多层螺旋CT扫描层厚、重建间隔和多平面重建图像质量相关性的实验研究

目的探讨Mx80004层螺旋CT机具有实用价值和理想的多平面重建(MPR)技术参数方法用Mx8000CT机对人结肠标本行6.5mm、5.0mm、3.2mm、2.0mm及1.0mm不同层厚扫描,分别进行2.0mm、1.0mm和0.5mm不同间隔重建,在工作站做肠腔纵切面的MPR(包括CPR)成像对各组MPR图像质量进行评分后作统计学对比分析结果在相同间隔重建的MPR图像中,以层厚越薄得分越高在相同层厚的MPR图像中,重建间隔越小,评分相对越高;0.5mm与1.0mm重建间隔间的图像质量相比无明显统计学差异1.0mm层厚的扫描范围太小,CT剂量指数(CTDI)明显高于其它扫描层厚;2.0mm层厚的扫描范围达88mm,且CTDI与剩余层厚者较接近结论Mx80004层螺旋CT机用2.0mm扫描层厚、1.0mm间隔重建,可获取满意质量的MPR图像,并具有实际操作意义     

CT扫描层厚改变对图像质量的影响及控制

ＣＴ扫描层厚改变对图像质量的影响及控制胡永胜影响ＣＴ图像质量的参数有空间分辨率、噪声和低对比检测能力、伪影以及窗宽、窗位等［１］。根据文献，噪声的平方与探测器发射的光子数和层厚成反比［２］，所以噪声与层厚直接相关。在实践中，我们也发现层厚减小时扫描，...     

胸部多层螺旋CT扫描:机架旋转时间对图像质量的影响

目的 :前瞻性评价机架旋转时间对胸部图像 ,包括横断面及多平面重建图像质量的影响。方法 :60例患者分为两组 ,采用GELightSpeedUltra 8层螺旋CT扫描仪直接增强扫描 ,机架旋转时间分别选择 0 .8s和 0 .5s。按照制订的标准 ,对比两组图像的图像质量 ,进行统计学分析。结果 :0 .8s和 0 .5s组显示野和扫描范围相似 ,两组扫描时间分别为(2 4 .9± 3 .2 )s和 (1 5 .6± 1 .7)s,差异有极显著性意义 (W =465 .0 ,P <0 .0 0 1 )。两组CTDIW(CT剂量指数 )分别为1 7.56mGy和 1 0 .98mGy,DLP(剂量长度乘积 )分别为 (480 .4± 62 .5)mGy·cm和 (30 2 .1± 35 .5)mGy·cm ,差异有极显著性意义 (W =465 .0 ,P <0 .0 0 1 )。两组图像质量平均得分为 4 .0 7± 0 .42和 4 .1 6± 0 .35 ,差异无显著性意义 (W =851 .0 ,P =0 .342 )。两组重建图像质量平均得分为 2 .43± 0 .68和 2 .50± 0 .63 ,差异无显著性意义 (W =848.0 ,P =0 .32 0 )。结论 :机架旋转时间 0 .5s组胸部图像质量略好于 0 .8s组 (差异无显著性意义 ) ;患者接受的X线剂量则明显降低 ,平均降低了 37%。建议将机架旋转时间 0 .5s作为常规应用     

心率及重建相位窗对多层螺旋CT冠状动脉造影图像质量的影响

目的 探讨心率及重建相位窗对多层螺旋CT冠状动脉造影图像质量的影响。方法 80例健康体检者行16层螺旋CT回顾性心电门控条件下冠状动脉造影。结果 每位患者的4条冠状动脉分支(左冠状动脉主干、左前降支、左回旋支、右冠状动脉)分别用于图像质量分析。心率≤60次／min者，有82．1％(46／56支)的图像可用于诊断；心率61～70次／min者，有63．4％(104／164支)的图像可用于诊断；心率71～80次/min者，有41．20h，(28／68支)的图像可用于诊断；心率80次／min以上者有31．2％(10／32支)的图像可用于诊断。左冠状动脉前降支在60％～70％的重建相位窗时图像质量最佳，左冠状动脉回旋支在50％～60％时最佳，右冠状动脉重建相位窗为50％～70％较满意。结论心率及重建相位窗对多层螺旋CT冠状动脉造影图像质量有重要影响作用。     

