Abstract
A key problem in using digital subtraction radiography in dentistry is the ability to reposition the X-ray
source and patient so as to reproduce an identical imaging geometry. In this paper we describe an
approach to solving this problem based on real time sensing of the 3-D position and orientation of the
patient's mouth. The research described here is part of a program which has a long term goal to develop
an automated digital subtraction radiography system. This will allow the patient and X-ray source to be
accurately repositioned without the mechanical fixtures that are presently used to preserve the imaging
geometry.
If we can measure the position and orientation of the mouth, then the desired position of the source can be
computed as the product of the transformation matrices describing the desired imaging geometry and the
position vector of the targeted tooth. Position and orientation of the mouth is measured by a real time
sensing device using low-frequency magnetic field technology.
We first present the problem of repositioning the patient and source and then outline our analytic solution.
Then we describe an experimental setup to measure the accuracy, reproducibility and resolution of the
sensor and present results of preliminary experiments.