Percent atheroma volume: Optimal variable to report whole-heart atherosclerotic plaque burden with coronary CTA,the PARADIGM study

Background and aimsDifferent methodologies to report whole-heart atherosclerotic plaque on coronary computed tomography angiography (CCTA) have been utilized. We examined which of the three commonly used plaque burden definitions was least affected by differences in body surface area (BSA) and sex.MethodsThe PARADIGM study includes symptomatic patients with suspected coronary atherosclerosis who underwent serial CCTA >2 years apart. Coronary lumen, vessel, and plaque were quantified from the coronary tree on a 0.5 mm cross-sectional basis by a core-lab, and summed to per-patient. Three quantitative methods of plaque burden were employed: (1) total plaque volume (PV) in mm³, (2) percent atheroma volume (PAV) in % [which equaled: PV/vessel volume * 100%], and (3) normalized total atheroma volume (TAV_norm) in mm³ [which equaled: PV/vessel length * mean population vessel length]. Only data from the baseline CCTA were used. PV, PAV, and TAV_norm were compared between patients in the top quartile of BSA vs the remaining, and between sexes. Associations between vessel volume, BSA, and the three plaque burden methodologies were assessed.ResultsThe study population comprised 1479 patients (age 60.7 ± 9.3 years, 58.4% male) who underwent CCTA. A total of 17,649 coronary artery segments were evaluated with a median of 12 (IQR 11–13) segments per-patient (from a 16-segment coronary tree). Patients with a large BSA (top quartile), compared with the remaining patients, had a larger PV and TAV_norm, but similar PAV. The relation between larger BSA and larger absolute plaque volume (PV and TAV_norm) was mediated by the coronary vessel volume. Independent from the atherosclerotic cardiovascular disease risk (ASCVD) score, vessel volume correlated with PV (P < 0.001), and TAV_norm (P = 0.003), but not with PAV (P = 0.201). The three plaque burden methods were equally affected by sex.ConclusionsPAV was less affected by patient's body surface area then PV and TAV_norm and may be the preferred method to report coronary atherosclerotic burden.     

2014年宁夏地区放射诊疗机构辐射防护监测结果分析

目的 比较容积CT剂量指数(CTDI_vol)及体型特异性剂量估算(SSDE)在估算腹部CT扫描时患者所受辐射剂量的差异。方法 采用Philips 256螺旋CT扫描仪对180例患者进行上腹部CT增强扫描,在左肾静脉主干层面测量每位患者的左右径(LAT)、前后径(AP),计算有效直径(ED),同时记录每位被检者的CTDI_vol值及体模的扫描直径,计算SSDE。将患者按照体重指数(BMI)分为3组:A组,BMI<20 kg/m²;B组,BMI介于20～24.9 kg/m²之间;C组,BMI>24.9 kg/m²。分别比较180例被检者及不同体重指数组CTDI_vol与SSDE之间的差异。结果 180例被检者CTDI_vol和SSDE分别为(9.91±2.91)和(14.01±2.82)mGy,差异有统计学意义(t=-13.354,P=0.000)。A组CTDI_vol和SSDE分别为(7.96±1.83)和(12.83±2.52)mGy ( t=-8.417,P =0.000);B组分别为(9.28±1.76)和(13.62±2.18)mGy(t=-15.051,P=0.000);C组分别为(12.19±3.65)和(15.39±3.47)mGy(t=-4.535,P=0.000)。此外,3组SSDE分别较CTDI_vol平均增加了62.83%、 47.80%和28.40%,即CTDI_vol过低估算被检者的辐射剂量,且随着体重指数的增加,CTDI_vol与SSDE之间的差值越小。结论 SSDE能够反映特定体型的被检者进行腹部CT扫描时所接受的辐射剂量。     

