3D均值中值滤波参数对3D有序子集期望最大化重建图像的影响

目的 采用3D均值中值滤波器对重建前投影数据进行滤波处理，并调整参数定量分析3D均值中值滤波参数选取对有序子集期望最大化（OSEM）重建图像的影响。方法 对分析模拟软件（ASIM）模拟的3D模体投影数据进行3D均值中值滤波处理。利用开源断层图像重建（STIR）软件中的OSEM算法对滤波前后投影数据进行重建，视觉和定量评估重建图像。结果 滤波参数K与图像质量密切相关。K值过大时重建图像边缘保持效果较差，图像过平滑；K值过小则不能抑制噪声，重建图像细节模糊。结论 重建图像噪声大小以及边缘保持效果对滤波参数K十分敏感。根据梯度分布直方图确定滤波参数选取范围，结合梯度分布比从中折中选择适当参数，既可去除噪声，又能保护图像边缘。     

不同强度高级迭代重建算法在不同噪声水平下对图像质量的影响:体模研究

目的 采用Catphan 500体模及改造后的套环体模,探讨2种体模噪声水平下高级迭代重建算法（ADMIRE）不同迭代强度对图像质量的影响。方法 在12种不同扫描条件下对标准体模组和套环体模组分别进行扫描,采用滤波反投影法（FBP ADMIRE 0亚组）及不同迭代强度ADMIRE 1~5（ADMIRE 1~5亚组）重建图像。测量图像的噪声、SNR、空间分辨率、密度分辨率,比较不同迭代强度图像间的差异。结果 标准体模组：随迭代强度增高,噪声逐渐减低,SNR逐渐增高,空间分辨率无明显改变,密度分辨率逐渐升高,ADMIRE 4、5亚组密度分辨率高于ADMIRE 0~2亚组（P均<0.05）。套环体模组：随迭代强度增高,噪声逐渐减低,SNR逐渐增高,ADMIRE 4、5亚组空间分辨率低于ADMIRE 0~2亚组,密度分辨率逐渐升高,ADMIRE 3~5亚组密度分辨率高于ADMIRE 0~2亚组（P均<0.05）。结论 标准体模图像噪声水平下,ADMIRE技术可提高密度分辨率而不降低空间分辨率;套环体模图像噪声水平下,ADMIRE技术可提高密度分辨率,但高级别ADMIRE技术会降低空间分辨率;推荐以ADMIRE 3作为优选迭代强度级别。     

3D均中值滤波参数的选取对3D OSEM重建图像的影响

目的 为了分析3D均值中值滤波参数的选取对OSEM重建图像的影响，采用3D均值中值滤波器对重建前的投影数据进行滤波处理，并调整参数进行定量分析。资料与方法 对分析模拟软件ASIM模拟的三维模体投影数据进行3D 均值中值滤波处理。利用开源断层图像重建软件STIR中的OSEM算法对滤波前后的投影数据进行重建，视觉和定量评估重建图像。结果 滤波参数与图像质量密切相关。值过大，重建图像边缘保持效果较差，图像过平滑。值过小，不能抑制噪声，导致重建图像细节模糊。 结论 重建图像的噪声大小以及边缘保持效果对滤波参数的选取是十分敏感的。可根据梯度分布直方图确定滤波参数选取范围，再结合梯度分布比从该范围内折中选择合适的参数，达到既去除噪声又保护图像边缘的目的。     

Acute gastrointestinal bleeding: Value of MDCT

Contrast-enhanced multidetector row helical computed tomography (MDCT) scanning is establishing itself as a rapid, noninvasive, and accurate diagnostic method in suspected acute gastrointestinal bleeding. Active bleeding can be depicted as an area of focal high attenuation within the bowel lumen on arterial phase MDCT images. New MDCT technologies facilitate three-dimensional image reconstruction, and higher temporal resolution is available with new MDCT scanner generations. This allows for the acquisition of arterial- and portal-venous phase images of the whole abdomen, revealing potential bleeding sources and simultaneously depict morphological changes in the abdomen, such as intestinal tumors. This article gives an overview of available diagnostic modalities in assessing gastrointestinal (GI) tract hemorrhage, with a special emphasis on new MDCT technology.     

