PC-based system for 3D registration of ultrasound and magnetic resonance images based on a magetic position sensor

Abstract

Stereotactic systems are based on preoperative tomographic images for assisting neurosurgeons to accurately guide the surgical tool into the brain. In addition, intraoperative ultrasound (US) images are used to monitor the brain in real time during the surgical procedure. The main disadvantage of stereotactic system is that preoperative images can become outdated during the course of the surgery. The main disadvantage of intraoperative US is the low signal-to-noise ratio that prevents the surgeon from appreciating the contents and orientation of the US images. A system that combines preoperative tomographic with intraoperative US imags could overcome the above-mentioned disadvantages. We have successfully developed and implemented a new PC-based system for interactive 3D registration of US and magnetic resonance images. Our software is written in Microsoft Visual C++ and it runs on a Pentium II 450-MHz PC. We have performed an extensive analysis of the errors of our system with a custom-built phantom. The registration error between US and MR space was dependent on the depth of the target within the US image. For a 3.5-MHz phased 1D array transducer and a depth of 6 cm, the mean value of the registration error was 2.00 mm and the standard deviation was 0.75 mm. The registered MR images were reconstructed using either zero-order or first-order interpolation. The interactive nature of our system demonstrates its potential to be used in the operating room.