对比分析容积CT剂量指数与体型特异性的剂量评估在估算腹部CT扫描辐射剂量中的差异

目的 比较容积CT剂量指数(CTDI_vol)及体型特异性剂量评估(SSDE)在估算腹部CT扫描时患者所受辐射剂量的差异。方法 采用Philips 256螺旋CT扫描仪对180例患者进行上腹部CT增强扫描,在左肾静脉主干层面测量每例患者的左右径(LAT)、前后径(AP),计算有效直径(ED),同时记录每例被检者的CTDI_vol值及体模的扫描直径,计算SSDE。将患者按照体质量指数(BMI)分为3组:A组,BMI<20.0 kg/m²;B组,BMI介于20.0~24.9 kg/m²之间;C组,BMI>24.9 kg/m²。分别比较180例被检者及不同体质量指数组CTDI_vol与SSDE之间的差异。结果180例被检者CTDI_vol和SSDE分别为(9.91±2.91)和(14.01±2.82)mGy,差异有统计学意义(t=-13.354, P<0.01)。A组CTDI_vol和SSDE分别为(7.96±1.83)和(12.83±2.52)mGy (t=-8.417, P<0.01);B组分别为(9.28±1.76)和(13.62±2.18)mGy(t=-15.051,P<0.01);C组分别为(12.19±3.65)和(15.39±3.47)mGy(t=-4.535,P<0.01)。此外,3组SSDE分别较CTDI_vol平均增加了62.83%、 47.80%和28.40%,即CTDI_vol过低估算被检者的辐射剂量,且随着体质量指数的增加,CTDI_vol与SSDE之间的差值越小。结论 SSDE能够反映特定体型的被检者进行腹部CT扫描时所接受的辐射剂量。     

Patient dose increase caused by posteroanterior CT localizer radiographs

IntroductionThe aim of this study was to compare the output dose (volume CT dose index [ CTDI_vol], and dose length product [DLP]) of automatic tube current modulation (ATCM) determined by localizer radiographs obtained in the anteroposterior (AP) and posteroanterior (PA) directions.MethodsOne hundred and twenty-four patients who underwent upper abdomen and/or chest–to–pelvis computed tomography (CT) were included. Patients underwent two series of CT examinations, and localizer radiographs were obtained in the AP and PA directions. The horizontal diameter of the localizer radiograph, scan length, CTDI_vol, and DLP were measured.ResultsThere was no significant difference in the scan length; however, all the other values were significantly higher in the PA direction. The mean horizontal diameter was 33.1 ± 2.6 cm and 35.4 ± 2.9 cm in the AP and PA directions of the localizer radiographs, respectively. The CTDI_vol and DLP in the PA direction increased by approximately 7–8%.Bland-Altman plots between AP and PA localizer directions in upper abdominal CT showed a positive bias of 1.1 mGy and 30.0 mGy cm for CTDI_vol and DLP, respectively. Correspondingly, chest–to–pelvic CT showed a positive bias of 0.93 mGy and 69.3 mGy cm for CTDI_vol and DLP, respectively.ConclusionThe output dose of ATCM determined by localizer radiographs obtained in the PA direction was increased compared to the AP direction. Localizer radiographs obtained in the AP direction should be preferred for optimizing the output dose using ATCM.Implications for practiceBased on the evidence of this study, localizer radiographs obtained in the AP direction should be preferred for optimizing the output dose in CT examinations.     

前置体型特异性剂量估算值优化CT冠状动脉成像的可行性

目的 探讨前置体型特异性剂量估算值（SSDE）优化CT冠状动脉成像（CCTA）的可行性。方法 回顾性分析2018年3月至2018年5月衢州市人民医院90例行CCTA扫描的患者资料,建立水等效直径（d_w）与体质量指数（BMI）的回归方程,并计算容积CT剂量指数（CTDI_vol）上四分位数。前瞻性收集2018年12月至2019年1月衢州市人民医院行CCTA扫描患者67例,按随机数表法分为对照组（32例）和试验组（35例）。对照组使用固定CTDI_vol设定扫描方案,试验组使用固定SSDE设定扫描方案。两组的目标剂量为90例患者CTDI_vol的上四分位数。评估并比较两组图像质量及辐射剂量。结果 90例患者BMI与d_w正相关（r=0.823,P<0.05）,回归方程为d_w=9.241+0.644×BMI;CTDI_vol的上四分位数为7.92 mGy。对照组和试验组冠状动脉血管段图像质量的优良率分别为94.10%（367/390）和93.93%（402/428）,差异无统计学意义（P> 0.05）;对照组和试验组SNR和CNR的中位数分别为21.08、24.39和17.24、19.94,差异无统计学意义（P> 0.05）。试验组的CTDI_vol、SSDE和女性乳腺辐射剂量（D_bre）分别较对照组降低37.04%、35.77%和37.37%,差异均具有统计学意义（z=-7.041,t=18.479,15.079,P<0.05）。结论 基于前置SSDE设定CCTA方案具有可行性,保证图像质量的同时,可有效降低辐射剂量。     

Comparison of coronary atherosclerotic plaque progression in East Asians and Caucasians by serial coronary computed tomographic angiography: A PARADIGM substudy

