容积重建(VR)法的技术参数及应用

目的：探讨螺旋ＣＴ三维容积重建（ｖｏｌｕｍｅ ｒｅｎｄｅｒｉｎｇ,简称ＶＲ）的实用方法和技巧,扩大其临床应用范围,方法：ＶＲ三维重建１００例包括：①血管组４９例,②骨关节组３０例,③其它部位组２１例。扫描层厚为１ｍｍ、２ｍｍ、３ｍｍ、５ｍｍ,重建间隙０．９ｍｍ、１．４ｍｍ、２．３ｍｍ,螺距１～２,重建方式为容积重建。结果：全部病例三维立体显示良好。图像柔和自然,病变整体形态及周围结构的关系明确,并     

螺旋CT三维重建的方法及技巧

目的 探讨螺旋ＣＴ三维重建的实用方法和技巧。方法 选择成功地进行了三维重建的２００例骨和血管病变。扫描层厚３￣５ｍｍ,重建间隔２￣３ｍｍ,螺距０．５￣１,数据输入工作站,用遮盖表现显示法进行处理。结果 全部病例的三维立体显示良好,病变整体形态、与周围结构的关系从不同位置和角度得以观察。结论 高质量的三维图像依赖于技术参数的合理选择匹配,以及医技人员的操作技巧和熟练程度以及扫描机器的质量。     

螺旋CT对塑料球并突起模型的成像观察

目的比较螺旋ＣＴ（ＳＣＴ）不同层厚及床速对塑料球及突起模型成像的还原准确性及多平面成像（ＭＰＲ）的影响。材料与方法自制塑料球（直径１５ｍｍ）上置２４根突起（长１、３、５ｍｍ，直径２ｍｍ），长短相间排列，并在其旁置不同走行方向的１ｍｍ和２．７ｍｍ导管若干根，模拟结节旁肺血管。层厚（ｍｍ）、每秒进床速度（ｍｍ／ｓ）、重建间隔（ｍｍ）分别以１０、１０、１ｍｍ，１０、１０、１ｍｍ，５、５、１ｍｍ，３、６、１ｍｍ，２、２、１ｍｍ，和高分辨率ＣＴ（ＨＲＣＴ）扫描，比较横断面及ＭＰＲ图像质量。结果各组扫描横断成像均能显示突起存在和数目，只是≤３、３、１ｍｍ时显示突起的位置和方向性及清晰度更优。床速≥５ｍｍ／ｓ时ＭＰＲ的球及突起明显拉长、模糊，不宜评价。螺距为０．５时采用１８０内插法（ｓｌｉｍ）对于提高ＭＰＲ质量是必要的。床速≥１０ｍｍ／ｓ时，横断面图像上紧邻突起、球或相互交叉的斜行导管可能被误解为有侵蚀。结论若要ＭＰＲ评价球灶、突起及周围导管更为精确，ＳＣＴ扫描参数应≤３、６、１ｍｍ，螺距＜１时重建内插算法务必采用１８０°内插算法。进床速为１０～２０ｍｍ／ｓ的ＳＣＴ可作为筛选病灶及初步定性的方法。     

正常听骨链的HRCT研究

目的：探讨ＨＲＣＴ显示听骨链的扫描技术。材料和方法：１５８个（８５例）正常耳按不同的扫描基线、层厚、层隔分为Ａ、Ｂ、Ｃ三组，计算三组中听骨链各部位的显示率。结果：砧骨长脚、镫骨上结构和砧镫关节的显示率在Ａ组分别为９０．９％、８５．２％和８４．１％，高于Ｂ组和Ｃ组，三组相比较有统计学意义（Ｐ＜０．０５）。结论：利用ＨＲＣＴ采用平行于硬腭的扫描基线以及层厚１．５ｍｍ、层隔１ｍｍ重叠扫描，应作为临床ＨＲＣＴ检查的扫描技术。     

