Beam hardening correction for a cone-beam CT system and its effect on spatial resolution

• Published in: Chinese physics C Vol. 35; no. 10; pp. 978 - 985
• Main Author: 赵维 付国涛 孙翠丽 王燕芳 魏存峰 曹大泉 阙介民 唐晓 史戎坚 魏龙 郁忠强
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.10.2011
• Subjects: Beams (radiation); CT图像重建; CT系统; Hardening; Image enhancement; Image quality; Image reconstruction; Mathematical analysis; MTF值; Spatial resolution; 射束硬化校正; 点扩散函数; 空间分辨率; 调制传递函数; 锥束
• ISSN: 1674-1137; 0254-3052; 2058-6132
• DOI: 10.1088/1674-1137/35/10/018

In this paper, we present a beam hardening correction （BHC） method in three-dimension space for a cone-beam computed tomography （CBCT） system in a mono-material case and investigate its effect on the spatial resolution. Due to the polychromatic character of the X-ray spectrum used, cupping and streak artifacts called beam hardening artifacts arise in the reconstructed CT images, causing reduced image quality. In addition, enhanced edges are introduced in the reconstructed CT images because of the beam hardening effect. The spatial resolution of the CBCT system is calculated from the edge response function （ERF） on different planes in space. Thus, in the CT images with beam hardening artifacts, enhanced ERFs will be extracted to calculate the modulation transfer function （MTF）, obtaining a better spatial resolution that deviates from the real value. Reasonable spatial resolution can be obtained after reducing the artifacts. The 10% MTF value and the full width at half maximum （FWHM） of the point spread function with and without BHC are presented.