低剂量能谱计算机断层扫描成像联合迭代重建对兔VX2肝癌模型的应用

目的:探讨低剂量能谱计算机断层扫描(computed tomography,CT)单能量成像联合自适应统计迭代重建(adaptive statistical iterative reconstruction,ASiR)技术在兔VX2肝癌模型中的图像质量及对他的检出价值.方法:采用CT引导下穿刺法将VX2肝癌移植瘤植入24只新西兰大白兔肝左叶,于种植后14 d行能谱CT腹部增强扫描,采用40%ASiR重建动静脉期70 keV单能量图像,得到A组和B组图像.24 h后再对此批兔子行常规100kV腹部增强扫描,动静脉期图像使用滤波反投影(filtered back projection,FBP)算法重建,得到C组和D组图像.由两名放射学家对4组图像质量采用5分评分制法进行主观评分,观察者间一致性采用Kappa检验.测量4组图像背部肌肉标准差作为图像噪声,测量肝脏肿瘤信噪比(signal to noise ratio,SNR)和对比噪声比(contrast to noise ratio,CNR),A组与C组、B组与D组间均采用配对t检验比较.并记录两次扫描的CT剂量指数(CT dose index volume,CTDIvol)和有效辐射剂量(effective dose,ED),亦采用配对t检验比较.结果:22只大白兔种植成功,种植14 d后两种CT扫描均检出肿瘤24个.GSI模式扫描组有效辐射剂量较常规扫描组降低约27%(1.30 mSv±0.09 mSv vs 1.78 mSv±0.13 mSv,P=0.021).动脉期图像A组主观评分高于C组(4.09分±0.71分vs 3.80分±0.67分,P=0.049).静脉期图像B组主观评分高于D组(4.16分±0.67分vs 4.75分±0.65分,P=0.005).动脉期A组图像噪声低于C组(7.52 HU±1.12 HU vs 10.83 HU±2.17HU,P0.001).静脉期B组图像噪声低于D组(8.25 HU±1.74 HU vs 11.55 HU±2.86 HU,P0.001).A组肝肿瘤SNR和CNR均高于C组(P0.05).B组肝肿瘤CNR高于D组,两组间SNR差异无统计学意义.结论:在兔VX2肝癌模型中,能谱CT单能量成像联合ASiR技术与常规扫描相比可降低辐射剂量,并提供良好的图像质量和肝癌病灶显示.     

双能量计算机断层扫描单能量重建技术在主动脉缩窄患者血管内支架置入术后的应用

目的探讨双能量计算机断层扫描(dual-energy computed tomography,DECT)单能量重建技术在主动脉缩窄血管内支架置入术后的应用价值。方法回顾性分析2017年9月到2019年10月16例主动脉缩窄血管内支架置入术后随访并行胸主动脉DECT扫描的患者,后处理重建40～190 keV间隔为10 keV的共16组单能量图像及线性融合图像(M=0.5)并进行比较。客观图像评价测量计算了对比噪声比(contrast to noise ratio,CNR)、伪影指数(artifact index,AI)及噪声(noise,N)。主观图像质量评价由2名放射科医生对总体图像质量进行双盲评估。结果主观图像质量评价结果显示,90 keV的总体图像质量(均值0.7)最高。客观图像质量评价中,90 keV单能量图像具有最低的AI及N,优于线性融合图像(均P0.05),CNR高于线性融合图像(P0.05)。结论双能量CT单能量重建技术可以减少术后支架伪影,提高图像质量,最优能级为90 keV。     

