Fifty-percent diluted contrast medium provides acceptable image quality in cerebral angiography

Purpose: Cerebral angiography is essential for neuro-endovascular treatment but carries a risk of contrast-induced nephropathy (CIN).Although dilution of iodinated contrast medium may reduce this risk, its impact on diagnostic image quality has not been fully clarified.This study evaluated whether 50% diluted contrast medium provides sufficient diagnostic confidence during preoperative angiography for unruptured cerebral aneurysms.Methods: Twenty-two patients with unruptured anterior circulation aneurysms were prospectively enrolled.Each patient underwent paired acquisitions with standard undiluted and 50% diluted contrast for 2D DSA and 3D rotational angiography (3DRA).Three independent reviewers rated paired images using a five-point scale (1 = no difference, 2-3 = differences without diagnostic impact, 4 = diagnostic impairment, 5 = nondiagnostic).The median score of the three reviewers was used for analysis.Scores of 4-5 were considered clinically unacceptable.Non-inferiority was confirmed if the upper limit of the 95% CI for the proportion of such cases was <0.30.Results: Across 2D DSA and 3DRA, no patients received scores of 4-5 with 50% diluted contrast medium, yielding clinically unacceptable evaluation rates of 0% (95% CI = 0-15.4).Some 3DRA volume-rendered images displayed minor decreases in visualization of small branches such as anterior choroidal or lenticulostriate artery, but the corresponding MIP images remained diagnostic.Conclusions: Angiography using 50% diluted contrast medium was associated with no clinically meaningful loss of image quality.