Semi-automatic measurement of the airway dimension by computed tomography using the full-width-half-maximum method: a study on the measurement accuracy according to the CT parameters and size of the airway.

OBJECTIVE: To assess the influence of variable factors such as the size of the airway and the CT imaging parameters such as the reconstruction kernel, field-of-view (FOV), and slice thickness on the automatic measurement of airway dimension. MATERIALS AND METHODS: An airway phantom was fabricated that contained eleven poly-acryl tubes of various lumen diameters and wall thicknesses. The measured density of the poly-acryl wall was 150 HU, and the measured density of the airspace filled with polyurethane foam was -900 HU. CT images were obtained using a 16-MDCT (multidetector CT) scanner and were reconstructed with various reconstruction kernels, thicknesses and FOV. The luminal radius and wall thickness were measured using in-house software based on the full-width-half-maximum method. The measured values as determined by CT and the actual dimensions of the tubes were compared. RESULTS: Measurements were most accurate on images reconstructed with use of a standard kernel (mean error: -0.03 +/- 0.21 mm for wall thickness and -0.12 +/- 0.11 mm for the luminal radius). There was no significant difference in accuracy among images with the use of variable slice thicknesses or a variable FOV. Below a 1-mm threshold, the measurement failed to represent the change of the real dimensions. CONCLUSION: Measurement accuracy was strongly influenced by the specific reconstruction kernel utilized. For accurate measurement, standardization of the imaging protocol and selection of the appropriate anatomic level are essential.     

螺旋CT眼眶容积测量方法的研究

目的 探讨测量眼眶容积简便、省时又相对准确的CT成像方法 . 资料与方法 以鼻科疾患就诊行16层螺旋CT扫描20例患者,眼眶正常,眼眶区及其周围未见占位性病变.双侧眼眶分别行容积再现(VR)成像,测得容积归入VR组;以层厚/层间距为2 mm/2 mm、2 mm/4 mm、2 mm/5 mm、3 mm/3 mm、3 mm/5 mm横断位重建五组图像,其余各种参数保持一致,并分别命名为A组、B组、C组、D组及E组.对各组测量得到的眼眶容积进行统计学分析. 结果 所得各组数据左右侧差异均无统计学意义.以VR组数据作为参照标准,A组误差率及差别的范围均最小,为2.42%和0.42%～4.40%,E组与其之间的差别最大,为7.35%,D组与其之间差别的范围最大为0.35%～7.75%. 结论 A组层厚及层间距均为2 mm重建图像测量眼眶容积省时、方便、准确,可应用于各类型CT扫描仪.     

螺旋CT多平面重组在副鼻窦检查中的应用

目的 :利用螺旋CT多平面重组技术探讨副鼻窦轴位扫描能否代替直接冠状位扫描。方法 :对 15例能合作的患者 ,均行副鼻窦轴位及冠状位扫描。使用美国GEProspeedFII双排螺旋CT机 ,层厚 5mm ,螺距 0 .75 ,连续横轴位扫描 ,利用多平面重组 (MPR)技术得到冠状位、矢状位重组图像 ;直接冠状位扫描获取冠状位图像 ;将同一患者的两组不同冠状位图像比较 ,主要观察各鼻窦窦壁及窦口。结果 :轴位扫描后重组所获图像亦能从多方位多角度观察 ,清楚显示各鼻窦及窦口。结论 :重组冠状位图像与直接冠状位扫描图像效果相同 ,可以取代直接冠状位扫描。避免后者检查时头部后仰造成的不适 ,患者容易接受 ,值得推广。     

Spiral CT optimization for measurement of bronchial lumen diameter using an experimental model