双螺旋CT门脉血管成像理想扫描参数和方法的研究

目的；探讨双螺旋CT门脉血管成像（DSCTP）理想扫描层厚，螺距，三维成像技术，资料与方法：采用Elscint双螺旋CT机扫描，94例患者，分为3组：A组：螺距1，层厚2.5mm，B组；螺距1．5，层厚2．5;3C,螺距1，层厚5mm，以最大强度投影法（MIP），表面阴影显示地（SSD）重建门静脉三维影像。比较不同层厚和螺距组合，不同成像技术对门脉显示的差别。比较各组横断面图像噪声大小及对DSCTP的影响。结果：（1）DSCTP图像质量，A、B组的效果均佳，优于C组。（2）MIP较SSD显示的血管丰富，小分支显示优于SSD。（3）B组噪声最大，但对DSCTP无明显影响。结论：DSCTP最佳扫描层厚为2.5mm，螺距为1.5,MIP为理想三维成像技术。     

腹腔动脉与肠系膜上动脉的螺旋CT血管造影初探

探讨螺旋ＣＴ血管造影（ｓｐｉｒａｌｃｏｍｐｕｔｅｄｔｏｍｏｇｒａｐｈｙａｎｇｉｏｇｒａｐｈｙ,ＳＣＴＡ）对腹腔动脉及其分支与肠系膜上动脉干的显示能力及扫描技术。方法腹部ＳＣＴＡ检查结果正常者３０例,平扫后行小剂量试验。取胰体水平腹主动脉为靶血管,以峰值时间为２秒定为最佳延迟扫描时间。ＳＣＴＡ以３．５ｍｌ／ｓ速度经肘前脉注入碘造影剂９０－１１０ｍｌ,由于侧向足侧扫描,扫描参数为螺距１．０层厚３．２ｎ     

肺部螺旋CT薄层扫描技术

目的：讨论螺旋ＣＴ扫描技术在肺部疾病检查中的应用价值。方法：３７例经手术病理证实的肺部病变均作螺旋ＣＴ扫描检查,层厚３￣５ｍｍ,ｐｉｔｃｈ１￣２,重建间隔１￣２ｍｍ。所有图像均在ＧＥ Ａｄｖａｎｔａｇｅ Ｗｉｎｄｏｗｓ２．０工作站上进行后处理,重建方式为表面显示法（ＳＳＤ）和最大密度投影法（ＭＩＰ）法。结果：３７例１￣５ｃｍ大小的病灶在ＣＴ图像上全部得以显示。１１你腺癌的供血血管,１０例细小毛刺,     

CT机准直系统故障检修

ＣＴ机准直系统故障检修朱兴树杨金华秦敏聂聪刘建秦ＥｌｓｃｉｎｔＣＴ机使用１．２ｍｍ、２．５ｍｍ层厚条件扫描时，不能进入曝光准备状态，出错提示为：Ａ－ｐｌａｎｅＳＷｃａｎｎｏｔｄｅｆｉｎｅ（Ａ面层厚不能定义），使用５ｍｍ、１０ｍｍ层厚条件，ＣＴ机可以完...     

正常听骨链的CT仿真内镜和三维重建

探讨正常听骨链ＣＴ仿真内镜（ＣＴＶＥ）和三维（３Ｄ）重建方法及其应用价值。材料和方法：２０例无中耳疾病者采用层厚１．０ｍｍ、螺距１．０轴位薄层扫描,骨算法、０．１ｍｍ～０．２ｍｍ间隔重建,分别做ＣＴＶＥ成像、表面（ＳＳＤ）和骨最大密度投影（ＭＩＰ）３Ｄ重建,观察和比较ＣＴＶＥ和３Ｄ显示正常听骨链的能力。结果：ＣＴＶＥ上,锤、砧骨及锤砧关节显示率都是１００％,镫骨底板显示率为３５％,仅２５％能分辨镫     