Quantitative image analysis for the detection of motion artefacts in coronary artery computed tomography

Multi detector-row CT (MDCT), the current preferred method for coronary artery disease assessment, is still affected by motion artefacts. To rule out motion artefacts, qualitative image analysis is usually performed. Our study aimed to develop a quantitative image analysis for motion artefacts detection as an added value to the qualitative analysis. An anthropomorphic moving heart phantom with adjustable heart-rate was scanned on 64-MDCT and dual-source-CT. A new software technique was developed which detected motion artefacts in the coronaries and also in the myocardium, where motion artefacts are more apparent; with direct association to the qualitative analysis. The new quantitative analysis managed to detect motion artefacts in phantom scans and relate them to artefact-induced vessel stenoses. Quantifying these artefacts at corresponding locations in the myocardium, artefact-induced vessel stenosis findings could be avoided. In conclusion, the quantitative analysis together with the qualitative analysis rules out artefact-induced stenosis.     

Philips GEMINI PET/CT五种常规图像重建算法图像质量的比较

目的 探讨Philips GEMINI PET/CT五种常规图像重建算法对PET图像质量的影响.方法 对Jaszack模型进行PET/CT显像,分别运用滤波反投影Hanning滤波(FBP-Hanning)、滤波反投影Butterworth滤波(FBP-Butterworth)、有序子集最大期望值法(OSEM)、行处理最大拟然算法(RAMLA)及三维行处理最大拟然算法(3D-RAMLA)对模型显像的各组原始数据进行图像重建.比较模型显像在不同重建算法及不同计数状态时图像分辨率、图像均匀性、图像对比度以及重建时间的差异.结果 模型显像中,3D-RAMLA、RAMLA、OSEM、FBP-Hanning及FBP-Butterworth所需重建时间分别为180 s、130 s、120 s、85 s、80 s.在高计数状态下,FBP-Butterworth最小可分辨4.8 mm的"热区"立柱,FBP-Hanning、OSEM、RAMLA及3D-RAMLA最小可分辨6.4 mm的"热区"立柱.在各种重建算法中,3D-RAMLA的图像对比度明显优于其他算法,RAMLA及3D-RAMLA的图像均匀性指标优于其他算法.随着采集计数的减少,各重建算法均出现图像分辨率、图像均匀性以及图像对比度的下降,其中以FBP-Butterworth下降最为显著.结论 不同重建算法及不同计数状态下PET图像质量存在不同程度的差异,在临床显像中应根据需要选择适当的图像重建算法.     

iDose4双模型迭代重建算法对CT图像质量及扫描剂量影响的模体研究

目的：评价双模型迭代重建算法（iDose4）和滤波反投影算法（FBP）对CT图像质量的影响,探讨应用iDose4降低扫描剂量的潜力。方法：应用256层螺旋CT（Philips Brilliance iCT）,在120 kV管电压条件下分别采用200/180/160/140/120/100/80/60/40/20 mAs条件下扫描Catphan模体,采用FBP和iDose4 1-6重建横断图像,以200 mAs FBP重建图像作为参照,分析扫描条件、重建算法对图像质量的影响（CT值、图像噪声、信噪比以及低对比度分辨力）,并分析图像质量与扫描剂量的关系。结果：iDose4与FBP重建图像CT值有高度的一致性（P〉0.05）;iDose4级别1-6重建可以不同程度的降低图像噪声（9.46%-43.30%）;在管电流降低至初始值40%-50%时（80-100 mAs）,iDose4级别6重建图像与200 mAs FBP重建图像其图像噪声无统计学差异（P〉0.05）;管电流降低至初始值50%-60%情况下（100-120 mAs）,其低对比度分辨力基本维持不变。结论：iDose4可以显著降低图像噪声,提高信噪比,改善图像质量。相对于FBP重建图像,利用iDose4高级迭代重建技术可以在扫描剂量隆低至40%-50%情况下,维持图像质量不变。     

儿童副鼻窦结构的64排CT低剂量技术应用

目的探讨儿童副鼻窦结构的64排CT低剂量扫描的最低管电流。方法选取临床怀疑副鼻窦炎而来放射科行CT检查的患儿90例随机分为三组。扫描设备为东芝Aquilion64排螺旋CT机。其他扫描条件固定，每组分别以250mA、20mA、10mA管电流进行扫描。将扫描后重建图像随机教授、副教授及主管技师各一人采用双盲法进行阅片，评价不同扫描剂量对于副鼻窦OMC的显示情况，以取得一致意见为准。以常规剂量图像作为基础片，OMC解剖结构能清楚显示的为合格，不能清楚显示的为不合格。评价结果进行多次配对设计两样本的卡方检验。结果本组实验得到儿童副鼻窦64排CT低剂量扫描管电流的最低值是20mA。结论 儿童副鼻窦64排CT扫描低剂量可以获得符合临床诊断需求的图像信息，因而能应用于临床。     

