MRI compatible head phantom for ultrasound surgery

Abstract

ObjectiveDevelop a magnetic resonance imaging (MRI) compatible head phantom with acoustic attenuation closely matched to the human attenuation, and suitable for testing focused ultrasound surgery protocols. Materials and methodsImages from an adult brain CT scan were used to segment the skull bone from adjacent cerebral tissue. The segmented model was manufactured in a 3-D printer using (Acrylonitrile Butadiene Styrene) ABS plastic. The cerebral tissue was mimicked by an agar–evaporated milk–silica gel (2% w/v–25% v/v–1.2% w/v) which was molded inside a skull model. ResultsThe measured attenuation of the ABS skull was 16dB/cmMHz. The estimated attenuation coefficient of the gel replicating brain tissue was 0.6dB/cmMHz. The estimated agar–silica gel’s T1 and T2 relaxation times in a 1.5Tesla magnetic field were 852ms and 66ms respectively. The effectiveness of the skull to reduce ultrasonic heating was demonstrated using MRI thermometry. ConclusionDue to growing interest in using MRI guided focused ultrasound (MRgFUS) for treating brain cancer and its application in sonothrombolysis, the proposed head phantom can be utilized as a very useful tool for evaluating ultrasonic protocols, thus minimizing the need for animal models and cadavers.