Introduction to Fetal Brain MRI
- Magnetic Resonance Imaging (MRI) provides superior soft tissue resolution, critical for detailed visualization of fetal brain structure.
- Fetal MRI has significantly advanced the field of fetal neurology by offering three-dimensional resolution, multiplanar imaging capabilities, and robust image quality.
- Ultrafast MRI sequences minimize motion artifacts caused by spontaneous fetal movements and maternal breathing, enabling high-quality imaging without sedation.
Common MRI Sequences and Applications
- T2-weighted sequences: Provide excellent contrast between tissue and cerebrospinal fluid, essential for assessing cortical development.
- T1-weighted inversion recovery and proton density sequences: Useful for detecting hyperintense lesions such as haemorrhage, lipoma, subependymal nodules, calcifications, and evaluating myelination patterns. However, these sequences are limited by motion artifact, especially before the end of the second trimester.
- T2*-weighted and susceptibility-weighted MRI: Sensitive to blood, blood breakdown products, and calcifications, crucial for identifying acquired disruptive lesions.
- Diffusion-weighted imaging (DWI): Identifies focal areas of acute ischemic injury and delayed brain development, valuable in high-risk pregnancies (e.g., small-for-gestational-age fetuses).
- Diffusion tensor imaging (DTI): Evaluates white matter microstructural architecture, axonal growth, and connectivity, though fetal motion currently limits routine clinical use.
- Proton Magnetic Resonance Spectroscopy (1H-MRS): Measures brain metabolites like N-acetyl aspartate (neuronal integrity), creatine (energy metabolism), choline (membrane turnover), and lactate (anaerobic metabolism).
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