The aim of the study was to determine optimal parameters for demonstrating sublobar bronchi on spiral CT. Measurements were obtained from five parallel polyethylene tubes embedded in foam matrix with similar radiographic characteristics to segmental and subsegmental bronchi and to lung parenchyma, respectively. Collimation widths of 1.5, 2, 3 and 4 mm were used, with a pitch of 1 or 1.5 and a reconstruction interval of 1 mm or 2 mm. Various slice planes were used. Images acquired orthogonally were viewed normally. Images acquired in planes oblique or parallel to the long axes of the tubes were reformatted into a plane orthogonal to the long axes of the tubes to be comparable with the directly acquired orthogonal images. Tube diameters were measured at lung window settings (L, -400; W, 1300) and compared with known true inner and outer tube diameters. Measurements from images acquired orthogonal to the tube long axes were accurate regardless of slice thickness. Images acquired obliquely or parallel only produced accurate measurements at the lowest slice thickness (1.5 mm). Pitch and reconstruction interval had no effect on measurement error in any scan plane. It is concluded that a slice thickness of 1.5 mm or less, with a pitch of 1.5, should be used when acquiring images at angles other than orthogonal to the long axes of experimental tubes equivalent to the segmental and subsegmental bronchi. It is suggested that similar parameters should be used in vivo and that the examination should be targeted to the area of the bronchial tree in question to reduce patient dose and length of breath-hold.     

离体猪肺的气管、支气管树遮盖表面显示法三维重建

目的：探讨CT扫描层厚和间隔对三维重建的影响。材料和方法：研究对象为10具离体新鲜猪肺标本。每一对象均接受层厚／间隔分别为3mm/3mm、3mm/1.5mm和1.5mm/1.5mm三种组合的EBCT扫描。扫描条件：130kV/630mA。扫描方式：连续容积扫描（CVS）。其横断面图像转入Insight工作站（accuimnage diagnostic corporation,USA)进行三维重建,重建方式为遮盖表面显示法（SSD）。重建值为－500Hu--300Hu。结果：（1）新鲜离体猪肺标本气管和支气管的一、二级分支的三维测量与解剖测量相符合。（2）3mm/3mm、1.5mm/1.5mm和3mm/1.5mm三组扫描参的猪肺气管、支气管一级分支的三维重建评分结果间无显著差异;对于二级支气管分支（3.67mm左右管径）的三维重建,3mm/1.5mm组的评分高于1.5mm/1.5mm组,有统计学意义;1.5mm/1.5mm组高于3mm/3mm组,也有统计学意义。结论：降低层厚或重叠扫描进行的三维重建可更好地显示较细的支气管,对于较粗的支气 管其影响不明显。     

螺旋CT三维重建技术在上气道病变中的临床价值

目的　探讨螺旋CT三维(3D)重建技术在上气道病变中的临床应用价值。　方法　对36例上气道病变的患者进行轴位螺旋CT扫描,层厚3.0mm,螺距1.0～1.2,分别做气道表面遮盖法(SSD)、表面透视法(RaySum)重建和叠加成像。　结果　SSD图像能清楚显示上气道的正常形态、多方位观察可全景地反映气道表面受压的情况,RaySum能更好地显示狭窄内缘的情况,9例(25%)气道SSD显示正常;SSD图像上显示的肿瘤侵犯范围明显小于轴位和多平面重组(MPR)图像。叠加成像清楚显示肿瘤与邻近结构尤其是血管、气道的关系。　结论　3D重建能立体地显示上气道病变,是轴位和MPR图像的很好补充手段。     

Computer-assisted lung nodule volumetry from multi-detector row CT: influence of image reconstruction parameters

