Aortic Diameter Measurements Research Articles

Ultrasound Measurement of Aortic Diameter in a National Screening Programme

Ultrasound Measurement of Aortic Diameter in a National Screening Programme

Single breathhold noncontrast thoracic MRA using highly accelerated parallel imaging with a 32‐element coil array

To evaluate the feasibility of performing single breathhold three-dimensional (3D) thoracic noncontrast MR angiography (NC-MRA) using highly accelerated parallel imaging. We developed a single breathhold NC MRA pulse sequence using balanced steady state free precession (SSFP) readout and highly accelerated parallel imaging. In 17 subjects, highly accelerated noncontrast MRA was compared against electrocardiogram-triggered contrast-enhanced MRA. Anonymized images were randomized for blinded review by two independent readers for image quality, artifact severity in eight defined vessel segments and aortic dimensions in six standard sites. NC-MRA and CE-MRA were compared in terms of these measures using paired sample t- and Wilcoxon tests. The overall image quality (3.21 ± 0.68 for NC-MRA versus 3.12 ± 0.71 for CE-MRA) and artifact (2.87 ± 1.01 for NC-MRA versus 2.92 ± 0.87 for CE-MRA) scores were not significantly different, but there were significant differences for the great vessel and coronary artery origins. NC-MRA demonstrated significantly lower aortic diameter measurements compared with CE-MRA; however, this difference was not considered clinically relevant (>3 mm difference) for less than 12% of segments, most commonly at the sinotubular junction. Mean total scan time was significantly lower for NC-MRA compared with CE-MRA (18.2 ± 6.0 s versus 28.1 ± 5.4 s, respectively; P < 0.05). Single breathhold NC-MRA is feasible and can be a useful alternative for evaluation and follow-up of thoracic aortic diseases.

Single-centre Prospective Comparison Between Contrast-Enhanced Ultrasound and Computed Tomography Angiography after EVAR

To evaluate contrast-enhanced ultrasound (CEUS) as an effective alternative to CT-angiography (CTA) for endoleak detection and aneurismal sac diameter measurement in the follow-up after endovascular abdominal aortic aneurysm repair (EVAR). From January 2006 to December 2010, 395 patients underwent EVAR follow-up with both CTA and CEUS. The diameter of the aneurismal sac and the presence of endoleaks were evaluated in all the 395 paired examinations. Bland–Altman plots showed a good agreement in aneurismal sac diameter evaluation between the two imaging modalities. The mean diameter was 54.93 mm (standard deviation (SD) ±12.57) with CEUS and 56.01 mm (SD ± 13.23) with CTA. The mean difference in aneurismal sac diameter was −1.08 mm ± 3.3543 (95% confidence interval (CI), −0.75 to −1.41), in favour of CTA. The number of observed agreement in endoleak detection was 359/395 (90.89%). The two modalities detected the same type I and type III endoleaks. McNemar’s χ2 test confirmed that CTA and CEUS are equivalent in endoleak detection. CEUS demonstrated to be as accurate as CTA in endoleak detection and abdominal aortic aneurysm diameter measurements during EVAR follow-up, without carrying the risks of radiation exposure or nephrotoxicity. Even if it cannot be proposed as the sole imaging modality during follow-up, our analysis suggests that it should have a major role.

Preliminary intraobserver and interobserver variability in wall stress and rupture risk assessment of abdominal aortic aneurysms using a semiautomatic finite element model

We investigated the intraobserver and interobserver variability of using semiautomatic finite element analysis to calculate the von Mises stress and peak wall rupture risk (PWRR) in patients with an abdominal aortic aneurysm (AAA) in longitudinal studies. Four independent observers made 3-dimensional (3D) reconstructions, with minimal manual adjustments, of small AAAs (<5.0 cm) in 17 patients and processed finite element analysis. We used semiautomatic diagnostic software with a finite element model (A4research, VASCOPS GmbH, Graz, Austria). The finite element method was used to calculate von Mises stress and PWRR, which are indicators for wall stress. The differences of each pair of measurements of von Mises stress and PWRR were plotted against their mean and the difference of the mean, according to Bland-Altman analysis. The intraobserver variability had an overall mean percentage difference of 6.86% ± 6.46% for the von Mises stress and 7.70% ± 6.26% for PWRR. The interobserver variability for the four observers showed an overall mean percentage difference of 7.09% ± 6.16% for the von Mises stress and 9.47% ± 8.18% for the PWRR measurement. No significant differences were found (P < .05), for the von Mises stress and PWRR for all observers. The von Mises stress and PWRR of small AAAs calculated in this semiautomatic finite element analysis program show good interobserver and intraobserver variability. It is suitable for clinical use to evaluate mechanical aortic wall characteristics and to compare it with other current methods such as maximum aortic diameter measurements.

