Figure 1
The axial thoracic contrast-enhanced computed tomography images present the morphologic features of the thymus in children. (A) 1 year old girl; round-oval shape; biconvex margins; predominantly left-sided location; Score 3, mainly soft-tissue attenuated thymus. (B) 4 months old boy; round-oval shape; biconvex margins; predominantly right-sided location; Score 3, mainly soft-tissue attenuated thymus. (C) 5 years old boy; quadrilateral shape; mixed (right straight, left convex) margins; middle location; Score 3, mainly soft-tissue attenuated thymus. (D) 15 years old boy; triangular shape; straight margins; middle location; Score 2, nearly half fatty and half soft-tissue attenuated thymus. An example of a manually delineated free-hand region of interest (ROI) for measuring the CT attenuation value is presented. (E) 17 years old boy; triangular shape; straight margins; middle location; Score 1, mainly fatty thymus. (F) 18 years old boy; triangular shape; biconcave margins; middle location; Score 0, complete fatty thymus.
Figure 2
The graph shows the measurements of the maximum anteroposterior (AP) and transverse (TR) diameter of the thymus; maximum width (W) and thickness (T) of the thymic lobes in the (A) round-oval, (B) quadrilateral, and (C) triangular thymic shape.
Table 1
Distribution of the shape, margins, and side predominance of the thymus according to age.
| MORPHOLOGIC FEATURES OF THE THYMUS | GROUP 1 (0–12 MONTHS) N (%) | GROUP 2 (1–3 YEARS) N (%) | GROUP 3 (4–6 YEARS) N (%) | GROUP 4 (7–10 YEARS) N (%) | GROUP 5 (11–14 YEARS) N (%) | GROUP 6 (15–18 YEARS) N (%) | p-VALUE | |
|---|---|---|---|---|---|---|---|---|
| Shape | round-oval | 14 (3%) | 52 (11.2%) | 16 (3.4%) | 5 (1.1%) | 7 (1.5%) | 0 (0.0%) | pa < 0.0001 |
| quadrilateral | 9 (1.9%) | 38 (8.2%) | 51 (11%) | 37 (8%) | 56 (12.1%) | 10 (2.2%) | pa < 0.0001 | |
| triangular | 1 (0.2%) | 4 (0.9%) | 16 (3.4%) | 30 (6.5%) | 41 (8.8%) | 77 (16.6%) | pa < 0.0001 | |
| Margins | biconvex | 15 (3.2%) | 48 (10.3%) | 18 (3.9%) | 10 (2.2%) | 18 (3.9%) | 0 (0.0%) | pb < 0.0001 |
| biconcave | 2 (0.4%) | 2 (0.4%) | 5 (1.1%) | 2 (0.4%) | 6 (1.3%) | 4 (0.9%) | pb = 0.489 | |
| straight | 2 (0.4%) | 18 (3.9%) | 31 (6.7%) | 43 (9.3%) | 54 (11.6%) | 80 (17.2%) | pb < 0.0001 | |
| mixed | 5 (1.1%) | 26 (5.6%) | 29 (6.2%) | 17 (3.7%) | 26 (5.6%) | 3 (0.6%) | pb < 0.0001 | |
| Side predominance | midline | 8 (1.7%) | 39 (8.4%) | 38 (8.2%) | 44 (9.5%) | 61 (13.1%) | 76 (16.4%) | pc < 0.0001 |
| right-sided | 12 (2.6%) | 19 (4.1%) | 9 (1.9%) | 6 (1.3%) | 16 (3.4%) | 2 (0.4%) | pc = 0.002 | |
| left-sided | 4 (0.9%) | 36 (7.8%) | 36 (7.8%) | 22 (4.7%) | 27 (5.8%) | 9 (1.9%) | pc < 0.0001 | |
[i] Abbreviations: mixed margins, a combination of concave and convex, concave and straight, or convex and straight margins;
Data are expressed as number (n) and percentage (%);
Pa – values for comparing each shape between age groups;
Pb – values for comparing each margin between age groups;
pc – values for comparing each side predominance between age groups;
p – values were obtained using the Chi-square test; p – values <0.05 were considered significant.
