Fatigue properties and damage constitutive model of salt rock based on CT scanning

To investigate the macroscopic fatigue properties and the mesoscopic pore evolution characteristics of salt rock under cyclic loading,fatigue tests under different upper-limit stresses were carried out on salt rock,and the mesoscopic pore structures of salt rock before and after fatigue tests and under different cycle numbers were measured using CT scanning instrument.Based on the test results,the effects of the cycle number and the upper-limit stress on the evolution of cracks,pore morphology,pore number,pore volume,pore size,plane porosity,and volume porosity of salt rock were analyzed.The failure path of salt rock specimens under cyclic loading was analyzed using the distribution law of plane porosity.The damage variable of salt rock under cyclic loading was defined on basis of the variation of volume porosity with cycle number.In order to describe the fatigue deformation behavior of salt rock under cyclic loading,the nonlinear Burgers damage constitutive model was further established.The results show that the model established can better reflect the whole development process of fatigue deformation of salt rock under cyclic loading.

Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.

Hformer:highly efficient vision transformer for low-dose CT denoising

In this paper,we propose Hformer,a novel supervised learning model for low-dose computer tomography(LDCT)denoising.Hformer combines the strengths of convolutional neural networks for local feature extraction and transformer models for global feature capture.The performance of Hformer was verified and evaluated based on the AAPM-Mayo Clinic LDCT Grand Challenge Dataset.Compared with the former representative state-of-the-art(SOTA)model designs under different architectures,Hformer achieved optimal metrics without requiring a large number of learning parameters,with metrics of33.4405 PSNR,8.6956 RMSE,and 0.9163 SSIM.The experiments demonstrated designed Hformer is a SOTA model for noise suppression,structure preservation,and lesion detection.

Value of low-dose and optimized-length computed tomography(CT)scan in CT-guided percutaneous transthoracic needle biopsy of pulmonary nodules

Objective:To investigate the value of application of low-dose and optimized length CT scan on puncture results,complications and patients’radiation dosage during CT-guided percutaneous biopsy of pulmonary nodules(PTNB).Methods:A total of 231 patients with PTNB under CT guidance were collected.Low dose scanning utilized tube current of 20 mA as compared with 40 mA in conventional dosage.Optimized length in CT is defined as intentionally narrowing the range of CT scanning just to cover 25 mm(5 layers)around the target layer during needle adjustment.According to whether low-dose scans and optimized length scans techniques were utilized,patients were divided into three groups:conventional group(conventional sequence+no optimization),optimized length group(conventional sequence+optimized length),and low-dose optimized length group(low dose sequence+optimized length).The ED(effective dose),the DLP(dose length product),the average CTDIvol(Volume CT dose index),total milliampere second between subgroups were compared.Results:Compared with the conventional group,ED,intraoperative guidance DLP,total milliseconds and operation time in the optimized length group were reduced by 18.2%(P=0.01),37%(P=0.003),17.5%(P=0.013)and13.3%(P=0.021)respectively.Compared with the optimized length group,the ED was reduced by 87%,preoperative positioning,intraoperative guidance and postoperative review DLP were also reduced by 88%,total milliampere second was reduced by 79%,with an average CTDIvol was reduced by 86%,in the low-dose optimized length group(P<0.001 for all).Conclusion:Optimizing the length during CT scanning can effectively reduce the intraoperative radiation dose and reduce the operation time compared with conventional plan;low-dose and optimized length CT scan can further reduce the total radiation dose compared with optimized length group with no differences on intraoperative complications,biopsy results and operation time.

基于CT技术的黄原胶加固土干湿循环条件下力学性能和微观结构劣化机制研究

干湿循环对岩土体的工程特性具有重要影响。采用CT扫描技术和力学测试,对加入不同含量黄原胶(0%,0.5%,1.5%)加固的黏土在经历不同次数(0,1,4,8,12次)干湿循环作用下的力学性能和微观结构劣化机制进行了研究,得到结论:(1)黄原胶能够有效提高土体的抗压强度和耐干湿循环效果。随着黄原胶含量的增加,干湿循环作用后的强度损失逐渐减小,当循环次数从0次增加到4次时,对于加入黄原胶含量分别为0%,0.5%,1.5%的试样,抗压强度分别损失了42.75%,17.2%,14.04%。(2)加固土的抗压强度与干湿循环次数之间保持指数下降的关系,当循环次数达到4次后,随着循环次数的进一步增加,抗压强度和弹性模量均在较小的变化范围内波动。(3)随着干湿循环次数的增加,黄原胶加固土的孔隙率表现出先增加后减小的趋势,连通孔隙不断扩展,而孤立孔隙表现出先增加后减小的趋势。(4)随着试样的干燥,黄原胶在土颗粒间形成网状基质,提高土体的强度和耐干湿循环能力。

