16层螺旋CT低剂量与常规剂量扫描的对照研究

目的通过对16层螺旋CT肺部低量与常规剂量扫描的对比分析，肺部低剂量检查的临床应用价值及优势。方法分析55例早期肺癌病变并经手术证实的患者，均为采用低剂量扫描体检时发现，短时间内又用常规剂量扫描，低剂量采用（120kV、20Eff．mAs），常规剂量采用（120kV、100Eff．mAs）扫描，对比分析两种扫描方法对病灶影像显示率及影像质量等因素有无差异性。结果低剂量扫描检查对病灶的显示与常规扫描检查均无明显差异，图像质量优良，纵膈窗图像噪声较大，但不影响纵膈内淋巴结及钙化的冠状动脉的显示。低剂量扫描剂量当量（CTDL）仅为常规扫描的20％。结论肺部CT扫描检查可采用低剂进行扫描，其对肺内病灶的显示与常规cT扫描无差别，并且可以明显减少患者的X线辐射剂量。     

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。     

低剂量技术在多排螺旋CT冠状动脉成像中的应用

目的 观察低剂量技术用于多排螺旋CT冠状动脉成像的效果。方法 将90例拟行CT冠状动脉造影（CTA）的患者随机分为A、B、C三组各30例,其中A组采用常规曝光条件（120kV,180mAs）,B组将管电压降至100kV,C组根据BMI设定管电流。观察三组图像信噪比、图像质量评分及有效剂量（ED）。结果 三组图像信噪比、图像质量评分均无显著差异,但ED在B组〈C组〈A组,两两比较P均〈0．05。结论 在冠状动脉CTA检查中适当降低管电压并根据BMI设定管电流,能够在保证图像质量的前提下降低患者所受辐射剂量,其中降低管电压效果尤为明显。     

迭代重建使用100kV管电压扫描对肥胖人群冠状动脉CT血管造影图像的影响

目的:探讨在冠状动脉CT血管造影图像(CCTA)检查中使用迭代重建(iterative reconstruction,IR)技术后,针对肥胖人群使用低管电压(100kV)扫描的可行性。方法:共有180例符合纳入标准的连续性受试者(男性112例)入选本前瞻性研究。受试者年龄43~77岁,平均(56.2±9.5)岁,体质量指数(BMI)范围:30~35 kg/m2。采用飞利浦公司256层螺旋CT扫描(Brilliance iCT,Philips Healthcare),回顾心电门控螺旋扫描模式及心电图相关管电流调节模式联合应用。按扫描方案分为高低管电压组(L组:100kV/800mAs;H组:120kV/800mAs),180例受试者随机分配入组。L组采用迭代重建算法重建图像(Idose4,level 4),H组采用滤波反投影算法(filter back projection,FBP)重建图像。图像主观评价法:使用4分单盲评法(1=不能诊断,4=图像极好)评价图像质量,并比较两观察者一致性。图像客观评价法:比较两组冠状动脉4大主干(左主干、前降支、回旋支及右冠状动脉)管腔内的CT值、感兴趣区噪声、信号噪声比及对比噪声比。结果:两组CNR分别为[(31.5±3.2)vs.(30.3±2.5,P0.05)]。两组图像质量评价均为好。两组图像质量评分差异无统计学意义(P0.05)。低电压100kV方案与高电压120kV方案辐射剂量分别为(4.3±0.6)mSv[CTDIvol:(15.7±0.4)mGy]、(7.6±0.4)mSv,[CTDIvol:(26.3±0.3)mGy](P0.001)。结论:在迭代重建技术辅助下,可在CCTA检查中对肥胖受试者(BMI:30~35 kg/m2)使用100kV管电压扫描,所得图像能够满足临床诊断需要。100kV方案较常规120kV方案辐射剂量明显降低。     

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。     

低管电压扫描联合低剂量造影剂在肺静脉及左心房造影中的价值

目的 探讨用低辐射剂量扫描下减少对比剂用量在肺静脉及左心房造影中的应用。方法 选取2022年2月至2022年4月在解放军第九六〇医院左心房及肺静脉血管造影成像的80例患者,分为对照组(管电压120 kV,造影剂70 mL)和试验组(管电压80 kV,造影剂40 mL),对两组图像质量进行主管测评和客观测评。结果 主观评测:两组图像质量均符合诊断要求,差异无统计学意义。客观评价:对照组扫描方案所测CT值、信噪比、辐射剂量指数、剂量长度乘积、有效剂量和试验组比较,差异均有统计学意义(P <0.05)。结论 用低管电压扫描联合低剂量造影技术在肺静脉及左心房检查中既能保证图像诊断又能有效地降低对比剂用量和辐射剂量。     

