Optimization of thoracic CT scan protocol in lung cancer screening by further reducing patient dose while maintaining image quality

Abstract

Abstract

Introduction & Objective: Nowadays there has been a growing demand for low dose CT protocols. CT has a critical role in the management of the diagnosis chain of pulmonary disease, especially in lung cancer screening. There have been introduced several dose reduction methods, however, most of them are time-consuming, intricate and vendor based strategies that are hardly used in clinics routinely. This study aims to evaluate the image quality and pulmonary nodule detectability of low dose CT protocols, that are feasible and easy implemented. Image quality was analyzed in a general quality control phantom (gammex), and then in a manmade lung phantom with nodules equivalent objects. Methods and Materials: In this study, two phantoms, Gammex and lung phantom, were used. First, to reduce the dose, Kv, mA and pitch factors were changed. Using Gammex Phantom, a low-dose protocol was selected and applied to the lung phantom. SNR, CNR and noise level of Images were checked and compared with the standard protocol. Results: Contrast resolution for both standard and low dose protocol was the same and it was 2 mm; spatial resolution for standard protocol was 4 and for low dose protocol wad 6 line pairs per cm. CTDIvol is 16.8 for the standard protocol, 7.6 for low dose protocol, SNR and CNR are 9 and 0.4 for standard protocol and 5.8 and 0.3 for low dose protocol, respectively. Conclusion: The results show that by reducing the radiation factors to an acceptable diagnostic level, although it causes a slight decrease in image quality, the patient dose is greatly reduced and this has no effect on the diagnosis of lung lesions. Keywords: Lung Cancer Screening, Ionizing Radiation Dose, Image Quality, Lung Phantom