基于CT断层扫描的木质家具与原木内部缺损三维可视化研究

研究木质家具与原木试件内部缺损三维可视化,有助于木质文物精准干预性保护与木材高效规划利用。凸显三维成像技术可视化优势,对木质文物保护具有重要意义。本文采用philips16排CT——A机型Brilliace16对试件三维断层扫描。通过对CT扫描后原始图像的分割,获取品质较佳的三维数字模型。继而对分割后的图像进行切面与断面两个维度的手工着色,随后通过三维重建可得到开裂、虫洞、朽坏等不同形式缺损的三维形态,并可得到与之对应的精准三维模型。试验证明:通过三维重建,可获取木质试件内部不同类型三维缺损形态的可视化分析,可对缺损形态进行360°观察,并可获取三维缺损形态的表面积、体积等精准物理参数。本技术可为木质文物修复提供三维缺损形态的精准参数及直观可视化三维模型。

CT增强扫描灰度直方图纹理分析技术对肺癌患者术前恶性程度评估及对预后的预测价值

目的探究CT增强扫描灰度直方图纹理分析技术对肺癌患者术前恶性程度评估及对预后的预测价值。方法选择2018年5月至2022年9月在我院就诊的且经术后病理证实的肺癌患者580例作为研究对象。依据术后病理分期,将研究对象分为高分化组(183例)、中分化组(195例)、低分化组(202例)。根据预后情况,将其分为预后良好组(356例)和预后不良组(224例)。由2名医师提取患者CT增强扫描灰度直方图纹理参数。受试者工作特征(receiver operating characteristic,ROC)曲线分析特征参数对肺癌患者术前恶性程度的诊断效能及预后的预测价值。多因素Logistic回归分析预后不良的重要影响因素并构建人工神经网络模型。Pearson分析检验参数间的相关性。结果均值、10%分位、50%分位等参数在高、中、低分化三组中有显著差异。三个参数对评估肺癌患者恶性程度均具有一定的诊断效能,且三者联合诊断效能最佳。均值、10%分位、50%分位是预后不良的保护因素,三者联合预测肺癌患者的曲线AUC值大于各指标单独预测的AUC值。ROC曲线和累积增益图表明该模型预测能力良好。纹理特征参数中,69.44%的参数具有相关性。结论CT增强扫描灰度直方图纹理参数在一定程度上反应肺癌患者术前恶性程度信息,给术前预测以及预后提供了重要方法。

基于CT扫描受压注浆体试块三维孔裂隙结构参数表征

目的为研究注浆体试块单轴压缩过程中孔裂隙结构演化特征,方法以级配砂砾注浆体试块为研究对象,对其单轴压缩过程分阶段进行工业CT扫描,并采用AVIZO对CT切片进行分析,重构孔裂隙结构三维模型,定量表征孔裂隙与孔喉特征参数。结果结果表明:单轴压缩下,试块依次经历孔裂隙萌生、发育、扩展与贯通阶段,孔裂隙演化特征比较明显,萌生阶段孔隙数增幅为14.41%,无明显贯通;发育阶段孔隙数增加326.91%,伴有一定数目孔隙贯通;扩展阶段孔隙数减少了57.79%,孔隙等效直径最大值增幅为223.45%,大部分孔隙贯通为裂隙;贯通阶段孔裂隙数目几乎不变,孔隙等效直径最大值增幅为92.83%,裂隙贯通后形成多个破裂面。峰值后试块出现连通孔隙,该阶段注浆体孔隙与喉道发育完全,试块破坏。结论研究结果可为后续破碎岩石注浆工程实践提供参考。

