Department of Bioengineering, University of California Riverside, Riverside, California, USA.
Magn Reson Med. 2024 Jun;91(6):2320-2331. doi: 10.1002/mrm.29995. Epub 2024 Jan 3.
Background suppression (BS) is recommended in arterial spin labeling (ASL) for improved SNR but is difficult to optimize in existing velocity-selective ASL (VSASL) methods. Dual-module VSASL (dm-VSASL) enables delay-insensitive, robust, and SNR-efficient perfusion imaging, while allowing efficient BS, but its optimization has yet to be thoroughly investigated.
The inversion effects of the velocity-selective labeling pulses, such as velocity-selective inversion (VSI), can be used for BS, and were modeled for optimizing BS in dm-VSASL. In vivo experiments using dual-module VSI (dm-VSI) were performed to compare two BS strategies: a conventional one with additional BS pulses and a new one without any BS pulse. Their BS performance, temporal noise, and temporal SNR were examined and compared, with pulsed and pseudo-continuous ASL (PASL and PCASL) as the reference.
The in vivo experiments validated the BS modeling. Strong positive linear correlations (r > 0.82, p < 0.0001) between the temporal noise and the tissue signal were found in PASL/PCASL and dm-VSI. Optimal BS can be achieved with and without additional BS pulses in dm-VSI; the latter improved the ASL signals by 8.5% in gray matter (p = 0.006) and 12.2% in white matter (p = 0.014) and tended to provide better temporal SNR. The dm-VSI measured significantly higher ASL signal (p < 0.016) and temporal SNR (p < 0.018) than PASL and PCASL. Complex reconstruction was found necessary with aggressive BS.
Guided by modeling, optimal BS can be achieved without any BS pulse in dm-VSASL, further improving the ASL signal and the SNR performance.
背景抑制（BS）在动脉自旋标记（ASL）中被推荐用于提高 SNR，但在现有的速度选择 ASL（VSASL）方法中很难进行优化。双模块 VSASL（dm-VSASL）允许延迟不敏感、稳健和 SNR 高效的灌注成像，同时允许高效的 BS，但它的优化尚未得到彻底研究。
速度选择标记脉冲的反转效果，如速度选择反转（VSI），可用于 BS，并对其进行建模以优化 dm-VSASL 中的 BS。进行了双模块 VSI（dm-VSI）的体内实验，以比较两种 BS 策略：一种是具有附加 BS 脉冲的传统策略，另一种是没有任何 BS 脉冲的新策略。检查和比较了它们的 BS 性能、时间噪声和时间 SNR，以脉冲和伪连续 ASL（PASL 和 PCASL）为参考。
体内实验验证了 BS 建模。在 PASL/PCASL 和 dm-VSI 中，时间噪声与组织信号之间存在很强的正线性相关性（r>0.82，p<0.0001）。在 dm-VSI 中可以实现具有和不具有附加 BS 脉冲的最佳 BS；后者使灰质中的 ASL 信号提高了 8.5%（p=0.006），白质中的 ASL 信号提高了 12.2%（p=0.014），并倾向于提供更好的时间 SNR。dm-VSI 测量的 ASL 信号（p<0.016）和时间 SNR（p<0.018）明显高于 PASL 和 PCASL。激进的 BS 需要进行复杂的重建。
在 dm-VSASL 中，通过建模指导，可以在没有任何 BS 脉冲的情况下实现最佳 BS，进一步提高 ASL 信号和 SNR 性能。