ObjectivesTo investigate potential differences in plaque progression (PP) between in East Asians and Caucasians as well as to determine clinical predictors of PP in East Asians.BackgroundStudies have demonstrated differences in cardiovascular risk factors as well as plaque burden and progression across different ethnic groups.MethodsThe study comprised 955 East Asians (age 60.4 ?± ?9.3 years, 50.9% males) and 279 Caucasians (age 60.4 ?± ?8.6 years, 74.5% males) who underwent two serial coronary computed tomography angiography (CCTA) studies over a period of at least 24 months. Patients were enrolled and analyzed from the PARADIGM (Progression of AtheRosclerotic PlAque DetermIned by Computed TomoGraphic Angiography IMaging) registry. After propensity-score matching, plaque composition and progression were compared between East Asian and Caucasian patients. Within East Asians, the plaque progression group (defined as plaque volume at follow-up CCTA minus plaque volume at baseline CCTA> 0) was compared to the no PP group to determine clinical predictors for PP in East Asians.ResultsIn the matched cohort, baseline volumes of total plaque as well as all plaque subtypes were comparable. There was a trend towards increased annualized plaque progression among East Asians compared to Caucasians (18.3 ?± ?24.7 ?mm³/year vs 16.6 ?mm³/year, p ?= ?0.054). Among East Asians, 736 (77%) had PP. East Asians with PP had more clinical risk factors and higher plaque burden at baseline (normalized total plaque volume of144.9 ?± ?233.3 ?mm³ vs 36.6 ?± ?84.2 ?mm³ for PP and no PP, respectively, p ?< ?0.001). Multivariate logistic regression analysis showed that baseline normalized plaque volume (OR: 1.10, CI: 1.10–1.30, p ?< ?0.001), age (OR: 1.02, CI: 1.00–1.04, p ?= ?0.023) and body mass index (OR: 2.24, CI: 1.01–1.13, p ?= ?0.024) were all predictors of PP in East Asians. Clinical events, driven mainly by percutaneous coronary intervention, were higher among the PP group with a total of 124 (16.8%) events compared to 22 (10.0%) in the no PP group (p ?= ?0.014).ConclusionEast Asians and Caucasians had comparable plaque composition and progression. Among East Asians, the PP group had a higher baseline plaque burden which was associated with greater PP and increased clinical events.     

Coronary Artery Lumen Segmentation Using Location–Adaptive Threshold in Coronary Computed Tomographic Angiography: A Proof-of-Concept

ObjectiveTo compare the lumen parameters measured by the location-adaptive threshold method (LATM), in which the inter- and intra-scan attenuation variabilities of coronary computed tomographic angiography (CCTA) were corrected, and the scan-adaptive threshold method (SATM), in which only the inter-scan variability was corrected, with the reference standard measurement by intravascular ultrasonography (IVUS).Materials and MethodsThe Hounsfield unit (HU) values of whole voxels and the centerline in each of the cross-sections of the 22 target coronary artery segments were obtained from 15 patients between March 2009 and June 2010, in addition to the corresponding voxel size. Lumen volume was calculated mathematically as the voxel volume multiplied by the number of voxels with HU within a given range, defined as the lumen for each method, and compared with the IVUS-derived reference standard. Subgroup analysis of the lumen area was performed to investigate the effect of lumen size on the studied methods. Bland-Altman plots were used to evaluate the agreement between the measurements.ResultsLumen volumes measured by SATM was significantly smaller than that measured by IVUS (mean difference, 14.6 mm³; 95% confidence interval [CI], 4.9–24.3 mm³); the lumen volumes measured by LATM and IVUS were not significantly different (mean difference, −0.7 mm³; 95% CI, −9.1–7.7 mm³). The lumen area measured by SATM was significantly smaller than that measured by LATM in the smaller lumen area group (mean of difference, 1.07 mm²; 95% CI, 0.89–1.25 mm²) but not in the larger lumen area group (mean of difference, −0.07 mm²; 95% CI, −0.22–0.08 mm²). In the smaller lumen group, the mean difference was lower in the Bland-Altman plot of IVUS and LATM (0.46 mm²; 95% CI, 0.27–0.65 mm²) than in that of IVUS and SATM (1.53 mm²; 95% CI, 1.27–1.79 mm²).ConclusionSATM underestimated the lumen parameters for computed lumen segmentation in CCTA, and this may be overcome by using LATM.     

