Water and lipid MRI of the Xenopus oocyte

Oocytes of Xenopus laevis are large, single cells that provide a promising model system for the exploration of the MR biophysics fundamental to more complex living systems. Previous studies have generally employed 2D spin-echo sequences with an image slice thickness greater than the thickness of the cellular volumes of interest. Also, the large cytoplasmic lipid signal has typically been ignored. This study describes separate, high-resolution 3D measurements of the water and lipid spin densities, T₁ and T₂ relaxation time constants, and the water apparent diffusion rate constant (ADC) in the Xenopus oocyte without significant partial volume artifacts. The lipid spin-density and values for water MR properties varied monotonically from the vegetal to animal poles, indicating that the border between the poles is not sharply demarcated. Regional water MR property values correlated with lipid signal intensity. Lipid-specific imaging is shown for which water suppression is achieved via high diffusion weighting in the imaging sequence.