iDose迭代重建算法对上腹部CT图像质量的影响

目的 比较不同水平的iDose迭代重建算法对上腹部CT增强扫描门静脉期图像质量的影响,获取本组图像质量相对较好的iDose迭代水平.方法 采用256层螺旋CT扫描仪对60例患者行4期上腹部CT增强扫描,对门静脉期的图像采用滤波反投影(FBP)、iDose1、iDose3、iDose5共4种方式的重建,比较不同重建方式下图像客观质量,包括噪声、信噪比(SNR)、对比噪声比(CNR),以及主观质量(噪声、锐利度、对比度、伪影、细小结构的清晰度)的差异.结果 4组图像的客观质量差异均有统计学意义(P＜0.05),iDose各组图像的客观噪声均低于FBP组,而SNR、CNR均高于FBP组(P＜0.05),iDose5组的SNR、CNR最高.与FBP组相比,iDose各组图像的主观噪声更低,锐利度、对比度及细小结构清晰度更好(P＜0.05),4组图像的伪影差异无统计学意义(P＞0.05).iDose3水平重建后图像的总体指标最好.结论 常规上腹部CT增强扫描时,应用iDose迭代算法重建后图像的噪声降低,总体质量提高.     

FBP 、iDose4和 IMR3种重建算法对低剂量胸部 CT 图像质量的影响

目的：探讨滤波反射投影（FBP）、混合迭代算法（iDose4）和全迭代模型重建（IMR）3种重建技术对低剂量胸部薄层CT图像质量的影响。方法应用飞利浦256层CT ,收集30例怀疑肺部疾病行胸部CT平扫的患者。扫描条件：管电压80 kVp ,管电流80 mAs。所得原始数据采用FBP、iDose4、IMR＿soft（L1＿Body＿Soft＿Tissue）及IMR＿routine（L1＿Body＿Routine）算法进行重建,重建层厚1 mm ,层间距0．5 mm。测量并记录图像噪声、信噪比（SNR）及对比噪声比（CNR）。采用4分法分别对肺窗及纵隔窗进行图像质量的评估。对比分析4组3种不同重建算法的定性及定量参数。结果4组的图像噪声值分别为55．7±20．7,37．0±13．0,13．4±4．9和19．5±7．9。与FBP组相比,iDose4组、IMR＿soft组及IMR＿routine组3组的噪声分别降低了33．5％,75．9％,65％（ P均＜0．001）。IMR＿soft及IMR＿routine 3组的SNR及CNR均明显高于FBP组（P均＜0．001）。iDose4组的SNR及CNR值高于FBP组,但差异无统计学意义（P值分别为0．08,0．91）。IMR＿soft及IMR＿routine 2组的SNR及CNR均高于iDose4组（P均＜0．001）,但2组之间差异无统计学意义（P＞0．05）。IMR＿routine组肺窗图像质量评分高于其他3组,但与IMR＿soft组差异无统计学意义。IMR＿soft组纵隔窗图像质量最高,与FBP、iDose42组差异有统计学意义（P均＜0．01）,但与IMR＿routine组差异无统计学意义（P＞0．05）。结论与FBP重建算法相比较,在低剂量条件下,iDose4及IMR均可明显降低图像噪声及提高图像质量,其中IM R重建算法降噪及提高图像质量效果更为显著。     

单源双能 CT 不同重建层厚对标准水模 GSI 数据的影响

目的：探讨单源双能 CT 不同重建层厚对标准水模能谱成像的 CT 值、水(碘)浓度、SD 值的影响。方法使用 GE 公司单源双能 CT(Discovery CT 750 HD),选择辐射剂量相近(165~262.5 mAs)的8个扫描协议,对 GE 20 cm 直径的水模行 CT 能谱成像(GSI)扫描,管电压采用140 kVp 和80 kVp 瞬时切换,扫描视野 medium,螺距1.375,探测器宽度40 mm,每个协议采集6层5 mm 层厚图像(B 组),重建1.25 mm 层厚图像(A 组)。使用 AW4.5工作站,将面积约3000 mm2的圆形感兴趣区(ROI)置于水模的中心、3点、6点、9点、12点的位置进行测量,分别在70 keV 单能量图像上测量 A、B 2组的 CT 值和 SD 值,在水(碘)基图像上测量水(碘)浓度和 SD 值,分别采用独立样本 t 检验、配对样本 t 检验进行统计学分析。结果A 组及 B 组 CT 值和水(碘)浓度的差异无统计学意义(P >0.05),SD 值的差异有统计学意义(P <0.05)。A、B 2组水(碘)浓度的 SD 值均小于 CT 值的 SD 值,差异有统计学意义(P <0.05)。结论重建层厚的改变不会影响单源双能 CT GSI 扫描的 CT 值和水(碘)浓度,对 SD 值有影响。GSI 对物质浓度的测量及 CT 值测量更加准确。     

