{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T21:46:27Z","timestamp":1760132787937,"version":"build-2065373602"},"reference-count":34,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2023,10,12]],"date-time":"2023-10-12T00:00:00Z","timestamp":1697068800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Natural Sciences and Engineering Research Council (NSERC) of Canada"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Gradient-recalled echo (GRE) echo-planar imaging (EPI) is an efficient MRI pulse sequence that is commonly used for several enticing applications, including functional MRI (fMRI), susceptibility-weighted imaging (SWI), and proton resonance frequency (PRF) thermometry. These applications are typically not performed in the mid-field (&lt;1 T) as longer T2* and lower polarization present significant challenges. However, recent developments of mid-field scanners equipped with high-performance gradient sets offer the possibility to re-evaluate the feasibility of these applications. The paper introduces a metric \u201cT2* contrast efficiency\u201d for this evaluation, which minimizes dead time in the EPI sequence while maximizing T2* contrast so that the temporal and pseudo signal-to-noise ratios (SNRs) can be attained, which could be used to quantify experimental parameters for future fMRI experiments in the mid-field. To guide the optimization, T2* measurements of the cortical gray matter are conducted, focusing on specific regions of interest (ROIs). Temporal and pseudo SNR are calculated with the measured time-series EPI data to observe the echo times at which the maximum T2* contrast efficiency is achieved. T2* for a specific cortical ROI is reported at 0.5 T. The results suggest the optimized echo time for the EPI protocols is shorter than the effective T2* of that region. The effective reduction of dead time prior to the echo train is feasible with an optimized EPI protocol, which will increase the overall scan efficiency for several EPI-based applications at 0.5 T.<\/jats:p>","DOI":"10.3390\/s23208428","type":"journal-article","created":{"date-parts":[[2023,10,12]],"date-time":"2023-10-12T14:22:17Z","timestamp":1697120537000},"page":"8428","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Optimization of Gradient-Echo Echo-Planar Imaging for T2* Contrast in the Brain at 0.5 T"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3195-9623","authenticated-orcid":false,"given":"Arjama","family":"Halder","sequence":"first","affiliation":[{"name":"Department of Medical Biophysics, Western University, London, ON N6A 3K7, Canada"}]},{"given":"Chad T.","family":"Harris","sequence":"additional","affiliation":[{"name":"Synaptive Medical, Toronto, ON M5V 3B1, Canada"}]},{"given":"Curtis N.","family":"Wiens","sequence":"additional","affiliation":[{"name":"Synaptive Medical, Toronto, ON M5V 3B1, Canada"}]},{"given":"Andrea","family":"Soddu","sequence":"additional","affiliation":[{"name":"Western Institute for Neuroscience, Physics and Astronomy, Western University, London, ON N6A 3K7, Canada"}]},{"given":"Blaine A.","family":"Chronik","sequence":"additional","affiliation":[{"name":"Department of Medical Biophysics, Western University, London, ON N6A 3K7, Canada"},{"name":"Western Institute for Neuroscience, Physics and Astronomy, Western University, London, ON N6A 3K7, Canada"}]}],"member":"1968","published-online":{"date-parts":[[2023,10,12]]},"reference":[{"key":"ref_1","unstructured":"Panther, A., Thevathasen, G., Connell, I.R., Yao, Y., Wiens, C.N., Curtis, A.T., Bindseil, G.A., Harris, C.T., Beatty, P.J., and Stainsby, J.A. 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