多层面螺旋CT血管成像应用参数优化

目的 探讨多层面螺旋CT血管成像(MSCTA)中扫描参数和重建方法的影响。资料与方法 60例共120次MSCT扫描，Marconi Mx8000型4层CT扫描仪，分别将准直层厚5．0mm、2．5mm、1．0mm与PitchO．875、1．25、1．75相匹配，各组数据分别以0％、50％、70％重叠重建率，对容积再现(VR)重建血管图像的图像质量和血管分支级数显示评分，不同层厚、重叠重建率和Pitch分组比较，将准直层厚2．5mm、1．0mm组，重叠50％重建68次血管成像行最大密度投影(MIP)重建，与对应VR图像行配对t检验。结果准直层厚1．0mm组O％和50％重叠重建及准直层厚2．5mm组重叠重建率50％、70％图像得分无显著性差异，但与准直层厚2．5mm组重叠重建率0％及准直层厚5．0mm组图像得分有显著性差异；准直层厚2．5mm时3种Pitch图像得分无显著性差异；准直层厚2．5mm和1．0mm时VR重建和MIP重建的得分无显著性差异。结论MSCTA时选择适当的扫描重建参数，可以显示较多血管分支级数，获得较好的图像质量，其优化的条件为：准直层厚2．5mm，Pitch1．75，50％重叠重建，两种重建方法VR和MIP在显示血管方面无明显差别。     

肺动脉CT三维血管成像低剂量扫描的应用

目的 探索肺动脉三维血管成像多层螺旋CT低剂量扫描的可行性,以及肺动脉容积三维处理(VR)图像的质量与平扫SD值的关系.方法 选取行肺动脉CT检查的受检者87人.选取志愿者63人为低剂量组,其余24人采用常规剂量扫描作为常规组.两者平扫均采用常规剂量150 mAs,低剂量肺动脉增强扫描采用60 mAs.图像进行VR后处理后,按A、B、C 3个等级进行评定,两组VR图像进行质量等级比较.低剂量组平扫图像测量CT值的标准差SD值,与增强的VR图像质量等级关系进行受试者操作特性曲线(ROC)分析.结果 常规剂量组VR图像等级为A级的达到100%,在低剂量组VR图像等级为A级的达到85.7%.平扫SD值与肺动脉VR图像的质量相关性分析,ROC曲线下面积为0.906.结论 肺动脉三维血管成像的低剂量扫描切实可行.     

肺动脉CT三维血管成像低剂量扫描的应用

目的 探索肺动脉三维血管成像多层螺旋CT低剂量扫描的可行性,以及肺动脉容积三维处理(VR)图像的质量与平扫SD值的关系.方法 选取行肺动脉CT检查的受检者87人.选取志愿者63人为低剂量组,其余24人采用常规剂量扫描作为常规组.两者平扫均采用常规剂量150 mAs,低剂量肺动脉增强扫描采用60 mAs.图像进行VR后处理后,按A、B、C 3个等级进行评定,两组VR图像进行质量等级比较.低剂量组平扫图像测量CT值的标准差SD值,与增强的VR图像质量等级关系进行受试者操作特性曲线(ROC)分析.结果 常规剂量组VR图像等级为A级的达到100%,在低剂量组VR图像等级为A级的达到85.7%.平扫SD值与肺动脉VR图像的质量相关性分析,ROC曲线下面积为0.906.结论 肺动脉三维血管成像的低剂量扫描切实可行.     

蝶腭孔的CT三维成像

目的 探讨CT三维成像评价蝶腭孔相关结构的价值.方法 使用Philips Mx8000型多层CT对5个成人头颅标本进行准直1 mm或0.5 mm的容积采集,并将数据输入配套Mxview工作站(SGI O2)进行三维重建处理,包括容积显示(VR)和三维正交多平面重建(MPR).并将图像上测量的数据与标本上实际测量的数据进行配对t检验.同时用相同的技术对12例临床病人进行扫描重建,并与标本CT图像进行比较.结果 蝶腭孔区各结构均能在三维重建图像中直观、清楚地显示,并且在VR所测数据与实际标本上所测数据基本一致.临床病例检查图像与标本图像质量相当.结论 CT容积采集三维重建可以直观、立体地显示蝶腭孔相关结构,准确地测定相关数据,并可应用于临床.     

