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Time-encoded pseudo-continuous arterial spin labeling: Increasing SNR in ASL dynamic angiography.
| Content Provider | Europe PMC |
|---|---|
| Author | Woods, Joseph G. Schauman, S. Sophie Chiew, Mark Chappell, Michael A. Okell, Thomas W. |
| Abstract | PurposeDynamic angiography using arterial spin labeling (ASL) can provide detailed hemodynamic information. However, the long time‐resolved readouts require small flip angles to preserve ASL signal for later timepoints, limiting SNR. By using time‐encoded ASL to generate temporal information, the readout can be shortened. Here, the SNR improvements from using larger flip angles, made possible by the shorter readout, are quantitatively investigated.MethodsThe SNR of a conventional protocol with nine Look‐Locker readouts and a 4 × 3 time‐encoded protocol with three Look‐Locker readouts (giving nine matched timepoints) were compared using simulations and in vivo data. Both protocols were compared using readouts with constant flip angles (CFAs) and variable flip angles (VFAs), where the VFA scheme was designed to produce a consistent ASL signal across readouts. Optimization of the background suppression to minimize physiological noise across readouts was also explored.ResultsThe time‐encoded protocol increased in vivo SNR by 103% and 96% when using CFAs or VFAs, respectively. Use of VFAs improved SNR compared with CFAs by 25% and 21% for the conventional and time‐encoded protocols, respectively. The VFA scheme also removed signal discontinuities in the time‐encoded data. Preliminary data suggest that optimizing the background suppression could improve in vivo SNR by a further 16%.ConclusionsTime encoding can be used to generate additional temporal information in ASL angiography. This enables the use of larger flip angles, which can double the SNR compared with a non‐time‐encoded protocol. The shortened time‐encoded readout can also lead to improved background suppression, reducing physiological noise and further improving SNR. |
| Related Links | https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC10091734&blobtype=pdf |
| Page Count | 19 |
| ISSN | 07403194 |
| Journal | Magnetic Resonance in Medicine [Magn Reson Med] |
| Volume Number | 89 |
| DOI | 10.1002/mrm.29491 |
| PubMed Central reference number | PMC10091734 |
| Issue Number | 4 |
| PubMed reference number | 36255158 |
| e-ISSN | 15222594 |
| Language | English |
| Publisher | John Wiley and Sons Inc. |
| Publisher Date | 2022-10-18 |
| Publisher Place | Hoboken |
| Access Restriction | Open |
| Rights License | This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2022 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine. |
| Subject Keyword | angiography arterial spin labeling Hadamard PCASL time‐encoded |
| Content Type | Text |
| Resource Type | Article |
| Subject | Radiology, Nuclear Medicine and Imaging |