PURPOSE: To investigate differences in volumetric measurement of pulmonary nodules caused by changing the reconstruction parameters for multi-detector row CT. MATERIALS AND METHODS: Thirty-nine pulmonary nodules less than 2 cm in diameter were examined by multi-slice CT. All nodules were solid, and located in the peripheral part of the lungs. The resultant 48 parameters images were reconstructed by changing slice thickness (1.25, 2.5, 3.75, or 5 mm), field of view (FOV: 10, 20, or 30 cm), algorithm (high-spatial frequency algorithm or low-spatial frequency algorithm) and reconstruction interval (reconstruction with 50% overlapping of the reconstructed slices or non-overlapping reconstruction). Volumetric measurements were calculated using commercially available software. The differences between nodule volumes were analyzed by the Kruskal-Wallis test and the Wilcoxon Signed-Ranks test. RESULTS: The diameter of the nodules was 8.7+/-2.7 mm on average, ranging from 4.3 to 16.4mm. Pulmonary nodule volume did not change significantly with changes in slice thickness or FOV (p>0.05), but was significantly larger with the high-spatial frequency algorithm than the low-spatial frequency algorithm (p<0.05), except for one reconstruction parameter. The volumes determined by non-overlapping reconstruction were significantly larger than those of overlapping reconstruction (p<0.05), except for a 1.25 mm thickness with 10 cm FOV with the high-spatial frequency algorithm, and 5mm thickness. The maximum difference in measured volume was 16% on average between the 1.25 mm slice thickness/10 cm FOV/high-spatial frequency algorithm parameters and overlapping reconstruction. CONCLUSION: Volumetric measurements of pulmonary nodules differ with changes in the reconstruction parameters, with a tendency toward larger volumes in high-spatial frequency algorithm and non-overlapping reconstruction compared to the low-spatial frequency algorithm and overlapping reconstruction.     

Optimization of computed tomography technique to demonstrate the fine structure of the lung

The purpose of this investigation was to optimize the reconstruction algorithm and the slice thickness of computed tomography (CT) for the study of the fine structure of the lung. In 75 patients, we performed routine thoracic CT examination and obtained two high-resolution CT (HRCT) slices at the same level using the standard and bone algorithms, or using the slice thickness of 1.5 mm and 3.0 mm. Side-by-side comparison of the standard and bone images revealed that more branching of the small vessels and more small bronchi could be recognized on the bone image than on the standard image. Thickened bronchovascular bundles and interlobular septa were demonstrated more clearly on the bone image than on the standard image. There was no significant difference in the CT attenuation value between the standard and bone images. The difference between 1.5 mm and 3.0 mm images when demonstrating the small vessels and bronchi was minimal in such lesions as lymphangitis carcinomatosa and radiation fibrosis. Thus HRCT, with a slice thickness of 1.5 mm and 3.0 mm reconstructed by the bone algorithm, is suitable for the demonstration of the fine structure of the lung.     

Accuracy of automatic airway morphometry in computed tomography-correlation of radiological-pathological findings

Objectives

Airway morphology shows characteristic changes in different pathologies. This study assesses the accuracy of a current automatic airway assessment technique by correlating CT images of porcine airways to histological slices of the same localization.

Materials and methods

Four isolated and ventilated porcine lungs were frozen in a liquid nitrogen bath and examined with a CT scanner (MDCT). This technique both preserved normal radiomorphological appearance and made it possible to slice the specimens for histological examination for subsequent correlation. The parameters wall thickness (WT), wall percentage (WP), and total diameter (TD) were assessed by computer-aided measurement of the MDCT images using an integral-based method (IBM) and by manually measuring the histological slices with an electronic caliper.

Results

The radiological–pathological correlation could be performed for 16 localizations. Mean relative errors for WT, WP, and TD were 11%, 5.6%, and 8.5%, respectively. Correlation was very high with coefficients r of 0.951 for WT, 0.916 for WP, and 0.987 for TD.

Conclusions

Our results are comparable to previously described errors in phantom correlations but are the first proof of ex vivo feasibility. Thus, by applying this freezing technique to MDCT data of diseased, explanted lungs and by combination with the IBM, further experiments can be performed to explore the effects of airway pathology on radiological morphology.     