多层螺旋CT颈动脉成像:VR与MIP的对照研究

目的 比较多排螺旋CT颈动脉成像容积重建和最大密度投影重建在显示颈动脉病变方面的差异.方法 随机选择临床病例及实验动物共72例行CT颈动脉成像,其中,30例通过随机区组分成2组,注射速率分别采用3 ml/s、4 ml/s,扫描层厚为1 mm;另42例也随机分成2组,扫描层厚分别采用1 mm和3 mm,注射速率采用4 ml/s.采用最大密度和容积重建2种后处理成像方法.根据颈动脉血管边缘的清晰度、光滑度、颈动脉的分级以及对斑块的显示能力由3位高年资放射科医生进行综合评判.结果 在血管边缘光滑度方面,3 mm层厚组血管边缘多呈锯齿状,1 mm层厚组血管边缘多光滑;3 ml/s注射速率组血管边缘多毛糙,密度不均,4 ml/s组血管边缘光滑.应用容积重建时,在血管边缘光滑度方面,2组不同层厚间、2种不同速率间无明显差异.MIP显示硬斑块引起的狭窄受钙化程度的影响大,VR显示颈动脉狭窄时,受钙化的影响小,多层面容积重建可以直接显示斑块.结论 VR受技术因素影响小,显示硬斑块引起的狭窄有优势,但邻近结构可能影响分支血管的观察.     

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。     

64层螺旋CT对主动脉根部形态结构的评价

目的 研究主动脉根部及临近组织结构64层螺旋CT(MSCT)成像技术、影像解剖及其临床意义.方法 60例无明显主动脉、主动脉瓣膜疾病患者行MSCT检查,采用多平面重建(MPR)、容积再现(VR)及仿真内镜(VE)等方法重建并测量相关数据.结果 测得主动脉根部直径(22.79±3.31)mm,主动脉窦间距(33.43±3...     

多层CT扫描层厚、重建参数的选择对容积重建图像质量的影响

目的探讨多层CT扫描层厚、重建层厚、重建间隔的选择对CT容积重建图像质量的影响。选择适宜多层CT容积重建扫描的扫描层厚、重建层厚、重建间隔的最佳匹配。方法应用多层螺旋CT以不同扫描层厚对模拟病变的橡胶恐龙模型进行扫描，以不同的重建层厚和重建间隔重建出容积重建图像。由5位放射医生采用全盲法对重建的容积重建图像进行评价，以析因设计的方差分析对各图像的评分进行分析。结果不同的扫描层厚、重建层厚、重建间隔匹配重建出的容积重建图像质量评分均数不同。扫描层厚V1、重建层厚V2、重建间隔V3对重建的VR图像质量影响程度存在差异（P〈0．05）。系数分别为V1=1413.033V2=563.733V3=390.533、且三者因素具有交互作用。扫描层厚、重建层厚、重建间隔越小容积重建图像质量评分越高，在扫描层厚2．0mm。重建层厚2．0mm时，重建间隔为扫描层厚的1／2、1／3、1／4容积重建图像的质量没有明显的差异。结论多层CT容积重建图像扫描参数扫描层厚应选择2．0mm，重建层厚2．0mm，重建间隔1／2为最佳。图像质量主要有扫描层厚决定。     

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。     

MSCT肺血管成像对肺动脉栓塞的诊断价值

目的:探讨多层螺旋CT肺血管成像对肺动脉栓塞的诊断价值.方法:对24例肺动脉栓塞病例行多层螺旋CT肺动脉成像检查,图像采用1.0mm层厚、0.7mm层间距和0.75mm层厚、0.5mm层间距进行重建,CTPA后处理采用容积再现(VRT)、最大密度投影(MIP)和多平面重建(MPR),对重建的图像进行对照分析、比较优缺点.结果:24例病例中,病变共累及76支肺动脉,其中,主肺动脉6支、肺叶动脉36支、肺段动脉27支、亚段动脉7支.肺动脉栓塞病变显示,1.0mm及0.75mm层厚重建无显著性差异意义.结论:多层螺旋CT肺动脉成像具有安全、快速、无创优点,对肺动脉栓塞诊断特异性强、敏感性高,可作为肺动脉栓塞的首选检查方法.     

