<title>Digital Storage Compression For Diagnostic Images</title>

Abstract

The compression of the digital information in a diagnostic image allows data to be stored in a smaller memory. This directly effects the cost and performance of computerized diagnostic imaging systems. Predictive compression (PC) combined with variable length coding (VLC) can achieve image compression with no alteration of the image element values. PC uses the values of neighboring, or previously transmitted, picture elements to predict a value for the next picture element. The difference between the prediction and the actual pixel value is then stored, in lieu of the actual pixel value. VLC techniques allow the differential signal to be encoded so that values which occur most frequently are stored with as little as one binary bit. The use of PC and VLC reduces the number of bits required to store an image. We have determined the compression factor (original/compressed bits per image) associated with five linear PC algorithms encoded with six VLC techniques for Ultrasound, Nuclear Medicine, Computed Tomography and Digital Roentgenographic images. The results allow us to identify PC and VLC algorithms most suitable for diagnostic imaging. Compression factors between 1.5 and 4 are achievable with simple algorithms.