Considering the survival rate of small animals and the continuity of the experiments, high-dose X-ray shooting process is not suitable for the small animals in computed tomography (CT) experiments. But the low-dose process results with images might be polluted by noises which are not conducive for the experiments. In order to solve this problem, we in this paper introduce a global dictionary learning based denoising method to apply the promotion of the low dose CT image. We at first adopted the K-means singular value decomposition (K-SVD) algorithm to train a global dictionary based on the high dose CT image. Then, the noise image could be decomposed into sparse component which was free from noise through the orthogonal matching pursuit (OMP) algorithm. Finally, the noise-free image could be achieved by reconstructing the image only with its sparse components. The experiments results showed that the method we proposed here could decrease the noise efficiently and remain the details, and it would help promote the low dose image quality and increase the survival rate of the small animals.
目的 探讨双源CT腰椎检查中低剂量扫描方法及其临床应用价值。 方法 将2011年8月－2012年5月行双源CT腰椎检查的714例患者随机分为7组。均采用管电压120 kV，分别依次采用常规参考管电流量250 mAs和低管电流量240、230、220、210、200、190 mAs，且均采用CARE DOSE技术采集数据。扫描参数：准直器64 mm×0.6 mm，重建层厚0.75 mm，重建间隔0.7 mm，FOV 180～200 mm。采集图像后，测量腰3椎体的CT值及同层面的脊髓的CT值、背脊肌的CT值及噪声；腰5椎体的CT值及同层面的脊髓的CT值、背脊肌的CT值及噪声，并计算腰3、腰5椎体及相应层面脊髓的信噪比(SNR)和其相对于背脊肌的对比噪声比（CNR）。应用统计学软件对不同管电流下的CNR、SNR、盲法评分的数值以及射线剂量指数（CTDI）、剂量长度乘积（DLP）、有效剂量（ED）进行分析。 结果 第1组和第2组比较，图像的背脊肌SD值；腰3、腰5椎体和脊髓的SNR值进行比较，差异无统计学意义（P＞0.05）。第1组与第3、4、5、6、7组比较，腰3、腰5低管电流量各组间图像的背脊肌SD值；腰3、腰5椎体和脊髓的SNR值与常规管电流量组间比较差异均有统计学意义（P＜0.05）。腰3和腰5各组图像的椎体-背脊肌和脊髓-背脊肌CNR值分别行单因素方差分析，结果差异均无统计学意义（P＞0.05）。 结论 双源CT腰椎检查时，通过阶段性逐步降低管电流量的方法，使诊断医生逐渐适应低剂量图像质量，从而实现现有设备的低剂量扫描的方法是可行的。对于体质量指数（BMI）≤25 kg/m2的患者，可以采用190 mAs的参考管电流量进行腰椎扫描，不仅降低了患者接受的辐射剂量，同时也能获得满足临床诊断的合格图像，并且保护患者和减小设备损耗。
Liver computed tomography (CT) perfusion is a noninvasive imaging technology which can quantitatively investigate liver function, and it is mainly used in the diagnosis of liver tumors and assessment of liver function in the state of chronic liver diseases. The use of liver CT perfusion was limited in the past because of the high radiation dose. Now new technologies are exploited and they make it possible to reduce the radiation burden while maintaining the imaging quality. This article discusses the research progress of low radiation dose CT perfusion in 3 aspects, including X-ray source, reconstruction algorithm, and improvement of CT scanners and optimization of scanning parameters. Although there are not too many studies of low radiation dose CT perfusion on liver now and many problems need to be solved, the clinical application of it will be very prospective.
