Comparison of different approaches for image quality assessment in computer tomography

There are two approaches for the computed tomography (CT) image quality assessment: objective method based on the assessment of the physical and technical parameters of the image and subjective method based on expert image quality assessment. The aim of this study was to compare these methods of the image quality assessment and to evaluate their applicability for CT scan protocol optimization. The study was performed using ACR CT accreditation phantom to assess the physical and technical parameters (HU of water, noise, contrast to noise ratio and modulation transfer function) and anthropomorphic Chest Phantom N1 Lungman with imitators of lung “ground glass opacity” nodules for expert image quality assessment. The phantoms were scanned on five CT scanning protocols with different mAs (levels of patient dose). The results of the study indicate that the physical and technical parameters are not suitable as full alternative for the expert image quality assessment but can be used as an approach to exclude the CT protocols/images with unacceptable image quality and can be recommended as a primary assessment of the image quality during the optimization in CT.