Diffusion-weighted imaging detects early brain injury after hypothermic circulatory arrest in pigs.

OBJECTIVES: Cerebral injury is a complication of surgery with deep hypothermic circulatory arrest (DHCA). This study aimed to evaluate diffusion-weighted imaging (DWI) for the early detection of brain injury after DHCA in an animal model.

METHODS: Twelve healthy, adult, male miniature pigs were randomly divided into the DHCA (to receive DHCA; n = 6) and the control (sham surgery under anaesthesia; n = 6) groups. All animals received DWI, T1-weighted imaging (T1WI) and T2WI the day before surgery, 7 h postoperatively and 24 h postoperatively. Histopathological evaluation of the brain tissues was performed in the DHCA group using the Fluoro-Jade C staining to detect neuronal degeneration, the Nissl staining to show neuronal morphology and the TUNEL assay for apoptosis. The Cohen's kappa coefficient was used to compare the results of DWI with those of the histopathological evaluation.

RESULTS: All animals survived surgery. In the control group, no new focal brain lesions were detected by postoperative DWI, T1WI or T2WI. In the DHCA group, new focal brain lesions were detected as early as 7 h postoperatively by DWI but not T1WI or T2WI. All three imaging sequences revealed abnormalities 24 h after surgery. In sections from areas showing abnormalities on DWI, the Fluoro-Jade C staining detected neuronal degeneration, the Nissl staining showed morphological abnormalities and the TUNEL assay demonstrated apoptotic cells. The Cohen's kappa statistics showed agreement between DWI findings and the results of all 3 histopathological examinations (TUNEL: kappa = 0.553; Nissl: kappa = 0.652; Fluoro-Jade C: kappa = 0.778; all P < 0.001).

CONCLUSIONS: DWI is superior to T1WI or T2WI for the early detection of neurological lesions after DHCA in pigs.