Congenital Hyperinsulinism (HI) is a disorder of insulin secretion that causes profound hypoglycemia leading to significant morbidity. It is the most common form of persistent neonatal hypoglycemia, and the most dangerous. Inappropriate insulin secretion causes not only hypoglycemia but also inability to release free fatty acids from adipose tissue and inability to release glycogen from the liver. Hence the brain is deprived of all the major fuel sources (glucose, beta-hydroxybutyrate and lactate) for energy thus leading to the high incidence of brain damage. In up to 50% of cases of congenital hyperinsulinism, medical therapy fails and surgical resection of the pancreas is necessary. Previous techniques developed to differentiate those patients with focal HI in whom surgery could result in a cure are very invasive and put the infants at risk for hypoglycemic brain damage or arterial thrombosis.