MICROPET SCANNING WITHIN THE NEONATAL INTENSIVE CARE UNIT (NICU): FEASIBILITY STUDIES

Objectives: In newborns, PET studies are difficult to perform because of difficulty in transporting sick infants. Furthermore, the spatial resolution of clinical PET scanners is suboptimal for newborns. We installed and tested the Focus 220 animal microPET scanner (Concorde Microsystems, Knoxville, TN) in our NICU.

Methods: We have performed PET studies of cerebral glucose metabolism, GABA-A receptor binding, and protein synthesis in over 30 infants (34 weeks gestational age to 8 months postnatal) with various neurological conditions. With a patient opening of 22cm and an axial field-of view of 8cm, this scanner can also be used in larger infants <15kg. All infants were bundled with blankets and fastened to the bed with velcro straps. Vital signs were monitored.

Results: Our preliminary studies documented the high spatial resolution (<2mm full-width-at-half-maximum) of the microPET scanner. Various thalamic and brainstem nuclei were identified. We confirmed the very early glucose functional maturation of sensorimotor cortex, thalamus, brainstem, cerebellar vermis, and limbic structures such as amygdala, even in premies. Ictal PET scans in neonates showed hypermetabolism restricted to the cerebral cortex, whereas interictal hypometabolism was of less localization value in newborns because of the normally low glucose metabolic rates in cerebral cortex. Heterotopic malformations appeared as areas of increased glucose metabolism with nodular or band appearance in the lower cortical layers or in white matter. The high 11C-flumazenil binding in basal ganglia, thalamus and brainstem of premature infants was dramatically different from low binding in older children and adults, and may indicate a transient overexpression of GABA-A receptors in these structures during development.

Conclusion: The Focus 220 microPET scanner is a powerful new approach in the study of neonatal neurological disorders and can be used to measure a variety of physiological and biochemical processes not only in brain, but also in other organs.