The Development of Intra operative Ultrasound Elasticity imaging Techniques to assist during Brain Tumour Resection

Brain tumour resection requires the surgeon to evaluate mechanical properties such as tumour stiffness and adherence o f tumour to the surrounding normal brain. This is a subjective assessment. Ultrasound elasticity imaging techniques allow more objective measurement and imaging o f mechanical properties such as strain, which is related to stiffness, in the case o f ultrasound elastography. This thesis describes the implementation of ultrasound elastography intraoperatively during brain tumour surgery using both an off-line processed and real-time ultrasound elastography system in 24 patients. Elastogram results on stiffness were compared to surgical findings. Adherence o f two surfaces in contact is related to slip which is a type of shear. It occurs when the frictional force binding the two surfaces is overcome. A new imaging technique called slip elastography that images the anatomical location o f a slip boundary and measures the externally applied force at which slip is first detected was developed. The technique provides a measure of the frictional force binding the two surfaces together. The theoretical basis, system development, in vitro testing using gelatine phantoms and the implementation o f slip elastography in 22 patients intraoperatively during brain tumour resection is described. The results indicated that ultrasound elastography is able to distinguish stiffer areas from softer areas intra-operatively during brain tumour resection. It also demonstrated the heterogeneity o f brain tumour stiffness.