Table 2
Distribution of the thymic density according to age.
| THYMIC ATTENUATION ASSESSMENT | GROUP 1 (0–12 MONTHS) | GROUP 2 (1–3 YEARS) | GROUP 3 (4–6 YEARS) | GROUP 4 (7–10 YEARS) | GROUP 5 (11–14 YEARS) | GROUP 6 (15–18 YEARS) | P-VALUE | |
|---|---|---|---|---|---|---|---|---|
| Thymic score | Score 1 | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 3 (0.6%) | p = 0.006 |
| Score 2 | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 14 (3.0%) | p < 0.0001 | |
| Score 3 | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 5 (1.1%) | 13 (2.8%) | 38 (8.2%) | p < 0.0001 | |
| Score 4 | 24 (5.2%) | 94 (20.3%) | 83 (17.9%) | 67 (14.4%) | 91 (19.6%) | 32 (6.9%) | p < 0.0001 | |
| CT attenuation values (HU) | Male | 73.7 ± 8.4 (61.2–89.3) | 75.4 ± 11.8 (53.4–104.6) | 73.4 ± 13.0 (22.9–90.2) | 67.1 ± 13.1 (22.1–90.3) | 56.2 ± 19.8 (6–93.2) | 25.0 ± 26.7 (-40.2–71.7) | pa = 0.029 |
| Female | 70.8 ± 10.2 (58.2–81.7) | 74.8 ± 11.8 (51.1–97.5) | 72.4 ± 9.2 (58.1–94.6) | 66.8 ± 13.5 (42.1–88.6) | 63.8 ± 17.6 (20.1–93.5) | 39.2 ± 33.8 (-27.6–98.1) | pb = 0.213 | |
| Total | 73.2 ± 8.6 (58.2–89.3) | 75.2 ± 11.7 (51.1–104.6) | 72.9 ± 11.2 (22.9–94.6) | 67.0 ± 13.2 (22.1–90.3) | 59.9 ± 19.1 (6.0–93.5) | 30.9 ± 30.5 (–40.2–98.1) | pc = 0.002 | |
[i] Abbreviations: Score 0, complete fatty replacement; Score 1, mainly fatty thymus; Score 2, 50% of fatty and 50% of the soft-tissue attenuated thymus; Score 3, mainly soft-tissue attenuated thymus;
Data are expressed as number (n) and percentage (%); mean ± standard deviation (SD), range (minimum to maximum value);
p – values for comparing each thymic score between age groups;
pa – values for comparing CT attenuation values among boys between age groups;
pb – values for comparing CT attenuation values among girls between age groups;
pc – values for comparing CT attenuation values between age groups;
p – values were obtained using the Chi-square test and ANOVA – post hoc Bonferroni test; p – values <0.05 were considered significant.
Figure 3
The graph shows the relationship between the estimated marginal means of the anteroposterior (AP) and transverse diameter of the thymus according to age groups.
Table 3
The mean diameters of the thymic gland according to age and gender.
