Abstract
PurposeTo compare a new parallel imaging (PI) method for multislice proton magnetic resonance spectroscopic imaging (1H‐MRSI), termed (2 + 1)D‐CAIPIRINHA, with two standard PI methods: 2D‐GRAPPA and 2D‐CAIPIRINHA at 7 Tesla (T).Methods(2 + 1)D‐CAIPIRINHA is a combination of 2D‐CAIPIRINHA and slice‐CAIPIRINHA. Eight healthy volunteers were measured on a 7T MR scanner using a 32‐channel head coil. The best undersampling patterns were estimated for all three PI methods. The artifact powers, g‐factors, Cramér–Rao lower bounds (CRLB), and root mean square errors (RMSE) were compared quantitatively among the three PI methods. Metabolic maps and spectra were compared qualitatively.Results(2 + 1)D‐CAIPIRINHA allows acceleration in three spatial dimensions in contrast to 2D‐GRAPPA and 2D‐CAIPIRINHA. Thus, this sequence significantly decreased the RMSE of the metabolic maps by 12.1 and 6.9%, on average, for 4 < R < 11, compared with 2D‐GRAPPA and 2D‐CAIPIRINHA, respectively. The artifact power was 22.6 and 8.4% lower, and the CRLB were 3.4 and 0.6% lower, respectively.Conclusion(2 + 1)‐CAIPIRINHA can be implemented for multislice MRSI in the brain, enabling higher accelerations than possible with two‐dimensional (2D) parallel imaging methods. An eight‐fold acceleration was still feasible in vivo with negligible PI artifacts with lipid decontamination, thus decreasing the measurement time from 120 to 15 min for a 64 × 64 × 4 matrix. Magn Reson Med 78:429–440, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.
Highlights
Proton magnetic resonance spectroscopic imaging (1HMRSI) can aid in the diagnosis of several brain diseases, such as tumors [1,2], multiple sclerosis [3,4], or mild traumatic brain injuries [5]
We proposed a new parallel imaging (PI) method for multislice 2D-1H-MR spectroscopic imaging (MRSI) that accelerates in all three spatial dimensions
Taking advantage of such acceleration results in maximal exploitation of the sensitivity variations of the AC, leading to expected reconstruction improvements over conventional PI methods. This theoretical expectation was confirmed by this study, as the proposed method provides lower artifact power (AP), g-factor, root mean square errors (RMSE), and Cramer–Rao lower bounds (CRLB) values, compared with 2D-GRAPPA and 2D-CAIPIRINHA
Summary
Proton magnetic resonance spectroscopic imaging (1HMRSI) can aid in the diagnosis of several brain diseases, such as tumors [1,2], multiple sclerosis [3,4], or mild traumatic brain injuries [5]. PI techniques were shown to be versatile tools for accelerating phase-encoding [21,22,23], as well as slice encoding in multislice sequences [24]. Aid of the intrinsic signal localization of the individual AC elements, ie, different sensitivity profiles for different AC elements, and additional calibration data This reconstruction can be performed either in k-space (GRAPPA) or in the image domain (SENSE). The performance of PI was shown to improve with the magnetic field strength [27], whereas some ultra-high-resolution SSE MRSI sequences are slightly less efficient at very high magnetic fields [9]. We propose (2 þ 1)D-CAIPIRINHA as a combination of 2D-CAIPIRINHA along the two axial phaseencoding directions, and slice-CAIPIRINHA along the slice-encoded third dimension, to accelerate multislice 1H-MRSI acquisitions. A similar method can be used for three-dimensional (3D) 1H-MRSI
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
