可用于高效过滤器检漏的PAO计数扫描法

结合洁净厂房设计和高效空气过滤器的相关规范,介绍了PAO计数扫描检漏方法。

DOP计数扫描法在高效过滤器安装泄漏检测中的应用

高效过滤器安装泄漏检测是空气净化技术检测的关键项目之一,结合实际工程论述了采用DOP计数扫描法检测高效过滤器安装泄漏的应用,对采用气溶胶和粒子计数器的采样要求作了规定。为了提高检漏的工作效率和保证采样结果的有效性,提出增加正压检漏的方法。

S2275肺及全身扫描计数仪原理及其初步应用

介绍了国内首台引进的"S2275肺及全身扫描计数仪"的结构性能及初步应用体会。"S2275肺及全身扫描计数仪"是目前世界上最先进的体外直接测量体内放射性核素种类、沉积部位和放射强度的内照射自动测量系统,可用于核事故受照人员及平时核作业人员内照射监测。

CT灌注扫描技术在急性缺血性脑卒中中的临床应用

目的探讨CT灌注扫描(CTP)技术在急性缺血性脑卒中中的临床应用。方法选取80例临床诊断高度怀疑急性缺血性脑卒中患者作为研究对象,患者均接受CT平扫、CTP技术、CT血管造影(CTA)检查。观察脑部CT平扫、CTP检查结果,比较CTP图像显示治疗前后患者对侧区、梗死区及缺血半暗带区参数。结果80例高度怀疑急性缺血性脑卒中患者经脑部CT平扫后,共检出38例早期低密度病灶,42例无明显异常。80例患者CTP检查发现,8例无缺血半暗带,无明显异常,随访1年后确诊为短暂性脑缺血发作(TIA);72例脑灌注有异常状况,经图像工作站配套软件分析后发现,39例有红色梗死区和黄色缺血半暗带区,33例仅小部分黄色异染区或无典型黄色缺血半暗带,随访1年后确诊为急性缺血性脑卒中。39例患者接受CTP检查图像有梗死区及缺血半暗带区,进一步分析其参数指标显示,其梗死区平均通过时间(MTT)(9.51±0.21)s长于对侧区的(4.51±0.65)s,脑血容量(CBV)(1.68±0.31)ml/100 g、脑血流量(CBF)(5.31±0.42)ml/(100 g·min)低于对侧区的(3.12±0.23)ml/100 g、(51.35±1.32)ml/(100 g·min),差异有统计学意义(P<0.05);缺血半暗带区MTT(7.61±0.51)s长于对侧区(4.51±0.65)s,CBF(31.21±1.36)ml/(100 g·min)低于对侧区的(51.35±1.32)ml/(100 g·min),差异有统计学意义(P<0.05);但缺血半暗带区和对侧区的CBV比较差异无统计学意义(P>0.05);梗死区MTT(9.51±0.21)s长于缺血半暗带区的(7.61±0.51)s,CBV(1.68±0.31)ml/100 g、CBF(5.31±0.42)ml/(100 g·min)低于缺血半暗带区的(3.11±0.21)ml/100 g、(31.21±1.36)ml/(100 g·min),差异有统计学意义(P<0.05)。CTP检查图像显示,治疗后梗死区MTT、CBV、CBF分别为(4.31±1.01)s、(3.18±0.45)ml/100 g、(50.32±1.21)ml/(100 g·min),缺血半暗带区分别为(4.61±1.02)s、(3.15±0.37)ml/100 g、(50.65±1.37)ml/(100 g·min),对侧区分别为(4.51±0.65)s、(3.12±0.23)ml/100 g、(51.35±1.32)ml/(100 g·min)。缺血半暗带区、梗死区与对侧区MTT、CBV、CBF比较,差异无统计学意义(P>0.05)。治疗后梗死区MTT短于本区治疗前,CBV、CBF高于本区治疗前,差异有统计学意义(P<0.05);缺血半暗带区MTT短于本区治疗前,CBF高于本区治疗前,差异有统计学意义(P<0.05)。结论临床可采用CTP技术检查高度怀疑急性缺血性脑卒中患者,通过评估患者颅内CTA、侧支循环状况、脑血流灌注成像状况,为临床诊治急性缺血性脑卒中提供更为客观、全面的信息依据,确保治疗效果。