Increased Aortic Root Size is Associated with Nocturnal Hypoxia and Diastolic Blood Pressure in Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is known as a major cardiovascular risk factor, and high prevalence of OSA has been reported in patients with thoracic aortic dissection. The aim of our study was to assess the relationship between OSA, its vascular consequences, and aortic root size. 156 newly diagnosed apneic patients free of cardiovascular disease and medication were included. Patients underwent cardiac ultrasound for measuring aortic root diameter, polysomnography, office and 24-h ambulatory blood pressure (BP) measurements, baroreflex sensitivity (BRS), and arterial stiffness evaluation by carotid-to-femoral pulse wave velocity (PWV). In univariate analysis, greater aortic root size was associated with older age (P = 0.03) and severity of OSA as expressed by mean nocturnal oxygen saturation (SpO2) (P = 0.015). Moreover, greater aortic root size was associated with higher diastolic BP, measured both clinically (P = 0.0005) or by 24-h ambulatory BP monitoring (P = 0.02), and PWV (P = 0.03). Mean nocturnal SpO(2) was correlated with BRS (P = 0.0008), thus potentially influencing BP values and arterial stiffness. In multivariate stepwise regression analysis, diastolic BP was the only significant factor for aortic root size (P = 0.0003). In OSA patients, nocturnal hypoxemia decreased BRS and increased diastolic BP, which was the main factor influencing aortic root size.

Single-centre Prospective Comparison Between Contrast-Enhanced Ultrasound and Computed Tomography Angiography after EVAR

Aim To evaluate contrast-enhanced ultrasound (CEUS) as an effective alternative to CT-angiography (CTA) for endoleak detection and aneurismal sac diameter measurement in the follow-up after endovascular abdominal aortic aneurysm repair (EVAR). Methods From January 2006 to December 2010, 395 patients underwent EVAR follow-up with both CTA and CEUS. The diameter of the aneurismal sac and the presence of endoleaks were evaluated in all the 395 paired examinations. Results Bland–Altman plots showed a good agreement in aneurismal sac diameter evaluation between the two imaging modalities. The mean diameter was 54.93 mm (standard deviation (SD) ±12.57) with CEUS and 56.01 mm (SD ± 13.23) with CTA. The mean difference in aneurismal sac diameter was −1.08 mm ± 3.3543 (95% confidence interval (CI), −0.75 to −1.41), in favour of CTA. The number of observed agreement in endoleak detection was 359/395 (90.89%). The two modalities detected the same type I and type III endoleaks. McNemar’s χ 2 test confirmed that CTA and CEUS are equivalent in endoleak detection. Conclusions CEUS demonstrated to be as accurate as CTA in endoleak detection and abdominal aortic aneurysm diameter measurements during EVAR follow-up, without carrying the risks of radiation exposure or nephrotoxicity. Even if it cannot be proposed as the sole imaging modality during follow-up, our analysis suggests that it should have a major role.

Invited Commentary

Invited Commentary

Reproducibility of ultrasound measurement of the abdominal aorta

Abdominal aortic aneurysm (AAA) screening and surveillance programmes use ultrasound imaging to measure the anteroposterior (AP) diameter of the infrarenal aorta. The aim of this study was to examine potential observer bias and variability in ultrasound measurements. Studies were identified for review via a MEDLINE database search (1966-2009). References supplied in accessed papers were also checked for potential relevance. Consistent search terminology, and inclusion and exclusion criteria were used to ensure quality of data. Nine papers were available to review. Variation in intraobserver repeatability and interobserver reproducibility was identified. Six studies reported intraobserver repeatability coefficients for AP aortic diameter measurements of 1·6-4·4 mm. These were below the 5-mm level regarded as acceptable by the UK and USA AAA screening programmes. Five studies had interobserver reproducibility below the level of 5 mm. Four studies, however, reported poor reproducibility (range from -2 to +5·2 to -10·5 to +10·4); these differences may have had a significant clinical impact on screening and surveillance. The studies used different methodologies with no standardized measurement techniques. Measurements were taken by observers from different medical disciplines of varying grade and levels of training. Standard training and formal quality assurance of ultrasound measurements are important components of an effective AAA screening programme.