Establishment of CT diagnostic reference levels (DRLs) for a Singapore healthcare cluster

IntroductionThe use of computed tomography (CT) in healthcare institutions has increased rapidly in recent years. The Singapore Health Services (SingHealth) cluster of healthcare institutions has taken the first step in establishing a local cluster-wide CT Diagnostic Reference Levels (DRL) in Singapore. CT dose data from each institution were collected through two primary dosimetry metrics: volume CT dose index (CTDI_vol measured in mGy) and dose-length product (DLP measured in mGy.cm).MethodsData from 19 CT scanners in seven institutions under one of Singapore healthcare cluster were retrospectively collected and analysed. The five common adult CT examinations analysed were CT Brain (non-contrast enhanced), CT Chest (IV contrast enhanced), CT Kidney-Ureter-Bladder (CT KUB, non-contrast enhanced), CT Pulmonary Angiogram (CT PA, IV contrast enhanced) and CT Abdomen-Pelvis (CT AP, IV contrast enhanced, single phase). Median CTDI_vol and DLP values for the five CT examinations from each institution were derived, with the cluster DRLs determined as the 75th percentile of the distribution of the institution median dose values.ResultsA total of 2413 dose data points were collected over a six-month period from June to November 2020. The cluster CT DRLs for the five CT examinations were determined to be 47 mGy and 820 mGy.cm for CT Brain, 5.4 mGy and 225 mGy.cm for CT Chest, 6.7 mGy and 248 mGy.cm for CT PA, 4.6 mGy and 190 mGy.cm for CT KUB and 6.9 mGy and 349 mGy.cm for CT AP.ConclusionThe establishment of the cluster CT DRLs provided individual institutions with a better understanding if their CT doses are unusually high or low, while emphasising that these DRLs are not meant as hard dose limits or constraints to follow strictly.     

Estimation of dose to the unborn child at diagnostic X-ray examinations based on data registered in RIS/PACS

The aim of this work was to determine mean absorbed doses to the unborn child in common conventional X-ray and computed tomography (CT) examinations and to find an approach for estimating foetal dose based on data registered in the Radiological Information System/Picture Archive and Communication System (RIS/PACS). The kerma-area product (KAP) and CT dose index (CTDI_vol) in common examinations were registered using a human-shaped female dosimetry phantom. Foetal doses, D_f, were measured using thermoluminescent dosimeters placed inside the phantom and compared with calculated values. Measured foetal doses were given in relation to the KAP and the CTDI_vol values, respectively. Conversion factor D_f/KAP varies between 0.01 and 3.8 mGy/Gycm², depending on primary beam position, foetus age and beam quality (tube voltage and filtration). Conversion factors D_f/CTDI_vol are in the range 0.02 – 1.2 mGy/mGy, in which the foetus is outside or within the primary beam. We conclude that dose conversion factors based on KAP or CTDI_vol values automatically generated by the RIS/PACS system can be used for rapid estimations of foetal dose for common examination techniques. Ethical Committee: No patients were involved in this study.     

能谱智能匹配联合双低技术在CT门静脉成像中的可行性研究

目的 探索单能量成像结合自适应统计迭代重建（adaptive statistical iterative reconstruction,ASIR）及自动能谱协议选择（automatic spectral imaging mode selection,ASIS）技术在个体化降低患者门静脉造影辐射剂量、对比剂剂量中的应用价值。方法 回顾性收集华中科技大学同济医学院附属协和医院2017年1月至2017年4月120例临床需进行上腹部增强检查的受检者资料（男80例,女40例）,按扫描方案分为3组,每组各40例。A组采用常规120 kVp扫描,噪声指数（NI）=10,对比剂用量为450 mgI/kg,图像采用50% ASIR重建;B、C两组采用能谱成像模式,NI=10（B组）,NI=13（C组）,对比剂用量均为300 mgI/kg,图像采用60 keV+50% ASIR重建。采用单因素方差分析比较3组图像中门静脉、肝实质的平均CT值及其差值、图像噪声、信噪比（SNR）及对比噪声比（CNR）。由两位高年资放射科医师对3组图像进行主观图像质量评分。记录患者的容积CT剂量指数（CTDI_vol）、剂量长度乘积（DLP）并计算有效剂量（E）。结果 B、C两组对比剂用量较A组降低了约30%。A、B、C组图像的门静脉CT值分别为168.22±17.82、209.06±20.07、211.03±25.60,B、C组与A比较,差异有统计学意义（t=-9.625、-8.680,P<0.05）。A、B、C 3组门静脉与肝实质CT差值分别为60.01±17.01、106.63±25.83、107.72±25.39,B、C组与A组比较,差异有统计学意义（t=-9.536、-9.857,P<0.05）。SNR分别为8.48±1.41、12.64±2.94、10.77±1.94,CNR分别为5.16±1.80、8.13±2.54、7.32±1.84,图像质量评分分别为（3.53±0.68）、（4.75±0.54）和（4.53±0.64）分,B、C组的SNR、CNR和图像质量评分与A组比较,差异有统计学意义（t=-8.082、-6.064、-6.050、-5.308、-8.912、-6.779,P<0.05）。A、B、C组CTDI_vol分别为（12.15±5.02）、（12.34±4.18）、（10.03±3.13）mGy,DLP分别为（348.62±155.99）、（355.56±131.07）、（287.10±92.25）mGy·cm,E分别为（5.23±2.34）、（5.33±1.97）、（4.31±1.38）mSv,相对于A、B两组,C组的CTDI_vol、DLP和E差异均有统计学意义（t=2.274、2.147、2.147、2.812、2.702、2.702,P<0.05）,分别降低了19%。结论 CT门静脉成像时,选择NI=13,60 keV结合50%ASIR重建及ASIS技术可以个体化降低患者的对比剂剂量和辐射剂量,并提供满足诊断要求的图像。     

