SnapShot Assist方案和参数优化下的冠状动脉CT血管成像

目的:探讨运用SnapShot Assist软件不同方案和参数优化下,对冠状动脉CT血管成像(Coronary Computed Tomographic Angiography,CCTA)的图像质量和辐射剂量的影响。方法:98例患者采用SnapShot Assist进行自动分组行CCTA:A组(n=41,e BMI23)80 k Vp/700 m A成像,B组(n=38,23≤e BMI28)100 k Vp/650 m A成像和C组(n=19,e BMI≥28)120 k Vp/650 m A成像。每一组又分为前瞻性门控轴向扫描模式(心率≤65次/分钟)和回顾性门控螺旋扫描模式(心率65次/分钟)两个亚组。30例未采用SnapShot Assist软件的常规回顾性心电门控螺旋扫描模式CCTA患者为对照组。分析比较各组图像质量主观评分、对比噪声比(Contrast-to-Noise Ratio,CNR)、信噪比(Signal-to-Noise Ratio,SNR)和胸壁皮下脂肪的密度标准差(Standard Deviation,SD)、CT容积剂量指数(volume CT Dose Index,CTDIvol)和有效辐射剂量(Effective Dose,ED)。结果:(1)A、B和C组内前瞻性心电门控扫描模式图像质量主观评分均值高于回顾性心电门控扫描模式,但差异无统计学意义(P0.05)。实验组图像质量评分与对照组无明显差异(P0.05)。(2)与对照组相比,A、B和C组CTDIvol、ED均显著降低(P0.05),其中辐射剂量平均下降63%。A、B和C组中,前瞻性心电门控轴向扫描均比回顾性心电门控螺旋扫描的CTDIvol、ED明显降低(P0.05)。结论:SnapShot Assist对患者进行个性化方案选择下的CCTA,在不降低图像质量的同时有效减少了辐射剂量。     

256层螺旋CT前瞻性心电门控冠状动脉成像的临床应用价值及其对比剂浓度研究

目的:探讨256层螺旋CT前瞻性心电门控冠状动脉成像的临床应用价值及不同浓度对比剂对其成像质量、碘用量以及有效辐射剂量的影响。方法:对120例疑似冠心病患者行256层螺旋CT成像扫描,将患者随机分为前瞻性心电门控组和回顾性心电门控组;出院前再将前瞻性心电门控组患者按数表法随机分为低浓度对比剂组、中浓度对比剂组和高浓度对比剂组。比较各组成像质量、碘用量、有效辐射剂量。结果:前瞻性心电门控组与回顾性心电门控组图像质量主观评分分布、可评价节段率、优良率、有效碘用量、信噪比(SNR)、载噪比(CNR)、主动脉CT值(CT主)、主动脉噪声值(SD主)比较无统计学差异(P0.05)。前瞻性心电门控组有效辐射剂量显著低于回顾性心电门控组(P0.05)。高浓度对比剂组可评价节段率、优良率、有效碘用量、SNR、CNR、CT主显著高于低浓度对比剂组和中浓度对比剂组(P0.05),中浓度对比剂组CNR显著高于低浓度对比剂组(P0.05)。结论:前瞻性心电门控技术用于冠心病诊断的图像质量与回顾性心电门控技术无明显差异,但是前瞻性心电门控技术辐射剂量更低。前瞻性心电门控使用低浓度对比剂可以获得满足临床诊断需要的图像质量,且碘用量更少。     