自动管电压选择技术在双源CT大螺距心脑一体化血管成像中的应用价值

目的探讨第三代双源CT大螺距心脑一体化血管成像中使用自动管电压选择技术在优化图像质量及降低辐射剂量中的作用。方法选择2019年10月～2020年11月首都医学大学宣武医院神经内科住院行冠状动脉及头颈动脉一体化CT扫描的老年患者100例,随机分为自动管电压组50例,固定管电压组50例。比较2组的一般临床资料、辐射剂量,并对图像质量进行主观及客观评价。结果自动管电压组实际管电流明显高于固定管电压组(P0.01)。自动管电压组剂量长度乘积及有效剂量较固定管电压组明显减低[(121.84±37.17)mGy·cm vs(175.93±18.26)mGy·cm,P0.01;(1.29±0.85)mSv vs(1.89±0.58)mSv,P0.01]。2组冠状动脉主观评分比较,无统计学差异(P0.05)。自动管电压组头颈动脉主观评分明显高于固定管电压组[(3.45±0.66)分vs(3.05±0.72)分,P0.05]。2组各部位图像噪声、信噪比及对比噪声比比较,差异无统计学意义(P0.05)。自动管电压组左冠状动脉主干、右冠状动脉主干、颈总动脉、颈内动脉、大脑中动脉及椎动脉CT值明显高于固定管电压组,差异有统计学意义(P0.01)。结论第三代双源CT大螺距心脑一体化血管成像中使用自动管电压技术可明显降低辐射剂量,并能提供良好的图像质量,值得临床推广应用。     

双源CT 100kV管电压在冠脉成像中的应用价值

目的:探讨双源CT应用100 k V管电压扫描方案在冠状动脉成像中的应用价值。方法:将70例临床怀疑或确诊为冠心病患者,随机分为管电压100 k V组(低剂量组,35例)与120 k V组(常规组,35例)。其他条件一致,分别对两组图像质量和辐射剂量进行评价。入组条件:体质量指数(BMI)为20~24,窦性心率。结果:两组冠脉成像图像质量无显著差别,而100 k V辐射剂量较120 k V组显著降低(P<0.01)。结论:应用双源CT做冠脉CT血管造影,给予100 k V管电压能够在保证图像质量,满足诊断要求同时降低辐射剂量。     

低剂量螺旋CT扫描在早期肺癌诊断中的应用分析

目的 分析低剂量螺旋CT扫描在早期肺癌临床诊断中的应用效果.方法 将我院收治的早期肺癌患者110例分为对照组和试验组,每组55例,对照组采用常规剂量螺旋CT扫描,试验组采用低剂量螺旋CT扫描.结果 试验组最大有效辐射剂量、有效mAs、DLP、CTDIw低于对照组(P<0.05);试验组与对照组图像质量优良率分别为96....     

64排螺旋CT冠状动脉成像中低剂量扫描的最有效方法探讨

目的探究64排螺旋CT冠状动脉成像中低剂量扫描的最有效方法。方法选择2018年1月至2018年12月间于我院行冠脉CT成像的患者共80例,将心率在70次/分以下、心率波动在5次/分以下的体检者共40例作为对照组,应用心电门控回顾性扫描;将心率在70次/分以上或心律不齐的体检者共40例作为观察组,应用心电门控前瞻性扫描。按照患者不同体重指数(BMI)给予不同管电压,对两组图像质量及辐射剂量进行观察。结果两组图像质量无明显差异,P0.05。在120kV管电压下,观察辐射剂量明显较对照少,对照组中,BMI18者选择80kV管电压较120kV的辐射剂量更小,BMI在18～24范围内者选择100kV管电压较120kV的辐射剂量更小,差异显著,P0.05。结论依据患者心律、心率以及BMI等指标制定出合适扫描方案,不仅能获取高质量冠脉CT图像,还能将患者辐射剂量降至最低。     

Comparison of radiation dose and image quality of triple-rule-out computed tomography angiography between conventional helical scanning and a strategy incorporating sequential scanning

