全模型迭代重建在头颈部CT血管成像中的应用

全模型迭代重建（IMR）在重建过程中建立图像统计模型和数据统计模型,通过反复进行扫描模型与采集数据之间的差异对比校正,实现影像最优化。头颈部CT血管成像采用IMR技术能显著降低影像噪声、提高影像信噪比和对比噪声比,可增强对脑动脉硬化和动脉瘤的诊断信心;还能提高对早期缺血性卒中动脉致密征检出的敏感度、大幅降低CT灌注的辐射剂量、减少CT血管成像对比剂用量以及降低病人的碘负荷。综述IMR技术在头颈部CT血管成像中的应用进展。     

低kV结合迭代重建在下肢动脉CT血管造影中的应用

目的 探讨低管电压联合自适应性迭代低剂量(AIDR-3D)技术在下肢动脉CT血管造影(CTA)应用的可行性。方法 60例疑诊下肢动脉闭塞的患者按随机数字表法分为对照组(120 kV)和试验组(100 kV)各30例,采用Toshiba Aquilion ONE完成CTA。对照组采用传统滤波反投射法(FBP)进行重建,试验组采用FBP和AIDR-3D两种重建。分别比较两组的主观图像质量及血管内密度(VD)、噪声、信噪比(SNR)、对比信噪比(CNR)和剂量长度乘积(DLP)。结果 试验组DLP较对照组明显减低[(503.5±104.7)vs. (1099.4±151.7) mGy·cm,t=15.7,P<0.05]。FBP重建的试验组图像的VD和噪声明显高于对照组(t=-3.13、-3.61,P<0.05)。AIDR-3D重建的图像噪声明显低于FBP重建图像(t=13.59,P<0.05)。与对照组相比, AIDR-3D重建的试验组图像噪声明显减低(t=2.14,P<0.05),而VD、SNR和CNR明显增高(t=-3.75、-4.19、-4.15,P<0.05)。结论 在320排CT下肢动脉CTA检查中,100 kV联合AIDR-3D重建可提高图像质量,并大幅减低辐射剂量。临床试验注册 中国临床试验注册中心,CHiCTR-DPD-16008054。     

低管电压联合迭代重建算法对胸部CT血管造影图像质量及辐射剂量的影响

目的 探讨低管电压联合迭代重建算法对胸部CT血管造影成像图像质量及辐射剂量的影响.方法 利用ATOM 701-D型成年男性仿真人胸部模型,配置碘水混合对比剂注入输液管后置入胸部模拟胸部血管.采用320排容积CT以80、100和120 kV分别联合自适应迭代降剂量技术(AIDR 3D)迭代重建4个等级(关闭、轻、标准、强)共12种方案按管电流等其他参数不变进行胸部扫描,记录辐射剂量.获得横断面输液管CT值及噪声水平、纵隔区软组织CT值、信噪比(SNR)和对比噪声比(CNR).比较不同管电压扫描及不同迭代算法水平重建对图像质量的影响.结果 容积CT剂量指数(CTDI_vol)、剂量长度乘积(DLP)及有效剂量(E)在120 kV时为12.50 mGy、453.50 mGy ·cm、6.35 mSv;在100 kV时为7.60 mGy、276.50 mGy ·cm、3.87 mSv;在80 kV时为3.80 mGy、138.70 mGy ·cm、1.94 mSv.随着管电压的降低,辐射剂量显著降低.不同管电压时,输液管CT值、噪声标准差(SD)、SNR、CNR差异均具有统计学意义(F=1 029.24、8.56、3.44、4.09,P<0.05).按不同重建算法,输液管SD、SNR、CNR差异均具有统计学意义(F=33.99、54.80、54.72,P<0.05),但对输液管CT值没有显著影响(P>0.05).管电压或重建算法对纵隔区软组织CT值的影响差异均无统计学意义(P>0.05).结论 80 kV管电压扫描联合标准水平的迭代重建算法方案可降低有效剂量,并获得较高质量的胸部血管图像.     

