Aortic Volumetry at Contrast-Enhanced Magnetic Resonance Angiography

Abstract

1.1. Objectives Bicuspid aortic valve (BAV) patients can develop thoracic aortic aneurysms (TAA) and therefore require serial imaging to monitor aortic growth. This study investigates the reliability of contrast-enhanced MR angiography (CEMRA) volumetry compared to two-dimensional diameter measurements to identify TAA growth. 1.2. Materials and Methods A retrospective, IRB approved and HIPAA compliant study was conducted on 20 BAV patients (45±8.9 years old, 20% women) who underwent serial CEMRA with a minimum imaging follow-up of 11 months. MRI was performed at 1.5 T with ECG-gated time-resolved CEMRA. Independent observers measured the diameter at the sinuses of Valsalva (SOV) and mid-ascending aorta (MAA) as well as ascending aorta volume between the aortic valve annulus and innominate branch. Intra/inter-observer coefficient of variation (COV) and intraclass correlation coefficient (ICC) were computed to assess reliability. Growth rates were calculated and assessed by Student’s t-test (p<0.05 significant). The diameter of maximal growth (DMG), defined as the diameter at SOV or MAA with the faster growth rate, was recorded. 1.3. Results The mean time of follow-up was 2.6±0.82 years (y). The intraobserver COV was 0.01 for SOV, 0.02 for MAA, and 0.02 for volume (interoberserver COV: 0.02, 0.03, 0.04, respectively). The ICC was 0.83 for SOV, 0.86 for MAA, 0.90 for DMG, and 0.95 for volume. Average aortic measurements at baseline and (follow-up) were 42±3 mm (42±3 mm, p=0.11) at SOV, 46±4 mm (47±4 mm, p<0.05) at MAA, and 130±23 mL (144±24 mL, p<0.05). Average size changes were 0.2±0.6 mm/y (1%±2%) at SOV, 0.5±0.8 mm/y (1%±2%) at MAA, 0.7±0.7 mm/y (2%±2%) at DMG, and 6±3 mL/y (4%±3%) with volumetry. 1.4. Conclusions 3D CEMRA volumetry exhibited a larger effect when examining percentage growth, a better ICC, and a marginally lower COV. Volumetry may be more sensitive to growth and possibly less affected by error than diameter measurements.

Interval changes in aortic peak velocity and wall shear stress in patients with bicuspid aortic valve disease

“…While earlier studies demonstrated aortic dilation rates of 1 to 2 mm/year [5], few patients are found to exhibit such rapid growth. A recent study by Trinh et al described diametric aortic growth of 0.06 cm/year [34]. This was corroborated by Detaint et al who found average annual maximum growth rates of 0.04 cm/ year (median 0.03 cm/year) as well as in Della Corte et al with average annual maximum growth rates of 0.06 cm/year [11,33].…”

“…Previous studies at our center using the same methods have investigated WSS, peak velocity, and aortic diameter and demonstrated excellent inter-observer reproducibility for all parameters [16,34,37]. The test-retest variability for region of interest analysis of systolic peak velocity and 3D WSS showed good agreement (Intra-class correlation coefficient ICC = 0.9 for velocity, and ICC = 0.8 for WSS) and a maximum difference of 0.04 m/sec for velocity and 0.05 Pa for WSS in a previously published study [37].…”

Aortic Valve Stenosis Alters Expression of Regional Aortic Wall Shear Stress: New Insights From a 4‐Dimensional Flow Magnetic Resonance Imaging Study of 571 Subjects

“…All subjects underwent a standard‐of‐care thoracic cardiovascular MRI exam including 2‐dimensional (2D) time‐resolved ECG gated (CINE) balanced steady state free precession imaging of the heart and aortic valve as well as 3D contrast‐enhanced magnetic resonance angiography following the administration of contrast media (either 0.2 mmol/kg of gadopentate dimeglumine, 0.1 mmol/kg of gadobenate dimeglumine, or 0.1 mmol/kg of gadofosveset trisodium) to provide a comprehensive evaluation of aortic morphology and valve function as previously reported 15, 16. In addition, 4D flow MRI (time‐resolved 3‐directional phase contrast MRI with 3D velocity encoding) was acquired in a sagittal oblique 3D volume covering the thoracic aorta using prospective ECG gating and a respiratory navigator gating 17.…”

“…contrast-enhanced magnetic resonance angiography following the administration of contrast media (either 0.2 mmol/kg of gadopentate dimeglumine, 0.1 mmol/kg of gadobenate dimeglumine, or 0.1 mmol/kg of gadofosveset trisodium) to provide a comprehensive evaluation of aortic morphology and valve function as previously reported. 15,16 In addition, 4D flow MRI (time-resolved 3-directional phase contrast MRI with 3D velocity encoding) was acquired in a sagittal oblique 3D volume covering the thoracic aorta using prospective ECG gating and a respiratory navigator gating. 17 4D flow pulse sequence parameters were as follows: spatial resolution=2.2 to 4.2 mm91.7 to 2.9 mm92.2 to 4.0 mm; field of view=320 to 470 mm9234 to 382 mm966 to 120 mm; temporal resolution=32.8 to 43.2 ms (11-31 cardiac time frames); echo time=2.1 to 2.8 ms; repetition time=4.1 to 5.4 ms; flip angle=7 to 15°.…”

Vascular Deformation Mapping (VDM) of Thoracic Aortic Enlargement in Aneurysmal Disease and Dissection

“…Measuring the aortic diameter at predefined anatomic locations fails to capture interval growth at nonmaximal locations, and this measurement does not detect the components of aortic enlargement in circumferential or longitudinal directions. Height-/weight-adjusted aortic area has been proposed as a better predictor of future rupture than maximal diameter, and several studies have investigated the use of volumetric measurements of TAA and AAA to improve the sensitivity for detecting aortic growth ( 10 , 20 – 24 ). However, similar to diameter measurements, measurement of aortic area and volumetric should be performed at predetermined anatomic boundaries to ensure that measurements are comparable between studies, and small focal changes in aortic dimension may be camouflaged by a volumetric measurement approach.…”