Objective To explore the feasibility of children age dependent chest tube voltage settings for optimizing radiation dose and image quality in digital radiography (DR). Methods Children aged 0 to 14 who visited the First Affiliated Hospital of Xinjiang Medical University from January, 2008 to December, 2010, were divided into the following 5 age groups: 0~, 1~, 3~, 7~, and 11~14-year-old, and each group was then randomly assigned to the optimization and control groups to take DR by computer. DR in automatic exposure control with different tube voltage depending on children age; the control group: DR in automatic exposure control with conventional fixed tube voltage. The dose area product (DAP) was adopted for the measurement of radiation dose, while the visual grading analysis score (VGAS) was for image quality. Then SPSS 17.0 was applied for statistical analysis. Results A total of 2 450 children were initially included. Finally there were 2 415 children included in the anteroposterior chest image in this study, and the other 35 children were excluded for their anatomical characteristics could not be showed due to serious primary diseases. There were 1 202 patients in the optimization group and 1 213 patients in the controlled group. The mean DAP in the optimization group was lower than that in the control group with a significant difference (t= –4.967, P=0.008). The mean VGAS in the optimization group was higher than that in the control group with a significant difference (t= 23.738, P=0.000). Conclusion Children age dependent tube voltage settings can effectively reduce radiation dose and improve image quality at the same time.
Objective To optimize image quality and radiation dose of infant chest digital radiography and to explore feasibility of reducing tube voltage and adjusting according to infant chest area. Methods 0 to 3-year-old infants were randomly divided into two average groups of 0- and 1-3 year-old, and then each age group was randomly assigned to optimization and control groups in digital radiography. Measurement of radiation dose used dose area product (DAP). Mean DAP between groups was compared by using t test, and the image quality of optimization was compared by rank sum test. Results A total of 400 cases of 0 to 3-year-old infants were identified, and finally 391 cases of infants anteroposterior chest image were included, including 196 cases in the optimization group (0-years: n=91; 1-3 years: n=105) and 195 cases in the control group (0-years: n=103; 1-3 years: n=92). The results showed: there were significant differences in the mean DAP in 0-years, 1-3 years and total infants between the optimization group and the control group (all P valuelt;0.05). The DAP of the optimization group was lower, and reduction of DAP was approximately 21.6% compared to the control subject. The Wilcoxon signed-rank test showed the difference of subjective evaluation of image quality was significantly different (P=0.000). High-quality image of the optimization group increased approximately 43.9% more than control subject. Conclusion Reducing tube voltage and adjusting according to infants chest area can not only reduce the radiation dose but also improve image quality in digital radiography.
ObjectiveTo explore the effect of snapshot freeze (SSF) on the image quality of coronary artery in 64 multislice spiral CT for patients with high heart rate. MethodsWe retrospectively analyzed the clinical data of 98 patients with an mean heart rate of ≥ 70 beats/min who underwent coronary CT angiography examination between August 2013 and February 2014. According to the inclusion criteria, 60 patients were included in our study. The image quality of standard reconstruction (STD) and motion-corrected (MC) reconstruction based on SSF platform were analyzed. The image quality was classified into 4 grades, and the image quality of coronary segments named according to AHA standard was evaluated. Then, we compared the image quality between the two different reconstruction methods. ResultsAltogether 180 coronary arteries and 795 coronary segments were evaluated. Before MC reconstruction, there were 133 (73.89%) arteries and 287 (36.10%) segments had pseudomorph, while after MC reconstruction, those two numbers were 89 (49.44%) and 150 (18.87%) (P<0.05). The right coronary artery (RCA) had a higher rate of pseudomorph and a lower image quality score[91.67% (55/60), 3.32±0.40] than left anterior descending artery[60.00% (36/60), 3.69±0.42] and left circumflex artery[70.00% (42/60), 3.44±0.55], especially the S2[90.00% (54/60), 2.45±0.85]. Overall image quality was higher with the use of MC reconstruction on per-artery level (P<0.05) and most of the per-segment level (P<0.05) compared with STD, especially for RCA and its segments (P<0.05). ConclusionSSF improves image quality of coronary artery in patients with high heart rate, especially for RCA.
