The impact of dose reduction on the quantification of coronary artery calcifications and risk categorization: A systematic review

Multiple dose reduction techniques have been introduced for coronary artery calcium (CAC) computed tomography (CT), but few have emerged into clinical practice while an increasing number of patients undergo CAC scanning. We sought to determine to what extend the radiation dose in CAC CT can be safely reduced without a significant impact on cardiovascular disease (CVD) risk stratification. A systematic database-review of articles published from 2002 until February 2018 was performed in Pubmed, WebOfScience, and Embase. Eligible studies reported radiation dose reduction for CAC CT, calcium scores and/or risk stratification for phantom or patient studies. Twenty-eight studies were included, under which 17 patient studies, 10 phantom/ex-vivo studies, and 1 study evaluated both phantom and patients. Dose was reduced with tube voltage reduction and tube current reduction with and without iterative reconstruction (IR), and tin-filter spectral shaping. The different dose reduction techniques resulted in varying final radiation doses and had varying impact on CAC scores and CVD risk stratification. In 78% of the studies the radiation dose was reduced by ≥ 50% ranging from (CTDI_vol) 0.6–5.5 mGy, leading to reclassification rates ranging between 3% and 21%, depending on the acquisition technique. Specific dose reduced protocols, including either tube current reduction and IR or spectral shaping with tin filtration, that showed low reclassification rates may potentially be used in CAC scanning and in future population-based screening for CVD risk stratification.     

Comparison of MRI, 64-slice MDCT and DSCT in assessing functional cardiac parameters of a moving heart phantom

To compare magnetic resonance imaging (MRI), 64-slice multi-detector computed tomography (MDCT) and dual-source computed tomography (DSCT) in assessing global function parameters using a moving heart phantom. A moving heart phantom with known volumes (215–258 ml) moving at 50–100 beats per minute was examined by three different imaging modalities using clinically implemented scanning protocols. End-diastolic and end-systolic volumes were calculated by two experienced observers using dedicated post-processing tools. Ejection fraction (EF) and cardiac output (CO) were calculated and mutually compared using Bland-Altman plots. MRI underestimated the ejection EF by 16.1% with a Bland-Altman interval (B-A) of [-4.35 (-2.48) -0.60]. Sixty-four-slice MDCT overestimated the EF by 2.6% with a relatively wide B-A interval of [-3.40 (0.40) 4.20]. DSCT deviated the least from the known phantom volumes, underestimating the volumes by 0.8% with a B-A interval of [-1.17 (-0.13) 0.91]. CO analysis showed similar results. Furthermore, a good correlation was found between DSCT and MRI for EF and CO results. MRI systematically underestimates functional cardiac parameters, ejection fraction and cardiac output of a moving heart phantom. Sixty-four-slice MDCT underestimates or overestimates these functional parameters depending on the heart rate because of limited spatial resolution. DSCT deviates the least from these functional parameters compared to MRI, EBT and 64-slice MDCT.     

Quantification of left ventricular function and mass in cardiac Dual-Source CT (DSCT) exams: comparison of manual and semiautomatic segmentation algorithms

The purpose of our study was to evaluate reliability of left ventricular (LV) function and mass quantification in cardiac DSCT exams comparing manual contour tracing and a region-growing-based semiautomatic segmentation analysis software. Thirty-three consecutive patients who underwent cardiac DSCT exams were included. Axial 1-mm slices were used for the semiautomated technique, and short-axis 8-mm slice thickness multiphase image reconstructions were the basis for manual contour tracing. Left ventricular volumes, ejection fraction and myocardial mass were assessed by both segmentation methods. Length of time needed for both techniques was also recorded. Left ventricular functional parameters derived from semiautomatic contour detection algorithm were not statistically different from manual tracing and showed an excellent correlation (p<0.001). The semiautomatic contour detection algorithm overestimated LV mass (180.30±44.74 g) compared with manual contour tracing (156.07±46.29 g) (p<0.001). This software allowed a significant reduction of the time needed for global LV assessment (mean 174.16±71.53 s, p<0.001). Objective quantification of LV function using the evaluated region-growing-based semiautomatic segmentation analysis software is feasible, accurate, reliable and time-effective. However, further improvements are needed to equal results achieved by manual contour tracing, especially with regard to LV mass quantification.     

Quantification of left ventricular function and mass in heart transplant recipients using dual-source CT and MRI: initial clinical experience

The purpose of this study was to compare LV function and mass quantification derived from cardiac dual-source CT (DSCT) exams with those obtained by MRI in heart transplant recipients. Twelve heart transplant recipients who underwent cardiac DSCT and MRI examination were included. Double-oblique short-axis 8-mm slice thickness images were evaluated. Left ventricular ejection fraction, end-diastolic volume, end-systolic volume, stroke volume, cardiac output and myocardial mass were manually assessed for each patient by two blinded readers. A systematic overestimation of all left ventricular volumes by DSCT when compared with MRI was observed. Mean difference was 16.58 +/- 18.61 ml for EDV, 4.9 4 +/- 6.84 ml for ESV, 11.64 +/- 13.58 ml for SV and 5.73 +/- 1.14 l/min for CO. Slightly lower values for left ventricular ejection fraction with DSCT compared with MRI were observed (mean difference 0.34 +/- 3.18%, p = 0.754). Correlation between DSCT and MRI for left ventricular mass was excellent (rho = 0.972). Bland and Altman plots and CCC indicated good agreement between DSCT and MRI left ventricular function and mass measurements. The interobserver correlation was good. In conclusion, DSCT accurately estimates left ventricular ejection fraction, volumes and mass in heart transplant recipients.     

