Standardizing Methods of Reading CT Maximum Aortic Diameters Amongst Experts Reduces Variations and Discordance, Improving Accuracy.

BACKGROUND: There is no consensus on the method of obtaining abdominal aortic aneurysm (AAA) maximum diameters based on computed tomographic angiography, and the reproducibility and accuracy of different methods have recently been debated due to advancements in imaging. This study compared the two most common methods based on orthogonal planes and centerline of flow to determine the discordances and accuracy amongst experiences readers. METHODS: The computed tomographic angiography max diameters of 148 AAAs were measured by three experienced observers, including a vascular surgeon, a radiologist and an imaging cardiologist. Observers used two different methods with standardized protocols: multiplanar reformations based on orthogonal planes, and a software using 3D aortic reconstructions to create centerline flow lumen providing diameters based on cross sections perpendicular to this lumen. Agreements and reliability of measurement methods were assessed by intra-class correlation coefficient and Bland - Altman analysis. Discordances between measurements of the methods and the original reported measurement, as well as outside hospitals were compared. RESULTS: The average age of the cohort was 75 years and aortic diameters ranged from 3.8 to 9.6 cm. For orthogonal readings, there were agreements within 3 mm between 86% and 92% of the time, while centerline - reading agreement was between 88% and 94%, which was not statistically significant. The intra-class correlation coefficient was high between method type and between readers. Within methods, agreement was between 0.96 and 0.97, while within - reader agreement measures was between 0.96 and 0.98. In comparison to the original and the outside hospital reports, 10% ≥ of the original and 20% ≥ of the outside hospital reported measurements were discordant between the readers. CONCLUSION: Maximal AAA measurements can have substantial variability leading to clinical significance and change in patient management and outcomes. Based on the results, orthogonal and centerline measurement methods have equally high agreements and concordance within 3 mm and low variations at a high volume center. However, when compared to the official read reports, there is high discordance rates that can significantly alter patient outcomes. A standardized method of measurement maximum diameter can reduce variations and discordances among different methods.

Standardization of a Carbon Dioxide Automated System for Endovascular Aortic Aneurysm Repair.

BACKGROUND: Endovascular aortic repair (EVAR) is presently the preferred treatment for abdominal aortic aneurysm; however, it requires the injection of a contrast medium, which can hamper the renal function. Other nontoxic agents such as carbon dioxide (CO2) have been sporadically tested in this setting with uncertain results. The aim of the study is to investigate the efficacy of a new standardized CO2 injection method in standard EVAR procedures. METHODS: Between August and October 2016, 31 consecutive patients (median age 76.1 [interquartile range {IQR}: 7.4] years) were submitted to standard EVAR. Proximal and distal endograft landing zones were identified by the injection of 100 mL of CO2 at 300 mm Hg, through an 11 cm 10F femoral sheath by a specifically manufactured automated injection device (Angiodroid Srl, San Lazzaro, Bologna, Italy). Before EVAR deployment, a confirmative injection with a conventional contrast medium was accomplished. The possibility of precisely visualizing the proximal and distal landing zones by CO2 digital subtraction angiography (DSA) was evaluated considering the contrast medium injection obtained in the same procedure as a gold standard. Similarly, the possible presence of endoleak was assessed at the end of the procedure by the 2 techniques. RESULTS: CO2 DSA allowed to identify the juxtarenal landing zone of the endograft in 19/31 cases (61%) and the distal one in 31/31 (100%). In 12 (39%) cases, CO2 injection failed to visualize at least the lowest renal artery. This occurred in large aneurysms with scarce thrombotic apposition and a luminal volume greater than 95.9 (IQR: 25.2) mm3. Completion CO2 DSA detected type II endoleaks (ELIIs) in 10 cases compared with 2 of conventional contrast media. CONCLUSIONS: The injection of nontoxic CO2 through an automated device allowed to perform EVAR procedures effectively, in the majority of cases. In some cases, a single injection of a minimum amount of conventional contrast medium can be used to overcome the lack of renal artery visualization by CO2. ELIIs are more frequently visualized with CO2 compared with standard contrast medium. Although the CO2 injection technique needs further amelioration particularly in the renal arteries detection, this technique appears promising and possibly substitutive of the standard contrast medium, with significant benefit for the renal function.

Radiation dose during endovascular aneurysm repair (EVAR): upgrade of an angiographic system from standard to Eco mode.

