多层螺旋CT重建参数对头颈部肿瘤MPR图像质量的影响

目的　分析多层螺旋CT(MSCT)重建及重组参数对头颈部肿瘤MPR图像质量的影响 ,以便选择最佳的参数组合。资料与方法　使用GELightspeedUltra 8层螺旋CT扫描机对 6 7例头颈部肿瘤患者进行扫描。分为两部分 ,第一部分 2 8例 ,分别对原始数据进行 1.2 5mm、2 .5mm层厚的轴面重建 ,重叠率均为 5 0 %。图像重组时 ,分别采用层厚 1mm、2mm、3mm和 5mm。第二部分 39例 ,分别采用 0 %、2 5 %、5 0 %和 75 %的重叠率和 1.2 5mm层厚进行轴面重建 ,然后采用 1mm层厚进行图像重组。应用双盲法评价各组图像质量 ,并进行统计学处理。结果　第一部分 ,在软组织、骨质和伪影方面组内差异有极显著性 (P <0 .0 1) ,1.2 5mm层厚轴面重建的各组MPR图像中 ,1mm层厚组对软组织和骨质的显示好于其他各组 (P <0 .0 1)。第二部分 ,在软组织、病变、骨质和伪影方面组内差异有极显著性 (P <0 .0 1) ;在软组织和病变方面 ,5 0 %与 75 %重叠率图像质量最佳 ,两者差异无显著性 (P >0 .0 5 ) ;在骨质方面 75 %重叠率组图像质量高于 5 0 %组 (P <0 .0 5 ) ;在伪影方面 ,5 0 %重叠率组好于 75 %组 (P <0 .0 1)。结论　头颈部肿瘤MSCT图像后处理采用 1.2 5mm层厚、5 0 %重叠率进行轴面重建后 ,用 1mm层厚的MPR图像能很好地显示软组织、病变     

多层螺旋CT颈动脉成像:层厚与成像方法的相关研究

目的 通过比较2种不同的扫描层厚对颈动脉多层螺旋CT（MDSCT）成像的影响以期获得合理的扫描参数。资料与方法 随机选择无脑缺血症状或脑梗死患者和有症状者共42例，随机分成1.3mm层厚组和3.2mm层厚组，其他扫描参数不变。采用最大密度投影（MIP）和容积重建（VR）2种后处理成像方法。根据颈动脉血管边缘的清晰度，颈动脉的分支级别显示情况进行综合评分。由2位有经验的放射科医师用盲法评分，所有统计工作由SPSS软件完成。结论 2种不同扫描层厚对颈动脉血管成像的总体质量与重建方法有关。应用MIP重建时，1.3mm层厚组明显优于3.2mm层厚组，应用VR时，两组图像的总体质量均优，差别并不明显。结论 多层螺旋CT颈动脉血管成像的总体质量的总体质量不仅取决于层厚的大小，还取决于图像的重建方法。     

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。     

多层螺旋CT血管造影在大血管病变术后复查中的应用

目的 评价多层螺旋CT血管造影术在大血管病变腔内隔绝术或血管搭桥术后复查中的临床应用价值。材料与方法 34例大血管病变腔内隔绝术或血管搭桥术后行多层螺旋CT血管造影术,采用准直2．5mm,层厚3.0mm,螺距为6,重建方法为容积漫游技术（VR）、SSD及MIP,并对三种方法进行比较。结果 主动脉瘤及夹层动脉瘤行腔内隔绝术后23例,血管搭桥术后7例,同时行腔内隔绝术及血管搭桥术后4例;2例出现渗漏,VR均能显示,SSD、MIP显示1例。VR图像能清晰显示内支架的位置及形态,对搭桥血管的位置、形态、吻合口及远侧段血管情况显示良好,明显优于SSD及MIP。结论 多层螺旋CT能在较短时间内进行大范围的扫描,有利于大血管病变的检查;VR图像优于SSD及MIP,能为术后情况提供更多信息。     