Comparison of two-dimensional and three-dimensional imaging techniques for measurement of aortic annulus diameters before transcatheter aortic valve implantation

AimsDifferent two-dimensional (2D) and three-dimensional (3D) imaging techniques are used for procedure planning and selection of prosthesis size before transcatheter aortic valve implantation. This study sought to compare different 2D...

CT Angiography in Stent-Graft Sizing: Impact of Using Inner vs. Outer Wall Measurements of Aortic Neck Diameters

To assess the impact of using inner wall vs. outer wall measurements on stent-graft sizing for endovascular repair of abdominal aortic aneurysm (AAA). Preoperative static and electrocardiographically-gated 64-slice computed tomographic angiography (CTA) datasets were acquired on 40 consecutive AAA patients (29 men; mean age 78.9 ± 6 years, range 75-89). On static images, the aortic neck diameters were manually measured twice by 2 readers at 3 clinically relevant levels (supra-, juxta-, and infrarenal). The measurements were obtained from intima-to-intima (inner wall) and from adventitia-to-adventitia (outer wall). Dynamically reconstructed scans were also reviewed in each phase of the cardiac cycle to identify inner and outer minimum/maximum diameters. Using inner and outer wall measurements performed on static images, readers selected the size of a stent-graft that required inner neck diameter measurements and then one that required outer wall diameters. To calculate the relative oversizing, each selected stent-graft size was compared to that obtained using dynamic measurements. Oversizing <4% or >30% was considered inadequate. Mean variations for the inner and outer wall diameters of 9.75% ± 4.01% and 8.66% ± 3.71%, respectively, were recorded on static CTAs; the absolute changes in diameters were 1.82 ± 0.63 mm and 1.91 ± 0.64 mm, respectively. No statistically significant differences were found relative to aortic pulsatility at the 3 levels in the neck for the inner or outer wall diameters. Significant variability was seen between inner (mean 20.8 ± 3.4 mm) vs. outer (mean 23.7 ± 4.3 mm; p < 0.05) wall diameters. Stent-graft sizes significantly changed on the basis of the measurement method and device; for example, using the outer diameter to size a stent-graft that requires an inner diameter reference changed 36% of the selected stent-graft sizes, with ~20% being excessively oversized. Conversely, using the inner diameter to size an outer-diameter-based stent-graft resulted in nearly 40% of the sizes being altered. Based on dynamic measurements, the changes were more dramatic: the oversizing was considered excessive in up to 90% of patients if the measurement method did not match the stent-graft's stipulated reference. These data suggest that stent-graft sizing should follow the manufacturer's recommendations for using inner or outer diameter references based on dynamic patterns (mean value between diastolic and systolic diameters suggested).

Descending aortic diameter of 5.5 cm or greater is not an accurate predictor of acute type B aortic dissection

The risk of acute type B aortic dissection is thought to increase with descending thoracic aortic diameter. Currently, elective repair of the descending thoracic aorta is indicated for an aortic diameter of 5.5 cm or greater. We sought to investigate the relationship between aortic diameter and acute type B aortic dissection, and the utility of aortic diameter as a predictor of acute type B aortic dissection. We examined the descending aortic diameter at presentation of 613 patients with acute type B aortic dissection who were enrolled in the International Registry of Acute Aortic Dissection between 1996 and 2009, and analyzed the subset of patients with acute type B aortic dissection with an aortic diameter less than 5.5 cm. The median aortic diameter at the level of acute type B aortic dissection was 4.1 cm (range 2.1-13.0 cm). Only 18.4% of patients with acute type B aortic dissection in the International Registry of Acute Aortic Dissection had an aortic diameter of 5.5 cm or greater. Patients with Marfan syndrome represented 4.3% and had a slightly larger aortic diameter than patients without Marfan syndrome (4.68 vs 4.32 cm, P = .121). Complicated acute type B aortic dissection was more common among patients with an aortic diameter of 5.5 cm or greater (52.2% vs 35.6%, P < .001), and the in-hospital mortality for patients with an aortic diameter less than 5.5 cm and 5.5 cm or greater was 6.6% and 23.0% (P < .001), respectively. The majority of patients with acute type B aortic dissection present with a descending aortic diameter less than 5.5 cm before dissection and are not within the guidelines for elective descending thoracic aortic repair. Aortic diameter measurements do not seem to be a useful parameter to prevent aortic dissection, and other methods are needed to identify patients at risk for acute type B aortic dissection.

