Practical Applications of Mach Band Theory in Thoracic Analysis

Abstract

In this review, routine radiographs with computed tomographic (CT) correlation are used to demonstrate practical applications of Mach band theory in thoracic analysis. Mach bands represent optical psychophysiologic edge-enhancement phenomena produced by means of lateral inhibition in the retina of the eye. Visualization of Mach bands depends on a set of variables that involve primarily the contour and optical density of a structure at an interface relative to that of its surround. On the basis of their appearance, the bands are defined as positive (white) or negative (black). The concept of Mach bands contributes to a greater understanding of three-dimensional structures projected onto two-dimensional routine radiographic images of the thorax. Mach bands can help differentiate normal from abnormal anatomy and thus increase the diagnostic yield from such images. Mach bands can be seen on images that use transmitted or reflective light, including CT scout images (topograms) of the thorax.

A lexicon for hepatocellular carcinoma surveillance ultrasonography: benign versus malignant lesions

“…In our study, thick hypoechoic rim was significantly associated with malignancy, while thin hypoechoic rim exhibited no significant association. Thin hypoechoic rims observed around benign lesions are more likely to be pseudo-rims, i.e., Mach bands rather than true rims, created because of an optical effect at margins between areas of different echogenicities [16]. In contrast, hyperechoic rim with partially hypoechoic internal pattern has been reported as being specific for hepatic hemangioma [11,13].…”

How reader perception of capsule affects interpretation of washout in hypervascular liver nodules in patients at risk for hepatocellular carcinoma

“…However, our objective analysis of washout demonstrated a significantly weaker association compared with a purely subjective analysis. One possible explanation for this weaker association is that capsules could create the optical illusion of “washout,” which is similar to the Mach band effect, where the visual system enhances the perception of contrast between two objects of different brightness when they are adjacent to one another . This phenomenon might be accentuated within a small nodule than in the nearby liver parenchyma, since the nodule is closely surrounded by the hyperintense capsule.…”

“…One possible explanation for this weaker association is that capsules could create the optical illusion of "washout," which is similar to the Mach band effect, where the visual system enhances the perception of contrast between two objects of different brightness when they are adjacent to one another. 22,23 This phenomenon might be accentuated within a small nodule than in the nearby liver parenchyma, since the nodule is closely surrounded by the hyperintense capsule. Another explanation could be the reader's predisposition to believe that nodules with a capsule are HCCs and therefore more likely to have washout.…”

CT scout view as an essential part of CT reading

“…A CT scout view is actually a regular radiograph obtained with high kilovolts and low milliamperes using sophisticated CT equipment. Therefore, basic principles of radiological interpretation are valid for CT scout view, for example as shown by Chasen in the practical applications of Mach band theory for chest CT scout views 1 . Thus, CT scout view should be evaluated with various window levels: bone, lung and soft tissue, as any other slice of CT.…”