Gradient-Based 2D/3D Rigid Registration of Fluoroscopic X-ray to CT

Harel Livyatan, Ziv Yaniv, and Leo Joskowicz
School of Computer Science and Engineering
The Hebrew University of Jerusalem, Jerusalem 91904, Israel.

Abstract: 

We present a gradient-based method for rigid registration of a patient
preoperative CT to its intraoperative situation with a few fluoroscopic
X-ray images obtained with a tracked C-arm.  The method is non-invasive,
anatomy-based, requires simple user interaction, and includes
validation. It is generic and easily customizable for a variety of routine
clinical uses in orthopaedic surgery.  Gradient-based registration consists
of three steps: 1.  initial pose estimation; 2. coarse geometry-based
registration on bone contours, and; 3.  fine Gradient Projection
Registration (GPR) on edge pixels.  It optimizes speed, accuracy, and
robustness. Its novelty resides in using volume gradients to eliminate
outliers and foreign objects in the fluoroscopic X-ray images, speed up
computation, and achieve higher accuracy. It overcomes the drawbacks of
intensity-based methods, which are slow and have a limited convergence
range, and of geometry-based methods, which depend on the image
segmentation quality.  Our simulated, in-vitro, and cadaver experiments on
a human pelvis CT, dry spine, dry femur, fresh lamb hip and human pelvis
under realistic conditions show a mean 0.5--1.7mm (0.5--2.6mm max) target
registration accuracy. 


Keywords: 2D/3D rigid registration, image-based registration, gradient
projection registration, fluoroscopic X-ray to CT registration.

Published in: IEEE Trans. on Medical Imaging, Vol 22(11), 2003, pp
1395--1406.  Special issue on Medical Image Registration, M. Fitzpatrick
and J. Pluim editors,