Feasibility study of hybrid scanning technique parameters on dose reduction and CT-image quality

초록

Recently, dose-reduction techniques have been the focus of radiation-based medical applications. In the present study, a region of interest (ROI) based imaging technique for dose reduction and attempted to solve the limitations and problems of conventional ROI imaging techniques by suggesting a novel hybrid scanning technique were developed. A prototype of the computed tomography (CT) system (TVX-IL1500H, GERI, Korea) and an RSD anthropomorphic head phantom were used to obtain the reconstructed image using two types of hybrid scanning techniques with source-to-detector distance and source-to-center rotation distance of 1178 mm and 905 mm, respectively. Hybrid CT images were reconstructed with a combination of truncated and nontruncated projections using the filtered back projection (FBP) reconstruction algorithm. The proposed hybrid CT scan was divided into alternating scans and half-scans. Optimization of hybrid CT scanning was performed using an acquisition parameter called the hybrid scanning weighting factor (HSWF), and image quality was evaluated by acquiring images according to each HSWF value. An image restoration method, based on the projection onto convex sets (POCS) algorithm introduced in our previous study, was used to correct the truncated projection data. The reconstructed image quality was analyzed using the structural similarity index (SSIM), contrast-to-noise ratio (CNR), and figure-of-merit (FOM). Consequently, appropriate acquisition parameter values for alternating half-scans in the hybrid scan were obtained and verified.

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