ORCID Profile
0000-0003-3405-7227
Current Organisation
University of Hawai'i
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Publisher: Wiley
Date: 26-04-2021
DOI: 10.1002/NBM.4531
Abstract: In this work, we propose a free‐breathing magnetic resonance fingerprinting (MRF) method that can be used to obtain B 1 + ‐robust quantitative T 1 maps of the abdomen in a clinically acceptable time. A three‐dimensional MRF sequence with a radial stack‐of‐stars trajectory was implemented, and its k‐space acquisition ordering was adjusted to improve motion‐robustness in the context of MRF. The flip angle pattern was optimized using the Cramér–Rao Lower Bound, and the encoding efficiency of sequences with 300, 600, 900 and 1800 flip angles was evaluated. To validate the sequence, a movable multicompartment phantom was developed. Reference multiparametric maps were acquired under stationary conditions using a previously validated MRF method. Periodic motion of the phantom was used to investigate the motion‐robustness of the proposed sequence. The best performing sequence length (600 flip angles) was used to image the abdomen during a free‐breathing volunteer scan. When using a series of 600 or more flip angles, the estimated T 1 values in the stationary phantom showed good agreement with the reference scan. Phantom experiments revealed that motion‐related artifacts can appear in the quantitative maps and confirmed that a motion‐robust k‐space ordering is essential. The in vivo scan demonstrated that the proposed sequence can produce clean parameter maps while the subject breathes freely. Using this sequence, it is possible to generate B 1 + ‐robust quantitative maps of T 1 and B 1 + next to M 0 ‐weighted images under free‐breathing conditions at a clinically usable resolution within 5 min.
Publisher: Wiley
Date: 25-11-2019
DOI: 10.1002/MRM.28096
Publisher: Wiley
Date: 20-11-2019
DOI: 10.1002/MRM.28073
Abstract: The goal of this work is to demonstrate a method for the simultaneous acquisition of proton multiparametric maps (T 1 , T 2 , and proton density) and sodium density images in 1 single scan. We hope that the development of such capabilities will help to ease the implementation of sodium MRI in clinical trials and provide more opportunities for researchers to investigate metabolism through sodium MRI. We developed a sequence based on magnetic resonance fingerprinting (MRF), which contains interleaved proton ( 1 H) and sodium ( 23 Na) excitations followed by a simultaneous center‐out radial readout for both nuclei. The receive chain of a 7T scanner was modified to enable simultaneous acquisition of 1 H and 23 Na signal. The obtained signal‐to‐noise ratio (SNR) was evaluated, and the accuracy of both proton T 1 , T 2 , and and sodium density maps were verified in phantoms. Finally, the method was demonstrated in 2 healthy subjects. The SNR obtained using the simultaneous measurement was almost identical to single‐nucleus measurements ( % change). Similarly, the proton T 1 and T 2 maps remained stable (normalized root mean square error in T 1 ≈ 2.2%, in T 2 ≈ 1.4%, and ≈ 5.4%), which indicates that the proposed sequence and hardware have no significant effects on the signal from either nucleus. In vivo measurements corroborated these results and demonstrated the feasibility of our method for in vivo application. With the proposed approach, we were able to simultaneously acquire sodium density images in addition to proton T 1 , T 2 , and maps as well as proton density images.
Publisher: Wiley
Date: 31-12-2021
DOI: 10.1002/MRM.29135
Abstract: To develop a 3D MR technique to simultaneously acquire proton multiparametric maps (T 1 , T 2 , and proton density) and sodium density weighted images over the whole brain. We implemented a 3D stack‐of‐stars MR pulse sequence which consists of interleaved proton ( 1 H) and sodium ( 23 Na) excitations, tailored slice encoding gradients that can encode the same slice for both nuclei, and simultaneous readout with different radial trajectories ( 1 H, full‐radial 23 Na, center‐out radial). The receive chain of our 7T scanner was modified to enable simultaneous acquisition of 1 H and 23 Na signal. A heuristically optimized flip angle train was implemented for proton MR fingerprinting (MRF). The SNR and the accuracy of proton T 1 and T 2 were evaluated in phantoms. Finally, in vivo application of the method was demonstrated in five healthy subjects. The SNR for the simultaneous measurement was almost identical to that for the single‐nucleus measurements ( % change). The proton T 1 and T 2 maps remained similar to the results from a reference 2D MRF technique (normalized RMS error in T 1 ≈ 4.2% and T 2 ≈ 11.3%). Measurements in healthy subjects corroborated these results and demonstrated the feasibility of our method for in vivo application. The in vivo T 1 values measured using our method were lower than the results measured by other conventional techniques. With the 3D simultaneous implementation, we were able to acquire sodium and proton density weighted images in addition to proton T 1 , T 2 , and from 1 H MRF that covers the whole brain volume within 21 min.
Publisher: Elsevier BV
Date: 12-2018
No related grants have been discovered for Zidan Yu.