1/T1 rho and low-field 1/T1 of tissue water protons arise from magnetization transfer to macromolecular solid-state broadened lines.
We argue that, for solutions of immobilized protein and for tissue, the dependence of 1/T1 of solvent protons on B(0) at low fields and 1/T1 rho on B1 for all B(0) are both manifestations of the same underlying phenomena: magnetization transfer between mobile water protons and solid-state broadened protein proton levels. Broadening causes rapid mixing of spin orientation within the transverse plane, at all B(0), unless B1 is greater than the protein internal field; this affects 1/T1 rho of solvent protons by magnetization transfer. Similarly, decreasing B(0) below the internal field mixes all orientations of magnetization, which affects the solvent proton low-field 1/T1 and high-field 1/T2.
Brown
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RD
IBM T.J. Watson Research Center, Yorktown Heights, New York 10598.
Koenig
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SH
D000818:Animals; D001834:Body Water; D002417:Cattle; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D011522:Protons; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D013154:Spleen / Q000378:metabolism*
D011522:Protons; D012710:Serum Albumin, Bovine