Comments regarding ‘Ultrasound Measurement of Aortic Diameter in a National Screening Programme’

Comments regarding 'Ultrasound Measurement of Aortic Diameter in a National Screening Programme'

Ultrasound Measurement of Aortic Diameter in a National Screening Programme

Objective Currently there is no universally accepted standard for ultrasound measurement of abdominal aortic aneurysm (AAA). The aim was to investigate the reliability and reproducibility of inner to inner (ITI) versus outer to outer (OTO) ultrasound measurement of AAA diameter. Methods A prospective study design was used to collect 60 random images of aorta (1.4–7.1 cm). Inner and outer wall diameter measurements were then performed by 13 qualified AAA screening technicians and 11 vascular sonographers. Results The mean (range) diameter for all 60 aortas by ITI was 3.91 cm (1.39–6.80) and by OTO was 4.18 cm (1.63–7.09), a significant mean difference of 0.27 cm (95% CI:0.23–0.32 cm). The reproducibility coefficients for differences between technicians were 0.30 cm (95% CI:0.24–0.36) for ITI and 0.42 cm (95% CI:0.35–0.49) for OTO indicating significantly better repeatability using ITI. Finally, 15 images were measured twice in random order by all screeners and sonographers. For AAAs >5 cm, repeatability was significantly better with ITI than OTO (0.14 vs. 0.21; p = 0.016). Conclusion There was the expected difference in AAA diameter between the two methods (0.27 cm). However, ITI wall method was measurably more reproducible.

Evaluation of aortic root for definition of prosthesis size by magnetic resonance imaging and cardiac computed tomography: Implications for transcatheter aortic valve implantation

BackgroundThis study sought to compare cardiac magnetic resonance imaging (CMR) with dual source computed tomography (DSCT) for analysis of aortic root dimensions prior to transcatheter aortic valve implantation (TAVI). In addition, the potential impact of CMR and DSCT measurements on TAVI strategy defined by 2D-transesophageal echocardiography (TEE) was evaluated. MethodsAortic root dimensions were measured using CMR and DSCT in 58 patients referred for evaluation of TAVI. The TAVI strategy (choice of prosthesis size and decision to implant) was based on 2D-TEE annulus measurements. ResultsCMR and DSCT aortic root measurements showed an overall good correlation (r=0.86, p<0.001 for coronal aortic annulus diameters). There was also a good correlation between TEE and CMR as well as between TEE and DSCT for measurement of sagittal aortic annulus diameters (r=0.69, p<0.001). However, annulus diameters assessed by TEE (22.1±2.3mm) were significantly smaller than coronal aortic annulus diameters assessed by CMR (23.4±1.8mm, p<0.001) or DSCT (23.6±1.8, p<0.001). Regarding TAVI strategy, the agreement between TEE and sagittal CMR (kappa=0.89) as well as sagittal DSCT measurements (kappa=0.87) was statistically perfect. However, decision based on coronal CMR- or MSCT measurements would have modified TAVI strategy as compared to a TEE based choice in a significant number of patients (22% to 24%). ConclusionIn patients referred for TAVI, CMR measurements of aortic root dimensions show a good correlation with DSCT measurements and thus CMR may be an alternative 3D-imaging modality. Aortic annulus measurements using TEE, CMR and DSCT were close but not identical and the method used has important potential implications on TAVI strategy.

