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.
【摘要】 目的 研究使用Bowtie滤线器（F1）后，保证加速器CBCT患者扫描图像质量前提下，如何合理设置扫描条件，尽量降低辐射剂量。 方法 使用Piranha辐射测量仪测量CBCT在使用F1与未使用F1时射线的半价层。设定不同的扫描模式，使用直径30 cm的有机玻璃模体测量扫描剂量，并使用XVI附带的Catphan503模体测量客观图像质量。在此基础上，研究扫描剂量以及图像质量与扫描条件的关系，提出了适合临床患者的胸部与腹部不同的扫描条件。 结果 使用F1后射束的半价层增加了0.77～0.92 mmAl，扫描剂量明显减少，中心点减少了22%~29%，边缘点减少了41%~45%，皮肤剂量减少显著。图像质量随着扫描剂量的增大而提高。空间分辨力受FOV影响较大，但一般能识别1～2 mm的物体，完全能够满足分辨细小骨结构与标记点的临床要求。图像伪影在使用L20时的大mAs下明显。胸部低剂量的CBCT图像如100 kV，M20，0.5 mAs的扫描条件亦可满足临床要求。腹部则需要使用较大剂量的扫描模式，CBCT图像才达到进行配准的要求。 结论 F1的使用在改善图像质量的前提下降低了扫描剂量，使用新的扫描序列能平衡二者的关系。【Abstract】 Objective To explore the influence of bowtie filtration on absorb dose and half-value layer inaluminum (Al) of cone-beam CT, estimate the image dose under different scan protocol, and establish the relationship between the image quality and the scan protocol after using F1. Methods Piranha was used to measure the HVL. Dose measurements were performed with an 0.6 cc Farmer type ionization chamber with a 30 cm-diam cylindrical shaped water phantoms in 100 and 120 kV with a series of mAs and FOV. CNR, noise and uniformity were measured on the Catphan503 images. Results HVL increased 0.77-0.92 mmAl where XVI generally had more penetrating beams at the similar kV settings. Scanning dose significantly reduced, the center point decreased 22%-29%, the edge with a decrease of 41%-45% which meant a very significant reduction in skin dose. Image quality improved with mAs increase. The spatial resolution mainly changed with FOV. But generally can identify 1-2 mm-diam objects, fully meet the clinical requirements of identify small bone structure and marker. Through this clinical investigation, low-dose CBCT images in chest, such as 100 kV, M20, and 0.5 mAs scanning protocol appeared to be an optimal settings. Abdomen image needed a higher dose to reach the requirements of registration. Conclusion Using F1 under the premise of improving the image quality then reducing the scanning dose and using a new scanning sequence can balance the image quality and scanning dose.
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.
目的 比较磁共振胰胆管成像（MRCP）三维质子加权快速自旋回波（SPACE）序列和半傅立叶采集单次激发快速自旋回波（HASTE）序列对胆囊管的显示情况，优选最佳的磁共振检查序列。 方法 2012年5月-2013年3月265例连续性患者同时采用SPACE序列和HASTE序列行MRCP检查，比较两种序列对胆囊管显示的图像质量和显示率，并进行统计学分析。 结果 SPACE序列对胆囊管显示的图像质量评分及显示率均优于HASTE序列 （P＜0.05）。 结论 SPACE序列是目前显示胆囊管较为理想的MRCP成像方法。
ObjectiveTo explore the effect of comfort care on patients undergoing CT enhanced scan. MethodsSixty patients undergoing CT enhanced scan were enrolled in June 2013, who were randomly divided into general care group (n=30) and comfort care group (n=30). General care group was given the routine care, while patients in the comfort care group accepted comfort care as well as routine care. The success rate of examination and excellent or good imaging rate between the two groups were compared. ResultsIn the general care group, the scan was successful in 21 patients and failed in 9, with a successful scan rate of 70.0% (21/30), and the excellent and good imaging rate was 71.4%. For the comfort care group, the scan examination succeeded in 29 patients and failed in 1 with a success rate of 96.7% (29/30), and the excellent and good imaging rate was 96.6% (28/29). The success rate in the two groups had statistical significance (χ2=7.680, P=0.006), and the excellent and good imaging rate was also significantly different (χ2=7.607, P=0.022). ConclusionComfort care for patients undergoing CT enhanced scan has a good effect in alleviating psychological stress, ensuring comfort and safety, and improving the success rate and excellent and good rate of imaging quality, which reflects its real value of nursing service in CT Department.
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.
A new enhancement method is proposed based on the characteristics of fundus images in this paper. Firstly, top-hat transform is utilized to weaken the background. Secondly, contrast limited adaptive histogram equalization (CLAHE) is performed to improve the uneven illumination. Finally, two-dimensional matched filters are designed to further enhance the contrast between blood vessels and background. The algorithm was tested in DIARETDB0 databases and showed good applicability for both normal and pathological fundus images. A new no-reference image quality assessment method was used to evaluate the enhancement methods objectively. The results demonstrated that the proposed method could effectively weaken the background, increase contrast, enhance details in the fundus images and improve the image quality greatly.
ObjectiveTo investigate the effects of the operation of nuclear medicine technologists on the quality and efficiency of whole-body bone imaging with single-photon emission computed tomography (SPECT). MethodsWe collected all the data from patients who underwent whole-body bone imaging with SPECT in the whole year of 2012 in Department of Nuclear Medicine, West China Hopsital of Sichuan University.From January to June 2012, no intervention was made.Between July and December 2012, a formal training including vein puncture, image processing, and post image processing improving was made for the technologists on the operation of whole-body bone scan.The difference in incidence rate of artifacts between the first and second half of the year was analyzed by χ2 test. ResultsIn all the 12 424 whole-body bone scan patients, the first and second six months had respectively 5 920 and 7 186.And the artifacts incidence rates were 15.6% vs.8.9%(χ2=137.483, P < 0.001).In addition, the daywork efficiency was highly improved by 16.7%(48.5 patients/day vs.56.6 patients/day). ConclusionThe operation of the nuclear medicine technologists not only affects the quality of whole-body bone imaging but also improves the work efficiency.
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.