Sreekanth M

PhD Scholar

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    • Phone no. (M): +91-9961942368

  • Research Focus : Parallel MRI Reconstruction.

Contextual Performance of GRAPPA Reconstruction: Implication to clinical Stroke Imaging.

Parallel MRI was established in 1980s. In conventional MR imaging, the phase-encoding steps are performed in sequential order by switching the magnetic field gradient step-by step, which in turn determines the speed of acquisition. Since the switching is expensive, acceleration is achieved by skipping alternate phase encoding lines. This was first implemented in 1989 by under sampling the k-space in PE direction. GRAPPA is a more generalized and improved version where acquired lines are linearly combined to estimate the missing line. The unacquired PE lines are then estimated from a linear combination of the acquired PE lines using one or more kernels computed using the calibrating signals.

My work emphasizes quality improvement of stroke and DTI images obtained after GRAPPA reconstruction. GRAPPA performance is analyzed in various non-ideal conditions. The non-ideal conditions include higher acceleration factor, increase in sensitivity noise and reduced number of calibration lines. For rapid acquisition of stroke images, higher acceleration factors and reduced number of calibration lines are needed. However aliasing artifacts in the reconstructed image increase with acceleration factor. The same thing also happens when the calibration lines are decreased. When more number of coils are used to add more data content, the sensitivity noise will also increase. The overall effect is the reduction in SNR and CNR, with increased artifact and blurring. Goal of my work is to overcome these difficulties and improve GRAPPA reconstruction in stroke imaging.

  • Madhusoodhanan, S. and Paul, J. S. (2016), A quantitative survey of GRAPPA reconstruction in parallel MRI: impact on noise reduction and aliasing. Concepts Magn Reson. doi:10.1002/cmr.a.21364