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The imaging appearance of crayons
Aaron S McAllister1, Neil U Lall2,3, Kareem O Tawfik4
1Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH, 45229, USA. aaron.mcallister@cchmc.org.
Background:
A crayon fragment was determined to be the source of a foreign body inflammatory process in the masticator space of a 15-month-old boy. The appearance of the crayon on CT and MR imaging was unexpected, leading to a further analysis of the imaging features of crayons.
Objective:
To investigate and characterize the imaging appearance of crayons at CT and MRI.
Materials And Methods:
The authors obtained CT and MR images of 22 crayons from three manufacturers and three non-pigmented crayons cast by the authors. CT attenuation of the crayons and diameter of the MRI susceptibility signal dropout were plotted versus brand and color.
Results:
All crayons demonstrated a longitudinal central hypo-attenuating tract. Crayon attenuation varied by brand and color. All of the crayons demonstrated a signal void on T1 and T2 imaging and signal dropout on susceptibility-weighted imaging, the diameter of which varied by brand and color.
Conclusion:
Understanding the imaging appearance of crayons could help in the correct identification of a crayon as a foreign body on imaging studies, even when it is located in unusual places.
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