宝石能谱CT GSI成像和常规成像在上腹部应用价值的对比研究

目的:探讨宝石能谱CT GSI扫描模式在上腹部检查中降低辐射剂量和优化图像质量的可行性及应用价值。方法:选择2016年9月至2016年12月期间我院40例拟行上腹部三期增强的患者,根据扫描模式将患者分为A组和B组,每组20例。A组患者采用宝石能谱CT常规扫描模式行螺旋扫描,管电压120 Kvp及自动毫安管电流,确定NI值为10。B组患者采用GSI模式行三期增强扫描收集门脉期图像。回顾性自适应统计迭代重建(ASIR)70kev单能量图像,应用ASIR Review工具收集0到100%ASIR的CT值、噪声值,计算图像信号噪声比(SNR)。记录各组剂量报告中CT剂量容积指数(CTDI vol)及剂量长度乘积(DLP),并计算有效剂量(ED),采用图像质量主观评分对图像进行评价。结果:B组CT值、噪声值及SNR均高于A组(P0.05),B组CTDIvol、DLP和ED均显著低于A组(P0.05);随着ASIR升高,SNR升高,但是图像质量主观评分先升高后降低。当ASIR为50%时,图像质量最高,不同ASIR的CT值、噪声值之间的差异无统计学意义(P0.05)。结论:宝石能谱CT GSI扫描模式的效果明显优于螺旋扫描,同时在降低图像噪声的前提下选择50%ASIR,可保障图像质量。     

大鼠活体胸部扫描中减少图像呼吸心跳伪影序列方案的探讨

目的开发256层螺旋CT大鼠活体胸部CT扫描中减少图像呼吸、心跳伪影的序列。方法采用飞利浦Brilliance-iCT对10只SD大鼠进行胸部CT成像。每只大鼠均采用A、B两种扫描方式, A方式为常规胸部CT扫描序列,为非心电门控螺旋扫描模式,B方式为非心电门控轴扫模式。两组均在120 kV条件下扫描,扫描长度为8 cm。对所得CT数据进行横断位与冠状位肺窗与软组织窗重建,观察图像并进行测量,比较两组图像的平均CT值、图像噪声、信噪比(SNR)、和主观图像质量评分的差异,并对不同观察者间主观图像质量评分的一致性进行检验。结果分析10例大鼠胸部CT扫描数据。A、B两种扫描序列的剂量长度乘积(dose length product,DLP)值分别为144.7 mGy/cm与72.2 mGy/cm。两组间肺组织CT值与肝组织CT值差异无显著性(t值分别为-0.205、0.545,P0.05),两组图像噪声差异无显著性(t值为-0.865,P0.05),两组图像肺组织的SNR差异无显著性(t值为0.903,P0.05),但肝组织的SNR值B组高于A组,差异有显著性(t值为-2.885,P0.05)。两位医师的评分结果的相关系数为0.763,诊断结果一致性良好。A、B两种扫描方式的图像主观质量评分为(2.5±0.53)分、(4.3±0.67)分,差异有显著性(χ~2值为14.76,P0.05)。结论大鼠胸部CT扫描采用非心电门控轴扫模式可获得与胸部常规CT扫描(非心电门控螺旋扫描模式)大致相当的CT值与噪声、信噪比,但采用非心电门控轴扫模式可以有效减少大鼠胸部图像的呼吸心跳伪影,降低辐射剂量,提高图像质量,提高观察者的诊断信心。     

应用反向滤过及迭代重建方法评估标准放射剂量与低剂量颈椎CT图像质量的对比研究

目的：利用反向滤过重建（filtered back-projecfion,FBP）及迭代重建（iterative reconstruction,IR）方法评估标准剂量及低剂量对颈椎CT图像质量的影响。方法：40例受检对象行颈椎CT检查,将其随机分为两组：标准剂量组（SD,120kVp,275mAs）及低剂量组（LD,120kVp,150mAs）,随机选择管电流值,所有数据均行FBP及IR重建。测量C3C4及C6C7椎间盘水平椎间盘、脊神经、脊髓、韧带以及周围软组织的图像噪声值（Imagenoise,IN）,信噪比（signal—to—noise,SNR）及对比信噪比（contrast—to—noise,CNR）。结果：在测量的各椎间盘水平,迭代重建的信噪比及对比噪声比要明显高于反向滤过重建方法,并有效的降低了图像噪声。低剂量迭代重建图像与标准剂量反向滤过图像相比无明显统计学意义。排除剂量及扫描层面的影响,椎间盘、脊神经及韧带的图像质量,迭代重建评分要明显高于反向滤过重建,结果具有统计学差异;而低剂量迭代重建图像质量评分与标准剂量反向滤过重建相比无明显差异。软组织及椎体的图像质量,迭代重建图像质量评分要低于反向滤过重建方法,结果具有统计学差异;而低剂量迭代重建图像质量评分与标准剂量反向滤过重建相比无明显差异。整体病例图像质量评分,迭代重建方法要高于反向滤过重建方法,低剂量迭代重建方法要高于标准剂量反向滤过重建方法。结论：应用低剂量扫描方式以及迭代重建方法进行颈椎CT检查可以为I临床提供较好的图像质量,对于椎间盘、脊神经、脊髓显示较好,对于周围软组织以及椎体来说,图像质量相对较差,同时可以降低大约40％的放射剂量。     

