Towards highly accelerated Cartesian time-resolved 3D flow cardiovascular magnetic resonance in the clinical setting

Abstract

BackgroundThe clinical applicability of time-resolved 3D flow cardiovascular magnetic resonance (CMR) remains compromised by the long scan times associated with phase-contrast imaging. The present work demonstrates the applicability of 8-fold acceleration of Cartesian time-resolved 3D flow CMR in 10 volunteers and in 9 patients with different congenital heart diseases (CHD). It is demonstrated that accelerated 3D flow CMR data acquisition and image reconstruction using k-t PCA (principal component analysis) can be implemented into clinical workflow and results are sufficiently accurate relative to conventional 2D flow CMR to permit for comprehensive flow quantification in CHD patients.MethodsThe fidelity of k-t PCA was first investigated on retrospectively undersampled data for different acceleration factors and compared to k-t SENSE and fully sampled reference data. Subsequently, k-t PCA with 8-fold nominal undersampling was applied on 10 healthy volunteers and 9 CHD patients on a clinical 1.5 T MR scanner. Quantitative flow validation was performed in vessels of interest on the 3D flow datasets and compared to 2D through-plane flow acquisitions. Particle trace analysis was used to qualitatively visualise flow patterns in patients.ResultsAccelerated time-resolved 3D flow data were successfully acquired in all subjects with 8-fold nominal scan acceleration. Nominal scan times excluding navigator efficiency were on the order of 6 min and 7 min in patients and volunteers. Mean differences in stroke volume in selected vessels of interest were 2.5 ± 8.4 ml and 1.63 ± 4.8 ml in volunteers and patients, respectively. Qualitative flow pattern analysis in the time-resolved 3D dataset revealed valuable insights into hemodynamics including circular and helical patterns as well as flow distributions and origin in the Fontan circulation.ConclusionHighly accelerated time-resolved 3D flow using k-t PCA is readily applicable in clinical routine protocols of CHD patients. Nominal scan times of 6 min are well tolerated and allow for quantitative and qualitative flow assessment in all great vessels.

Whole-heart four-dimensional flow can be acquired with preserved quality without respiratory gating, facilitating clinical use: a head-to-head comparison

“…This study shows an underestimation of 4D flow SV compared to 2D flow, which is in line with previous results at 1.5 T and 3 T [7, 24]. In a phantom study with steady flow (as opposed to the pulsatile flow in the heart), Brix et al showed a 10 % overestimation of 4D flow compared to 2D [25], although their in vivo results show a small underestimation (−2 ± 15 ml, computed from presented values).…”

Aortic 4D flow MRI in 2 minutes using compressed sensing, respiratory controlled adaptive k‐space reordering, and inline reconstruction

“…K‐t PCA is another technique that has been applied to accelerate 4D flow. Values derived from this technique were found to be highly correlated with those of 2D PC MRI (R 2 = 0.93 for stroke volumes), with some underestimation in Q max in the AAo, superior vena cava, main pulmonary artery, and the left and right pulmonary arteries (−5.1% ± 7.5%) in volunteers when using an acceleration factor of 8 . More recently, Bollache et al explored a 2‐min aortic protocol using no respiratory navigation, k‐t PEAK GRAPPA acceleration (R = 5) with variable sampling patterns, and found underestimation in Q max and v max (Peak velocity, in vitro, −22% to −0.8% underestimation, in vivo [volunteers], −18% to 6.4%; current study : in vitro, −22.5% to −3.7%, in vivo [volunteers], −16.2% to −9.4%) …”

Independent validation of four‐dimensional flow MR velocities and vortex ring volume using particle imaging velocimetry and planar laser‐Induced fluorescence

“…The presented setup can therefore be used for validation of improved 4D PC‐MR sequences. Acceleration of 4D PC‐MR using techniques such as k‐t BLAST and k‐t SENSE , spiral readouts , random undersampling , and k‐t PCA is of great interest to reduce lengthy scan times. However, acceleration techniques often introduce errors such as temporal and spatial smoothing , which can be reliably evaluated using the proposed phantom setup.…”