Age-related changes in CT attenuation of the thymus in children

Abstract

The decline in thymic CT attenuation with age is consistent with fatty infiltration of the gland. The measurements given in this report can serve as a basis for comparison to determine whether the thymus of a young child is normal or pathological.

Imaging of the pediatric thymus: Clinicoradiologic approach

“…The mean thickness of a normal thymus can vary from 0.5 to 1.1 cm as reported by Baron et al[ 9 ]. Computed tomography (CT) density of the thymus has also been reported to decrease with age in children (from 80 HU to 56 HU) likely due to fatty replacement and cellular involution[ 11 ].…”

Imaging of the Pediatric Thymus and Thymic Disorders

“…It demonstrates homogeneous enhancement on post-contrast images. The attenuation of the thymus declines with increasing age as it becomes increasingly replaced with fat (Sklair-Levy et al 2000). On cross-sectional imaging, the appearance of the thymus is consistent with its radiographic appearance.…”

“…The thymus can typically be seen in the anterior mediastinum on CT imaging throughout childhood, and is still visible in most patients up to the age of 30 years. On CT imaging performed without intravenous contrast administration, the thymus has a homogeneous appearance that, compared to cardiac and chest wall musculature, is hyperdense in infancy and nearly isodense later in childhood (mean Hounsfield Unit values ranging from 80.8 in infancy to 56.4 at 14 years of age) (Sklair-Levy et al 2000). It demonstrates homogeneous enhancement on post-contrast images.…”

Imaging of thymic disorders

“…The left lobe is often slightly more prominent than the right, with concave or flat margins in the normal adult [1]. Fatty infiltration begins in childhood, with a gradual decline in CT attenuation, starting at the age of approximately 1 year [3]; the originally homogenous thymic soft tissue gradually involutes and becomes replaced by fat. By the age of 40, the thymus is usually mostly fatty in composition, although it may contain speckles of soft tissue (Fig.…”