分类: 生物学 >> 生物物理学 提交时间: 2016-05-12
摘要: Radiofrequency (RF) coil arrays with high count of elements, e.g., closely spaced multi-row arrays, exhibit superior parallel imaging performance in magnetic resonance imaging (MRI). However, it is technically challenging and time-consuming to build multi-row arrays due to complex coupling issues. This paper presents a novel and simple method for closely spaced multi-row RF array designs. Induced current elimination decoupling method has shown the capability of reducing coupling between microstrip elements from different rows. In this study, its capability for decoupling array elements from the same row was investigated and validated by bench tests, with an isolation improvement from -8.9 to -20.7 dB. Based on this feature, a closely spaced double-row microstrip array with 16 elements was built at 7 T. S (21) between any two elements of the 16-channel closely spaced double-row microstrip array was better than -14 dB. In addition, its feasibility and performance was validated by MRI experiments. No significant image reconstruction-related noise amplifications were observed for parallel imaging even when reduced factor (R) achieves 4. The experimental results demonstrated that the proposed design might be a simple and efficient approach in fabricating closely spaced multi-row RF arrays.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-12
摘要: Purpose: To improve adaptive reconstruction of multichannel MR images by simultaneously removing nonsmooth phase and signal-loss imaging artifacts. Methods: The improved adaptive reconstruction consists of three steps: (1) modified multichannel images are first derived by dividing raw multichannel images by a reference image (i.e., a normalized single-channel image); (2) the modified multichannel images are smoothed by a low-pass filter; (3) adaptive spatial matched filters determined from the smoothed multichannel images are utilized to obtain multichannel combined images. Numerical simulations, as well as MRI experiments, on phantoms and human subjects are performed to evaluate and compare the effectiveness of this improved adaptive reconstruction approach against traditional coil combination methods. Results: Both simulation and MRI experimental results demonstrated that the proposed improved adaptive reconstruction method is able to obtain combined images with reduced nonsmooth phase and signal-loss imaging artifacts. Conclusions: A novel multichannel image reconstruction method is developed that produces high quality multichannel combined images. (C) 2015 American Association of Physicists in Medicine.