Data rate and dynamic range compression of medical images: Which one goes first?

Advances in the field of medical imaging have led to an immense increase in the volume of images being acquired. A fast growing application is to enable physicians to access image data remotely from any viewing device. This casts new challenges for data rate compression. Meanwhile medical images typically have High Dynamic Range (HDR), which needs to be transformed to Low Dynamic Range (LDR) through a so-called “windowing” operation in order for them to be viewed on standard displays to best visualize specific types of content such as tissues or bone structures. This leads to a basic question: Should data compression be performed before windowing or vice versa? Answering this question needs domain knowledge and also requires comparing HDR and LDR images in terms of objective measures, which has only recently become possible. In this paper, we compare the two alternative schemes by using a recently proposed structural fidelity measure. Our study suggests that data compression followed by windowing delivers better performance than the other alternative.