新兴光子计数计算机断层扫描原理、技术挑战与临床应用分析

近年来,基于光子计数探测器(PCD)的光子计数计算机断层扫描(PCD-CT)已逐步应用于临床实践。相比传统CT,PCD-CT可能会达到微米级空间分辨率、更低的辐射剂量、零电子噪声以及多能量成像和物质识别等,能够促进临床方面超低剂量扫描,并可能发现微小、隐匿性病灶,大幅度提高图像质量。但受限于工艺水平,电荷共享、脉冲堆积、K-电子逃逸和计数率漂移等问题尚未解决,可能会导致图像分辨率和能量分辨率下降,并增加图像噪声和环状伪影等。本文系统阐述了PCD-CT的物理原理、PCD和能量积分探测器(EID)的结构原理差异以及当前PCD-CT发展瓶颈,并分析了三种探测器材料的利弊;然后通过PCD-CT在中国死因占比最高的三种疾病(心血管病、肿瘤、呼吸系统疾病)中的临床应用,具体介绍PCD-CT的临床优势,旨在全面帮助医师理解PCD-CT的技术创新与当前的技术缺陷,并提出未来几年PCD-CT急需解决的问题。

光子计数探测器投影数据噪声的p-范分布统计分析

光子计数型能谱计算机断层扫描(CT)已成为CT成像领域的最新技术,建立精确的噪声模型可以为开发高效的能谱重建算法和降低辐射剂量提供理论支撑。通过对光子计数型能谱CT投影数据噪声进行深入分析和理论推导,提出了能谱CT投影数据噪声的p-范分布模型。首先,综合考虑光子计数探测器能量采集中的光子统计波动和电子热噪声,利用贝叶斯公式推导噪声分布模型。然后经过投影数据的密度函数拟合验证、拟合优度检验等实验环节对所提理论模型进行检验。结果表明,相比于传统分布模型,所提分布模型能够更加精准地刻画光子计数型能谱CT成像机理和物理过程。最后,对投影数据观测序列进行时间序列分析,并将预测得到的结果用于修复异常值。从仿真实验结果和实际数据实验结果可以看出,该预测值具有良好的修复效果。

多层螺旋CT冠状动脉重建技术及其临床应用

多层螺旋CT旋转一周的扫描时间已短至500ms,在心电后门控技术的基础上,应用多层螺旋CT薄层及小螺距扫描心脏后进行冠状动脉重建已成为一项重要的非侵袭性冠状动脉成像手段。本文重点介绍了多层螺旋CT冠状动脉重建的扫描技术和图像后处理方法,并对其临床应用价值作一综述。

温度升高对PSⅡCP47/D_1/D_2/Cyt b559复合物能量传递的影响

采用分幅扫描单光子计数荧光光谱装置 ,研究温度升高对PSⅡCP4 7/D1/D2 /Cytb5 5 9复合物能量传递的影响 .获得分别在 2 0℃、4 2℃和 4 8℃处理后 ,CP4 7/D1/D2 /Cytb5 5 9复合物主发射峰所在的波长未发生多大改变 ,均在 682nm ,但其荧光强度逐渐降低 ,而大约 730nm处主发射峰的振动副带发生了明显的变化 ,4 2℃其弱峰趋势已不显著 ,相对荧光强度下降 ,4 8℃弱峰趋势已完全消失 ;最大峰值处获得两个时间组分 ,这两个组分都属于电荷重组 .其中 ,1～ 2ns组分随处理温度的升高变化不大 ,而 7～ 2 0ns组分随温度升高变化较大 ,并且逐渐延长 .因此 ,处理温度的升高使CP4 7/D1/D2 /Cytb5 5 9复合物的二级结构、色素分布的空间位置发生变化 ,从而影响了CP4 7/D1/D2 /Cytb5 5 9复合物中的能量传递以及电荷重组 .4 2℃已对其造成影响 ,而 4

Comparison of total splenic artery embolization and partial splenic embolization for hypersplenism

AIM:To evaluate whether total splenic artery embolization(TSAE) for patients with hypersplenism delivers better long-term outcomes than partial splenic embolization(PSE).METHODS:Sixty-one patients with hypersplenism eligible for TSAE(n = 27,group A) or PSE(n = 34,group B) were enrolled into the trial,which included clinical and computed tomography follow-up.Data on technical success,length of hospital stay,white blood cell(WBC) and platelet(PLT) counts,splenic volume and complications were collected at 2 wk,6 mo,and 1,2,3,4 years postoperatively.RESULTS:Both TSAE and PSE were technically successful in all patients.Complications were significantly fewer(P = 0.001),and hospital stay significantly shorter(P = 0.007),in group A than in group B.Postprocedure WBC and PLT counts in group A were significantly higher than those in group B from 6 mo to 4 years(P = 0.001),and post-procedure residual splenic volume in group A was significantly less than that observed in group B at 1,2,3 and 4 years post-procedure(P = 0.001).No significant differences were observed in red blood cell counts and liver function parameters between the two groups following the procedure.CONCLUSION:Our results indicate that TSAE for patients with hypersplenism not only delivers a better longterm outcome,but is also associated with lower complication rates and a shorter hospital stay than PSE.

