Improving image quality consistency and diagnostic accuracy in lower extremity CT angiography using a split-bolus contrast injection protocol.

OBJECTIVES: To evaluate the clinical value of using a split-bolus contrast injection protocol in improving image quality consistency and diagnostic accuracy in lower extremity CT angiography (CTA). METHODS: Fifty (mean age, 66 ± 12 years) and 39 (mean age, 66 ± 11 years) patients underwent CTA in the lower extremity arteries using split-bolus and fixed-bolus injection schemes, respectively. The objective and subjective image quality of the 2 groups were compared and the diagnostic efficacy for the degree of vessel stenosis was compared using digital subtraction angiography as the gold standard. A P < .05 was considered statistically significant. RESULTS: In comparison with the fixed-bolus scheme, the split-bolus scheme greatly improved the consistency of image quality of the low extremities by significantly increasing the arterial enhancement (337.87 ± 64.67HU vs. 254.74 ± 71.58HU, P < .001), signal-to-noise ratio (22.58 ± 11.64 vs. 7.14 ± 1.98, P < .001), and contrast-to-noise ratio (37.21 ± 10.46 vs. 31.10 ± 15.40, P = .041) in the infrapopliteal segment. The subjective image quality was better (P < .001) and the diagnostic accuracy was higher in the split-bolus group than in the fixed-bolus group (96.00% vs. 91.67%, P < .05, for diagnosing >50% stenosis, and 97.00% vs. 89.10%, P < .05, for diagnosing occlusion) for the infrapopliteal segment arteries. CONCLUSIONS: Compared with the fixed-bolus injection scheme, the split-bolus injection scheme improves the image quality consistency and diagnostic accuracy especially for the infrapopliteal segment arteries in lower extremity CTA. ADVANCES IN KNOWLEDGE: (1) The split-bolus injection scheme of CTA of the lower extremity arteries improves the overall image quality, uniformity of contrast enhancement. (2) Compared with the fixed-bolus injection scheme, the split-bolus injection scheme especially improves the infrapopliteal segment arteries image quality and diagnostic efficacy.

Image quality improvement in low-dose chest CT with deep learning image reconstruction.

OBJECTIVES: To investigate the clinical utility of deep learning image reconstruction (DLIR) for improving image quality in low-dose chest CT in comparison with 40% adaptive statistical iterative reconstruction-Veo (ASiR-V40%) algorithm. METHODS: This retrospective study included 86 patients who underwent low-dose CT for lung cancer screening. Images were reconstructed with ASiR-V40% and DLIR at low (DLIR-L), medium (DLIR-M), and high (DLIR-H) levels. CT value and standard deviation of lung tissue, erector spinae muscles, aorta, and fat were measured and compared across the four reconstructions. Subjective image quality was evaluated by two blind readers from three aspects: image noise, artifact, and visualization of small structures. RESULTS: The effective dose was 1.03 ± 0.36 mSv. There was no significant difference in CT values of erector spinae muscles and aorta, whereas the maximum difference for lung tissue and fat was less than 5 HU among the four reconstructions. Compared with ASiR-V40%, the DLIR-L, DLIR-M, and DLIR-H reconstructions reduced the noise in aorta by 11.44%, 33.03%, and 56.1%, respectively, and had significantly higher subjective quality scores in image artifacts (all p < 0.001). ASiR-V40%, DLIR-L, and DLIR-M had equivalent score in visualizing small structures (all p > 0.05), whereas DLIR-H had slightly lower score. CONCLUSIONS: Compared with ASiR-V40%, DLIR significantly reduces image noise in low-dose chest CT. DLIR strength is important and should be adjusted for different diagnostic needs in clinical application.

Individualized protocol for radiation and contrast medium dose reduction in one-stop assessment for kidney transplantation patients.

