Fetal thymus volume estimation by virtual organ computer-aided analysis in normal pregnancies

Area of Science:

• Fetal Medicine
• Medical Imaging
• Computational Anatomy

Background:

• The thymus, a pyramidal organ, plays a crucial role in fetal immune development.
• Accurate assessment of fetal thymus volume is essential for monitoring normal growth and development.
• Traditional methods for estimating fetal organ volume can be challenging due to complex shapes and dynamic changes.

Purpose of the Study:

• To evaluate the efficacy of virtual organ computer-aided analysis (V-OCA) for estimating fetal thymus volume.
• To assess the relationship between fetal thymus volume and gestational age in normal pregnancies.
• To determine the interobserver and intraobserver variability of V-OCA for thymus volume measurement.

Main Methods:

• Three-dimensional (3D) volume datasets were acquired from 37 normal pregnancies (12-35 weeks' gestation).
• Fetal thymus volume was calculated using V-OCA by two independent examiners.
• 4D sonography and spatiotemporal image correlation were used in a subset of cases to assess cardiac cycle-related volume variations.

Main Results:

• V-OCA successfully identified thymus borders and calculated volume in 77.7% of cases.
• A statistically significant linear growth trend of fetal thymus volume was observed between 12 and 35 weeks' gestation.
• Interobserver and intraobserver variability were not statistically significant, indicating high reproducibility.

Conclusions:

• Virtual organ computer-aided analysis is a feasible method for estimating fetal thymus volume in normal pregnancies.
• Fetal thymus volume demonstrates consistent linear growth throughout the second and third trimesters.
• Minor volume fluctuations during the cardiac cycle are likely due to soft tissue dynamics and do not significantly impact overall volume assessment.