Multimodal imaging fiducial markers for kinematic measurement of joint models

Abstract

Background: Fiducial markers are objects placed in the field of view of an imaging system for use as a point of reference or a measure. There is no information regarding suitable markers for joint models. Objectives: We compared the fiducial markers commonly used in X-ray, CT, and MRI imaging modalities. Methods: The markers tested were plastic balls, ceramic balls, passive reflective balls, liquid-filled balls, and steel balls. The balls were scanned using X-ray, CT, and MRI systems. The scanned X-ray images were reviewed if it the markers are able to be expressed. The tomographic images of CT and MRI were converted into 3D ball models and then the reconstructed shapes and dimensions of the balls were examined. The dimensional accuracy of expression and reconstruction was calculated in terms of the mean and the standard deviation. Results: There was no marker that can be expressed in all the imaging modalities. Alternatively, we propose a synthetic marker that is composed of a hard sphere and a fat tissue wrapping. The hard ball is for X-ray and CT imaging, while the fat tissue is for MRI imaging. Conclusion: A synthetic marker composed of a hard sphere and a fat tissue wrapping can a multimodal fiducial marker. Keywords: Accuracy, fiducial marker, multimodal, registration