Radiation dose of non-enhanced chest CT can be reduced 40% by using iterative reconstruction in image space.

To evaluate the image quality and dose reduction capability of non-enhanced chest computed tomography (CT) examinations using iterative reconstruction in image space (IRIS). A CT water phantom was scanned at 120 kV/150 mAs and 100 kV/270 mAs as the reference, and the tube current was decreased in 10% intervals down to 40% of the reference value. Image noise was evaluated and compared between filtered back-projection (FBP) and IRIS reconstructed data. In the patient study, 90 patients underwent non-enhanced chest CT examinations; the patients were randomly assigned into three groups: group A (n=30) standard dose protocol, 120 kV/110 mAs; group B (n=30) low dose, 100 kV/110 mAs; group C (n=30) low dose, 120 kV/67 mAs. All images were reconstructed by FBP and IRIS algorithm using matched kernels of B30 and I30. The objective image noise (OIN), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the aorta and latissimus dorsi were measured. The subjective image quality and noise were scored using a three-point scale by two experienced radiologists. The results of the subjective and objective image assessment were compared between groups B and C (low dose) IRIS and group A (standard dose) FBP. The phantom study showed comparable image noise between the scans using 60% dose with IRIS and 100% dose with FBP for both 120 and 100 kV. In the patient study, groups A, B, and C had effective dose of 3.81 ± 0.43, 2.40 ± 0.19, and 2.41 ± 0.15 mSv. IRIS significantly improved the OIN, SNR, and CNR compared with FBP for the same patient. The OIN, SNR, and CNR using IRIS in group B and C were improved or comparable to those in group A using FBP. No significant difference was found in subjective image quality and noise between groups B and C using IRIS and group A using FBP. Compared with FBP, IRIS can maintain or improve image quality on unenhanced chest CT image reconstruction while saving 40% radiation dose.

Hu XH ，Ding XF ，Wu RZ ，Zhang MM ... -  《-》

Chest CT with iterative reconstruction algorithms for airway stent evaluation in patients with malignant obstructive tracheobronchial diseases.

Li T ，Zhang Y ，Wang Y ，Gao J ，Jiang Y ... -  《-》

Improved image quality in dual-energy abdominal CT: comparison of iterative reconstruction in image space and filtered back projection reconstruction.

Wang R ，Yu W ，Wu R ，Yang H ，Lu D ，Liu J ，Zhang Z ，Zhang C ... -  《-》

Combining low tube voltage and iterative reconstruction for contrast-enhanced CT imaging of the chest-initial clinical experience.

To evaluate the image quality of contrast-enhanced chest computed tomography (CT) with low tube voltage settings using an iterative reconstruction algorithm (iDose4) and standard dose filtered back projection (FBP) CT in patients with normal body mass index (BMI). Eighty patients with normal BMI were referred for a contrast-enhanced chest CT. Patients were randomly assigned into two groups: 120 kVp and 80 kVp. Standard convolution FBP was used to reconstruct the 120 kVp group (A) and 80 kVp group (C) image sets and iterative reconstruction (iDose4) was used to reconstruct the 80 kVp group (B) image sets. The mean image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and effective dose (ED) were calculated for each protocol. Image quality was graded (scale: 1-3) and compared among the three groups. The radiation dose was 71.35% less for the low-voltage protocol. Noise was significantly lower in the low-voltage images reconstructed with iDose4 (group B) compared with images reconstructed with FBP (group C). Group B had the highest SNR and CNR. There was no difference in subjective image quality scores between groups B and A (p > 0.05). Compared with standard FBP reconstruction, the iDose4 iterative reconstruction yields higher SNR, CNR, and better image quality in contrast-enhanced chest CT with low tube voltage settings.

Li Q ，Yu H ，Zhang L ，Fan L ，Liu SY ... -  《-》

The optimal dose reduction level using iterative reconstruction with prospective ECG-triggered coronary CTA using 256-slice MDCT.

To assess the image quality (IQ) of an iterative reconstruction (IR) technique (iDose(4)) from prospective electrocardiography (ECG)-triggered coronary computed tomography angiography (coronary CTA) on a 256-slice multi-detector CT (MDCT) scanner and determine the optimal dose reduction using IR that can provide IQ comparable to filtered back projection (FBP). 110 consecutive patients (69 men, 41 women; age: 54 ± 10 years) underwent coronary CTA on a 256-slice MDCT (Brilliance iCT, Philips Healthcare). The control group (Group A, n=21) were scanned using the conventional tube output (120 kVp, 210 mAs) and reconstructed using FBP. The other 4 groups were scanned with the same kVp but successively reduced tube output as follows: B[n=15]: 125 mAs; C[n=22]: 105 mAs; D[n=36]: 84 mAs: E[n=16]: 65 mAs) and reconstructed using IR levels of L3 (Group B), L4 (Group C) and L5 (Groups D and E), to compensate for the noise increase. All images were reconstructed using the same kernel (XCB). Two radiologists graded IQ in a blinded fashion on a 4-point scale (4 - excellent, 3 - good, 2 - fair and 1 - poor). Quantitative measurements of CT values, image noise and contrast-to-noise (CNR) were measured in each group. A receiver-operating characteristic (ROC) analysis was performed to determine a radiation reduction threshold up to which excellent IQ was maintained. There were no significant differences in objective noise, SNR and CNR values among Groups A, B, C, D, and E (P=0.14, 0.09, 0.17, respectively). There were no significant differences in the scores of the subjective IQ between Group A, and Groups B, C, D, E (P=0.23-0.97). Significant differences in image sharpness and study acceptability were observed between groups A and E (P<0.05). Using the criterion of excellent IQ (score 4), the ROC curve of dose levels and IQ acceptability established a reduction of 60% of tube output (Group D) as optimum cutoff point (AUC: 0.72, 95% CI: 0.59-0.86). Group D (84 mAs with L5) provided equivalent subjective image ranking (with lumen sharpness taken into account) and objective IQ measurements (noise: 36.5 ± 10.7; SNR: 13.6 ± 4.9; CNR: 16.28 ± 5.4) compared with FBP images in Group A (noise: 35.5 ± 9.4; SNR: 12.4 ± 2.5; CNR: 15.4 ± 3.2) (P=0.14, 0.09, 0.17, respectively). The effective dose (ED) of Group D was 63% lower than that of Group A (1.2 ± 0.1 mSv versus 3.2 ± 0.6 mSv). Iterative reconstruction techniques can provide 63% ED reduction in prospectively-triggered coronary CTA using 256-slice MDCT while maintaining excellent image quality.

Hou Y ，Xu S ，Guo W ，Vembar M ，Guo Q ... -  《-》