Application of real-time shear wave elastography in neonatal thymus

To investigate the application of real-time shear wave elastography (SWE) in neonatal thymus.

A total of 143 neonates were selected, including 77 males and 66 females. They were divided into preterm group (76 cases) and full-term group (67 cases) according to gestational age. First, the body length, weight, body surface area (BSA), and body mass index (BMI) were obtained for all participants. All subjects underwent routine ultrasound examination to obtain the cranio-caudal diameter (CC) (defined as the maximum dimension between the superior and inferior poles in the sagittal plane of both thymic lobes), transverse diameter (Width) (defined as the sum of the maximum lateral dimensions of both lobes in the transverse plane), and antero-posterior diameter (AP) (defined as the maximum dimension between theanterior and posterior poles in the transverse plane of both thymic lobes). The thymic volume was then calculated using the formula: Volume = Width*AP*CC*0.5. Then the imaging mode was switched to SWE to record the Elastography Quality Index (EQI) mean, maximum, median values of Young's modulus. The difference of elasticity between the two groups and between the sexes was compared. The 95% medical reference range of thymus elasticity was obtained.

Body length, body weight, BSA, BMI, thymic Width, AP, CC and volume in preterm infants were all lower than those in term infants (P < 0.05). There were no significant difference in the thymic EQI mean, median and maximum value between the two groups (P > 0.05). As for body length, weight, surface area, BMI; thymic Width, AP, CC and volume; the thymic EQI mean, median and maximum value, there was no significant difference between the males and females (P > 0.05). The gestational age, BMI and thymic volume were not correlated with the thymic EQI mean, median and maximum (P > 0.05). The average gestational age of neonates was positively correlated with thymic volume, BSA and body weight (r₁ = 0.595; r₂ = 0.887; r₃ = 0.783; r₄ = 0.885, P < 0.05). The thymic volume was positively correlated with BSA and body weight (r₁ = 0.655; r₂ = 0.680, P < 0.05). The 95% Reference ranges of thymic EQI mean, median and maximum were 6.800-21.100 kPa, 6.588-20.240 kPa and 13.620-45.660 kPa, respectively.

Real-time shear wave elastography can obtain the normal elastic value of healthy pediatric thymus, distinguish the healthy and pathological state, and provide the normal reference range of shear Young's modulus value for clinical and follow-up scientific research.