Thymic ultrasound. I. Intrathymic anatomy in infants.
BACKGROUND
The gross appearance and echogenicity of the normal thymus have been described, but specific intrathymic anatomy has not been evaluated with imaging.


METHODS
The thymus from a 34-week-gestation stillborn male was examined with ultrasound, and the images were correlated with microscopic findings. Thymic ultrasound was performed in 12 infants without any evidence of thymic abnormality, severe infection, or chronic illness. Images were evaluated focusing on intrathymic parenchymal anatomy and compared to the liver, spleen, and thyroid gland.


RESULTS
In the specimen thymus, ultrasound demonstrated connective-tissue septa as echogenic linear structures. The cortex was relatively hypoechoic, whereas the medulla was echogenic. The blood vessels within the septa were seen as discrete echoes. In vivo ultrasound demonstrated multiple branching echogenic linear structures and foci throughout the parenchyma, representing connective-tissue septa or blood vessels within the septa. The normal thymus was easily differentiated from the liver, spleen, and thyroid glands.


CONCLUSIONS
Ultrasound is capable of demonstrating intrathymic anatomy, including the medulla, cortex, septa, and blood vessels in a fresh specimen. In vivo connective-tissue septa and blood vessels in the thymic parenchyma produce a unique echo pattern.
Han
B K
BK
Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Suh
Y L
YL
Yoon
H K
HK
D002102:Cadaver; D005333:Fetus / Q000033:anatomy & histology; D006801:Humans; D007223:Infant; D008297:Male; D013950:Thymus Gland / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000196:embryology; D018615:Ultrasonography, Doppler, Color / Q000379:methods