术前CT测量胸腰椎椎弓根相关参数在螺钉内固定术中的应用

目的探讨术前CT测量胸腰椎椎弓根相关参数在椎弓根螺钉内固定术中的应用价值。方法 63例胸腰椎椎弓根损伤患者于螺钉内固定术前均行拟固定椎体节段的椎弓根层面薄层CT扫描,图像传输至PACS医生诊断工作站,选择椎弓根最宽层面测量以下参数:椎弓根水平面角(PHA),椎弓根轴心线长度(PAL),钉道长度(LSC),椎弓根内横径(PTD)。结果 T1～12及L1～5椎弓根水平面角逐渐增大;T1～10及L1～4椎弓根轴心线长度逐渐增长,T111、2较T10短,L5较L4短,S1较L5短;T1～6椎弓根内横径逐渐变小,T7～12椎弓根内横径逐渐增大。胸腰段椎弓根水平面角、内横径及轴心线长度在不同个体及不同节段存在差异性。根据椎弓根水平面角,确定进钉的方向,根据椎弓根内横径,选择螺钉的最大直径,根据椎弓根轴心线长度,确定螺钉的总长度和螺钉植入深度。根据CT测量椎弓根相关数据进行个性化置钉,术后CT扫描证实螺钉全部准确置入椎弓根内。结论通过术前CT测量不同节段胸腰椎椎弓根相关数据,制定个性化的置钉方案,可提高置钉准确率及减少并发症。     

MSCT胸部低剂量扫描对慢性肺部病变的应用研究

目的:比较低剂量及常规剂量扫描对慢性肺部弥漫性病变(范围较广泛者)的显示差异,探讨低剂量扫描诊 断慢性弥漫性或浸润性肺部病变的可行性及合理扫描方案。方法:34例慢性肺部病变患者及4例临床怀疑支气管扩张但 CT扫描未见异常的患者,行低剂量(50mAs)全肺螺旋扫描,14例患者并行常规剂量(195mAs)全肺增强扫描,所有病例 在病变部位加低剂量(50mAs)及常规剂量(220mAs)薄层(2.5mm)HRCT扫描。比较低剂量及常规剂量扫描对病变范 围、分布及病变特征的显示差异。结果:两种剂量全肺扫描(重建层厚7.5mm)图像对肺部病变分布的范围及各种征象的 显示差异无显著性意义(P>0.05);两种剂量的薄层HRCT图像对各种病变征象均可以显示,但是对支气管扩张、蜂窝样 改变、纤维索条及胸膜下线的显示以常规剂量为优(P<0.05),对其它征象的显示两组剂量差异无显著性意义(P> 0.05)。结论:对于怀疑肺弥漫性病变的患者,可以采用低剂量全肺扫描,病变部位加常规剂量薄层HRCT扫描。     

Serial change in airway lumen and wall thickness at thin-section CT in asymptomatic subjects

PURPOSE: To retrospectively analyze serial changes in airway lumen and wall thickness (WT) at multi-detector row computed tomography (CT) in asymptomatic subjects. MATERIALS AND METHODS: Institutional review board did not require its approval or informed patient consent. Airway dimensions were analyzed in 52 patients (30 men and 22 women) without known cardiopulmonary disease. Contiguous 2-mm CT sections were obtained after reconstruction, extending from origin of right posterior basal segmental bronchi to posterior subsegmental bronchi. Following parameters were determined with semiautomatic image-processing program: luminal area (LA), total airway area (TA), short axis of lumen (LSD), and short axis of total airway (TSD). In airways in which adjacent vessel or branching of small bronchus abutted boundary of airway, extrapolated line was traced by one radiologist. Airway wall area (WA) was calculated as TA - LA, and WT was calculated as (TSD - LSD)/2. Relative WA (WA% = [WA/TA] . 100) and ratio of airway WT to total diameter (D) (WT/D = WT/TSD) were calculated. Linear regression analysis and Spearman rank correlation were used to evaluate relationship between airway parameters (LA, WA%, and WT/D ratio) and distance from origin of segmental bronchi. RESULTS: LA decreased as CT proceeded from hilum to periphery (r = -0.765, P < .001). In 308 (32.7%) of 943 bronchi, however, LA increased as CT proceeded from hilum to periphery. LA increased by 10% or more in 101 (10.7%) of 943 bronchi. Mean changes in WA% and WT/D ratio between two contiguous sections were 0.66 +/- 5.05 (standard deviation) and 0.003 +/- 0.024, respectively. WA% changed by more than 5% between two contiguous sections in 274 (29.0%) of 943 bronchi. WT/D ratio changed by more than 0.02 between two contiguous sections in 338 (35.8%) of 943 bronchi. CONCLUSION: Variation of airway lumen and WT is found in asymptomatic subjects without known cardiopulmonary disease.     