ObjectivesTo investigate the influence of scanning parameters (tube voltages and tube currents) on image quality and corresponding radiation doses with simulated lung nodules in chest CT.MethodsThe anthropomorphic chest phantoms with 12 simulated, randomly placed nodules of different diameters and densities in the chest were scanned by different scanning parameters. The detection rate, degree of nodular deformation, image quality (with both subjective and objective evaluation) and the corresponding radiation doses were recorded and evaluated, and the correlation between nodule detection rate, degree of nodular deformation, radiation dose and image quality using different scanning parameters was analyzed.ResultsThe image quality improved with the increase of tube voltage and tube current (P<0.05). When the tube current was constant, the CT values of the vertebral decreased gradually with the increase of tube voltages (P<0.05); however, significant difference was not detected in CT values of the lung field (P>0.05). When the tube current was 100 mAs, the lung nodules with CT values of +100 HU and −630 HU showed statistical difference when using different tube voltage (P<0.05); but there was no significant difference in nodules of −800 HU (P=0.57). When tube voltage was 100 kV and 120 kV each, it was possible to detect all lung nodules with a detection rate of 100%. The detection rate was 33% and 66% in 3 mm diameter when the tube current was 80 kV/15 mA and 80 kV/20 mA, respectively. The nodules deformation in nodules with a CT value of −630 HU and diameter less than 5 mm was the most prominent (P<0.05). After analyzing the relationship between image quality and radiation doses using different tube voltages, we established a system of correlation equations: 80 kV: Y=2.625X+0.038; 100 kV: Y=14.66X+0.158; 120 kV: Y=18.59X+0.093.ConclusionsThe image quality improves with the increase of tube current and tube voltage, as well as the corresponding radiation doses. By reducing the tube voltage and increasing the tube current appropriately, the radiation doses can be reduced. Follow-up CT examination of pulmonary ground glass nodules should apply the same tube voltage imaging parameters, so as to effectively reduce the measurement error of nodule density and evaluate the change of nodules more accurately.
ObjectiveTo explore the impact of different monochromatic reconstruction on image quality of early lesions of coronavirus disease 2019 (COVID-19).MethodsThe chest spectral CT images of 11 patients confirmed as COVID-19 in West China Hospital of Sichuan University between January and February 2020 were retrospectively analyzed. A total of 34 inflammatory lesions were found in the 11 cases. Seven groups of images were reconstructed from the raw data for each patient, including the conventional polychromatic image and different monochromatic images of 40-140 keV (with intervals of 20 keV). CT and standard deviation (SD) values of all lesions were measured to calculate the signal-noise ratio (SNR) and contrast-noise ratio (CNR). The image quality was subjectively scored by two radiologists, and the differences in image quality among different monochromatic groups and the polychromatic group were compared.ResultsWith the increase of X-ray energy, the CT values and SD values of reconstructed images in monochromatic groups gradually decreased, and the SNRs and CNRs gradually increased, and the differences between adjacent two groups were all statistically significant (P<0.001). In the range of 80-140 keV, the SD values of different monochromatic groups were lower than that of the polychromatic group, and the SNRs and CNRs were higher than those of the polychromatic group, and the pairwise comparison results showed statistically significant differences (P<0.001). The 120 keV-reconstructed image had the highest subjective score, and the difference from that of the polychromatic image was statistically significant (P<0.05).ConclusionsDifferent monochromatic reconstruction of spectral CT can significantly reduce the image noise in early COVID-19 lesions, and improve the image quality. Combining subjective and objective evaluation of images, the 120 keV-reconstructed monochromatic image shows the best early lesions of COVID-19 and is of great significance for early clinical screening.