Fractal analysis of thermal conduction of loose coal

For deep mining engineering, heat transfer of coal mass is a vital factor in the thermal environment of coal mines. In order to study the thermal conduction mechanism, we obtained gray images of coal mass microstructure by scanning samples with a digital microscope. With the use of Matlab, these gray images were transformed into binary images, which were then transformed into a corresponding matrix consisting only of the values 0 and 1. According to the calculation method of box-counting dimension, we calculated the fractal dimension of the loose coal to be approximately 1.86. The thermal conductivity expressions of loose coal were derived based on the simulation method of thermal resistance. We calculated the thermal conductivity of loose coal by using a fractal model and compared the calculated values with our experimental data. The results show that the test data show an encourag-ing agreement with the calculated values. Hence fractal theory is a feasible method for studying thermal conductivity of loose coal.

Computing the topology of an arrangement of implicitly defined real algebraic plane curves~§

We introduce a new algebraic approach dealing with the problem of computing the topology of an arrangement of a finite set of real algebraic plane curves presented implicitly. The main achievement of the presented method is a complete avoidance of irrational numbers that appear when using the sweeping method in the classical way for solving the problem at hand. Therefore, it is worth mentioning that the efficiency of the proposed method is only assured for low-degree curves.

The optimal slice thickness of CT in revealing lobulation of malignant solitary pulmonary nodules

Objective： The aim of this study was to determine an optimal slice thickness that was efficient in revealing Iobulation of malignant solitary pulmonary nodules （SPNs） on multi-slice spiral computed tomography （MSCT） images preliminarily. Methods： Fifty patients with malignant SPNs （diameter -〈 3 cm） underwent multidetector-row computed tomography of the chest in a single-breath-hold technique. The raw data were acquired with a collimation of 0.625 mm. Three sets of contiguous images were reconstructed with 1-, 2-, and 5-ram slice thickness, respectively. The Iobulation sign of SPNs on the computed tomography （CT） images presented in 1-, 2-, and 5-ram slice thickness was compared. Using the 1-mm sections as the gold standard, an optimal slice thickness in revealing Iobulation sign of SPNs was determined. Results： The 1-mm-thick images CT revealed 98 Iobulations （25 with chord distance 〈 1 ram; 30 with chord distance 1-2 ram; 43 with chord distance 〉 2 mm） of 45 malignant SPNs. 18 Iobulations with chord distance 〈 1 mm presented in 2-mm-thick sections were as same as those in I-ram-thick sections. Statistically significant difference in Iobulations number was found between that revealed in 2-ram-thick images and that in I-ram-thick images （P = 0.023 〈 0.05）. 16 Iobulations with chord distance 〈 1 mm presented in 5-mm-thick sections were as same as that in I-ram-thick sections. There was statistically significant difference in Iobulations number between that revealed in 5-mm-thick images and that in I-ram-thick images （P = 0.004 〈 0.05）. The 24 Iobulations with chord distance 1-2 mm presented in 2-ram-thick sections were as same as that in 1-mm-thick sections. No statistically significant difference in Iobulations number were found between that revealed in 2-mm-thick images and that in 1-mm-thick images （P = 0.261 〉 0.05）. 13 Iobulations with chord distance 1-2 mm presented in 5-ram-thick sections were as same as that in 1- mm-thick sections. There was statistically significant difference in Iobulations number between that revealed in 5-ram-thick images and that in I-ram-thick images （P = 0.003 〈 0.05）. 40 Iobulations with chord distance 〉 2 mm presented in 2-ram-thick sections were as same as that in I-ram-thick sections. No statistically significant difference in Iobulations number was found between that revealed in 2-ram-thick images and that in I-ram-thick images （P = 0.631 〉 0.05）. 36 Iobulations with chord distance 〉 2 mm presented in 5-mm-thick sections were as same as that in I-ram-thick sections. There was no statistically significant difference in Iobulations number between that revealed in 5-ram-thick images and that in I-ram-thick images （P = 0.264 〉 0.05）. Conclusion： It is suggested that the use of 1-mm slice thickness is suitable in revealing Iobulations with chord distance 〈 1 ram. A 2-mm slice thickness is suggested to be used in revealing Iobulafions with chord distance 1-2 mm and 5-mm slice thickness to be used in revealing Iobulations with chord distance 〉 2 mm.

Measuring the space between vagina and rectum as it relates to rectocele

AIM:To measure the normal space between the posterior wall of the vagina and the anterior wall of the respectively rectum using computed tomography(CT) and reveal its were relationship to rectocele. METHODS:A total of twenty female volunteers without rectocele were examined by CT scan.We performed a middle level continuous horizontal pelvic scan from the upper part to the lower part and collected the measurement data to analyze the results using t-test. RESULTS:Twenty volunteers were enrolled in the study. The space between the posterior wall of the vagina and the anterior wall of the rectum was measured at three levels(upper 1/3,middle,lower 1/3 level of vagina). The results showed that the space from the posterior wall of the vagina to the anterior wall of the rectum at the upper 1/3 level and the middle level was 3.896 ±0.3617 mm and 4.6575±0.3052 mm,respectively. When the two groups of data were compared,we found the space at the upper 1/3 level was shorter than at the middle level(P<0.01).Moreover,at the lower 1/3 level the space measured was 10.058±0.4534 mm.The results revealed that the space at the lower 1/3 level was longer than that at the middle level(P<0.01). CONCLUSION:These measurement data may be helpful in assessing rectocele clinical diagnosis and functional outcomes of rectocele repair.