MDCT assessment of airway wall thickness in COPD patients using a new method: correlations with pulmonary function tests

Quantitative assessment of airway-wall dimensions by computed tomography (CT) has proven to be a marker of airway-wall remodelling in chronic obstructive pulmonary disease (COPD) patients. The objective was to correlate the wall thickness of large and small airways with functional parameters of airflow obstruction in COPD patients on multi-detector (MD) CT images using a new quantification procedure from a three-dimensional (3D) approach of the bronchial tree. In 31 patients (smokers/COPD, non-smokers/controls), we quantitatively assessed contiguous MDCT cross-sections reconstructed orthogonally along the airway axis, taking the point-spread function into account to circumvent over-estimation. Wall thickness and wall percentage were measured and the per-patient mean/median correlated with FEV1 and FEV1%. A median of 619 orthogonal airway locations was assessed per patient. Mean wall percentage/mean wall thickness/median wall thickness in non-smokers (29.6%/0.69 mm/0.37 mm) was significantly different from the COPD group (38.9%/0.83 mm/0.54 mm). Correlation coefficients (r) between FEV1 or FEV1% predicted and intra-individual means of the wall percentage were −0.569 and −0.560, respectively, with p < 0.001. Depending on the parameter, they were increased for airways of 4 mm and smaller in total diameter, being −0.621 (FEV1) and −0.537 (FEV1%) with p < 0.002. The wall thickness was significantly higher in smokers than in non-smokers. In COPD patients, the wall thickness measured as a mean for a given patient correlated with the values of FEV1 and FEV1% predicted. Correlation with FEV1 was higher when only small airways were considered     

气管支气管病变的多层螺旋CT诊断

目的:回顾性分析41例气管支气管病变的多层螺旋CT(MDCT)影像资料,探讨MDCT对气管支气管病变的诊断价值。材料和方法:搜集自2006年5至2007年8月共41例气管支气管病变的MDCT资料,常规横断面为6mm层厚,回顾性重建为1mm层厚、1mm层间隔,并于同步工作站进行三维重建,包括CT仿真支气管内镜(CTVE)、多层面/曲面成像(MPP/CPR)、最大/小密度投影(MIP,MinIP)、表面遮盖成像(SSD))和容积重组(VR)。结果:MDCT结合多种三维重建可以很好地显示气管支气管的正常和异常,肺癌、支气管结核、支气管腔内占位以及邻近病变所致气道狭窄各有特点。三维重建对狭窄部位、范围和程度的确定显示很好。结论:MDCT结合多种后处理三维重建对气管支气管的各种类型病变有较好的诊断和鉴别诊断价值。     

气管、支气管黏液表皮样癌的多层螺旋CT表现

目的 分析原发于气管、支气管的黏液表皮样癌（MEC）的CT表现以提高对该病的认识水平。资料与方法 回顾性分析4例经手术病理证实的气管、支气管MEC临床资料和CT表现。所有病例行层厚为3mm胸部螺旋CT扫描,其中平扫3例,增强扫描2例。对所有病例进行多平面重建（MPR）、三维（3D）和仿真内镜（CTVE）重建后进一步观察。结果 1例气管MEC表现为受累气管壁局部增厚,肿瘤轻度强化。3例左主支气管MEC表现为主支气管腔内息肉样结节,并沿支气管方向生长,平扫肿瘤稍低于或等于肌肉密度,密度均匀;1例增强扫描显示肿瘤明显强化,1例见钙化;3例均有气道阻塞性改变,1例纵隔淋巴结肿大。结论 气管、支气管MEC的CT表现有一定特征性。多层螺旋CT的各重建图像能更完整、清晰地显示肿瘤,对临床治疗有重要提示意义。     

