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.     

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.     

心电门控320排容积CT在急性胸痛中应用价值的前瞻性研究

目的:探讨前瞻性心电门控320排容积CT对急性胸痛成像的可行性及诊断价值。方法:对连续61例急性胸痛患者不控制心率条件下行前瞻性心电门控wide-volume模式并强制在一个心动周期扫描,曝光时间窗根据心率不同预设在40%~50%R-R间期(心率≥70次/min)或70%~80%R-R间期(心率70次/min)。2个volume涵盖自胸廓入口至心膈面,对比剂采用三相注射法以便同时显示主动脉、冠状动脉、肺动脉三大血管床。评价三大血管床的图像质量及对胸痛病因的诊断能力。记录患者的有效辐射剂量、对比剂用量。结果:61例患者的三大血管床(主动脉、冠状动脉及肺动脉)均得到明显均匀强化。主动脉和肺动脉均获得良好的可诊断图像(可诊断率达100%,61/61)。2例患者因屏气不良冠状动脉图像无法评价,在其余59例患者的625个冠状动脉节段中,图像质量为1级的占94.2%(589/625),2级图像质量占3.2%(20/625),总的可评价率达97.4%。观察者之间总的一致性较好(k=0.83,95%CI:0.60~1.00)。平均有效辐射剂量为(5.44±1.15)mSv,对比剂总量平均为(75.7±4.35)mL。本扫描计划对胸痛病因阳性诊断率为82%(50/61),CTA诊断为阴性的18%(11/61)的患者中随诊一月内无不良并发症出现。结论:320排容积CT的前瞻心电门控wide-volume扫描模式在不控制心率情况下可低辐射剂量及低对比剂用量地对急性胸痛患者进行评价。     

Radiation exposure of patients and coronary arteries in the stent era: A prospective study.

Previous studies have investigated the radiation dose to doctors and patients during coronary angiography and angioplasty, but most of them were retrospective, conducted in the prestent era, and results have not been consistent. Effective dose of 57 patients undergoing coronary angiography and/or angioplasty was assessed by using a dose-area product (DAP) to effective dose conversion factor. Radiation exposure risks to patients were then calculated for each procedure. Thermoluminescent dosimeters, mounted on a specially designed catheter that was advanced to the left or right sinus of Valsalva, were used to measure the dose received by the coronary arteries. Mean effective dose received by patients were 5.0 +/- 0.5 mSv for coronary angiography, 6.6 +/- 1.0 mSv for angioplasty, 10.2 +/- 1.5 mSv for angioplasty followed by stent implantation, 13.6 +/- 2.5 mSv for angiography followed by ad hoc angioplasty, and 16.7 +/- 2.8 mSv for angiography followed by ad hoc angioplasty and stent implantation. Patient risk of developing cancer after each procedure was 0.025%, 0.033%, 0.051%, 0.068%, and 0.084%, respectively. Corresponding mean coronary irradiation doses were 24 +/- 2.5, 31.0 +/- 3.6, 43.6 +/- 7.2, 55.0 +/- 7.5, and 64.7 +/- 5.6 mGy, respectively. A linear relationship of the DAP and the dose at the coronary arteries was found: DAP = 1,273 (cm(2)) x coronary dose (mGy). Radiation exposure to coronary arteries and associated risk to patients are relatively low, even following complicated, multivessel angioplasty with stent implantation. Our method can be used for calculation of radiation risk to patients and radiation dose to coronary arteries by using external dosimeters. Cathet. Cardiovasc. Intervent. 51:259-264, 2000.     

Effect of increasing body mass index on image quality and positive predictive value of 100-kV coronary computed tomographic angiography

