Spurious phase correction in rapid metabolic imaging

• Published in: Journal of magnetic resonance (1997) 2021-11, Vol.332 (107065), p.107065, Article 107065
• Main Authors: El Sabbagh, Nour, Chassain, Carine, Ratiney, Hélène, Pagés, Guilhem, Bonny, Jean-Marie
• Format: Article
• Language: English
• Subjects: Brain; Frequency commutation; Imaging, Three-Dimensional; Life Sciences; Magnetic Resonance Imaging; MRSI; Multi-shot imaging; Phantoms, Imaging; Phase correction; Phase Variation; Phase-coherent; Phase-continuous
• ISSN: 1090-7807; 1096-0856; 1096-0856
• DOI: 10.1016/j.jmr.2021.107065

[Display omitted] •Rapid multi-shot MRSI sequences may be subject to spurious phase accumulation.•Spurious phase accumulation leads to improper metabolite map reconstruction.•The rotating frame frequency during the echo time adds this unwanted phase.•It is therefore critical to know how the frequency is switched in the pulse sequence.•13C phantom IDEAL spiral acquisitions illustrate this often overlooked problem. IDEAL-type magnetic resonance spectroscopic imaging (MRSI) sequences require the acquisition of several datasets using optimized sampling in the time domain to reconstruct metabolite maps. Each unitary scan consists of a selective slice (2D) or slab (3D) excitation followed by an evolution time and then the acquisition of the spatially encoded signal. It is critical that the phase variation during the evolution time for each scan is only dependent on chemical shifts. In this paper, we described the apparition of spurious phase due to either the transmit or the receive frequency. The presence of this unwanted phase depends on (i) where the commutation between these two frequencies is performed and (ii) how it is done, as there are two phase commutation modes: continuous and coherent. We present the correction needed in function of the different cases. It appears that some solutions are universal. However, it is critical to know which case is implemented on the MRI scanner, which is not always easy information to have. We illustrated several cases with our preclinical MRI by using the IDEAL spiral method on a 13C phantom.