A Closed-Form Differential Formulation for Ultrasound Spatial Calibration: Multi-wedge Phantom

Calibration is essential in freehand 3-D ultrasound to find the spatial transformation from the image coordinates to the sensor coordinate system. Calibration accuracy has significant impact on image-guided interventions. We introduce a new mathematical framework that uses differential measurements to achieve high calibration accuracy. Accurate measurements of axial differences in ultrasound images of a multi-wedge phantom are used to calculate the calibration matrix with a closed-form solution. The multi-wedge phantom has been designed based on the proposed differential framework and can be mass-produced inexpensively using a 3-D printer. The proposed method enables easy, fast and highly accurate ultrasound calibration, which is essential for most current ultrasound-guided applications and also widens the range of new applications. The precision of the method using only a single image of the phantom is comparable to that of the standard N-wire method using 50 images. The method can also directly take advantage of the fine sampling rate of radiofrequency ultrasound data to achieve very high calibration accuracy. With 100 radiofrequency ultrasound images, the method achieves a point reconstruction error of 0.09 ± 0.39 mm.     

Multidetector computed tomographic morphology of ovaries in cynomolgus macaques (Macaca fascicularis).

Macaques are important models for menopause and associated diseases in women. A sensitive, noninvasive technique for quantifying changes in ovarian morphology would facilitate longitudinal studies focused on the health-related sequelae of naturally occurring or experimentally induced alterations in ovarian structure and function. Multidetector computed tomography (MDCT) is a fast, non-invasive imaging technique that uses X-rays, multiple rows of detectors, and computers to generate detailed slice images of structures. The purpose of this study was to describe the utility of MDCT for reliably characterizing ovarian morphology in macaques. Five macaques were scanned using contrast-enhanced MDCT. The following characteristics were described: 1) appearance of ovaries and adjacent landmarks, 2) effects of varying technical protocols on ovarian image quality, 3) radiation doses delivered to the pelvic region during scanning, and 4) MDCT estimates of ovarian volume and antral follicle counts versus those measured directly in ovarian tissue. Ovaries were distinguishable in all MDCT scans and exhibited heterogeneous contrast enhancement. Antral follicles appeared as focal areas of nonenhancement. Ovarian image quality with 5 pediatric scanning protocols was sufficient for discriminating ovarian margins. Pelvic region radiation doses ranged from 0.5 to 0.7 rad. Antral follicles counted using MDCT ranged from 3 to 5 compared with 3 to 4 counted using histology. Ovarian volumes measured using MDCT ranged from 0.41 to 0.67 ml compared with 0.40 to 0.65 ml by water displacement. MDCT is a promising technique for measuring longitudinal changes in macaque ovarian morphology reliably and noninvasively.     

应用64排螺旋CT低剂量技术检查儿童颞骨结构的探讨

目的探讨儿童颞骨结构的64排CT低剂量扫描的最低管电流。方法选取临床怀疑中耳病变而来放射科行CT检查的患儿180例随机分为3组。扫描设备为东芝Aquilion 64排螺旋CT机。其他扫描条件固定，每组分别以常规剂量组（150mA以上）、30rnA、20mA管电流进行扫描。将扫描后重建图像随机分配至教授、副教授及技师各一人采用双盲法进行阅片，评价不同扫描剂量对于颞骨结构的显示情况，以取得一致意见为准。以常规剂量图像作为基础片，颞骨解剖结构能清楚显示的为合格，不能清楚显示的为不合格。评价结果进行多次配对设计两样本的卡方检验。结果本组实验得到儿童颞骨64排CT低剂量扫描管电流的最低值是30mA。结论儿童颞骨64排低剂量CT扫描可以可获得符合临床诊断需求的图像信息，因而能应用于临床。     

Achieving consistent image quality with dose optimization in 64-row multidetector computed tomography prospective ECG gated coronary calcium scoring

