Feasibility Study Of Low Dose CT With Ahybrid Iterative Reconstruction Technique For Evaluation Of Airway Stents In Patients With Malignant Tracheal Stenosis

ObjectiveTo investigate the image quality of low dose CT with a hybrid iterative reconstruction technique(iDose4, Philips Healthcare) for airway stents evaluation compared to routine dose CT in patients with malignant tracheal stenosis. Methods60 patients(58±8.6 years, 37 male) with airway stent who are randomly assigned into two groups(routine-dose(RD) and low-dose(LD) group, 30 for each) underwent chest CT on a 256-slice CT(RD-group 120 kV, 250 mAs, LD-group 120 kV, 120mAs). Images were reconstructed by filtered back projection(FBP) in RD-group and iDose4 in LD-group. CTDIvol of both groups was recorded. Image quality assessment was performed by two radiologists according to structure demarcation near stents, artifacts, noise, and diagnostic confidence using a five-point scale [1(poor) to 5(excellent)]. Image noise, SNR and CNR were measured. Subjective image quality was compared with Mann-Whitney test. Student t test was used to test objective image quality and radiation dose between groups. ResultsThe score of Sharpness, noise, artifacts, diagnostic confidence about airway stent in LD group were 3.77±0.53, 3.62±0.56, 3.70±0.72, 3.98±0.70, respectively. And the score of Sharpness, noise, artifacts, diagnostic confidence about airway stent in RD group were 3.65±0.69,3.73±0.66,3.35±0.58,3.72±0.67, respectively. There was no significant difference in image quality of structure demarcation, noise and diagnostic confidence between the two groups(P>0.05), while iDose4 enabled a higher score in image quality of artifacts in LD-group compared with those in RD-group(P=0.004). The subjective evaluation scores of image quality from two radiologists indicated excellent inter-observer agreement in scoring results, Kappa value were 0.851,0.847,0.859,0.892,respectively(all P<0.05).The objective noise of LD group(14.7±3.4) was lower and CNR(0.68±0.66) was higher than RD group(SD=15.6 ± 4.5, CNR=0.64 ± 0.51), but were no significant difference(P=0.41, P=0.754, respectively). SNR was significantly higher of LD-group than RD-group(3.76±1.37 VS 3.14±0.90, P=0.044). ConclusioniDose4 improves image quality of low dose CT by comparison of routine dose images reconstructed by FBP, which indicates that iDose4 may help low dose CT to become a routine use for airway stents evaluation.