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INTRODUCTION

Key Points

  • Digital records of sound, still, and moving images are increasingly prevalent in medical care.

  • Medical records are being digitized.

  • The efficient storage and transmission of digital information depends on digital compression.

  • The use of digital formats permits the application of the same digital signal enhancement techniques that have been depicted in forensically oriented television and movies.

Still and moving digital images are increasingly becoming a part of the medical record, which will no doubt ultimately become a mixed multimedia virtual document encompassing many different types of information. This could conceivably include audio or video recordings of doctor-patient interactions, perhaps even records of auscultation and or the physical examination of a patient using haptic technology (Fig. 16-1).

Figure 16-1

A variety of digital information including still images, audio files, video data, and perhaps even recordings of examinations will become part of the electronic medical record of the future.

Records of this kind will be “bulky” when first acquired and they will probably undergo some degree of compression prior to storage and/or transmission. Additionally, because they are digital, multimedia files are susceptible to computerized techniques for enhancement of the signal of interest (i.e., sound, picture) (Fig. 16-2).

Figure 16-2

Computers can be used to enhance signals of interest in audio and visual data.

This chapter provides a brief introduction to the concepts and implications of data compression, transmission and manipulation, and their application in a medical setting, and will focus primarily on still images and video, although the same principles are applicable to sound as well.

DIGITAL RECORDING BASICS

Key Points

  • The same data, be it sound or image, can be stored in a variety of ways with significantly different degrees of efficiency, portability, and integrity depending on what format is used.

  • A large variety of storage formats have been developed, and they differ in their intent—some are designed for faithful (lossless) reproduction of data others for efficient storage (lossy).

  • Many data storage formats have a large amount of “empty space” such as the white are on a piece of newspaper.

  • Compression is used in all of our communications (i.e., telephony) and usually with no significant impact on our comprehension.

Information can be stored in many ways, some of which are inherently inefficient relative to others. For example, an interval of sound can be stored on a wire, a polyvinyl chloride platter, or CD. Similarly, a document can be stored as a printed piece of paper or a sequence of letters and formatting codes used by a word processing program to arrange the letters. The same letter can also be stored as a picture image, as a digital camera, copier or ...

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