Jean-David Jutras1, Keith Wachowicz1,2, Nicola De Zanche1,2. 1. Department of Oncology, University of Alberta, Edmonton, Alberta, Canada. 2. Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada.
Abstract
PURPOSE: DESPOT2 is a single-component T2 mapping technique based on bSSFP imaging. It has seen limited application because of banding artifacts and magnetization transfer (MT) effects. In this work, acquisitions are optimized to minimize MT effects, while exact and approximate analytical equations enable automatic correction of banding artifacts within the T2 maps in mere seconds. THEORY AND METHODS: The technique was verified on an agar phantom at 3 tesla. The T2 resulting from four different data combination techniques was compared with the T2 from CPMG. Two comparable DESPOT2 scan protocols (short vs. long TR/TRF ) designed to minimize MT effects, were tested both in the phantom and in vivo. A third protocol was tested in the brain of 8 volunteers and analytical correction schemes were compared with DESPOT2-FM. RESULTS: The T2 measurements in agar agree with CPMG within ∼7% and in vivo results agree with values reported in the literature. The approximate analytical solutions provide increased robustness to hardware imperfections and higher T2 -to-noise ratio than the exact solutions. CONCLUSION: New analytical solutions enable fast and accurate whole-brain T2 mapping from previously measured T1 and B1 maps, and bSSFP images with at least two phase offsets and two flip angles (=4 datasets, 8 min scan). Magn Reson Med 76:1790-1804, 2016.
PURPOSE: DESPOT2 is a single-component T2 mapping technique based on bSSFP imaging. It has seen limited application because of banding artifacts and magnetization transfer (MT) effects. In this work, acquisitions are optimized to minimize MT effects, while exact and approximate analytical equations enable automatic correction of banding artifacts within the T2 maps in mere seconds. THEORY AND METHODS: The technique was verified on an agar phantom at 3 tesla. The T2 resulting from four different data combination techniques was compared with the T2 from CPMG. Two comparable DESPOT2 scan protocols (short vs. long TR/TRF ) designed to minimize MT effects, were tested both in the phantom and in vivo. A third protocol was tested in the brain of 8 volunteers and analytical correction schemes were compared with DESPOT2-FM. RESULTS: The T2 measurements in agar agree with CPMG within ∼7% and in vivo results agree with values reported in the literature. The approximate analytical solutions provide increased robustness to hardware imperfections and higher T2 -to-noise ratio than the exact solutions. CONCLUSION: New analytical solutions enable fast and accurate whole-brain T2 mapping from previously measured T1 and B1 maps, and bSSFP images with at least two phase offsets and two flip angles (=4 datasets, 8 min scan). Magn Reson Med 76:1790-1804, 2016.