应用反向滤过及迭代重建方法评估标准放射剂量与低剂量颈椎 CT图像质量的对比研究

目的：利用反向滤过重建（filtered back-projection,FBP）及迭代重建（iterative reconstruction,IR）方法评估标准剂量及低剂量 对颈椎CT 图像质量的影响。方法：40 例受检对象行颈椎CT 检查,将其随机分为两组：标准剂量组（SD,120 kVp, 275 mAs）及低 剂量组（LD,120 kVp,150 mAs）,随机选择管电流值,所有数据均行FBP 及IR 重建。测量C3 C4 及C6 C7 椎间盘水平椎间盘、脊 神经、脊髓、韧带以及周围软组织的图像噪声值（Image noise,IN）,信噪比（signal-to-noise,SNR）及对比信噪比（contrast-to-noise, CNR）。结果：在测量的各椎间盘水平,迭代重建的信噪比及对比噪声比要明显高于反向滤过重建方法,并有效的降低了图像噪 声。低剂量迭代重建图像与标准剂量反向滤过图像相比无明显统计学意义。排除剂量及扫描层面的影响,椎间盘、脊神经及韧带 的图像质量,迭代重建评分要明显高于反向滤过重建,结果具有统计学差异;而低剂量迭代重建图像质量评分与标准剂量反向滤 过重建相比无明显差异。软组织及椎体的图像质量,迭代重建图像质量评分要低于反向滤过重建方法,结果具有统计学差异;而 低剂量迭代重建图像质量评分与标准剂量反向滤过重建相比无明显差异。整体病例图像质量评分,迭代重建方法要高于反向滤 过重建方法,低剂量迭代重建方法要高于标准剂量反向滤过重建方法。结论：应用低剂量扫描方式以及迭代重建方法进行颈椎 CT 检查可以为临床提供较好的图像质量,对于椎间盘、脊神经、脊髓显示较好,对于周围软组织以及椎体来说,图像质量相对较 差,同时可以降低大约40%的放射剂量。     

256排Revolution多参数调节下低剂量心脏冠脉成像应用

目的:研究256排Revolution多参数调节下低剂量扫描心脏冠脉成像(Coronary computed tomographic angiography,CCTA)的应用。方法:回顾性分析2016年3月15日至5月15日间在我院256排CT行CCTA的患者,分为心率稳定试验组(n=54例)和心率不稳定试验组(n=41例),同时选取在我院64排VCT行CCTA的患者为对照组(n=116例),对三组CCTA图像质量行主观和客观评估,比较有效辐射剂量的差异。结果:256排CT检查成功率和图像质量的主观评价均优于对照组(P0.05);信噪比(SNR)、对比噪声比(CNR)与对照组差异无统计学意义(P0.05);但有效辐射剂量明显降低(P0.05)。结论:256排CT多参数调节下检查冠脉在保证图像质量下可有效降低辐射剂量。     