骨关节创伤的螺旋CT三维影像应用研究

目的：探讨螺旋ＣＴ三维影像（ＳＳＤ和ＭＰＲ）在骨关节创伤中的应用价值及相关的技术要点。方法：研究经Ｘ线和螺旋ＣＴ证实的骨关节创伤病例８５例。扫描参数：（１）３ｍｍ层百,４．５ｍｍ床速和１￣２ｍｍ重建间距;（２）５ｍｍ层厚、５￣７．５ｍｍ床速和２ｍｍ重建间距;作ＳＳＤ时阈值范围之低值为１２０￣１８０,观察ＳＳＤ和ＭＰＲ的窗宽和窗位分别为３０００￣３２００、１０００￣１２００和８００￣１０００、２５０     

支气管树的多排螺旋CT三维研究

目的评价多排螺旋CT(MDSCT)三维重建显示段以下中小气道的能力。方法20例健康志愿者行准直1mm,Pitch1.75的螺旋高分辨率扫描,分别用标准(FilterB)和高滤过重建算法(FilterD)重建横断面图像,间隔0.6mm。其中10例同时做增强扫描。16个新鲜肺叶充气标本,用3组方案扫描,准直分别为0.5mm、1.0mm和2.5mm,Pitch1.75,FilterD重建,间隔相应为0.3mm、0.6mm和1.3mm。用种子技术行支气管表面遮盖显示(SSD)重建,比较平扫与增强、不同滤过算法和不同层厚显示支气管的等级和长度。结果在活体,采用平扫重建的SSD图像优于增强,用FilterD重建的SSD图像优于FilterB,其中以平扫FilterD图像所做SSD最佳,能显示99.8%的4级、大部分5级及部分6级支气管。在肺标本,0.5mm组显示5～8级支气管明显优于1.0mm和2.5mm组,能显示全部7级和部分8级支气管。结论采用MDSCT、0.5～1.0mm准直的高分辨率扫描后行SSD重建能从平面和立体直观地显示4～7级支气管,评价该范围内的支气管病变。     

肝脏疾病对双螺旋CT门静脉血管成像质量的影响

评价肝脏疾病因素对双螺旋ＣＴ门脉血管成像质量的影响。材料与方法９７例患者进行了ＤＳＣＴＰ成像，其中肝脏ＣＴ扫描下沉上对轻度异常者６２例，肝脏病较严重者３５例。结在ＤＳＣＴＰ图像质量方面，甲组优于乙组，即肝硬化，门脉高压，巨块型肝癌或弥漫型肝癌，门脉栓度塞等，门脉成像质量差。     

Technical analysis of volume-rendering algorithms: application in low-contrast structures using liver vascularisation as a model

AIM: To assess the influence of pre-set volume-rendering opacity curves (OC) on image quality and to identify which absolute parameters (density of aorta, hepatic parenchyma and portal vein) affect visualization of portal vascular structures (low-contrast structures). MATERIALS AND METHODS: Twenty-two patients underwent a dual-phase spiral CT with the following parameters: collimation 3 mm, pitch 2, increment 1 mm. Three scans were performed: one without contrast medium and the latter two after the injection of contrast material (conventionally identified as 'arterial' and 'portal'). The images were sent to a workstation running on an NT platform equipped with post-processing software allowing three-dimensional (3D) reconstructions to generate volume-rendered images of the vascular supply to the liver. Correlation between the absolute values of aorta, liver and portal vein density, OC parameters, and image quality were assessed. RESULTS: 3D images generated using pre-set OC obtained a much lower overall quality score than those produced with OC set by the operator. High contrast between the liver and the portal vein, for example during the portal vascular phase, allows wider windows, thus improving image quality. Conversely, the OC in the parenchymal phase scans must have a high gradient in order to better differentiate between the vascular structures and the surrounding hepatic parenchyma. CONCLUSIONS: Image features considered to be of interest by the operator cannot be simplified by the mean of pre-set OC. Due to their strong individual variability automatic 3D algorithms cannot be universally applied: they should be adapted to both image and patient characteristics.     