| THYMIC GLAND DIMENSIONS (MM) | GROUP 1 (0 – 12 MONTHS) | GROUP 2 (1 – 3 YEARS) | GROUP 3 (4 – 6 YEARS) | GROUP 4 (7 – 10 YEARS) | GROUP 5 (11 – 14 YEARS) | GROUP 6 (15 – 18 YEARS) | p-VALUE | |
|---|---|---|---|---|---|---|---|---|
| Right thymic lobe width | M | 22.3 ± 4.8 | 23.0 ± 5.3 | 19.7 ± 4.3 | 19.9 ± 5.4 | 21.2 ± 6.3 | 19.8 ± 5.6 | pa = 0.053 |
| F | 20.7 ± 2.7 | 20.5 ± 4.3 | 19.6 ± 4.0 | 19.7 ± 3.8 | 22.4 ± 6.6 | 18.1 ± 4.8 | pb = 0.448 | |
| T | 22.0 ± 4.5 | 22.1 ± 5.1 | 19.6 ± 4.1 | 19.8 ± 4.8 | 21.8 ± 6.4 | 19.1 ± 5.3 | pc = 0.011 | |
| Right thymic lobe thickness | M | 18.1 ± 7.0 | 19.1 ± 8.2 | 16.1 ± 6.3 | 14.9 ± 6.0 | 14.3 ± 5.2 | 9.5 ± 5.3 | pa < 0.0001 |
| F | 15.3 ± 2.5 | 17.8 ± 5.6 | 17.1 ± 5.0 | 14.8 ± 7.1 | 17.4 ± 8.2 | 8.9 ± 4.2 | pb < 0.0001 | |
| T | 17.6 ± 6.5 | 18.5 ± 7.3 | 16.6 ± 5.7 | 14.9 ± 6.4 | 15.8 ± 7.0 | 9.2 ± 4.9 | pc < 0.0001 | |
| Left thymic lobe width | M | 25.7 ± 6.3 | 27.6 ± 7.7 | 29.2 ± 5.7 | 27.3 ± 5.9 | 27.3 ± 7.9 | 22.9 ± 9.0 | pa = 0.001 |
| F | 23.5 ± 9.4 | 26.9 ± 7.6 | 25.5 ± 7.3 | 27.0 ± 6.9 | 26.5 ± 8.6 | 21.7 ± 8.1 | pb = 0.279 | |
| T | 25.3 ± 6.7 | 27.3 ± 7.6 | 27.3 ± 6.8 | 27.3 ± 7.9 | 26.9 ± 8.3 | 22.4 ± 8.6 | pc < 0.0001 | |
| Left thymic lobe thickness | M | 16.5 ± 5.1 | 17.7 ± 5.4 | 16.0 ± 4.0 | 14.0 ± 4.4 | 13.9 ± 4.9 | 9.8 ± 4.4 | pa < 0.0001 |
| F | 16.7 ± 2.5 | 17.1 ± 4.4 | 17.9 ± 4.2 | 14.1 ± 5.0 | 16.0 ± 6.6 | 10.5 ± 4.3 | pb < 0.0001 | |
| T | 16.5 ± 4.7 | 17.5 ± 5.1 | 17.0 ± 4.2 | 14.0 ± 4.6 | 14.9 ± 5.8 | 10.1 ± 4.4 | pc < 0.0001 | |
| Thymic gland AP diameter | M | 18.4 ± 4.0 | 18.8 ± 4.4 | 16.8 ± 4.1 | 16.2 ± 4.0 | 17.9 ± 5.4 | 17.7 ± 5.0 | pa = 0.283 |
| F | 20.2 ± 3.4 | 16.6 ± 4.8 | 16.4 ± 3.7 | 17.3 ± 4.2 | 17.4 ± 5.3 | 16.4 ± 3.8 | pb = 0.794 | |
| T | 18.7 ± 3.9 | 18.0 ± 4.7 | 16.6 ± 3.9 | 16.6 ± 4.1 | 17.6 ± 5.4 | 17.2 ± 4.5 | pc = 0.750 | |
| Thymic gland transverse diameter | M | 34.6 ± 11.4 | 36.2 ± 10.2 | 32.1 ± 9.3 | 29.0 ± 9.6 | 33.5 ± 13.1 | 18.8 ± 9.0 | pa < 0.0001 |
| F | 32.0 ± 4.9 | 34.9 ± 9.2 | 35.0 ± 8.3 | 29.0 ± 11.2 | 30.8 ± 11.6 | 19.4 ± 7.7 | pb < 0.0001 | |
| T | 34.2 ± 10.5 | 35.7 ± 9.8 | 33.6 ± 8.9 | 29.0 ± 10.1 | 18.8 ± 9.0 | 19.0 ± 8.4 | pc < 0.0001 | |
[i] Abbreviations: AP, anteroposterior
Data are expressed as mean ± standard deviation (SD);
pa – values for comparing each thymic dimension values among boys between age groups;
pb – values for comparing each thymic dimension values among girls between age groups;
pc – values for comparing each thymic dimension values between age groups;
p – values were obtained using the Kruskal – Wallis test; p – values <0.05 were considered significant.