Establishment of Radiation Dose Reduction Criteria for Thoracic and Abdominal CT via Systematic Spatial Resolution Evaluation

With the development of various reconstruction algorithms for CT imaging, it has become possible to perform low-dose CT examinations without compromising image quality. However, quantitative evaluation such as image noise, signal-to-noise ratio (SNR), and contrast-tonoise ratio (CNR) have been mainly used yet, while the spatial resolution and overall image quality rely on subjective assessment. Therefore, this study aimed to propose a quantitative method for evaluating spatial resolution in chest and abdominal CT scans, in order to facilitate dose reduction. For this study, a phantom was fabricated using 3D printing and scanned under chest and abdominal imaging conditions, with additional scans performed under low-dose conditions. The peak, bottom, FWHM, DFWHM, and peak-bottom were compared and analyzed. The results showed no statistically significant differences in spatial resolution parameters between all chest and abdominal protocol, with FWHM and DFWHM indicating the same distance. Even if the dose is reduced to 30 mAs in the chest CT condition and to 50 mAs in the abdominal CT condition, there will not be a big problem in terms of spatial resolution. Lastly, the indices from this study demonstrate potential as objective measures of spatial resolution when applying low-dose CT protocols.