上海市4家儿童医院的儿童CT剂量分析

目的通过对上海市儿童CT扫描受检者剂量参数的调查, 探讨上海地区儿童CT扫描剂量分布情况, 并为建立上海地区儿童受检者CT检查诊断参考水平提供依据。方法 2021年在上海地区全部4家儿童医院开展儿童头颅、胸部、腹部CT扫描受检者剂量普查, 调查对象按年龄0～、1～、5～、10～15岁分为4个年龄组, 每个年龄组调查30例, 收集受检者基本信息、CT扫描参数、容积CT剂量指数(CTDIvol)和剂量长度乘积(DLP)等剂量指标, 分析同一部位不同年龄组之间和同一部位同一年龄组不同医院之间CTDIvol、DLP的差异。结果头颅CT扫描时, 0～、1～、5～、10～15岁组儿童CTDIvol和DLP的75%位数分别为25、25、28、43 mGy和402、477、504、752 mGy·cm;胸部CT扫描时, 0～、1～、5～、10～15岁组儿童CTDIvol和DLP的75%位数分别为2.7、2.2、2.8、5.4 mGy和40、48、75、176 mGy·cm;腹部CT扫描时, 0～、1～、5～、10～15岁组儿童CTDIvol和DLP的75%位数分别为4.9、4.4、8.2、12 mGy...     

Diagnostic value of comprehensive on-site and off-site coronary CT angiography for identifying hemodynamically obstructive coronary artery disease

BackgroundThis study aimed to investigate the diagnostic value of comprehensive on-site coronary computed tomography angiography (CCTA) using stenosis and plaque measures and subtended myocardial mass (V_sub) for fractional flow reserve (FFR) defined hemodynamically obstructive coronary artery disease (CAD). Additionally, the incremental diagnostic value of off-site CT-derived FFR (FFR_CT) was assessed.MethodsProspectively enrolled patients underwent CCTA followed by invasive FFR interrogation of all major coronary arteries. Vessels with ≥30% stenosis were included for analysis. On-site CCTA assessment included qualitative and quantitative stenosis (visual grading and minimal lumen area, MLA) and plaque measures (characteristics and volumes), and V_sub. Diagnostic value of comprehensive on-site CCTA assessment was tested by comparing area under the curves (AUC). In vessels with available FFR_CT, the incremental value of off-site FFR_CT was tested.ResultsIn 236 vessels (132 patients), MLA, positive remodeling, non-calcified plaque volume, and V_sub were independent on-site CCTA predictors for hemodynamically obstructive CAD (p < 0.05 for all). V_sub/MLA² outperformed all these on-site CCTA parameters (AUC = 0.85) and V_sub was incremental to all other CCTA predictors (p = 0.02). In subgroup analysis (n = 194 vessels), diagnostic performance of FFR_CT and V_sub/MLA² was similar (AUC 0.89 and 0.85 respectively, p = 0.25). Furthermore, diagnostic performance significantly albeit minimally increased when FFR_CT was added to on-site CCTA assessment (ΔAUC = 0.03, p = 0.02).ConclusionsIn comprehensive on-site CCTA assessment, V_sub/MLA2 demonstrated greatest diagnostic value for hemodynamically obstructive CAD and V_sub was incremental to all evaluated CCTA indices. Additionally, adding FFR_CT only minimally increased diagnostic performance, demonstrating that on-site CCTA assessment is a reasonable alternative to FFR_CT.     

