Dong Ying, Chang Zheng, Xie Guoxi, Whitehead Gregory, Ji Jim X
Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, USA.
Department of Radiation Oncology, Duke University, Durham, North Carolina, USA.
Magn Reson Med. 2015 Sep;74(3):716-26. doi: 10.1002/mrm.25453. Epub 2014 Sep 23.
To provide visualization of the brachytherapy seeds and differentiation with natural structures in MRI by taking advantage of their high magnetic susceptibility to generate positive-contrast images.
The method is based on mapping the susceptibility using an equivalent short-TE sequence and a kernel deconvolution algorithm with a regularized L1 minimization. An appealing aspect of the method is that signals from the surrounding areas where signal to noise ratio (SNR) is sufficiently high are used to derive the susceptibility of the seeds, even though the SNR in the immediate vicinity of the seeds can be extremely low due to rapid signal decay.
The method is tested using computer simulations and experimental data. Comparing to conventional methods, the proposed method improves seed definition by a factor of >70% in the experiments. It produces the enhanced contrast at the exact seed location, whereas methods based on susceptibility gradient mapping produce highlighted regions surrounding the seeds. The proposed method is capable to perform the function for a wide range of resolutions and SNRs.
The results show that the proposed method provides positive contrast for the seeds and correctly differentiates them from other structures that appear similar to the seeds on conventional magnitude images.
利用近距离放射治疗种子源的高磁化率生成正性对比图像，在磁共振成像（MRI）中实现对种子源的可视化并与自然结构进行区分。
该方法基于使用等效短回波时间序列和带有正则化L1最小化的内核去卷积算法来绘制磁化率。该方法的一个吸引人之处在于，即使种子源紧邻区域的信噪比由于信号快速衰减可能极低，但来自信噪比足够高的周围区域的信号仍被用于推导种子源的磁化率。
该方法通过计算机模拟和实验数据进行了测试。与传统方法相比，在实验中该方法将种子源的清晰度提高了70%以上。它在种子源的确切位置产生增强的对比度，而基于磁化率梯度映射的方法则在种子源周围产生高亮区域。该方法能够在广泛的分辨率和信噪比范围内发挥作用。
结果表明，所提出的方法为种子源提供了正性对比，并能将它们与在传统幅度图像上与种子源相似的其他结构正确区分开来。