The Quality of Reconstructed 3D Images in Multidetector-Row Helical CT: Experimental Study Involving Scan Parameters

Objective

To determine which multidetector-row helical CT scanning technique provides the best-quality reconstructed 3D images, and to assess differences in image quality according to the levels of the scanning parameters used.

Materials and Methods

Four objects with different surfaces and contours were scanned using multidetector-row helical CT at three detector-row collimations (1.25, 2.50, 5.00 mm), two pitches (3.0, 6.0), and three different degrees of overlap between the reconstructed slices (0%, 25%, 50%). Reconstructed 3D images of the resulting 72 sets of data were produced using volumetric rendering. The 72 images were graded on a scale from 1 (worst) to 5 (best) for each of four rating criteria, giving a mean score for each criterion and an overall mean score. Statistical analysis was used to assess differences in image quality according to scanning parameter levels.

Results

The mean score for each rating criterion, and the overall mean score, varied significantly according to the scanning parameter levels used. With regard to detector-row collimation and pitch, all levels of scanning parameters gave rise to significant differences, while in the degree of overlap of reconstructed slices, there were significant differences between overlap of 0% and of 50% in all levels of scanning parameters, and between overlap of 25% and of 50% in overall accuracy and overall mean score. Among the 18 scanning sequences, the highest score (4.94) was achieved with 1.25 mm detector-row collimation, 3.0 pitch, and 50% overlap between reconstructed slices.

Conclusion

Comparison of the quality of reconstructed 3D images obtained using multidetector-row helical CT and various scanning techniques indicated that the 1.25 mm, 3.0, 50% scanning sequence was best. Quality improved as detector-row collimation decreased; as pitch was reduced from 6.0 to 3.0; and as overlap between reconstructed slices increased.     

螺旋CT血管造影判断肺癌与中央肺动静脉的关系

目的 评价螺旋ＣＴ血管造影（ｓｐｉｒａｌ ＣＴ ａｎｇｉｏｇｒａｐｈｙ,ＳＣＴＡ）判断肺门区肺癌侵犯中央肺血管的准确性及其临床价值。方法 对３例病变在肺门区、术前诊断为肺癌的患者进行ＳＣＴＡ检查。分别以手术所见的３０９支血管和病理观察的６９支血管为标准,对比３ｍｍ间隔增强横断面ＣＴ和ＳＣＴＡ图像判断肿瘤与肺静脉关系的准确性。结果 （１）ＳＣＴＡ的几种重建法所得图像判断血管与肿瘤的关系各有优缺点。（     

Detection of pulmonary metastases with multi-detector row CT scans of 5-mm nominal section thickness: autopsy lung study

PURPOSE: To determine the effect of changing pitch and collimation on depiction of pulmonary metastases on scans of 5-mm section thickness obtained with multi-detector row computed tomography (CT) compared with those obtained with single-detector row CT. MATERIALS AND METHODS: In five autopsy lungs, 1,013 metastatic 0.5-30.0-mm nodules were detected at helical CT with 1-mm collimation and histopathologically diagnosed as metastases. Each nodule was numbered, and its localization was recorded as the standard for subsequent studies. Four types of scans of 5-mm section thickness were obtained with multi-detector row CT and four sets of helical pitch and table speed, respectively, as follows: set A, 3:1 and 7.5 mm per rotation; set B, 6:1 and 15 mm per rotation; set C, 6:1 and 30 mm per rotation; set D, conventional and 5-mm interval. Conventional helical CT scans (set E) were obtained with 5-mm collimation at single-detector row CT. Two independent observers evaluated the five sets of CT scans. RESULTS: Acquisition times for sets A-D, respectively, were 1.9, 3.8, 7.5, and 1.5 times faster than they were for set E. The mean numbers of detected nodules were 671 (66%) in set A, 661 (65%) in set B, 678 (67%) in set C, 654 (65%) in set D, and 656 (65%) in set E; there was no significant difference in the number of detected nodules among the five sets (P =.997, McNemar test and Bonferroni equation). CONCLUSION: Regardless of varying pitch or detector collimation, multi- and single-detector row CT scans obtained with 5-mm section thickness have almost the same ability to depict pulmonary metastases and are equivalent.     

