能谱CT虚拟平扫替代常规平扫评估甲状腺结节的可行性研究

目的探讨能谱CT碘抑制(MSI)成像作为虚拟平扫(VNC)替代真实平扫(TNC)对甲状腺结节进行评估的可行性。方法回顾性分析2014年2月—10月于我院行常规平扫、能谱成像模式增强扫描的72例甲状腺疾病病人影像资料,采用配对t检验和Wilcoxon符号秩和检验比较TNC与VNC影像上不同组织CT值、客观影像质量、主观影像质量评分、诊断钙化能力及辐射剂量的差异。结果 1在TNC和VNC两种影像上,甲状腺结节病灶、正常甲状腺、颈内动脉的CT值差异均有统计学意义(P0.05),但除正常甲状腺腺体外,其他部位CT值差异均不大(4 HU)。两种影像项部脂肪CT值的差异无统计学意义(P0.05)。VNC影像噪声高于TNC影像,信噪比(SNR)及对比噪声比(CNR)均低于TNC影像(P0.05)。2TNC与VNC主观影像质量评分中位数均为4.0分,VNC的主观评分略低于TNC,两者评分差异无统计学意义(P0.05)。3TNC检出钙化24例,VNC检出22例。TNC与VNC对钙化检出数目的差异无统计学意义(P0.05);TNC测得的钙化长径值较VNC大(P0.05)。4单独能谱增强扫描的剂量长度乘积(DLP)和有效辐射剂量(ED)值明显小于TNC加增强扫描(P0.05),与常规平扫加增强扫描比较,单独能谱增强扫描的有效辐射剂量可降低48.76%。结论在甲状腺CT扫描中,VNC成像对甲状腺结节的诊断具有替代TNC成像的潜在能力。     

光谱CT胸部增强静脉期虚拟血管成像替代三期扫描的可行性研究

目的探讨采用光谱CT胸部增强静脉期图像获得虚拟平扫、虚拟动脉期图像实现一期扫描替代三期扫描的可行性。方法回顾性分析2022年1至5月在昆明医科大学第一附属医院接受光谱CT胸部平扫及双期增强扫描的100例患者的影像资料。对所有患者的静脉期图像进行后处理, 获得虚拟平扫(VNC)及40 keV虚拟单能量图像(VMI)用于模拟动脉期图像(Vart)。采用配对t检验、Wilcoxon检验、McNemar检验对比真实平扫(TNC)与VNC、常规动脉期(CIart)与Vart的图像质量和病灶检出情况。图像质量的客观评价指标包括胸主动脉、各级肺动脉、T4椎体骨松质、胸壁脂肪的CT值、背景噪声、信噪比(SNR)、对比噪声比(CNR);图像质量的主观评分采用5分制双盲法评估。病灶情况的评估包括钙化灶检出率以及肺结节的大小、密度、体积、实性成分占比和影像特征。结果除胸壁脂肪和T4椎体骨松质外, 其他部位CT值在VNC与TNC图像上差异无统计学意义(P>0.05);除右上肺动脉、右下肺动脉外, 其他部位背景噪声值、SNR在TNC图像与VNC图像差异均有统计学意义(P<0.05)。相较于CIart...     

能谱CT虚拟平扫在儿童肝肿瘤中的应用价值

目的:通过能谱CT虚拟平扫水基(WB)图、物质压碘(MSI)图与真实平扫(TNC)对儿童肝肿瘤进行定性和定量研究，探讨虚拟平扫替代真实平扫的可行性。方法:连续性搜集我院30例肝肿瘤患儿，所有患儿均行CT平扫、动脉期、门脉期和实质期扫描。将门脉能谱GSI数据导入后处理工作站生成虚拟平扫WB图和MSI图，对TNC、WB和MSI三组图像进行5分制主观评分和病灶检出能力比较。测量TNC和WB各个部位的CT值和图像背景噪声，计算肝实质和肝肿瘤的信噪比(SNR),比较TNC、WB和MSI三组图像的对比噪声比(CNR)。采用相关样本的符号秩和检验比较TNC与MSI的相关参数，对TNC、MSI、WB图像的CNR值和主观评分分别进行方差分析和Kruskal-Wallis H检验。结果:MSI的SD值、肝肿瘤和腹主动脉的CT值、肝实质和肝肿瘤的SNR值均高于TNC,而肝实质的CT值低于TNC,差异均有统计学意义(P<0.05);三组图像对病灶的检出能力差异无统计学意义(P>0.05)。WB图的CNR(4.74±0.32)高于TNC图(3.07±0.27)和MSI图(3.41±0.28),而MS...     