Endothelial shear stress computed from coronary computed tomography angiography: A direct comparison to intravascular ultrasound

IntroductionIntravascular ultrasound (IVUS) studies have shown that biomechanical variables, particularly endothelial shear stress (ESS), add synergistic prognostic insight when combined with anatomic high-risk plaque features. Non-invasive risk assessment of coronary plaques with coronary computed tomography angiography (CCTA) would be helpful to enable broad population risk-screening.AimTo compare the accuracy of ESS computation of local ESS metrics by CCTA vs IVUS imaging.MethodsWe analyzed 59 patients from a registry of patients who underwent both IVUS and CCTA for suspected CAD. CCTA images were acquired using either a 64- or 256-slice scanner. Lumen, vessel, and plaque areas were segmented from both IVUS and CCTA (59 arteries, 686 3-mm segments). Images were co-registered and used to generate a 3-D arterial reconstruction, and local ESS distribution was assessed by computational fluid dynamics (CFD) and reported in consecutive 3-mm segments.ResultsAnatomical plaque characteristics (vessel, lumen, plaque area and minimal luminal area [MLA] per artery) were correlated when measured with IVUS and CCTA: 12.7 ​± ​4.3 vs 10.7 ​± ​4.5 ​mm², r ​= ​0.63; 6.8 ​± ​2.7 vs 5.6 ​± ​2.7 ​mm², r ​= ​0.43; 5.9 ​± ​2.9 vs 5.1 ​± ​3.2 ​mm², r ​= ​0.52; 4.5 ​± ​1.3 vs 4.1 ​± ​1.5 ​mm², r ​= ​0.67 respectively. ESS metrics of local minimal, maximal, and average ESS were also moderately correlated when measured with IVUS and CCTA (2.0 ​± ​1.4 vs 2.5 ​± ​2.6 ​Pa^, r ​= ​0.28; 3.3 ​± ​1.6 vs 4.2 ​± ​3.6 ​Pa, r ​= ​0.42; 2.6 ​± ​1.5 vs 3.3 ​± ​3.0 ​Pa, r ​= ​0.35, respectively). CCTA-based computation accurately identified the spatial localization of local ESS heterogeneity compared to IVUS, with Bland-Altman analyses indicating that the absolute ESS differences between the two CCTA methods were pathobiologically minor.ConclusionLocal ESS evaluation by CCTA is possible and similar to IVUS; and is useful for identifying local flow patterns that are relevant to plaque development, progression, and destabilization.     

Impact of age on coronary artery plaque progression and clinical outcome: A PARADIGM substudy

BackgroundThe association of age with coronary plaque dynamics is not well characterized by coronary computed tomography angiography (CCTA).MethodsFrom a multinational registry of patients who underwent serial CCTA, 1153 subjects (61 ± 5 years old, 61.1% male) were analyzed. Annualized volume changes of total, fibrous, fibrofatty, necrotic core, and dense calcification plaque components of the whole heart were compared by age quartile groups. Clinical events, a composite of all-cause death, acute coronary syndrome, and any revascularization after 30 days of the initial CCTA, were also analyzed. Random forest analysis was used to define the relative importance of age on plaque progression.ResultsWith a 3.3-years’ median interval between the two CCTA, the median annual volume changes of total plaque in each age quartile group was 7.8, 10.5, 10.8, and 12.1 mm³/year and for dense calcification, 2.5, 4.6, 5.4, and 7.1 mm³/year, both of which demonstrated a tendency to increase by age (p-for-trend = 0.001 and < 0.001, respectively). However, this tendency was not observed in any other plaque components. The annual volume changes of total plaque and dense calcification were also significantly different in the propensity score-matched lowest age quartile group versus the other age groups as was the composite clinical event (log-rank p = 0.003). In random forest analysis, age had comparable importance in the total plaque volume progression as other traditional factors.ConclusionsThe rate of whole-heart plaque progression and dense calcification increases depending on age. Age is a significant factor in plaque growth, the importance of which is comparable to other traditional risk factors.Clinical trial registrationURL: http://www.clinicaltrials.gov. Unique identifiers: NCT02803411.     

