X-ray collimator shutter detection by active-rods

We present Active-Rods, a technique for automatically detecting collimator shutter edges in digital radiographs. Unlike the active contour method designed for smooth boundary contouring, the Active-Rods approach seeks straight line open boundaries. The shutter detection problem is formulated as minimizing an energy functional of both local edges and regional statistics. Initial shutter positions are obtained through edge detection, modeling and grouping for desired collinear sets. Rod translations and rotations are driven by the forces and torques via energy minimization. This technique has demonstrated promising shutter detection on a broad range of clinical images.