能谱CT虚拟平扫在肾癌中的应用

目的：探讨能谱CT虚拟平扫(VNC)替代常规平扫在肾癌中的临床应用价值。方法回顾分析32例经病理证实为肾癌的患者影像资料,均行能谱CT常规平扫及动脉期、静脉期能谱成像(GSI),采用MSI软件生成动脉期VNC和静脉期VNC图像。分别测量3组图像(常规平扫、动脉期VNC、静脉期VNC)肾脏病灶的CT值、病灶-正常肾脏的对比噪声比(CNR),同层面病灶的长径、橫径,采用单因素方差分析;由2位放射科医师对3组图像分别行5分制图像质量主观评分,3分制影像学征象主观评分,对2位医师评价结果的一致性行Kappa 检验,对3组图像的图像质量主观评分行单因素方差分析。结果2位医师对3组图像评价结果的一致性较好(Kappa 值均>0.700);3组图像间图像质量主观评分无统计学差异(P>0.05);影像学征象主观评分动脉期 VNC为2.88±0.34,静脉期VNC为2.84±0.37,均可接受。3组图像的CNR分别为0.52±0.11、0.72±0.16、0.69±0.12,动脉期VNC、静脉期 VNC的对比噪声比(CNR)均高于常规平扫,有统计学差异(P<0.05)。3组图像同层面病灶的长径和横径无统计学差异(P>0.05)。3组图像肾脏病灶的CT值分别为(30.04±4.09)HU、(32.69±4.07)HU、(32.56±3.52)HU,有统计学差异(P<0.05),常规平扫病灶的CT值低于动脉期 VNC和静脉期 VNC,但差值均在5 HU内。结论在肾癌检查中 VNC能替代常规平扫,可减少患者的扫描次数,降低辐射剂量。     

双源能谱CT虚拟平扫替代常规平扫评估食管癌的可行性研究

目的探讨双源能谱CT虚拟平扫(VNC)替代常规平扫(TNC)评估食管癌的可行性。方法回顾性收集经胃镜或手术病理证实的食管癌病人46例,所有病人均行TNC及双能量动、静脉双期增强扫描,经双能后处理软件获得动脉期VNC影像。由2名观察者分析TNC和VNC影像上病灶形态学特征(管壁是否增厚、肿瘤与周围组织关系、淋巴结肿大等),并对影像质量进行评分;2组间比较采用卡方检验或Wilcoxon秩和检验,观察者间一致性采用Kappa检验分析。采用配对t检验比较TNC与VNC影像的辐射剂量及其他定量评价参数。结果TNC和VNC影像上显示病灶形态学特征差异均无统计学意义(均P>0.05)。2名观察者对TNC和VNC影像质量主观评分的一致性均较好(均κ>0.75),且对2种影像的主观评分的差异无统计学意义(P>0.05)。2种影像上测得的食管癌病灶处管壁厚度的差异无统计学意义(P>0.05),VNC影像上降主动脉、皮下脂肪CT值高于TNC(P<0.05),但食管癌病灶、椎体后肌肉和空气的CT值差异无统计学意义(P>0.05)。与TNC相比,VNC影像具有较高的SNR和较低的噪声(均P<0.05)。双能量动、静脉期扫描有效辐射剂量小于常规三期扫描(P<0.05),其有效辐射剂量降低了(3.46±0.87)mSv。结论双源能谱CT可为食管癌病人提供与TNC影像质量相似的VNC影像,并降低了辐射剂量。     

