Background:

The current standard in functional and volumetric imaging by cardiovascular magnetic resonance (CMR) are protocols using ECG gated balanced steady-state free precision (bSSFP) in breathholdig technique. The resulting image quality can severely suffer from insufficient patient cooperation or arrhythmia. Real-time imaging (RT) is an approach to overcome these limitations of CMR. We show our first results with patients in sinus rhythm and atrial fibrillation using bSSFP compared to RT.

Methods:

27 patients (21 sinus rhythm, 6 atrial fibrillation) were scanned with a CMR protocol including bSSFP as well as a RT sequence. The RT protocol uses a spiral tiny-golden angle (TyGA)  multislice acquisition without the need of breathholding or respiratory gating. The spiral sequence comprised an Archimedean spiral with a fixed acquisition time of 3 ms. The angle between consecutive interleaves was determined as a modified TyGA trajectory for center-out acquisitions (TyGA-CAT). All data were reconstructed by a k-t SPARSE-SENSE framework with a Total Variation sparsity operator. Image analysis was done using Segment (Medviso AB, Lund, Sweden). Intraclass correlations (ICC) and Bland-Altman-Plots were performed using SPSS 26 (IBM Corp., Armonk, NY, USA).

Results:

Very good ICC were seen for LVEDV and LVESV (both ICC=0.996), LVSV (ICC=0.981), LVEF (ICC=0.971), RVEDV (ICC=0.990), RVESV (ICC=0.991), RVSV (ICC=0.973) and RVEF (ICC=0.966). A good agreement between both sequences is also seen in the Bland-Altman-Plots even though the sample size is small.

Discussion:

RT imaging is feasible in patients with sinus rhythm as well as atrial fibrillation. Although the image resolution is lower, volumetric results are comparable to those of standard bSSFP imaging. Only minor differences were found between the two measurements, which seem to be not relevant in clinical practice. While the RT imaging was made under free breathing, a different intrathoracic pressure and thereby a different cardiac preload may affect the volumetric measurements. A larger cohort with atrial fibrillation is needed to show the full potential of RT imaging i.e. in patients with severe arrhythmia.