Single breath-hold non-contrast thoracic mra using highly-accelerated parallel imaging with a 32-element coil array

OBJECTIVE—To evaluate the feasibility of performing single breath-hold 3D thoracic noncontrast magnetic resonance angiography (NC-MRA) using highly-accelerated parallel imaging. MATERIALS AND METHODS—We developed a single breath-hold NC MRA pulse sequence using balanced steady state free precession (SSFP) readout and highly-accelerated parallel imaging. In 17 subjects, highly-accelerated non-contrast MRA was compared against electrocardiogram (ECG)-triggered contrast-enhanced MRA. Anonymized images were randomized for blinded review by two independent readers for image quality, artifact severity in 8 defined vessel segments and aortic dimensions in 6 standard sites. NC-MRA and CE-MRA were compared in terms of these measures using paired sample t and Wilcoxon tests. RESULTS—The overall image quality (3.21±0.68 for NC-MRA vs. 3.12±0.71 for CE-MRA) and artifact (2.87±1.01 for NC-MRA vs. 2.92±0.87 for CE-MRA) scores were not significantly different, but there were significant differences for the great vessel and coronary artery origins. NC-MRA demonstrated significantly lower aortic diameter measurements compared to CE-MRA; however, this difference was not considered clinically relevant (>3 mm difference) for less than 12% of segments, most commonly at the sinotubular junction. Mean total scan time was significantly lower for NC-MRA compared to CE-MRA (18.2 ± 6.0s vs. 28.1 ± 5.4s, respectively; p < 0.05). CONCLUSION—Single breath-hold NC-MRA is feasible and can be a useful alternative for evaluation and follow-up of thoracic aortic diseases.

Preoperative quantification of aortic valve stenosis: comparison of 64-slice computed tomography with transesophageal and transthoracic echocardiography and size of implanted prosthesis

Precise measurements of aortic complex diameters are essential for preoperative examinations of patients with aortic stenosis (AS) scheduled for aortic valve (AV) replacement. We aimed to prospectively compare the accuracy of transthoracic echocardiography (TTE), transoesophageal echocardiography (TEE) and multi-slice computed tomography (MSCT) measurements of the AV complex and to analyze the role of the multi-modality aortic annulus diameter (AAd) assessment in the selection of the optimal prosthesis to be implanted in patients surgically treated for degenerative AS. 20 patients (F/M: 3/17; age: 69 ± 6.5 years) with severe degenerative AS were enrolled into the study. TTE, TEE and MSCT including AV calcium score (AVCS) assessment were performed in all patients. The values of AAd obtained in the long AV complex axis (TTE, TEE, MSCT) and in multiplanar perpendicular imaging (MSCT) were compared to the size of implanted prosthesis. The mean AAd was 24 ± 3.6 mm using TTE, 26 ± 4.2 mm using TEE, and 26.9 ± 3.2 in MSCT (P = 0.04 vs. TTE). The mean diameter of the left ventricle out-flow tract in TTE (19.9 ± 2.7 mm) and TEE (19.5 ± 2.7 mm) were smaller than in MSCT (24.9 ± 3.3 mm, P < 0.001 for both). The mean size of implanted prosthesis (22.2 ± 2.3 mm) was significantly smaller than the mean AAd measured by TTE (P = 0.0039), TEE (P = 0.0004), and MSCT (P < 0.0001). The implanted prosthesis size correlated significantly to the AAd: r = 0.603, P = 0.005 for TTE, r = 0.592, P = 0.006 for TEE, and r = 0.791, P < 0.001 for MSCT. Obesity and extensive valve calcification (AV calcium score ≥ 3177Ag.U.) were identified as potent factors that caused a deterioration of both TTE and MSCT performance. The accuracy of AAd measurements in TEE was only limited by AV calcification. In multivariate regression analysis the mean value of the minimum and maximum AAd obtained in MSCT-multiplanar perpendicular imaging was an independent factor (r = 0.802, P < 0.0001) predicting the size of implanted prosthesis. In patients with AS echocardiography remains the main diagnostics tool in clinical practice. MSCT as a 3-dimentional modality allows for accurate measurement of entire AV complex and facilitates optimal matching of prosthesis size.

