Jennifer C Alphonse BSC, Presenter: Nothing to Disclose

Andrew McLennan MBBS, FRANZC, Abstract Co-Author: Nothing to Disclose

Philip J Schluter PhD, Abstract Co-Author: Nothing to Disclose

Jennifer M Cox PhD, Abstract Co-Author: Nothing to Disclose

Jillian L Clarke BSC, MEd, Abstract Co-Author: Nothing to Disclose

To investigate the utility of FMF angle screening in routine assessment at 11-14 weeks gestation. To compare the accuracy of 2D (real-time) FMF angle measurement with 3D (off-line) volume reconstruction.

Adapting Sonek et al's methodology, a single operator collected 2D images and 3D volumes from 166 single chromosomally normal fetuses at 11-14 weeks gestation in consenting participants, using a GE E8 Voluson Expert ultrasound machine. The FMF angle was measured on a frozen 2D image in an appropriate plane and, after a delay of at least 48 hours, was measured from the 3D volume using the 4D View (GE) off-line measurement program.  

The FMF angle was successfully visualized in 147/166 subjects (89%). The mean difference was -1.28°. The angle reduces with advancing crown rump length. In 90% of volumes with paired measurements, intra-observer difference was less than 5°. The difference between the paired 3D and 2D measurements was less than 8° in 95% of cases. This difference reduced substantially after an initial learning curve of 40 cases. Data collection is continuing.

FMF angle measurement is repeatable and can be incorporated into routine 11-14 week screening without lengthening the examination. Fetal position precludes accurate measurement in a consistent number. With appropriate training and experience, 2D measurement of the FMF angle is as accurate as 3D volume reconstruction.

In 2005 the FASTER trial found screening programs can detect 88% of Down Syndrome (DS) fetuses in pregnant women. Sonek et.al (2007) found that measuring FMF may improve current screening for DS.

Alphonse, J, McLennan, A, Schluter, P, Cox, J, Clarke, J, Fetal Frontomaxillary Facial (FMF) Angle Measurement in the First Trimester.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8005885.html