Computed Tomography Of The Lung In The High Pitch Mode During Continuous Breathing

Objectives: To prospectively investigate whether the high-pitch mode(HPM) for computed tomography(CT) enables the diagnostic visualization of the lung parenchyma without suspended respiration.Materials and Methods: A total of 60 patients(age, 56±10years) underwent 128-slice dual-source CT of the chest. CT chest routine scan was performed in the HPM with a pitch of 3.2 during continuous breathing(group A routine scan,n=30) and CT chest enhanced scan was performed at standard pitch of 1 during deep-inspiratory breath-hold during breath-hold(group A enhance scan), and at standard pitch of 1 during deep-inspiratory breath-hold(group B,n=30). Three groups adopt automatic tube current modulation technology scans. All groups were treated with SAFIRE reconstruction. Two blinded readers independently assessed the image quality of 5 regions in both the lungs using a semiquantitative 3-point score. Image noise was measured as the standard deviation of attenuation. Presence and size of pulmonary nodules were noted and measured on each CT dataset. Lung volume was measured using Lung care software.Results: Interobserver agreement for image quality ratings was excellent(k=0.91). There were no significant differences in the number of lung regions having an image quality other than excellent, whereas significantly less regions had impaired image quality in group A(4%,6/150) compared with group B(8%,12/150).Image quality impairment in group B was because of breathing in 25% and cardiac pulsation in 75%. Both the image noise in the center of group A(31.1±2.0HU;range:25.3-32.4 HU;) was significantly lower than that in group B(19.2±1.9 HU;range:15.8-23.8HU P < 0.001)),or the image noise in the periphery of group A(22.0±2.3HU range:15.8-24.0) was significantly lower than that in group B(17.6±1.4HU;range:15.6-19.7 HU;P < 0.001); image noise mean difference between the center and the periphery of group A(11.1±0.3HU) was significantly lower than that in group B(1.7±0.5HU).There were no significant differences for the size(P=0.73) and volume(P=0.94) of lung nodules among the 2 modes. Estimated effective radiation doses in group A and group B were 1.2±0.3mSv and 3.4±0.6mSv, respectively.Conclusions: CT of the lung can be accomplished using the HPM at a low radiation dose with a diagnostic image quality even without suspended respiration.