Spatial frequency filtering in digital subtraction angiography (DSA) by real-time digital video convolution

A circuit has been constructed to perform spatial frequency filtration on DSA images at real-time video rates. The 10-bit device performs low-pass or high-pass filtering, and with external memory can perform bandpass and more sophisticated filtering. Pixels in the convolving kernel are weighted independendently in the x-and y-directions to provide a Gauss-ian-like convolving function. The kernel width ranges from 3-30 pixels and appropriate weighting yields a FWHM of the Gaussian kernel function as small as 0.85 pixel width for horizontal image widths of ≤256 pixels and as small as 1.25 pixel width for a horizontal image width of 512 pixels. Applications to be investigated include scatter and glare correction for videodensitometry, enhancement of arteries behind large opacified structures such as the ventricle and aorta, noise suppression in low-spatial frequency DSA exams, edge-enhancement of images, and partial-pixel shifting. Peli and Lim have suggested a more sophisticated algorithm which enhances high-pass filtration only in dark regions of an image. This and other techniques may be implemented with the current circuit to enhance small detail in highly opacified regions such as the ventricle, while leaving the rest of the image unaltered. © 1983 SPIE.

Duke Scholars

Author James T. Dobbins III Radiology