Application of rational practice and technical advances for optimizing radiation dose for chest CT

Though clinical benefits of CT exceed the adverse effects of radiation, the increasing use of CT has raised a compelling case for reducing radiation exposure. This controversy has been compounded by the sheer magnitude of CT examinations being performed annually, alleged overuse, and inappropriate selection of optimum scanning parameters, all of which expose the patient population to increased radiation exposure. Recommended clinical strategies for radiation dose optimization include optimization of scanning parameters and creating awareness and adopting guidelines for legitimate indications for CT scanning to avoid overuse and hence, the associated over-exposure. Whereas technological advances have increased the applications of the modality, it is also assisting in development of promising techniques to reduce associated radiation exposure, while maintaining "optimum image quality" needed to make a confident diagnosis. The present pictorial essay describes the fundamentals of CT radiation exposure and need for CT radiation dose reduction on the basis of documented scanning practices and technological advances.     

双低剂量结合迭代重建技术在肺动脉CT血管成像中的应用

目的探讨双低剂量结合迭代重建(i Dose4)技术对肺动脉CT血管成像(CTPA)图像质量及辐射剂量的影响。方法前瞻性收集60例行CTPA检查患者,随机分为实验组(100k Vp、i Dose4重建、对比剂碘浓度270 mg I/m L)及对照组(120k Vp、FPB重建、对比剂碘浓度350 mg I/m L)各30例,比较两组患者图像质量、辐射剂量及碘对比剂用量。结果实验组图像主观评分较对照组略高,两组无统计学差异(P0.05);实验组肺动脉各段CT值均高于对照组,两组有统计学差异(P0.05)。实验组CTDIvol、DLP值均低于对照组,差异有统计学意义(P0.05)。实验组患者使用对比剂碘总量较对照组减少约22.9%。结论使用低浓度碘对比剂、低管电压结合i Dose4技术行CTPA检查,可获得较好的图像质量,并显著降低辐射剂量及对比剂用量。     

Minimizing radiation dose for coronary CT angiography

Coronary CT angiography is a rapidly growing technique that offers distinct advantages over traditional imaging techniques. However, because of rapid growth of this technique, radiation dose safety has been placed under the spotlight. There are several main determinants of total radiation dose, and these are outlined in this review. Integration of these dose-saving techniques will go a long way in maintaining diagnostic image quality and improving patient safety.     

双源双能量CT成像在新型冠状病毒肺炎中的应用价值

目的探讨双源双能量计算机体层成像（CT）不同单能量重建对新型冠状病毒肺炎（COVID-19）间质性病灶的显示和图像质量及辐射剂量的影响。 方法回顾性分析2020年1—3月郑州大学第一附属医院收治的20例COVID-19患者的胸部平扫影像学资料。比较同一患者双源双能量CT与常规CT的扫描辐射剂量。同时重建双源双能量CT扫描40、60、80、100、120 keV单能量图像,比较不同单能量图像间质性病灶的CT值和标准差（SD）,计算信噪比（SNR）和对比噪声比（CNR）;由2名经验丰富的肺部诊断医师采用5分法评估不同单能量图像质量,并进行比较。 结果双源双能量CT组的CT容积剂量指数（CTDI_vol）为（6.0±2.4）mGy,较常规CT组的（8.9±2.9）mGy下降了33%,且差异有统计学意义（t=10.694,P<0.001）;双源双能量CT组剂量长度乘积（DLP）和全身有效剂量（ED）分别为（217.5±79.6）mGy·cm和（3.1±1.1）mSv,低于常规CT组的（333.8±109.0）mGy·cm（t=10.727,P<0.001）和（4.67±1.52）mSv（t=10.730,P<0.001）。随着X线能量的升高,单能量图像的SNR和CNR逐渐增加,CT值和SD值逐渐降低,相邻两组间比较差异均有统计学意义（P<0.001）。2名诊断医师的图像质量主观评价一致性较好（Kappa值为0.700~0.857,P<0.001）,不同单能量图像主观评分差异均有统计学意义（P<0.001）,其中80 keV图像主观评分最高。 结论与常规CT相比,使用双源双能量CT降低了辐射剂量;120 keV单能量图像质量客观评价较高,但80 keV单能量图像更有利于间质性病灶的显示,对提示病情进展具有重要意义。     

Thoracic CT technique in children.