PURPOSE: To evaluate the radiation dose reduction during endovascular aneurysm repair (EVAR) after the reconfiguration of a Philips AlluraXper FD20 X-ray system. METHODS: Between 2013 and 2015, we implemented a low-dose protocol (Eco dose) increasing the filtration with 1 mm of Al and 0.1 of Cu on both fluoroscopy and fluorography and halving the frames per second in fluoroscopy. The switch was complemented by hybrid operating room staff education and training in radiation protection. We compared two samples of 50 patients treated before the switch (normal dose) with 50 patients treated after the switch (Eco dose). Procedures were categorized into two different grades of complexity, standard and complex, intended as fenestrated/chimney/snorkel and EVAR plus additional embolization to prevent endoleak type II. We evaluated patient demographics, Air Kerma (AK), dose area product (DAP), and procedural data (fluoroscopy time, number of fluorographies, and iodinated contrast). Staff radiation dose was measured with film badge dosimeter on C-arm. RESULTS: The Eco-dose protocol witnessed a DAP reduction of 53% in standard EVARs and of 57% in complex EVARs and an AK reduction of 45% in standard and 57% in complex EVAR. The image quality in 2016 was perceived acceptable, as proven by the fact that fluoroscopy time, number of fluorographies, and contrast medium volumes did not have to be increased. We achieved a reduction in staff dose of 25.6%. CONCLUSIONS: Optimized angiographic system setting significantly reduced the radiation dose both to the patients and to the staff assuring safe EVAR procedures.

The Impact of Compliance with Imaging Follow-up on Mortality After Endovascular Abdominal Aortic Aneurysm Repair: A Population Based Cohort Study.

OBJECTIVE: Compliance with regular imaging follow-up after endovascular aortic aneurysm repair (EVAR) is inconsistent, and evidence of benefit from scheduled long-term surveillance is limited. This study sought to characterize the association between post-EVAR imaging frequency and long-term survival. METHODS: Using administrative health databases for the province of Ontario, Canada, a cohort of patients was identified who underwent EVAR between 2004 and 2014. Minimum appropriate imaging follow-up (MAIFU) was defined as a CT scan or ultrasound of the abdomen within 90 days of EVAR as well as every 15 months thereafter. Multivariate time to event analyses characterized the association between compliance with MAIFU over time and all-cause mortality. RESULTS: 4988 patients treated by EVAR were identified. Median follow-up was 3.4 years (IQR 2.0-5.3 years) and 90 day mortality was 1.6%. Among those who survived over 90 days, 87% (N = 4251 of 4902) underwent at least one CT scan or ultrasound of the abdomen within 90 days, but only 58% (N = 2859 of 4902) went on to meet MAIFU criteria. Infrequent imaging correlated with lower follow-up by a vascular surgeon, but not with infrequent primary care or specialist consultations. Consistently meeting MAIFU criteria was associated with a lower risk of death when compared with missing the first imaging follow-up within 90 days (HR 0.82, 95% CI 0.69-0.96, p = .014), or when compared with having first imaging follow-up within 90 days but subsequently not meeting MAIFU criteria (HR 0.78, 95% CI 0.68-0.91, p = .001). A larger proportion of the follow-up period meeting MAIFU criteria was associated with a lower risk of death. CONCLUSIONS: These data support efforts to improve compliance with imaging surveillance after EVAR.

Compliance of postendovascular aortic aneurysm repair imaging surveillance.

OBJECTIVE: Imaging surveillance after endovascular aortic aneurysm repair (EVAR) is critical. In this study we analyzed compliance with imaging surveillance after EVAR and its effect on clinical outcomes. METHODS: Retrospective analysis of prospectively collected data of 565 EVAR patients (August 2001-November 2013), who were followed using duplex ultrasound and/or computed tomography angiography. Patients were considered noncompliant (NC) if they did not have any follow-up imaging for 2 years and/or missed their first post-EVAR imaging over 6 months. A Kaplan-Meier analysis was used to compare compliance rates in EVAR patients with hostile neck (HN) vs favorable neck (FN) anatomy (according to instructions for use). A multivariate analysis was also done to correlate compliance and comorbidities. RESULTS: Forty-three percent were compliant (7% had no follow-up imaging) and 57% were NC. The mean follow-up for compliant patients was 25.4 months (0-119 months) vs 31.4 months for NC (0-140 months). The mean number of imaging was 3.5 for compliant vs 2.6 for NC (P < .0001). Sixty-four percent were NC for HN patients vs 50% for FN patients (P = .0007). The rates of compliance at 1, 2, 3, 4, and 5 years for all patients were 78%, 63%, 55%, 45%, and 32%; and 84%, 68%, 61%, 54%, and 40% for FN patients; and 73%, 57%, 48%, 37%, and 25% for HN patients (P = .009). The NC rate for patients with late endoleak and/or sac expansion was 58% vs 54% for patients with no endoleak (P = .51). The NC rate for patients with late reintervention was 70% vs 53% for patients with no reintervention (P = .1254). Univariate and multivariate analyses showed that patients with peripheral arterial disease had an odds ratio of 1.9 (P = .0331), patients with carotid disease had an odds ratio of 2 (P = .0305), and HN patients had an odds ratio of 1.8 (P = .0007) for NC. Age and residential locations were not factors in compliance. CONCLUSIONS: Overall, compliance of imaging surveillance after EVAR was low, particularly in HN EVAR patients, and additional studies are needed to determine if strict post-EVAR surveillance is necessary, and its effect on long-term clinical outcome.