基于不同重建算法的PET重建参数优化研究

目的：应用PET/CT模型评估不同重建算法条件下PET重建参数优化方案。方法：参照国际电工协会（IEC）标准中PET/CT测试模型的要求,采用聚甲基丙烯酸甲酯材料制作模型,内部配有直径大小不一的圆柱体用于模拟病灶。向小圆柱体和模型分别注入不同浓度的18F-FDG溶液,模拟放射性药物在人体内的分布情况。采用不同的重建算法及重建参数对PET/CT原始图像进行重建,通过对比分析不同重建条件下图像的放射性计数、对比度、背景变化率和信噪比进行图像质量评估。结果：当重建算法相同时,16子集3次迭代的条件下具有最为均衡的图像质量。相比于有序子集期望值最大化（OSEM）算法组,True-X组的背景变化率较低,并具有更高的对比度百分数和信噪比,差异具有统计学意义（均P<0.05）。结论：自制PET/CT模型可以作为临床工作中重建参数优化以及图像质量控制的有效研究工具。PET/CT重建参数可优先选用16子集3次迭代和True-X高清重建算法。     

螺旋CT薄层重建技术对肺错构瘤的诊断价值

目的：探讨螺旋CT薄层重建技术对肺错构瘤的诊断价值。方法分析21例经手术病理证实的肺错构瘤患者,先行胸部常规CT扫描,再行CT薄层重建。观察2种图像上病灶的边缘特征及内部特征,将观察结果行卡方检验,以P<0.05为差异显著标准。结果常规CT与薄层重建图像比较：①分叶征的显示率相同,均为12例(57.1%)。②钙化的显示率相同,均为9例(42.9%)。③脂肪的显示率分别为3例(14.3%)和9例(42.9%),差异有统计学意义(χ2=4.200,P<0.05)。④常规CT与薄层重建对血管穿过征的显示率分别为3例(14.3%)和10(47.6%),差异有统计学意义(χ2=5.459,P<0.05)。结论 CT薄层重建较常规 CT能更好地显示肺错构瘤的内部特征,提高诊断正确率。     

探究1024×1024重建矩阵结合Karl算法对CT门静脉成像的门脉图像质量和肝脏体积测量的影响

目的：探究1 024×1 024重建矩阵结合Karl算法对CT门静脉成像的门脉图像质量和肝脏体积测量的影响。方法：回顾性分析行全腹部增强CT检查的患者40例,所有患者均采用联影uCT760进行扫描。成像参数：管电压120 kV,管电流设置为剂量调制等级3,重建512×512矩阵,Karl 5级图像,获得图像为常规组(A组)。使用常规组的原始数据重建得到实验组(B组)图像：采用1 024×1 024矩阵,结合Karl 5、7、9级重建获得B₁～B₃组图像。应用联影智能科研平台系统测量肝脏体积,比较A、B两组门静脉和肝脏CT值、标准差(SD)值、对比噪声比(CNR)、肝脏体积值及图像主观评分。结果：B组门静脉和肝脏CT值与A组比较差异无统计学意义(P=0.079～0.766)。随着Karl等级的提高,B组门静脉和肝脏的SD值逐渐下降(P<0.001),CNR逐渐升高(P<0.001),肝脏体积值差异无统计学意义(P=0.999)。主观评价上,随着Karl等级的增加,B组伪影评分逐渐降低(P<0.05),图像噪声、门静脉边缘锐利度...     

多模型迭代重建算法在提高常规剂量胸部CT图像质量的临床价值

目的 探讨基于多模型的迭代重建算法(ASIR-V)和自适应统计迭代重建算法(ASIR)在常规剂量胸部CT检查中降低图像噪声和提高图像质量的临床价值.方法 选取行宝石能谱CT常规剂量胸部平扫患者30例.所有患者均采用自动管电流调制技术,预设噪声指数为14,对同一患者所得图像采用10％～100％(间隔10％)的不同权重AS...     

