超低场(ULF)磁共振成像(MRI)具有使MRI更易于访问的潜力,鉴于其成本效益,降低功率要求,和便携性。然而,信噪比(SNR)随场强下降,需要具有较低分辨率和较长扫描时间的成像。这项研究介绍了一种新颖的基于傅立叶的超分辨率(FouSR)方法,旨在提高ULFMRI图像的分辨率,并最大程度地增加总扫描时间。FouSR组合来自各向异性分辨率的两个正交ULF图像的空间频率,以创建各向同性的T2加权流体衰减反演恢复(FLAIR)图像。我们假设FouSR可以有效地从欠采样切片方向恢复信息,从而改善多发性硬化症(MS)病变和其他重要解剖特征的描绘。重要的是,FouSR算法可以在扫描仪上实现,并改变k空间轨迹。配对ULF(超精细SWOOP,0.064特斯拉)和高场(西门子,Skyra,3特斯拉)在同一天从幻影和10名MS或疑似MS参与者(6名女性;平均±SD年龄:44.1±4.1)的队列中收集FLAIR扫描。沿冠状面和轴向面获取ULF扫描,具有1.7mm×1.7mm的平面分辨率,切片厚度为5mm。根据记录的ULF冠状和轴向扫描对FouSR进行评估,它们的平均值(ULF平均值)和黄金标准SR(ANTSSR)。与ULF冠状(36.7±12.2)相比,FouSR表现出更高的SNR(47.96±12.6),与ULF轴向(0.13±0.07)相比,病变的显著性(0.12±0.06),但与患者扫描中的其他方法相比,对比噪声比(CNR)没有任何显着差异。然而,与所有其他技术相比,FouSR显示出更高的图像清晰度(0.025±0.0040)(ULF冠状0.021±0.0037,q=5.9,p-adj。=0.011;ULF轴向0.018±0.0026,q=11.1,p-adj。=0.0001;ULF平均值0.019±0.0034,q=24.2,p-adj。<0.0001),与ULF平均值(-1.02±0.37,t(543)=-10.174,p=<0.0001)相比,病变清晰度(-0.97±0.31)更高。由三名经验丰富的MS神经科医生进行的平均盲法定性评估显示,FouSR和其他方法在WML和沟或gyri可视化方面没有显着差异。FouSR可以,原则上,在扫描仪上实施,以在飞行中以更高的分辨率产生临床上有用的FLAIR图像,为在MS中可视化病变和其他解剖结构提供了有价值的工具。
Ultra-low field (ULF) magnetic resonance imaging (MRI) holds the potential to make MRI more accessible, given its cost-effectiveness, reduced power requirements, and portability. However, signal-to-noise ratio (SNR) drops with field strength, necessitating imaging with lower resolution and longer scan times. This study introduces a novel Fourier-based Super Resolution (FouSR) approach, designed to enhance the resolution of ULF MRI images with minimal increase in total scan time. FouSR combines spatial frequencies from two orthogonal ULF images of anisotropic resolution to create an isotropic T2-weighted fluid-attenuated inversion recovery (FLAIR) image. We hypothesized that FouSR could effectively recover information from under-sampled slice directions, thereby improving the delineation of multiple sclerosis (MS) lesions and other significant anatomical features. Importantly, the FouSR algorithm can be implemented on the scanner with changes to the k-space trajectory. Paired ULF (Hyperfine SWOOP, 0.064 tesla) and high field (Siemens, Skyra, 3 Tesla) FLAIR scans were collected on the same day from a phantom and a cohort of 10 participants with MS or suspected MS (6 female; mean ± SD age: 44.1 ± 4.1). ULF scans were acquired along both coronal and axial planes, featuring an in-plane resolution of 1.7 mm × 1.7 mm with a slice thickness of 5 mm. FouSR was evaluated against registered ULF coronal and axial scans, their average (ULF average) and a gold standard SR (ANTs SR). FouSR exhibited higher SNR (47.96 ± 12.6) compared to ULF coronal (36.7 ± 12.2) and higher lesion conspicuity (0.12 ± 0.06) compared to ULF axial (0.13 ± 0.07) but did not exhibit any significant differences contrast-to-noise-ratio (CNR) compared to other methods in patient scans. However, FouSR demonstrated superior image sharpness (0.025 ± 0.0040) compared to all other techniques (ULF coronal 0.021 ± 0.0037, q = 5.9, p-adj. = 0.011; ULF axial 0.018 ± 0.0026, q = 11.1, p-adj. = 0.0001; ULF average 0.019 ± 0.0034, q = 24.2, p-adj. < 0.0001) and higher lesion sharpness (-0.97 ± 0.31) when compared to the ULF average (-1.02 ± 0.37, t(543) = -10.174, p = <0.0001). Average blinded qualitative assessment by three experienced MS neurologists showed no significant difference in WML and sulci or gyri visualization between FouSR and other methods. FouSR can, in principle, be implemented on the scanner to produce clinically useful FLAIR images at higher resolution on the fly, providing a valuable tool for visualizing lesions and other anatomical structures in MS.