双层探测器光谱CT虚拟平扫应用于肺结节人工智能诊断的可行性研究

目的:探讨利用双层探测器光谱CT肺部虚拟平扫(VNC)图像进行肺结节人工智能(AI)诊断的可行性。方法:回顾性分析2022年5－11月间，在南京大学医学院附属鼓楼医院行胸部CT平扫联合双期增强扫描的52例患者资料。选择静脉期扫描数据重建肺窗VNC图像。用AI诊断软件对常规平扫(TNC)和VNC图像进行分析，测量肺实质的CT值和噪声并计算信噪比(SNR)，并由2名放射医师对图像质量进行主观评分。记录各期扫描的剂量长度乘积(DLP)，并计算有效剂量( E)。采用配对 t检验比较2组图像质量客观指标和辐射剂量，采用Wilcoxon非参数检验比较图像质量主观评分。采用Wilcoxon符号秩检验比较2组图像AI诊断的敏感性和假阳性检出率(FPDR)。 结果:与TNC相比，静脉期VNC图像的噪声降低了13.8%，SNR升高14.9%，DLP和 E均降低了33.3%，差异具有统计学意义( t＝5.82、－5.35、22.93、22.92， P <0.05)。2组图像肺实质的CT值及主观评分差异均无统计学意义( P >0.05)。对于不同类型的肺结节，2组图像AI诊断的敏感性差异均无统计学意义( P >0.05)。但对于直径≤4 mm实性结节和全部肺结节总体而言，VNC组的FPDR略有升高，差异具有统计学意义( Z＝－2.03、－3.09， P <0.05)，对于其他类型的肺结节，FPDR差异则无统计学意义( P >0.05)。 结论:基于光谱CT的肺部静脉期VNC图像，在保证图像质量和肺结节AI诊断准确性，且FPDR没有显著升高的情况下，大幅降低患者辐射剂量，可以替代TNC进行常规应用。     

双源CT虚拟平扫图像质量及去除碘油的能力评价

目的：评价肝癌肝动脉化疗栓塞（TACE）术后双源CT虚拟平扫的图像质量以及去除栓塞区域碘油的能力。方法：对40例肝癌TACE术后患者先行常规腹部平扫（TNC）,然后静脉注射对比剂行双能量动脉期、门静脉期增强扫描,之后采用肝脏虚拟平扫后处理软件LiverVNC对双能量强化图像进行处理,得到VNC图像,以TNC图像为标准,评价VNC图像的图像质量及VNC去除碘油的能力,比较图像的信噪比（SNR）、对比信噪比（CNR）、碘油沉积缺损区及病灶周边区CT值并进行统计学分析。结果：VNC具有很强的去除碘油的能力,对于碘油沉积患者,VNC较TNC在图像质量上有所下降,碘油沉积缺损区的CT值VNC较TNC低,差异有统计学意义（TNC动脉期CT值-54．4±19．1,VNC—CT值：44．8±12．9,P〈0．05;TNC门静脉期CT值=54．4±19．1,VNC-CT值=45．3±13．4,P〈0．05）,病灶周边区的CT值VNC与TNc差异无统计学意义（TNC动脉期CT值-56．4±7．6,VNC—CT值=55．1±7．8,P〉0．05;TNC门静脉期CT值：56．4±7．6,VNC—CT值-58．3±8．2,P〉0．05）,病灶的动脉期VNC与门静脉期VNC的CT值差异无统计学意义（碘油沉积缺损区动脉期CT值-44．8±12．9,门静脉期CT值-45．3±13．4,P〉0．05;病灶周边区动脉期CT值-55．1±7．8,门静脉期CT值=58．3±8．2,P〉0．05）。结论：对于较少碘油沉积的病例,VNC能基本满足诊断需求,对于肝癌TACE术后病灶,VNC对病灶周边区的显示好于病灶内。     

双源双能量CT胰腺虚拟平扫的临床应用价值研究

目的 :探讨双源双能量CT胰腺虚拟平扫的临床应用价值。方法 :50例患者行上腹部双源CT常规平扫及动脉期、门脉期、延迟期双能量CT增强扫描,通过双能量"Liver VNC"软件后处理分别得到动脉期、门脉期及延迟期的虚拟平扫图像,比较常规平扫与3组虚拟平扫图像的胰腺平均CT值、竖脊肌平均CT值、SNR、对比噪声比(CNR)、图像主观质量、病灶显示情况及辐射剂量。结果:常规平扫与虚拟平扫图像的胰腺平均CT值、竖脊肌平均CT值差异均无统计学意义(均P0.05);虚拟平扫图像的SNR、CNR均高于常规平扫图像(均P0.05);常规平扫与虚拟平扫所有图像评分均在3分以上,差异有统计学意义(P0.05),均满足临床诊断需要;常规平扫与虚拟平扫图像对病灶有相似的检出功能;双能量扫描虚拟平扫的总有效剂量低于常规扫描(P0.05)。结论:双源双能量CT胰腺虚拟平扫图像质量较常规平扫图像有一定程度下降,但可满足临床诊断需求,同时又减少一次平扫的辐射剂量,且SNR更高,因此具有潜在的临床应用价值。     