多层CT仿真支气管镜成像参数的优化

目的　探讨合理的多层螺旋CT仿真支气管镜成像扫描和重建参数。方法　 1 2 0例健康志愿者均分为 6组 ,分别接受不同参数组合的扫描 (MarconiMX 80 0 0机型 ) ,包括层厚 6 5、3 2mm(准直分别为 5 0、2 5mm) ,螺距 1 2 5、1 75 ,曝光量 1 95、1 0 0、50mAs,标准分辨率和高分辨率扫描 ,所有病例均 50 %重叠重建 ,其中第 1、2组根据不同重建间隔及不同滤过算法组合共 5种方法重建。分别对第 1段支气管 (S1 )作CT仿真支气管镜 (VB)观察 ,测定VB下最末端支气管内径。结果(1 )扫描层厚和曝光量影响VB效果 ,层厚 3 2mm时可观察S1最小支气管内径为 2 1 8～ 2 63mm ,明显优于层厚 6 5mm时的 3 2 5mm(t=3 61 9,P <0 0 1 ) ,曝光量则以 1 95mAs为佳 (F =8 35 ,P <0 0 1 )。而螺距和扫描分辨率则无明显影响 (P >0 0 5)。 (2 )重建间隔显著影响VB效果 ,第 2组中VB效果以重建间隔 0 5mm时为优 (F =3 53 ,P <0 0 5) ,但 1 6与 1 0间及 0 5与 1 0间差异无显著性意义。 0 5mm时可观察S1最小支气管内径为 (1 68± 0 2 1 )mm ,1 6mm时可观察S1最小支气管内径为 (2 1 0± 0 36)mm。第 1组中VB效果以重建间隔 3 2mm时最差 (F =3 2 0 ,P <0 0 5) ,2 0与 1 0mm时差异无显著性意义。 2 0mm时可观察S1最小     

上肢动脉病变的多层CT血管造影

目的:探讨多层CT血管造影(MSCTA)在上肢动脉病变诊断中的应用.方法:对临床疑诊上肢动脉病变的41例患者行MSCTA检查,扫描范围自颈根部上10cm至中指末端,扫描层厚5mm,重建层厚1.25mm,重叠50%.全部病例完成容积显示(VR)、最大密度投影(MIP)和曲面重组(CPR)处理.结果:全部病例得到正确诊断,并充分显示细节,包括动静脉畸形16例、锁骨下动脉狭窄7例、动脉栓塞9例、动脉瘤3例、大动脉炎3例、动脉扭曲3例,其中25例病例诊断经手术证实,10例经DSA证实.结论:MSCTA能很好显示上肢动脉各种病理性改变的形态学特征,并帮助明确诊断.     

颅颈联合CTA中准直与螺距最佳匹配的选择

目的 :探讨多层螺旋CT颅颈联合动脉成像时准直与螺距的最佳匹配方案。方法 :扫描设备为飞利浦MX80 0 0四层螺旋CT机。采用追踪触发技术启动诊断扫描 (触发阈值设定为 75HU)。将 4 0例无头颈部动脉系统疾病的志愿者按扫描参数的不同随机分为A(准直 1.0mm ,螺距 1.75 0 )、B(准直 2 .5mm ,螺距 0 .6 2 5 ) 2组 ,探讨颅颈联合MSCTA时准直与螺距的恰当匹配。以最大强度投影和容积再现法重建动脉影像。统计方法采用四格表资料的 χ2 检验和成组设计的两样本均数t检验 (双侧 ,α=0 .0 5 )。结果 :A、B两组对Ⅰ～Ⅳ级血管的显示率无显著性差异 ;对Ⅴ级动脉分支的显示能力存在显著性差异 (χ2 =3.91,P <0 .0 5 ) ,A组的显示能力高于B组。动脉Ⅰ～Ⅴ级分支的图像质量A、B两组间均存在显著性差异 (P <0 .0 5 )。B组对Ⅰ -Ⅱ级动脉的成像质量优于A组。A组对Ⅲ～Ⅴ级动脉的成像质量优于B组。结论 :①颅颈联合MSCTA可系统显示头颈部血管 ,避免分段成像的遗漏或不必要的重复、追加扫描。②颅颈联合CTA采用准直1 0mm、螺距 1.75 0优于准直 2 .5mm、螺距 0 .6 2 5 ,这种匹配方式对小血管显示佳。     

多层螺旋CT脑血管造影容积重建技术对颅内动脉瘤的诊断及临床应用价值

目的：探讨多层螺旋CT血管造影（MSCTA）容积重建（VR）技术对颅内动脉瘤的诊断及价值。方法：对37例临床怀疑颅内动脉瘤的患者进行MSCTA检查，其中6例另行DSA检查。全部患者CT扫描获得原始图像后采用VR技术对图像进行三维重建，10例同时采用最大强度投影（MIP）进行重建。结果：37例患者MSCTA共发现43个动脉瘤，其中多发动脉瘤5例（4例2个，1例3个）。VR图像上所测动脉瘤直径2.5—38mm。6例DSA患者发现6个动脉瘤，与CTA结果基本相符。结论：MSCTAVR技术是一种简便、微创而且相对可靠的诊断颅内动脉瘤的方法，对于指导手术或介入治疗颅内动脉瘤有重要价值。     

