title: A pulse sequence optimization method for assessment of nucleus size in q-space analysis of idealized cells.
abstract: To adjust pulse sequences that produce diffusion-weighted MRI signals for increased sensitivity to nucleus size, the impulse-propagator method in q-space is applied to a spherical geometry that would describe each member of a collection of cells and their nuclei, with several possible representations of the extracellular space. The method is extended to allow propagation between nucleus, cytoplasm, and extracellular space through semi-permeable membranes, using an approximate adjustment of intra-compartment propagators. Diffraction patterns are first calculated for the three compartments separately, for PGSE and OGSE pulse sequences, and verified by comparison with Monte Carlo simulations. The detailed patterns from the separate compartments determine the q value for maximum contrast in the total signal between large and small nuclei, an optimization that is not accurate in a Gaussian Phase Distribution (GPD) approximation. Then diffraction patterns are calculated for the case of linked compartments with semi-permeable membranes. The treatment of permeability adequately estimates pulse-sequence parameters for maximum contrast in calculated signal as nucleus size varies.
authors: Thunder Bay Regional Research Institute, 290 Munro St., Thunder Bay, ON P7A 7T1, Canada; Department of Physics, Lakehead University, 955 Oliver Rd., Thunder Bay, ON P7B 5E1, Canada; Dept. of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO 80309-0311, United States. Electronic address: gregory.duane@colorado.edu.
authors: Gregory S
authors: GS
authors: Duane
authors: Thunder Bay Regional Research Institute, 290 Munro St., Thunder Bay, ON P7A 7T1, Canada.
authors: Yanwei
authors: Y
authors: Wang
authors: Thunder Bay Regional Research Institute, 290 Munro St., Thunder Bay, ON P7A 7T1, Canada.
authors: Blake R
authors: BR
authors: Walters
authors: Thunder Bay Regional Research Institute, 290 Munro St., Thunder Bay, ON P7A 7T1, Canada; Department of Physics, Lakehead University, 955 Oliver Rd., Thunder Bay, ON P7B 5E1, Canada.
authors: Jae K
authors: JK
authors: Kim
mesh_terms: D000465:Algorithms; D002463:Cell Membrane Permeability; D002467:Cell Nucleus / Q000648:ultrastructure*; D002477:Cells / Q000648:ultrastructure*; D003198:Computer Simulation; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008566:Membranes; D008954:Models, Biological; D009010:Monte Carlo Method
keywords: Diffraction pattern; Diffusion-weighted MRI; Impulse-propagator; Q-space