肥胖患者80 kV与120 kV不同重建算法CTPA图像质量分析

目的 分析肥胖患者高、低管电压迭代重建(IR)算法与滤波反投影(FBP)算法的CT肺动脉造影(CTPA)图像质量及辐射剂量,探讨低管电压IR算法在肥胖患者CTPA中的可行性.方法 将临床疑似肺栓塞需行CTPA检查的肥胖患者随机分为80 kV或120 kV组,均采用IR及FBP方式对图像进行后处理.测量肺动脉主干、右肺上叶动脉及右肺下叶后基底段动脉的CT值,计算肺动脉平均CT值,采用独立样本t检验分析.结果 高、低管电压组IR亚组的肺动脉CT值与FBP亚组相比,差异无显著性(P>0.05),噪声、信噪比(SNR)、对比噪声比(CNR)的差异有统计学意义(P<0.05).80 kV组的肺动脉CT值、噪声、SNR、CNR均明显高于120 kV组,且差异有统计学意义(P<0.05),而辐射剂量均明显低于120 kV组,差异亦有统计学意义(P=0.000).结论 与120 kV联合FBP算法相比,80 kV联合IR算法的CTPA图像质量明显提高,且患者所受辐射剂量明显降低,可用于肥胖患者的CTPA.     

深度学习图像重建算法在头部非增强扫描中的价值:尸头研究

目的 深度学习图像重建算法(DLIR)在头部非增强CT中降噪及降低辐射剂量的可能性研究.方法 采用256排CT对成人尸头进行常规剂量(A组)和低剂量(B组)扫描,2组原始数据分别采用滤波反投影法(FBP)和DLIR低(DLIR-L)、中(DLIR-M)、高(DLIR-H)3档重建.测量组织CT值、噪声(SD)值,计算信...     

重建算法影响计算机辅助检测评价低剂量CT肺气肿定量和支气管成像

目的 比较基于模型的迭代重建(MBIR)、自适应迭代重建(ASIR)和滤波反投影(FBP)重建对计算机辅助检测(CAD)低剂量CT(LDCT)条件下肺气肿定量和气道成像的影响.资料与方法 收集接受胸部LDCT受检者36例,分别采用FBP、ASIR和MBIR重建.应用CAD进行肺气肿定量和提取分析右肺上叶支气管长度.由2...     

Quantitative analysis of emphysema in 3D using MDCT: influence of different reconstruction algorithms

PURPOSE: The aim of the study was to compare the influence of different reconstruction algorithms on quantitative emphysema analysis in patients with severe emphysema. MATERIAL AND METHODS: Twenty-five patients suffering from severe emphysema were included in the study. All patients underwent inspiratory MDCT (Aquilion-16, slice thickness 1/0.8mm). The raw data were reconstructed using six different algorithms: bone kernel with beam hardening correction (BHC), soft tissue kernel with BHC; standard soft tissue kernel, smooth soft tissue kernel (internal reference standard), standard lung kernel, and high-convolution kernel. The only difference between image data sets was the algorithm employed to reconstruct the raw data, no additional radiation was required. CT data were analysed using self-written emphysema detection and quantification software providing lung volume, emphysema volume (EV), emphysema index (EI) and mean lung density (MLD). RESULTS: The use of kernels with BHC led to a significant decrease in MLD (5%) and EI (61-79%) in comparison with kernels without BHC. The absolute difference (from smooth soft tissue kernel) in MLD ranged from -0.6 to -6.1 HU and were significant different for all kernels. The EV showed absolute differences between -0.05 and -0.4 L and was significantly different for all kernels. The EI showed absolute differences between -0.8 and -5.1 and was significantly different for all kernels. CONCLUSION: The use of kernels with BHC led to a significant decrease in MLD and EI. The absolute differences between different kernels without BHC were small but they were larger than the known interscan variation in patients. Thus, for follow-up examinations the same reconstruction algorithm has to be used and use of BHC has to be avoided.     

MSCT薄层重建对表现为肺纯磨玻璃结节的肺腺癌浸润性的定量分析

目的通过对表现为纯磨玻璃结节(pGGN)的浸润性肺腺癌组和非浸润性肺腺癌组的CT影像特征定量分析,提高两组之间的鉴别诊断。方法选取并分析经手术及病理确诊的151例表现为单发pGGN患者,其中非浸润性腺癌组包括不典型腺瘤样增生(AAH)46例,原位癌(AIS)49例;浸润性腺癌组包括微浸润腺癌(MIA)31例,浸润性腺癌(IA)25例,所有患者确诊前均行MSCT肺部平扫并1 mm薄层重建。在薄层重建图像上测量所有pGGN最大截面面积、平均CT值,分析胸膜牵拉征、空泡征、毛刺征、分叶征及支气管充气征等征象。对pGGN最大截面面积及平均CT值做ROC曲线。结果 pGGN最大截面面积、平均CT值、空泡征、分叶征及毛刺征在浸润性肺腺癌组和非浸润性肺腺癌组之间差异有统计学意义(P<0.05)。病灶最大截面面积及平均CT值诊断价值较好,两者联合ROC曲线AUC值为0.916,敏感度为81.8%,特异度为90.4%。结论 pGGN最大截面面积、平均CT值、空泡征、分叶征及毛刺征均有助于鉴别浸润性肺腺癌和非浸润性肺腺癌,其中最大截面面积和平均CT值诊断价值较大,两者联合AUC值较单一指标显著增高。     

