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Mach band sign: an optical illusion
Ragesh Panikkath1, Deepa Panikkath1
1Department of Internal Medicine, Texas Tech University Health Sciences Center School of Medicine, Lubbock, Texas.
Proceedings (Baylor University. Medical Center)
|December 9, 2014
Summary
A chest X-ray initially suggested pneumopericardium in an unresponsive patient. However, this was a Mach band sign artifact, not actual air around the heart.
Area of Science:
- Radiology
- Medical Imaging
- Ophthalmology
Background:
- Pneumopericardium, air in the pericardial sac, is a critical finding on chest radiographs.
- Distinguishing true pneumopericardium from imaging artifacts is essential for accurate diagnosis.
Observation:
- A 63-year-old woman presented with an unresponsive state, and her initial chest radiograph showed a shadow concerning for pneumopericardium.
- This shadow lacked other typical features of pneumopericardium, and subsequent radiographs showed no air around the heart.
Findings:
- The concerning radiolucent shadow was identified as a Mach band sign.
- The Mach band sign is a visual artifact resulting from lateral inhibition in retinal photoreceptors.
Implications:
- This case highlights the importance of recognizing visual artifacts in medical imaging interpretation.
- Understanding the Mach band sign can prevent misdiagnosis of critical conditions like pneumopericardium.
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