The document provides a detailed methodology for imaging the fetal corpus callosum using ultrasound techniques. It emphasizes the ideal gestational age for evaluation and describes various approaches such as transabdominal and transvaginal imaging. Additionally, it discusses the use of 3D assessment and Doppler imaging to enhance the visualization of the corpus callosum and associated structures.

1. How to image the fetal corpus
callosum
Aly Youssef, Tullio Ghi, Gianluigi Pilu
Department of Obstetrics and Gynecology
University of Bologna
Italy

2. How to: image the fetal corpus callosum
Indication: ultrasonographic evaluation of the fetal corpus
callosum
When? ideal gestational age is ≥ 20 weeks
Machine settings: routine obstetric anomaly scan
Ideal fetal lie: on back or one side; the transabdominal
approach is facilitated by a breech or transverse
presentation; the transvaginal approach provides excellent
resolution but requires a cephalic presentation

3. Acoustic window: 3D images of the fetal skull (a,b) demonstrate the wide
acoustic windows provided by the frontal suture (1), bregmatic fontanel (2) and
sagittal suture (3). By aligning the acoustic beam with these windows, excellent
resolution of cerebral structures including the corpus callosum is possible (c). As
the acoustic window runs along the entire calvarium, the corpus callosum can be
imaged by anterior, superior and posterior approaches (arrows).
a b c

4. Fetal profile approach
• Obtain a mid-sagittal fetal profile view (a)
• Move the transducer cranially and angulate in a
caudal direction in order to use the acoustic
window of the anterior fontanel and the frontal
suture
• Slight lateral movements of the probe will be
required to locate the mid-sagittal plane thus
demonstrating the corpus callosum (b, highlighted
in yellow).
a
b

5. Coronal approach
• Obtain a coronal section of the anterior horns of
the lateral ventricles
• Move the probe to orientate the cavum septi
pellucidi (arrow) vertically (a).
• Rotate the transducer 90°
obtaining a midline
brain section and visualizing the corpus callosum
(b, highlighted in yellow).
a
b

6. Pericallosal artery
• The pericallosal artery (arrows) is
demonstrated by color Doppler in the mid-
sagittal view
• Identification of the pericallosal artery
highlights the presence of the corpus callosum
• Appearance of the pericallosal artery in a
normal fetus at 20 weeks’ gestation (a)
• Partial agenesis of the corpus callosum
inferred by a partial Doppler signal from the
pericallosal artery where the presence of the
corpus callosum was difficult to assess in b-
mode (b)
a
b

7. 3D assessment of the corpus callosum
Acquisition plane: the standard BPD axial plane

8. 3D assessment of the corpus callosum
•Acquire a 3D volume
•The multiplanar mode displays the axial (A), coronal (B), and sagittal (C) planes
•Position the intersection point of the planes in the cavum septi pellucidi
A
C
B

9. 3D assessment of the corpus callosum
•The arrows indicate the direction of the rotation required to align the midline with the C-plane
A
C
B

10. 3D assessment of the corpus callosum
•Once the A- and B-planes have been rotated so that the midline is aligned with the C-plane, a mid-
sagittal view of the brain is demonstrated, in which it is possible to recognize the comma-shaped
anechoic complex formed by the combination of the corpus callosum (CC) and the cavum septi
pellucidi (CSP)
A
C
B
CC-CSPCC-CSP

11. 3D assessment of the corpus callosum
•Activate the volume contrast imaging (VCI) 3D mode in order to improve the image
quality
B
A
C
B

12. 3D assessment of the corpus callosum
•The intersection point may need to be moved towards either wall of the CSP to
optimize the image of the CC
A
C
B

13. 3D assessment of the corpus callosum
•Another simple 3D technique is the Omniview-VCI (GE Healthcare)
•Following 3D volume acquisition, activation of the OmniView task
•Draw a line horizontally on the midline across the cavum septi pellucidi
•Automatically, a reconstructed mid-sagittal plane is displayed on the right side of the
screen
CC-CSPCC-CSP
A B