60-S Retrogated Compressed Sensing 2D Cine of the Heart: Sharper Borders and Accurate Quantification

Abstract

Background and objective: Real-time compressed sensing cine (CS_rt) provides reliable quantification for both ventricles but may alter image quality. The aim of this study was to assess image quality and the accuracy of left (LV) and right ventricular (RV) volumes, ejection fraction and mass quantifications based on a retrogated segmented compressed sensing 2D cine sequence (CS_rg).

Methods: Thirty patients were enrolled. Each patient underwent the reference retrogated segmented steady-state free precession cine sequence (SSFP_ref), the real-time CS_rt cine and the segmented retrogated prototype CS_rg sequence providing the same slices. Functional parameters quantification and image quality rating were performed on SSFP_ref and CS_rg images sets. The edge sharpness, which is an estimate of the edge spread function, was assessed for the three sequences.

Results: The mean scan time was: SSFP_ref = 485.4 ± 83.3 (SD) s (95% CI: 454.3-516.5) and CS_rg = 58.3 ± 15.1 (SD) s (95% CI: 53.7-64.2) (p < 0.0001). CS_rg subjective image quality score (median: 4; range: 2-4) was higher than the one provided by CS_rt (median: 3; range: 2-4; p = 0.0008) and not different from SSFP_ref overall quality score (median: 4; range: 2-4; p = 0.31). CS_rg provided similar LV and RV functional parameters to those assessed with SSFP_ref (p > 0.05). Edge sharpness was significantly better with CS_rg (0.083 ± 0.013 (SD) pixel^-1; 95% CI: 0.078-0.087) than with CS_rt (0.070 ± 0.011 (SD) pixel^-1; 95% CI: 0.066-0.074; p = 0.0004) and not different from the reference technique (0.075 ± 0.016 (SD) pixel^-1; 95% CI: 0.069-0.081; p = 0.0516).

Conclusions: CS_rg cine provides in one minute an accurate quantification of LV and RV functional parameters without compromising subjective and objective image quality.

Keywords: CMR; cardiac; compressed sensing; fast imaging; function; heart; image quality; magnetic resonance; retrogating; retrospective.

Figure 1

Edge sharpness measurement. An orthogonal profile line is drawn across the border between the interventricular myocardium and the left ventricular blood pool (blue line) on a 4-chamber view at end-diastole provided by (a) the reference segmented SSFP sequence, (b) the real-time compressed sensing sequence and (c) the retrogated compressed sensing prototype, providing intensity profiles (blue curves) along the line for (d) reference, (e) real-time and (f) prototype sequences. The edge sharpness was calculated as the inverse of the distance d (in pixels) from the positions corresponding to 20% and 80% (red stars) of the difference between the maximum and minimum signal intensities (black crosses) along the profile line and was expressed in pixel⁻¹. Abbreviations: SSFP_ref, reference steady-state free precession; CS_rt, real-time compressed sensing; CS_rg, retrogated compressed sensing; ε, edge sharpness; Ymax, maximum signal intensity; Ymin, minimum signal intensity; d, distance along the intensity (pixels).

Figure 2

Midventricular short-axis cine slice acquired with the three cine sequences in a 37-year-old patient referred for myocarditis suspicion. (a) Reference steady-state free precession cine: Likert scale = 4/4; EuroCMR score = 0/10; ε = 0.082 pixel⁻¹; LVEF = 59%, LVEDV = 135 mL, LVM = 83 g, RVEF = 63%, RVEDV = 159 mL; (b) Real-time compressed sensing cine: Likert scale = 4/3; EuroCMR score = 0/10; ε = 0.056 pixel⁻¹; LVEF = 60%, LVEDV = 133 mL, LVM = 81 g, RVEF = 61%, RVEDV = 153 mL; (c) Retrogated compressed sensing cine: Likert scale = 4/4; EuroCMR score = 0/10; ε = 0.081 pixel⁻¹; LVEF = 58%, LVEDV = 133 mL, LVM = 86 g, RVEF = 62%, RVEDV = 164 mL. Abbreviations: ε, edge sharpness; LVEF, left ventricular ejection fraction; LVEDV, left ventricular end-diastolic volume; LVM, left ventricular myocardial mass; RVEF, right ventricular ejection fraction; RVEDV, right ventricular end-diastolic volume.

Figure 3

Edge sharpness comparison assessed at end-diastole. (a) There was no significant difference regarding ε between CS_rg and SSFP_ref (p = 0.0516) (b) but CS_rg significantly improved ε while compared with CS_rt (p = 0.0004). Abbreviations: CS_rg, retrogated compressed sensing; CS_rt, real-time compressed sensing; SSFP_ref, reference steady-state free precession; ε, edge sharpness.

Figure 4

Bland–Altman plots and linear regression trendlines applied to left ventricular functional parameters quantifications. Left column: Bland–Altman plots for (a) LVEF, (c) LVEDV, (e) LVESV, (g) LVSV and (i) LVM. Solid blue lines are the mean differences between parameters measured with SSFP_ref and CS_rg sequences and dashed red lines are the 95% limits of agreement. Right column: linear regression trend lines for (b) LVEF, (d) LVEDV, (f) LVESV, (h) LVSV and (j) LVM. Abbreviations: SSFP_ref, reference steady-state free precession; CS_rg, retrogated compressed sensing; SD, standard deviation; LVEF, left ventricular ejection fraction; LVEDV, left ventricular end-diastolic volume; LVESV, left ventricular end-systolic volume; LVSV, left ventricular stroke volume; LVM, left ventricular mass.

Figure 4

Bland–Altman plots and linear regression trendlines applied to left ventricular functional parameters quantifications. Left column: Bland–Altman plots for (a) LVEF, (c) LVEDV, (e) LVESV, (g) LVSV and (i) LVM. Solid blue lines are the mean differences between parameters measured with SSFP_ref and CS_rg sequences and dashed red lines are the 95% limits of agreement. Right column: linear regression trend lines for (b) LVEF, (d) LVEDV, (f) LVESV, (h) LVSV and (j) LVM. Abbreviations: SSFP_ref, reference steady-state free precession; CS_rg, retrogated compressed sensing; SD, standard deviation; LVEF, left ventricular ejection fraction; LVEDV, left ventricular end-diastolic volume; LVESV, left ventricular end-systolic volume; LVSV, left ventricular stroke volume; LVM, left ventricular mass.

Figure 5

Bland–Altman plots and linear regression trendlines applied to right ventricular functional parameters quantifications. Left column: Bland-Altman plots for (a) RVEF, (c) RVEDV, (e) RVESV, and (g) RVSV. Solid blue lines are the mean differences between parameters measured with SSFP_ref and CS_rg sequences and dashed red lines are the 95% limits of agreement. Right column: linear regression trend lines for (b) RVEF, (d) RVEDV, (f) RVESV, and (h) RVSV. Abbreviations: SSFP_ref, reference steady-state free precession; CS_rg, retrogated compressed sensing; SD, standard deviation; RVEF, right ventricular ejection fraction; RVEDV, right ventricular end-diastolic volume; RVESV, right ventricular end-systolic volume; RVSV, right ventricular stroke volume.