Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
German Cancer Consortium Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Sci Rep. 2018 Jul 13;8(1):10631. doi: 10.1038/s41598-018-28894-w.
Magnetic resonance imaging (MRI) provides excellent cross-sectional images of the soft tissues in patients. Unfortunately, MRI is intrinsically slow, it exposes patients to severe acoustic noise levels, and is limited in the visualization of certain tissues such as bone. These limitations are partly caused by the timing structure of the MRI exam which first generates the MR signal by a strong radio-frequency excitation and later acquires the weak MRI signal. Concurrent excitation and acquisition (CEA) can overcome these limitations, but is extremely challenging due to the huge intensity difference between transmit and receive signal (up to 100 dB). To suppress the strong transmit signals during signal reception, a fully automated analog cancellation unit was designed. On a 3 Tesla clinical MRI system we achieved an on-resonance analog isolation of 90 dB between the transmit and receive path, so that CEA images of the head and the extremities could be acquired with an acquisition efficiency of higher than 90% at sound pressure levels close to background noise. CEA with analog cancellation might provide new opportunities for MRI in tissues with very short T relaxation times, and it offers a silent and time-efficient MRI acquisition.
磁共振成像（MRI）可提供患者软组织的出色横断图像。不幸的是，MRI 本质上速度较慢，会使患者暴露在强烈的声噪水平下，并且在某些组织（例如骨骼）的可视化方面受到限制。这些限制部分是由于 MRI 检查的时间结构引起的，该结构首先通过强射频激发产生 MR 信号，然后获取较弱的 MRI 信号。同时激发和采集（CEA）可以克服这些限制，但由于发射和接收信号之间的强度差异巨大（高达 100dB），因此极具挑战性。为了在信号接收过程中抑制强发射信号，设计了一个全自动模拟消除单元。在 3T 临床 MRI 系统上，我们在发射和接收路径之间实现了 90dB 的共谐模拟隔离，因此可以在接近背景噪声的声压级下以高于 90％的采集效率获取头部和四肢的 CEA 图像。具有模拟消除的 CEA 可能为 T1 弛豫时间非常短的组织中的 MRI 提供新的机会，并且提供无声且高效的 MRI 采集。