低剂量个体化扫描对头颈部CT血管成像图像质量及辐射剂量的影响

目的探讨低剂量个体化头颈部CT血管成像扫描方案对图像质量及辐射剂量的影响。方法 80例可疑头颈动脉粥样硬化行头颈CT血管成像扫描患者,随机抽取20例采用常规剂量扫描（A组）,体质量指数（BMI）不限,管电压120 kV,管电流250 m As（机器设定值）;另60例患者按BMI〉24.9 kg/m^2、18.5～24.9 kg/m^2、﹤18.5kg/m^2分别入3个低剂量组（B、C、D组,每组20例）;B、C、D组管电压均为100 kV,管电流分别为250、200、150m As;余扫描条件各组相同。分析比较各组图像的辐射剂量、CT值、信号噪声比（SNR）、对比噪声比（CNR）及主观图像质量。结果 B、C、D组容积CT剂量指数（CTDIvol）、剂量长度乘积（DLP）及有效剂量（ED）较A组均明显降低;血管内CT值均明显上升（P均〈0.05）;低剂量各组图像噪声有所增加,但四组间SNR、CNR差异均无统计学意义;且低剂量组动脉重建图像质量、血管边缘及对图像的诊断信心评价整体满意,与常规组比较无统计学意义。结论在头颈部动脉成像时采用低剂量个体化扫描方案可使扫描方案的设计更加趋于合理化和个性化,在保证不影响图像诊断质量的同时能明显降低辐射剂量,减少对患者的辐射危害。     

Double Flash扫描方式在冠状动脉计算机断层扫描中的应用

目的 探讨双源计算机断层扫描（computerized tomography,CT）大螺距前瞻性心电触发采集模式（Flash模式）在冠状动脉CT中的应用价值.方法 随访中国人民解放军总医院行冠状动脉CT检查的患者120例,其中采用Double Flash扫描方式组60例（A组）,常规螺旋扫描方式组60例（B组）.入选患者在CT检查过程中心率均＜70次/min,窦性心律且节律整齐,且体质量＜100 kg.采用4分法对图像质量进行评价（1分为图像质量极好,2分为图像质量好,3分为图像质量一般,4分为图像质量差）,并记录两组患者整个扫描过程中的总有效剂量值及总剂量长度乘积.结果 两组间图像质量评分比较,差异无统计学意义（P＞0.05）.A组整个扫描过程中的总有效剂量值明显低于B组,差异有统计学意义[（2.6±0.8） mSv vs.（8.6±1.3） mSv,P＜0.05];总剂量长度乘积也明显低于B组,差异有统计学意义[（145.8±13.5） mGy·cm vs.（621.4±129.8）mGy.cm,P＜0.05].结论 双源CT大螺距前瞻性心电触发采集模式应用于心率＜70次/min的患者时与常规螺旋扫描模式比较,在保证图像质量的同时,还可显著降低辐射剂量.     

双层探测器光谱CT在颅内血管成像中的应用研究

目的对比双层探测器光谱CT（SDCT)不同keV单能级与常规颅内血管CTA的图像质量。 方法回顾性分析于首都医科大学附属北京天坛医院放射科自2020年4月至2021年3月行颅内血管光谱CT成像的80例患者的临床和影像资料。比较40~90 keV（间隔10 keV）能级图像和常规图像上血管的CT值及相对于胼胝体的对比噪声比（CNR）、图像质量、血管容积重建（VR）难易程度。 结果能级降低（90 keV降至40 keV）,血管CT值显著升高（颈内动脉C7段：242.16~1090.28 HU;基底动脉：217.17~1021.79 HU）,而胼胝体压部CT值无明显变化（29.30~37.76 HU）。低能级（40~60 keV）图像上血管的CNR、图像质量评分显著高于常规图像,且比常规图像易于VR,差异均有统计学意义（P<0.05）。 结论双层SDCT的低能级（40~60 keV）图像比常规图像更利于血管的显示,亦易于进行VR。     

双源CT双能量虚拟扫描与常规扫描在肝脏成像中的应用对比

正医源性辐射日渐受到人们关注。满足图像质量和诊断需要时尽可能降低CT的辐射剂量的研究显得尤为重要~([1])。与一般的多层螺旋CT相比,西门子双源炫速CT具有两个探测器及球管,每扫描一次即可获得两组不同的图像。而双能量虚拟扫描技术可控制放射剂量,从而代替常规扫描技术~([2])。本研究采用双源CT对患者肝脏分别实施常规平扫和双能量虚拟平扫,对比实施两种扫描方法后的图像质量以及辐射剂量等,     