Lowering the voltage to 100 kV is an effective method of reducing the radiation of coronary computed tomographic angiography (CTA). It is unknown, however, whether one could use a 100-kV CTA protocol with overweight or obese patients. We, thus, evaluated the effect of increasing body mass index (BMI) on various image quality parameters of 100-kV CTA. We also compared the radiation dose and diagnostic accuracy of 100-kV CTA with CTA performed at 120 kV. Three different protocols were studied: 120 kV, retrospective; 100 kV, retrospective; and 100 kV, prospective. The image quality and radiation doses were analyzed for each protocol. The effect of increasing BMI was also examined. A worsening of the noise, contrast-to-noise, and signal-to-noise ratios occurred with increasing BMI and decreasing voltages. The radiation exposure was significantly lowered with the 100-kV protocol and with prospective gating. Despite this image degradation, however, diagnostic images were obtained with 100-kV CTA, even in overweight and many obese subjects. Of the 66 subjects referred for invasive angiography because of the findings from CTA, 55 were correctly characterized (overall positive predictive value [PPV] of 83.3%). This PPV remained reasonable, irrespective of the voltage, until a BMI of 35 kg/m(2) was reached (PPV for 100-kV protocol 90.0% [27 of 30]; PPV for a BMI of ≥ 25 kg/m(2) but < 30 kg/m(2) 84.4% [27 of 32]; and PPV for a BMI of ≥ 30 kg/m(2) but < 35 kg/m(2) 81.8% [18 of 22]). In conclusion, 100-kV coronary CTA is feasible in overweight and many obese subjects.     

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.     

Advances in Nuclear Cardiac Instrumentation with a View Towards Reduced Radiation Exposure

Recent advances in nuclear cardiology instrumentation have enabled myocardial perfusion imaging (MPI) with improved image quality and faster scan times. These developments also can be exploited to reduce the effective radiation dose to the patient. In this review, we discuss these technologies including new single photon emission computed tomography (SPECT) and positron emission tomography (PET) scanners, as well as novel reconstruction software with regard to their potential for the reduction of the patient radiation dose. New advances in nuclear cardiology instrumentation will allow routine rest/stress MPI imaging with low radiation doses (<5 mSv) and fast imaging times, even by the software-only solutions. It is possible to further reduce the MPI radiation dose to less than 2 to 3 mSv range with standard acquisition times. PET perfusion imaging also can be performed with very low doses especially by the three-dimensional scanners allowing hybrid PET/computed tomographic angiography (CTA) imaging with low overall dose. In addition, stress-only protocols can be utilized to further reduce the radiation dose and the overall test time.     

Ultra-fast,low dose high-pitch (FLASH) versus prospectively-gated coronary computed tomography angiography: Comparison of image quality and patient radiation exposure

Background

Coronary computed tomography angiography (CCTA) is increasingly being used for the evaluation of coronary artery disease; however, radiation exposure remains a major limitation of its use.

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。     

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.     

窄窗扫描技术在高心率患者320排CT冠状动脉成像中的应用研究

目的：探讨高心律患者320排CT冠状动脉成像使用前瞻性心电门控窄窗扫描技术对图像质量和辐射剂量的影响。方法80例心率在80~100次/min的患者随机分成观察组和对照组。观察组按R- R间期30％～50％进行前瞻性窄窗扫描3个心动周期,对照组按R- R间期30％～80％进行常规扫描3个心动周期,冠状动脉节段图像质量采用4级评分法评分,辐射剂量值由设备自动计算。结果可评价血管段和优良率两组间差异无统计学意义（P＞0.05）。冠状动脉总节段、右冠状动脉（RCA）、左冠状动脉主干（LM）、左前降支（LAD）和旋支（LCX）的质量评分两组间差异无统计学意义（P＞0.05）。观察组的RCA和LCX与心律波动呈中等程度负相关（r =0.41、0.47）。观察组和对照组平均辐射剂量分别为（7.63±3.29）和（12.85±2.71）mSv,差异有统计学意义（t=1.384,P＜0.05）。结论窄窗扫描技术可应用在心律波动不大的高心率患者,能明显降低辐射剂量而不影响图像质量。     

胸部低剂量CT扫描在AIDS合并PCP体质量低者中的应用价值

目的探讨低剂量CT扫描在AIDS合并PCP体质量低者中的应用可行性及临床价值。方法将69例AIDS合并PCP体质量低患者,随机分成3组,分别采用管电压固定为120kV,常规剂量(自动mAs)与低剂量扫描,低剂量扫描管电流分别采用40mAs,30mAs,20mAs,对图像质量、辐射剂量进行分析,得出AIDS合并PCP体质量低患者的最优低剂量扫描方案。结果常规剂量扫描与低剂量扫描获得图像均能达到影像诊断要求。采用管电压固定为120kV,管电流为常规剂量、40 mAs、30 mAs、20 mAs组获得的平均辐射剂量CTDIvol分别为:6.65mGy、2.06 mGy、1.54 mGy、1.03 mGy,管电流20 mAs组最低,为常规剂量的15.5%。结论采用管电压kV值固定为120kV,管电流20mAs胸部低剂量CT扫描在AIDS合并PCP体质量低患者中图像质量能满足临床诊断要求,同时降低辐射剂量,值得推广。     