左心耳CT血管造影双期扫描在房颤患者中诊断左心耳血栓的应用价值

目的:探讨左心耳CT血管造影(CTA)双期扫描在房颤患者中诊断左心耳血栓的应用价值。方法:回顾性收集2020年1月至2022年6月房颤患者36例,所有患者均行左心耳(LAA)CTA双期扫描和经食管超声心动图(TEE)检查。以TEE检查结果为“金标准”,分别计算LAA-CTA第一期和第二期诊断LAA血栓的敏感性、特异性、阳性预测值、阴性预测值及诊断符合率,并采用Kappa检验评价LAA-CTA第一期和第二期诊断结果与TTE诊断结果的一致性。结果:LAA-CTA第一期诊断左心耳血栓患者21例,第二期诊断左心耳血栓患者15例,TTE诊断左心耳血栓患者14例;LAA-CTA第一期诊断LAA血栓的敏感性、特异性、阳性预测值、阴性预测值及诊断符合率分别为64.29%、45.45%、42.86%、66.67%及52.78%;LAA-CTA第二期诊断LAA血栓的敏感性、特异性、阳性预测值、阴性预测值及诊断符合率分别为92.86%、90.91%、86.67%、95.24%、91.67%,差异均有统计学意义(P<0.05)。LAA-CTA第一期诊断左心耳血栓结果与TEE诊断结果一致性一般(Kappa=0.089),而LAA-CTA第二期诊断左心耳血栓结果与TEE诊断结果一致性较好(Kappa=0.827),差异有统计学意义(P<0.05)。结论:左心耳CTA双期扫描均能发现LAA血栓,但第二期扫描诊断血栓的敏感性、特异性及诊断符合率均升高,且第二期诊断血栓结果与TEE一致性较好,因此左心耳CTA双期扫描方法在诊断LAA血栓方面具有较高的临床应用价值。

CT常规扫描与CT小肠造影对小肠肿瘤的诊断价值比较

目的分析CT常规扫描与CT小肠造影对小肠肿瘤的诊断价值。方法选取2019年11月至2021年10月赣南医学院兴国医院的35例疑似小肠肿瘤患者作为研究对象,以病理检查结果为金标准,比较128层螺旋CT常规扫描与128层螺旋CT小肠造影诊断小肠肿瘤的准确度、敏感度、特异度、阳性预测值、阴性预测值,并对比两种检查方式对各类型小肠肿瘤疾病的检出率。结果病理检查结果显示,35例疑似小肠肿瘤疾病患者中,阳性32例,阴性3例。32例阳性患者中,小肠脂肪瘤15例,小肠平滑肌瘤12例,腺瘤5例。CT小肠造影对小肠肿瘤疾病的诊断准确度为94.29%、敏感度为96.88%,CT常规扫描的诊断准确度为71.43%,敏感度为75.00%,CT小肠造影高于CT常规扫描,差异有统计学意义(P<0.05);CT小肠造影对小肠肿瘤疾病诊断的特异度为100.00%,阳性预测值为96.88%,阴性预测值为66.67%,CT常规扫描特异度为50.00%,阳性预测值为88.89%,阴性预测值为12.50%,两种检查方式比较差异无统计学意义(P>0.05)。两种检查方式对各类型小肠肿瘤疾病的检出率比较,差异无统计学意义(P>0.05)。结论对于小肠肿瘤患者,与CT常规扫描相比,CT小肠造影检查准确度、敏感度更高,诊断效能显著。

512层螺旋CT薄层扫描结合计算机人工神经网络对小肠病变的诊断价值研究

目的:运用图像识别和图像描述技术,研究512层螺旋CT薄层扫描结合计算机人工神经网络在小肠病变诊断上的应用价值。方法:建立基于ResNet 101、Faster R-CNN、LSTM的小肠CT图像识别描述人工神经网络模型,采用ResNet 101和Faster R-CNN联合提取图像特征信息进行ROI融合建立图像编码,采用LSTM进行图像解码输出CT图像诊断报告。设计11个病变图像特征标签,选择我院2020年1月—2022年1月行512层螺旋CT薄层扫描病例材料1572套,材料覆盖正常图像及出血、炎性息肉等9种病变类型,按7∶3随机分为训练组和测试组,对模型进行训练并展开性能测试,评价模型输出的CT诊断文字报告质量、诊断准确率及病变部位提取正确率。结果:文字报告质量评分为(4.0325±0.684)分,出现错误评估项样本占比0.8%,仅语句结合约35%存在不合理现象;各病变类型诊断准确率均在97%左右,仅腺癌存在轻微的诊断为腺瘤性息肉现象,整体病变类型诊断正确率97.17%;病变部位正确识别提取率99.43%。结论:基于ResNet 101、Faster R-CNN、LSTM建立人工神经网络模型,进行小肠512层螺旋CT扫描图像的诊断识别,可准确定位图像病变部位,根据病变部位图像特征准确进行病变类型诊断,并就11个CT图像特征进行文字化描述,输出符合医师阅读理解的图像诊断报告,并发现部分医师人工阅片遗漏错误的地方,可为医师提供更为丰富、有效、准确的CT图像诊断信息,有利于医师作出正确的诊断。

