Measurement and analysis of CT number linearity

Objective: To explore the evaluation method for CT number linearity by measuring CT numbers. Methods: The model CTP401 of Catphan500 phanton was adopted to measure CT numbers of four objective substances, then CT number Linearity, contrast scales, and uncertainties were calculated. Results: Statistically significant differences in CT numbers were found between the two reconstruction algorithms (P<0.001), The contrast scale of sharp reconstruction algorithm was 1.90 x 10-4 cm-1 · Hu-1, and smooth reconstruction algorithm was 1.79 x 10-4 cm-1 · Hu-1. Conclusions: Qualified CT number linearity is important to image quality control in CT scanners, Reconstruction algorithms and uncertainties must be marked in test reports of CT number linearity. (authors)