Triple-rule-out computed tomographic angiography (TRO CTA), performed to evaluate the coronary arteries, pulmonary arteries, and thoracic aorta, has been associated with high radiation exposure. The use of sequential scanning for coronary computed tomographic angiography reduces the radiation dose. The application of sequential scanning to TRO CTA is much less well defined. We analyzed the radiation dose and image quality from TRO CTA performed at a single outpatient center, comparing the scans from a period during which helical scanning with electrocardiographically controlled tube current modulation was used for all patients (n = 35) and after adoption of a strategy incorporating sequential scanning whenever appropriate (n = 35). Sequential scanning was able to be used for 86% of the cases. The sequential-if-appropriate strategy, compared to the helical-only strategy, was associated with a 61.6% dose decrease (mean dose-length product of 439 mGy × cm vs 1,144 mGy × cm and mean effective dose of 7.5 mSv vs 19.4 mSv, respectively, p <0.0001). Similarly, a 71.5% dose reduction occurred among the 30 patients scanned with the sequential protocol compared to the 40 patients scanned with the helical protocol using either strategy (326 mGy × cm vs 1,141 mGy × cm and 5.5 mSv vs 19.4 mSv, respectively, p <0.0001). Although the image quality did not differ between the strategies, a nonstatistically significant trend was seen toward better quality in the sequential protocol than in the helical protocol. In conclusion, approaching TRO CTA with a diagnostic strategy of sequential scanning, as appropriate, can offer a marked reduction in the radiation dose while maintaining the image quality.     

The potential for reduced radiation dose from deep learning-based CT image reconstruction: A comparison with filtered back projection and hybrid iterative reconstruction using a phantom

The purpose of this phantom study is to compare radiation dose and image quality of abdominal computed tomography (CT) scanned with different tube voltages and tube currents, reconstructed with filtered back projection (FBP), hybrid iterative reconstruction (IR) and deep learning image reconstruction (DLIR) algorithms.A total of 15 CT scans of whole body phantoms were taken with 3 different tube voltages and 5 different tube currents. The images were reconstructed with FBP, 30% and 50% hybrid IR adaptive statistical iterative reconstruction (ASIR-V), and low, medium and high strength DLIR algorithms. The image scanned with tube voltage/tube current of 120 kV/ 200 mA and reconstructed with FBP algorithm was chosen as the reference image. Five radiologists independently analyzed the images individually and also compared it with the reference image in overall, using the visual grading analysis. The mean score of each image was calculated and compared.Using DLIR algorithms, the radiation dose was reduced by 65.5% to 68.1% compared with the dose used in the reference image, while maintaining comparable image quality. Using the DLIR algorithm of medium strength, the image quality was even better than the reference image with a reduced radiation dose up to 36.2% to 50.0%. The DLIR algorithms generated better quality images than ASIR-V algorithms in all the data sets. In addition, among the data sets reconstructed with DLIR algorithms, image quality was the best at the medium strength level, followed by low and high.This phantom study suggests that DLIR algorithms may be considered as a new reconstruction technique by reducing radiation dose while maintaining the image quality of abdominal CTs.     

High diagnostic yield from transbronchial biopsy of solitary pulmonary nodules using low‐dose CT‐guidance

Background and objective: The diagnostic yield from fluoroscopy‐guided bronchoscopic transbronchial biopsy of small solitary pulmonary nodules is low. The hypothesis tested in the present study was that the diagnostic yield can be significantly increased by combining flexible bronchoscopy with CT‐guidance using a dedicated low‐dose protocol. Methods: CT‐guided transbronchial biopsies were performed in 15 patients with a newly diagnosed solitary peripheral pulmonary nodule and negative conventional bronchoscopic biopsies under fluoroscopic guidance. For imaging, a multi‐detector helical CT unit, adjusted at 120 kV, 15 mAs/slice, 4 × 5 mm collimation, 10 mm reconstructed slice thickness and a maximal scan length of 150 mm, was used. After advancing the biopsy forceps towards the lesion, a CT scan was obtained. When the tip of the forceps reached or penetrated the lesion a biopsy was taken, otherwise the procedure was repeated with a maximum of eight attempts. The effective radiation dose was calculated. Results: The average diameter of the nodules was 23 ± 6 mm (mean ± SD) with a maximum distance to the parietal pleura of 18 mm (mean 6.5 mm). A mean of 4.1 (range 2–8) CT scans was performed to localize the lesion. In four patients, the forceps only reached the periphery of the nodule. In one patient, the nodule was missed in all attempts. Histology was malignant in eight patients and benign in four patients. In three patients, biopsy results were false negative (benign or non‐specific instead of malignant). The overall diagnostic yield was 73%. Complications consisted of two pneumothoraces, one of which necessitated a chest tube. Mean effective radiation dose was 0.55 mSv (range 0.3–1.0). Conclusions: CT‐guided transbronchial biopsy can be a valuable diagnostic tool in evaluating solitary pulmonary nodules. This applies for selected patients when other diagnostic methods are either unavailable or inappropriate. The diagnostic yield is high and, when a low‐dose protocol is used, radiation exposure can be kept at a minimum.     