Standardized Protocol to Analyze Computed Tomography Imaging of Type B Aortic Dissections.

PURPOSE: To propose a standard measuring protocol for type B aortic dissections so as to improve comparability between studies reporting aortic dimensions. METHODS: Fifteen computed tomography (CT) scans of type B aortic dissections were measured with a standard protocol by 2 independent observers using postprocessing software. The following parameters were assessed: true, false, and total lumen diameter; true and false lumen volume; and entry tear size, location, and number. Diameters were measured in a perpendicular plane at 2, 10, and 20 cm from the left subclavian artery and 5 cm from the most distal renal artery. True lumen volume was assessed from the left subclavian artery to the aortic bifurcation, while the false lumen volume was from the start to end up to the aortic bifurcation. Entry tear location was assessed in relation to the left subclavian artery. Intra- and interobserver repeatability and agreement were evaluated using the Bland-Altman method, an a priori set of acceptable differences, and Lin's concordance correlation coefficient (LCCC). RESULTS: Intra- and interobserver mean differences for aortic diameter and true and false lumen volumes were generally within the limits of agreement and the a priori differences; the LCCC showed excellent agreement. Entry tear location, size, and number were difficult to measure in a repeatable manner, with inconsistent correlation coefficients, especially between the 2 observers. CONCLUSION: This protocol showed acceptable repeatability for aortic diameter and aortic volume measurements. Assessment of entry tears proved challenging and associated with less favorable results. Additionally, investigators are urged to be more transparent regarding the measurement methodology used in studies describing aortic dimensions.

Imaging After Nellix Endovascular Aneurysm Sealing: A Consensus Document.

Endovascular aneurysm sealing (EVAS) using the Nellix system is a new and different method of abdominal aortic aneurysm repair. Normal postoperative imaging has unique appearances that change with time; complications also have different and specific appearances. This consensus document on the imaging findings after Nellix EVAS is based on the collective experience of the sites involved in the Nellix EVAS Global Forward Registry and the US Investigational Device Exemption Trial. The normal findings on computed tomography (CT), duplex ultrasound, magnetic resonance imaging, and plain radiography are described. With time, endobag appearances change on CT due to contrast migration to the margins of the hydrogel polymer within the endobag. Air within the endobag also has unique appearances that change over time. Among the complications after Nellix EVAS, type I endoleak usually presents as a curvilinear area of flow between the endobag and aortic wall, while type II endoleak is typically small and usually occurs where an aortic branch artery lies adjacent to an irregular aortic blood lumen that is not completely filled by the endobag. Procedural aortic injury is an uncommon but important complication that occurs as a result of overfilling of the endobags during Nellix EVAS. The optimum imaging surveillance algorithm after Nellix EVAS has yet to be defined but is largely CT-based, especially in the first year postprocedure. However, duplex ultrasound also appears to be a sensitive modality in identifying normal appearances and complications.

Diagnosis of Aortic Graft Infection: A Case Definition by the Management of Aortic Graft Infection Collaboration (MAGIC).

