Multidetector computed tomography evaluation of normal thymus and variations with age

Area of Science:

• Radiology
• Immunology
• Anatomy

Background:

• The thymus is a primary lymphoid organ crucial for T-cell development, prominent in children and involuting with age.
• Thymic morphology varies significantly across different age groups.
• Computed tomography (CT) is a key imaging modality for evaluating thymic anatomy.

Purpose of the Study:

• To characterize the computed tomography (CT) appearance of the normal thymus.
• To analyze age-related changes in thymic size, CT attenuation, and fatty infiltration.
• To establish normative data for thymic CT characteristics.

Main Methods:

• Retrospective analysis of 450 non-contrast thoracic CT scans.
• Exclusion of patients with known thymic abnormalities or underlying diseases.
• Measurement of thymic dimensions, CT Hounsfield unit (HU) values, and assessment of fatty replacement across age groups.

Main Results:

• Thymic size decreases with advancing age, with complete fatty replacement observed in individuals over 60 years.
• The mean age for complete fatty replacement was 45 years.
• Non-contrast CT attenuation (HU values) was highest in infants and decreased with age, with common shapes including arrowhead and locations pre-aortic/para-aortic.

Conclusions:

• Normal thymic appearance on CT is age-dependent and exhibits considerable variation.
• Establishing normative CT data is essential for accurate differentiation of normal thymic involution from pathological conditions.
• This can prevent unnecessary interventions for benign age-related thymic changes.