Fast and accurate T1 Mapping at 3T using spiral TAPIR and compressed sensing
04 June 2019
Robert Claeser, Markus Zimmerman and N. Jon Shah
The TAPIR sequence is a well-established method for T1 mapping. By combining a slice‐interleaving Look‐Locker read‐out with the acquisition of multiple k‐space lines in one shot it enables the fast and accurate measurement of T1 relaxation times.
However, although the acquisition of multiple lines per excitation increases imaging speed, the corresponding increase in TR and TE is detrimental to the T1 fitting performance. To alleviate this trade‐off in imaging speed versus T1 mapping performance, in this study, a spiral read‐out was inserted into the TAPIR sequence with one arm of an interleaved spiral read‐out replacing the multi‐line Cartesian readout.
Although one interleave covers approximately the same portion of k‐space as one Cartesian EPI9 read‐out that acquires nine gradient echoes per interleave, the significantly shorter sampling time allows for a lower TR. Here we show that the short TE of a spiral read‐out also improves on the underestimation bias exhibited by many Look‐Locker T1 mapping sequences, including Cartesian TAPIR.
Additionally, a short TE is desirable to maximise the received MR signal, especially if substances with rapid T2 * relaxation, such as myelin water, are of interest. Finally, we show how using leave‐one‐out undersampling of interleaves with compressed sensing reconstruction for in vivo measurements provides a further reduction in scanning time and potentially reduces motion artefacts.
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