低剂量CT扫描在评价老年菌阴性肺结核患者抗结核治疗效果中的应用

目的 采用低剂量CT扫描对老年菌阴性肺结核患者抗结核治疗效果进行评价.方法 对47例菌阴性肺结核抗结核治疗后1～12个月复查的老年患者采用低剂量CT扫描(120 kV,20 mAs),通过与治疗前常规CT(120 kV,200～280 mAs)扫描影像学结果的比较,对老年菌阴性肺结核患者抗结核治疗效果进行评价.结果 老年菌阴性肺结核患者初诊CT征象最常见的为腺泡实变融合和肺叶/肺段实变,其发生率分别为100.0和76.6%,而空洞的发生率相对较少;1～3个月复查好转的征象主要为树芽征,而腺泡融合实变和肺叶/肺段实变的好转主要发生于4～9个月,空洞性病变显效较慢,持续时间为6～12个月.结论 低剂量CT扫描能较好地反映老年菌阴性肺结核的不同影像学征象及抗结核治疗后的影像学,适合对老年菌阴性肺结核患者治疗后的效果进行评价.

Abstract：

Objective To evaluate the therapeutic effect of antituberculosis therapy in elderly patients with smear-negative pulmonary tuberculosis by low-dose computed tomography (CT).Methods Forty-seven elderly patients diagnosed as smear-negative pulmonary tuberculosis were rechecked with low-dose chest CT scan (120 kV, 20 mAs) after 1-12 months of antituberculous therapy respectively. These images were compared with common CT before treatment (120 kV, 200-280 mAs). Results In the elderly patients with smear-negative pulmonary tuberculosis, the most common CT signs before treatment were acinus consolidation (100%) and lobar or segmental consolidation (77%), but the cavity was seen less. After effective antituberculous therapy, tree-inbud was improved after one to three months, the acinus consolidation and lobular or segmental consolidations were improved after four to nine months, and the cavitations were slowly improved after six months. Conclusions Low-dose CT can provide sufficient information for the therapeutic effects of antituberculous therapy of smear-negative pulmonary tuberculosis in the elderly and could be used for rechecking.     

Reduced radiation for adult thoracic CT: a practical approach

PURPOSE: To determine whether radiation dose to patients can be reduced for clinical thoracic CT scans without loss of diagnostic information. MATERIALS AND METHODS: One hundred consecutive patients having clinical CT examinations of the thorax were included. The patients were divided into 4 groups, and the mAs setting determined from the patient's weight as follows (max. 300 and min. 100 mAs): group 1: mAs = weight in lbs. rounded to the next multiple of 10, plus 30 (mAs = wtR + 30); group 2: mAs = weight rounded to the next multiple of 10 (mAs = wtR); group 3: mAs = weight rounded to the next multiple of 10, minus 20 (mAs = wtR - 20); group 4: mAs = weight rounded to the next multiple of 10, minus 30 (mAs = wtR - 30). The neck, mediastinum, lungs, and upper abdomen were assessed for quality on a 4 point scale. RESULTS: Only at the lowest mAs levels did we see some degradation of image quality in the lower neck with an increase in streak artifacts. The other body regions all showed good or excellent image quality. CONCLUSIONS: Radiation dosage can be reduced by more than half without loss of diagnostic quality, using this simple formula: mAs = weight in lbs. rounded to the next multiple of 10 minus 30 (mAs = wtR - 30).     

Pulmonary sarcoidosis in a 14-year-old boy diagnosed by low-dose CT-guided transthoracic lung biopsy

Pulmonary sarcoidosis is a rare disease in the pediatric age group, characterized by the presence of epitheloid-cell granulomas. In stage 3 sarcoidosis, pulmonary infiltrates without hilar lymphadenopathy occur. Definitive diagnosis requires a histopathological specimen, which might be difficult to obtain by transbronchial biopsy. Multidetector computed tomography (MDCT)-guided transthoracic lung biopsy (TLB) is a well-established procedure in adults, but has only rarely been applied in children.A 14-year-old boy was admitted to hospital for evaluation of a chronic systemic disease with severe pulmonary manifestation. All investigations, including bronchosopy and bronchoalveolar lavage with microbiological and virological testing, had been negative. MDCT-guided TLB was performed on a 16-section scanner with a low-dose protocol (single slices, 120 kV, 20 mAs), using a 16-gauge biopsy device. The total effective dose was 0.4 mSv for the biopsy procedure. Histopathological examination revealed multiple epitheloid-cell granulomas with giant cells in the absence of microbiological or virological abnormalities. A diagnosis of stage 3 pulmonary sarcoidosis was made and systemic anti-inflammatory therapy was administered, which led to complete remission within weeks. MDCT-guided TLB can be a valuable instrument in assessing pulmonary manifestations of pediatric sarcoidosis, enabling precise histopathological diagnosis and adequate therapy. The use of low-dose protocols can substantially reduce radiation exposure without relevant loss of image information. MDCT-guided lung biopsy should be considered prior to open-lung surgery in selected patients with unclear pulmonary disease.     

