Feasibility and reproducibility of biventricular volumetric assessment of cardiac function during exercise using real‐time radial k‐t SENSE magnetic resonance imaging

Abstract

Purpose:To assess the feasibility and reproducibility of real-time radial k-t sensitivity encoding (SENSE) magnetic resonance imaging (MRI) for biventricular volumetric assessment during exercise. Materials and Methods:In all, 12 healthy young adults underwent MRI at rest and during supine exercise at three different workload intensities. Biventricular volumes and function were assessed with 1) a radial k-t SENSE real-time sequence and 2) a scanner vendor supplied (standard) realtime sequence. Global image quality, motion fidelity, and agreement in right ventricular (RV) and left ventricular (LV) stroke volume (SV) as a surrogate measure for accuracy were assessed. Exercise MR was repeated within 1 month for assessment of reproducibility.Results: Imaging scores were superior for radial real-time k-t SENSE images (P Ͻ 0.001). Agreement in RV and LV SV during exercise was better with radial k-t real-time (SD of difference Ϯ3.43 vs. Ϯ8.97 mL; P Ͻ 0.001). Agreement in cardiac output (CO) in the same subject at two different imaging sessions was better for radial k-t SENSE. This was significant for the CO calculated for the RV (SD of difference Ϯ0.6 vs. Ϯ0.95 L/min; P ϭ 0.01) and LV (Ϯ0.45 vs. Ϯ0.92 L/min; P Ͻ 0.001). Conclusion:Radial k-t SENSE real-time imaging represents a feasible and reproducible imaging technique for biventricular assessment during exercise.

Isometric stress in cardiovascular magnetic resonance—a simple and easily replicable method of assessing cardiovascular differences not apparent at rest

“…The image plane was positioned at the sinotubular junction. Left ventricular volumes were assessed in the short axis (11-13 slices) during free breathing using a real-time radial k-t SENSE sequence (FOV: ≈380 mm, matrix: 128×128, voxel size: ≈3.0×≈3.0×10 mm, TE/TR: ≈1.14/ ≈2.3 msec, flip angle: 38°, pixel bandwidth: 1,500 Hz/pixel, radial spokes: 128, k-t SENSE acceleration factor: 8, scan time: ≈1.5 sec per slice, temporal resolution: ≈35.5 msec) [15].…”

Cardiac MRI

“…We provide advances on these novel techniques by instituting a means of compensating for cardiac translation caused by diaphragmatic excursion and by validating the techniques against a recognized standard. Furthermore, Lurz et al 9,20 used an ergometer in which subjects move their straight legs in a kicking motion, a form of exercise that uses a smaller muscle mass and less physical work (≤22.5 W) compared with the cycle exercise used in our study (218±52 W). Higher CO values were measurable in our study, and the strong agreement between CO Fick and CO CMR verifies their accuracy.…”

“…As a result, investigators have resorted to CMR imaging during early recovery, 6,7 during breath-hold, 8 or at submaximal exercise intensities. 9 No studies have validated real-time exercise CMR measures against cardiac output (CO) measures derived by invasive standards.…”

“…These techniques were sufficient for demonstrating a difference in RV reserve between patients with marked alterations in RV afterload and healthy control subjects, although the expected differences in recovery rates serve as an important confounder. Lurz et al 9,20 provide the only previous experience of true real-time CMR imaging during exercise and freebreathing using an ungated sequence similar to that described here (although they used radial rather than Cartesian k-space sampling). We provide advances on these novel techniques by instituting a means of compensating for cardiac translation caused by diaphragmatic excursion and by validating the techniques against a recognized standard.…”

Cardiac Function

“…This has urged several groups to develop clinically useful ultrafast and real-time sequences with an acceptable temporal resolution (below 50 ms) and in-plane spatial resolution (below 2.5 mm) (Kramer et al 2008). In addition to use of techniques such as view or echo sharing and parallel imaging, a substantial reduction in measurement time can be achieved by developing novel strategies to fill the k-space (e.g., partial k-space filling, radial or spiral k-space filling), and by exploiting correlations in k-space and time (k-t) such as k-t BLAST and k-t SENSE techniques (see ''Cardiac MR Physics''; Setser et al 2000;Nagel et al 2000;Kaji et al 2001;Barkhausen et al 2002;Lee et al 2002;Spuentrup et al 2003;Hori et al 2003;Kühl et al 2004;Taylor et al 2005;Jahnke et al 2006Jahnke et al , 2007Muthurangu et al 2008;Lurz et al 2009). …”