AbstractID: 8886 Title: X-Ray Beam Tracking System for a Fluoroscopic C-Arm Unit
A system has been developed to determine the position of the x-ray beam and patient table for a ceiling mounted digital fluoroscopic
c-arm unit. This information can be used to track the location of radiation exposure on the patient dynamically during the course of a
procedure for deterministic risk assessment and to assist in stereotactic or 3D projection image reconstruction. The six degrees of
freedom of the x-ray tube coordinates and four additional degrees for table localization are determined from sensors built into the unit.
The analog sensor signals are filtered and digitized to a 12-bit serial signal which is read by a program that converts the voltage values
to coordinate values using calibration curves. With these curves, angular coordinates can be determined to within a half of a degree
and translational coordinates to within 2 mm. The positional calibration methods used and the mathematics of the beam coordinate
transformation will be described. The system includes a real-time graphic display of the c-arm gantry and table at their current
position with all beam coordinates given. This display was created by modeling a volume-based description of each component of the
machine using C++ object capabilities and OpenGL visualization was implemented. The system developed provides immediate visual
feedback of x-ray beam and table location and allows their coordinates to be directly imported by external software with increased
precision over the c-arm manufacturer display values.
Supported by FDA grant #R44FD-01584-02, Esensors, Inc. and an equipment grant from Toshiba Corp.