Youngdee Wiwat, Lurie David J, Foster Margaret A
Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Foresterhill, UK.
Phys Med Biol. 2002 Apr 7;47(7):1091-100. doi: 10.1088/0031-9155/47/7/307.
A new pulse sequence for rapid imaging of free radicals is presented which combines snapshot imaging methods and conventional field-cycled proton electron double resonance imaging (FC-PEDRI). The new sequence allows the number of EPR irradiation periods to be optimized to obtain an acceptable SNR and spatial resolution of free radical distribution in the final image while reducing the RF power deposition and increasing the temporal resolution. Centric reordered phase encoding has been employed to counter the problem of rapid decay of the Overhauser-enhanced signal. A phase-correction scheme has also been used to correct problems arising from instability of the magnetic field following field-cycling. In vivo experiments were carried out using triaryl methyl free radical contrast agent, injected at a dose of 0.214 mmol kg(-1) body weight in anaesthetized adult male Sprague-Dawley rats. Transaxial images through the abdomen were collected using 1, 2, 4 and 8 EPR irradiation periods. Using 4 EPR irradiation periods it was possible to generate free radical distributions of acceptable SNR and resolution. The EPR power deposition is reduced by a factor of 16 and the acquisition time is reduced by a factor of 4 compared to an acquisition using the conventional FC-PEDRI pulse sequence.
本文提出了一种用于自由基快速成像的新脉冲序列，该序列结合了快照成像方法和传统的场循环质子电子双共振成像（FC-PEDRI）。新序列能够优化电子顺磁共振（EPR）辐照周期的数量，以便在最终图像中获得可接受的信噪比（SNR）和自由基分布的空间分辨率，同时降低射频功率沉积并提高时间分辨率。采用中心重排序相位编码来解决奥弗豪泽增强信号快速衰减的问题。还使用了一种相位校正方案来校正场循环后磁场不稳定所产生的问题。在体内实验中，使用三芳基甲基自由基造影剂，以0.214 mmol kg(-1)体重的剂量注射到麻醉的成年雄性Sprague-Dawley大鼠体内。使用1、2、4和8个EPR辐照周期收集穿过腹部的横断面图像。使用4个EPR辐照周期可以生成具有可接受的SNR和分辨率的自由基分布。与使用传统FC-PEDRI脉冲序列采集相比，EPR功率沉积降低了16倍，采集时间减少了4倍。
