Objective: MRI’s T ₁ measures the rate nuclei in a magnetic field approach thermal equilibrium, dependent upon Water _total + hydration fraction, the latter the major source of uncertainty.

Methods: This paper explores the contribution of the hydration fraction within intracellular microtubules’ (MTS) compartment to edema, using MRI’s T _2, due to a theoretically described quantum function of dipole-dipole interactions between ordered water and MTS’ protein, tubulin, endowing a coherence of increased order, lower heat capacity, and complexity of functioning.

Results/discussion: MTS are hollow cylinders 10 ² –10 ³ nm in length, with 25 nm exterior/15 nm interior diameter(s); MTS represent 2–10% of brain’s protein; concentration in axons/dendrites is 200 × 10 ⁻⁶ M. Ordered water fills the MTS’s hollow core, 31% of MTS by volume. In rat studies using T ₂ , which can separate out ordered and non-ordered water fractions, the mean fraction size of ordered water with shortest T ₂ was 13%. In man, upper limits of just 100 ml, a 7–8% volume increase, are available to accommodate any brain edema, yet the low compliance of man’s evolutionary significant gray matter tolerates only a 1.5%, or 18 ml, increase.

Conclusion: In brain edema, the window to irreversibility is narrow; an inclusion of MTS’s quantum functioning of ordered water, and measurement of this separate and significant hydration fraction may bring options to management, and lead to the reversibility of life-threatening edema.

Conflict of interest: None declared.