Computed tomography (CT) is a powerful tool for imaging the different structures of the child's thorax. Pediatric thoracic CT technique should provide images that allow confident diagnosis at the lowest risk to the patient. New data has increased our understanding of the risk of low-dose radiation. Understanding the technical aspects of CT scanning allows the CT scanner to be optimized for the best combination of image quality and radiation dose. Developments in CT scanning, including multidetector scanners and vascular imaging techniques, are changing the way CT scanning is used. The many imaging options available to the thoracic radiologist require a complex set of decisions when establishing CT protocols and when selecting techniques for different clinical indications. This article presents information on radiation risk and provides an overview of the broad range of factors used when performing pediatric thoracic CT.     

Flash双源CT大螺距冠状动脉成像与冠状动脉造影对比的临床研究

目的评价Flash双源CT大螺距前瞻性心电门控扫描模式（flashspril）诊断冠状动脉狭窄的准确性。方法30例患者行Flash双源CT冠状动脉成像（CTCA）后进行冠状动脉造影术（CCA）检查。以冠状动脉造影术结果作为金标准,统计Flash双源CTCA显示冠脉病变的敏感性、特异性、阳性预测值和阴性预测值,统计冠状动脉各段图像质量评分及有效射线剂量。结果①准确性评价：基于节段水平分析,敏感性93．2％,特异性96．8％,阳性预测值86．0％,阴性预测值98．5％。基于血管水平分析,敏感性97．9％,特异性83．8％,阳性预测值88．7％,阴性预测值96．8％。基于患者水平分析,敏感性、特异性、阳性预测值、阴性预测值均为100％。CTCA显示冠状动脉狭窄结果与CCA高度一致。②图像质量：右冠状动脉不可诊断血管节段占右冠状动脉的3．4％,左冠状动脉主干、前降支不可诊断血管节段为0,回旋支不可诊断血管节段低于1．0％。③射线剂量：平均有效射线剂量（1．72±0．10）mSv。结论Flash双源CTflashspril模式CTCA评价冠状动脉狭窄的准确性高,图像质量好,运动伪影小,有效射线剂量低。     

前瞻性心电触发轴位扫描技术在64层螺旋CT中的应用

目的探讨在64层螺旋CT冠状动脉成像中采用前瞻性心电触发轴位扫描技术的图像质量和辐射剂量。方法选择采用前瞻性心电触发轴位扫描技术进行64层螺旋CT冠状动脉成像的患者160例作为前瞻组。将相同扫描参数输入回顾性心电门控螺旋扫描程序,获得扫描剂量数据作为回顾组。由2名放射科医师分别进行图像重建和图像质量评价。冠状动脉图像质量分级采用4级评分法。结果 2名放射科医师在图像重建和图像质量评价方面均有良好的一致性。160例患者除8例图像有严重血管错层伪影、2例冠状动脉严重钙化,共显示1449个冠状动脉节段。1～3分以上的1431个节段(98.76%)具有较好的图像质量,可以满足临床诊断要求。前瞻组与回顾组的平均有效剂量差异有统计学意义[(3.17±1.17)mSv vs (22.09±6.72)mSv,P0.01]。结论在64层螺旋CT冠状动脉成像中采用前瞻性心电触发轴位扫描技术可在保证图像质量的同时显著降低辐射剂量。     

双源CT不同扫描模式下患者冠脉图像质量评分及接受有效辐射剂量的研究

目的 研究双源CT不同扫描模式下患者冠脉图像质量评分及患者接受的有效辐射剂量.方法 50例患者被纳入研究,男性36例,女性14例,平均年龄（68.2±9.4）岁,心率＜60次/min,心率稳定,BMI为22.5～24.9 kg/m2.所有研究对象均在第1个月的第1天和第15天两次行不同扫描模式双源螺旋CT（DSCT）：A组为100/sn 100 kV,B组为80/sn 120 kV.研究两组的冠脉图像质量及患者接受的有效辐射剂量.结果 A组Ⅰ级图像数量（52％）低于B组（70％）,且差异具有统计学意义（P＜0.01）.B组的图像比A组的图像质量高,但都可以进行诊断.从性别上来看,无论100 kV还是120 kV,高螺距冠脉图像的有效辐射剂量暴露量女性均值高于男性均值,但100 kV的辐射剂量暴露低于120 kV.结论 Flash双源CT（100/sn100kV）在获得满意图像质量的同时可以减低辐射剂量.     

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.     

Patient Dose in Cardiac Computed Tomography

BACKGROUND: Computed tomographic (CT) imaging of the heart is becoming more widely available, and the quality of and interest in these examinations continues to increase. Yet, many physicians who perform or order these exams may be unfamiliar with the radiation doses that are delivered to the patient during specific cardiac CT examinations. OBJECTIVE: The purpose of this article is to describe several fundamental radiation dose quantities that are used to either measure or report the dose associated with a particular CT examination. In addition, radiation dose estimates are given for coronary artery calcium imaging and coronary angiography performed using either electron beam CT (EBCT) or multi-detector row CT (MDCT) systems.     