迭代重建技术对双低剂量肺动脉CT血管造影图像质量分析

目的分析迭代重建技术对双低剂量肺动脉CT血管造影(CTA)检查图像质量的影响。 方法选取2018年2月至2021年2月我院行肺动脉CTA检查73例，随机分为对照组35例，观察组38例。对照组采用常规剂量滤波反投影重建，观察组采用双低剂量iDose⁴迭代重建技术。比较两组图像参数[背景噪声值(BN)、肺动脉CT值平均值(SI_vessel)、信噪声比(SNR)、对比噪声比(CNR)]、辐射剂量[容积CT剂量指数(CTDI_vol)、剂量长度指数(DLP)、有效吸收剂量(ED)]及图像质量，并分析典型病例的影像学表现。 结果观察组BN、SI_vessel、SNR、CNR参数高于对照组(P<0.05)；观察组CTDI_vol、DLP、ED辐射剂量低于对照组(P<0.05)；观察组图像质量优良率94.74%高于对照组77.14%(P<0.05)。 结论迭代重建技术应用于双低剂量肺动脉CTA检查中能降低辐射剂量，提高信噪比，改善图像质量。     

低剂量扫描联合低剂量对比剂在CT肺动脉成像应用

目的:探讨低剂量扫描联合低剂量对比剂在多层螺旋CT肺动脉成像(CTPA)的应用。方法:60例临床疑似肺栓塞的患者随机分为A、B两组,每组各30例。A组为试验组,扫描管电压为80kVp,对比剂采用碘海醇(300mg/mL)35mL及30mL0.9%氯化钠溶液。B组为对照组,扫描管电压为120kVp,对比剂采用碘海醇(300mg/mL)70mL及0.9%氯化钠溶液30mL。测量肺动脉主干至双侧亚段肺动脉的CT值,计算平均CT值。以肺动脉主干CT值的标准差代表图像噪声,记录CT实际容积剂量指数(CTDIvol)、剂量长度乘积(DLP)、并计算有效剂量(ED)。计算图像信噪比(SNR)及对比噪声比(CNR),对图像质量进行五级评分。结果:A组CDTIvol、DLP、ED分别为(6.21±0.89)mGy,(239.28±1.78)mGy·cm,(3.46±0.87)mSV。B组CDTIvol、DLP、ED分别为(12.07±1.38)mGy,(451.42±2.98)mGy·cm,(6.31±1.06)mSV。两组辐射剂量差异有统计学意义(P<0.05),A组患者的辐射剂量明显比B组降低46%。两组图像质量主观评分差异无统计学意义(P>0.05)。结论:应用低管电压联合低剂量造影剂在CTPA中是完全可行的,可以在保证图像质量的情况下明显降低的患者的辐射剂量和对比剂的用量。     

