Single breath-hold slice-following CSPAMM myocardial tagging

Abstract

Myocardial tagging has shown to be a useful magnetic resonance modality for the assessment and quantification of local myocardial function. Many myocardial tagging techniques suffer from a rapid fading of the tags, restricting their application mainly to systolic phases of the cardiac cycle. However, left ventricular diastolic dysfunction has been increasingly appreciated as a major cause of heart failure. Subtraction based slice-following CSPAMM myocardial tagging has shown to overcome limitations such as fading of the tags. Remaining impediments to this technique, however, are extensive scanning times (~ 10 min), the requirement of repeated breath-holds using a coached breathing pattern, and the enhanced sensitivity to artifacts related to poor patient compliance or inconsistent depths of end-expiratory breath-holds. We therefore propose a combination of slice-following CSPAMM myocardial tagging with a segmented EPI imaging sequence. Together with an optimized RF excitation scheme, this enables to acquire as many as 20 systolic and diastolic grid-tagged images per cardiac cycle with a high tagging contrast during a short period of sustained respiration. 9

In vivo SNR in DENSE MRI; temporal and regional effects of field strength, receiver coil sensitivity and flip angle strategies

“…The use of variable flip angle without slice-following will in practice not produce a constant SNR unless the saturation effect of through-plane motion is taken into account. This may partly explain the slight increase in SNR over time seen in this study and previously [22]; however, some of this effect has also been observed using slice-following [3].…”

“…The flip angle optimization was based on heart rate, myocardial T 1 and excitation pattern, as previously reported [3]. T 1 values of 870 ms at 1.5T and 1114 ms at 3T were used.…”

“…This is achieved with a low flip angle in the early cardiac phases and a higher towards the end; this exploits that the stimulated signal is strong in the beginning and not consuming the signal unnecessarily. The flip angle sequence can be optimized with respect to T 1 and heart rate to produce a steady state of multiple heart-cycles where excitation and relaxation is balanced [3]. This approach gives the highest constant SNR level achievable, making it a popular technique, especially in tagging studies.…”

Magnitude image CSPAMM reconstruction (MICSR)

“…It is well known that the RF pulses of the imaging sequence have significant effect on tag persistence (15,16). It is possible to improve SPAMM and CSPAMM tag persistence (contrast) by starting with a small flip angle when M Z is large and increasing the flip angle as M Z decreases (15,16).…”

“…It is possible to improve SPAMM and CSPAMM tag persistence (contrast) by starting with a small flip angle when M Z is large and increasing the flip angle as M Z decreases (15,16). Although we do not currently have the ability to use variable flip angles in cardiac gated cine imaging on our Marconi 1.5T Eclipse, we will be performing simulations to examine the effect of variable flip angles on MICSR contrast.…”