Investigation impact of dual model iterative reconstruction method(iDose~4) on the CT image quality and dose reduction—a phantom approach

Objective: To investigate the impact of iterative reconstruction method(iDose4) on the CT image quality and dose reduction by using phantom studies. Methods: A Catphan phantom was scanned by a 256-slice CT(Philips Brilliance iCT) with varied mAs from 20 to 200, the axial images were reconstructed by filtered back projection(FBP) and iDose4with a level of 1 to 6. Image quality was assessed with following aspect: CT value accuracy and consistency, image noise and signal-noise-ratio(SNR), low density resolution. Meanwhile the volume CT dose index CTDIvol and Dose length product DLP were recorded for dose evaluation. Results: The axial image CT values has a high degree of consistency(P0.05) for both iDose4and FBP reconstruction method. The image noise can be reduced in different degree with different iDose4level 1~6 reconstruction(9.46%~43.30%). When tube current reduced to 40%~50%(80~100 mAs), iDose4level 6 got image without significant difference regarding to the image noise compared to 200 mAs FBP image(P0.05); under the conditions of 50%~60% initial tube current(100~120 mAs), low density resolution could remain unchanged. Conclusion: iDose4can significantly reduce image noise and improve image quality, under the condition of 40% ~50% scanning dose can get satisfactory image quality. Thus iterative reconstruction has larger space to lower the scanning dose.