To evaluate the clinical value of a body mass index (BMI) based tube current (mA) selection method for obtaining consistent image quality with dose optimization in MDCT prospective ECG gated coronary calcium scoring. A formula for selecting mA to achieve desired image quality based on patient BMI was established using a control group (A) of 200 MDCT cardiac patients with a standard scan protocol. One hundred patients in Group B were scanned with this BMI-dependent mA for achieving a desired noise level of 18 HU at 2.5 mm slice thickness. The CTDIvol and image noise on the ascending aorta for the two groups were recorded. Two experienced radiologists quantitatively evaluated the image quality using scores of 1–4 with 4 being the highest. The image quality scores had no statistical difference (P = 0.71) at 3.89 ± 0.32, 3.87 ± 0.34, respectively, for groups A and B of similar BMI. The image noise in Group A had linear relationship with BMI. The image noise in Group B using BMI-dependent mA was independent of BMI with average value of 17.9 HU and smaller deviations for the noise values than in Group A (2.0 vs. 2.9 HU). There was a 35% dose reduction with BMI-dependent mA selection method on average with the lowest effective dose being only 0.35 mSv for patient with BMI of 18.3. A quantitative BMI-based mA selection method in MDCT prospective ECG gated coronary calcium scoring has been proposed to obtain a desired and consistent image quality and provide dose optimization across patient population.     

多排螺旋CT对肺动脉及其分支的显示研究

目的探讨多排螺旋CT(MDCT)薄层扫描对肺动脉及其分支的显示能力。方法前瞻性研究30例正常人。CT设备使用GELightspeedQX/iUltra。扫描层厚1.25mm,重建间距0.65mm,扫描速度0.5s/圈,螺距0.875,床速8.75mm/圈。造影剂含碘浓度300mgI/ml,注射速度3.5ml/s,总量80ml,延迟18s后扫描。结果1.25mm薄层重建,肺动脉三、四级、五级及六级分支显示率分别为100%、100%、75%及35%。结论多层螺旋CT薄层扫描可以较好地显示第三～五级肺动脉。     

64排CT容积HRCT扫描方案优化的模具研究

目的优化容积HRCT的扫描方案,提高容积HRCT的图像质量。方法应用64排CT对Catphan模具进行扫描,采用螺旋扫描方式,对HRCT的扫描方案进行优化,优化的参数包括：探测器宽度、焦点尺寸、旋转时间、管电压及管电流、扫描孔径、螺距、重建卷积函数、重建模式。结果增加探测器宽度可使噪声降低（t=-4.228,P=0.002）,放射剂量降低,对空间分辨率无明显影响。改变旋转时间对空间分辨率、噪声（F=0.627,P=0.130）均无明显差异。小焦点较大焦点的空间分辨率提高1 LP/cm。增加管电压与管电流可使噪声降低,空间分辨率随之改善,放射剂量增加。不同扫描孔径的放射剂量有所不同。螺距0.5得到最佳的Z轴分辨率12 LP/cm。在3种高分辨率算法中,bone优于bone plus及edge。重建模式plus较full的噪声降低（t=58.234,P〈0.001）,Z轴分辨率也降低。结论采用优化的扫描方案,可以提高容积HRCT的图像质量并控制放射剂量,有助于正确评价容积HRCT的价值。     

Stereolithographic reproduction of complex cardiac morphology based on high spatial resolution imaging

Sammary Background Precise knowledge of cardiac anatomy is mandatory for diagnosis and treatment of congenital heart disease. Modern imaging techniques allow high resolution three-dimensional (3D) imaging of the heart and great vessels. In this study stereolithography was evaluated for 3D reconstructions of multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) data. Methods A plastinated heart specimen was scanned with MDCT and after segmentation a stereolithographic (STL) model was produced with laser sinter technique. After scanning the STL model with MDCT these data were compared with those of the original specimen after rigid registration using the iterative closest points algorithm (ICP). The two surfaces of the original specimen and STL model were matched and the symmetric mean distance was calculated. Additionally, the heart and great vessels of patients (age range 41 days–21 years) with congenital heart anomalies were imaged with MDCT (n = 2) or free breathing steady, state free-precession MRI (n = 3). STL models were produced from these datasets and the cardiac segments were analyzed by two independent observers. Results All cardiac structures of the heart specimen were reconstructed as a STL model within sub-millimeter resolution (mean surface distance 0.27 ± 0.76 mm). Cardiac segments of the STL patient models were correctly analyzed by two independent observers compared to the original 3D datasets, echocardiography (n = 5), x-ray angiography (n = 5), and surgery (n = 4). Conclusions High resolution MDCT or MRI 3D datasets can be accurately reconstructed using laser sinter technique. Teaching, research and preoperative planning may be facilitated in the future using this technique. Electronic Supplementary Material Electronic supplementary material is available if you access the Local HTML full text version of the article at     