迭代重建技术在前门控结合体质量调节管电压管电流心脏CT成像的研究——降低辐射剂量及控制图像质量简

目的 探讨迭代重建技术（iDose4）在前瞻性心电门控结合体质量调节管电压管电流心脏螺旋计算机断层扫描（computerized tomography,CT）成像中降低辐射剂量及控制图像质量的应用价值.方法 选取实验猪10只,每只猪均进行以体质量调节管电压管电流为基础的常规剂量（A组）及在此基础上降低管电流[分别降低30％（B组）、50％（C组）、70％（D组）]的256层前瞻性心电门控心脏CT扫描,所有数据均分别采用滤波反投影（filtered back projection,FBP）和iDose4重建,计算猪接受的辐射剂量,测量升主动脉根部及左心室腔噪声、信噪比（SNR）、对比噪声比（CNR）,分别对总体图像质量和冠状动脉图像质量进行评分（5分法评分）,3分及以上为图像质量可满足诊断,并对两种重建方法处理后所得结果进行比较.结果 A、B、C、D组的有效辐射剂量（ED）分别为（3.13±0.63） mSv、（2.26±0.51） mSv、（1.61±0.36） mSv、（1.01±0.23）mSv.随着X线剂量降低,图像噪声增加,信噪比、对比噪声比降低,图像质量下降.各组内比较,iDose4重建的图像噪声均较FBP重建者明显降低,而信噪比及对比噪声明显提高,差异均有统计学意义（P均=0.000）.A、B、C、D各组内经FBP/iDose4重建后总体图像质量评分分别为（3.80±0.42）分/（4.60±0.52）分、（3.60±0.52）分/（4.40±0.52）分、（3.00±0.67）分/（3.80±0.42）分、（2.00±0.67）分/（3.40±0.52）分,各组内比较差异均有统计学意义（P＜0.05）.用FBP重建,A、B、C、D组近、远端冠状动脉的可诊断率分别为100％、95％、70％、20％和92％、72％、36％、0;经iDose4重建后,A、B、C组近、远端冠状动脉的可诊断率均大于经FBP重建后A组的可诊断率或与其相当（P＞0.05）,而D组的可诊断率明显低于FBP重建后A组的可诊断率,差异有统计学意义（P＜0.05）.结论 在前门控结合体质量调节管电压管电流心脏CT成像中,应用iDose4较FBP可显著降低图像噪声,提高信噪比及对比噪声比,提高图像质量;用iDose4重建可以在现有辐射剂量基础上降低50％的剂量进行扫描而图像质量保持不变.     

“三低”技术在CT体部血管一站式成像的应用价值

目的 评价低管电压、低对比剂浓度及低造影剂流速条件下行冠状动脉、肺动脉、主动脉全段及分支一站式CT血管成像的图像质量和辐射有效剂量的应用价值。方法 回顾性分析不同浓度造影剂下完成一站式血管扫描的60例患者,按不同的扫描条件和造影剂浓度分为A、B两组,每组30例。A组：管电压80 kV,管电流250 mA,碘浓度300 mg/mL,流速3.5 mL/s; B组：管电压100 kV,管电流200 mA,碘浓度320 mg/mL,流速5 mL/s。将两组图像质量进行客观评价,比较两组图像的血管(冠状动脉、肺动脉、主动脉全段主干分支)CT值、对比度噪声比(CNR)、图像噪声(PN)和辐射有效剂量。结果 两组图像质量主客观评价A组与B组冠状动脉各主干CT值及其PN(PN1),肺动脉主干、左右肺动脉CT值及其PN(PN2),主动脉各处CT值差异均有统计学意义(P<0.05);冠状动脉CNR(CNR1)、肺动脉CNR(CNR2)、主动脉PN(PN3)和主动脉CNR(CNR3)无统计学差异(P>0.05)。A、B两组血管计算机体层摄影血管造影辐射有效剂量分别为(3.7±0.7)mSv和(6...     

心脏双能量CT与负荷/静息心肌灌注显像和冠状动脉造影的对比研究

目的:探讨心脏双能量CT对冠状动脉狭窄和心肌灌注缺损的诊断价值。方法:34例临床可疑或已知冠心病患者行心脏双能量CT检查。重建冠状动脉CTA图像(dual-energy CT angiographyDE-CTA)和双能心肌灌注图(dual-energy CT perfusion DE-CTP)用于冠状动脉狭窄程度和心肌灌注缺损的评判,并与冠状动脉造影和负荷/静息心肌灌注显像(single photo emission computed tomographySPECT)为参考标准,评价心脏双能量CT对冠状动脉狭窄程度和心肌灌注缺损诊断的灵敏度、特异度、阳性预测值及阴性预测值。结果:1.28例符合纳入标准的患者进入本研究;2.DE-CTA显示408段冠状动脉,其中44段冠状动脉狭窄≥50%,以冠状动脉造影为参考标准,DE-CTA诊断冠状动脉狭窄的灵敏度、特异度、阳性预测值及阴性预测值分别为89.28%、97.70%、86.20%及98.29%,准确性为96.58%;3.DE-CTP显示心肌节段476段,其中90段显示心肌灌注缺损,以负荷/静息心肌灌注显像为参考标准,DE-CTP诊断心肌灌注缺损的灵敏度、特异度、阳性预测值及阴性预测值分别为85.71%、93.09%、74.07%及96.58%,准确性为91.71%,DE-CTP诊断心肌灌注缺损与负荷/静息心肌灌注显像,诊断心肌灌注缺损具有较好的一致性,kappa值0.74(P<0.001)。结论:双能量CT作为一项新的成像方法,不仅能够诊断冠状动脉狭窄,还能对病变冠状动脉的血流动力学改变做出准确判断。     

