Noise Characteristics of Summary Maps for Brain CT Perfusion: A Simulation Study Using a Digital Phantom and Clinical Images

Abstract

Purpose: Cerebral CT perfusion (CTP) summary maps classify the ischemic core, penumbra, and normal tissue from traditional parametric maps, which is a criterion for indicating thrombectomy. Since perfusion maps change when the CTP radiation dose is reduced, summary maps also might change. This study aimed to assess the noise characteristics of a summary map in simulation experiments. Methods: We added various amounts of noise to a digital phantom and clinical CTPs, used Vitrea (Canon Medical Systems, Tochigi, Japan) to perform perfusion analysis, and assessed the relationship between the noise and cerebral blood volume (CBV), time to maximum (Tmax), and ischemic core and penumbra volumes. Results: As the noise increased, the obtained CBV increased, the obtained Tmax shortened, and the obtained ischemic core and penumbra volumes decreased, which depended on the tissue’s CBV and Tmax. Conclusion: Under low-dose conditions, the ischemic core and penumbra volumes decreased, so the criteria for thrombectomy may differ from those for standard doses.