双源CT对腹腔镜保留肾单位手术治疗T1a期肾癌的应用价值

目的探讨双源CT在腹腔镜保留肾单位手术（LNSS）治疗T1a期肾癌术前评估中的应用价值。方法对60例T1a肾癌患者行双源CT检查,分别探查患侧肾脏血管解剖结构、肾肿瘤大小、位置、毗邻关系及对侧肾脏的相关情况等指标,并与LNSS术中所见及病理结果对比,研究两者的相关性。结果双源CT显示的患侧肾脏血管解剖结构、肿瘤大小、位置与LNSS术中所见均无统计学差异（均P＞0.05）,而且显示的肿瘤侵入肾实质深度以及与周围血管、集合系统的毗邻关系与病理结果具有一致性（Kappa值=0.949、0.872、0.936,均P＜0.05）。结论双源CT对LNSS治疗T1a期肾癌能更好的进行术前评估,具有较高的临床应用价值。     

双源CT血管成像技术对主动脉夹层的诊断价值研究

目的探讨双源CT血管成像技术对主动脉夹层的诊断价值。方法选择2011年12月~2013年12月在我院进行诊疗的主动脉夹层患者20例为研究对象。使用SIEMENS公司SOMATOM DEFINITION DSCT扫描仪行平扫加增强扫描。结果 20例AD(主动脉夹层患者)按DeBakey分类法分为DeBakeyⅠ型2例、Ⅱ型2例、Ⅲ型16例。按照Stanford分型法为A型6例、B型14例。"双腔主动脉"即真腔和假腔是AD诊断的主要和直接征象:双源CTA对AD真假腔及内膜瓣的显示率达100%。4例患者假腔内还出现不同程度的血栓,表现为假腔内的充盈缺损。结论双源CT血管成像技术为诊断主动脉夹层提供了更有利的指导依据,操作简单且具有强大的后处理功能,值得广泛推广和应用。     

High-pitch versus sequential mode for coronary calcium in individuals with a high heart rate: Potential for dose reduction

BackgroundTo determine the impact of high-pitch spiral acquisition on radiation dose and cardiovascular disease (CVD) risk stratification by coronary artery calcium (CAC) assessment with computed tomography in individuals with a high heart rate.MethodsOf the ROBINSCA trial, 1990 participants with regular rhythm and heart rates >65 beats per minute (bpm) were included. As reference, 390 participants with regular heart rates ≤65 bpm were used. All participants underwent prospectively electrocardiographically(ECG)-triggered imaging of the coronary arteries using dual source CT at 120 kVp, 80 ref mAs using both high-pitch spiral mode and sequential mode. Radiation dose, Agatston score, number of positive scores, as well as median absolute difference of the Agatston score were determined and participants were stratified into CVD risk categories.ResultsA similar percentage of participants with low heart rates and high heart rates had a positive CAC score in data sets acquired in high-pitch spiral (low heart rate: 57.7%, high heart rate: 55.8%) and sequential mode (58.0%, 54.7%, p = n.s.). The median absolute difference in Agatston scores between acquisition modes was 14.2% and 9.2%, for the high and low heart rate groups, respectively. Excellent agreement for risk categorization between the two data acquisition modes was found for the high (κ = 0.927) and low (κ = 0.946) heart rate groups. Radiation dose was 48% lower for high-pitch spiral versus sequential acquisitions.ConclusionRadiation dose for the quantification of coronary calcium can be reduced by 48% when using the high-pitch spiral acquisition mode compared to the sequential mode in participants with a regular high heart rate. CVD risk stratification agreement between the two modes of data acquisition is excellent.     

双源CT三维血管重建技术对“胡桃夹”综合征的应用

目的：探讨双源CT（DSCT）三维重建技术在“胡桃夹”综合征诊断中的应用价值。方法：对24例临床疑有“胡桃夹”现象患者进行（DSCT）三维重建血管造影,对左肾静脉受压处进行显示与测量。结果：24例中16例诊断有“胡桃夹”现象,表现为左肾静脉明显受压。24例患者的SMA均以小于45°的锐角从AO发出,夹角A为14°～38°,平均28．12°±7．92°;A＇为11°～21°,平均16．46°±3．42°。结论：双源CT三维重建技术可作为“胡桃夹”综合征现象最理想且无创的检查手段和诊断依据。     

DSCT在左心室功能评估中的初步研究

目的初步探讨DSCT评估左心功能的准确性.方法14例健康者和32例冠心病患者在24h同时进行DSCT和超声心动图检查,对比DSCT与超声测量值的相关性.结果DSCT与超声心动图测量结果相关性良好.结论DSCT冠状动脉造影检查所得到的左心室数据准确性高,无呼吸运动伪影、成像时间短,可用于临床诊断.