Prenatal Brain MR Imaging: Reference Linear Biometric Centiles between 20 and 24 Gestational Weeks

Abstract

Background and purpose: Evaluation of biometry is a fundamental step in prenatal brain MR imaging. While different studies have reported reference centiles for MR imaging biometric data of fetuses in the late second and third trimesters of gestation, no one has reported them in fetuses in the early second trimester. We report centiles of normal MR imaging linear biometric data of a large cohort of fetal brains within 24 weeks of gestation.

Materials and methods: From the data bases of 2 referral centers of fetal medicine, accounting for 3850 examinations, we retrospectively collected 169 prenatal brain MR imaging examinations of singleton pregnancies, between 20 and 24 weeks of gestational age, with normal brain anatomy at MR imaging and normal postnatal neurologic development. To trace the reference centiles, we used the CG-LMS method.

Results: Reference biometric centiles for the developing structures of the cerebrum, cerebellum, brain stem, and theca were obtained. The overall interassessor agreement was adequate for all measurements.

Conclusions: Reference biometric centiles of the brain structures in fetuses between 20 and 24 weeks of gestational age may be a reliable tool in assessing fetal brain development.

Fig 1.

Vermian CCD (the MR imaging trait with the worst percentage disagreement in accuracy between the 2 assessors). Bland-Altman plot of the interassessor B–A difference versus the mean of the measures made on a single fetus. Dashed lines are the limits of agreement for the B–A difference: Ninety-five percent of these differences are expected to lie within these limits when the agreement between the 2 assessors is perfect.

Fig 2.

Pontine APD (the MR imaging trait with the highest correlation of disagreement in accuracy between the 2 assessors and size of MR imaging trait). Bland-Altman plot of the interassessor B–A difference versus the mean of the measures made on a single fetus. Dashed lines are the limits of agreement for the B–A difference: Ninety-five percent of these differences are expected to lie within these limits when the agreement between the 2 assessors is perfect.

Fig 3.

Reference chart for cerebral FOD growth: a whole set of computed centiles (3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th) with observed values. Females are denoted by light gray dots, males by dark gray dots, and fetuses of sex unknown by white dots.

Fig 4.

Reference chart for cerebral BPD growth: a whole set of computed centiles (3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th) with observed values. Females are denoted by light gray dots, males by dark gray dots, and fetuses of sex unknown by white dots.