An in-Field Calibrating Method for the Bilateral Filter Applied to X-ray Flat Panel Grayscale Images with High Spectral Resolution

Several spatial filters applied to images are available in technical and scientific literature. Besides the reduction of the noise level, some of them also aim at the preservation of edges and details. Those filters are commonly applied to the processing of X-ray medical image sequences, which are usually noised due to the low doses of radiation suitable for medical procedures but where the loss of any detail may impair a diagnosis. In this context, the bilateral filter is well suited. However, an adequate calibration of the bilateral filter is required for reaching the best cost benefit between reducing the noise level and preserving the image edges. Calibration procedures are still underexplored in the literature thereby, this paper proposes a new method that allows in-field calibration of the bilateral filter embedded into a piece of equipment for angiography, which uses a flat panel X-ray detector. The proposed method can be applied to images with any spectral resolution and surpasses the performance of the calibration method presented in the literature.