双源 CT 双能量虚拟平扫在胸部疾病的临床应用研究

目的：探讨双源 CT(DSCT)双能量虚拟平扫(VNC)技术在胸部疾病的应用价值。方法对60例患者行胸部常规 CT平扫和双能量 CT 增强扫描。对比分析常规 CT 平扫图像与 VNC 图像,测量降主动脉、左心房及胸椎椎体后方肌肉的平均 CT 值、计算信噪比(SNR)、评价二者图像质量、比较辐射剂量。结果60例患者降主动脉的常规平扫与 VNC 平均 CT 值差异有统计学意义(P <0.05);左心房及胸椎椎体后方肌肉平均 CT 值无差异(P >0.05)。VNC 降主动脉、左心房及胸椎椎体后方肌肉的 SNR 均高于常规平扫(P <0.05)。运用增强序列卷积核重建得到的肺窗图像与常规平扫肺窗图像基本一致,对肺实变47例,空洞4例,结节26例,肿块24例,纤维化病变31例,胸膜病变29例二者均能清楚显示(P >0.05)。VNC 图像仅对4(4/49)例肺门区微小钙化灶显示较常规平扫图像模糊。常规平扫与 VNC 图像的质量评分差异无统计学意义。VNC 的容积 CT 剂量指数(CTDIvol)、剂量长度乘积(DLP)、有效剂量(ED)均稍高于常规平扫(P <0.05),但节省1次常规平扫剂量,平均每人可减少2.22 mSv ED。结论DSCT双能量 VNC 技术应用于胸部扫描,其图像质量能达到诊断要求,可有效降低辐射剂量,具有较好的临床应用价值。     

双源CT双能量虚拟平扫对脂肪肝的诊断价值

_目的：探讨双源 CT 双能量腹部虚拟平扫对脂肪肝的诊断价值。方法：回顾性分析采用双源 CT 行腹部双能量增强扫描诊断为脂肪肝的77例患者的平扫期（120 kV）及虚拟平扫（VNC）图像。虚拟平扫图像运用门脉期双能量（100及140 kV）图像重建而来。选择肝门层面测量真实平扫（TNC）与 VNC 图像上肝右叶、肝左叶、脾脏、下腔静脉的 CT 值及噪声,并在肝门层面测量上腹部前后径及左右径。记录整个扫描和平扫期对应的剂量长度乘积（DLP）。评价 TNC 与VNC 图像间各 CT 值及噪声的差异,分析两组图像上肝右叶噪声与前后径、左右径及平均径的关系。分别用肝/脾 CT 值比＜0．8、肝/下腔静脉 CT 值比＜1．0,做为诊断中重度脂肪肝的标准,比较 TNC 和 VNC 图像诊断中重度脂肪肝的一致性。结果：VNC 图像上肝左叶、右叶及脾脏的 CT 值均高于 TNC（P＜0．01）,差异小于10 HU。VNC 图像上各部位噪声均低于 TNC。TNC 图像上,肝右叶噪声与前后径、左右径、平均径均有中等相关性（r＝0．562,0．608,P＜0．01）;在 VNC图像上,肝右叶噪声与上述径线值相关性弱。用肝/脾 CT 值比＜0．8作为诊断重度脂肪肝的标准,VNC 与 TNC 图像诊断重度脂肪肝一致性的 kappa 值为0．591;用肝/静脉 CT 值比＜1．0作为诊断标准,两种图像一致性的 kappa 值为0．458。用 VNC 代替 TNC 图像,可降低24．2％的总扫描剂量。结论：VNC 图像与 TNC 图像在诊断中重度脂肪肝上具有中等的一致性,推荐运用肝/脾 CT 值比＜0．8这一诊断标准。     

Comparative study of hepatic venography using non-linear-blending images,monochromatic images and low-voltage images of dual-energy CT

Objective:

To investigate the use of non-linear-blending and monochromatic dual-energy CT (DECT) images to improve the image quality of hepatic venography.

Methods:

82 patients undergoing abdominal DECT in the portal venous phase were enrolled. For each patient, 31 data sets of monochromatic images and 7 data sets of non-linear-blending images were generated. The data sets of the non-linear-blending and monochromatic images with the best contrast-to-noise ratios (CNRs) for hepatic veins were selected and compared with the images obtained at 80 kVp and a simulated 120 kVp. The subjective image quality of the hepatic veins was evaluated using a four-point scale. The image quality of the hepatic veins was analysed using signal-to-noise ratio (SNR) and CNR values.

Results:

The optimal CNR between hepatic veins and the liver was obtained with the non-linear-blending images. Compared with the other three groups, there were significant differences in the maximum CNR, the SNR, the subjective ratings and the minimum background noise (p < 0.001). A comparison of the monochromatic and 80-kVp images revealed that the CNR and subjective ratings were both improved (p < 0.001). There was no significant difference in the CNR or subjective ratings between the simulated 120-kVp group and the control group (p = 0.090 and 0.053, respectively).