256 CT低管电压联合迭代重组技术在头颈部CT血管成像中的应用

目的 探讨低管电压(80 kV)联合迭代重组技术在头颈部CT血管成像(CTA)扫描中对图像质量、辐射剂量的影响.方法 将75例临床需要行头颈部CTA检查的患者随机编入A、B、C三组,每组25例.A组为常规剂量扫描,参数为120 kV、300 mAs,经滤波反投影(FBP)重组;B、C组为低剂量扫描,管电流和管电压分别为120kV、180 mAs,80 kV、180 mAs,采用iDose4迭代重组.对比分析CT图像质量,包括动脉强化值、对比噪声比(CNR)、图像质量评分及辐射剂量.计量资料采用配对t检验两两比较,图像质量评分采用非参数x2检验进行统计分析.结果 (1)图像质量主观评分:A组3分1例,4分24例;B组3分2例,4分23例;C组3分5例,4分20例;统计学分析无差异(P＞0.05).(2)A、B两组主动脉弓、颈总动脉、颈内动脉及大脑中动脉的动脉强化CT值统计无明显差异(P＞0.05);C组的CT动脉强化值高于A组(P＜0.05).(3)C组的背景噪声[(12.5±1.9)HU]高于A组[(9.0±1.6)HU](P＜0.05);两组的CNR分别为(49.2±9.4)、(43.0±12.6),无统计学差异(P＞0.05).(4)A、B、C组的剂量长度乘积(DLP)分别为(925.1±48.5)、(571.4±24.2)、(164.1±7.0)mGy·cm;辐射有效剂量(ED)分别为(2.87±0.15)、(1.77±0.08)、(0.51±0.02) mSv,均有统计学意义(P＜0.05),C组较A组辐射剂量明显降低,约82.3％.结论 256 CT头颈部CTA采用低管电压(80 kV)联合迭代重组技术能提供满足临床诊断要求的图像,同时明显降低辐射剂量.     

低管电流联合多模型迭代重建技术对腰椎定量CT准确度的应用价值

目的 通过模型研究,探讨低mA联合多模型迭代重建对腰椎骨密度（BMD）准确度的可行性。方法 应用GE Revolution原型机,在5种不同的剂量水平（管电压120 kV,管电流40、60、80、100和120 mA）,对欧洲腰椎体模（ESP）进行扫描,并分别进行多模型数据迭代重建（ASiR-V）（权重0、20%、40%、60%、80%和100%）。分别在L1、L2和L3正中间置感兴趣区（ROI）,测量其CT值、噪声,并计算其对比噪声比（CNR）。采用单因素方差分析比较在不同剂量水平和不同迭代权重比例条件下的骨密度值。结果 容积CT剂量指数（CTDI_vol）和剂量长度乘积（DLP）与管电流呈正相关关系（r=1）。在不同辐射剂量、同一迭代权重下,ESP （L1,L2和L3）的BMD差异均无统计学意义（P>0.05）;在相同辐射剂量、不同的迭代权重条件下,ESP （L1,L2和L3）的BMD差异均无统计学意义（P>0.05）。腰椎BMD准确度误差均在6%以内。结论 ESP腰椎BMD进行重复性测量,120 kV、40 mA低剂量条件下,不影响BMD准确度,实现腰椎定量CT （QCT）的准确测量,并显著降低辐射剂量;同时,可以适当增加ASiR-V权重比例,降低图像噪声,提高图像质量。     

联合应用低管电压和迭代重建进行腹部CT血管成像的研究

目的 探讨低管电压联合迭代重建(IR)在腹部CTA应用中的可行性及价值.方法 选择因怀疑腹部血管性疾病行腹部CTA检查的50例患者,随机分为年龄、体重指数相匹配的A、B两组.A组采用100 kV、IR和滤波反投影(FBP)重建,B组采用120 kV、FBP重建.分别测量A组IR、FBP重建及B组FBP重建的平膈肌下缘水平腹主动脉、左肾动脉开口处和腹主动脉分叉处血管CT值及图像噪声,并计算相应的信噪比(SNR)和对比噪声比(CNR).分析两组的有效辐射剂量(ED)、A组IR与FBP重建及A组IR与B组FBP重建的CT值、图像噪声、SNR、CNR和图像质量是否有统计学差异.结果 A组IR的图像噪声显著低于FBP重建(P＜0.01),SNR和CNR显著高于FBP重建(P＜0.01),CT值及图像质量差异均无统计学意义(P＞0.05).A组IR的CT值、SNR和CNR均显著高于B组FBP重建(P＜0.01),两者的图像噪声和图像质量差异均无统计学意义(P＞0.05);与B组FBP重建相比,A组IR的ED降低40.70％.结论 低管电压IR用于腹部CTA能够提供较高质量图像且辐射剂量降低.     

