Impact of reconstruction techniques on low dose chest CT image quality：comparison of FBP,iDose4 and IMR / 实用放射学杂志

ABSTRACT

Objective To investigate the impact of different reconstruction algorithms ,including filtered back projection (FBP) , hybrid iterative reconstruction technique (iDose4 ,Philips Healthcare) and iterative model reconstruction (IMR ,Philips Healthcare) on image quality of the low dose chest CT .Methods 30 consecutive patients underwent chest CT on a 256‐slice CT (80 kVp ,80 mAs) were enrolled .Raw data were reconstructed with FBP ,iDose4 ,IMR_soft (L1_Body_Soft_Tissue) and IMR_routine(L1_Body_Routine) algorithms respectively ,and reconstructed thickness was 1 mm ,increment 0 .5 mm .SD ,SNR and CNR were measured and recor‐ded .Image quality was assessed using 4‐point scale (poor to excellent) with lung and mediastinum window ,respectively .We com‐pared quantitative and qualitative parameters among three reconstructions .Results SD of four groups were 55 .7 ± 20 .7 ,37 .0 ± 13 .0 , 13 .4 ± 4 .9 and 19 .5 ± 7 .0 ,repectively .Compared with FBP group ,SD reduced by 33 .5% ,75 .9% ,65% (all ,P0 .05) .The image quality score of lung window in IMR_routine group was the highest in groups ,but was no significantly different with IMR_soft group ,and was significantly different with FBP group and iDose4 group ,respectively .The image quality score of mediastinum window in IMR_soft group was the highest in groups , but was no significantly different with IMR_routine group and was significantly different with FBP group and iDose4 group ,respec‐tively .Conclusion Compared with FBP technique ,iDose4 and IMR techniques can distinctly reduce image noise and improve image quality on low dose CT ,especially IMR algorithm .