ABSTRACT
Objective To explore the best percentage of adaptive statistical iterative reconstruction Veo (ASiR-V)in detection of pulmonary nodule by chest ultralow dose CT (ULDCT).Methods 81 patients with pulmonary nodule detected by chest low dose CT (LDCT)underwent a local ULDCT scan at the center of the nodule with a range of 3 cm scan length.LDCT was performed with the mode of the Assist kV (120/100 kV)/Smart mA with noise indices of 14.1 HU and reconstructed with ASiR-V 50% algorithm.ULDCT was acquired at a tube potential of 120 kV and tube current-time product of 2.8 mAs and reconstructed with ASiR-V 50%,70% and 90%algorithms.Subjective and obj ective image qualities,sensitivities of detection and diameter of nodule among all ULDCT images were compared.Results Compared with the radiation dose of LDCT [(0.9 9±0.3 6)mSv],a 90.2% decrease was seen with the ULDCT, for which the calculated mean effective radiation dose was (0.097±0.007)mSv.The noise values of fat and paravertebral muscle for ULDCT reconstructed with ASiR-V 90% were 12.33±1.86 and 14.82±2.6,which were significantly lower than those in the group of ASiR-V 50% (1 9.73±1.98, 21.19±2.46)and the group of ASiR-V 70% (15.79±1.82,17.71±2.50)(P＜0.05).The subjective scores of images reconstructed with ASiR-V 70% (4.13±0.47)were the highest,which were slightly higher than those in 90%groups (4.03±0.38)(P＜0.05).No significant differences for overall sensitivity of nodule detection were observed among the ULDCT reconstructed with ASiR-V 50%(86.42%),ASiR-V 70%(87.04%)and ASiR-V 90% (88.89%)(P＞0.05).The mean nodule diameter measurements were (6.4±2.0)mm,(5.9±2.2)mm,(6.0±2.2)mm and (6.1 ±2.2)mm for LDCT and ULDCT (ASiR-V 50%,70% and 90%),respectively with P＞0.05.Conclusion At extremely low exposure levels,ASiR-V can obviously improve the image qualities of ULDCT,and 90% is the best percentage for lung algorithm reconstruction with a high sensitivity of pulmonary nodule detection.
ABSTRACT
Objective To study the effects of joint optimization of CT scanning?modes and CTA starting?modes on the image quality, the patients' radiation doses and contrast volumes in cervicocerebral CTA. Method According to the date of examination from December 2013 to January 2014, 188 consecutive patients were prospectively selected and underwent cervicocerebral CTA using different CT scanning?modes and CTA starting?modes. These patients wererandomly divided into 4 groups:A1 (45 cases), A2 (48 cases), B1 (45 cases) and B2 (50 cases). Group A1 were Flash mode combined with test bolus, Group A2 were Flash mode combined with bolus tracking, group B1 were the common spiral scanning mode combined with test bolus and group B2 were the common spiral scanning mode combined with bolus tracking. The objective image quality evaluation criteria included the CT value comparison at the aortic arch (Pa1), carotid artery bifurcation (Pa2), basal artery (Pa3), superior vena cava (Pv1), internal jugular (pv2), transverse sinus (Pv3) and image objective noise. The subjective image quality assessments criteria included the contrast hardening artifact and diagnose acceptability. The radiation dose and contrast volumes of every patient were recorded and analyzed. The analysis of variance, the chi?square tests and the rank sum tests (Kruskal?Wallis) were used for data statistics. Results There were significant differences on the CT value at transverse sinus among the four groups, they were (124±30), (151±34), (130±37) and (160±37) HU, and different starting?modes had impacts on venous reflux (P0.05). The image noise had significant differences in four groups (P0.05), however there were significant differences on contrast hardening artifacts (P<0.05) among the four groups. With the same scanning mode, the artifacts of group A1 were more serious than A2 and B1 were more serious than B2.There were significant differences on the patients' contrast volumes in the four groups (P<0.05), they were (45±5), (49±4), (35±4) and (35±4) ml, the contrast volumes in groups A1 and B1 were more than groups A2 and B2. There were significant differences among the four groups on patients' ED (P<0.05), which were (0.79 ± 0.07), (0.81 ± 0.08), (1.49 ± 0.11) and (1.51 ± 0.12) mSv. The radiation dose in groups A1, A2 were lower than those in B1 and B2. Conclusion The joint use of Flash mode and bolus tracking technique is recommended in application of cervicocerebral CTA, for its advantages of better image quality, good diagnosis acceptability, the patient's low radiation dose and low contrast volumes.