Whole-Cerebrum distortion-free three-dimensional pseudo-continuous arterial spin labeling at 7T

Chenyang Zhao, Xingfeng Shao, Qinyang Shou, Samantha J. Ma, Sayim Gokyar, Christina Graf, Rudolf Stollberger, Danny JJ Wang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Fulfilling potentials of ultrahigh field for pseudo-Continuous Arterial Spin Labeling (pCASL) has been hampered by B1/B0 inhomogeneities that affect pCASL labeling, background suppression (BS), and the readout sequence. This study aimed to present a whole-cerebrum distortion-free three-dimensional (3D) pCASL sequence at 7T by optimizing pCASL labeling parameters, BS pulses, and an accelerated Turbo-FLASH (TFL) readout. A new set of pCASL labeling parameters (Gave = 0.4 mT/m, Gratio = 14.67) was proposed to avoid interferences in bottom slices while achieving robust labeling efficiency (LE). An OPTIM BS pulse was designed based on the range of B1/B0 inhomogeneities at 7T. A 3D TFL readout with 2D-CAIPIRINHA undersampling (R = 2 × 2) and centric ordering was developed, and the number of segments (Nseg) and flip angle (FA) were varied in simulation to achieve the optimal trade-off between SNR and spatial blurring. In-vivo experiments were performed on 19 subjects. The results showed that the new set of labeling parameters effectively achieved whole-cerebrum coverage by eliminating interferences in bottom slices while maintaining a high LE. The OPTIM BS pulse achieved 33.3% higher perfusion signal in gray matter (GM) than the original BS pulse with a cost of 4.8-fold SAR. Incorporating a moderate FA (8°) and Nseg (2), whole-cerebrum 3D TFL-pCASL imaging was achieved with a 2 × 2 × 4 mm3 resolution without distortion and susceptibility artifacts compared to 3D GRASE-pCASL. In addition, 3D TFL-pCASL showed a good to excellent test-retest repeatability and potential of higher resolution (2 mm isotropic). The proposed technique also significantly improved SNR when compared to the same sequence at 3T and simultaneous multislice TFL-pCASL at 7T. By combining a new set of labeling parameters, OPTIM BS pulse, and accelerated 3D TFL readout, we achieved high resolution pCASL at 7T with whole-cerebrum coverage, detailed perfusion and anatomical information without distortion, and sufficient SNR.

Original languageEnglish
Article number120251
JournalNeuroImage
Volume277
DOIs
Publication statusPublished - 15 Aug 2023

Keywords

  • Arterial spin labeling (ASL)
  • Background suppression (BS)
  • Perfusion imaging
  • Pseudo-continuous arterial spin labeling (pCASL)
  • simultaneous multislice (SMS)
  • Turbo-FLASH (TFL)
  • Ultrahigh field

ASJC Scopus subject areas

  • Neurology
  • Cognitive Neuroscience

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