubbles and Young's modulus within the injury region were acquired using a customized ultrasound scanner. Three random forest models (SHAPE alone, SWE alone, and their combination) were built to predict local BTPs, and the receiver operating characteristic (ROC) curves were used to evaluate the models' diagnostic value for elevated BTPs.

The SHAPE combined SWE model demonstrated optimal predictive performance, with a root-mean square error (RMSE) of merely 2.794 mmHg, and a sensitivity of 100%, specificity of 84.42%, accuracy of 84.38% for predicting BTP > 20 mmHg.

The SHAPE+SWE combination outperforms either modality alone, suggesting that BTP is jointly determined by local blood flow pressure and the stiffness of the local brain tissue.

This study represents a proof-of concept method of assessing local BTP following TBI by combining SHAPE with SWE. It can hold promise as a novel, minimally invasive, and precise alternative approach for measuring local BTP in TBI patients after further validation of clinical transcranial application.