基于CT扫描的CO_(2)相变致裂煤裂隙演化特征

为进一步揭示CO_(2)相变致裂煤的裂隙改造机理,开展了CO_(2)相变致裂煤体实验,基于CT扫描和三维裂隙重构,分析了CO_(2)相变致裂前后的煤样内部裂隙结构参数,查明了CO_(2)相变致裂煤的三维裂隙结构演化特征。结果表明,致裂后煤样的裂隙总数量减少,裂隙总体积和裂隙总表面积增加;CO_(2)相变致裂产生了裂隙扩张转化效应,在致裂压力的扩张作用下,小尺度裂隙转化为更大尺度的裂隙;长度小于1000μm的裂隙数量减少、裂隙体积和表面积明显减小,长度大于1000μm的裂隙体积和表面积明显增大,且裂隙之间扩张贯通而引起其数量减少;CO_(2)相变致裂大幅度改善了煤体三维裂隙的连通性,有利于气体的运移和产出。此研究为CO_(2)相变致裂效果提供新的分析评价方法,也可为其他非常规天然气储层及其改造的裂隙演化特征研究提供参考和借鉴。

比较腹盆腔增强CT、盆腔MRI平扫在正确预测淋巴结状态方面的诊断性能

目的探讨在卵巢癌淋巴结转移诊断中,腹盆腔增强CT与盆腔MRI平扫的诊断性能对比。方法选取卵巢癌患者46例作为研究对象,安排接受腹盆腔增强CT与盆腔MRI平扫,以病理结果为参照计算两种方法的灵敏度、特异度、阳性预测值以及阴性预测值。结果CT扫描检查结果显示,腹盆腔增强CT在卵巢癌盆腔淋巴结转移诊断中,灵敏度为45.00%,特异度为73.08%;盆腔MRI平扫在卵巢癌盆腔淋巴结转移诊断中,灵敏度为60.00%,特异度为80.77%;腹盆腔增强CT联合盆腔MRI平扫在卵巢癌盆腔淋巴结转移诊断中,灵敏度为85.00%,特异度为92.31%。结论在卵巢癌淋巴结转移诊断中,相较于腹盆腔增强CT,盆腔MRI具有较高的诊断灵敏度和特异度,但两者联合运用取得的诊断效能更高。

基于CT扫描研究颗粒形状对砂土力学性质的影响

为了探究颗粒形状对砂土力学性质的影响,选取玻璃珠、石英砂、玻璃渣3种颗粒形状差异较大的砂土作为研究对象。首先通过计算机断层(computed tomography,CT)扫描重构了3种砂土的三维结构,选取了伸长率(EI)、扁度(FI)、球度(S)3个表征颗粒形状参数的均值作为砂土颗粒整体形状参数(overall regularity,OR),并对整体形状参数OR进行统计分析。然后配制7种不同形状参数的砂土进行了常规三轴压缩试验得到了其力学强度参数,研究砂土颗粒形状对其力学强度的影响规律。结果表明:7种砂土的应力-应变曲线均为应变软化型,都呈现出先剪缩后剪胀的特性;整体形状参数OR能较好反映砂土的力学特征,即随着整体形状参数OR的减小,应变软化现象变得不明显,但其峰值偏应力呈增大的趋势;砂土的内摩擦角随整体形状参数OR的减小呈线性增长,表观黏聚力急剧增大,但最大剪胀角随OR的减小而减小。此外,将临界内摩擦角与整体形状参数OR进行线性拟合,得到了两者较好的线性关系。

