While radiology was founded when X-rays spoiled a piece of photographic film, modern medical imaging has evolved to become primarily electronic. Computers, electromagnetic storage systems, and information networks are rapidly replacing photographic film as the means of viewing, storing, and distributing radiologic images. As with any media, however, these electronic systems have idiosyncrasies that can lead to misinterpretation and error. It is therefore vital for radiologists to understand the foundations of the electronic media, so as to be able to recognize these pitfalls nd, to the extent possible, adjust for them.

Using some interesting images as starting points, we will discuss how modern systems store and display two-dimensional (2-D) and three-dimensional (3-D) images, as well as describe the additional text data necessary to provide the proper context for the imaging.

Two-dimensional radiologic imaging

In Figure 3.1, we have four identical images. Well, at least the images are identical in terms of how they are stored on a computer. On the screen, they are clearly very different. While the basic structures of the images generally appear similar, color and intensity have been varied to emphasize different aspects of the images. Given that the images were created from identical datasets, what could account for these differences? To understand this better, let us delve into how radiology images are stored and displayed using computer systems. We will start by examining the foundations of 2-D radiologic images, and explore how they relate to the pictures that actually appear on a computer monitor.