In general, the more heavily the images are T1 weighted the higher the relative SI of the cortex ( Fig. 4.1) and the more heavily they are T2 weighted, as seen with the fast spin echo (FSE) sequence ( Fig. 4.3), the lower the relative SI. The signal intensity (SI) of the cortex is high on T1 weighted (T1W) By 38 weeks all the sulci are formed though they become deeper over the following few weeks1 The brain of the term (37–42 weeks) infant is similar to that of the adult in terms of its cortical folding. MR imaging of the brain in the term infant: conventional T1 and T2 weighted sequences THE CORTEX The slice thickness we use is 4–6mm with no slice gap.Īn excellent review of different pulse sequences and their relative merits in the pediatric context is given by Barkovich 8. Details of the sequences used on the different systems at different ages are given in Table 4.1. These differences must be taken into account when interpreting images. This makes the appearance of images, particularly the basal ganglia, thalami and internal capsule, different from some published data. Our MR scans are not angled as steeply as is usual for computed tomography (CT). After term, the neonatal unit magnet cannot be used as the bore is too small 57. All three scanners are used for imaging infants up to term. For imaging and multinuclear spectroscopy we have a 1.5 Tesla Picker Eclipse system. We have a 1 Tesla Picker HPQ Vista/Plus system and a 1 Tesla novel short small bore system which is situated in the neonatal intensive care unit. Pulse sequences used by our own group for imaging neonates and young infants Centers must determine normal appearances for different ages on their own system. The introduction of new sequences often means that new norms need to be established. A large number of infants need to be studied with different strength magnets and using different sequences to fully appreciate the range of normal appearances 4–8, The technique has made it possible to see in minute detail changes in cortical folding, involution of the germinal layer, premyelination changes within white matter, myelination, iron deposition, and the growth of different regions of the brain that is not possible with computed tomography or ultrasound.Įstablishing normality is especially difficult because the appearance of the normal brain is changing almost weekly. Magnetic resonance (MR) imaging of the infant brain has given an enormous insight into the maturational processes that take place after birth. Observations of other areas of the brain seen on MR brain scans from term to years.MR changes in the cerebrum, brain stem and cerebellum occuring after term:Ĭonventional T1 and T2 weighted sequences.Diffusion weighted imaging of the neonatal brain. MR imaging of the brain in the term infant: conventional T1 and T2 weighted sequences.Pulse sequences used by our group for imaging neonates and young infants.
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