OBJECTIVE: To compare image quality, radiation, and contrast medium (CM) doses between individualized and conventional scan protocols in combined coronary CT angiography (CCTA) and iliac artery CTA for kidney transplantation patients. METHODS: 148 patients needing assessment for coronary and iliac arteries before kidney transplantation were prospectively enrolled and randomly divided into the conventional and individualized groups. All patients underwent one-stop combined scans on a 256-row CT scanner with automatic tube current modulation, 50 % pre-ASIR-V to control radiation dose. CCTA was performed first using one heartbeat axial scan mode with bolus tracking technique and iliac CTA was performed 3 s after CCTA using a spiral scan. The conventional group (n = 72) used the standard protocol: 100 kVp, 60 mL of 350 mgI/mL CM at 4.5 mL/s flow rate. The individualized group (n = 76) used a body-mass-index (BMI)-dependent protocol: kVp: 80 (BMI < 24) and 100 (BMI ≥ 24) and CM: 19 mgI/kg (BMI < 18); 21 mgI/kg (18 ≤ BMI < 24); and 22 mgI/kg (BMI ≥ 24). Image quality radiation and CM doses of the two groups were compared. RESULTS: There was no significant difference in patient demographic data. Compared with the conventional group, the individualized group reduced contrast flow rate (in mL/s) by 14.4 % (3.85 ±â€¯0.72 vs. 4.5), contrast dose (in mL) by 35.8 % (38.53 ±â€¯7.18 vs. 60) and radiation dose (in mSv) by 34.3 % (4.30 ±â€¯1.73 vs. 6.54 ±â€¯1.45). The individualized group had significantly higher subjective image quality score (P ＜ 0.05), lower noise (17.30 ±â€¯4.97 HU vs. 19.13 ±â€¯4.73 HU, P = 0.02) and higher signal-to-noise ratio (22.09 ±â€¯7.41 vs. 19.55 ±â€¯6.18, P = 0.03) for the three main vessels in CCTA compared with the conventional group. There were no differences in both subjective scores and objective measurements in iliac artery CTA between the two groups. CONCLUSION: The individualized scanning protocol in the one-stop assessment of coronary and iliac arteries before kidney transplantation significantly reduces both radiation and CM doses while maintaining image quality in iliac artery CTA and providing better coronary artery images in CCTA.

Improving diagnostic accuracy for arteries of lower extremities with dual-energy spectral CT imaging.

PURPOSE: Investigate the clinical value of improving diagnostic accuracy for arteries of lower extremities with low energy images in dual-energy spectral CT (DEsCT) imaging. METHOD: 110 (mean age, 67 ±â€¯10 years) and 72 (mean age, 65 ±â€¯13 years) patients underwent CT angiography (CTA) in the lower extremities using dual-energy and conventional (100kVp) imaging mode, retrospectively. The 50 keV monochromatic images were reconstructed in the DEsCT group for analysis. The quantitative and qualitative image quality of the two groups were compared using various statistical analysis methods and the diagnostic accuracy for the degree of vessel stenosis was compared using DSA as the gold standard. Consistency test was used for intra-group evaluation. A P < 0.05 was considered statistically significant. RESULTS: The use of 50 keV images in DEsCT significantly increased the enhancement in arteries of LKS (544.91 ±â€¯106.37HU vs. 339.65 ±â€¯83.74HU, P < 0.001) and provided higher SNR (19.92±9.39 vs. 17.39±4.99, P = 0.04) and CNR (45.60±16.61 vs. 38.70±18.17, P < 0.01) compared with conventional 100kVp images. Mann-Whitney test showed that the subjective image quality of the arteries of lower knee segment (LKS) in the DEsCT group was higher than in the conventional group (P = 0.01). The diagnostic efficiency of DEsCT group was better than that of conventional group, mainly in arteries of LKS (95.91 % vs. 87.85 %, for 50 % stenosis, P<0.001; 94.32 % vs. 89.58 % for occlusion, P = 0.02). CONCLUSIONS: The use of 50 keV DEsCT images enhances the contrast in the lower extremity arteries and improves the diagnostic accuracy for the arteries of LKS, compared with the conventional CTA protocols.