多层螺旋CT Flash Spiral模式老年冠状动脉成像的图像质量及影响因素分析

目的:探讨老年多层螺旋CT Flash Spiral模式和Spiral模式的冠状动脉动脉成像质量及其影响因素。方法:选择我院2010年1月~2012年12月行多层螺旋CT冠状动脉成像老年患者186例,根据心率和心律将患者分为两组:A组98例行Flash Spiral模式扫描;B组88例行Spiral模式扫描,对两组扫描的冠状动脉分别做图像后处理。比较两组患者的一般情况、图像质量评分及辐射剂量,并统计分析心率变异性对图像质量的影响。结果:两组患者在年龄、性别构成、体重指数(BMI)、钙化积分方面差异无统计学意义(均P0.05);在心率、心率变异性方面,A组明显低于B组,差异有统计学意义(均P0.05);两组患者图像质量评分、图像噪声及对比信噪比(CNR)相比较,差异均无统计学意义(均P0.05);不可诊断节段基于血管节段评价A组和B组分别为1.98%和2.21%,基于患者评价分别为8.16%和6.82%,差异无统计学意义(均P0.05);A组扫描时间、容积CT剂量指数(CTDIvol)、剂量长度乘积(DLP)、单位有效剂量(ED)小于B组,差异有统计学意义(均P0.05);心率变异性10次/min患者冠状动脉图像质量明显低于心率变异性5~10次/min和≤5次/min(P0.05)。结论:采用多层螺旋CT Flash Spiral模式扫描老年冠状动脉成像质量与Spiral模式接近,但有效辐射剂量明显减少。心率变异性是影响老年患者Flash Spiral模式扫描图像质量的重要因素。     

能谱CT双低剂量在门静脉成像中的应用研究

目的:评估宝石能谱CT在低kV及低剂量对比剂的条件下,门静脉成像的图像质量及技术的可行性。方法:纳入临床建议行CT门静脉成像(CT Portal Venography,CTPV)检查且BMI28 kg/m~2的患者40例,分为试验组(采用低电压及低剂量对比剂)和对照组(采用常规电压及常规剂量对比剂)各20例。应用GE公司Discovery CT750HD宝石能谱CT进行扫描。试验组扫描参数:80 k V,300 m A,对比剂为威视派克(270 mg I/mL)60 mL,图像重建采用50%滤波反投影重建(FBP)+50%自适应统计迭代重建(ASIR);对照组扫描参数:120 kV,300 m A,对比剂为欧乃派克(350 mg I/mL)90 mL,图像重建采用100%滤波反投影重建(FBP)。评价图像质量采用目测5分法,记录扫描容积CT剂量指数(CTDIvol),剂量长度乘积(DLP),测量并计算图像噪声(Image Noise,IN)及肝内、外门静脉的对比噪声比(Contrast to Noise Ratio,CNR)。并应用独立样本t检验比较2组间图像质量评分、噪声值、对比噪声比(CNR)。结果:试验组和对照组图像质量评分分别为(4.0±0.5)、(4.1±0.5)分,差异无统汁学意义(t=0.805,P0.05)。试验组肝内噪声及肝外噪声分别为(21.2±2.1)HU、(21.6±2.3)HU,高于对照组(14.2±1.5)HU、(15.0±1.4)HU,差异有统计学意义(t值分别为11.993、11.091,P值均0.01);试验组肝内CNR及肝外CNR分别为3.6±0.9、5.1±0.8,低于对照组5.4±1.0、6.9±1.1,差异有统计学意义(t值分别为5.231、4.261,P值均0.01)。试验组所接受辐射剂量容积剂量指数CTDIvol(4.7±0.2)mGy和剂量长度乘积DLP(132.7±6.2)mGy·cm均低于对照组CTDIvol(13.7±0.3)mGy和DLP(395.2±22.1)mGy·cm,差异均有统计学意义(t值分别为102.781、51.089,P值均0.01)。结论:低剂量、等渗低浓度对比剂CTPV技术明显减少碘对比剂用量和射线暴露,并且满足临床诊断的需要。     

