Wu Yupeng, Pang Qifan, Wang Zhichao, Li Gaiying, Fu Caixia, Cao Mengqiu, Wang Xingrui, Jiang Dongmei, She Dejun, Song Yang, Zhao Yu, Li Jianqi
Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai, China.
Zhejiang Lab, Zhejiang, Hangzhou, China.
NMR Biomed. 2025 Sep;38(9):e70109. doi: 10.1002/nbm.70109.
To simultaneously fit multiple-pool effects, spectrally selective 3D chemical exchange saturation transfer (CEST) imaging typically requires single-shot readouts to save time. However, to date, fast low angle shot (FLASH) and echo planar imaging (EPI) have been the primary pulse sequences used for this purpose. They suffer from low signal-to-noise ratio (SNR) or image distortion related to B0 field inhomogeneity. In this work, we developed a 3D single-shot CEST sequence using true fast imaging with steady-state precession (True FISP) readout, also known as balanced steady state free precession (bSSFP), and optimized the scanning parameters through simulations. The performance of the CEST sequence was validated using an egg white phantom, 10 healthy volunteers, and two patients with brain tumors on a 3T human scanner. Subsequently, the proposed CEST sequence using True FISP was compared with the commonly used FLASH-based CEST sequence, focusing on SNR and image contrast, while maintaining identical pre-saturation modes, repetition time, echo time, and scan time. In the simulation experiments, the maximum CEST signal obtained from the True FISP was significantly greater than that obtained from the FLASH sequence. In the egg white phantom, the SNRs of amide proton transfer-weighted (APTw) and nuclear Overhauser enhancement (NOE) effect images obtained from the True FISP were 68.3% and 57.0% higher than those obtained from the FLASH sequence, respectively. In healthy volunteers, saturated images collected with the True FISP sequence at 3.5 ppm showed an approximately 84% increase in mean temporal SNR compared to those collected with the FLASH sequence. Compared to the FLASH sequence, the CEST images obtained from the True FISP sequence could display more detailed brain tissue structures of both normal individuals and patients with brain tumors. Therefore, due to the high SNR inherent in the sequence, True FISP has the potential to be used for fast and high-quality 3D image readout of CEST contrasts in clinical applications.
为了同时拟合多池效应，光谱选择性三维化学交换饱和转移（CEST）成像通常需要单激发读出以节省时间。然而，迄今为止，快速低角度激发（FLASH）和回波平面成像（EPI）一直是用于此目的的主要脉冲序列。它们存在信噪比（SNR）低或与B0场不均匀性相关的图像失真问题。在这项工作中，我们开发了一种使用稳态进动真快速成像（True FISP）读出的三维单激发CEST序列，也称为平衡稳态自由进动（bSSFP），并通过模拟优化了扫描参数。使用蛋清模型、10名健康志愿者和两名脑肿瘤患者在3T人体扫描仪上对CEST序列的性能进行了验证。随后，将所提出的使用True FISP的CEST序列与常用的基于FLASH的CEST序列进行比较，重点关注SNR和图像对比度，同时保持相同的预饱和模式、重复时间、回波时间和扫描时间。在模拟实验中，从True FISP获得的最大CEST信号明显大于从FLASH序列获得的信号。在蛋清模型中，从True FISP获得的酰胺质子转移加权（APTw）和核Overhauser增强（NOE）效应图像的SNR分别比从FLASH序列获得的高68.3%和57.0%。在健康志愿者中，与使用FLASH序列采集的饱和图像相比，使用True FISP序列在3.5 ppm处采集的饱和图像平均时间SNR提高了约84%。与FLASH序列相比，从True FISP序列获得的CEST图像可以显示正常个体和脑肿瘤患者更详细的脑组织结构。因此，由于该序列固有的高SNR，True FISP有潜力用于临床应用中快速、高质量的CEST对比度三维图像读出。