Fractal analysis of trabecular architecture: with special reference to slice thickness and pixel size of the image

Many analyses of bone microarchitecture using three-dimensional images of micro CT (microCT) have been reported recently. However, as extirpated bone is the subject of measurement on microCT, various kinds of information are not available clinically. Our aim is to evaluate usefulness of fractal dimension as an index of bone strength different from bone mineral density in in-vivo, to which microCT could not be applied. In this fundamental study, the relation between pixel size and the slice thickness of images was examined when fractal analysis was applied to clinical images. We examined 40 lumbar spine specimens extirpated from 16 male cadavers (30-88 years; mean age, 60.8 years). Three-dimensional images of the trabeculae of 150 slices were obtained by a microCT system under the following conditions: matrix size, 512 x 512; slice thickness, 23.2 em; and pixel size, 18.6 em. Based on images of 150 slices, images of four different matrix sizes and nine different slice thicknesses were made using public domain software (NIH Image). The threshold value for image binarization, and the relation between pixel size and the slice thickness of an image used for two-dimensional and three-dimensional fractal analyses were studied. In addition, the box counting method was used for fractal analysis. One hundred forty-five in box counting was most suitable as the threshold value for image binarization on the 256 gray levels. The correlation coefficients between two-dimensional fractal dimensions of processed images and three-dimensional fractal dimensions of original images were more than 0.9 for pixel sizes < or =148.8 microm at a slice thickness of 1 mm, and < or =74.4 microm at one of 2 mm. In terms of the relation between the three-dimensional fractal dimension of processed images and three-dimensional fractal dimension of original images, when pixel size was less than 74.4 microm, a correlation coefficient of more than 0.9 was obtained even for the maximal slice thickness (1.74 mm) examined in this study.     

CT angiography of the coronary arteries with a 16-row spiral tomograph. Effect of spatial resolution on image quality

PURPOSE: To evaluate image quality of coronary CT angiography with retrospectively ECG-gated 16 multi-slice spiral CT (MSCT), reconstructed with 0.75 mm slice thickness for optimal spatial resolution and with 1.3 mm slice thickness, to produce spatial resolution comparable to a 4-MSCT. MATERIALS AND METHODS: Ten patients underwent coronary CT angiography with a 16-MSCT (Siemens Sensation 16, Forchheim, Germany) with 0.75 mm detector collimation. Raw helical CT data were retrospectively reconstructed using two different settings. Setting A: B20f smooth kernel, axial MPR with 1.3 mm slice thickness and 0.7 mm increment. Setting B: B35f "HeartView" medium-smooth kernel, 0.75 mm slice thickness, 0.5 mm increment. In the axial slices two regions of interest (ROIs) were placed in the area of the aortic root (AR) and more caudal in the area of the left ventricle (LV). Image noise was determined by the standard deviation of the CT numbers.Two readers determined visibility of coronary arteries by standardized maximum intensity projections (MIP) post-processing in left, right anterior and left anterior oblique projection plane from setting A and B. Each projection was rated on a five point rating scale concerning plaque delineation. Points determined for each data set were summed up and used for comparison. RESULTS: No significant difference between the CT-numbers was found for setting A and B (A: 283.0 in AR/295.9 in LV and B: 282,9 in AR/297.2 in LV; p >0.2). However, the image noise was significantly different for setting A and B (A: 4.46 in AR/1.67 in LV and B: 8.16 in AR/7.38 in LV; p <0.01). Better delineation of the coronary arteries and atherosclerotic lesions could be achieved from MIP projections in setting B compared to setting A. CONCLUSION: Higher image noise is present in coronary 16-MSCT with thin-slice reconstruction compared to simulated 4-MSCT. However the MIP-reconstructions benefit most from the higher spatial resolution.     