ObjectiveTo evaluate the effect of time-related administration of methotrexate (MTX) on neural cell apoptosis in rats after spinal cord injury (SCI) so as to investigate its potential neuroprotective mechanism and appropriate administration time. MethodA total of 120 male Sprague Dawley rats, 247-286 g in weight, were randomly divided into 4 groups (n=30) :sham group (group A), control group (group B), MTX treating group (group C), and MTX prophylaxis group (group D). The SCI model was established in the rats of groups B, C, and D by improved Allen method, and just laminectomy was performed in group A. MTX (0.5 mg/kg) was administered with tail vein injection at 1, 6, 12, 18, and 24 hours after injury in group C, and at 30 minutes before injury and at 6, 12, 18, and 24 hours after injury in group D; the equivalence saline was injected at 1, 6, 12, 18, and 24 hours after injury in groups A and B. Basso-Beattie-Bresnahan (BBB) score was used to evaluate the neural function at 1, 3, 7, 14, and 21 days after injury, HE staining to observe histological changes, immunohistochemical staining and TUNEL method to measure the expression of Caspase-3 and neural cells apoptosis, respectively. ResultsTen rats died during the experiment in groups B, C, and D; 25 rats in each group were included into the experiments at last. BBB score of group A was significantly higher than that of groups B, C, and D at all time points after injury (P<0.05) . BBB score of groups C and D were significantly higher than that of group B at 3, 7, 14, and 21 days (P<0.05) , and BBB score of group D was significantly higher than that of group C at 3, 7, and 14 days (P<0.05) . The histological observation showed normal structure of spinal cord at all time points after injury in group A. While the degree of SCI in group D was lighter than that in groups B and C, and group C was lighter than group B. At 14 days after injury, the degree of SCI in groups B, C, and D tend to keep the same. The number of Caspase-3 and TUNEL positive cells of groups B, C, and D was significantly more than that of group A at all time points after injury (P<0.05) , group B was significantly more than groups C and D (P<0.05) . The number of Caspase-3 positive cells of group C was significantly more than that of group D at 3, 7, and 14 days (P<0.05) . While the number of TUNEL positive cells of group C was significantly more than that of group D at 3 and 7 days (P<0.05) . And the number of Caspase-3 positive cells and TUNEL positive cells was positively correlated in groups B, C, and D (P<0.05) at 1, 3, 7, 14, and 21 days after injury. ConclusionsLow-dose MTX may effectively reduce the degree of the secondary injury of spinal cord by reducing the nerve cell apoptosis. Better effect can be obtained when MTX is used as prevent method than as a way of treatment.
Objective To assess the radiation dose and image quality with low-dose multi-detector row CT urography （CTU） for the evaluation of children patients with ureteropelvic junction stenosis （UJS）. Methods In this prospective study， 30 children patients with UJS underwent CTU were classified half-randomly through exam numbers into 3 groups （115 mA， 100 mA， and 75 mA）. Consecutive acquisitions including CT dose index weighted （CTDIw） and dose long product （DLP） were obtained in each patient and compared for each group. Three experienced chest radio-logists were unaware of the CT technique reviewed CT images for overall image quality using a 3-grade scale （excellent， good， and worst）. The data were analyzed using a parametric analysis of variance test and Wilcoxon’s signed rank test. Results The CTDIws of 115 mA group， 100 mA group， and 75 mA group were （7.63±0.83） mGy， （6.29±0.51） mGy， and （4.72±0.18） mGy， respectively， the difference was significant among three groups （F=36.445， P=0.000）. The mean CTDIw reduction was 38.2% in the 75 mA group as compared with 115 mA group （P＜0.001）. The DLPs of 115 mA group， 100 mA group， and 75 mA group were （173.89±29.88） mGy•cm， （145.96±26.21） mGy•cm， and （102.78±12.72） mGy•cm， respectively， the difference was significant among three groups （F=13.955， P=0.000）. The mean radiation dose reduction was 40.9% （75 mA group versus 115 mA group， P＜0.001）. The assessment of image quality was no significant difference with the same protocol and post-processing technique （Wilcoxon’s signed rank test， P＞0.05）. There was a good agreement for image quality scoring among the three reviewers （Kappa=0.736）. Conclusion Low-dose multi-detector row CTU should be considered as a promising technique for the evaluation of children patients with UJS because it could decrease radiation dose and obtain acceptable image quality.
Lung cancer is the leading cause of death among the tumors in the whole world. Although new diagnostic techniques have been developed for nearly 20 years, the mortality is still high. Until now, no randomized controlled trial of chest x-ray and sputum cytology showed the improvement of the survival rate of lung cancer. Low-dose CT can screen more patients in early stage, however, overdiagnosis, cost and the quality of studies should be considered. Further studies of RCTs should be done to clarify these questions.
