Hypoxic-ischemic brain injury in the neonatal rat model: relationship between lesion size at early MR imaging and irreversible infarction.
OBJECTIVE
By using a neonatal rat hypoxia-ischemia (HI) model, we studied the relationship between lesion volume-measured by diffusion-weighted imaging (DWI) and T2-weighted imaging (T2WI) at an early time point-and irreversible infarct volume. We also evaluated the optimal apparent diffusion coefficient (ADC) threshold that provides the best correlation with irreversible infarct size.


METHODS
Twenty-three neonatal rats underwent right common carotid artery ligation and hypoxia. MR imaging was performed 1-2 hours post-HI by using DWI and T2WI and at day 4 post-HI by using T2WI. Lesion volumes relative to whole brain (%LV) were measured on ADC maps by using different relative ADC thresholds 60%-80% of mean contralateral ADC and T2WI. Pearson correlation and multiple linear regression analysis were used to study the relationships between ln(%LV) at MR imaging and %LV at histopathology.


RESULTS
At 1-2 hours post-HI, all lesion volume measurements on DWI were significantly correlated with the infarct volume on histopathology, with the best correlation attained at the 80% ADC threshold (r = 0.738; P < .001). The estimated regression formula was %LV on histopathology = 20.60 + 3.33 ln(%LV on 80% ADC threshold) (adjusted R(2) = 0.523; P < .001). Lesion volume at 1-2 hours post-HI tended to underestimate the final infarct volume.


CONCLUSIONS
Early post-HI MR imaging by using DWI correlates moderately well with the size of irreversible infarct, especially when measured by using a relative ADC threshold of 80% mean contralateral ADC.
Wang
Y
Y
Department of Diagnostic Radiology University of Hong Kong, Hong Kong, China.
Cheung
P-T
PT
Shen
G X
GX
Wu
E X
EX
Cao
G
G
Bart
I
I
Wong
W H S
WH
Khong
P-L
PL
D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000473:pathology*; D002544:Cerebral Infarction / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging; D020925:Hypoxia-Ischemia, Brain / Q000150:complications / Q000175:diagnosis* / Q000473:pathology; D008279:Magnetic Resonance Imaging; D051381:Rats; D017207:Rats, Sprague-Dawley