Dynamic upper airway soft-tissue and caliber changes in healthy subjects and snoring patients

BACKGROUND AND PURPOSE: The oropharyngeal airways are smaller in those who snore than in those who do not. We sought to determine which soft-tissue component surrounding the airways contributes to upper airway narrowing in those who snore. METHODS: Ten control subjects and 19 snoring patients underwent CT, with 2-mm-thick axial sections obtained every 0.6 seconds during the respiration cycle at the same oropharyngeal level. We selected two sections with the widest and narrowest parts of the oropharyngeal airway to measure the anteroposterior and lateral dimensions of the airway and the thickness of the bilateral parapharyngeal fat pads, pterygoid muscles, and parapharyngeal walls. Mean values were calculated for each phase. For each subject, differences were calculated by subtracting the values in narrowest phase from those in the widest phase. RESULTS: Changes in airway dimension (P < .05) and lateral parapharyngeal wall thickness (P < .01) were significantly different between snorers and control subjects. Changes in parapharyngeal wall thickness and transverse oropharyngeal airway diameter changes were significantly related (P < .01) in those who snored but not in control subjects. CONCLUSION: Airway narrowing predominantly occurs in the lateral dimension in people who snore. Changes in the lateral pharyngeal wall are more important than the parapharyngeal fat pads in airway calibration. Narrowing of the upper airway area at the end of the expirium and the beginning of the inspirium is thought to be the cause of snoring and due to augmented muscle mass and prolonged laxity rather than inadequate activation of the pharyngeal dilating muscles.     

双源CT脑静脉造影扫描技术探讨

目的:选择脑双源CT静脉造影(CTV)的最佳扫描时相及重建层厚,以获得良好的脑静脉图像。方法:①11例志愿者行同层动态增强扫描,以探讨团注追踪触发技术的理论阈值。以理论阈值为中心,将45例志愿者随机分为3组探讨团注追踪触发技术的应用阈值。②将扫描所获得原始数据以0.75mm和1.50mm层厚重建,比较2组层厚重建的三维血管图像质量,进行统计分析。结果:触发阈值100HU组,靶血管全程显示良好;采用0.75mm层厚重建的三维血管图像质量优于1.50mm层厚(P<0.05)。结论:采用100HU阈值进行静脉触发扫描和0.75mm层厚重建血管可以获得良好的脑CTV图像。     

Portal venous calcifications 20 years after portosystemic shunting: demonstration by spiral CT with CT angiography and 3D reconstructions

BACKGROUND: Evaluation of the value of spiral computed tomography (SCT), and postprocessing procedures in patients with extensive portal venous calcifications 20 years after portosystemic shunting was performed. METHODS: In two patients spiral CT (SCT) examinations of the abdomen (slice thickness 3 mm, table feed 6 mm/s) were performed prior and after application of 150 ml of contrast material administered at a flow rate of 4 ml/s. Axial images were reconstructed at 2 mm increments for postprocessing procedures and 6 mm increments for axial source images. Postprocessing was performed with a maximum intensity projection (MIP) and shaded surface display (SSD) imaging program. RESULTS: In both cases preoperative plain film radiography of the chest and abdomen showed large curvilinear calcifications located at the upper quadrant of the abdomen. The calcifications were directed along the expected axis and position of the portal vein and the portosystemic venous anastomosis. Axial CT slices and CTA showed that the calcifications were located in the vessel wall and that the portal vein lumen as well as the portosystemic venous anastomosis were patent. CONCLUSION: Long-standing portal hypertension is capable of causing portal venous calcifications due to mechanical stress to the vessel wall even years after performing portosystemic shunting. Typically, the calcifications are directed along the expected axis and position of the portal vein. SCT of the portal venous system is a reliable method to differentiate between calcifications in a thrombus or in the vessel wall, which may have therapeutic significance.