Simultaneous denoising and enhancement for X-ray angiograms by employing spatial-frequency filter

X-ray angiograms, which suffer from low-contrast and noise, need to be improved by both the image enhancement and denoising techniques. However, the goals of these two tasks usually conflict, which makes it difficult to efficiently combine the enhancement and denoising in one scheme. To deal with this problem, we propose a novel spatial-frequency filtering (SFF) scheme for high-contrast X-ray cardiovascular angiogram image restoration. The proposed scheme includes the following four parts: (1) low-quality X-ray angiogram images are decomposed into the base layer with strong structures and redundant parts by employing a relative total variation (RTV) method. (2) the base layer is enhanced by a proposed improved histogram equalization (IHE) method. (3) The detail layer with weak structures is extracted by using a short-time Fourier transform (STFT) and is further enhanced by a proposed adaptive correction parameter. (4) The improved image is the combination of results obtained by the base layer and the detail layer. Experimental results in both qualification and quantitation validate that the proposed method performs better than the state-of-the-arts on contrast enhancement, structure preservation, and noise reduction.