ABSTRACT NUMBER: ESOC2026A2341 THE ASSOCIATION BETWEEN NET WATER UPTAKE ON NON-CONTRAST CT AND FOLLOW-UP MRI APPARENT DIFFUSION COEFFICIENT VALUES IN LATE-WINDOW ISCHEMIC STROKE PATIENTS

Abstract Background and aims Net water uptake (NWU) on non-contrast CT (NCCT) may possibly quantify ischemic core and predict follow-up infarct volume (FIV). Its association with diffusion-weighted MRI (DWI), where fixed apparent diffusion coefficient (ADC) thresholds are used to define FIV, remains unclear. We investigated the correlation between baseline NCCT NWU and ADC values at 24h in late-window ischemic stroke patients with large-vessel occlusion treated with or without endovascular therapy (EVT). Methods We included ischemic stroke patients from the MR CLEAN-LATE trial with available baseline NCCT and follow-up 24h DWI. Patients with prior ischemic stroke were excluded. Manual segmentation was performed on co-registered NCCT and 24h DWI. FIV was defined with an ADC threshold <620*10-6mm2/s. NWU was calculated as: NWU(%)=(1-(median density lesion)/(median density mirror))*100. NWU was the variable of interest in two linear regression models: (1) with the corresponding 24h median ADC values as outcome, adjusted for collateral grade and symptom onset-to-door time; and (2) with NIHSS at 5–7 days as outcome, adjusted for collateral grade, symptom onset-to-door time, FIV, intracranial hemorrhage, and occlusion location. Results Ninety-four patients were included. Mean NWU was 13.8% (SD=4.9). Mean ADC values were 659*10-6mm2/s (SD=185*10-6) in non-EVT patients versus 782*10-6mm2/s (SD=109*10-6) in EVT-patients. Higher NWU was associated with higher 24h ADC values and follow-up NIHSS, although not statistically significant (12.7 [-2.4-27.9] and 0.16 [-0.07- 0.39] respectively). Conclusions Higher baseline NWU trends with higher 24h ADC values and higher follow-up NIHSS, suggesting that NWU may potentially be an explanatory factor for neurological outcome. Conflict of interest Ching Khan: nothing to disclose. Bob Roozenbeek: nothing to disclose. Bart Emmer: nothing to disclose. Robert van Oostenbrugge: nothing to disclose. Wim van Zwam: nothing to disclose. Aad van der Lugt: nothing to disclose. Daniel Bos: nothing to disclose.