【摘要】 目的 探讨多层螺旋CT低剂量扫描在小儿上尿路梗阻性疾病中的应用价值。 方法 2008年1月-2009年6月经临床手术证实尿路梗阻的患儿52例，按梗阻的原因分为结石组13例与非结石组39例。将非结石组患儿，按照年龄分为0~1岁（8例）、1~5岁（16例）和5~10岁（15例）3个组，均采用个性化的低剂量扫描方式。 结果 结石组与非结石组阳性诊断率均为100%。低剂量扫描患儿所接受的辐射剂量明显降低，CT扫描管电流不变，管电压降低1/3，CT检查的辐射剂量可降低约70%，且均可达到临床诊断要求。 结论 多层螺旋CT低剂量个性化扫描在小儿上尿路梗阻性疾病中诊断中具有明显优势。【Abstract】 Objective To evaluate low-dose multislice spiral CT for upper urinary tract obstruction in children. Methods From January 2008 to June 2009, 52 children with upper urinary tract obstruction were diagnosed via clinical surgeries. The patients were divided into two groups according to whether having renal calculus (13 patients) or not (39 patients). The patients in non-calculus group were divided into three sub-groups: aged 0-1 (eight patients), 1-5 (16 patients), and 5-10 (15 patients). Low dose multislice spiral CT with different doses was performed. Results The rate of positive predictive diagnosis was 100% in both calculus and non-calculus group. Low dose scan reduced the radiation dose of children. The fixed tube current and the decreased tube voltage (decreased 1/3) led to the decrease of the radiation dose (decreased 70%), which were feasible for diagnosis. Conclusion Low-dose multislice spiral CT was available for upper urinary tract obstruction in children.
Objective To investigate the efficacy of low-dose inhaled nitric oxide (iNO) in the treatment of severe hypoxemia after Sun’s operation. Methods The clinical data of patients undergoing Sun’s operation for acute Type A aortic dissection in our hospital from January 2020 to June 2022 were retrospectively analyzed. Patients who received conventional treatment before November 2021 were enrolled as a control group. After November 2021, iNO was used in our hospital, and the patients who received iNO as an iNO group. The preoperative clinical baseline data, perioperative clinical data and oxygenation index were compared between the two groups. Results A total of 54 patients were included in the control group, including 45 males and 9 females, with an average age of 53.0±10.9 years. A total of 27 patients were included in the iNO group, including 21 males and 6 females, with an average age of 52.0±10.6 years. The preoperative body mass index of the two groups was greater than 25 kg/m2, white blood cell count, C-reactive protein were significantly higher than normal level, but there was no statistical difference between the groups (P＞0.05). There were no statistical differences in intraoperative data between the two groups (P＞0.05). The iNO group had significantly shorter duration of mechanical ventilation, postoperative ICU stay, and postoperative hospital stay than the control group (P<0.001). After 12 h of iNO treatment, hypoxic condition improved obviously, oxygenation indices in 12 h, 24 h, 36 h,48 h, 60 h and 72 h in the iNO group were significantly higher than those in the control group (P<0.05). Conclusion The treatment of severe hypoxemia after Sun’s surgery with low-dose of iNO is safe and effective, can significantly improve oxygenation function, and has significant advantages in shortening ventilator use time, postoperative ICU stay and postoperative hospital stay, but it is not significant in changing postoperative mortality.
The widespread use of low-dose computed tomography (LDCT) in lung cancer screening has enabled more and more lung nodules to get identified of which more than 20% are multiple pulmonary nodules. At present, there is no guideline or consensus for multiple pulmonary nodules whose management is based primarily on the pulmonary imaging characteristics and associated risk factors. Herein, this review covers the imaging methods, CT appearances and management of multiple pulmonary nodules.
目的 探讨双源CT低剂量扫描技术在胸部普通检查中的应用价值。 方法 将2011年8月－2012年12月收治的875例患者依次分为7组，分别采用常规管电流量110 mAs和低管电流量105、100、95、90、85、80 mAs测量，计算并评估7组患者纵隔窗图像的胸骨前空气CT值标准差（SD空气）、肺动脉分叉平面肺动脉信噪比、降主动脉信噪比、肺动脉-竖脊肌对比噪声比、降主动脉-竖脊肌对比噪声比；纵隔窗图像和肺窗图像主观质量评分以及射线剂量指标：CT剂量指数（CTDI）、剂量长度乘积（DLP）、有效剂量（ED）。 结果 7组患者纵隔窗图像肺动脉信噪比、降主动脉信噪比、图像主观质量评分和射线剂量CTDI、DLP、ED之间差异均有统计学意义（P＜0.05）；肺动脉-竖脊肌对比噪声比、降主动脉-竖脊肌对比噪声比之间差异无统计学意义（P＞0.05）；其中第7组图像信噪比、射线剂量和主观质量评分均为最低，部分图像肩背部出现横条状伪影，影响肺尖部病变的显示，难以提供足够的诊断信息。 结论 胸部普通CT检查，通过阶段性降低管电流量使诊断医生逐渐适应低剂量图像质量，从而普及现有设备的低剂量扫描的方法是可行的。双源CT采用85 mAs的参考管电流量，既能获得满足临床诊断的合格图像，又能明显降低患者群体接受的辐射剂量。