SCT薄层扫描和图像重建对肝脏小病变诊断敏感性的临床研究

目的 :探讨SCT薄层扫描和图像重建技术在肝脏小病变检出和显示方面的应用价值。方法 :原发性肝癌 2 2例 ,进行SCT薄层扫描和图像重建。 5mm准直 ,于动脉期和门脉期分别进行全肝扫描 (Pitch =1)。选层厚 6.5mm和10 0mm进行图像重建 ,前者重建间隔分别取 2 .5mm和 5 .0mm ,后者分别取 4.0mm和 8.0mm。根据病灶大小 ,按≤10 0mm ,11.0～ 2 0 .0mm ,2 1.0～ 3 0 .0mm分为三组 ,并分别对在不同层厚和重建间隔下病灶检出的敏感性和显示情况进行分析并进行统计学处理。结果 :≤ 10 .0mm组、11～ 2 0 .0mm组的病灶检出敏感性在不同层厚和重建间隔均差异有显著性意义 (P <0 0 5 ) ,而确定病灶数只在部分层厚和重建间隔差异有显著性意义 (P <0 .0 5 ) ;2 1.0～ 3 0 .0mm病灶敏感性仅在层厚 6.5mm、间隔 2 .5mm和层厚 10 .0mm、间隔 8.0mm差异有显著性意义 (P <0 .0 2 5 )。结论 :应用SCT薄层扫描和重叠重建技术 ,明显提高肝脏小病变检出的敏感性 ,并且可以改善病变的显示 ,提高诊断的可信度     

四层螺旋CT下肢动脉造影常规扫描参数优化研究

目的：探讨4层螺旋CT在下肢动脉造影中具有实用价值和理想三维重建图像的扫描技术参数。方法：使用东芝Aquilion 4层螺旋CT机对60例患者分3组进行下肢动脉造影,准直选择2mm、3mm、4mm,螺距分别为2.0625、1.375、1.375,层厚分别以2mm、3mm、4mm,间隔分别以1mm、1.5mm、2mm重建。在工作站分别做VR、MIP、CPR成像,对各组图像质量评分后作统计学对比分析。结果：在不增加CTDI的前提下,2mm层厚Z轴图像优于3mm、4mm层厚图像,横断图像没有显著性差异,2mm层厚图像噪声高于3mm、4mm层厚图像,但在可接受范围内。结论：4层螺旋CT机用2mm扫描层厚、2.0625螺距、1mm重建间隔,可获得满意Z轴图像,并具有实际操作意义。     

16层CT蛛网膜下腔造影

蛛网膜下腔造影后进行CT扫描充分结合了腔道造影和CT断层成像的优势,16层CT同时还提供了优秀的三维重建,使CT蛛网膜下腔造影技术得到了充分的发挥.本文就其中的CT椎管造影和脑室脑池造影的应用技术和效果作一论述.     

Influence of observer experience and training on proficiency in coronary CT angiography interpretation

Purpose

To assess the influence of experience and training on the proficiency in coronary CT angiography (CCTA) interpretation of practitioners with different levels of experience.

Methods and materials

Nine radiologist and cardiologist observers with varying prior CCTA experience ranging from novice to expert independently analyzed two case series of 50 catheter-correlated CCTA studies for coronary artery stenosis (0%, ≤49%, 50–74%, 75–99%, or 100%). Results of the first case series were unblinded and presented along with catheter angiography results to each reader before proceeding to the second series. Diagnostic accuracy on a per-segment basis was compared for all readers and both case series, respectively.

Results

Correlation coefficients between CCTA and catheter angiography initially ranged between good (r = 0.87) and poor (r = 0.26), depending on reader experience, and significantly (p < 0.05) improved in the second case series (range: r = 0.42 to r = 0.91). Diagnostic accuracy was significantly (p < 0.05) higher for more experienced readers (range: 96.5–97.8%) as compared to less experienced observers (range: 90.7–93.6%). After completion of the second case series for less experienced readers sensitivity and PPV significantly (p < 0.05) improved (range: 62.7–67.8%/51.4–84.1%), but still remained significantly (p < 0.05) lower as compared to more experienced observers (range: 89.8–93.3%/80.6–93.3%).

Conclusion

The level of experience appears to be a strong determinant of proficiency in CCTA interpretation. Limited one-time training improves proficiency in novice readers, but not to clinically satisfactory levels.     