Evaluation of image quality and dose in renal colic: comparison of different spiral-CT protocols

The aim of this study was to test different technical spiral-CT parameters to obtain optimal image quality with reduced X-ray dose. Images were acquired with a spiral-CT system Philips Tomoscan AVE1, using 250 mA, 120 kV, and 1-s rotational time. Three protocols were tested: protocol A with 5-mm thickness, pitch 1.6, slice reconstruction every 2.5 mm; protocol B with 3-mm thickness, pitch 1.6, slice reconstruction every 1.5 mm; and protocol C with 3-mm thickness, pitch 2, slice reconstruction every 1.5 mm. Two phantoms were employed to evaluate the image quality. Axial images were acquired, then sagittal and coronal images were reconstructed. Finally, the absorbed X-ray dose for each protocol was measured. Regarding image quality, 5-mm-thick images (protocol A) showed greater spatial resolution and lower noise compared with 3-mm-thick images (protocols B and C) on the axial plane; 3-mm reconstructed sagittal and coronal images (protocols B and C) showed an improved image quality compared with 5-mm reformatted images (protocol A). Concerning X-ray dose, the mean dose was: protocol A 19.6 +/- 0.8 mGy; protocol B 14.4 +/- 0.6 mGy; protocol C 12.5 +/- 1.0 mGy. Our study supports the use of thin slices (3 mm) combined with pitch of 1.6 or 2 in renal colic for X-ray dose reduction to the patient and good image quality.     

Influence of helical CT parameters on spatial resolution in CT angiography performed with a subsecond scanner.

RATIONALE AND OBJECTIVES: In helical CT, the beam collimation, table feed (TF) per tube rotation, voltage, current, reconstruction increment, kernel, linear interpolation algorithm (LIA), and contrast are variable parameters. The purpose of this study was to determine which of these parameters are most important to minimize partial volume effects for improving spatial resolution in CT angiography. METHODS: Phantom vessel stenoses of different lengths (2, 8 mm) and diameters (0.5, 1, 2, 3, 4 mm) were scanned with helical CT using a constant tube rotation time of 0.75 sec and 42 selected combinations of the above-mentioned parameters. Orthogonal targeted maximum intensity projections of the stenoses were ordered according to the increase in blurring and noise in a consensus reading by two radiologists blinded to the parameters used. RESULTS: Three millimeters of collimation and TF in conjunction with a 180 degrees LIA and > 250 Hounsfield unit contrast density was considered the optimal parameter combination and enabled a continuous visualization of the stenoses down to 0.5 mm in diameter. A collimation of 1 or 2 mm and 5 mm was considered inferior to a collimation of 3 mm because of, respectively, noise and blurring. With 3 mm collimation, significant blurring occurred when a pitch larger than 1.5 was used. A 3 mm collimation with a pitch of 2 (6 mm TF) was found to be superior to a collimation of 5 mm in conjunction with a pitch of 1 (5 mm TF). With 5 mm collimation, the short stenoses could be visualized only when using a 180 degrees LIA and a TF per tube rotation smaller than 7 mm. Eight and 10 mm collimations failed to depict the short stenoses. CONCLUSIONS: Collimation had the most influence on image quality in CT angiography, followed by LIA, pitch, and contrast density. Decreasing the reconstruction increment to less than one third of the TF or increasing the voltage or current beyond standard values did not improve the delineation of the stenoses. For screening examinations, the authors recommend the use of 3 mm collimation, 180 degrees LIA, and a pitch of 2.