胸主动脉CT血管造影自适应性统计迭代重建权重和低剂量扫描条件的优化

目的 探讨胸主动脉CT血管造影(CTA)成像时的适应性统计迭代重建(ASIR)的最佳权重和优化低剂量扫描参数.方法 将体质量指数为19~24 kg/m²的120例患者随机数字表法分成6组,用宝石能谱CT进行胸主动脉CTA扫描,扫描范围为290~330 mm,第1组扫描条件为机器默认的100 kV、240 mAs,使用10%~100%权重的适应性统计迭代重建,对图像进行重建并计算信噪比(SNR)及对比度噪声比(CNR),请两位影像学家对图像进行5分值主观评价,优选出最佳图像质量的ASIR权重,在此权重基础上固定100 kV,用210、180、 150、120 及90 mAs对其他5组患者进行扫描,记录不同mAs的CTDI_vol及DLP,并转换为有效剂量E.计算上述图像的SNR及CNR,并进行主观评价.结果 100 kV、240 mAs 扫描条件下图像的最佳ASIR权重为60%.ASIR权重为60%、100 kV下240~90 mAs扫描产生图像进行主观评价分值分别为(4.78±0.30)~(3.15±0.23);其CTDI_vol、DLP平均值分别为: 12.64~4.41 mGy和331.81~128.27 mGy,并将DLP转换为E为4.98~1.92 mSv.120~240 mAs各组的影像质量差异无统计学意义(F＝5.365,P>0.05),但120 mAs的CTDI_vol、DLP及E较240 mAs分别低53.4%、48.5%及49.9%. 结论 在进行胸主动脉低剂量CTA成像时最佳的ASIR权重为60%.体质量指数为19~24 kg/m²的被检者胸主动脉低剂量CTA扫描的最佳mAs 为120 mAs (100 kV时).     

“三低”技术联合全模型迭代重建算法在头颈部CT血管成像中的可行性研究

目的探讨80 kV低管电压、低对比剂注射速率和低对比剂用量的“三低”技术,联合全模型迭代重建（IMR）算法在头颈部CT血管成像（CTA）检查的可行性。方法前瞻性连续收集2015年7-11月行头颈部CTA检查的患者60例,采用随机数字表法将其分为A、B两组,每组各30例。A组为常规剂量组,管电压120 kV,滤过反投影（FBP）重建,对比剂注射速率4.5~5.5 ml/s,注射时间10 s;B组为80 kV低管电压组,分别使用FBP和IMR进行图像重建,得到B1和B2两组图像,对比剂注射速率3.5~4.0 ml/s,注射时间10 s。测量并计算A组、B1组、B2组的图像动脉血管CT值、图像噪声、信噪比（SNR）和对比噪声比（CNR）,并由2名放射诊断医师对图像质量按照5分法进行评价。3组图像间动脉血管CT值、图像噪声、SNR和CNR采用单因素方差分析,图像质量主观评价采用Kruskal-Wallis检验,两组检查的容积CT剂量指数（CTDI_vol）和剂量长度乘积（DLP）比较采用两个独立样本t检验。结果 A、B1和B2组3组图像质量主观评分范围分别为3~5分、2~4分和3~5分,B1组有12例患者图像之间评分≤2分,图像无法诊断。A和B1、A和B2、B1和B2图像之间评分差异均有统计学意义（t=4.55、-6.58、-2.03,P<0.05）。B2组与A组的图像客观指标SNR和CNR比较差异无统计学意义（P>0.05）,但B2和A组图像的SNR、CNR均优于B1组,差异均有统计学意义（t=-12.14、13.39、-9.96、9.45,P<0.05）。B组CTDI_vol[（1.7±0.2）mGy]比A组[（8.9±1.0）mGy]减少了80.9%,DLP[（77.9±9.0）mGy·cm]比A组[（415.5±56.7）mGy·cm]减少了81.3%,B组对比剂注射速率[（3.9±0.1）ml/s]比A组[（5.0±0.2）ml/s]减少了22.0%,B组对比剂总量[（39.2±1.9）ml]比A组[（50.3±2.2）ml]减少22.1%,差异有统计学意义（t=39.1、32.2、20.8、20.8,P<0.05）。结论使用80 kV管电压、低对比剂注射速率和用量,并使用IMR算法进行图像重建,进行头颈部CTA扫描是可行的。可以在保证图像质量的基础上,使患者辐射剂量减少81.3%。临床试验注册号中国临床试验注册中心,ChiCTR-BOC-16010060。     

不同前置和后置自适应统计迭代重建算法权重在冠状动脉CT血管成像中的研究

目的 探讨不同前置和后置自适应统计迭代重建算法(ASiR-V)水平在冠状动脉CT血管成像(CCTA)中图像质量和辐射剂量的比较研究.方法 前瞻性将150例行CCTA检查患者随机分为A、B、C、D、E 5组并采用前置40％、50％、60％、70％、80％ASiR-V权重和后置70％ASiR-V权重进行扫描,计算所有图像的...     

