Coronary MR angiography at 3T during diastole and systole

Abstract

Purpose:To investigate the impact of end-systolic imaging on quality of right coronary magnetic resonance angiography (MRA) in comparison to diastolic and to study the effect of RR interval variability on image quality. Materials and Methods:The right coronary artery (RCA) of 10 normal volunteers was imaged at 3T using parallel imaging (sensitivity encoding [SENSE]). Navigator-gated three-dimensional (3D) gradient echo was used three times: 1) end-systolic short acquisition (SS): 35-msec window; 2) diastolic short (DS): middiastolic acquisition using 35-msec window; and 3) diastolic long (DL): 75-msec diastolic acquisition window. Vectorcardiogram (VCG) data was used to analyze RR variability. Vessel sharpness, length, and diameter were compared to each other and correlated with RR variability. Blinded qualitative image scores of the images were compared.Results: Quantitative and qualitative parameters were not significantly different and showed no significant correlation with RR variability. Conclusion:Imaging the RCA at 3T during the end-systolic rest period using SENSE is possible without significant detrimental effect on image quality. Breaking away from the standard of imaging only during diastole can potentially improve image quality in tachycardic patients or used for simultaneous imaging during both periods in a single scan. A MAJOR TECHNICAL CHALLENGE for coronary magnetic resonance angiography (MRA) is cardiac motion (1). Adverse effects of this motion on image quality can be minimized by acquiring images during the most quiescent mid-diastolic period of the cardiac cycle (2-4) which is typically found in middiastole. This relative motion-free period occurs after relaxation of the ventricles at approximately 75% of the cardiac cycle, and depending on the heart rate, lasts for an average of 187 msec (range 66 -330 msec) (1). Both coronary MRA (2-4) and computed tomography angiography (CTA) dose modulation (5) protocols are usually set to acquire images or reconstruct images during this period of the cardiac cycle. However, at the end of ventricular systole, (approximately 34% of the cardiac cycle) there is another relatively quiescent period that lasts for approximately 118 msec (range 0 -223 msec) (1).Though both of these periods' lengths have an inverse relationship with the heart rate (1), the duration of systole is less affected by heart rate variability than that of diastole (6). For example, an increase of 10% in heart rate from 70 to 77 beats per minute (BPM) should shorten diastasis, on average, from 458 msec to 395 msec (63 msec or 14%) but only change systole from 399 msec to 384 msec (15 msec or 4%) (7). Hence, for subjects with high beat-to-beat variability in their RR interval lengths, the temporal position of the middiastolic period may be more variable than that of the endsystolic period.For these reasons, end-systolic imaging may be an alternative to more conventional diastolic imaging as a way to minimize the adverse effects of RR variability. However, the abbreviated systolic rest peri...

Initial results on in vivo human coronary MR angiography at 7 T

“…While we did not perform a direct comparison with lower-field-strength coronary MRA, the 7 T scanning time was similar to that of earlier reports performed at lower field strength (21,22) and without parallel imaging. However, and using the present 7 T approach, an increased visible vessel length and a higher image quality may be expected at both 1.5 T (20) and 3 T (5).…”

Correction for heart rate variability during 3D whole heart MR coronary angiography

“…However, a more recent study suggests that imaging at end-systole does not affect image quality if the acquisition window is SENSE abbreviated (34). Especially in tachycardic patients, imaging at end-systole (using Eq.…”

Motion Compensation Strategies in Magnetic Resonance Imaging

“…Typically, a period of minimal myocardial motion occurs in late diastole, 25 although end-systolic imaging may be preferable in patients with high heart rates. 26,27 While ECG triggering is the workhorse of cardiac MRI, it is also applied in peripheral organs where the pulsatility of the blood causes unwanted artifacts, such as in carotid imaging 28 or cerebral blood flow measurements. 29 Considerable ECG-signal degradation may occur because of radiofrequency (RF) fields and gradient -switching.…”