术前多排螺旋CT三期增强扫描对非小细胞肺癌纵隔淋巴结转移的诊断价值

目的探讨多排螺旋CT(MSCT)三期增强扫描对非小细胞肺癌(NSCLC)纵隔淋巴结转移(MLNM)中的术前诊断价值。方法回顾性分析80例NSCLC患者的临床资料,术前均行MSCT三期增强扫描,以术后病理结果为金标准,使用Kappa一致性检验评价MSCT三期增强扫描在术前诊断MLNM的诊断效能。结果术后病理检查证实80例NSCLC患者中,N0期31例,N1期24例,N2期25例,其中MLNM 25例(31.25%);术前MSCT诊断N0期34例,N1期24例,N2期22例,术前MSCT对NSCLC患者N分期诊断与术后病理一致性一般(Kappa=0.735);25例合并MLNM患者中,术前MSCT确诊19例,其对NSCLC患者MLNM的诊断与病理结果一致性一般(Kappa=0.531),其诊断的灵敏度、特异度、准确度、阳性预测值和阴性预测值分别为76.00%、80.00%、78.75%、63.33%和88.00%;纵隔淋巴结转移率在不同肿瘤直径、胸膜凹陷与否、不同肿大淋巴结位置、累及粗大肺静脉与否以及不同淋巴结短径的NSCLC患者间比较均有统计学意义(P<0.05)。结论术前MSCT三期增强扫描诊断NSCLC患者MLNM具有一定的准确性,结合原发病灶大小、胸膜凹陷、肿大淋巴结位置、累及粗大肺静脉等多方面信息可为淋巴结清扫提供重要参考。

螺旋CT扫描结核分枝杆菌肺病影像学特点及诊断价值研究

目的研究螺旋CT扫描应用于结核分枝杆菌肺病患者影像学特点和临床诊断价值。方法选取2021年10月—2023年2月本院结核分枝杆菌肺病患者155例作为本次研究对象,采用回顾性分析资料的方式进行研究。所有患者均进行螺旋CT扫描检查,并以病理学、细菌学以及纤维支气管镜诊断作为金标准,分析患者影像学特点、诊断价值。结果分析影像学特点,经螺旋CT扫描检查155例,显示存在斑片浸润征象、散播病灶、条索节结征象、胸膜增厚、多发空洞、肺不张、胸腔积液,其中斑片浸润征象(89.03%)、散播病灶(69.68%)、条索节结征象(63.23%)占比较高。分析诊断价值,经金标准检查出阳性120例,阴性35例。采用螺旋CT扫描后,检查出阳性117例,阴性32例。经螺旋CT扫描诊断,阳性检出率(77.42%)、灵敏度(97.50%)、特异度(91.43%)、阳性预测值(97.50%)、阴性预测值(91.43%),其与金标准对比,差异无统计学意义(P>0.05)。诊断符合率(96.13%)虽然与金标准对比,差异无统计学意义(P>0.05)。结论针对结核分枝杆菌肺病患者,实施螺旋CT扫描能够尽早较为精确诊断,诊断效果较高,可较为清晰观察影像学特点,具有重要参考价值,有利于为患者尽快制定治疗方案,在临床诊断方案中值得大力实施以及推广。

Mortality outcomes of low-dose computed tomography screening for lung cancer in urban China:a decision analysis and implications for practice

Background: Mortality outcomes in trials of low-dose computed tomography(CT) screening for lung cancer are inconsistent. This study aimed to evaluate whether CT screening in urban areas of China could reduce lung cancer mortality and to investigate the factors that associate with the screening effect.Methods: A decision tree model with three scenarios(low-dose CT screening, chest X-ray screening, and no screening) was developed to compare screening results in a simulated Chinese urban cohort(100,000 smokers aged45-80 years). Data of participant characteristics were obtained from national registries and epidemiological surveys for estimating lung cancer prevalence. The selection of other tree variables such as sensitivities and specificities of low-dose CT and chest X-ray screening were based on literature research. Differences in lung cancer mortality(primary outcome), false diagnoses, and deaths due to false diagnosis were calculated. Sensitivity analyses were performed to identify the factors that associate with the screening results and to ascertain worst and optimal screening effects considering possible ranges of the variables.Results: Among the 100,000 subjects, there were 448,541, and 591 lung cancer deaths in the low-dose CT, chest X-ray, and no screening scenarios, respectively(17.2% reduction in low-dose CT screening over chest X-ray screening and 24.2% over no screening). The costs of the two screening scenarios were 9387 and 2497 false diagnoses and 7and 2 deaths due to false diagnosis among the 100,000 persons, respectively. The factors that most influenced death reduction with low-dose CT screening over no screening were lung cancer prevalence in the screened cohort, lowdose CT sensitivity, and proportion of early-stage cancers among low-dose CT detected lung cancers. Considering all possibilities, reduction in deaths(relative numbers) with low-dose CT screening in the worst and optimal cases were16(5.4%) and 288(40.2%) over no screening, respectively.Conclusions: In terms of mortality outcomes, our findings favor conducting low-dose CT screening in urban China.However, approaches to reducing false diagnoses and optimizing important screening conditions such as enrollment criteria for screening are highly needed.