电子束CT血管造影评价颈动脉狭窄的临床应用

探讨颈动脉电子束ＣＴ血管造影（ＥＢＣＴＡ０的方法并评价其临床价值。材料和方法：使用电子束ＣＴ对５３例病例进行检查。采用Ｉｍａｔｒｏｎ Ｃ－１５０型电子束ＣＴ扫描设备,以２￣４ｍｌ／ｓ前臂静脉注射８０￣９０ｍｌ ０ｍｎｉ￣ｐａｑｕｅ ３００,延迟２０￣３０ｓ后进行连续容积扫描,层厚１．５￣３ｍｍ。将电子束ＣＴ图像转入工作站处理。采用最大密度投影（ＭＩＰ）、表面遮盖显示（ＳＳＤ）、容积再现（ｖｏｕｍｅ     

Noise-based tube current reduction method with iterative reconstruction for reduction of radiation exposure in coronary CT angiography

Purpose

To investigate the potential of noise-based tube current reduction method with iterative reconstruction to reduce radiation exposure while achieving consistent image quality in coronary CT angiography (CCTA).

Materials and methods

294 patients underwent CCTA on a 64-detector row CT equipped with iterative reconstruction. 102 patients with fixed tube current were assigned to Group 1, which was used to establish noise-based tube current modulation formulas, where tube current was modulated by the noise of test bolus image. 192 patients with noise-based tube current were randomly assigned to Group 2 and Group 3. Filtered back projection was applied for Group 2 and iterative reconstruction for Group 3. Qualitative image quality was assessed with a 5 point score. Image noise, signal intensity, volume CT dose index, and dose-length product were measured.

Results

The noise-based tube current modulation formulas were established through regression analysis using image noise measurements in Group 1. Image noise was precisely maintained at the target value of 35.00 HU with small interquartile ranges for Group 2 (34.17–35.08 HU) and Group 3 (34.34–35.03 HU), while it was from 28.41 to 36.49 HU for Group 1. All images in the three groups were acceptable for diagnosis. A relative 14% and 41% reduction in effective dose for Group 2 and Group 3 were observed compared with Group 1.

Conclusion

Adequate image quality could be maintained at a desired and consistent noise level with overall 14% dose reduction using noise-based tube current reduction method. The use of iterative reconstruction further achieved approximately 40% reduction in effective dose.     

Image quality and radiation dose of low dose coronary CT angiography in obese patients: Sinogram affirmed iterative reconstruction versus filtered back projection

Purpose

To investigate the image quality and radiation dose of low radiation dose CT coronary angiography (CTCA) using sinogram affirmed iterative reconstruction (SAFIRE) compared with standard dose CTCA using filtered back-projection (FBP) in obese patients.

Materials and methods

Seventy-eight consecutive obese patients were randomized into two groups and scanned using a prospectively ECG-triggered step-and-shot (SAS) CTCA protocol on a dual-source CT scanner. Thirty-nine patients (protocol A) were examined using a routine radiation dose protocol at 120 kV and images were reconstructed with FBP (protocol A). Thirty-nine patients (protocol B) were examined using a low dose protocol at 100 kV and images were reconstructed with SAFIRE. Two blinded observers independently assessed the image quality of each coronary segment using a 4-point scale (1 = non-diagnostic, 4 = excellent) and measured the objective parameters image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Radiation dose was calculated.

Results

The coronary artery image quality scores, image noise, SNR and CNR were not significantly different between protocols A and B (all p > 0.05), with image quality scores of 3.51 ± 0.70 versus 3.55 ± 0.47, respectively. The effective radiation dose was significantly lower in protocol B (4.41 ± 0.83 mSv) than that in protocol A (8.83 ± 1.74 mSv, p < 0.01).

Conclusion

Compared with standard dose CTCA using FBP, low dose CTCA using SAFIRE can maintain diagnostic image quality with 50% reduction of radiation dose.     

