Attempt to quantify uterine involution using acoustic radiation force impulse before and after placental delivery.

ABSTRACT

PURPOSE: The aim of the present study was to investigate whether baseline stiffness of the uterine corpus and cervix accurately estimated by acoustic radiation force impulse (AFRI) elastography changed after placental delivery. METHODS: Eleven patients with normal vaginal delivery underwent ARFI elastography before, immediately after, and 1 and 2 h after placental delivery, and the shear wave velocity was measured to determine the stiffness. Each measurement was performed in triplicate to obtain a mean ± SD. RESULTS: The shear wave velocity of the uterine corpus before, immediately after, and 1 and 2 h after placental delivery was 1.81 ± 0.60, 3.04 ± 0.76, 3.12 ± 0.95, and 2.72 ± 0.81 m/s, respectively, and the shear wave velocity of the uterine cervix was 1.35 ± 0.45, 1.87 ± 0.57, 1.68 ± 0.59, and 1.70 ± 0.5 m/s, respectively. The stiffness of the uterine corpus significantly changed over time, although that of the uterine cervix was not significantly altered. The stiffness of the uterine corpus was significantly higher immediately after and 1 and 2 h after placental delivery as compared with that before placental delivery. The uterine corpus had a significantly higher stiffness than the uterine cervix at each of the four time points examined. CONCLUSION: ARFI elastography may be useful to assess uterine involution using the shear wave velocity.