A fast and effective method for enhancement of contrast resolution properties in medical images

In medical imaging, the poor quality image specifically the low contrast image may deliver inadequate data for the visual interpretation of affected portions. Hence, a combined approach called exposure based contrast limited bi-histogram equalization method is proposed to improve the visual quality of medical images. The proposed method has three stages: At first, input histogram is sub-divided into two histograms based on the exposure threshold to preserve mean brightness and strengthen the fine details. Then, the two sub histograms are clipped to limit the contrast amplification and a new dynamic range is assigned to each clipped sub-histogram by its exposure threshold value. At last, a contrast-enhanced image is gained by equalizing each clipped sub-histogram individually. Experiments were conducted on a wide variety of medical images to evaluate the performance of proposed method both qualitatively and quantitatively. Extensive quantitative measures show that the proposed technique achieves better performance in terms of peak signal to noise ratio, entropy, contrast ratio, enhancement measures and computational complexity when compared to state of art enhancement methods. The proposed algorithm improves contrast while preserving brightness and visual quality. The proposed method provides better quality for disease examination and diagnosis.