NEW METHOD FOR CONTRAST MANIPULATION IN DNP-ENHANCED MRI

The magnetization subtraction technique (MS), which is equivalent to t he inversion recovery technique in strong magnetic fields, has been im plemented in dynamic nuclear polarization-enhanced magnetic resonance imaging (DNPI), The general theoretical basis of the MS method, which can be applied to DNPI or to prepolarized MRI in weak magnetic fields (such as Earth's magnetic field), is introduced, Details are provided about the signal amplitude, dynamic range of the method, and condition s required to observe signal void in samples with specific T-1 relaxat ion times, The experimental results obtained with MS DNPI are presente d and discussed, In the experiments, electron spin resonance irradiati on frequencies of 199 MHz and 16.2 MHz were employed, Also, T-1 contra st manipulation in the polarizing and in the detection magnetic field is discussed and demonstrated for MS DNPI.