What imaging finding defines Pectus excavatum on CT chest?

What imaging finding defines Pectus excavatum on CT chest?

• A. CT chest with Haller index of 3.2 or greater
• B. Chest X-ray showing elevated diaphragms
• C. MRI chest with posterior sternum indentation
• D. Ultrasound showing anterior chest wall deformity

Answer: (A)

The main concept here is using a CT-based quantitative metric to define pectus excavatum. On CT, the chest’s transverse width and its anteroposterior (AP) depth are measured on an axial image at the level of the deepest sternal depression. The Haller index is the ratio of the transverse (left–right) diameter to the AP diameter. Because the sternum is sunken in pectus excavatum, the AP distance shortens while the width is relatively unchanged, causing the Haller index to rise. A value around normal is roughly 2.5; a Haller index of 3.2 or greater signals a significant deformity and is a commonly used threshold for severity and surgical consideration. This CT-specific measurement provides a reproducible, objective definition of the condition on imaging. Other options do not give this precise CT-based metric: chest X-ray lacks the same quantitative assessment, MRI isn’t the standard way to define the deformity on imaging, and ultrasound is not used for characterizing this chest wall contour.

The main concept here is using a CT-based quantitative metric to define pectus excavatum. On CT, the chest’s transverse width and its anteroposterior (AP) depth are measured on an axial image at the level of the deepest sternal depression. The Haller index is the ratio of the transverse (left–right) diameter to the AP diameter. Because the sternum is sunken in pectus excavatum, the AP distance shortens while the width is relatively unchanged, causing the Haller index to rise. A value around normal is roughly 2.5; a Haller index of 3.2 or greater signals a significant deformity and is a commonly used threshold for severity and surgical consideration. This CT-specific measurement provides a reproducible, objective definition of the condition on imaging. Other options do not give this precise CT-based metric: chest X-ray lacks the same quantitative assessment, MRI isn’t the standard way to define the deformity on imaging, and ultrasound is not used for characterizing this chest wall contour.