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Abstract
The aim of this essay is to assess the role of ultrasound and novel MR imaging techniques in diagnosis of fetal intracranial malformations.
Ultrasonography is the imaging modality used for routine prenatal screening, mainly because it is relatively inexpensive, readily available, free of motion artifacts, and easy to handle and perform repeatedly. The capability of studying blood flow by using Doppler imaging is a unique feature of ultrasonography. While considerable anatomical information may be gained from ultrasound in the first trimester, the most practical time for routine prenatal ultrasound in the screening for fetal anomalies is between 18 and 22 weeks. At this gestation, the intracranial anatomy is sufficiently developed to permit identification of many major malformations, although it must be remembered that some significant
anomalies may not be apparent at this stage, e.g., agenesis of the corpus callosum (not before 18 weeks) and Dandy-Walker malformation variants. The low tissue contrast and small viewing field available with ultrasonography limit it as a definitive prenatal diagnostic tool,
particularly for clinical conditions such as complex fetal CNS anomalies.
In addition, it must be remembered that some structural anomalies involving myelination, migration, or cortical folding defects are not amenable to ultrasound detection, here comes the
role of fetal MRI.