Method for reducing noise in a sequence of fluoroscopic images by temporal and spatial filtering

摘要

In the field of medical imaging using fluoroscopy, a method for reducing noise in a sequence of fluoroscopic images acquired by an X-ray detector comprises for each image (xn) of the sequence: applying temporal filtering to the image (xn) at instant n, the temporal filtering comprising fluoroscopic noise reduction processing; applying spatial filtering to the image (yn) at instant n, the spatial filtering comprising: transforming the image (yn) acquired at the instant n from the spatial domain into the curvelet domain using a curvelet transform, each transformed image being represented by a set of coefficients, thresholding the coefficients of the image (yn) using a thresholding function, the thresholding function cancelling the coefficients below a third predetermined threshold, and preserving or adjusting the coefficients above the third predetermined threshold, transforming the image (Zn) whose coefficients have been thresholded from the curvelet domain into the spatial domain using an inverse curvelet transform.

主权项

1. A method for reducing noise in a sequence of fluoroscopic images acquired by an X-ray detector, each image (xn) being formed in the spatial domain by a matrix of pixels, each pixel having a value representative of a signal level, the method comprising the following successive steps for each image (xn):
applying temporal filtering to the image (xn) acquired at an instant n, the application of said temporal filtering comprising the following substeps for each pixel of the image:
determining a difference between the value of the pixel considered in the image (xn) acquired at the instant n and the value of the corresponding pixel in the image (yn-1) acquired at an instant n−1 to which the temporal filtering has been applied,if the difference is below a first predetermined threshold S1, correcting the value of the corresponding pixel with a first set of parameters,if the difference is above a second predetermined threshold S2, correcting the value of the corresponding pixel with a second set of parameters, applying spatial filtering to the image (yn) acquired at the instant n, the application of said spatial filtering comprising the following substeps:
transforming the image (yn) acquired at the instant n from the spatial domain into a curvelet domain using a curvelet transform, each image in the curvelet domain being represented by a set of coefficients,thresholding the coefficients of the image (yn) using a thresholding function, the thresholding function cancelling the coefficients below a third predetermined threshold, and preserving or adjusting the coefficients above the third predetermined threshold,transforming the image (yn) whose coefficients have been thresholded from the curvelet domain into the spatial domain using an inverse curvelet transform.