管电压对下肢CT血管成像辐射剂量及图像质量的影响研究

目的:研究管电压对下肢CT血管成像辐射剂量及图像质量的影响。方法:选取2016年1月-2017年10月于我院行下肢CT血管成像的患者102例,将其以随机数字表法均分成观察组与对照组,每组51例。对照组管电压取120kV,观察组管电压取80kV,其他扫描参数相同。分别比较两组辐射剂量情况、客观图像质量以及主观图像质量情况。结果:观察组CT剂量指数(CTDIvol)、计量长度乘积(DLP)、有效辐射剂量(ED)水平均明显低于对照组,差异均有统计学意义(P0.05)。观察组腹主动脉、髂总动脉、股动脉、腘动脉、胫前动脉、胫后动脉、腓动脉CT值以及图像噪声均明显高于对照组,差异均有统计学意义(P0.05),两组动脉对比噪声比(CNR)和信噪比(SNR)比较差异无统计学意义(P0.05)。观察组血管阶段显示评分、血管细节分支显示评分均明显高于对照组,而血管边缘锐利度评分明显低于对照组,差异均有统计学意义(P0.05)。结论:下肢CT血管成像采用80kV管电压扫描可有效降低患者所接受的辐射剂量,且能获取较为满意的图像,值得临床推广应用。     

High-Pitch,Low-Voltage and Low-Iodine-Concentration CT Angiography of Aorta: Assessment of Image Quality and Radiation Dose with Iterative Reconstruction

ObjectiveTo assess the image quality of aorta obtained by dual-source computed tomography angiography (DSCTA), performed with high pitch, low tube voltage, and low iodine concentration contrast medium (CM) with images reconstructed using iterative reconstruction (IR).MethodsOne hundred patients randomly allocated to receive one of two types of CM underwent DSCTA with the electrocardiogram-triggered Flash protocol. In the low-iodine group, 50 patients received CM containing 270 mg I/mL and were scanned at low tube voltage (100 kVp). In the high-iodine CM group, 50 patients received CM containing 370 mg I/mL and were scanned at the tube voltage (120 kVp). The filtered back projection (FBP) algorithm was used for reconstruction in both groups. In addition, the IR algorithm was used in the low-iodine group. Image quality of the aorta was analyzed subjectively by a 3-point grading scale and objectively by measuring the CT attenuation in terms of the signal- and contrast-to-noise ratios (SNR and CNR, respectively). Radiation and CM doses were compared.ResultsThe CT attenuation, subjective image quality assessment, SNR, and CNR of various aortic regions of interest did not differ significantly between two groups. In the low-iodine group, images reconstructed by FBP and IR demonstrated significant differences in image noise, SNR, and CNR (p<0.05). The low-iodine group resulted in 34.3% less radiation (4.4 ± 0.5 mSv) than the high-iodine group (6.7 ± 0.6 mSv), and 27.3% less iodine weight (20.36 ± 2.65 g) than the high-iodine group (28 ± 1.98 g). Observers exhibited excellent agreement on the aortic image quality scores (κ = 0.904).ConclusionsCT images of aorta could be obtained within 2 s by using a DSCT Flash protocol with low tube voltage, IR, and low-iodine-concentration CM. Appropriate contrast enhancement was achieved while maintaining good image quality and decreasing the radiation and iodine doses.     

不同剂量64排CT增强扫描结合三维重建在胃癌应用中的图像质量研究

目的:研究不同剂量64排CT增强扫描结合三维重建在胃癌应用中的图像质量。方法:90例胃癌行胃部64层螺旋CT三期增强扫描患者后根据管电压设置分成A、B、C三组:A组120KV、B组100KV、C组80KV。通过轴位图像结合三维重建(VR、MPR和MIP等)分析不同剂量下螺旋CT扫描结合三维重建图像诊断质量。结果:A、B两组的图像清晰度的差异无统计学意义(P0.05),A、B组剂量加权指数降低率的差异具有统计学意义,A、C两组间图像清晰度及剂量加权指数降低率的差异具有统计学意义(P0.05),B、C组两项差异具有统计学意义。结论:适当调整MSCT的剂量,可以获得与常规MSCT剂量完全相同的图像而且可以降低辐射。     

Low-dose paediatric cardiac and thoracic computed tomography with prospective triggering: Is it possible at any heart rate?

