Table 1.

Imaging findings and time frame for assessment of abnormalities for each MRI modality.

Pattern of Injury	Imaging Modality	Imaging Findings	Time Frame of Abnormalities
WM/WS	T1WI/T2WI	Abnormal signal intensity in the white matter of the watershed areas of the cerebral arteries, and also the overlying cortex in severely affected infants. T2WI may show loss of gray-white matter differentiation at the cortex.	Inconspicuous or subtle abnormalities in the first days, which become gradually more apparent by the latter half of the first week following the insult. MRI obtained beyond 1 month can show cortical thinning, white matter volume loss, cysts and gliosis of the cortex and white matter.
	DWI	High signal intensity on isotropic DWI with low ADC values in the affected areas.	Abnormalities peak at 3–5 days after the insult. Pseudo-normalization occurs after approximately 11–12 days for infants treated with therapeutic hypothermia, and 6–8 days in non-cooled infants.
	1H-MRS	Increased lactate and decreased NAA in the affected white matter.	Lactate in general increases <24 h and subsequently normalizes by the end of the first week, but persistent elevation has been reported. 1 NAA declines <24 h and remains low during the first 2 weeks after the insult, although some studies have reported that NAA levels do not significantly diminish until approximately 48 h after the insult. 2
	SWI	Prominent hypo-intense veins, low signal intensity at the site of hemorrhagic lesions.	Prominent hypo-intense veins have been observed as early as 18 h after birth, but current literature is limited. Low signal intensity at the site of hemorrhagic lesions is seen immediately and can persists for many months.
BGT	T1WI/T2WI	Abnormal signal intensity in the basal ganglia, thalami and the perirolandic cortex. Absence of a normal high-signal intensity of the PLIC.	Inconspicuous or subtle abnormalities in the first days, which become gradually more apparent by the latter half of the first week following the insult. MRI obtained beyond 1 month can show volume loss, cysts, gliosis and impaired myelination of the central gray matter and perirolandic cortex.
	DWI	High signal intensity on isotropic DWI with low ADC values in affected areas.	Abnormalities peak at 3–5 days after the insult. Pseudo-normalization occurs after approximately 11–12 days for infants treated with therapeutic hypothermia, and 6–8 days in non-cooled infants.
	1H-MRS	Increased lactate and decreased NAA in basal ganglia and thalami.	Lactate in general increases <24 h and subsequently normalizes by the end of the first week, but persistent elevation has been reported. 1 NAA declines <24 h and remains low during the first 2 weeks after the insult, although some studies have reported that NAA levels do not significantly diminish until approximately 48 h after the insult. 2
	SWI	Prominent hypo-intense veins	Prominent hypo-intense veins have been observed as early as 18 h after birth, but current literature is limited.

¹—Based on previous work by Barkovich et al. [88]; ²—Reported by Barkovich et al. [92] and Penrice et al. [93]. ADC: apparent diffusion coefficient; BGT: basal ganglia and thalami; DWI: diffusion-weighted imaging; 1H-MRS: proton magnetic resonance spectroscopy; MRI: magnetic resonance imaging; NAA: N-acetylaspartate; PLIC: posterior limb of the internal capsule; SWI: susceptibility weighted imaging; T1WI: T1-weighted imaging; T2WI: T2-weighted imaging; WM/WS: white matter/watershed.