CT angiography (CTA) and Cr perfusion (CTP) imaging can play important roles in the workup of acute ischemic stroke. However, these techniques are hindered by the large amounts of contrast agents (CAs) required, high doses of X-ray radiation exposure, and nephrotoxicity of the clinical used iodinated CAs. To address these problems, we synthesized and validated a novel class of Cr CAs, PEGylated BaHoF5 nanoparticles (NPs), for CFA and CTP imaging, which can greatly enhance the diagnostic sensitivity and accuracy of ischemic stroke. These agents have unique advantages over conventional iodinated Cr agents, including much lower dosage required, major metabolism through liver and better imaging efficiency at different voltages. Once translated, these PEGylated BaHoF5 NPs can replace iodine-based CM for diagnostic contrast-enhanced imaging of patients with kidney/heart diseases and improve the overall diagnostic index with negligible side effects. (C) 2015 Elsevier Ltd. All rights reserved.