Evaluation of ultra-low-dose thoracic multi-detector-row CT using different reconstruction kernels and new reconstruction algorithms

CT has great advantages in detecting early-stage small lung cancer and is becoming common in lung cancer screening. Multi-detector-row CT (MDCT) can provide thin-slice images with low radiation exposure. In this study, ultra-low-dose (5 mAs: 10 mAs, 0.5 sec/rot) thoracic MDCT images were evaluated. We describe the differences in image quality and quantity between the different reconstruction kernels. We also propose a new reconstruction algorithm (ultra-low-dose reconstruction algorithm: ULR) for ultra-low-dose thoracic CT, to reduce noise and streak artifacts. We are convinced of the usefulness and possibility of ultra-low-dose thoracic MDCT with ULR algorithms for lung cancer screening.     

Quantitative evaluation of several partial fourier reconstruction algorithms used in mri

Partial Fourier reconstruction algorithms exploit the redundancy in magnetic resonance data sets so that half of the data is calculated during image reconstruction rather than acquired. The conjugate synthesis, Margosian, homodyne detection, Cuppen and POCS algorithms are evaluated using spatial frequency domain analysis to show their characteristics and where limitations may occur. The phase correction used in partial Fourier reconstruction is equivalent to a convolution in the frequency domain and the importance of accurately implementing this convolution is demonstrated. New reconstruction approaches, based on passing the partial data through a phase correcting, finite impulse response (FIR), digital filter are suggested. These FIR and MoFIR algorithms have a speed near that of the Margosian and homodyne detection reconstructions, but with a lower error; close to that of the Cuppen/POCS iterative approaches. Quantitative analysis of the partial Fourier algorithms, tested with three phase estimation techniques, are provided by comparing artificial and clinical data reconstructed using full and partial Fourier techniques.     

图像重建方法对门控核素心肌灌注显像室壁相位分析的影响

目的 评价几种常用的SPECT门控核素心肌灌注显像（GSPECT MPI）图像迭代重建方法对相位分析的影响。方法对所选的30例患者应用Philips Cardio MD系统采集GSPECTMPI图像,分别使用滤波反投影（FBP）、最大似然一最大期望值（MLEM）、带三维分辨率恢复的MLEM（AST）、带衰减校正（AC）的MLEM及带AC和蒙特卡罗散射校正（ACSC）的MLEM对GSPECT数据进行重建。将重建数据传递至SyncTool,以测量左心室不同步参数（相位标准差和直方图带宽）。使用配对t检验比较由FBP和以上各种迭代法所得到的左心室不同步参数。结果负荷GSPECTMPI相位分析结果中由FBP、MLEM、带AC的MLEM、带ACSC的MLEM、AST所得到的相位标准差分别为11．6°,10．9°,11．2°,11．6°,11．4°;直方图带宽分别为35．7°,34．3°,35．1°,36．9°,35．1°。静息GSPECTMPI相位分析结果中由上述5种方法所得到的相位标准差分别为15．2°,14．5°,15．4°,15．4°,14．8°;直方图带宽分别为47．3°,46．4°,46．4°,47．9°,46．1°。负荷显像时从各迭代方法和FBP所得到的左心室不同步参数之间差异无统计学意义（t值-1．179～1．554,P均〉0．05）,静息显像时各参数间差异亦无统计学意义（t值-0．714—0．666,P均〉0．05）。结论标准FBP重建已足够用于精确的相位分析,SyncTool测量左心室不同步的技术可广泛应用于临床。     

Quantitative analysis of technegas SPECT: evaluation of regional severity of emphysema.

