Noise-Resistant Weak-Structure Enhancement for Digital Radiography

Today's digital radiography systems mostly use unsharp masking-like image enhancement techniques based on splitting input images into two or three frequency channels. This method allows to enhance very small structures (edge enhancement) as well as enhancement of global contrast (harmonization). However, structures of medium size are not accessible by such enhancement. We develop and test a nonlinear enhancement algorithm based on hierarchically repeated unsharp masking, resulting in a multiscale architecture allowing consistent access to structures of all sizes. The algorithm is noise-resistant in the sense that it prevents unacceptable noise amplification. Clinical tests performed in the radiology departments of two major German hospitals so far strongly indicate the superior performance and high acceptance of the new processing.