MR imaging of orbital and ocular disease

Magnetic resonance (MR) images of 27 patients with ocular and orbital pathology were reviewed retrospectively and correlated with computed tomography (CT), funduscopic examination, and tissue histology. Disease processes were classified by location into ocular, extraconal, intraconal, optic nerve, and orbital apex. The diagnostic efficacy of MR differed at each location. MR was very sensitive in detecting ocular, extraconal, and intraconal lesions larger than 5 mm but was insensitive in imaging smaller lesions and in detecting pathology of the optic nerve. The limitations of MR were related to 7 mm slice thickness and 2.6 mm interslice gap. The diagnostic accuracy is expected to improve markedly with further developments in thin-section imaging and use of surface coils.     

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.     

多层螺旋CT后处理技术在喉癌分期中的应用

目的探讨16层螺旋CT各种后处理技术在喉癌术前分期中的应用。资料与方法37例拟诊喉癌患者术前行准直为0．625mm螺旋CT扫描,利用扫描获取的容积资料行薄层1mm冠状、矢状、轴位多平面重组（MPR）、仿真喉镜（CTVL）、容积再现（VR）重建肿块与颈部邻近血管关系以及喉腔透明显示（RSP）等多种后处理技术,综合对喉癌术前TNM作出评估,并将影像分期结果与手术病理结果对照,评价该方法的准确性。结果16层螺旋CT术前对喉TNM分期与临床最终手术病理结果对照,其中TI期符合率为50％,T2期为60％,T3期为75％,T4期为81．25％。总体分期符合率为72．9％。尤其是1mm薄层MPR图像可明显提高对前联合、喉旁间隙、声门下有无受累以及喉软骨微浸润的判断。结论16层螺旋CT0．625mm层厚各向同性容积扫描,各种后处理技术的综合应用,在喉癌术前临床评估中具有很高的实用价值,值得推广应用。     

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。     

High-resolution spiral computed tomography with multiplanar reformatting, 3D surface- and volume rendering: a non-destructive method to visualize ancient Egyptian mummification techniques.

Ancient Egyptians used mummification techniques to prevent their deceased from decay. This study evaluates the potential of computed tomography (CT) in determining these techniques in a non-destructive way. Twenty-five mummies were studied by using high-resolution spiral CT, 1mm slice thickness for the head and 3mm slice thickness for the rest of the body. Images were reconstructed with 3D, multiplanar reformatting and volume rendering. In all cases the used mummification techniques could be reconstructed. The way the brain was removed, the presence of chemicals, like resin and natron, could be detected and the way the intestines were handled could be made visible. The use of CT is indispensable as a non-destructive method in the reconstruction of mummification techniques.     

Three-dimensional CT angiography of the pancreatic artery in 16-channel multislice CT: value of scanning with submillimetre collimation

The aim of this study was to assess the effects of the reconstructed thickness of axial images on image quality of CT pancreatic arteriography with 16-channel multislice CT. In 31 consecutive patients, raw data of arterial-phase scanning with 0.5 mm collimation were reconstructed in the following three ways: 0.5 mm thickness (effective thickness of 0.75 mm) at 0.4 mm intervals in Group 1; 1 mm thickness at 0.5 mm intervals in Group 2; and 2 mm thickness at 1 mm intervals in Group 3. For the visualization of major arteries and small arteries of the pancreatic head, four blinded readers independently performed side-by-side comparison of the CT arteriographic images generated from each axial dataset for the same patient using a three-dimensional volume-rendered technique. In all comparisons using a continuous rating scale, CT arteriographic images generated from thinner axial images were found to be significantly superior (p<0.01). The difference was more pronounced for small arteries. The degree of degradation from Group 1 to Group 2 was markedly smaller than that from Group 1 to Group 3 or from Group 2 to Group 3. For small arteries, paired images were assigned a grade of "almost equivalent" in 73%, 6% and 15% of the comparison between Group 1 and Group 2, Group 1 and Group 3, and Group 2 and Group 3, respectively. We concluded that the image quality of CT pancreatic arteriography, especially for small arteries, can be improved by reconstructing axial images with thinner thickness from the data obtained with submillimetre collimation.     

