Slice Selection Using Modulated Gradients for Fast 2D Single Point EPR Imaging

Nallathamby Devasahayam¹, Sankaran Subramanian¹, Shingo Matsumoto¹, Murali Cherukuri Krishna¹

We describe a novel slice selection strategy in 2D EPR imaging. Two and three dimensional in vivo EPR imaging and relaxation based oxymetry have been carried out routinely in our laboratory using the pure phase-encoding methodology of single point imaging, SPI. In this development we use the same imaging equipment operating at 300 MHz, with an additional provision of applying a low frequency (100 Hz) sinusoidal field along one of the gradient axes at nominal AC amplitude of about 1 mT/m. The modulation of the gradient along a particular axis introduces inhomogeneity along that axis everywhere except around the midpoint at which the amplitude is close to zero. A two dimensional phase encoding in a plane perpendicular to the axis of the modulated gradient retains coherent phase information only from the narrow slice at the center. Resolution of 5 mm and slice thickness of 5 mm is demonstrated.