Assessment of computed tomography radiation doses for paediatric head and chest examinations using paediatric phantoms of three different ages

IntroductionWith the rapid development of computed tomography (CT) scanners, the assessment of the radiation dose received by the patient has become a heavily researched topic and may result in a reduction in radiation exposure risk. In this study, radiation doses were measured using three paediatric phantoms for head and chest CT examinations in Najran, Saudi Arabia.MethodsThirteen scanners were included in the study to estimate the CT radiation doses using three phantoms representing three age groups (1-, 5-, and 10-year-old patients).ResultsThe volume CT dose index (CTDI_vol) estimated for each phantom ranged from 6.56 to 41.12 mGy and 0.292 to 11.10 mGy for the head and chest examinations, respectively. The estimation of lifetime attributable risk (LAR) indicated that the cancer risk could reach approximately 0.02–0.16% per 500 children undergoing head and chest CT examinations.ConclusionThe comparison with the published data of the European Commission (EC) and countries reported in this study revealed that the mean CTDI_vol for the head examinations was within the recommended dose reference levels (DRLs). Meanwhile, chest results exceeded the international DRLs for the one-year-old phantoms, suggesting that optimisation work is required at a number of sites.Implications for practiceThe variation among CT doses reported in this study showed that substantial standardisation is needed.     

儿童CT检查诊断参考水平典型值的初步探讨

目的统计以容积CT剂量指数(CTDI_(vol))、基于水当量直径(WD)的体型特异性剂量估算值(SSDEWD)及剂量长度乘积(DLP)为衡量指标的儿童头颅、胸部及腹盆部CT检查诊断参考水平(DRL)典型值,衡量本医疗机构CT检查辐射水平。方法回顾性收集2021年1月至2021年12月间南京医科大学附属儿童医院收治的头颅1391例,胸部1386例及腹盆部1035例患者CT影像资料,分别记录其年龄、CTDI_(vol)、DLP,手动测量最中间扫描图像的前后径(AP)、左右径(LAT)、兴趣区面积(AROI)及面积内CT值(CTROI),按照美国医学物理学家学会(AAPM)报告方法,计算有效直径(d)、WD、转换因子(f16/32XSIZE)及SSDEWD;将各检查部位分别按照年龄及体型进行分组:按照年龄分为<1、1~、5~、10~、15~岁5组,各分组患儿数分别为:头颅252、320、400、380及39例;胸部188、320、399、398及81例;腹盆部75、310、310、300及40例。头颅基于LAT分为<12.5、12.5~、14~、15~、16~cm 5组,每组患儿分别为151、222、319、399及300例;胸部、腹盆部基于d分为<15、15~、20~、25~、30~cm 5组,每组患儿分别为胸部275、527、400、165及19例;腹盆部403、410、184、34及4例。统计各分组内CTDI_(vol)、SSDEWD和DLP的第75百分位数,将其作为DRL典型值;并比较CTDI_(vol)和SSDEWD在衡量辐射剂量上的差异。结果按年龄分组,以CTDI_(vol)为衡量指标的头颅、胸部、腹盆部DRL典型值分别为14.9~24.1、1.8~4.5和2.0~7.5 mGy;以SSDEWD为衡量指标的DRL典型值分别为14.7~18.9、4.2~6.9和4.7~11.8 mGy;以DLP为衡量指标的DRL典型值分别为260~505、40~185和65~435 mGy·cm。按d分组,以CTDI_(vol)为衡量指标的胸部、腹盆部DRL典型值分别为1.8~6.8和2.2~9.2 mGy;以SSDEWD为衡量指标的DRL典型值分别为4.2~9.1和4.9~13.0 mGy;以DLP为衡量指标的DRL典型值分别为40~255和85~545 mGy·cm。头颅按LAT分组,以CTDI_(vol)为衡量指标的DRL典型值为14.1~23.1 mGy;以SSDEWD为衡量指标的DRL典型值为14.3~18.5 mGy;以DLP为衡量指标的DRL典型值为240~475 mGy·cm。头颅除年龄<1岁、LAT<12.5 cm分组外,CTDI_(vol)均大于SSDEWD,头颅CTDI_(vol)为(18.63±3.24)mGy,SSDEWD为(16.38±1.81)mGy,差异有统计学意义(t=48.78,P<0.001);胸部、腹盆部各分组CTDI_(vol)均小于SSDEWD,胸部CTDI_(vol)为(2.77±1.02)mGy,SSDEWD为(5.22±1.26)mGy,差异有统计学意义(t=-210.89,P<0.001);腹盆部CTDI_(vol)为(3.36±1.82)mGy,SSDEWD为(6.27±2.44)mGy,差异亦有统计学意义(t=-115.16,P<0.001)。结论本医疗机构DRL典型值与其他国家相比处于合理且较低水平,SSDEWD较CTDI_(vol)能更准确反映辐射剂量,亟需建立基于SSDEWD的DRLs。     

Effect of iterative reconstruction algorithms on peripheral MDCT angiography virtual histology plaque volumes: have we been overestimating disease burden?

