Moderate hypothermia has been demonstrated to be the effective treatment for neonates with hypoxic-ischemic encephalopathy (HIE). However, few studies reveal the actual alterations in physiological parameters (i.e. brain temperature and cerebral blood flow) of neonates undergoing cooling, especially for HIE lesions. Therefore, this project aims to utilize the magnetic resonance imaging (MRI), i.e. MR thermal imaging and phase contrast MRI to measure the changes of these parameters before and during hypothermia; and then make comparisons with the routine nasopharyngeal and rectal temperature. All these would provide in vivo quantitative data for therapeutic evaluation and promote the optimization.

1. Study objects 1.1 Primary object To examine the changes of brain temperature and cerebral blood flow in neonates with HIE before and during (i.e. cooling lasting for 24~36 hr) selective brain cooling.

   1.2 Secondary object To compare the differences in temperature between brain (thalamus and HIE lesions) and nasopharynx and rectum of HIE neonates during the cooling.

2. Methods Prospective observational study; the MR thermal imaging and phase contrast MRI will be used to estimate brain temperature and cerebral blood flow.

Neonates with HIE who fulfilled the moderate hypothermia criteria will be recruited from the neonatal intensive care units. MR scans will be performed twice after informed parental consent. The first scan will be before the hypothermia and the second scan will be during the hypothermia. The first scan will be performed while the neonate is still in the intensive care unit. At the time of the second MR scan, the neonate is still in the intensive care unit, and the neonate in hypothermia group is receiving the brain selective cooling. Sedation would be used if required in these babies.

Inclusion Criteria:

• Neonates in the neonatal intensive care unit who fulfill the hypothermia criteria for treating the hypoxic ischemic encephalopathy and who are scheduled to have an MRI for evaluation of the extent of their injury.
• Parents, clinicians and physician consent to perform evaluation of MRI before and during the hypothermia.

Exclusion Criteria:

• Neonates too unstable to have MRI exam, defined by being more than 40% oxygen on the ventilator.
• Hypothermia treatment interruption caused by potential factors.
• Neonates with central nervous system infection,intracranial hemorrhage and brain parenchyma lesions caused by trauma.

Neonates with hypoxic-ischemic encephalopathy who fulfill the moderate hypothermia criteria