Assessment of the Thymus
and the Measurement of the Thymic Size
in Healthy Neonates from North India
Associate Professor, Department of Radiology,
SGRR Institute of Medical & Health Sciences,
Patel Nagar, Dehradun, India- 248001.
Objective: To create the reference standards for the thymic size by sonography in healthy neonates in the north Indian population and to assess the variation in its location, echogenicity and echopattern.
Material and Methods: This study was done prospectively on 200 healthy term neonates from north India at less than one week of age. The size of the thymus was measured in terms of the transverse diameter, the sagittal area, the thymic index and the anteroposterior (AP) diameter and the normal reference standards were created. The thymus was assessed in terms of its location, echogenicity (done in terms of the relative echogenicity number) and echopattern. The comparison of the thymic echogenicity and the echopattern with that of the liver, spleen and the thyroid was also performed.
Results: The range of the thymic transverse diameter was 1.6-4.2 cm (mean 2.68 Â± 0.54), that of the sagittal area was 1.31â€“5.13 cm2 (mean 3.01 Â± 0.74), that of the thymic index was 2.60â€“16.93 cm3 (mean 8.10 Â±2.74), that of the AP (Right) was 0.50â€“2.30 cm (mean 1.27 Â± 0.35), that of the AP (left) was 0.20â€“2.90 cm (mean 1.72 Â±0.4) and that of the AP (mean) was 0.40â€“2.35 cm (mean 1.49 Â± 0.33). The thymus was located in the supero-anterior mediastinum and it was less echogenic than the liver, spleen and the thyroid. In majority of the subjects, the thymus was coarser in echo pattern than the spleen. However, it resembled or was coarser than the liver and the thyroid in almost equal proportions.
Conclusion: The normative standards of the thymic size and the thymic appearance in a given population are useful in assessing this complex lymphoid organ sonographically in health and disease and also to carry out various immunological studies.