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The final section, Part V, contains a concise Index of Figures for easy reference to visual support; an imaging-specific Glossary of Terms; a list of Suggested Reading resources for more in-depth study; and a helpful Subject Index for quick access to particular conditions, techniques, and cases. Interpreting diagnostic images produced by any modality requires a combination of skill and experience. The skill component can be developed by training and study, but experience can only be obtained over time. Regardless of the diagnostic imaging modality, a consistent systematic approach to interpretation is essential to accurate analysis and reliable diagnoses. Radiologic interpretation is based on detecting alterations from normal. Changes in size, shape, margin, position, number, symmetry, and opacity are evaluated. The same process can be applied to other imaging modalities by substituting ❏ opacity for echogenicity in diagnostic ultrasound, ❏ attenuation in computed tomography, ❏ signal intensity in magnetic resonance imaging, and ❏ radiopharmaceutical uptake in nuclear medicine. Thorough analysis of the images presented is essential to reaching an accurate diagnosis. The most reliable approach is to use a combination of two techniques. The observer should evaluate all of the body parts or components in the image sequentially. It is important to develop a checklist and always follow the list. This approach is especially useful for complex images, such as thoracic radiographs and abdominal ultrasound. Second, one should consider what diseases may affect a particular body part and evaluate the image for evidence of lesions. This is most useful when evaluating the musculoskeletal system, where structures are less complex. One must be careful, however, not to develop tunnel vision or search for what one thinks is the most likely diagnosis. The process of lesion detection can be divided into three phases: fixation, recognition, and diagnosis. As the eye scans an image, a vast amount of information is presented to the brain. Fixation occurs when the eye focuses on a portion of the image. Factors that influence how the brain perceives this data include lighting conditions, image sharpness, and image contrast. Many optical illusions are based on the tendency of the brain to distort data presented to it by the eyes. In other words, what the eye sees is not always what the brain sees; and this disparity occurs frequently when viewing radiographs. After an image has been presented to the brain, the second phase, lesion recognition, depends on a process of comparing the actual image with the expected normal appearance. This phase is affected by the experience of the observer; in effect, the quality and quantity of stored normal images in the brain. Other factors that may influence this phase include bias or prejudice on the part of the observer.

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