Intra-operative Ultrasound Elastography and Registered Magnetic Resonance Imaging of Brain Tumours: A Feasibility Study

Abstract

Following craniotomy, the decision to resect a brain tumour is based on (1) the surgeon's interpretation of preoperative imaging, such as MRI, (2) correlating the imaging to the surgical field, (3) visual inspection of the surgical field, and (4) palpation thus providing biomechanical information on tumour and brain. There is a degree of subjectivity in the use of palpation for biomechanical evaluation. Ultrasound elastography is a technique for determining more objective biomechanical information at depth in the form of relative strain, thus indirectly stiffness, within an ultrasound scan plane. In addition, neuro-navigation techniques assist in correlating preoperative imaging to the surgical field. We present two cases where ultrasound elastography with co-registered MRI, using neuro-navigation, was used intra-operatively during brain tumour resection. Correlation with the co-registered MRI was excellent in both patients. Strain contrast between brain and tumour was evident in elastograms produced in both patients; the tumour had a lower strain, hence was stiffer compared with brain. When strain applied was increased slip between tumour and brain was detected. All these findings corresponded with the surgical findings. Ultrasound elastography with co-registered MRI is a promising imaging technique, which can be used intra-operatively to provide biomechanical information prior to resection.