Chan, HW; (2016) Optimising the use and assessing the value of intraoperative shear wave elastography in neurosurgery. Doctoral thesis , UCL (University College London).

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Abstract

The clinical outcomes for epilepsy and brain tumour surgery depend on the extent of resection. Neurosurgeons frequently rely on subjective assessment of stiffness and adherence to achieve maximal resection. However, due to similarity in tactile texture and visual appearance of these lesions to normal brain, this can lead to inadequate resection. Magnetic resonance imaging (MRI) has not completely solved this problem for various reasons, including the existence of MRI-negative lesions. Shear wave elastography (SWE) is an ultrasound-based quantitative elasticity imaging technique that provides an objective assessment of stiffness, which has not previously been applied intraoperatively during neurosurgery. This thesis describes the optimisation and assessment of implementing intraoperative SWE in neurosurgery. The aims of the work described in this thesis were to validate SWE measurements; to optimise intraoperative applications by investigating the artefacts of SWE; to evaluate SWE performance in detecting epileptogenic lesions, residual tumour and slippery boundaries; and to determine the histopathological correlation with SWE measurements. Using gelatine phantoms and post-mortem mouse brains, SWE measurements were validated. Through phantom models and ex vivo porcine brains and spinal cords, the factors affecting SWE measurements were established and SWE settings optimised. In addition, novel features of slippery tumour-brain interface were demonstrated in vitro and confirmed intraoperatively. Clinical implementation of SWE in epilepsy (38 patients) and brain tumour surgery (34 patients), demonstrated SWE’s capability in differentiating epileptogenic lesions (p<0.001) and brain tumours (p=0.003) from normal brain. SWE was shown to be superior to MRI in detecting epileptogenic lesions (p=0.001), in particular MRI-negative cases where SWE managed to demonstrate lesions in 4 cases with positive histology. For detecting residual tumour, SWE was shown to be superior to surgeons’ opinion (p=0.001), and similar to MRI (p=1.000) and intraoperative B-mode ultrasound (p=0.727). Histopathologically, there was no correlation with SWE measurements, except for proliferation (p=0.007). In conclusion, this thesis demonstrated potential patient benefit of integrating intraoperative SWE into neurosurgical practice, and therefore, a compelling reason to continue development and optimisation of this technology.

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