Rebecca E Feldman1, Priti Balchandani2. 1. Translational and Molecular Imaging Institution, Icahn School of Medicine at Mount Sinai, New York, New York, USA. rebecca.feldman2@mountsinai.org. 2. Translational and Molecular Imaging Institution, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
Abstract
PURPOSE: MR spectroscopic imaging (MRSI) benefits from operation at 7T due to increased signal-to-noise ratio (SNR) and spectral separation. The 180° radiofrequency (RF) pulses used in the conventional MRSI sequences are particularly susceptible to the variation in the transmitted RF (B1 ) field and severe chemical shift localization errors at 7T. RF power deposition, as measured by specific absorption rate (SAR), also increases with field strength. Adiabatic 180° RF pulses may mitigate the effects of B1 variation. We designed and implemented a semiadiabatic spectral-spatial spectroscopic imaging (SASSI) pulse sequence to provide more uniform spectral data at 7T with reduced SAR. METHODS: The adiabatic Shinnar-Le Roux algorithm was used to generate a high bandwidth 180° adiabatic spectral-spatial (SPSP) pulse that captured a spectral range containing the main metabolites of interest. A pair of 180° SPSP pulses was used to refocus the signal excited by a 90° SPSP pulse in order to select a 3D volume of interest in the SASSI sequence. RESULTS: The SASSI pulse sequence produced spectra with more uniform brain metabolite SNR when compared with the conventional nonadiabatic MRSI sequence. CONCLUSION: SASSI achieved comparable SNR to the current adiabatic alternative, semi-LASER, but with 1/3 of the SAR. Magn Reson Med 76:1071-1082, 2016.
PURPOSE: MR spectroscopic imaging (MRSI) benefits from operation at 7T due to increased signal-to-noise ratio (SNR) and spectral separation. The 180° radiofrequency (RF) pulses used in the conventional MRSI sequences are particularly susceptible to the variation in the transmitted RF (B1 ) field and severe chemical shift localization errors at 7T. RF power deposition, as measured by specific absorption rate (SAR), also increases with field strength. Adiabatic 180° RF pulses may mitigate the effects of B1 variation. We designed and implemented a semiadiabatic spectral-spatial spectroscopic imaging (SASSI) pulse sequence to provide more uniform spectral data at 7T with reduced SAR. METHODS: The adiabatic Shinnar-Le Roux algorithm was used to generate a high bandwidth 180° adiabatic spectral-spatial (SPSP) pulse that captured a spectral range containing the main metabolites of interest. A pair of 180° SPSP pulses was used to refocus the signal excited by a 90° SPSP pulse in order to select a 3D volume of interest in the SASSI sequence. RESULTS: The SASSI pulse sequence produced spectra with more uniform brain metabolite SNR when compared with the conventional nonadiabatic MRSI sequence. CONCLUSION: SASSI achieved comparable SNR to the current adiabatic alternative, semi-LASER, but with 1/3 of the SAR. Magn Reson Med 76:1071-1082, 2016.
Authors: Charles H Cunningham; Daniel B Vigneron; Albert P Chen; Duan Xu; Ralph E Hurd; Napapon Sailasuta; John M Pauly Journal: Magn Reson Med Date: 2004-07 Impact factor: 4.668
Authors: Jun Ma; Carrie Wismans; Zhipeng Cao; Dennis W J Klomp; Jannie P Wijnen; William A Grissom Journal: Magn Reson Med Date: 2017-03-31 Impact factor: 4.668
Authors: L McCarthy; G Verma; G Hangel; A Neal; B A Moffat; J P Stockmann; O C Andronesi; P Balchandani; C G Hadjipanayis Journal: AJNR Am J Neuroradiol Date: 2022-05-26 Impact factor: 4.966