C-Arm imaging for brachytherapy source reconstruction: geometrical accuracy.

We study the accuracy of brachytherapy source reconstruction using C-Arm images. We use a phantom embedded with dummy ribbons in a regular pattern, placed at the rotation center of the C-Arm. With a commercial reconstruction jig, radiographic films are taken without the image intensifier. The average error in reconstructed seed coordinates is 0.1 cm. However, the jig is inconvenient for patient procedures. For C-Arm reconstruction without the jig, the magnifications of the image intensifier along orthogonal directions are different. We "stretch" the image to equalize the magnifications. Afterward, seed reconstruction has an average error of 0.1 cm in all directions.