低剂量CT筛查肺结核对图像质量的影响

目的：评价CT低剂量扫描筛查肺结节对胸部图像质量时影响。方法：对26例肺转移瘤患者，分别应用195mAs/6．5mm(剂量／层厚)、195/3．2、50/3．2、30／3．2扫描肺部，分别评价不同剂量条件和扫描层厚下图像噪声大小。肺结构显示的清晰度和患者的身高体重之间的关系。结果：30/3．2组的图像噪声大于50/3．2组，50/3．2组的大于195/3．2组，随扫描剂量的降低，图像清晰度或锐利度下降，50/3．2基本能保证图像质量，对某些结构的显示甚至优越于195/3．5，而30/3．2对身高体重比小于2．513者图像质量下降影响观察。结论：随扫描剂量的降低，图像质量下降，减薄层厚可以弥补低剂量的不足，50/3．2(剂量／层厚)基本能保证图像质量，可以满足诊断需要，甚至优越于195/3．5，根据身高体重比自动选择扫描剂量有助于提高对图像质量的控制。     

鼻窦低剂量CT扫描对图像质量影响的研究

目的探讨鼻窦CT扫描时单纯降低mA值,晶体接受的射线剂量及其对图像质量的影响。方法将50例行鼻窦冠状面CT扫描者根据有无炎症分为正常组(32例)与炎症组(18例)。每组患者根据扫描的mA值设置分为200mA和50mA组。正常组有8例,炎症组有7例同时行高分辨重建。用镁铜磷氟化锂[LiF(Mg·Cu·P)]热释光探测器测量晶体受到的照射剂量。评价不同条件、不同算法(软组织算法和高分辨算法)时的图像质量。评价指标为中鼻甲、钩突、上颌窦开口、筛漏斗、额隐窝、筛板。评价标准为未显示,0分;显示、但不清楚,1分;清楚显示,2分。左右单独计分。结果当mA值由200减至50时,晶体所接受的射线剂量由7339mGy降至1108mGy。两组差异有统计学意义(P<001)。而图像质量无明显下降(P>005)。对于正常组,高分辨重建有助于细小解剖结构的显示,对于炎症组高分辨重建并不能增加细节的显示程度。结论在单纯降低mA值的条件下,受检者所接受的射线剂量明显减少,虽然图像噪声有所增加,但图像仍然保持较好的诊断质量。     

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     

16层螺旋CT的多平面重建、曲面重建及容积重建在泌尿系统疾病诊断中的应用研究

随着螺旋CT的扫描速度和后处理功能的不断提高，其在泌尿系统疾病中的应用越来越广泛。可以用无创的方法探讨病理生理状态下泌尿系统在结构与功能上的改变。本文对我院自2005-07～2006—10期间所做的40例多平面重建、曲面重建及容积重建的泌尿系统疾病进行分析，探讨螺旋CT的多平面重建、曲面重建及容积重建在泌尿系统疾病中的诊断价值。     

Comparison of the image quality and radiation dose of different scanning modes in head-neck CT angiography

Objectives:To analyze and compare the radiation dose and image quality of different CT scanning modes on head-neck CT angiography.Methods:A total of 180 patients were divided into Group A and Group B. The groups were further subdivided according to different scanning modes: subgroups A1, A2, A3, B1, B2, and B3. Subgroups A1 and B1 used conventional CT protocol, subgroups A2 and B2 used the kV-Assist scan mode, and subgroups A3 and B3 used the dual-energy gemstone spectral imaging protocol. The CT dose index and dose–length product were recorded. The objective image quality and subjective image evaluation was conducted by two independent radiologists.Results:The signal-to-noise ratios, contrast-to-noise ratios, and subjective scores of subgroups A3 and B3 were higher than the other subgroups. In subgroups B1 and B2, the subjective scores of 9 patients and 12 patients were lower than 3, respectively. The subjective scores of subgroups B1 and B2 were lower than the other subgroups. There was no statistically significant difference in signal-to-noise ratios, contrast-to-noise ratios, and subjective scores between subgroups A1 and A2. The effective dose of subgroup A2 was 41.7 and 36.4% lower than that in subgroups A1 and A3, respectively (p < 0.05). In Group B, there were no statistically significant differences in CT dose indexvol, dose–length product, and ED among the subgroups (p > 0.05).Conclusion:In the head-neck CT angiography, the kV-Assist scan mode is recommended for patients with body mass index between 18.5 and 34.9 kg m⁻²; gemstone spectral imaging scanning mode is recommended for patients with body mass index ≥34.9 kg m⁻².     

