{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,9,12]],"date-time":"2026-09-12T13:07:46Z","timestamp":1789218466170,"version":"build-2803163510"},"posted":{"date-parts":[[2026,9,9]]},"group-title":"Bioengineering","reference-count":53,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T00:00:00Z","timestamp":1788912000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/"}],"funder":[{"name":"Intramural Research Program (IRP) of the National Institute of Child Health and Human Development","award":["1-ZIA-HD008971-07"],"award-info":[{"award-number":["1-ZIA-HD008971-07"]}]},{"name":"National Institute of Neurological Diseases and Stroke Intramural Research Program","award":["ZIC-NS009450"],"award-info":[{"award-number":["ZIC-NS009450"]}]},{"name":"Department of War in the Military Traumatic Brain Injury Initiative","award":["HU0001-22-2-0058"],"award-info":[{"award-number":["HU0001-22-2-0058"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,9,9]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:sec>\n                  <jats:title>Purpose<\/jats:title>\n                  <jats:p>\n                    To demonstrate the feasibility of whole-brain multidimensional\n                    <jats:italic>T<\/jats:italic>\n                    <jats:sub>1<\/jats:sub>\n                    -\n                    <jats:italic>T<\/jats:italic>\n                    <jats:sub>2<\/jats:sub>\n                    relaxation imaging on a portable 0.064 T MRI scanner.\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Methods<\/jats:title>\n                  <jats:p>\n                    A two-dimensional inversion-recovery, fast spin-echo acquisition was used to jointly encode\n                    <jats:italic>T<\/jats:italic>\n                    <jats:sub>1<\/jats:sub>\n                    and\n                    <jats:italic>T<\/jats:italic>\n                    <jats:sub>2<\/jats:sub>\n                    relaxation. Joint relaxation distributions were reconstructed voxel-wise using marginal-distribution constrained optimization (MADCO). The approach was evaluated in a quantitative relaxation MRI phantom and subsequently applied\n                    <jats:italic>in vivo<\/jats:italic>\n                    in a healthy volunteer. Joint distributions, marginal distributions, distribution-derived measures, and statistical dependencies between the two relaxation dimensions were examined.\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Results<\/jats:title>\n                  <jats:p>\n                    Phantom joint relaxation estimates showed good overall agreement with mono-exponential relaxation measurements and previously reported values at 0.064 T. The\n                    <jats:italic>in vivo<\/jats:italic>\n                    acquisition provided whole-brain coverage over a broad range of relaxation weightings and tissue contrasts. Reconstructed joint\n                    <jats:italic>T<\/jats:italic>\n                    <jats:sub>1<\/jats:sub>\n                    -\n                    <jats:italic>T<\/jats:italic>\n                    <jats:sub>2<\/jats:sub>\n                    distributions showed spatially organized features across the relaxation space, including broad and overlapping relaxation components that were not fully represented by single-value relaxation maps or by either 1D marginal distribution alone. Selected regions of the joint relaxation space produced component maps with distinct spatial patterns. Statistical analysis further showed a dependence between the two relaxation dimensions, supporting the presence of added information in the joint distribution that is lost when treating\n                    <jats:italic>T<\/jats:italic>\n                    <jats:sub>1<\/jats:sub>\n                    and\n                    <jats:italic>T<\/jats:italic>\n                    <jats:sub>2<\/jats:sub>\n                    separately.\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Conclusion<\/jats:title>\n                  <jats:p>\n                    Whole-brain multidimensional\n                    <jats:italic>T<\/jats:italic>\n                    <jats:sub>1<\/jats:sub>\n                    -\n                    <jats:italic>T<\/jats:italic>\n                    <jats:sub>2<\/jats:sub>\n                    relaxation imaging is clinically feasible on a portable 0.064 T MRI scanner. Joint relaxation distributions provide information beyond single-value relaxation mapping and may support further developments of quantitative multidimensional imaging at ultra-low field.\n                  <\/jats:p>\n                <\/jats:sec>","DOI":"10.64898\/2026.09.04.749459","type":"posted-content","created":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T12:40:26Z","timestamp":1788957626000},"source":"Crossref","is-referenced-by-count":0,"title":["Multidimensional\n                  <i>T<\/i>\n                  <sub>1<\/sub>\n                  -\n                  <i>T<\/i>\n                  <sub>2<\/sub>\n                  Relaxation Imaging\n                  <i>In Vivo<\/i>\n                  on a Portable 0.064 T MRI Scanner"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6025-8666","authenticated-orcid":false,"given":"Ella","family":"Wilczynski","sequence":"first","affiliation":[{"name":"Section on Quantitative Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health, Bethesda, MD, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kulam Najmudeen","family":"Magdoom","sequence":"additional","affiliation":[{"name":"Section on Quantitative Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health, Bethesda, MD, USA"},{"name":"The Military Traumatic Brain Injury Initiative (MTBI2), Uniformed Services University of the Health Sciences, Bethesda, MD, USA"},{"name":"The Henry M. Jackson Foundation for the Advancement of Military Medicine (HJF) Inc., Bethesda, MD, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0295-601X","authenticated-orcid":false,"given":"Alexandru V","family":"Avram","sequence":"additional","affiliation":[{"name":"Section on Quantitative Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health, Bethesda, MD, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0221-9121","authenticated-orcid":false,"given":"Nathan H","family":"Williamson","sequence":"additional","affiliation":[{"name":"Section on Quantitative Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health, Bethesda, MD, USA"},{"name":"The Military Traumatic Brain Injury Initiative (MTBI2), Uniformed Services University of the Health Sciences, Bethesda, MD, USA"},{"name":"The Henry M. 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