A fast navigator (fastNAV) for prospective respiratory motion correction in first‐pass myocardial perfusion imaging

• Published in: Magnetic resonance in medicine Vol. 85; no. 5; pp. 2661 - 2671
• Main Authors: Mooiweer, Ronald, Neji, Radhouene, McElroy, Sarah, Nazir, Muhummad Sohaib, Razavi, Reza, Chiribiri, Amedeo, Roujol, Sébastien
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.05.2021; John Wiley and Sons Inc
• Subjects: Breathing; Calibration; Excitation; Full Papers—Imaging Methodology; Heart; Image quality; Magnetic resonance imaging; myocardial perfusion; navigator; Perfusion; prospective motion correction; Quality assessment; Respiration; respiratory motion correction; slice tracking; Statistical analysis; subject‐specific tracking factor; Tracking; Ventricle; navigator; respiratory motion correction; slice tracking; myocardial perfusion; subject-specific tracking factor; prospective motion correction
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.28617

Purpose To develop and evaluate a fast respiratory navigator (fastNAV) for cardiac MR perfusion imaging with subject‐specific prospective slice tracking. Methods A fastNAV was developed for dynamic contrast‐enhanced cardiac MR perfusion imaging by combining spatially nonselective saturation with slice‐selective tip‐up and slice‐selective excitation pulses. The excitation slice was angulated from the tip‐up slice in the transverse plane to overlap only in the right hemidiaphragm for suppression of signal outside the right hemidiaphragm. A calibration scan was developed to enable the estimation of subject‐specific tracking factors. Perfusion imaging using subject‐specific fastNAV‐based slice tracking was then compared to a conventional sequence (ie, without slice tracking) in 10 patients under free‐breathing conditions. Respiratory motion in perfusion images was quantitatively assessed by measuring the average overlap of the left ventricle across images (avDice, 0:no overlap/1:perfect overlap) and the average displacement of the center of mass of the left ventricle (avCoM). Image quality was subjectively assessed using a 4‐point scoring system (1: poor, 4: excellent). Results The fastNAV calibration was successfully performed in all subjects (average tracking factor of 0.46 ± 0.13, R = 0.94 ± 0.03). Prospective motion correction using fastNAV led to higher avDice (0.94 ± 0.02 vs. 0.90 ± 0.03, P < .001) and reduced avCoM (4.03 ± 0.84 vs. 5.22 ± 1.22, P < .001). There were no statistically significant differences between the 2 sequences in terms of image quality (both sequences: median = 3 and interquartile range = 3‐4, P = 1). Conclusion fastNAV enables fast and robust right hemidiaphragm motion tracking in a perfusion sequence. In combination with subject‐specific slice tracking, fastNAV reduces the effect of respiratory motion during free‐breathing cardiac MR perfusion imaging.