无创性3D—MSCTA超薄层亚毫米扫描技术在脑血管病变术前诊断与术后随访的临床应用价值

目的评价无创性3D—MSCTA超薄层亚毫米扫描技术在脑血管病变术前诊断与术后随访的临床应用价值。方法83例患者均用16层螺旋CT行0．5mm超薄层亚毫米扫描,CTA重建均用容积再现（VR）和最大密度投影（MIP）,部分选用曲面重建（CPR）技术,全部结果均经手术或DSA证实。结果83例患者中,单发动脉瘤41例,多发动脉瘤4例,动脉瘤术后瘤夹在位且血管显影正常32例,烟雾病2例,动静脉畸形（AVM）3例,海绵状血管瘤1例。结论3D—MSCTA超薄层亚毫米扫描技术实现了真正的各向同性扫描,能无创、精确、清晰显示脑血管病变,可作为脑血管病变首选检查方法。     

Under-reporting of osteoporotic vertebral fractures on computed tomography

Purpose

Osteoporotic vertebral fractures are frequently asymptomatic. They are often not diagnosed clinically or radiologically. Despite this, prevalent osteoporotic vertebral fractures predict future osteoporotic fractures and are associated with increased mortality and morbidity. Appropriate management of osteoporosis can reduce future fracture risk. Fractures on lateral chest radiographs taken for other conditions are frequently overlooked by radiologists. Our aim was to assess the value of computed tomography (CT) in the diagnosis of vertebral fracture and identify the frequency with which significant fractures are missed.

Materials and methods

The thoracic CT scans of 100 consecutive male and 100 consecutive female patients over 55 years were reviewed. CT images were acquired on General Electric Lightspeed multi-detector (MD) CT scanners (16 or 32 row) using 1.25 mm slice thickness. Midline sagittal images were reconstructed from the 3D volume images. The presence of moderate (25–40% height loss) or severe (>40% height loss) vertebral fractures between T1 and L1 was determined using an established semi-quantitative method and confirmed by morphological measurement. Results were compared with the formal CT report.

Results

Scans of 192 patients were analysed (95 female; 97 male); mean age 70.1 years. Thirty-eight (19.8%) patients had one or more moderate to severe vertebral fractures. Only 5 (13%) were correctly reported as having osteoporotic fractures in the official report. The sensitivity of axial CT images to vertebral fracture was 0.35.

Conclusion

Incidental osteoporotic vertebral fractures are under-reported on CT. The sensitivity of axial images in detecting these fractures is poor. Sagittal reformations are strongly recommended to improve the detection rate.     

Impact of Different CT Slice Thickness on Clinical Target Volume for 3D Conformal Radiation Therapy

The purpose of this study was to present the variation of clinical target volume (CTV) with different computed tomography (CT) slice thicknesses and the impact of CT slice thickness on 3-dimensional (3D) conformal radiotherapy treatment planning. Fifty patients with brain tumors were selected and CT scans with 2.5-, 5-, and 10-mm slice thicknesses were performed with non-ionic contrast enhancement. The patients were selected with tumor volume ranging from 2.54 cc to 222 cc. Three-dimensional treatment planning was performed for all three CT datasets. The target coverage and the isocenter shift between the treatment plans for different slice thickness were correlated with the tumor volume. An important observation from our study revealed that for volume < 25 cc, most of the cases were underdosed by 18% with 5-mm slice thickness and 27% with 10-mm slickness. For volume > 25 cc, the target underdosage was less than 6.7% for 5-mm slice thickness and 8% for 10-mm slice thickness. For 3D conformal radiotherapy treatment planning (3DCRT), a CT slice thickness of 2.5 mm is optimum for tumor volume < 25 cc, and 5 mm is optimum for tumor volume > 25 cc.     

Electron beam CT versus 16-slice spiral CT: how accurately can we measure coronary artery calcium volume?

The purpose of this study was to investigate how accurately CAC volume we can be measured using electron beam computed tomography (CT) and 16-slice spiral CT. CAC models with known volume attached to a cardiac phantom were scanned. The error of measurement, variability between measured and real volumes, and inter-scan measurement variability were obtained. For spiral CT, seven different parameters were included: (1) slice thickness (0.625 mm, 1.25 mm and 2.5 mm), (2) retrospective spiral electrocardiograph (ECG)-gated or prospective axial ECG-triggering, (3) overlapping or non-overlapping. The error of measurement was 15% on electron beam CT and 8–20% on spiral CT. CAC volumes were underestimated in 92% and overestimated in 8% of the electron beam CT scans. Volumes were underestimated in 79%, correct in 5% and overestimated in 16% of the spiral CT scans. The best measurement and the least variability was observed on 0.625-mm retrospective spiral ECG-gated CT (error of 8%), a significant result (t-test: P<0.01) when compared with electron beam CT. CAC volume measurement on CT scanners may be significantly different and often underestimates the real volume of CAC. For precise evaluation of CAC volume, thin-slice retrospective spiral ECG-gated scan using a spiral CT scanner is desirable.