Our objective was to compare plaque volumes of multidetector computed tomographic images reconstructed using adaptive statistical iterative reconstruction (ASIR), model-based iterative reconstruction (MBIR), and filtered back projection (FBP). We reviewed 25 patients for a total of 50 extremities imaged on the same scanner. Calcified plaque FBP volume (3468.2±2634.8 mm³) was higher than ASIR (2548.1±2166.5 mm³). Calcified plaque FBP volume was higher than MBIR (mean=2345.7±1935.4 mm³). Our findings suggest that traditional FBP methods overestimate disease compared to newer reconstruction methods.     

Reproducibility of quantitative plaque measurement in advanced coronary artery disease

BackgroundThe ability to characterize and to quantify the extent of coronary artery disease has the potential to improve the prognostic capability of coronary computed tomography angiography. Although reproducible techniques have been described in those with mild coronary disease, this has yet to be assessed in patients with advanced disease.MethodsTwenty patients with known multivessel disease underwent repeated computed tomography coronary angiography, 2 weeks apart. Coronary artery segments were analysed using semi-automated software by two trained observers to determine intraobserver, interobserver and interscan reproducibility.ResultsOverall, 149 coronary arterial segments were analysed. There was excellent intraobserver and interobserver agreement for all plaque volume measurements (Lin’s coefficient 0.95 to 1.0). There were no substantial interscan differences (P ?> ?0.05 for all) for total (2063 ?± ?1246 ?mm³, mean of differences ?35.6 ?mm³), non-calcified (1795 ?± ?910 ?mm³, mean of differences ?4.3 ?mm³), calcified (298 ?± ?425 ?mm³, mean of differences ?31.3 ?mm³) and low-attenuation (13 ?± ?13 ?mm³, mean of differences ?2.6 ?mm³) plaque volumes. Interscan agreement was highest for total and noncalcified plaque volumes. Calcified and low-attenuation plaque (?236.6 to 174 ?mm³ and -15.8 to 10.5 ?mm³ respectively) had relatively wider 95% limits of agreement reflecting the lower absolute plaque volumes.ConclusionIn the presence of advanced coronary disease, semi-automated plaque quantification provides excellent reproducibility, particularly for total and non-calcified plaque volumes. This approach has major potential to assess change in disease over time and optimize risk stratification in patients with established coronary artery disease.     

Ultralow-dose CT with tin filtration for detection of solid and sub solid pulmonary nodules: a phantom study

Objectives:

To investigate the diagnostic performance of advanced modelled iterative reconstruction (ADMIRE) to filtered back projection (FBP) when using an ultralow-dose protocol for the detection of solid and subsolid pulmonary nodules.

Methods:

Single-energy CT was performed at 100 kVp with tin filtration in an anthropomorphic chest phantom with solid and subsolid pulmonary nodules (2–10 mm, attenuation, 20 to −800 HU at 120 kVp). The mean volume CT dose index (CTDI_vol) of the standard chest protocol was 2.2 mGy. Subsequent scans were obtained at 1/8 (0.28 mGy), 1/20 (0.10 mGy) and 1/70 (0.03 mGy) dose levels by lowering tube voltage and tube current. Images were reconstructed with FBP and ADMIRE. One reader measured image noise; two readers determined image quality and assessed nodule localization.

Results:

Image noise was significantly reduced using ADMIRE compared with FBP (ADMIRE at a strength level of 5 : 70.4% for 1/20; 71.6% for 1/8; p < 0.001). Interobserver agreement for image quality was excellent (k = 0.88). Image quality was considered diagnostic for all images at 1/20 dose using ADMIRE. Sensitivity of nodule detection was 97.1% (100% for solid, 93.8% for subsolid nodules) at 1/20 dose and 100% for both nodule entities at 1/8 dose using ADMIRE 5. Images obtained with 1/70 dose had moderate sensitivity (overall 85.7%; solid 95%; subsolid 73.3%).

Conclusion:

Our study suggests that with a combination of tin filtration and ADMIRE, the CTDI_vol of chest CT can be lowered considerably, while sensitivity for nodule detection remains high. For solid nodules, CTDI_vol was 0.10 mGy, while subsolid nodules required a slightly higher CTDI_vol of 0.28 mGy.

Advances in knowledge:

Detection of subsolid nodules is feasible with ultralow-dose protocols.