Adaptive Histogram Equalization (AHE) has been applied to high resolution digital chest radiographs to provide contrast enhancement. The method provides good contrast in uniform areas of the image, e.g. the lung field, but in so doing both overenhances noise and produces an artifact at boundaries between high density and low density regions. The artifact, which appears as a band of very low contrast data spanning such a boundary, has the effect of suppressing structural information. Although it is known that the problem of overenhancing noise is controlled by the algorithm known as Contrast Limited Adaptive Histogram Equalization (CLAHE), the boundary artifact is not removed by this technique. This paper concentrates on the boundary artifact. We present a method for processing a chest radiograph by means of background subtraction prior to applying the CLAHE algorithm which reduces contrast at high/low density boundaries and thus permits contrast enhancement free of both noise and boundary artifacts.