Comparison of diagnostic accuracy and radiation dose between prospective triggering and retrospective gated coronary angiography by dual-source computed tomography

The purpose of this study was to evaluate and compare the diagnostic accuracy and radiation dose of dual-source computed tomographic (DSCT) coronary angiography for assessment of coronary artery disease using prospective electrocardiographic triggering and retrospective electrocardiographically (ECG) gated spiral scans. One hundred sixteen patients who had undergone dual-source computed tomography and conventional coronary angiography were enrolled in this study. Fifty-four patients were scanned using retrospective ECG-gated protocols (group 1) and 62 patients using prospective ECG-triggered protocols (group 2). Diagnostic accuracy, image quality, and effective dose were compared between groups 1 and 2. Conventional coronary angiography was used as the reference standard. In total 1,709 (98.2%) coronary segments in the 116 patients were assessable with adequate image quality. Sensitivities and specificities of diagnosing coronary heart disease (≥50% stenosis) in a patient-based analysis of DSCT data were 93.3% and 88.9% in group 1 and 96.4% and 85.7% in group 2, respectively (p=0.973 and 0.761). In vessel-based analysis, sensitivities and specificities were 77.4% and 94.1% in group 1 and 79.6% and 92.3% in group 2 (p=0.983 and 0.985). Overall averaged image quality scores (using 1- to 4-point scale) in groups 1 and 2 were 3.3 ± 0.4 and 3.5 ± 0.9, respectively (p=0.268). Prevalence of good (score 3.0) and excellent (score 4.0) image qualities of coronary vessels were 95.4% in group 1 and 92.4% in group 2 (p = 0.861). Effective doses were 8.82 ± 3.50 mSv (range 3.92 to 15.36) in group 1 and 2.95 ± 1.39 mSv (range 0.99 to 6.06) in group 2 (p<0.001). In conclusion, DSCT prospective ECG-triggered coronary angiography has equivalent image quality and diagnostic value compared to that of retrospective ECG-gated scans. Radiation dose was significantly decreased using prospective electrocardiographic triggering.     

16排移动CT在ICU床旁与车载头部扫描结果对比分析

目的对比分析16排移动CT在ICU床旁与车载头部扫描结果。 方法廊坊爱德堡医院神经外科自2017年12月1日至2019年11月30日应用国产16排移动CT进行头部扫描661例次，其中ICU床旁扫描27例次（ICU组），车载扫描634例次（车载组）。统计2组受检者诊断阳性率，并从车载扫描者中随机选择30例次与ICU床旁头部扫描27例次对比分析成像质量及运动伪影发生率、检查时间及辐射剂量值等。 结果ICU组移动CT头部扫描27例次，均为阳性诊断，车载组634例次，阳性诊断419例。ICU组（27例次）和车载组（30例次）成像质量良好，颅底层面发生线状运动伪影ICU组为7.41%，车载组为16.67%。ICU组床旁扫描耗时最短10.6 min，最长19.4 min，平均15.68 min。车载扫描耗时最短15.9 min，最长37.4 min，平均26.40 min。16排移动CT成人头部扫描的有效容积剂量CTDIvol为（34.55±4.08）mGy，有效剂量为（0.80±0.06）mSv。 结论16排移动CT在ICU床旁扫描和车载扫描成像质量可靠，检查耗时短，辐射剂量低，使用安全。     

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.     

Coronary CT angiography with single-source and dual-source CT: Comparison of image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated protocols

Background

This study is conducted to investigate and compare image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated coronary CT angiography (CCTA) with the use of single-source CT (SSCT) and dual-source CT (DSCT).

