Feasibility of real‐time cardiac MRI in mice using tiny golden angle radial sparse

Abstract

Cardiovascular magnetic resonance imaging has proven valuable for the assessment of structural and functional cardiac abnormalities. Even although it is an established imaging method in small animals, the long acquisition times of gated or self-gated techniques still limit its widespread application. In this study, the application of tiny golden angle radial sparse MRI (tyGRASP) for real-time cardiac imaging was tested in 12 constitutive nexilin (Nexn) knock-out (KO) mice, both heterozygous (Het, N = 6) and wild-type (WT, N = 6), and the resulting functional parameters were compared with a well-established self-gating approach. Real-time images were reconstructed for different temporal resolutions of between 16.8 and 79.8 ms per image. The suggested approach was additionally tested for dobutamine stress and qualitative first-pass perfusion imaging. Measurements were repeated twice within 2 weeks for reproducibility assessment. In direct comparison with the high-quality, self-gated technique, the real-time approach did not show any significant differences in global function parameters for acquisition times below 50 ms (rest) and 31.5 ms (stress).Compared with WT, the end-diastolic volume (EDV) and end-systolic volume (ESV) were markedly higher (P < 0.05) and the ejection fraction (EF) was significantly lower in the Het Nexn-KO mice at rest (P < 0.001). For the stress investigation, a clear decrease of EDV and ESV, and an increase in EF, but maintained stroke volume, could be observed in both groups. Combined with ECG-triggering, tyGRASP provided firstpass perfusion data with a temporal resolution of one image per heartbeat, allowing the quantitative assessment of upslope curves in the blood-pool and myocardium.Excellent inter-study reproducibility was achieved in all the functional parameters.The tyGRASP is a valuable real-time MRI technique for mice, which significantly reduces the scan time in preclinical cardiac functional imaging, providing sufficient image quality for deriving accurate functional parameters, and has the potential to investigate real-time and beat-to-beat changes.

Quantification of Biventricular Myocardial Strain Using CMR Feature Tracking: Reproducibility in Small Animals

“…All animals were anesthetized in an induction container attached to the vaporizer by exposure to 5% isoflurane. The isoflurane was then maintained between 1.0 and 1.5% in medical air (0.1 L/min) during the entire procedure to maintain the respiratory frequency between 60 and 80 respiratory cycles per minute [ 20 ]. Mice were placed in a prone position, and the respiratory rate was monitored with a balloon pressure sensor.…”

“…CMR cine data were acquired by applying a conventional Cartesian self-gated sequence (IntraGate©, ParaVision 6.0.1, Bruker BioSpin, Ettlingen, Germany) with Sensitivity Encoding (SENSE) acceleration [ 20 , 21 ]. Slice planning was performed as suggested earlier [ 21 ] ensuring high reproducibility of the image geometry for subsequent examinations.…”

“…The number of short-axis slices was adjusted to ensure full coverage of the left and right ventricles in end-diastole. The following parameters were set [ 20 ]: echo/repetition time TE/TR = 1.04/5.62 ms, flip angle α = 15°, matrix size = 256 × 256, in-plane resolution Δ r = 0.1172 mm 2 , slice thickness s D = 1.0 mm, bandwidth bw = 125 kHz, 20 phases per cardiac cycle, 200-fold oversampling, acceleration factor = 2, and acquisition time T ACQ = 2 m 37 s per slice.…”

Non-invasive Imaging in Patients With Chronic Total Occlusions of the Coronary Arteries—What Does the Interventionalist Need for Success?

“…Image quality is getting worse only in patients with severe arrhythmia or non-compliant patients. Real-time imaging without the need for breath holding is evolving to overcome these disadvantages (72).…”

Quantitative myocardial first‐pass perfusion imaging of CO2‐induced vasodilation in rats

“…The acceleration of data acquisition was necessary to obtain a sufficient temporal resolution as fast heart rates in rodents preclude a full sampling of k-space during a single heartbeat. Previous reports employed either sensitivity-encoding 29,43,44 or k-t undersampling 37,40,[45][46][47] to accelerate data acquisition with an acceleration factor varying from R = 2 to R = 10. The data were reconstructed with k-t PCA, which was shown to perform well for larger undersampling factors 48 and was previously used to reconstruct first-pass perfusion data in mice with an acceleration factor of R = 10.…”