¹H spectroscopic imaging of human brain at 3 Tesla: Comparison of fast three‐dimensional magnetic resonance spectroscopic imaging techniques

Abstract

Purpose:To investigate the signal-to-noise-ratio (SNR) and data quality of time-reduced three-dimensional (3D) proton magnetic resonance spectroscopic imaging ( 1 H MRSI) techniques in the human brain at 3 Tesla. Materials and Methods:Techniques that were investigated included ellipsoidal k-space sampling, parallel imaging, and echo-planar spectroscopic imaging (EPSI). The SNR values for N-acetyl aspartate, choline, creatine, and lactate or lipid peaks were compared after correcting for effective spatial resolution and acquisition time in a phantom and in the brains of human volunteers. Other factors considered were linewidths, metabolite ratios, partial volume effects, and subcutaneous lipid contamination. Results:In volunteers, the median normalized SNR for parallel imaging data decreased by 34 -42%, but could be significantly improved using regularization. The normalized signal to noise loss in flyback EPSI data was 11-18%. The effective spatial resolutions of the traditional, ellipsoidal, sensitivity encoding (SENSE) sampling scheme, and EPSI data were 1.02, 2.43, 1.03, and 1.01 cm 3 , respectively. As expected, lipid contamination was variable between subjects but was highest for the SENSE data. Patient data obtained using the flyback EPSI method were of excellent quality. Conclusion:Data from all 1 H 3D-MRSI techniques were qualitatively acceptable, based upon SNR, linewidths, and metabolite ratios. The larger field of view obtained with the EPSI methods showed negligible lipid aliasing with acceptable SNR values in less than 9.5 min without compromising the point-spread function.

Compressive Sensing Could Accelerate1H MR Metabolic Imaging in the Clinic

“…Several other fast chemical shift imaging and spectroscopic imaging approaches have been developed in the past and compared theoretically (23) and experimentally (24). In particular, echo-planar spectroscopic imaging (25,26) is a powerful spectroscopic imaging technique that remains underutilized in the clinic (27).…”

Multimodal Mass Spectrometric Imaging of Small Molecules Reveals Distinct Spatio-Molecular Signatures in Differentially Metastatic Breast Tumor Models

“…Sectioned samples from biopsies or other biological materials can be directly analyzed without the need for chemical labeling or extended sample preparation, and hundreds of biomolecules can be detected on a single tissue slide. Secondary ion mass spectrometry (SIMS) and matrix assisted laser desorption ionization (MALDI) are able to detect molecular distributions on histological tissue sections (28) at high spatial resolution, reaching spatial resolutions bellow 50 μm with MALDI-MS imaging and in the sub-micrometer range with SIMS (29, 30), while in-vivo MRSI provides 500 μm spatial resolution (31). Here, we have developed an approach using complementary desorption and ionization techniques directly applied on tissue obtained from breast cancer xenograft models.…”

MR Spectroscopic Imaging

“…The use of a rectangular FOV could also save up to 30 % (Golay et al 2002) resulting in a total acquisition time between 10 and 15 min. Further reduction in acquisition time can be achieved with fast imaging techniques like echo planar spectroscopic imaging (EPSI) and parallel imaging method (Posse et al 1995;Zierhut et al 2009;Ozturk et al 2006;Sabati et al 2014) or multiple spin-echo spectroscopic imaging (MSESI) (Duyn and Moonen 1993). These techniques scan more than one phase encoding step for a single excitation pulse, providing the respective acceleration factors, and allow acquisition of 3D MRSI data with sufficient spatial resolution in reasonable scan time.…”