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.
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.
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.
Objective To discuss the application of dual-source computed tomography （CT） low dose technology in the upper abdomen enhanced inspection. Methods Six hundred consecutive patients from July 2011 to February 2012 in this hospital were orderly divided into ordinal tube current （210 mAs） group and low dose tube current group （200 mAs，190 mAs，180 mAs，170 mAs，and 165 mAs）. The standard deviation （SD） of subcutaneous fat，signal to noise ratio （SNR） of liver and pancreas， contrast to noise ratio （CNR） of liver-erector spinae and pancreas-erector spinae，score of subjective diagnosis and the indexes of radiation dose，including CT dose index （CTDI），dose length product （DLP），effective dose （ED） were measured，calculated，and assessed respectively on CT images of arterial phase and portal phase from each group. Results The SD of subcutaneous fat， SNRs of liver and pancreas，score of subjective diagnosis，and the CTDI，DLP，ED of CT images in arterial phase and portal phase were significantly different from each other （P＜0.05），while CNRs of liver-erector spinae and pancreas-erector spinae were not statistically significant （P＞0.05）. The SNR，radiation dose，and score of subjective diagnosis of the 165 mAs tube current group were the lowest among all the groups，but the images of the 165 mAs tube current group could not fulfill the need of diagnosis. Conclusions It is really feasible that the method of decreasing tube current gradually in the upper abdomen enhanced CT inspection could ensure that the radiologists could adapt the low dose image bit by bit，and this methods could be popularized to all kinds of CT facilities we own currently. The images with 170 mAs as tube current in the upper abdomen enhanced inspection of dual-source CT could fulfill the need of diagnosis，and the radiation dose of patients is apparently lower than that the conventional scan．
Cone-beam computed tomography (CBCT) is widely used in dentistry, surgery, radiotherapy and other medical fields. However, repeated CBCT scans expose patients to additional radiation doses, increasing the risk of secondary malignant tumors. Low-dose CBCT image reconstruction technology, which employs advanced algorithms to reduce radiation dose while enhancing image quality, has emerged as a focal point of recent research. This review systematically examined deep learning-based methods for low-dose CBCT reconstruction. It compared different network architectures in terms of noise reduction, artifact removal, detail preservation, and computational efficiency, covering three approaches: image-domain, projection-domain, and dual-domain techniques. The review also explored how emerging technologies like multimodal fusion and self-supervised learning could enhance these methods. By summarizing the strengths and weaknesses of current approaches, this work provides insights to optimize low-dose CBCT algorithms and support their clinical adoption.
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.
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.
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.
【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.
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。