First performance evaluation of a dual-source CT (DSCT) system

We present a performance evaluation of a recently introduced dual-source computed tomography (DSCT) system equipped with two X-ray tubes and two corresponding detectors, mounted onto the rotating gantry with an angular offset of 90°. We introduce the system concept and derive its consequences and potential benefits for echocardiograph (ECG)-controlled cardiac CT and for general radiology applications. We evaluate both temporal and spatial resolution by means of phantom scans. We present first patient scans to illustrate the performance of DSCT for ECG-gated cardiac imaging, and we demonstrate first results using a dual-energy acquisition mode. Using ECG-gated single-segment reconstruction, the DSCT system provides 83 ms temporal resolution independent of the patient’s heart rate for coronary CT angiography (CTA) and evaluation of basic functional parameters. With dual-segment reconstruction, the mean temporal resolution is 60 ms (minimum temporal resolution 42 ms) for advanced functional evaluation. The z-flying focal spot technique implemented in the evaluated DSCT system allows 0.4 mm cylinders to be resolved at all heart rates. First clinical experience shows a considerably increased robustness for the imaging of patients with high heart rates. As a potential application of the dual-energy acquisition mode, the automatic separation of bones and iodine-filled vessels is demonstrated. An erratum to this article can be found at     

High-resolution computed tomography (HRCT) in the detection of “early asbestosis”

Two radiologists reviewed in masked fashion 144 standard chest radiographs, previously judged as normal by other readers, within a cohort of asymptomatic shipyard workers exposed to amosite. Among the 144 workers we selected subjects (n = 72) who fitted the following criteria: (1) documented occupational exposure to asbestos; (2) absence of any clinical symptomatology suggestive of asbestosis or of any other lung disease. Thirty-eight of them had standard chest radiogrphs that were confirmed as normal by both our radiologists, while 34 showed suspected pleural plaques or a very slight parenchymal involvement. These 72 subjects underwent high-resolution CT (HRCT): pleural plaques were shown in 33, parenchymal alterations in 7, and both pleural and parenchymal involvement in 13. HRCT findings were strictly correlated to the duration of amosite exposure and to the latency time since first exposure. Sensitivity, specificity and diagnostic accuracy values of standard chest radiographs were calculated with respect to HRCT and found to be, for pleural and parenchymal findings respectively: sensitivity 53% and 19%; specificity 72% and 94%; accuracy 60% and 72%. In conclusion, pleural and/or pulmonary involvement in asbestos-exposed workers can be shown by HRCT before the appearance of any symptomatology and abnormality on chest radiography. Furthermore the HRCT findings are correlated to the duration of exposure and latency time. time. Correspondence to; P. Boraschi     

Suitability of helical multislice acquisition technique for routine unenhanced brain CT: an image quality study using a 16-row detector configuration

Subjective and objective image quality (IQ) criteria, radiation doses, and acquisition times were compared using incremental monoslice, incremental multislice, and helical multislice acquisition techniques for routine unenhanced brain computed tomography (CT). Twenty-four patients were examined by two techniques in the same imaging session using a 16-row CT system equipped with 0.75-width detectors. Contiguous “native” 3-mm-thick slices were reconstructed for all acquisitions from four detectors for each slice (4×0.75 mm), with one channel available per detector. Two protocols were tailored to compare: (1) one-slice vs four-slice incremental images; (2) incremental vs helical four-slice images. Two trained observers independently scored 12 subjective items of IQ. Preference for the technique was assessed by one-tailed t test and the interobserver variation by two-tailed t test. The two observers gave very close IQ scores for the three techniques without significant interobserver variations. Measured IQ parameters failed to reveal any difference between techniques, and an approximate half radiation dose reduction was obtained by using the full 16-row configuration. Acquisition times were cumulatively shortened by using the multislice and the helical modality.     

A retrospectively ECG-gated multislice spiral CT scan and reconstruction technique with suppression of heart pulsation artifacts for cardio-thoracic imaging with extended volume coverage

A method for cardio-thoracic multislice spiral CT imaging with ECG gating for suppression of heart pulsation artifacts is introduced. The proposed technique offers extended volume coverage compared with standard ECG-gated spiral scan and reconstruction approaches for cardiac applications: Thin-slice data of the entire thorax can be acquired within one breath-hold period using a four-slice CT system. The extended volume coverage is enabled by a modified approach for ECG-gated image reconstruction. For a CT system with 0.5-s gantry rotation time, images are reconstructed with 250-ms image temporal resolution. Instead of selecting scan data acquired in exactly the same phase of the cardiac cycle for each image as in standard ECG-gated reconstruction techniques, the patient's ECG signal is used to omit scan data acquired during the systolic phase of highest cardiac motion. With this approach cardiac pulsation artifacts in CT studies of the aorta, of paracardiac lung segments, and of coronary bypass grafts can be effectively reduced.     

CT colonography: results and limitations

Meta-analysis of data from studies of CT colonography suggests that it has excellent per-patient average sensitivity and average specificity for detection of adenomatous polyps and cancer. However, while its potential as a screening test is undoubted, there are several current limitations that will need to be overcome before it can be considered seriously by health policy makers. These revolve around issues of generalisability, which is inhibited most by a lack of trained observers and access to CT scanners, and a paucity of data relating to cost-effectiveness. Whether offering CT colonography as an alternative to competing strategies will genuinely enhance compliance also needs further and more detailed attention.