γ-CT Technique Used for Industrial Multiphase Flow Detection

A gamma-ray Computed Tomography （CT）technique based on MATLAB has been developed,and its potential for the application of multiphase flow detection has been demonstrated with simulation results.Aiming to improve the real time performance,we design a CT system with fixed sources and limited detecors.By dissecting the imaging region with Delaunay triangulation method,the algebraic reconstruction algorithm and simultaneous multiplicative algebraic reconstruction algorithm re implemented respective algebraic reconstruction algorithm are implemented respectively to reconstruct cross-sectional images.The resultant images can be utilized to identify flow regimes or extract characteristic parameters.

Concomitant chemoradiation using gemcitabine in locally advanced hepatocellular carcinoma

Objective:Hepatocellular carcinoma (HCC) is among the most common and rapidly increasing cancers in Pakistan.There is currently no standard management for advanced HCC.The aim of the study was to assess response rate and toxicity of concomitant gemcitabine and external radiation therapy (ERT) in locally advanced HCC.Methods:Sixty patients were enrolled.Gemcitabine,70 mg/m2 was given weekly during ERT.ERT was delivered with 60Co beam up to 30.6 Gy,1.8 Gy/fraction.Tumor response was assessed by computed tomography (CT) at eight weeks.Complete and partial response (CR and PR),progressive and stable disease (PD and SD) were assessed.Hematological,gastrointestinal and hepatic toxicities were assessed weekly.Results:No CR was seen.PR,SD and PD were seen in 33%,40% and 27% of patients respectively.Grade 3/4 toxicity for total leukocyte count and platelets was observed in 7% and 27% patients.Grade 3/4 toxicity for liver failure,bilirubin,aspartate aminotransferase,alanine aminotransferase and alkaline phosphatase was seen in 35%,28%,38%,24% and 43% patients respectively.Conclusion:The study showed that concomitant gemcitabine and ERT is a feasible option with moderate toxicity in advanced HCC.

Computed Tomography Using Level Set Method and Algebraic Reconstruction Technique

In this paper, a novel reconstruction technique based on level set method and algebraic reconstruction technique is proposed for multiphase flow computed tomography (CT) system. The curvature-driven noise reduction method is inserted into the conventional iteration procedure of algebraic reconstruction technique to improve the image quality and convergence speed with limited projection data. By evolving the image as a set of iso-intensity contours after each updation, the sufficient number of iterations for acceptable results is reduced by 80%-90%, while the image quality is enhanced obviously. Quantitative evaluation of image quality is given by using both relative image error and correlation coefficient. The resultant images can be utilized to detect flow regimes for monitoring industrial multiphase flow. Laboratory results demonstrate the feasibility of the proposed method. Phantoms of four typical flow regimes can be reconstructed from few-view projection data efficiently, and the corresponding image errors and correlation coefficients are acceptable for the cases tested in this paper.

In situ investigation of SiC powder's microwave sintering by SR-CT technique

Microwave sintering is being developed as a novel technique for the preparation of dense structural ceramics,but the mature theory has not been established due to the technical difficulties.The synchrotron radiation X-ray computed tomography(SR-CT) technique was introduced for the first time into the study of microwave sintering to in-situ observe the microstructure evolution of silicon carbide(SiC) material in this paper.By applying the SR-CT technique,the reconstructed 2D and 3D images of the specimen were obtained and the double logarithm curve of mean neck size and time(Ln(x)-Ln(t)) were obtained from these reconstructed images.Various sintering phenomena including sintering neck growth during microwave treatment were observed from the reconstructed images.Furthermore,the differences in microstructure evolution and sintering kinetics between microwave and conventional sintering were analyzed based on the reconstructed images and the Ln(x)-Ln(t) curve.1) The sharp surface of grains near the contact region distinctly grew blunt and the sintering neck growth between these grains were obviously observed at the early stage.Besides,the larger particles grew faster than smaller ones.The main reason for these phenomena may be the micro-focusing effect of electric fields.2) During each of the three sintering stages,the sintering kinetics curve of double logarithm relationship between mean neck size and time shows a good linear relationship,but at the middle stage the slope of the curve increases dramatically,which is quite larger than conventional sintering.The preliminary interpretation for these extraordinary phenomena has been discussed in details.