Conclusion:

The non-linear-blending technique for acquiring DECT provided the best image quality for hepatic venography.

Advances in knowledge:

DECT can enhance the contrast of hepatic veins and the liver, potentially allowing the wider use of low-dose contrast agents for CT examination of the liver.CT venography (CTV) is an important non-invasive examination to assess the hepatic veins and plays an important role in the pre-operative evaluation of liver transplants and the diagnosis of hepatic venous diseases.^1,2 Compared with CT hepatic artery angiography or multiphasic liver CT, CTV often requires a larger dose of the contrast agent to achieve sufficient contrast for filling in the hepatic veins.³ Increasing the contrast agent not only increases the economic burden of the patient but also raises the incidence of side effects and complications related to the contrast agent. One of the goals in the advancement of CT techniques is to continuously improve the image quality and clinical applications while reducing radiation exposure and promoting the reasonable use of contrast agents. Several studies suggest that low tube voltage CTV reduces radiation and improves vascular contrast^4–6 because iodinated contrast material is more conspicuous in low-kilovolt peak(kVp) images with an approximately 80% increase in CT attenuation at 80 kVp compared with that at 140 kVp.^6–8Dual-source CT (DSCT) was recently introduced into clinical practice. It can simultaneously acquire low- and high-energy image data using two X-ray tube and detector systems mounted in one gantry.⁹ Dual-energy CT (DECT) could improve the contrast and thereby the image quality of CTV images by virtual monochromatic imaging¹⁰ and non-linear-blending⁸ and linear-blending techniques.^7,11,12 Studies have shown that a DECT non-linear-blending technique could improve the conspicuity of myocardial delayed enhancement.⁸ The clinical application of DSCT undoubtedly greatly aides the choice of a suitable application from a variety of post-processing techniques that can significantly improve the contrast enhancement of hepatic veins. However, the ability to improve the conspicuity of hepatic veins via a dual-source DECT non-linear-blending technique and the performance of non-linear-blending and monochromatic imaging techniques have not been studied. Therefore, the purpose of our study was to improve the image quality of hepatic venography over single-energy CT by using DECT virtual monochromatic imaging and a non-linear-blending technique.     

Synthesized MR images: comparison with acquired images

Synthesized and directly acquired spin-echo images were compared in order to assess the validity of magnetic resonance (MR) image synthesis as a method enabling retrospective formation of images by interactive manipulation of scan parameters. Synthetic images subjectively compared favorably in both accuracy and precision with acquired images when formed for the same values of echo (TE) and repetition times (TR) and for interpolated and extrapolated values of both TE and TR. Plots of synthetic and acquired signals within the same pixel sectors quantitatively showed comparable values for several regions of interest in the brain. Percent error and noise-normalized differences between acquired and synthetic images were tested as a quantitative measure of accuracy. Percent error was consistently less than 5% for brain parenchyma, and synthetic signals were accurate to within four times the noise level at acquisition. The apparent signal-to-noise ratio of synthetic images was comparable, superior, or inferior to similar acquired images, depending on the values of TE and TR. Total acquisition time required for synthetic formation of images for arbitrary values of TE and TR was equivalent to that of a single direct acquisition with a TR of 2,500 msec.     

Registration of two-dimensional cardiac images to preprocedural three-dimensional images for interventional applications

PURPOSE: To evaluate the accuracy and efficiency of rigid-body registration of two-dimensional fast cine and real-time cardiac images to high-resolution and SNR three-dimensional preprocedural reference volumes for application during MRI-guided interventional procedures. MATERIALS AND METHODS: Mutual information (MI) and correlation ratio (CR) similarity measures were evaluated. The dependence of registration accuracy and efficiency on different resolution and SNR parameters, and also on cardiac-phase differences was evaluated in a porcine model. Two-dimensional images were initially misoriented at distances (d) of 2-10 mm, and rotations of +/-5 degrees about all axes. Registration error and computation time were evaluated, and performance was also assessed visually. RESULTS: The maximum registration error using MI (<2.7 mm and <3.6 degrees ) occurred for d = 10 mm, misrotation of +/-5 degrees , and relative SNR = 1. The computation time was 15 seconds for MI and 10 seconds for CR. CONCLUSION: Registration accuracy was not highly dependent on the relative timing, within the cycle, between the two-dimensional and three-dimensional images. Registration using CR was faster than that using MI, although accuracy was marginally higher with MI. J.