Vascular dementia (VaD) is a relatively heterogeneous disease with various vascular etiologies and has become the second most common cause of dementia in elderly people. With recent advances in embolic stroke prevention, subcortical ischemic vascular dementia (SIVD) has become one of the most common types of VaD. Early detection and management of SIVD in the elderly is critical. Previous studies have proven that subcortical ischemic lesions may cause general cognitive dysfunction and poor physical health. Multi-TI arterial spin-labeling (mTI-ASL) MR sequences measure the perfusion with multiple transit times after labeling and can provide timing information such as bolus arrival time (BAT) and more accurately quantify regional cerebral blood flow (CBF). This study investigates the feasibility of mTI-ASL in detecting the difference in cerebral perfusion between AD and SIVD patients, especially in BAT and CBF.Nineteen SIVD subjects (7 males, mean age 66.7 years), twelve AD subjects (5 males, mean age 65.6 years), and ten healthy controls (HCs) (4 males, mean age 62.5 years) were included in the study. The diagnosis of SIVD was based on a modified version of criteria from the National Institute of Neurological Disorders and Stroke and the Association Internationale pour Ia Recherche' et l'Enseignement en Neurosciences (NINDS–AIREN). ¹ The AD sample met the NINCDS-ADRDA criteria for probable AD of mild–moderate severity. ² Participants were scanned using a MAGNETOM Skyra 3T MR scanner (Siemens Healthcare, Erlangen, Germany) with a 32-channel head coil. The mTI-ASL images were acquired with a prototype sequence with the following parameters: TR/TE = 4600/22 ms, FOV = 220 × 220 mm², iPAT mode = GRAPPA (PE) 2, slice thickness = 4 mm, voxel size = 3.4 × 3.4 × 4.0 mm³, 20 slices, bolus length = 700 ms, 16 TIs from 480 to 4080 ms, and total acquisition time = 5:09 min including an M0 scan. The Buxton model with a non-linear fit to CBF and BAT was used for quantification. The group analysis of BAT and CBF were post-processed with SPM8 (Wellcome Department of Cognitive Neurology, London, UK).Voxel-based analysis (VBA) was performed to compare the AD, SIVD and HC groups. Age, sex, education, Mini Mental State Examination (MMSE) scores and gray matter volume were all considered as covariant factors. Compared to HCs, the CBF decreased in the bilateral frontal lobe of AD patients including in the left superior frontal gyrus, middle frontal gyrus, Brodmann area 10 (anterior prefrontal cortex) and right superior frontal gyrus. The BAT demonstrated prolonged characters in corresponding decreased CBF areas compared to HCs. (Figure 1) There was no significant difference in CBF between SIVD and HCs, and between SIVD and AD patients. However, significant prolongation was detected in Brodmann area 19 (associative visual cortex) of BAT in SIVD patients compared to HCs. In comparison between AD and SIVD patients, BAT was significantly prolonged in the bilateral frontal lobe, left dorsal thalamus and right parietal lobe in AD patients. (Figure 2)Single-TI ASL (sTI-ASL) experiments cannot detect the highest CBF for all brain areas, especially for patients who may have prolonged artery transit time (ATT) compared to normal subjects. So the decrease of CBF and increase of ATT show low CBF in the sTI-ASL results that lead to the underestimation of CBF. The mTI-ASL could provide both quantitative BAT (ATT) and CBF, so that we learn more about the mechanism and how to treat AD and SIVD.The CBF decreased more in the frontal lobe of AD patients compared with healthy controls, and the BAT maps demonstrated an opposite tendency compared to CBF. The mTI-ASL could be used to evaluate the cerebral perfusion of AD and SIVD patients both in CBF and BAT and could detect perfusion deficits more accurately and efficiently compared with CBF.