OBJECTIVE/BACKGROUND: The management of aortic graft infection (AGI) is highly complex and in the absence of a universally accepted case definition and evidence-based guidelines, clinical approaches and outcomes vary widely. The objective was to define precise criteria for diagnosing AGI. METHODS: A process of expert review and consensus, involving formal collaboration between vascular surgeons, infection specialists, and radiologists from several English National Health Service hospital Trusts with large vascular services (Management of Aortic Graft Infection Collaboration [MAGIC]), produced the definition. RESULTS: Diagnostic criteria from three categories were classified as major or minor. It is proposed that AGI should be suspected if a single major criterion or two or more minor criteria from different categories are present. AGI is diagnosed if there is one major plus any criterion (major or minor) from another category. (i) Clinical/surgical major criteria comprise intraoperative identification of pus around a graft and situations where direct communication between the prosthesis and a nonsterile site exists, including fistulae, exposed grafts in open wounds, and deployment of an endovascular stent-graft into an infected field (e.g., mycotic aneurysm); minor criteria are localized AGI features or fever ≥38°C, where AGI is the most likely cause. (ii) Radiological major criteria comprise increasing perigraft gas volume on serial computed tomography (CT) imaging or perigraft gas or fluid (≥7 weeks and ≥3 months, respectively) postimplantation; minor criteria include other CT features or evidence from alternative imaging techniques. (iii) Laboratory major criteria comprise isolation of microorganisms from percutaneous aspirates of perigraft fluid, explanted grafts, and other intraoperative specimens; minor criteria are positive blood cultures or elevated inflammatory indices with no alternative source. CONCLUSION: This AGI definition potentially offers a practical and consistent diagnostic standard, essential for comparing clinical management strategies, trial design, and developing evidence-based guidelines. It requires validation that is planned in a multicenter, clinical service database supported by the Vascular Society of Great Britain & Ireland.

Cardiovascular magnetic resonance reference ranges for the heart and aorta in Chinese at 3T.

BACKGROUND: Cardiovascular magnetic resonance (CMR) reference ranges have not been well established in Chinese. Here we determined normal cardiac and aortic reference ranges in healthy Singaporean Chinese and investigated how these data might affect clinical interpretation of CMR scans. METHODS: In 180 healthy Singaporean Chinese (20 to 69 years old; males, n = 91), comprehensive cardiac assessment was performed using the steady state free precision technique (3T Ingenia, Philips) and images were analysed by two independent observers (CMR42, Circle Cardiovascular Imaging). Measurements were internally validated using standardized approaches: left ventricular mass (LVM) was measured in diastole and systole (with and without papillary muscles) and stroke volumes were compared in both ventricles. All reference ranges were stratified by sex and age; and "indeterminate/borderline" regions were defined statistically at the limits of the normal reference ranges. Results were compared with clinical measurements reported in the same individuals. RESULTS: LVM was equivalent in both phases (mean difference 3.0 ± 2.5 g; P = 0.22) and stroke volumes were not significantly different in the left and right ventricles (P = 0.91). Compared to females, males had larger left and right ventricular volumes (P < 0.001 for all). Indexed LVM was significantly higher in males compared to females (50 ± 7 versus 38 ± 5 g/m2, respectively; P < 0.001). Overall, papillary muscles accounted for only ~2% of the total LVM. Indexed atrial sizes and aortic root dimensions were similar between males and females (P > 0.05 for all measures). In both sexes, age correlated negatively with left and right ventricular volumes; and positively with aortic sinus and sinotubular junction diameters (P < 0.0001 for all). There was excellent agreement in indexed stroke volumes in the left and right ventricles (0.1±5.7 mL/m2, 0.7±6.2 mL/m2, respectively), LVM (0.6±6.4 g/m2), atrial sizes and aortic root dimensions between values reported in clinical reports and our measured reference ranges. CONCLUSIONS: Comprehensive sex and age-corrected CMR reference ranges at 3T have been established in Singaporean Chinese. This is an important step for clinical practice and research studies of the heart and aorta in Asia.

Preoperative predictive factors of aneurysmal regression using the reporting standards for endovascular aortic aneurysm repair.