双源CT双能量冠状动脉斑块成像的初步应用

目的探讨双源CT双能量成像技术进行冠状动脉斑块成像的可行性。方法 40例病人行双能量CT冠状动脉斑块成像。结果 40例受检者均能得到冠状动脉成像的单能数据及双能量数据,其中10例行DSA者,CTA与DSA所见一致。其中3例行IVUS检查,共5处斑块,其中4处斑块双能图像与IVUS所见一致。结论单次对比增强双能量CT心脏成像,可同时获得优良的冠状动脉和冠状动脉斑块成像,并降低了射线剂量。     

Detection of gallbladder stones by dual-energy spectral computed tomography imaging

AIM:To evaluate the detectability of gallbladder stones by dual-energy spectral computed tomography(CT) imaging.METHODS:Totally 217 patients with surgically confirmed gallbladder stones were retrospectively analyzed who underwent single-source dual-energy CT scanning from August 2011 to December 2013. Polychromatic images were acquired. And post-processing software was used to reconstruct monochromatic(40 ke V and 140 ke V) images,and calcium-lipid pair-wise base substance was selected to acquire calcium base images and lipid base images. The above 5 groups of images were evaluated by two radiologists separately with 10-year experience in CT image reading. In the 5 groups of images,the cases in the positive group and negative group were counted and then the detection rate was calculated. The inter-observer agreement on the scoring results was analyzed by Kappa test,and the scoring results were analyzed by Wilcoxon test,with P 0.05 indicating that the difference was statistically significant. The stone detection results of the 5 groups of images were analyzed by χ2 test.RESULTS:There was good inter-observer agreement(k = 0.772). In 217 patients with gallbladder stones,there was a statistically significant difference in stone visualization between spectral images(40 ke V,140 ke V,calcium base and lipid base images) and polychromatic images(P 0.05). 40 ke V monochromatic images were better than 140 ke V monochromatic images(4.90 ± 0.35 vs 4.53 ± 1.15,P 0.05),and calcium base images were superior to lipid base images(4.91 ± 0.43 vs 4.77 ± 0.63,P 0.05),but there was no statisticallysignificant difference between 40 ke V monochromatic images and calcium base images(4.90 ± 0.35 vs 4.91 ± 0.43,P 0.05). In 217 gallbladder stone patients,there were 21,3,28,5 and 12 negative stone cases in polychromatic images,40 ke V images,140 ke V images,calcium base images and lipid base images,respectively,and the differences among the five groups were statistically significant(P 0.05).CONCLUSION:Monochromatic images and base substance images have a good clinical prospect in the iso-density stone detection.     

能谱CT成像对晶状体老化诊断价值的初步研究

目的 观察青年人和老年人正常晶状体的能谱CT表现,初步探讨能谱CT成像对晶状体老化的诊断价值. 方法 回顾性分析33例行能谱CT扫描的头颅图像中的正常晶状体30例,其中青年组(25～50岁)17例,34只晶状体,老年组(70～84岁)13例,26只晶状体,自动重建获得头颅混合能量和单能量图像(40～140keV),由2位放射科医师评估眼球区域射线硬化伪影情况,选择双侧晶状体为感兴趣区,获取双侧晶状体的CT能谱曲线,在40～110 keV范围内每隔5 keV记录对应单能量下晶状体的CT值,并对2组数值进行比较. 结果 晶状体单能量CT图像较混合能量CT成像伪影率显著降低(P＜0.01),青年组与老年组晶状体能谱曲线呈现不同形态,老年组晶状体CT值[(76.87±2.30)HU]较青年组[(81.33±2.48)HU]显著降低,各单能量下2组CT值均具有显著性差异(P＜0.01). 结论 能谱CT成像能够有效去除眶内射线硬化伪影,能够敏感地检测到晶状体老化所致的微小密度改变.     

