Comparing use of an artery in the wrist to an artery in the groin to access the blood vessels leading to the brain for cerebral angiography (visualising blood flow in the brain)

INTERVENTION: Permuted block randomization will be performed prior to commencing the study using a block size of 4 subjects (with 2 treatment arms: radial and femoral) using the statistical software StatsDirect Version 3.1.22 (Cambridge, UK; www.statsdirect.com). The results of the randomization will then be used to create a series of sealed envelopes labelled on the front with the study ID number, and inside containing a sheet of paper outlining the group allocation (RADIAL or FEMORAL), as well as the subject data collection sheet pre‐filled with the subject ID as the only patient identifier. These envelopes will be placed in numerical order (1 at top, 80 at bottom; 4 additional envelopes created in case of patients who are randomized and then withdraw from the study after group allocation but prior to the procedure). The box containing these envelopes will be kept in the secure area of the angiography suite control room in the Department of Neuroradiology, TWH (Level 3 East Wing). For adult patients referred to the Department of Neuroradiology for diagnostic cerebral angiography, informed written consent for participation in the trial will be obtained from the patient or their next of kin (where applicable) by one of the co‐investigators. An Allen’s test will be performed on the right wrist/hand after obtaining consent but prior to randomization, to determine suitability for radial artery access. If, upon release of pressure from the ulnar artery and opening of the hand, there is not adequate skin reperfusion (restoration of redness) in the index finger within 10 seconds, the patient will be deemed unsuitable for radial artery access and excluded from the study analysis prior to randomization. Randomization will then be undertaken by the interventionist selecting the top sealed randomization envelope from the box of envelopes in the angiography suite control room. The patient will be notified of CONDITION: Neurovascular diseases ; Circulatory System PRIMARY OUTCOME: Rate of procedural success (defined by successful cannulation and angiography of pre‐defined vessels based on diagnostic requirements). Efficacy will be assessed via procedural success rates (binary variable) for both groups, with between‐group comparison performed using non‐inferiority testing (non‐inferiority limit of 10% procedural failure). SECONDARY OUTCOME: ; 1. Visual analogue scale (VAS) assessment of post‐procedure pain from the access site, measured 1 h post‐procedure. The means for the two groups will be compared using an unpaired t‐test (alpha = 0.05). A >10% difference in the mean values of the VAS results between groups would be indicative of significant clinical difference.; ; INCLUSION CRITERIA: 1. Aged =18 years 2. Referred to the Department of Neuroradiology (UHN) for diagnostic cerebral angiography 3. Ability to give informed written consent to participate in the study, or have a next of kin present (phone consent will not be deemed satisfactory) to give such consent