Low contrast medium and radiation dose for hepatic computed tomography perfusion of rabbit VX2 tumor

AIM:To evaluate the feasibility of low contrast medium and radiation dose for hepatic computed tomography(CT) perfusion of rabbit VX2 tumor.METHODS:Eleven rabbits with hepatic VX2 tumor underwent perfusion CT scanning with a 24-h interval between a conventional tube potential(120 k Vp) protocol with 350 mg I/m L contrast medium and filtered back projection,and a low tube potential(80 k Vp) protocol with 270 mg I/m L contrast medium with iterative reconstruction.Correlation and agreement among perfusion parameters acquired by the conventional and low dose protocols were assessed for the viable tumor component as well as whole tumor.Image noise and tumor-to-liver contrast to noise ratio during arterial and portal venous phases were evaluated.RESULTS:A 38% reduction in contrast medium dose(360.1 ± 13.3 mg I/kg vs 583.5 ± 21.5 mg I/kg,P 0.001) and a 73% decrease in radiation dose(1898.5 m Gy·cm vs 6951.8 m Gy·cm) were observed.Interestingly,there was a strong positive correlation in hepatic arterial perfusion(r = 0.907,P 0.001;r = 0.879,P 0.001),hepatic portal perfusion(r = 0.819,P = 0.002;r = 0.831,P = 0.002),and hepatic blood flow(r = 0.945,P 0.001;r = 0.930,P 0.001) as well as a moderate correlation in hepatic perfusion index(r = 0.736,P = 0.01;r = 0.636,P = 0.035) between the low dose protocol with iterative reconstruction and the conventional protocol for the viable tumor component and the whole tumor.These two imaging protocols provided a moderate but acceptable agreement for perfusion parameters and similar tumorto-liver CNR during arterial and portal venous phases(5.63 ± 2.38 vs 6.16 ± 2.60,P = 0.814;4.60 ± 1.27 vs 5.11 ± 1.74,P = 0.587).CONCLUSION:Compared with the conventional protocol,low contrast medium and radiation dose with iterative reconstruction has no significant influence on hepatic perfusion parameters for rabbits VX2 tumor.     

Effect of a standardized quality-improvement protocol on radiation dose in coronary computed tomographic angiography

Coronary computed tomographic angiography (CCTA) is associated with ionizing radiation, prompting concerns of future cancer risk. Recent studies have reported reduced radiation doses and similar image quality by the selective use of dose reduction techniques, although the clinical penetration of these methods has been limited. In a quality improvement initiative, a comprehensive, standardized radiation dose reduction protocol was implemented, and its effect on radiation dose and image quality was assessed. A total of 449 patients who underwent 64-detector CCTA at 3 centers were prospectively evaluated, and patients were compared before (n = 247) and after (n = 202) the implementation of a standardized body mass index-based and heart rate-based protocol that simultaneously incorporated multiple dose reduction strategies. Median radiation dose decreased from 2.6 mSv (interquartile range 2.0 to 4.2) to 1.3 mSv (interquartile range 0.8 to 1.9) after the implementation of the standardized protocol (p < 0.001). On multivariate analysis, reduction in overall radiation dose was observed by numerous dose reduction techniques, with varying efficacy of dose lowering: prospective (vs retrospective) electrocardiographic gating (-82%), reduced tube voltage (-41% for 100 vs 120 kV), lower tube current (-25% per -100 mA), and reduced overall scan length (-6% per -1 cm) (p < 0.001 for each). No differences were observed between patients before and after the initiation of the protocol for study interpretability (96% vs 96%, p = 0.66). There was an increase in signal-to-noise ratio after implementing the standardized protocol (11 ± 3 vs 12 ± 4, p < 0.01). In conclusion, a quality improvement protocol for CCTA incorporating multiple dose reduction techniques permits significant radiation dose reduction and may improve the safety profile of CCTA.