BACKGROUND: Aneurysmal regression is a reliable marker for long-lasting success after endovascular aneurysm repair (EVAR). The aim of this study was to identify the preoperative factors that can predictably lead to aneurysmal sac regression after EVAR, according to the reporting standards of the Society for Vascular Surgery and the International Society of Cardiovascular Surgery (SVS/ISCVS). METHODS: From 199 patients treated by EVAR between 2000 and 2009, 164 completed computed tomography angiographies and duplex scan follow-up images were available. All computed tomography angiographies for enrolled patients in this retrospective study were analyzed with Endosize software (Therenva, Rennes, France) to provide spatially correct 3-dimensional data in accordance with SVS/ISCVS recommendations. Anatomic parameters were graded according to the relevant severity grades. A severity score was calculated at the aortic neck, the abdominal aortic aneurysm, and the iliac arteries. Clinical and demographic factors were studied. Patients with aneurysmal regression >5 mm were assigned to group A (mean age, 71.4 ± 8.9 years) and the others to group B (76.3 ± 8.3 years). RESULTS: Aneurysmal regression occurred in 66 patients (40.2%; group A). Univariate analyses showed smaller severity scores at the aortic neck (P = .02) and the iliac arteries (P = .002) in group A and calcifications and thrombus were less significant at the aortic neck (P = .003 and P = .02) and at the iliac arteries (P = .001 and P = .02), and inferior mesenteric artery patency was less frequent (68.2% vs 82.7%, P = .04). Two multivariate analyses were done: one considered the scores and the other the variables included in the scores. In the first, the patients of group A were younger (P = .002) and aortic neck calcifications were less significant (P = .007). In the second, group A patients were younger (P < .001) and the aortic neck scores were smaller (P = .04). There was no difference between the two groups in the type of implanted endoprosthesis or in the follow-up (group A: 46.4 ± 24 months; group B: 47.2 ± 22 months; P = .35). CONCLUSIONS: In this study, the young age of the patients and their aortic neck quality, in particular the absence of neck calcification, appear to have been the main factors affecting aneurysm shrinkage, such that they represent a target population for the improvement of EVAR results.

Correlation of CT aortography measurements of infrarenal aortic aneurysms and body mass index in preprocedural evaluation for endovascular repair.

The aim of this study is to analyze the morphological differences of infrarenal aortic aneurysms and common iliac arteries that are important for endovascular management between patients of different body mass index using 64 slice multidetector row CT aortography. This was a multicenter study of 100 patients (50 Europeans and 50 Japanese). All patients had risk factors, manifest symptoms, and ultrasound verified aneurysmal dilation of the infrarenal aorta. All examinations were performed on the same CT platform using the same post-processing protocols. Due to the heterogeneity of the population, several statistical models were used. Significant differences were found in morphological parameters of infrarenal aorta in relation to BMI. In over one out of three patients with BMI less than 23, endovascular treatment is contraindicated due to the dimensions of the aneurysmal neck. Relative to BMI value, differences were found in transverse diameters of the medium part of the aneurysm and in the length of common iliac arteries. CT aortography performed on a 64 slice multidetector row CT platform provides precise and numerous data for the analysis of anatomical and pathological differences of infrarenal aortic aneurysms that are of crucial importance for the planning of treatment and the analysis of the differences relating to body habitus.

Validation of a new standardized method to measure proximal aneurysm neck angulation.

PURPOSE: This study presented and validated a new standardized method for the measurement of the aortic angulation in patients with abdominal aortic aneurysms (AAA) and quantified the observer variability. METHODS: A standardized method to quantify aortic angulation was introduced. To measure aortic angulation, a center lumen line (CLL) of the aorta was made, and a three-dimensional (3D) aortic reconstruction was obtained. The 3D reconstruction was turned 360 degrees perpendicular to the CLL in the middle of the flexure. The sharpest angle of the CLL was considered the true angle of the aortic axis. The computed tomography angiography data sets of 20 patients scheduled for endovascular aneurysm repair (EVAR) were obtained. The angles between the suprarenal aorta and the aneurysm neck (alpha) and between the aneurysm neck and sac (beta) were measured. Two observers independently measured the angles. Differences of each pair of measurements were plotted against their mean and intraobserver and interobserver variabilities were calculated according to Bland and Altman. RESULTS: The intraobserver mean difference for angle alpha was -0.2 degrees (-0.5%), with a repeatability coefficient (RC) of 6.4 degrees (20.2%), and 0.6 degrees (1.4%) for angle beta, with a RC of 6.2 degrees (13.4%). The interobserver mean difference for angle alpha was -1.5 degrees (-4.5%), with a RC of 6.9 degrees (22.0%), and -0.2 degrees (-0.4%) for angle beta, with a RC of 7.4 degrees (16.0%). No significant differences were observed between the observers. CONCLUSION: The presented technique to objectively quantify the angulation of the aneurysm neck is easy to perform and reliable. This method showed good intraobserver and interobserver variability and should therefore be the standard when measuring and reporting aortic angulation.

Three-dimensional imaging core laboratory of the endovascular aneurysm repair trials: validation of methodology.

