Compression of Biomedical Images and Signals

Chapter 5

Quality Assessment of Lossy Compressed Medical Images

5.1. Introduction

Lossy compression techniques do not leave an original medical image unimpaired. It is therefore necessary to evaluate the degradations caused on the image. For natural images, coding techniques must keep to one single criterion relating to visual quality of the reconstructed image. For medical images, it is essential that the compression avoids any distortions that could modify the diagnostic interpretation of the image and the value of anatomic and/or functional parameters that are supposed to indicate the state of the organ being studied. The American College of Radiology pointed out in its practical guide on radiology that this compression must be carried out without losing any information useful to the diagnosis [AME 05].

Defining the amount of distortion accepted that could preserve the reliability of the diagnosis of the reconstructed image is a complex problem and an open debate in the medical imaging field. In fact, the eligible compression rate does not only change according to the compression method applied, but also largely depends on the characteristics of the image being studied; characteristics that are linked to the gathering techniques as well as to the nature of the organ being explored and to the pathology itself [ERI 02].

In this chapter, we will start by outlining the consequences of any degradations generated by the two compression norms, JPEG and JPEG 2000, in medical imaging. ...