Garach, Ravindra Mahendrakumar (2005-08). Robust phase sensitive inversion recovery imaging. Master's Thesis. Thesis uri icon

abstract

  • Inversion Recovery (IR) is a powerful tool for contrast manipulation in Mag- netic Resonance Imaging (MRI). IR can provide strong contrast between tissues with different values of T1 relaxation times. The tissue magnetization stored at an IR image pixel can take positive as well as negative values. The corresponding polarity information is contained in the phase of the complex image. Due to numerous factors associated with the Magnetic Resonance (MR) scanner and the associated acquisition system, the acquired complex image is modulated by a spatially varying background phase which makes the retrieval of polarity information non-trivial. Many commercial MR scanners perform magnitude-only reconstruction which, due to loss of polarity information, reduces the dynamic contrast range. Phase sensitive IR (PSIR) can provide enhanced image contrast by estimating and removing the background phase and retrieving the correct polarity information. In this thesis, the background phase of complex MR image is modeled using a statistical model based on Markov Ran- dom Fields (MRF). Two model optimization methods have been developed. The first method is a computationally effcient algorithm for finding semi-optimal solutions satisfying the proposed model. Using an adaptive model neighborhood, it can recon- struct low SNR images with slow phase variations. The second method presents a region growing approach which can handle images with rapid phase variations. Ex- perimental results using computer simulations and in vivo experiments show that the proposed method is robust and can perform successful reconstruction even in adverse cases of low signal to noise ratios (SNRs) and high phase variations.
  • Inversion Recovery (IR) is a powerful tool for contrast manipulation in Mag-
    netic Resonance Imaging (MRI). IR can provide strong contrast between tissues with
    different values of T1 relaxation times. The tissue magnetization stored at an IR
    image pixel can take positive as well as negative values. The corresponding polarity
    information is contained in the phase of the complex image. Due to numerous factors
    associated with the Magnetic Resonance (MR) scanner and the associated acquisition
    system, the acquired complex image is modulated by a spatially varying background
    phase which makes the retrieval of polarity information non-trivial. Many commercial
    MR scanners perform magnitude-only reconstruction which, due to loss of polarity
    information, reduces the dynamic contrast range. Phase sensitive IR (PSIR) can
    provide enhanced image contrast by estimating and removing the background phase
    and retrieving the correct polarity information. In this thesis, the background phase
    of complex MR image is modeled using a statistical model based on Markov Ran-
    dom Fields (MRF). Two model optimization methods have been developed. The first
    method is a computationally effcient algorithm for finding semi-optimal solutions
    satisfying the proposed model. Using an adaptive model neighborhood, it can recon-
    struct low SNR images with slow phase variations. The second method presents a
    region growing approach which can handle images with rapid phase variations. Ex-
    perimental results using computer simulations and in vivo experiments show that the
    proposed method is robust and can perform successful reconstruction even in adverse
    cases of low signal to noise ratios (SNRs) and high phase variations.

publication date

  • August 2005
  • August 2005