ObjectiveTo demonstrate that the use of step-and-shoot (SAS) mode in paediatric cardiac CT angiography (CCTA) is possible at heart rates (HR) greater than 65 bpm, allowing low-dose acquisition with single-source 64-slices CT.MethodsWe retrospectively included 125 paediatric patients (0–6 years). CCTA was performed with SAS at diastolic phase in 31 patients (group D, HR < 65 bpm), at systolic phase in 45 patients (group S, HR ≥ 65 bpm) and with non-gated mode in 49 patients (group NG). Effective dose (ED) and image quality using a 3-grade scoring scale (1, excellent; 2, moderate; 3, insufficient) of group S were compared with group D for coronary examinations and group NG for entire thorax vascular anatomy.ResultsFor coronary indications, median ED was 0.6 mSv in group D versus 0.9 mSv in group S (p < 0.01). For whole thorax indications, median ED was 2.7 mSv in group NG versus 1.1 mSv in group S (p < 0.001). The mean image quality score was (1.4 ± 0.6) points in group D, (1.4 ± 0.7) in group S for coronary indications (p = 0.9), (1.3 ± 0.6) in group S for whole thorax indications and (2.0 ± 0.0) in group NG (p < 0.001).ConclusionSAS mode is feasible in children with HR greater than 65 bpm allowing low-dose CCTA. It provided comparable image quality in systole, compared to diastole. SAS at the systolic phase provided better image quality with less radiation dose compared to non-gated scans for whole thorax examinations.     

64层螺旋CT不同剂量扫描对活动性继发性肺结核患者诊断价值、图像质量和辐射剂量的影响

目的:研究64层螺旋CT不同剂量扫描对活动性继发性肺结核患者诊断价值、图像质量和辐射剂量的影响,旨在为临床活动性继发性肺结核患者提供更为安全有效的检查方案。方法:将我院从2018年1月2020年1月收治的100例活动性继发性肺结核患者纳入研究。对所有患者分别进行低剂量(40 m A)以及常规剂量(120 m A)扫描和薄层重建。比较不同剂量扫描的诊断准确率、影像学表现、图像质量以及辐射参数、患者满意度。结果:64层螺旋CT低剂量扫描与常规剂量扫描诊断活动性继发性肺结核的准确率分别为92.00%、93.00%,两者比较差异无统计学意义(P>0.05)。低剂量扫描及常规剂量扫描在空洞、钙化灶、实变、磨玻璃密度影及树芽征发生率方面对比差异均无统计学意义(P>0.05)。低剂量扫描及常规剂量扫描在扫描图像质量、薄层重建图像质量方面对比差异均无统计学意义(P>0.05)。低剂量扫描各项扫描辐射参数均低于常规剂量扫描,差异有统计学意义(P<0.05)。低剂量扫描的患者满意度高于常规剂量扫描的患者(P<0.05)。结论:64层螺旋CT不同剂量扫描对活动性继发性肺结核患者的诊断价值及生成的图像质量相近,但低剂量扫描可有效降低辐射剂量,从而在一定程度上增加扫描的安全性,使患者满意度提升。     

Optimizing Radiation Dose Levels in Prospectively Electrocardiogram-Triggered Coronary Computed Tomography Angiography Using Iterative Reconstruction Techniques: A Phantom and Patient Study

Aim

To investigate the potential of reducing the radiation dose in prospectively electrocardiogram-triggered coronary computed tomography angiography (CCTA) while maintaining diagnostic image quality using an iterative reconstruction technique (IRT).

Methods and Materials

Prospectively-gated CCTA were first performed on a phantom using 256-slice multi-detector CT scanner at 120 kVp, with the tube output gradually reduced from 210 mAs (Group A) to 125, 105, 84, and 63 mAs (Group B–E). All scans were reconstructed using filtered back projection (FBP) algorithm and five IRT levels (L2-6), image quality (IQ) assessment was performed. Based on the IQ assessment, Group D(120 kVp, 84 mAs) reconstructed with L5 was found to provide IQ comparable to that of Group A with FBP. In the patient study, 21 patients underwent CCTA using 120 kV, 210 mAs with FBP reconstruction (Group 1) followed by 36 patients scanned with 120 kV, 84 mAs with IRT L5 (Group 2). Subjective and objective IQ and effective radiation dose were compared between two groups.