Methods

A total of 209 patients who underwent CCTA with suspected coronary artery disease scanned with SSCT (n = 95) and DSCT (n = 114) scanners using prospective ECG-triggered and retrospective ECG-gated protocols were recruited from two institutions. The image was assessed by two experienced observers, while quantitative assessment was performed by measuring the image noise, the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). Effective dose was calculated using the latest published conversion coefficient factor.

Results

A total of 2087 out of 2880 coronary artery segments were assessable, with 98.0% classified as of sufficient and 2.0% as of insufficient image quality for clinical diagnosis. There was no significant difference in overall image quality between prospective ECG-triggered and retrospective gated protocols, whether it was performed with DSCT or SSCT scanners. Prospective ECG-triggered protocol was compared in terms of radiation dose calculation between DSCT (6.5 ± 2.9 mSv) and SSCT (6.2 ± 1.0 mSv) scanners and no significant difference was noted (p = 0.99). However, the effective dose was significantly lower with DSCT (18.2 ± 8.3 mSv) than with SSCT (28.3 ± 7.0 mSv) in the retrospective gated protocol.

Conclusions

Prospective ECG-triggered CCTA reduces radiation dose significantly compared to retrospective ECG-gated CCTA, while maintaining good image quality.     

Radiation dose levels in chest computed tomography scans of coronavirus disease 2019 pneumonia: A survey of 2119 patients in Chongqing,southwest China

To investigate computed tomography (CT) diagnostic reference levels for coronavirus disease 2019 (COVID-19) pneumonia by collecting radiation exposure parameters of the most performed chest CT examinations and emphasize the necessity of low-dose CT in COVID-19 and its significance in radioprotection.The survey collected RIS data from 2119 chest CT examinations for 550 COVID-19 patients performed in 92 hospitals from January 23, 2020 to May 1, 2020. Dose data such as volume computed tomography dose index, dose-length product, and effective dose (ED) were recorded and analyzed. The radiation dose levels in different hospitals have been compared, and average ED and cumulative ED have been studied.The median dose-length product, volume computed tomography dose index, and ED measurements were 325.2 mGy cm with a range of 6.79 to 1098 mGy cm, 9.68 mGy with a range of 0.62 to 33.80 mGy, and 4.55 mSv with a range of 0.11 to 15.37 mSv for COVID-19 CT scanning protocols in Chongqing, China. The distribution of all observed EDs of radiation received by per patient undergoing CT protocols during hospitalization yielded a median cumulative ED of 17.34 mSv (range, 2.05–53.39 mSv) in the detection and management of COVID-19 patients. The average number of CT scan times for each patient was 4.0 ± 2.0, and the average time interval between 2 CT scans was 7.0 ± 5.0 days. The average cumulative ED of chest CT examinations for COVID-19 patients in Chongqing, China greatly exceeded public limit and the annual dose limit of occupational exposure in a short period.For patients with known or suspected COVID-19, a chest CT should be performed on the principle of rapid-scan, low-dose, single-phase protocol instead of routine chest CT protocol to minimize radiation doses and motion artifacts.     

绝对时相收缩期采集降低心房颤动患者冠状动脉CT成像辐射剂量的研究

目的:研究绝对时相收缩期采集在心房颤动患者冠状动脉CT血管造影(CTA)的可行性,并与相对时相采集对照。方法:连续入组92例持续心房颤动患者,其中A组46例采用绝对时相收缩期采集(R波后200~400ms),B组46例采用相对时相收缩期采集(R-R间期:30%~50%)。对两组扫描的冠状动脉分别做图像处理。比较两组的图像质量和辐射剂量。结果:A组冠状动脉段图像质量总体评分为(1.56±0.25),B组为(1.62±0.28),两组间差异无统计学意义(P=0.283)。两组之间可诊断的冠状动脉段比率差异无统计学意义(P=0.785)。A组有效剂量5.76(3.20,8.63)mSv;B组有效剂量9.27(4.74,12.65)mSv,两组间有效剂量差异有统计学意义(P=0.001)。绝对时相采集比相对时相采集降低辐射剂量约38%。结论:在心房颤动患者绝对时相收缩期采集具有可行性,该方案比相对时相采集显著降低辐射剂量,而不影响图像质量。     

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。