OBJECTIVE: The aim of this study was to establish and validate a three-dimensional imaging protocol for the assessment of Computed Tomography (CT) scans of abdominal aortic aneurysms in UK EVAR trials patients. Quality control and repeatability of anatomical measurements is important for the validity of any core laboratory. METHODS: Three different observers performed anatomical measurements on 50 preoperative CT scans of aortic aneurysms using the Vitrea 2 three-dimensional post-imaging software in a core laboratory setting. We assessed the accuracy of intra and inter observer repeatability of measurements, the time required for collection of measurements, 3 different levels of automation and 3 different automated criteria for measurement of neck length. RESULTS: None of the automated neck length measurements demonstrated sufficient accuracy and it was necessary to perform checking of the important automated landmarks. Good intra and limited inter observer agreement were achieved with three-dimensional assessment. Complete assessment of the aneurysm and iliacs took an average (SD) of 17.2 (4.1) minutes. CONCLUSIONS: Aortic aneurysm anatomy can be assessed reliably and quickly using three-dimensional assessment but for scans of limited quality, manual checking of important landmarks remains necessary. Using a set protocol, agreement between observers is satisfactory but not as good as within observers.

Effect of automated tube voltage selection, integrated circuit detector and advanced iterative reconstruction on radiation dose and image quality of 3rd generation dual-source aortic CT angiography: An intra-individual comparison.

PURPOSE: To compare, on an intra-individual basis, the effect of automated tube voltage selection (ATVS), integrated circuit detector and advanced iterative reconstruction on radiation dose and image quality of aortic CTA studies using 2nd and 3rd generation dual-source CT (DSCT). MATERIAL AND METHODS: We retrospectively evaluated 32 patients who had undergone CTA of the entire aorta with both 2nd generation DSCT at 120kV using filtered back projection (FBP) (protocol 1) and 3rd generation DSCT using ATVS, an integrated circuit detector and advanced iterative reconstruction (protocol 2). Contrast-to-noise ratio (CNR) was calculated. Image quality was subjectively evaluated using a five-point scale. Radiation dose parameters were recorded. RESULTS: All studies were considered of diagnostic image quality. CNR was significantly higher with protocol 2 (15.0±5.2 vs 11.0±4.2; p<.0001). Subjective image quality analysis revealed no significant differences for evaluation of attenuation (p=0.08501) but image noise was rated significantly lower with protocol 2 (p=0.0005). Mean tube voltage and effective dose were 94.7±14.1kV and 6.7±3.9mSv with protocol 2; 120±0kV and 11.5±5.2mSv with protocol 1 (p<0.0001, respectively). CONCLUSION: Aortic CTA performed with 3rd generation DSCT, ATVS, integrated circuit detector, and advanced iterative reconstruction allow a substantial reduction of radiation exposure while improving image quality in comparison to 120kV imaging with FBP.

The Need for Standardized Methods for Measuring the Aorta: Multimodality Core Lab Experience From the GenTAC Registry.

OBJECTIVES: This study sought to evaluate variability in aortic measurements with multiple imaging modalities in clinical centers by comparing with a standardized measuring protocol implemented in a core laboratory. BACKGROUND: In patients with aortic disease, imaging of thoracic aorta plays a major role in risk stratifying individuals for life-threatening complications and in determining timing of surgical intervention. However, standardization of the procedures for performance of aortic measurements is lacking. METHODS: To characterize the diversity of methods used in clinical practice, we compared aortic measurements performed by echocardiography, computed tomography (CT), and magnetic resonance imaging (MRI) at the 6 GenTAC (National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions) clinical centers to those performed at the imaging core laboratory in 965 studies. Each center acquired and analyzed their images according to local protocols. The same images were subsequently analyzed blindly by the core laboratory, on the basis of a standardized protocol for all imaging modalities. Paired measurements from clinical centers and core laboratory were compared by mean of differences and intraclass correlation coefficient (ICC). RESULTS: For all segments of the ascending aorta, echocardiography showed a higher ICC (0.84 to 0.93) than CT (0.84) and MRI (0.82 to 0.90), with smaller mean of differences. MRI showed higher ICC for the arch and descending aorta (0.91 and 0.93). In a mixed adjusted model, the different imaging modalities and clinical centers were identified as sources of variability between clinical and core laboratory measurements, whereas age groups or diagnosis at enrollment were not. CONCLUSIONS: By comparing core laboratory with measurements from clinical centers, our study identified important sources of variability in aortic measurements. Furthermore, our findings with regard to CT and MRI suggest a need for imaging societies to work toward the development of unifying acquisition protocols and common measuring methods.