Quantitative investigation of multi-fracture morphology during TPDF through true tri-axial fracturing experiments and CT scanning

Due to the reservoir heterogeneity and the stress shadow effect, multiple hydraulic fractures within one fracturing segment cannot be initiated simultaneously and propagate evenly, which will cause a low effectiveness of reservoir stimulation. Temporary plugging and diverting fracturing(TPDF) is considered to be a potential uniform-stimulation method for creating multiple fractures simultaneously in the oilfield. However, the multi-fracture propagation morphology during TPDF is not clear now. The purpose of this study is to quantitatively investigate the multi-fracture propagation morphology during TPDF through true tri-axial fracturing experiments and CT scanning. Critical parameters such as fracture spacing, number of perforation clusters, the viscosity of fracturing fluid, and the in-situ stress have been investigated. The fracture geometry before and after diversion have been quantitively analyzed based on the two-dimensional CT slices and three-dimensional reconstruction method. The main conclusions are as follows:(1) When injecting the high viscosity fluid or perforating at the location with low in-situ stress, multiple hydraulic fractures would simultaneously propagate. Otherwise, only one hydraulic fracture was created during the initial fracturing stage(IFS) for most tests.(2) The perforation cluster effectiveness(PCE) has increased from 26.62% during the IFS to 88.86% after using diverters.(3) The diverted fracture volume has no apparent correlation with the pressure peak and peak frequency during the diversion fracturing stage(DFS) but is positively correlated with water-work.(4) Four types of plugging behavior in shale could be controlled by adjusting the diverter recipe and diverter injection time, and the plugging behavior includes plugging the natural fracture in the wellbore, plugging the previous hydraulic fractures, plugging the fracture tip and plugging the bedding.

Optimum Threshold Estimation of Thorax CT Scan for COVID-19 Diagnosis in a Single Center in Cameroon

Objective: To evaluate the lung CT scan as a possible predictive diagnostic method for COVID-19 in the Cameroonian context. Methods: We designed a cross sectional study. Suspected cases of COVID-19 during the first wave at the national social insurance fund (NSIF) hospital were screened with both COVID-19 with lung CT scan and a PCR test. Univariate analysis was performed for sample description and multivariate analysis to assess the correlation between positive results for the PCR and other parameters. We estimated the optimum threshold of sensitivity/specificity, and area under curve using the empirical method and package. Results: A total of 62 suspected COVID-19 cases were recorded, predominantly males (Sex Ratio = 2.2) with a median age of 58.5 (IQR = 19.7). Among our 62 patients, 29 (46.8%) were confirmed COVID-19 cases with positive PCR results. All the patients had a thorax CT scan with a median impairment of 40% (IQR = 20%). The optimum threshold estimate for CT scan for COVID-19 infection diagnosis was 60% (95% CI = 25% - 80%). Overall, the sensitivity and specificity estimates were 0.30 (95% CI = 0.15 - 0.49) and 0.87 (95% CI = 0.70 - 0.96), respectively, leading to an Area Under Curve (AUC) estimate of 0.59 (95% CI = 0.46, 0.71). Conclusion: In this setting, lung CT scan was neither sensitive nor specific to predict COVID-19 disease.

CT用于非人体目标几何体的三维重建

当被扫描物体存在镂空、遮挡和狭小空间时,需要大量图像拍摄或激光扫描工作;利用三维点云构建三角网格时,需要大量人工交互操作,且三维面绘制容易丢失特征信息。为解决上述问题,提出了采用CT对非人体目标几何体进行三维重建,再用体绘制进行显示的方法。基于医用CT对瓷器、陶器、木器和青铜器等材质的工艺品进行三维扫描,直接基于体绘制算法进行三维显示,同时提取CT图像轮廓点实现面绘制建模。结果表明,CT扫描重建精度高、体绘制效果好且人工工作量小、速度快。因此CT扫描及体绘制在非人体目标的三维重建中具有可行性,并且可以提高效率和精度。