Ultrasonic speed of sound dispersion imaging

The feasibility for speed of sound dispersion (SOSD) imaging was investigated here. A through transmission new method for measuring the SOSD was utilized. With this method a long pulse comprising of two frequencies one being the double of the other is transmitted through the object and detected on its other side. SOSD projection images were obtained by scanning objects immersed in water using a raster mode utilizing a computerized scanning system. Using this approach SOSD projection images were obtained for solids and fluids as well as for a tissue mimicking breast phantom and an in vitro soft tissues phantom. The results obtained here, have clearly demonstrated the feasibility of SOSD projection imaging. SOSD may serve as a new contrast source and potentially may aid in breast diagnosis.     

Reduced exposure using asymmetric cone beam processing for wide area detector cardiac CT

The purpose of this study was to estimate dose reduction after implementation of asymmetrical cone beam processing using exposure differences measured in a water phantom and a small cohort of clinical coronary CTA patients. Two separate 320?×?0.5?mm detector row scans of a water phantom used identical cardiac acquisition parameters before and after software modifications from symmetric to asymmetric cone beam acquisition and processing. Exposure was measured at the phantom surface with Optically Stimulated Luminescence (OSL) dosimeters at 12 equally spaced angular locations. Mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at the center plus four peripheral locations in the water phantom. To assess image quality, mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at five points within the water phantom. Retrospective evaluation of 64 patients (37 symmetric; 27 asymmetric acquisition) included clinical data, scanning parameters, quantitative plus qualitative image assessment, and estimated radiation dose. In the water phantom, the asymmetric cone beam processing reduces exposure by approximately 20% with no change in image quality. The clinical coronary CTA patient groups had comparable demographics. The estimated dose reduction after implementation of the asymmetric approach was roughly 24% with no significant difference between the symmetric and asymmetric approach with respect to objective measures of image quality or subjective assessment using a four point scale. When compared to a symmetric approach, the decreased exposure, subsequent lower patient radiation dose, and similar image quality from asymmetric cone beam processing supports its routine clinical use.     

Multidetector row CT: principles and clinical applications

Multidetector row CT (MDCT) is the latest advancement in CT technology. The use of multiple detector rows allows faster scanning and thinner collimation. These improvements allow routine scans to be performed faster with higher z-axis resolution. New applications can also be developed using this new technology. To fully appreciate the potential of these new MDCT scanners, it is important for the radiologist to be familiar with the scanner design and capabilities. This article reviews the basic principles of MDCT scanners. Scanner/detector design, beam collimation/slice thickness, radiation dose, data manipulation, and display are discussed.     

SAFIRE重建算法对胸部CT图像质量和辐射剂量的影响

目的 利用仿真胸部体模,比较原始数据域迭代重建(SAFIRE)算法与滤波反投影(FBP)算法对胸部CT图像质量和辐射剂量的影响。方法 在新双源CT(Somatom definition flash CT)设备上预设80、100、120 kV三组管电压值,采用自动毫安秒care dose 4D技术对仿真胸部体模进行扫描,分别用FBP及SAFIRE重建算法(等级1~5)重建图像,比较胸部不同组织结构的噪声及CT值,并由2名放射科医师独立评价图像质量。每组扫描结束后,记录CT剂量加权指数(CTDIvol)和剂量长度乘积(DLP),计算并比较有效剂量。结果 相同扫描参数检查时,SAFIRE重建算法较FBP算法图像噪声明显降低(P<0.05);不同扫描参数检查时,无论FBP算法或SAFIRE重建算法,图像噪声均随管电压增加而降低;胸部各组织结构的噪声会随重建算法和管电压改变而发生变化;100 kV/SAFIRE(等级3)的主观和客观图像质量指标均优于120 kV/FBP,且辐射剂量降低37.61%。结论 胸部CT扫描中,采用SAFIRE重建算法能有效提高图像质量,降低辐射剂量。