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- Open Access
Noninvasive pressure measurement with 4D phase contrast MRI in patients with aortic coarctations
© Nett et al; licensee BioMed Central Ltd. 2012
- Published: 1 February 2012
- Pressure Gradient
- Aortic Coarctation
- Velocity Encode
- Simplify Bernoulli Equation
- Retrospective Cardiac Gating
In this study, pressure gradients measured with 4D phase contrast MRI were compared to those measured with Doppler ultrasound in patients with aortic coarctations. We found good agreement between these methods as well as good correlation between pressure measurements and degree of stenosis.
Seven subjects (2F/5M, mean age 22.7 years) with CoA were enrolled. Three patients were imaged before repair and four after. All patients had routine clinical transthoracic US exams.
All patients were scanned on clinical 1.5T or 3T systems. Volumetric, time-resolved PC MRI data with 3-directional velocity encoding were acquired with dual-echo PC VIPR  and respiratory and retrospective cardiac gating: 1.25mm3 isotropic resolution, BW=125 kHz, TR 6.2ms, volume: 32cm x 32 cm x 20 cm, 12,000 dual echoes, scan time= ~13 min, Venc = 160 cm/s.
PC VIPR pressure gradients were derived using an iterative method based on the Navier-Stokes equation . 3D visualization was achieved using EnSight (CEI). Quantification of pressure gradients was done using a Matlab (Mathworks) analysis tool. The PC VIPR and US pressure measurements were compared for statistical significant differences using the paired t-test (p<0.05).
A significant correlation between PC VIPR and US pressure measurements was observed (r = 0.84, P = 0.13). Overall, PC VIPR underestimated pressure differences compared with US . PC VIPR pressure measurements were compared with the grade of the stenosis and these measurements were also found to be correlated (r = 0.51, P = 0.14).
This study demonstrates the utility of 4D PC MRI for measurement of 4D pressure gradients in aortic coarctations as compared with Doppler ultrasound as well as percent stenosis. Similar to the findings of a recent 4D MR flow study with Cartesian encoding, the peak pressure differences were lower than assessed with US . 4D PC MRI can also be used to measure other important hemodynamic parameters such as WSS and OSI which have been linked to aneurysm formation. These noninvasive measures can possibly assist in the diagnosis and follow-up of patients with CHD.
Peak pressure differences measured across the aortic coarctation and with PC VIPR and Doppler ultrasound and associated percent stenosis for each patient
Time Between Ultrasound and MRI
PC VIPR Pressure (mmHg)
Ultrasound Pressure (mmHg)
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