单源双能 CT 不同重建层厚对标准水模 GSI 数据的影响

目的：探讨单源双能 CT 不同重建层厚对标准水模能谱成像的 CT 值、水(碘)浓度、SD 值的影响。方法使用 GE 公司单源双能 CT(Discovery CT 750 HD),选择辐射剂量相近(165~262.5 mAs)的8个扫描协议,对 GE 20 cm 直径的水模行 CT 能谱成像(GSI)扫描,管电压采用140 kVp 和80 kVp 瞬时切换,扫描视野 medium,螺距1.375,探测器宽度40 mm,每个协议采集6层5 mm 层厚图像(B 组),重建1.25 mm 层厚图像(A 组)。使用 AW4.5工作站,将面积约3000 mm2的圆形感兴趣区(ROI)置于水模的中心、3点、6点、9点、12点的位置进行测量,分别在70 keV 单能量图像上测量 A、B 2组的 CT 值和 SD 值,在水(碘)基图像上测量水(碘)浓度和 SD 值,分别采用独立样本 t 检验、配对样本 t 检验进行统计学分析。结果A 组及 B 组 CT 值和水(碘)浓度的差异无统计学意义(P >0.05),SD 值的差异有统计学意义(P <0.05)。A、B 2组水(碘)浓度的 SD 值均小于 CT 值的 SD 值,差异有统计学意义(P <0.05)。结论重建层厚的改变不会影响单源双能 CT GSI 扫描的 CT 值和水(碘)浓度,对 SD 值有影响。GSI 对物质浓度的测量及 CT 值测量更加准确。     

64层螺旋CT冠状动脉成像质量影响因素的分析

目的:分析64层螺旋CT冠状动脉扫描中影响成像质量的各种因素。方法:对89例怀疑冠心病或冠心病复查患者进行64层螺旋CT冠状动脉检查,回顾性分析成像质量,探讨心率及心率波动对冠脉成像质量的影响,pitch值与心率的关系,替代(override)功能的应用价值,从而优化扫描参数。结果:①心率及心率波动与冠脉成像质量成负相关;②心率与扫描/重建方式及pitch值存在相互对应关系;③心率替代功能的合理使用可以提高CT冠状动脉的成像质量。结论:通过控制心率及心率波动,选择心率替代功能,采取适当的扇区扫描/重建模式可以提高图像质量和冠状动脉诊断的可靠性。     

锥形束CT和多层螺旋CT对寰枢椎成像的辐射剂量和图像质量差异研究

目的比较锥形束CT(CBCT)和多层螺旋CT(MSCT)应用于寰枢椎成像的检查剂量和成像质量的差异。方法使用普兰梅卡CBCT扫描仪的30种曝光条件和东芝320排MSCT的15种曝光条件对头颈部体模进行扫描。基于蒙特卡罗算法剂量评价软件PCXMC计算CBCT的有效剂量(E);以剂量长度乘积(DLP)乘以成人颈部特异性转换系数得到MSCT的E值。两独立样本的t检验或Wilcoxon秩和检验用于比较两种成像方式的辐射剂量和主、客观图像质量。采用双盲法对图像的边缘清晰度、对比度、软组织层次、伪影进行5分制主观评分,测量感兴趣区(ROI)的信号与噪声,计算对比信噪比(CNR)。结果 CBCT容积剂量指数、E值分别为2.9 mGy、27.61 μSv,均低于MSCT的8.8 mGy、433.16 μSv,差异有统计学意义(z=-3.05、-5.25,P<0.05);CBCT组的噪声和CNR分别为27.74 HU和3.69,MSCT组为7.84 HU和27.1,差异有统计学意义(z=-5.39、-5.42,P<0.05);CBCT组的总体图像质量、对比度、伪影评分分别为3.5、3.0、5分,均高于MSCT组2.0、2.0、4.0分,差异有统计学意义(z=-2.32、-2.46、-3.31,P<0.05)。结论寰枢椎CBCT和MSCT扫描均可获得满足诊断要求的图像质量,与MSCT相比,CBCT寰枢椎扫描有效地降低了辐射剂量,符合辐射防护最优化原则。     

Investigating the relationship between virtual cystoscopy image quality and CT slice thickness

Objective

To investigate the effect of reconstruction slice thickness on image quality at CT virtual cystoscopy (VC).

