Laplacian unwrapping can be very robust even with highly wrapped images but does so at the expense of accuracy. It typically unwraps with an error of low spatial variability. This can be a perfectly reasonable unwrapping technique for some applications such as QSM where the background field (low spatial variability) is subsequently removed. However, in applications such as shimming or qMRI where the accuracy is important, Laplacian unwrapping is not recommended.
Other unwrapping algorithms and softwares are listed below.
PRELUDE: Spatial unwrapping technique using region growing algorithm Jenkinson, 2003. SEGUE: Spatial unwrapping technique based on similar principles to Prelude with optimizations to improve the speed Karsa & Shmueli, 2019. BEST PATH: 3D unwrapping algorithm using spatial information to assess the quality of the phase data and unwrap high quality regions first. Abdul-Rahman et al., 2007 ROMEO: Unwrapping technique using temporal and spatial information to guide the path of unwrapping Dymerska et al., 2021. UMPIRE:Temporal unwrapping technique using unevenly spaced echoes to accurately unwrap phase images. This technique requires three or more echoes Robinson et al., 2014.
- Jenkinson, M. (2003). Fast, automated, N-dimensional phase-unwrapping algorithm. Magn. Reson. Med., 49(1), 193–197.
- Karsa, A., & Shmueli, K. (2019). SEGUE: A Speedy rEgion-Growing Algorithm for Unwrapping Estimated Phase. IEEE Trans. Med. Imaging, 38(6), 1347–1357.
- Abdul-Rahman, H. S., Gdeisat, M. A., Burton, D. R., Lalor, M. J., Lilley, F., & Moore, C. J. (2007). Fast and robust three-dimensional best path phase unwrapping algorithm. Appl. Opt., 46(26), 6623–6635.
- Dymerska, B., Eckstein, K., Bachrata, B., Siow, B., Trattnig, S., Shmueli, K., & Robinson, S. D. (2021). Phase unwrapping with a rapid opensource minimum spanning tree algorithm (ROMEO). Magn. Reson. Med., 85(4), 2294–2308.
- Robinson, S., Schödl, H., & Trattnig, S. (2014). A method for unwrapping highly wrapped multi-echo phase images at very high field: UMPIRE. Magn. Reson. Med., 72(1), 80–92.