Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21287, USA.
J Magn Reson Imaging. 2011 Jun;33(6):1330-40. doi: 10.1002/jmri.22571.
To develop and evaluate a practical method for the quantification of signal-to-noise ratio (SNR) on coronary MR angiograms (MRA) acquired with parallel imaging.
To quantify the spatially varying noise due to parallel imaging reconstruction, a new method has been implemented incorporating image data acquisition followed by a fast noise scan during which radiofrequency pulses, cardiac triggering and navigator gating are disabled. The performance of this method was evaluated in a phantom study where SNR measurements were compared with those of a reference standard (multiple repetitions). Subsequently, SNR of myocardium and posterior skeletal muscle was determined on in vivo human coronary MRA.
In a phantom, the SNR measured using the proposed method deviated less than 10.1% from the reference method for small geometry factors (≤2). In vivo, the noise scan for a 10 min coronary MRA acquisition was acquired in 30 s. Higher signal and lower SNR, due to spatially varying noise, were found in myocardium compared with posterior skeletal muscle.
SNR quantification based on a fast noise scan is a validated and easy-to-use method when applied to three-dimensional coronary MRA obtained with parallel imaging as long as the geometry factor remains low.
开发并评估一种用于定量分析并行成像采集冠状动脉磁共振血管造影（MRA）信号噪声比（SNR）的实用方法。
为了量化由于并行成像重建而产生的空间变化噪声，我们实现了一种新方法，该方法包括图像数据采集以及在快速噪声扫描期间禁用射频脉冲、心脏触发和导航门控。该方法的性能在体模研究中进行了评估，其中 SNR 测量值与参考标准（多次重复）进行了比较。随后，我们在体内冠状动脉 MRA 上确定了心肌和后骨骼肌肉的 SNR。
在体模中，对于小几何因子（≤2），使用所提出的方法测量的 SNR 与参考方法的偏差小于 10.1%。在体内，对于 10 分钟的冠状动脉 MRA 采集，噪声扫描可在 30 秒内完成。与后骨骼肌肉相比，由于空间变化的噪声，心肌的信号更高，SNR 更低。
基于快速噪声扫描的 SNR 定量分析是一种经过验证且易于使用的方法，当应用于并行成像采集的三维冠状动脉 MRA 时，只要几何因子保持较低，就可以使用该方法。