低浓度对比剂、低管电压结合迭代重建在CT冠状动脉成像检查中的临床价值

目的评价低k V、低浓度对比剂结合使用迭代重建CT冠状动脉成像(CTCA)的影像质量和辐射剂量。方法符合纳入标准的CTCA受检者共90例,男52例,女38例;年龄30~85岁,平均年龄(56.72±14.51)岁。将其随机分为A、B、C共3组,每组各30例。分别给予不同碘浓度的对比剂:A组270 mg I/m L、B组350 mg I/m L、C组370 mg I/m L。A组管电压100 k V,B、C组管电压120 k V,3组管电流为200~250 m As。采用4分法主观评价影像质量;测量左、右冠状动脉开口、升主动脉根部的CT值,计算影像的信噪比(SNR)、对比噪声比(CNR)来客观评价影像质量。同时记录受检者的CT剂量指数、剂量长度乘积(DLP)、对比剂注射的容量和浓度,分别计算受检者辐射剂量和碘用量。3组受检者年龄、DLP、有效剂量(ED)、信号强度、噪声、SNR和CNR的差异采用方差分析进行比较,组间进一步两两比较采用LSD-t检验。性别、影像质量的主观评分采用χ~2检验。结果 3组受检者的性别、年龄、身高、体质量、BMI差异均无统计学意义(P0.05)。3组受检者冠状动脉段显示质量达诊断需求者有1 210段(98.94%)。3组之间在冠状动脉各段显示质量上差异无统计学意义(χ~2=4.56,P=0.325)。3组中左、右冠状动脉及升主动脉根部的CT值、SNR、CNR差异均无统计学意义(均P0.05)。A组DLP、ED和碘总量均低于B、C组(P0.05),相对于B组分别降低了约27.58%、27.58%、21.27%,相对于C组分别降低了约28.21%、28.21%、24.83%。结论低k V、低浓度对比剂结合迭代重建进行CTCA成像,能获得与常规CTCA一致的影像质量,同时明显地降低受检者的辐射剂量和注射的碘总量。     

Improved image quality and low radiation dose with hybrid iterative reconstruction with 80 kV CT pulmonary angiography

Objectives

To determine the impact of hybrid iterative reconstruction (HIR) on image quality in 80 kV CT pulmonary angiography (CTPA) in comparison to filtered-back-projection (FBP).

Methods

Fifty patients (body weight <80 kg) with suspected pulmonary embolism (PE) underwent CTPA at 80 kV (mean CTDIvol, 2.3 mGy; effective dose, 1.2 mSv). The raw data were reconstructed using FBP and three increasing HIR levels. Two radiologists assessed image quality and image noise. Conspicuity of PE was assessed in central, segmental, and subsegmental arteries. CT attenuation of pulmonary arteries, objective image noise (OIN) and contrast-to-noise ratios (CNR) were assessed.

Results

With each HIR level, a significant decrease in subjective and objective image noise was achieved with a reduction of OIN up to 46% in comparison with FBP. CNR significantly increased with the application of HIR compared to FBP. Image quality was rated significantly higher at HIR reconstructions in comparison with FBP. Diagnosis of PE was feasible with each data set; however, conspicuity of central and segmental PE significantly improved with the use of HIR.

Conclusions

Eighty kilovoltage CTPA with HIR provides improved image quality and conspicuity of pulmonary embolism enabling low dose CTPA protocols close to 1 mSv in patients weighing less than 80 kg.     

Value of knowledge-based iterative model reconstruction in low-kV 256-slice coronary CT angiography

BackgroundMost current iterative reconstruction algorithms for CT imaging are a mixture of iterative reconstruction and filtered back projection. The value of “fully” iterative reconstruction in coronary CT angiography remains poorly understood.ObjectiveWe aimed to assess the value of the knowledge-based iterative model reconstruction (IMR) algorithm on the qualitative and quantitative image quality at 256-slice cardiac CT.MethodsWe enrolled 21 patients (mean age: 69 ± 11 years) who underwent retrospectively ECG gated coronary CT anhgiography at 100 kVp tube voltage. Images were reconstructed with the filtered back projection (FBP), hybrid iterative reconstruction (IR), and IMR algorithms. CT attenuation and the contrast-to-noise ratio (CNR) of the coronary arteries were calculated. With the use of a 4-point scale, 2 reviewers visually evaluated the coronary arteries and cardiac structures.ResultsThe mean CT attenuation of the proximal coronary arteries was 369.3 ± 73.6 HU, 363.9 ± 75.3 HU, and 363.3 ± 74.5 HU, respectively, for FBP, hybrid IR, and IMR and was not significantly different. The image noise of the proximal coronary arteries was significantly lower with IMR (11.3 ± 2.8 HU) than FBP (51.9 ± 12.9 HU) and hybrid IR (23.2 ± 5.2 HU). The mean CNR of the proximal coronary arteries was 9.4 ± 2.4, 20.2 ± 4.7, and 41.8 ± 9.5 with FBP, hybrid IR and IMR, respectively; it was significantly higher with IMR. The best subjective image quality for coronary vessels was obtained with IMR (proximal vessels: FBP, 2.6 ± 0.5; hybrid IR, 3.4 ± 0.5; IMR, 3.8 ± 0.4; distal vessels: FBP, 2.3 ± 0.5; hybrid IR. 3.1 ± 0.5; IMR, 3.7 ± 0.5). IMR also yielded the best visualization for cardiac systems, that is myocardium and heart valves.ConclusionThe novel knowledge-based IMR algorithm yields significantly improved CNR and better subjective image quality of coronary vessels and cardiac systems with reliable CT number measurements for cardiac CT imaging.     

