Image reconstruction impacts haemodynamic parameters derived from 4D flow magnetic resonance imaging with compressed sensing.

Abstract

Aims: 4D blood flow measurements by cardiac magnetic resonance imaging (CMR) can be used to simplify blood flow assessment. Compressed sensing (CS) can provide better flow measurements than conventional parallel imaging (PI), but clinical validation is needed. This study aimed to validate stroke volume (SV) measurements by 4D-CS in healthy volunteers and patients while also investigating the influence of the CS image reconstruction parameter λ on haemodynamic parameters.

Methods and results: Healthy participants (n = 9; 20-62 years) underwent CMR with 2D, 4D-CS, and 4D-PI flow. Patients (n = 30, 17 with congenital heart defect; 2-75 years) had 4D-CS added to their clinical examination. Impact of λ was assessed by reconstructing 4D-CS data for six different λ values. In healthy volunteers, 4D-CS and 4D-PI SV differed by 0.4 ± 6.5 mL [0.6 ± 9.1%; intraclass correlation coefficient (ICC) 0.98], and 4D-CS and 2D flow by 0.9 ± 7.0 mL (0.9 ± 10.6%; ICC 0.98). In patients, 4D-CS and 2D flow differed by -1.3 ± 6.0 mL (-7.2 ± 20%; ICC 0.97). SV was not dependent on λ in patients (P = 0.75) but an increase in λ by 0.001 led to increased differences between 4D-CS and 4D-PI of -0.4% (P = 0.0021) in healthy participants. There were significant differences for ventricular kinetic energy (systole: P < 0.0001; diastole: P < 0.0001) and haemodynamic forces (systole: P < 0.0001; diastole: P < 0.0001), where error increased with increasing λ values in both healthy participants and patients.

Conclusion: 4D flow CMR with CS can be used clinically to assess SV in paediatric and adult patients. Ventricular kinetic energy and haemodynamic forces are however sensitive to the change in reconstruction parameter λ, and it is therefore important to validate advanced blood flow measurements before comparing data between scanners and centres.