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。     

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。     

Optimization of radiation dose reduction in cardiac computed tomographic angiography

Cardiac computed tomographic angiography (CCTA) has evolved at an unprecedented pace over the past decade, during which time it has proven to be an accurate and effective tool for imaging of the heart in a growing list of clinical applications. However, the rapid growth in the use of CT imaging in general has prompted appropriate concerns regarding increasing medical radiation exposure to patients, particularly with regard to potential long-term risks of radiation-induced malignancy on both individual and population levels. As with all medical imaging modalities, imaging the heart with CCTA should be performed in a manner that achieves diagnostic image quality while maintaining patient radiation exposure as low as reasonably achievable (As Low As Reasonably Achievable [ALARA] principle). The goal of this article is to provide the reader with a wide-ranging review of both primary and secondary techniques that are currently available to minimize patient radiation exposure. Some of the techniques described in this article are universal, whereas others may be scanner specific. By gaining a thorough understanding of the various tools and methodologies employed for reduction of radiation exposure, the cardiac imager should be able to formulate CCTA protocols appropriate for their equipment and their clinical applications, in a manner that optimally preserves diagnostic image quality and minimizes patient radiation dose.     

冠状动脉CTA双低技术的临床应用

目的探讨应用双低技术——低千伏(100 kV)技术联合低对比剂浓度在冠状动脉CT血管造影(CCTA)中的可行性。方法选取拟行冠状动脉CTA检查患者80例患者(体重指数≤26.0 kg/m2),随机分为A、B两组,A组(n=40)采用100kV,270 mg/ml威视派克对比剂及自适应迭代算法重建(ASiR),B组(n=40)采用120 kV,350 mg/ml欧乃派克对比剂及滤波反投影算法重建(FBP)。测量主动脉、皮下脂肪和竖脊肌的CT值和SD值,平均SD值计算为图像噪声。测量左冠状动脉前降支(LAD),左冠状动脉回旋支(LCX)和右冠状动脉(RCA)的CT值和SD值,并计算对比噪声比(CNR)。采用5分法对所有图像进行主观质量评分。记录CT剂量指数,并进行有效辐射剂量计算。结果A组患者平均碘用量比B组患者下降22.8%。两组患者LAD、LCX和RCA血管CT值、CNR值、图像噪声及图像质量主观评分,均无统计学差异(P均0.05)。A组患者的有效辐射剂量明显低于B组患者,差异有统计学意义(P0.05)。结论对于体重指数≤26的患者,低对比剂浓度和低千伏(100 kV)相对于常规扫面能够提供相似的图像质量,并减少对比剂的碘用量及有效辐射剂量。     

低剂量、大螺距双源CT前瞻性心电门控冠状动脉成像在心房颤动患者中的初步应用

目的评价第二代双源CT大螺距前瞻性心电门控扫描模式（fllash spiral）在房颤患者中应用的可行性。方法从我院接受大螺距双源CT冠状动脉成像检查的1077例患者中,选择房颤患者10例,分别采用HP前瞻性心电门控扫描（flash spiral模式）和回顾性心电门控模式扫描（spiral模式）。Flash spiral模式采集图像时间选择为RR间期的20％-30％成像。结果10例患者均采用flash模式扫描,其中7例患者图像质量好（评分1分）,3例患者有轻度伪影,但可评价血管（评分2分）。SpirM扫描中,4例病例右冠状动脉伪影重,为非诊断血管病例,1例回旋支重度伪影。Flash模式扫描有效射线剂量为O．680-1．887mSv,8例患者低于1mSv。Spiral扫描有效射线剂量为14．920-21．306mSv。结论①房颤患者采用大螺距flash spiral模式单个心动周期成像可获得良好的效果,且图像质量优于回顾性心电门控模式。②由于RR间期不规则,房颤患者flash spirM扫描时必须在下一个R波前完成扫描,需提前采集数据时间（RR间期的20％-30％采集为最佳）。③房颤患者flash spiral扫描有效射线剂量低于1mSv。     

Tomografia computorizada cardíaca prévia a ablação de fibrilhação auricular – efeitos da evolução tecnológica e otimização de protocolos

Background

Cardiac computed tomography (CT) can provide a precise tridimentional anatomic map and exclude intra‐cardiac thrombus. We aimed to access the impact of CT protocol optimization and technological evolution on the contrast and radiation dose as well as on image quality previous to atrial fibrillation (AF) ablation.