迭代重建算法在双源CT三低方案冠状动脉血管成像中的应用价值

目的 探讨迭代重建（SAFIRE）算法在双源CT三低方案（低管电压、低剂量对比剂、低流速注射）冠状动脉血管造影（CCTA）中的应用价值。方法 连续选取120例体质量指数（BMI）18.6~24.9 kg/m² 和心率<65次/min的患者,均使用对比剂碘海醇350 mgI/ml,其中包括滤波反投影技术（FBP）组和SAFIRE组,每组60例。FBP组采用120 kV管电压、对比剂剂量0.9 ml/kg、注射流速5.0 ml/s,进行前瞻性心电门控扫描,图像重建采用FBP;SAFIRE组采用80 kV管电压、对比剂剂量0.7 ml/kg、注射速率3.5 ml/s,进行前瞻性心电门控大螺距扫描,图像重建采用SAFIRE。测量两组动脉管腔内及左心室底部肌肉的CT强化值和噪声,计算信噪比（SNR）及对比噪声比（CNR）。采用双盲法对冠状动脉节段以4分法进行评价,其中1分为不可诊断图像。记录每一个患者的平均容积CT剂量指数（CTDI_vol）和剂量长度乘积（DLP）,并计算有效剂量。结果 两组动脉管腔内CT值、图像噪声、SNR、CNR,差异均无统计学意义（P>0.05）;SAFIRE组有效剂量（0.39±0.02）mSv较FBP组显著降低（4.99±1.36）mSv,差异有统计学意义（t=26.31,P<0.05）。结论 在BMI为18.6~24.9 kg/m ²、心率<65次/min的患者中,应用双源CT前瞻性心电触发大螺距三低方案联合迭代重建算法冠状动脉血管成像,能得到满意的图像,又降低了辐射剂量。     

Iterative model reconstruction: Improved image quality of low-tube-voltage prospective ECG-gated coronary CT angiography images at 256-slice CT

Objectives

To investigate the effects of a new model-based type of iterative reconstruction (M-IR) technique, the iterative model reconstruction, on image quality of prospectively gated coronary CT angiography (CTA) acquired at low-tube-voltage.

Methods

Thirty patients (16 men, 14 women; mean age 52.2 ± 13.2 years) underwent coronary CTA at 100-kVp on a 256-slice CT. Paired image sets were created using 3 types of reconstruction, i.e. filtered back projection (FBP), a hybrid type of iterative reconstruction (H-IR), and M-IR. Quantitative parameters including CT-attenuation, image noise, and contrast-to-noise ratio (CNR) were measured. The visual image quality, i.e. graininess, beam-hardening, vessel sharpness, and overall image quality, was scored on a 5-point scale. Lastly, coronary artery segments were evaluated using a 4-point scale to investigate the assessability of each segment.

Results

There was no significant difference in coronary arterial CT attenuation among the 3 reconstruction methods. The mean image noise of FBP, H-IR, and M-IR images was 29.3 ± 9.6, 19.3 ± 6.9, and 12.9 ± 3.3 HU, respectively, there were significant differences for all comparison combinations among the 3 methods (p < 0.01). The CNR of M-IR was significantly better than of FBP and H-IR images (13.5 ± 5.0 [FBP], 20.9 ± 8.9 [H-IR] and 39.3 ± 13.9 [M-IR]; p < 0.01). The visual scores were significantly higher for M-IR than the other images (p < 0.01), and 95.3% of the coronary segments imaged with M-IR were of assessable quality compared with 76.7% of FBP- and 86.9% of H-IR images.

Conclusions

M-IR can provide significantly improved qualitative and quantitative image quality in prospectively gated coronary CTA using a low-tube-voltage.