Results

In the phantom scans, there were no significant differences in image noise, contrast-to-noise ratio (CNR) and modulation transfer function (MTF) curves between Group A and the 84 mAs, 63 mAs groups (Groups D and E). Group D (120 kV, 84 mAs and L5) provided an optimum balance, producing equivalent image quality to Group A, at the lowest possible radiation dose. In the patient study, there were no significant difference in image noise, signal-to-noise ratio (SNR) and CNR between Group 1 and Group 2 (p = 0.71, 0.31, 0.5, respectively). The effective radiation dose in Group 2 was 1.21±0.14 mSv compared to 3.20±0.58 mSv (Group 1), reflecting dose savings of 62.5% (p<0.05).

Conclusion

iterative reconstruction technique used in prospectively ECG-triggered 256-slice coronary CTA can provide radiation dose reductions of up to 62.5% with acceptable image quality.     

能谱CT优化胃肿瘤扫描辐射剂量对肾上腺嗜铬细胞瘤的诊断价值

目的:探讨能谱CT优化胃肿瘤扫描辐射剂量对肾上腺嗜铬细胞瘤的诊断价值。方法:采用回顾性、抽样、随机研究方法选择2012年9月到2017年2月在我院诊治的肾上腺嗜铬细胞瘤患者59例作为研究对象,所有患者都给予常规CT扫描与能谱CT优化胃肿瘤扫描,记录和比较辐射剂量与图像质量。结果:所有病例包膜均完整,边缘清楚,肿瘤内见单发或多发低密度区,肿瘤实质区呈不均匀显著强化。常规CT与能谱CT的图像质量主观评分分别为3.89±0.45分和4.54±0.34分;常规CT与能谱CT图像的胃肿瘤CT值分别为31.94±6.39HU和35.29±5.19HU,对比都有显著差异(P0.05)。能谱CT图像的膀胱和皮下脂肪图像噪声值都显著低于常规CT图像,对比差异都有统计学意义(P0.05);能谱CT扫描的CTDIvol和DLP分别为12.39±3.48mGy和624.10±39.19mGy.cm,都显著低于常规CT扫描的14.09±4.13mGy和653.92±56.29mGy.cm(P0.05)。结论:能谱CT优化胃肿瘤扫描在肾上腺嗜铬细胞瘤诊断中的应用能有效减少辐射剂量与图像噪声,提高图像CT值与主观质量,临床应用价值更高。     

Prospectively versus Retrospectively ECG-Gated 256-Slice CT Angiography to Assess Coronary Artery Bypass Grafts — Comparison of Image Quality and Radiation Dose

Objective

In this retrospective non-randomized cohort study, the image quality and radiation dose were compared between prospectively electrocardiogram (ECG)-gated axial (PGA) and retrospectively ECG-gated helical (RGH) techniques for the assessment of coronary artery bypass grafts using 256-slice CT.

Methods

We studied 124 grafts with 577 segments in 64 patients with a heart rate (HR) <85 bpm who underwent CT coronary angiography (CTCA); 34 patients with RGH-CTCA and 30 patients with PGA-CTCA. The image quality of the bypass grafts was assessed by a 5-point scale (1 = excellent to 5 = non-diagnostic) for each segment (proximal anastomosis, proximal, middle, distal course of graft body, and distal anastomosis). Other objective image quality indices such as noise, signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) were assessed. Radiation doses were also compared.

Results

Patient characteristics of the two groups were well matched except HR. The HR of the PGA group was lower than that of the RGH group (62.0±5.0 vs. 65.7±7.4). For both groups, over 90% of segments received excellent or good image quality scores and none was non-evaluative. The image quality generally degraded as graft segment approached to distal anastomosis regardless of techniques and graft types. Image quality scores of the PGA group were better than those of the RGH group (1.51±0.53 vs. 1.73±0.62; p<0.001). There was no significantly difference of objective image quality between two techniques, and the effective radiation dose was significantly lower in the PGA group (7.0±1.2 mSv) than that of the RGH group (20.0±4.6 mSv) (p<0.001), with a 65.0% dose reduction.

Conclusions

Following bypass surgery, 256-slice PGA-CTCA is superior to RGH-CTCA in limiting the radiation dose and obtaining better image quality for bypass grafts.