Bismuth breast-shield use in chest computed tomography for efficient dose reduction and sufficient image quality

Background:Radiosensitivity in the breasts increases the risk of carcinogenesis from exposure to the ionizing radiation of computed tomography (CT) administered in the course of medical attention. Bismuth shielding techniques have been used to reduce radiation, but image noise increased, degrading image quality.Purpose:The aim of this study was to investigate how the use of iterative reconstruction (IR) combined with bismuth shielding influences image quality.Materials and Methods:Women aged at least 20 years with body mass indexes <28 were recruited and randomly assigned to 1 of 3 CT scanning protocols without shielding, with a bismuth breast shield before the scout view, or with a bismuth breast shield after the scout view. All obtained images were reconstructed using an IR algorithm. To evaluate radiation dose, 2 Gafchromic films were placed over the clothes, 1 near each nipple.Results:Average dose reduction was significant (27.99%, P < .05) when bismuth shielding was applied after the scout view. Using the contrast-to-noise ratio, the image quality was found to be superior when the IR algorithm was applied. Using quantitative evaluations by 2 radiologists applying a 4-point Likert scale, significant differences in image quality were not found among the 3 protocols.Conclusion:Bismuth breast shields, particularly when used after acquiring scout images, are effective at reducing radiation dose without undermining the diagnostic value of the images when the IR technique is applied.     

Computed Tomography Angiography of Carotid Arteries and Vertebrobasilar System: A Simulation Study for Radiation Dose Reduction

Computed tomography angiography (CTA) of carotid arteries and vertebrobasilar system is a standardized procedure with excellent image quality, but radiation exposure remains a matter of concern. The aim of this study is to examine to what extent radiation dose can be lowered in relation to a standard protocol by simulating examinations with lower tube currents applying a dedicated software.Lower tube current was simulated by a dedicated noise insertion and reconstruction software (ReconCT). In a phantom study, true scans were performed with different dose protocols and compared to the results of simulated dose reductions of the same degree, respectively. In a patient study, 30 CTAs of supra-aortic vessels were reconstructed at a level of 100%, 75%, 50%, and 25% of the initial dose. Objective and subjective image analyses were performed.No significant noise differences between true scans and simulated scans of mimicked contrasted vessels were found. In the patient study, the quality scores of the 4 dose groups differed statistically significant; this difference vanished for the comparison of the 100% and 75% datasets after dichotomization into the categories of diagnostic and nondiagnostic image quality (P = .50).This study suggests an easy-to-implement method of simulating CTAs of carotid arteries and vertebrobasilar system with lower tube current for dose reduction by artificially adding noise to the original raw data. Lowering the radiation dose in a moderate extent to 75% of the original dose levels does not significantly alter the diagnostic image quality.     

Performance Evaluation of a Multi-Slice CT System with 16-Slice Detector and Increased Gantry Rotation Speed for Isotropic Submillimeter Imaging of the Heart

BACKGROUND: 4-slice CT scanners have shown limitations in clinical application for noninvasive coronary CT angiography (CTA). We evaluate advances in ECG-gated scanning of the heart and the coronary arteries with recently introduced 16-slice CT equipment (SOMATOM Sensation 16, Siemens, Forchheim, Germany). MATERIALS AND METHODS: The technical principles of ECG-gated cardiac scanning, scan parameters, and detector design of the new scanner are presented. ECG-gated scan and image reconstruction techniques and ECG-controlled dose modulation ("ECG pulsing") for a reduction of the patient dose are described, key parameters for image quality and simulation results presented, and phantom studies and initial patient experience discussed. The impact of reduced gantry rotation time (0.42 s) on temporal resolution and initial estimations of the patient dose are presented. RESULTS: Extensions of ECG-gated reconstruction algorithms used for 4-slice CT provide adequate image quality for up to 16 slices. For each detector collimation different slice widths are available for retrospective reconstruction with well-defined slice sensitivity profiles (SSPs). For coronary CTA the heart can be covered with 0.75 mm collimation within a 20-s breathhold. The best possible spatial resolution is 0.5 x 0.5 x 0.6 mm. For 0.42 s gantry rotation time, temporal resolution reaches its optimum (105 ms) at a heart rate of 81 bpm. Effective patient dose for coronary CTA is 4-5 mSv using ECG-pulsed acquisition. CONCLUSION: The clinical performance of coronary CTA by means of spatial resolution, temporal resolution and scan time is substantially improved with the evaluated 16-slice CT scanner. Also, display of smaller coronary segments and instent visualization are substantially improved.