Assessment of Elastase‐Induced Murine Abdominal Aortic Aneurysms: Comparison of Ultrasound Imaging with In Situ Video Microscopy

Aims. The aim of this study was to definitively assess the validity of noninvasive high-frequency ultrasound (US) measurements of aortic luminal diameter (ALD) in a murine model of elastase-induced abdominal aortic aneurysm in comparison with in situ video microscopy (VM). Methods. C57BL/6 mice underwent transient perfusion of the aorta with either elastase (n = 20: Elastase group) or saline (n = 10: Sham). Unoperated mice (n = 10) were also studied. Results. ALD measurements by US had excellent linear correlation and absolute agreement with that by VM in both Control (unoperated or sham-operated mice) and elastase groups (r = 0.96, intraclass correlation coefficient (ICC) = 0.88 and r = 0.93, ICC = 0.92, resp.). Bland-Altman analysis of US compared with VM measurements in both groups indicated good agreement, however US measurements were slightly but significantly higher than VM measurements in the control group (mean bias 0.039 mm, P < .05). Linear regression analysis revealed excellent correlation between US and VM measurements in both groups. (R2 = 0.91 in Control group, R2 = 0.85 in elastase group.) The reliability of US measurements was also confirmed by ex vivo histological measurements. Conclusions. High-frequency US provides reliable ALD measurements in developing murine abdominal aortic aneurysms.

Should the proximal arch be routinely replaced in patients with bicuspid aortic valve disease and ascending aortic aneurysm?

Bicuspid aortic valve is frequently associated with underlying aortopathy. Data support an aggressive approach to replacement of the ascending aorta. However, the natural history of the unreplaced aortic arch is unknown, and some have advocated routine replacement of the proximal arch in this setting. We identified patients with bicuspid aortic valve undergoing repair or replacement of the ascending aorta with or without aortic valve replacement or root replacement between January 1988 and December 2007 at our institution. Follow-up was by review of clinical records and postal questionnaire. Of 470 patients identified, 48 patients had hemiarch or total arch replacement and were excluded. Of the remaining 422 patients, 227 had separate aortic valve replacement or repair and ascending aortoplasty (76) or ascending aortic graft replacement (175), 107 a valved conduit, 40 a homograft root, and 21 a valve-sparing root replacement. The mean age was 56 ± 15 years, and 80% were male. Follow-up was up to 17 (median 4.2) years. There were 23 (5.5%) late reoperations, of which none were for arch dilatation. Survival at 1, 5, 10, and 12 years was 96.5%, 89.6%, 77.7%, and 74.0%. Freedom from late reoperation was 98.7%, 94.1%, 81.0%, and 81.0%. Paired echocardiographic measurements of aortic arch diameter (n = 58) were 33.3 mm preoperatively versus 31.9 mm postoperatively (P = .135) at a mean 4 years. Progressive dilatation of the aortic arch leading to reoperation after repair of ascending aortic aneurysm in patients with bicuspid aortic valve is uncommon. A selective approach to transverse aortic arch replacement is appropriate.

2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM Guidelines for the Diagnosis and Management of Patients With Thoracic Aortic Disease: Executive Summary

2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM Guidelines for the Diagnosis and Management of Patients With Thoracic Aortic Disease: Executive Summary

Ultrasound-determined diameter measurements are more accurate than axial computed tomography after endovascular aortic aneurysm repair

This study evaluated the correlation of ultrasound (US)-derived aortic aneurysm diameter measurements with centerline, three-dimensional (3-D) reconstruction computed tomography (CT) measurements after endovascular aortic aneurysm repair (EVAR). Concurrent CT and US examinations from 82 patients undergoing post-EVAR surveillance were reviewed. The aortic aneurysm diameter was defined as the major axis on the centerline images of 3-D CT reconstruction. This was compared with US-derived minor and major axis measurements, as well as with the minor axis measurement on the conventional axial CT images. Correlation was evaluated with linear regression analyses. Agreement between different imaging modalities and measurements was assessed with Bland-Altman plots. The correlation coefficients from linear regression analyses were 0.92 between CT centerline major and US minor measurements, 0.94 between CT centerline major and US major measurements, and 0.93 between CT minor and centerline major measurements. Bland-Altman plots showed a mean difference of 0.11 mm between US major and CT centerline measurements compared with 5.38 mm between US minor and CT centerline measurements, and 4.25 mm between axial CT minor and centerline measurements. This suggested that, compared with axial CT and US minor axis measurements, US major axis measurements were in better agreement with CT centerline measurements. Variability between major and minor US and CT centerline diameter measurements was high (standard deviation of difference, 4.27-4.84 mm). However, high variability was also observed between axial CT measurements and centerline CT measurements (standard deviation of difference, 4.36 mm). The major axis aneurysm diameter measurement obtained by US imaging for surveillance after EVAR correlates well and is in better agreement with centerline 3-D CT reconstruction diameters than axial CT.