Methods

Pelvic CT examinations in bladder cancer patients were reconstructed at different slice thicknesses (0.6–5 mm) and intervals, and resulting VC images assessed. Quality indicators were ridging, holes, floaters and dimpling artefacts, tumour definition, and an overall score, ranked 1 (best) to 7 (worst). CT number and standard deviation (SD) for bladder contents and bladder wall were recorded. The mean SD was used as a measure of noise, and the contrast-to-noise ratio (CNR) was calculated as the CT number difference between them divided by the average image noise. The mean CNR across the three levels was used for analysis. Each qualitative image quality measure was compared with CT number, noise and CNR measurements.

Results

Dimpling artefacts increased with thinner slice reconstruction and correlated with increased noise, often resulting in poor tumour definition. The best overall image quality score was seen for VC images reconstructed at 1.2 mm slice thickness, probably because of the competing effects of spatial resolution and CNR.

Conclusion

A slice thickness reconstruction <1.2 mm does not provide for better image quality at VC owing to the presence of increased noise.Flexible and rigid cystoscopy are invasive techniques employed in the diagnosis and follow-up of patients with suspected and treated bladder malignancy. Areas of mucosal abnormality can be directly visualised and resected or biopsied. However, the procedure is associated with a complication rate of 4–6%, depending on expertise [1-3], and visualisation of the entire mucosal surface of the bladder is not always possible, particularly in the presence of clot and debris. Other anatomical abnormalities within the bladder (such as diverticula) cannot be adequately accessed. Alternative diagnostic tools and imaging techniques have until now been unable to provide sufficient accuracy to replace this direct visualisation of the bladder.Recently, the availability of rapid image acquisition, and software permitting three-dimensional computer-rendered images, has led to interest in virtual reality imaging. Volume rendering processing techniques have developed such that it is now possible to simulate intraluminal navigation through any hollow viscus, as in conventional endoscopic procedures. The majority of virtual endoscopy development has been in CT virtual colonoscopy, which has developed into an accepted tool for the diagnosis and screening of colonic lesions [4]. The bladder also provides a suitable organ for virtual imaging: it is a hollow fluid-filled organ into which additional positive or negative contrast material can be instilled via urethral catheter or intravenously. CT virtual cystoscopy (VC) has been reported for the investigation of haematuria and diagnosis of bladder tumours [5-7].VC as an imaging modality is well described in the literature, but the optimum scanning technique remains unclear. Initial studies of VC used single-detector CT scanners and a collimation of 3–5 mm. These early reports demonstrate a low sensitivity for the detection of smaller tumours using a shaded surface technique of virtual imaging [8,9]. Most of these studies have used a collimation of 3 mm and reconstruction interval of 1–2 mm [6,10-15]. Dectection rates of >90% are reported with a lower size limit of 5 mm.Multidetector CT (MDCT) has the ability to image faster than single-detector CT and acquire multiple thin sections with near-isotropic voxels. Virtual reconstructions of these thin sections using volume rendering software could result in improved spatial resolution and the possibility to detect smaller abnormalities. As the technological capability to reconstruct with thinner slice thickness has improved, there has been a reported improvement in tumour detection rates without impairment of image quality for CT virtual colonoscopy; for every 1 mm increase in slice thickness, there is a decrease in sensitivity of 5% [16] and in specificity [17]. A slice thickness of 3 mm or below is currently recommended for CT virtual colonoscopy [18]. Although reports of VC using MDCT suggest an improvement in bladder tumour detection rates with reducing slice thickness [19-22], the optimal image acquisition variables for VC remain unknown.This study was performed to investigate the effects of reducing slice thickness on virtual CT reconstructions with the following objectives:

1. document artefacts associated with CT VC and image quality
2. define the effect of slice thickness on image quality variables
3. define the optimum image acquisition for CT VC.

     

定位像扫描参数对胸部CT影像质量和辐射剂量影响的模体研究

目的:探讨胸部CT定位像扫描参数(X射线管投照角度和管电压)的选择对图像质量和辐射剂量的影响规律,为临床实践中成像参数的选择提供指导。方法:选择不同扫描参数对成人胸部拟人模体进行定位像采集,X射线管投照角度(0°、90°和180°)、管电压(70、80、100、120和140 kV)和管电流(25 mA)共15种组合。...     

