Malek Tebache MD, Presenter: Nothing to Disclose

Laurent Collignon MD, Abstract Co-Author: Nothing to Disclose

Pierre Defrere MD, Abstract Co-Author: Nothing to Disclose

Léon Rausin MD, Abstract Co-Author: Nothing to Disclose

Jean-Pierre Schaaps MD, PhD, Abstract Co-Author: Nothing to Disclose

Linda Tebache BSc, Abstract Co-Author: Nothing to Disclose

when a skeletal fetal disease is suspected with ultrasonography (US), the complementary mean of investigation is radiography. Currently 2 or 3 plain films are necessary, with a radiation exposure of at least 3 to 5 mGy. The result is often disappointing. We describe a method using multidetector computed tomography (MDCT) achieving low dose of irradiation.

Imaging was performed on a 4-MDCT : 120 kVp, 35 mAs, rotation time of 0,5 sec, 4 x 1 mm, pitch 0,9. A preliminary study is conducted to estimate the absorbed dose to fetal location. We used an anthropomorphic phantom (Rando-Alderson model) and thermoluminescence dosimeters. 35 pregnant patients were examined in the third trimester after informed consent. They were selected in a cohort of 21000 morphologic US performed during a 51 months period. In each case a skeletal developmental disorder was suspected with US. Mean gestational age was 26,5 weeks. No sedation is used. The MDCT raw data set is used to produce a stack of 2mm axial slices. Diagnostic accuracy of native slices, MPVR, MIP, 3D SSD and VRT were compared with US findings. Our conclusions were confronted to final diagnosis.

CTDIvol averaged 5 mGy; that is to say an irradiation dose equivalent to a CT-scanner pelvimetry. Native slices alone were inconclusive. We found thick MIP or 3D SSD reconstructions the best techniques. Fetal findings included: Klippel-Trenaunay syndrome, thanatophoric dysplasia, chondrodysplasia punctata, campomelic dysplasia, type 2 osteogenesis imperfecta, achondroplasia, achondrogenesis, spondylothoracic dysplasia, lower mesodermal defect, vertebral dysplasia, arthrogryposis and IUGR (idiopathic intrauterine growth retardation). CT results have been rated very good (n=18), good (n=12), average (n=4) and mediocre (n=1). CT-scanner brought valuable complementary informations in 16 patients (46 %).

Skeletal disorders still remain a challenge for fetal US. MDCT is a low radiating technique competitive with plain films, acquiring volumes of high diagnostic quality.

We suggest that multiple row detector CT scanner provides an interesting method for the workup of selected fetuses with suspected skeletal disease.

Tebache, M, Collignon, L, Defrere, P, Rausin, L, Schaaps, J, Tebache, L, CT-Scanner Approach in the Assessment of Fetal Skeletal Diseases.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5011978.html