Roswell Park Comprehensive Cancer Center
The visual world, including the world of diagnostic imaging, is filled with illusions. Some illusions, such as imaging artifacts, are avoidable or mitigable. Illusions of sensation, however, arise from physiological mechanisms in the beholder's eye and nervous system, and cannot be avoided. This educational exhibit seeks to promote awareness of these illusions and how they can affect diagnostic imaging.
Educational Goals / Teaching Points
Visual illusions are aberrations in the perception of reality which occur as a result of the method by which images are generated, retinal processing of light into neural activity, or the organization of visual information to form a mental image. Illusions are classified based upon the point at which they occur along this pathway. Illusions of sensation, which arise from retinal processing, occur frequently in radiology and can elicit either a false positive or false negative finding. For example, Mach bands and background effects are illusions of sensation that arise from lateral inhibition in the retina. Their effects can be seen across several imaging modalities. In this educational exhibit, we will review common scenarios where these illusions can pose a diagnostic challenge, and discuss strategies that radiologists can take to distinguish these illusions from reality.
Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
This educational exhibit will review illusions of sensation, including Mach bands and background effect, as they pertain to diagnostic imaging with plain film X-rays, mammogram, conventional angiography, ultrasound, and CT.
Illusions of sensation cannot be avoided, but knowledge of these illusions can be useful for avoiding false positive and false negative diagnoses in diagnostic imaging.