Metal artifacts reduction in computed tomography: A phantom study to compare the effectiveness of metal artifact reduction algorithm,model-based iterative reconstruction,and virtual monochromatic imaging

The purpose of this study was to compare the effectiveness of a metal artifact reduction algorithm (MAR), model-based iterative reconstruction (MBIR), and virtual monochromatic imaging (VMI) for reducing metal artifacts in CT imaging.A phantom study was performed for quantitatively evaluating the dark bands and fine streak artifacts generated by unilateral hip prostheses. Images were obtained by conventional scanning at 120 kilovolt peak, and reconstructed using filtered back projection, MAR, and MBIR. Furthermore, virtual monochromatic images (VMIs) at 70 kilo-electron volts (keV) and 140 keV with/without use of MAR were obtained by dual-energy CT. The extents and mean CT values of the dark bands and the differences in the standard deviations and location parameters of the fine streak artifacts evaluated by the Gumbel method in the images obtained by each of the methods were statistically compared by analyses of variance.Significant reduction of the extent of the dark bands was observed in the images reconstructed using MAR than in those not reconstructed using MAR (all, P < .01). Images obtained by VMI at 70 keV and 140 keV with use of MAR showed significantly increased mean CT values of the dark bands as compared to those obtained by reconstructions without use of MAR (all, <.01). Significant reduction of the difference in the standard deviations used to evaluate fine streak artifacts was observed in each of the image sets obtained with VMI at 140 keV with/without MAR and conventional CT with MBIR as compared to the images obtained using other methods (all, P < .05), except between VMI at 140 keV without MAR and conventional CT with MAR. The location parameter to evaluate fine streak artifacts was significantly reduced in CT images obtained using MBIR and in images obtained by VMI at 140 keV with/without MAR as compared to those obtained using other reconstruction methods (all, P < .01).In our present study, MAR appeared to be the most effective reconstruction method for reducing dark bands in CT images, and MBIR and VMI at 140 keV appeared to the most effective for reducing streak artifacts.     

High-Pitch Coronary CT Angiography at 70 kVp With Low Contrast Medium Volume: Comparison of 80 and 100 kVp High-Pitch Protocols

The purpose of this article is to evaluate image quality and radiation dose of prospectively electrocardiogram (ECG)-triggered high-pitch coronary computed tomography angiography (CCTA) at 70 kVp and 30 mL contrast medium.One hundred fifty patients with a heart rate ≤70 beats per minute (bpm) underwent CCTA using a second-generation dual-source computed tomography (CT) scanner and were randomized into 3 groups according to tube voltage and contrast medium volume (370 mg/mL iodine concentration) (100 kVp group, 100 kVp/60 mL, n = 55; 80 kVp group, 80 kVp/60 mL, n = 44; 70 kVp group, 70 kVp/30 mL, n = 51). Objective and subjective image quality along with the effect of heart rate (HR) and body mass index (BMI) was evaluated and compared between the groups. Radiation dose was estimated for each patient.CT attenuation and image noise were higher in the 80 and 70 kVp groups than in the 100 kVp group (all P < 0.001). Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were lower in the 70 kVp group than in the 80 and 100 kVp groups (all P < 0.05). There was no difference for subjective image quality between the groups (P > 0.05). HR did not affect subjective image quality (all P > 0.05), while patients with BMI <23 kg/m² had higher image quality than patients with BMI ≥23 kg/m² (P < 0.05). Compared with the 100 kVp group, the radiation dose of the 70 kVp group was reduced by 75%.In conclusion, prospectively ECG-triggered high-pitch 70 kVp/30 mL CCTA can obtain diagnostic image quality with lower radiation dose in selected patients with BMI <23 kg/m² compared with 80/100 kVp/60 mL CCTA.     

