Large gains in SNR through the application of Shinnar-Le Roux RF pulse design to short-TR spin-echo fMRI acquisitions at 7 T

IF 2 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Magnetic resonance imaging Pub Date : 2026-06-01 Epub Date: 2026-02-06 DOI:10.1016/j.mri.2026.110639

Mukund Balasubramanian , Robert V. Mulkern , William A. Grissom , Jonathan R. Polimeni

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引用次数: 0

Abstract

Purpose

The optimal excitation flip angle (FA) for short-TR spin-echo acquisitions can be well above 90°, far beyond the small FAs suited for commonly-used sinc RF pulses. The goal of this study was to characterize the benefits of Shinnar-Le Roux (SLR) over sinc pulses for these acquisitions, which may lead to improvements in the temporal and spatial specificity of fMRI.

Methods

Slice profiles were obtained either through Bloch simulation or from scans of an oil phantom at 7 T (T₁/TR = 1500/300 ms). Spatial integrals of the slice profiles were used as measures of the resulting (relative) SNR. We also measured the spatial profile of spin-echo “linescan” acquisitions, which are of increasing interest for in vivo studies of cortical layers.

Results

For 2D acquisitions with the parameter values used here, the high-quality slice profiles provided by the SLR pulses resulted in an SNR gain of ∼100% relative to sinc pulses. For 1D linescan acquisitions, the SNR gains were even higher: ∼150%.

Conclusions

The large gains in SNR described here should enhance any studies using short-TR spin-echo acquisitions; in particular, we anticipate application of these SLR pulses to fMRI studies that target the microvasculature with both high spatial and high temporal resolution. Potential limitations, due to high SAR or B₁⁺ inhomogeneity, should however be kept in mind, especially at ultra-high field strengths.

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通过将Shinnar-Le Roux射频脉冲设计应用于7 T的短tr自旋回波fMRI采集，可大幅提高信噪比。

目的：用于短tr自旋回波采集的最佳激励翻转角（FA）可以远远超过90°，远远超过适用于常用的自旋射频脉冲的小FA。本研究的目的是表征sinnar - le Roux （SLR）相对于正弦脉冲的优势，这可能导致fMRI的时间和空间特异性的改善。方法：通过Bloch模拟或在7 T （T1/TR = 1500/300 ms）扫描油幻影获得切片剖面。切片剖面的空间积分被用作测量结果（相对）信噪比。我们还测量了自旋回波“线扫描”获取的空间剖面，这对皮层的体内研究越来越感兴趣。结果：对于使用本文参数值的二维采集，单反脉冲提供的高质量切片剖面相对于正弦脉冲产生了约100%的信噪比增益。对于一维线性扫描采集，信噪比增益甚至更高：约150%。结论：本文描述的信噪比的大幅提高应该加强任何使用短tr自旋回波采集的研究；特别是，我们期望将这些单反脉冲应用于以高空间和高时间分辨率为目标的微血管功能磁共振成像研究。然而，由于高SAR或B1+不均匀性，应牢记潜在的局限性，特别是在超高场强下。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Magnetic resonance imaging 医学-核医学

CiteScore

4.70

自引率

4.00%

发文量

194

审稿时长

83 days

期刊介绍： Magnetic Resonance Imaging (MRI) is the first international multidisciplinary journal encompassing physical, life, and clinical science investigations as they relate to the development and use of magnetic resonance imaging. MRI is dedicated to both basic research, technological innovation and applications, providing a single forum for communication among radiologists, physicists, chemists, biochemists, biologists, engineers, internists, pathologists, physiologists, computer scientists, and mathematicians.