Purpose: To analyze the influence of spatial resolution, field strength and imaging sequence on the quantification of RV wall motion using FT-CMR.
Methods: Cine CMR images (Philips) were acquired in 10 healthy volunteers (mean age 28±4 yrs and 60% male). We used two acquisition methods (balanced Steady State Free Precession [bSSFP] on 1.5T and 3T [not possible on 7T] and Fast Low Angle Shot [FLASH] on 3T and 7T) at increasing resolution (Table 1). FT-CMR (Medis) was performed on RV 4-chamber axis to calculate mean and regional longitudinal strain. Correlations between resolutions (1.7x1.7x8mm³ vs. 1.3x1.3x8mm³ and vs. 2x2x10mm³); imaging sequences (bSSFP vs. FLASH); and field strengths (3T vs. 1.5T and 3T vs. 7T), were calculated using Spearman’s Rho (rs). One variable was altered for every comparison separately.
Results: Comparing resolution on 1.5T, a moderate correlation was seen between mean strain values at lower (1.3x1.3x8 mm³) and higher (2x2x10 mm³) resolution compared to the standard resolution (1.7x1.7x8 mm3) (rs 0.69 [p=0.03] and rs 0.56 [p=0.09] respectively). For regional strain, this differed per region (rs 0.30-0.87), with the strongest correlation in the subtricuspid region (rs=0.83, p=0.003). Comparing field strengths, 1.5T and 3T bSSFP images showed a good correlation of mean RV strain (-22±5% and -21±6%, respectively; rs 0.78 [p=0.02]), but a poor correlation of regional strain (rs=0.24). In contrast, 3T and 7T FLASH images, showed poor correlation for mean RV strain (rs -0.18 [p=0.70]). For regional strain, this differed per region (rs -0.54-0.79), with a good correlation (rs 0.79 p<0.04) for the subtricuspid region. Comparing image sequence on 3T, a poor correlation was observed between bSSFP and FLASH (rs 0.14-0.49).
Conclusion: This study illustrates how imaging parameters influence RV FT-CMR. Both global and regional strain values are influenced by imaging sequence, but to a lesser extent by the spatial resolution. Furthermore, mean strain values on 3T correlate with 1.5T, but not with 7T.