Steven C. Horii, MD

Figure 3. Simple E-R model shows the relationship between a patient and the images obtained of that patient. The entities are represented by rectangular boxes and the relationships by diamond-shaped boxes. The small characters next to the arrows indicate that one patient may have n studies and that one study may contain n images. The arrows do not indicate data movement; rather, they are included to avoid ambiguity or nonsensical relationships (eg, it would make no sense to say that an image contains a study). Only three patient attributes -- name, medical record number, and age -- are shown. If the number of attributes is large, they may not be included in the E-R diagram.