Dual-source CT coronary imaging in heart transplant recipients: image quality and optimal reconstruction interval

The image quality and optimal reconstruction interval for coronary arteries in heart transplant recipients undergoing non-invasive dual-source computed tomography (DSCT) coronary angiography was evaluated. Twenty consecutive heart transplant recipients who underwent DSCT coronary angiography were included (19 male, one female; mean age 63.1 +/- 10.7 years). Data sets were reconstructed in 5% steps from 30% to 80% of the R-R interval. Two blinded independent observers assessed the image quality of each coronary segments using a five-point scale (from 0 = not evaluative to 4 = excellent quality). A total of 289 coronary segments in 20 heart transplant recipients were evaluated. Mean heart rate during the scan was 89.1 +/- 10.4 bpm. At the best reconstruction interval, diagnostic image quality (score >/=2) was obtained in 93.4% of the coronary segments (270/289) with a mean image quality score of 3.04 +/- 0.63. Systolic reconstruction intervals provided better image quality scores than diastolic reconstruction intervals (overall mean quality scores obtained with the systolic and diastolic reconstructions 3.03 +/- 1.06 and 2.73 +/- 1.11, respectively; P < 0.001). Different systolic reconstruction intervals (35%, 40%, 45% of RR interval) did not yield to significant differences in image quality scores for the coronary segments (P = 0.74). Reconstructions obtained at the systolic phase of the cardiac cycle allowed excellent diagnostic image quality coronary angiograms in heart transplant recipients undergoing DSCT coronary angiography.     

多层螺旋CT膝关节低剂量扫描对影像质量的影响

目的:探讨多层螺旋CT低剂量膝关节扫描的可行性及其对图像质量的影响。方法:收集2009年5月~10月,100例行膝关节CT扫描者根据扫描的管电压高低分为2组(其他扫描条件不变),每组50例,A组110kV和B组80kV(管电压选择110kV和80kV是依据分别观察10例在此条件下扫描的患者图像,应用80kV而不影响诊断)。测量膝关节髌骨上缘水平后方肌肉软组织固定ROI的CT值,以CT值的标准差(SD)作为图像噪声。通过CT机自动得到平均容积CT剂量指数(CTDIvol),再计算出剂量长度乘积(DLP)。获得的图像通过双盲法进行质量评分,对两组CTDIvol值、DLP值、图像噪声、及图像质量评分均值用t检验进行比较。结果:A组和B组的CTDIvol值分别为(5.29±0.23)和(2.08±0.15)mGy,DLP值分别为(61.26±11.64)和(24.21±4.64)mGy.cm,B组较A组下降约(60.68)%,两者之间差异均有统计学意义(t值分别为(82.4)和(20.91),P0.01,B组噪声均值略高于A组(分别为12.22±2.97和16.55±2.96),t=-7.299,P=0.000,但两组图像质量平均评分分别为(4.86±0.40)分和(4.82±0.44)分,差异无统计学意义(t=0.475,P0.05)。结论:16层螺旋CT应用低kV设置(80kV)扫描膝关节可大幅度降低辐射剂量且所得图像质量不影响诊断。     

基于深度学习的重建算法对腹部胰腺和门静脉CT图像质量的改善价值

目的探讨深度学习重建算法(DLIR)相对于滤波反投影算法(FBP)和多模型迭代重建算法(ASIR-V)对腹部胰腺和门静脉CT图像质量的改善价值。方法选取行常规腹部CT增强检查的患者36例,所得图像分别采用DLIRL、DLIR-M、DLIR-H、FBP及30%ASIR-V、70%ASIR-V算法重建图像,所得6种重建图像由2位放射科医师采用双盲法对图像噪声、对比度及细微结构进行主观评价。通过分别测量不同重建算法图像的CT值、SD值、SNR和CNR,并进行组间比较,来观察不同重建算法对图像质量的影响。结果 6组图像的SNR、CNR差异均有统计学意义(P<0.05),其中DLIR-H图像的SNR和CNR最高。主观评分之间差异均有统计学意义(P<0.05),两位医师的主观评分一致性良好,Kappa≥0.70,其中DLIR-M的主观评分最高。结论与FBP和ASIR-V重建算法比较,DLIR能够有效降低图像噪声、提高图像质量,因此DLIR算法可用于提升腹部胰腺和门静脉CT图像质量,有较好的临床应用前景。     

Impact of body part thickness on AP pelvis radiographic image quality and effective dose

Introduction

Within medical imaging variations in patient size can generate challenges, especially when selecting appropriate acquisition parameters. This experiment sought to evaluate the impact of increasing body part thickness on image quality (IQ) and effective dose (E) and identify optimum exposure parameters.