22 feb. 2011 FETAL DTI TRACTOGROPHY IN THE ASSESSMENT OF INTEREMISPHERIC WHITE MATTER TRACTS IN THE CLINICAL SUSPICION OF CALLOSAL DYSGENESIS
Roxana T. Popa-Stanila*, Georgeta Rusu*, D. Muresan**, S. Sfrângeu*, F. Stamatian**
* Department of Radiology at „Iuliu Haiteganu” University of Medicine and Pharmacy Cluj-Napoca
** Department of Obstetrics and Gynecology at “Iuliu Hatieganu” University of Medicine and Pharmacy Cluj-Napoca
Rezumat: Rolul Tractografiei DTI fetale in aprecierea conexiunilor interemisferice in suspiciunea clinică de disgenezie a corpului calos
Tractografia reprezintă o metoda IRM (imagistica prin rezonanta magnetica) de studiere in vivo a micro-arhitecturii substantei albe, evidentiind tracturile neuronale si conexiunile cu regiunile corticale si subcorticale. Exista inca multiple provocari de depasit pentru a obtine achizitii DTI (diffusion tensor imaging) de calitate la nivelul creierului fetal, insa atunci cand este posibil, reconstructiile tractografice, alaturi de secventele morfologice conventionale, pot imbunatati diagnosticul precoce al malformatiilor cerebrale fetale, ca si agenezia corpului calos (ACC).
Material si metoda: S-a efectuat IRM fetal in camp magnetic de 3T la 7 cazuri cu suspiciune ecografica de ACC. La toate cazurile s-au achizitionat secventele morfologice conventionale si secventa DTI (25 directii de codare). Reconstructiile tractografice la nivelul corpului calos au fost calitativ satisfacatoare la 4 pacienti.Acestea au fost comparate cu tractografiile normale ale unor feti investigati pentru patologie abdominala.Toate cazurile au fost confirmate postnatal ecografic sau prin IRM.
Rezultate: IRM a relevat doua cazuri de ACC partiala, un caz de ventriculomegalie asimetrica cu compresia posterioara a CC si un caz de ventriculomegalie asociata altor malformatii cerebrale. In 3 din cele 4 cazuri reconstructiile tractografice au fost utile in estimarea integritatii corpului calos, dovedind prezenta de fibre nervoase interemisferice, dificil de vizualizat pe imaginile conventionale.
Concluzii: Reconstructiile tractografice la nivelul creierului fetal pot aduce informatii diagnostice suplimentare in suspiciunile de disgeneza a corpului calos. Secventa DTI ar trebui luata in considerare ca si secventa complementara protocolului de baza de IRM fetal in malformatiile cerebrale.
Abstract
Magnetic resonance (MR) diffusion tensor imaging (DTI) tractogrophyis an imaging tool that allows in vivo study of the white matter micro-architature, highlighting neural tracts and cortical and subcortical connections. Fetal motion is the main challenge to overcome in order to obtain a good quality DTI sequence, but when possible, the tractographic reconstructions combined with conventional morphological MRI sequences may improve the early diagnosis of fetal corpus callosum (CC) dysgenesis.
Materials and methods: Fetal MRI was performed on a 3T superconducting unit in 7 cases with ultrasonographic suspicion of CC dysgenesis. DTI and conventional morphological MR sequences were acquired in all cases. Tractographic reconstructions at the level of the CC were qualitatively satisfactory in 4 cases. The control group, consisted of fetuses of similar gestational age, with MRI indication for abdominal pathology, and normal cerebral development. All cases were confirmed by postnatal ultrasound or MRI.
Results: Fetal MRI revealed partial agenesis of the CC in 2 cases, posterior compression of the CC in a case of asymmetric ventriculomegaly and a thin CC associated with other cerebral malformations. In 3 of the 4 cases the tractographic reconstructions were useful in predicting the integrity of the corpus callosum, proving the presence of interhemisphericwhite matter tracts, otherwise difficult to detect on conventional images.
Conclusion: Fetal MR tractography can provide additional information with diagnostic value, in cases of suspected CC dysgenesis. DTI should be considered as a complementary sequence to the fetal MRI protocol for cerebral malformations.
Keywords: diagnostic prenatal, imagistica prin rezonanta magnetica, imagistica prin tensor de difuzie, tractografie, fetal, corp calos