The purpose of this study was to quantify the regional severity of emphysema by 3-dimensional fractal analysis of technegas (99mTc-carbon particle radioaerosol) SPECT images. METHODS: Technegas SPECT was performed on 22 patients with emphysema. The lungs were delineated using 4 cutoff levels (15%, 20%, 25%, and 30% of the maximal pixel radioactivity), and the total number of pixels was measured in the areas surrounded by the contours obtained with each cutoff level. We calculated fractal dimensions from the relationship between the total number of pixels and cutoff levels transformed into logarithms. Fractal dimension for total or regional lung was defined as the severity of emphysema. RESULTS: Total lung fractal dimension (T-FD), upper lung fractal dimension (U-FD), and lower lung fractal dimension (L-FD) for patients with emphysema were 1.84 +/- 0.46 (mean +/-SD), 2.22 +/- 0.61, and 1.77 +/- 0.49, respectively. U-FD was significantly greater than was L-FD. Patients with the ratio of U-FD to L-FD of <1.16 had a significantly greater percentage forced vital capacity (FVC) than did patients with the ratio of >1.16. Patients with an L-FD of <1.8 had a significantly greater forced expiratory volume in 1 s (FEV1)/FVC than did patients with that of >1.8. No significant difference was found between patient groups stratified by U-FD. CONCLUSION: The regional severity of emphysema was well shown by these fractal dimensions.     

不同程度肺气肿MSCT定量测量与视觉评分结果的比较

目的 探讨MSCT肺密度定量测量与视觉评分2种方法对不同程度肺气肿的评估价值.方法 将30例研究对象分成轻度肺气肿组(A组)与中、重度肺气肿组(B组).病人行胸部MSCT容积扫描.测量肺气肿指数(EI),计算视觉评分分数(VS),同时记录2种方法所需时间.对A、B 2组不同医师间所得到结果的差异性与相关性进行比较.对A、B 2组的EI与VS的相关性分别进行比较.对肺密度定量测量和视觉评分所需时间进行比较.结果 医师之间肺密度定量测量结果的一致性好于视觉评分结果的一致性(r=0.99~1.00 vs r=0.35~0.97,P＜0.05).视觉评分结果医师之间的一致性B组好于A组(r=0.73~0.97 vs r=0.35~0.77,P＜0.05),肺密度定量测量结果的一致性A、B 2组之间差异极小(r=0.99~1.00 vs r=0.98~0.99,P＜0.05).B组病人EI与VS的相关性好于A组病人EI与VS的相关性(r=0.725 vs r=0.317,P＜0.05).肺密度定量测量平均时间为(7.88±0.80) min,视觉评分平均时间为(4.42±0.40) min,二者之间差异具有统计学意义(P＜0.05).结论 肺密度定量测量与视觉评分结果之间具有相关性.肺气肿定量测量与视觉评分相比医师之间评估结果的一致性更高.肺气肿视觉评分结果的一致性较差,特别是轻度肺气肿时.对轻度肺气肿病人进行评估与随访时应采用定量测量方法.     

Quantitative and qualitative assessment of left ventricular volume with ECG-gated multislice spiral CT: value of different image reconstruction algorithms in comparison to MRI

PURPOSE: To assess the value of different image reconstruction algorithms for assessment of the left ventricular function using retrospectively ECG-gated multislice spiral computed tomography (MSCT) of the heart. MATERIAL AND METHODS: MSCT and cine magnetic resonance (MR) imaging of the heart were performed in 15 patients. For MSCT, standard and multisegmental image reconstruction with improved temporal resolution were used. Standardized multiplanar reformats in the short axis and long axis views were reconstructed from MSCT data. End-systolic (ESV) and end-diastolic volume (EDV), stroke volume (SV), ejection fraction (EF) and myocardial mass (MM) were calculated. Left ventricular wall motion was assessed qualitatively. RESULTS: MSCT was in acceptable agreement with MR imaging for quantification of the ventricular function. According to the Bland-Altman approach the mean differences for the left ventricular volumes (ESV, EDV, SV) ranged from -9.6 ml to 3.1 ml with standard image reconstruction and from -0.6 ml to 1.9 ml utilizing multisegmental image reconstruction with limits of agreement ranging from -26.6 ml to 12.5 ml and -15.6 ml to 15.0 ml, respectively. Applying the multisegmental image reconstruction algorithm, a significantly improved agreement with the MR data was found for EDV, SV and EF. For wall motion analysis, standard image reconstruction showed a significant difference to MR imaging with a correspondence in 83.75% of the 240 assessed segments, while multisegmental image reconstruction agreed with MR imaging in 92.5% of the segments. CONCLUSION: Multisegmental image reconstruction improves the quantitative assessment of left ventricular function when compared to standard image reconstruction. Multisegmental image reconstruction allows qualitative wall motion analysis.