Accuracy and safety of high pitch computed tomography imaging in young children with complex congenital heart disease

Multidetector computed tomographic angiography defines anatomy in complex congenital heart disease, but radiation exposure and general anesthesia requirements limit its application. The aim of this study was to compare radiation exposure, anesthesia use, and diagnostic accuracy between standard-pitch, single-source computed tomography and high-pitch, dual-source computed tomography for image quality and risk in a clinical pediatric population. Consecutive computed tomographic scans were evaluated in patients aged <2 years with complex congenital heart disease. Two groups were compared on the basis of standard- versus high-pitch scans. High-pitch scans were further divided into variable pitch (2.25 to 3.0) and highest pitch (3.4) groups. Image quality, radiation exposure, anesthesia use, and diagnostic confidence and accuracy were determined. Sixty-one scans were reviewed (29 at standard pitch, 32 at high pitch). Body surface area, scan length, and indications were similar. The median dose-length product for standard-pitch scans was 66 mGy · cm (range 29 to 372) compared to 7 mGy · cm (range 3 to 50) in all high-pitch scans. The median dose-length product was 28 mGy · cm (range 8 to 50) for variable high-pitch scans and 5 mGy · cm (range 3 to 12) for the highest fixed-pitch scans. Diagnostic confidence was similar, although high-pitch scans had higher image noise and lower contrast-to-noise ratios. All high-pitch scans were performed under sedation with free breathing, and all standard-pitch scans required general anesthesia. Diagnostic accuracy was 100% in the 2 groups, with 17 standard-pitch and 16 high-pitch patients undergoing procedural validation. In conclusion, high-pitch, dual-source computed tomography provides excellent diagnostic accuracy and markedly reduces radiation dose, although image quality is mildly reduced.     

Monochromatic energy computed tomography image for active intestinal hemorrhage:A model investigation

AIM: To investigate the value of computed tomography(CT) spectral imaging in the evaluation of intestinal hemorrhage.METHODS: Seven blood flow rates were simulated in vitro.Energy spectral CT and mixed-energy CT scanswere performed for each rate(0.5,0.4,0.3,0.2,0.1,0.05 and 0.025 m L/min).The detection rates and the contrast-to-noise ratios(CNRs) of the contrast agent extravasation regions were compared between the two scanning methods in the arterial phase(AP) and the portal venous phase(PVP).Comparisons of the CNR values between the PVP and the AP were made for each energy level and carried out using a completely random t test.A χ2 test was used to compare the detection rates obtained from the two scanning methods.RESULTS: The total detection rates for energy spectral CT and mixed-energy CT in the AP were 88.57%(31/35) and 65.71%(23/35),respectively,and the difference was significant(χ2 = 5.185,P = 0.023); the total detection rates in the PVP were 100.00%(35/35) and 91.4%(32/35),respectively,and the difference was not significant(χ2 = 1.393,P = 0.238).In the AP,the CNR of the contrast agent extravasation regions was 3.58 ± 2.09 on the mixed-energy CT images,but the CNRs were 8.78 ± 7.21 and 8.83 ± 6.75 at 50 and 60 keV,respectively,on the single-energy CT images,which were significantly different(3.58 ± 2.09 vs 8.78 ± 7.21,P = 0.031; 3.58 ± 2.09 vs 8.83 ± 6.75,P = 0.029).In the PVP,the differences between the CNRs at 40,50 and 60 keV different monochromatic energy levels and the polychromatic energy images were significant(19.35 ± 10.89 vs 11.68 ± 6.38,P = 0.010; 20.82 ± 11.26 vs 11.68 ± 6.38,P = 0.001; 20.63 ± 10.07 vs 11.68 ± 6.38,P = 0.001).The CNRs at the different energy levels in the AP and the PVP were significantly different(t =-2.415,-2.380,-2.575,-2.762,-2.945,-3.157,-3.996 and-3.189).CONCLUSION: Monochromatic energy imaging spectral CT is superior to polychromatic energy images for the detection of intestinal hemorrhage,and the detection was easier in the PVP compared with the AP.