CHIC: cylindrical helix imaging coordinate registration fiducial for MRI-guided interventions

Accurate placement of tubular shaped surgical tools is necessary for a large variety of image-guided medical interventions. In this process, localization of the instrument, or a robotic assistant manipulating the instrument, is crucial for successful registration of physical space to medical image space. Various fiducial frames and registration methods have been proposed and discussed in literature. However, these frames are typically bulky in size or otherwise not appropriate for use with MR imaging. In particular, it is impossible or awkward to integrate them with the surgical tools. This paper presents the design a compact Cylindrical Helix Imaging Coordinate Registration Fiducial (CHIC) and algorithm to precisely and robustly localize the frame in 6 degree of freedom (DOF). The mathematical model of the frame is developed and evaluated with simulation. This cylindrical shaped frame is particularly suitable for mounting to the distal end of tubular shape surgical tools, which provides a direct imaging visualization of frame, tool and possibly the surgical sites. The paper uses MRI-guided surgical procedure as a focusing application, although the broader aim is development of a versatile registration frame that is usable for a variety of image-guided procedures ranging from ultrasound to fluoroscopy and computerized tomography (CT). Accuracy and performance were evaluated in three cases: simulated images with artificial noise, arbitrarily re-sliced 3D MRI volume, and real 3T MRI images.