Department of Radiology, Mayo Clinic, Rochester, 55905, Minnesota, USA.
Magn Reson Med. 2023 Oct;90(4):1547-1554. doi: 10.1002/mrm.29747. Epub 2023 Jun 22.
To show that the acoustic noise of spiral MRI can be reduced by derating the gradients with minimal penalty to image quality and scan time, and to illustrate an algorithm for optimal choice of derating parameters.
Acoustic noise level was measured and compared for various values of maximum gradient amplitude and slew rate for T -weighted spin-echo spiral scans while maintaining image contrast, FOV and resolution, and readout time. A full gradient trajectory and a derated gradient (undersampled) trajectory were chosen for a volunteer scan followed by parallel imaging-aided reconstruction to illustrate comparable image SNR. Two auto-derating methods, which prioritize slew rate and gradient amplitude, respectively, were derived using analytical results from the WHIRLED PEAS variant of spiral waveforms and compared in their acoustic noise level under test use cases.
Derating the gradients made the scan quieter by 16.6 dB(A) on average than a full gradient trajectory and required an undersampling factor R = 2 in order to maintain scan time, with no appreciable penalty in image SNR. Prioritizing reduced slew rate resulted in maximal loudness reduction.
Scanner gradients can often be derated to reduce the acoustic noise for spiral MRI with minimal penalty in scan time and image quality with the help of parallel imaging. An automatic slew-priority derating method that maximizes loudness reduction is given.
展示通过降低梯度的额定值来降低螺旋 MRI 的声噪声，同时对图像质量和扫描时间的影响最小，并说明一种用于最佳选择降额参数的算法。
在保持图像对比度、视野和分辨率以及读出时间不变的情况下，测量并比较了各种最大梯度幅度和斜率值的 T 加权自旋回波螺旋扫描的声噪声水平。为志愿者扫描选择了全梯度轨迹和降额梯度（欠采样）轨迹，然后进行并行成像辅助重建，以说明可比的图像 SNR。使用螺旋波形的 WHIRLED PEAS 变体的分析结果推导出了两种自动降额方法，分别优先考虑斜率和梯度幅度，并在测试用例下比较它们的声噪声水平。
与全梯度轨迹相比，梯度降额平均使扫描安静 16.6dB(A)，并且为了保持扫描时间，需要一个 2 的欠采样因子 R，图像 SNR 没有明显的损失。降低斜率优先可实现最大的响度降低。
在并行成像的帮助下，螺旋 MRI 的扫描梯度通常可以降低额定值以降低声噪声，同时对扫描时间和图像质量的影响最小。给出了一种自动降低斜率优先的降额方法，可最大限度地降低响度。
