Objectives/hypothesis: The purpose of this study is to review the computed tomography (CT) scans of infants, children, and adults to assess the degree of calcification of the thyroid cartilage at various ages in order to understand in which age group laryngeal ultrasound can be utilized.
Study design: Retrospective.
Methods: Two hundred patients from newborn to 50 years who received a CT scan of the neck were identified. The Hounsfield units (HU) of the thyroid cartilage were calculated at one o'clock, four o'clock, eight o'clock, and eleven o'clock at the level of the true and false vocal fold. The Spearman correlation coefficient was calculated to evaluate the correlation between each measure and age, then a linear regression with a logarithmic transformation was applied to further study how the measures were related to age.
Results: The Spearman correlation coefficients ranged from 0.58 to 0.75. The P values of these coefficients were all < 0.0001, showing a significant relationship to age. The age increase by 1 year resulted in increased calcification by 1.5% to 4%. The Wilcoxon signed rank test compared the rate of calcification at each site measured. This showed that the two posterolateral sites calcify faster than the two anteromedial sites.
Conclusion: The thyroid cartilage calcifies at a rate that is significantly related to increasing age and calcifies in a posterolateral to anteromedial direction. Based on the HU, the thyroid cartilage is not consistently denser than soft tissue until greater than 40 years of age, which would make laryngeal ultrasound feasible for this population.
Level of evidence: 4.
Keywords: Thyroid cartilage calcification; laryngeal ultrasound.
© 2015 The American Laryngological, Rhinological and Otological Society, Inc.