MRI assessment of multiple dipolar relaxation time ( T 1 D ) components in biological tissues interpreted with a generalized inhomogeneous magnetization transfer (ihMT) model

Victor N.D. Carvalho (1, 2) , Andreea Hertanu (1) , Axelle Grélard (3) , Samira Mchinda (1) , Lucas Soustelle (1) , Antoine Loquet (3) , Erick Dufourc (3) , Gopal Varma (4) , David C Alsop (4) , Pierre Thureau (2) , Olivier Girard (1) , Guillaume Duhamel (1)

1 CRMBM - Centre de résonance magnétique biologique et médicale
2 ICR - Institut de Chimie Radicalaire
3 CBMN - Chimie et Biologie des Membranes et des Nanoobjets
4 Beth Israel Deaconess - Harvard Medical School

T 1D , the relaxation time of dipolar order, is sensitive to slow motional processes. Thus T 1D is a probe for membrane dynamics and organization that could be used to characterize myelin, the lipid-rich membrane of axonal fibers. A mono-component T 1D model associated with a modified ihMT sequence was previously proposed for in vivo evaluation of T 1D with MRI. However, experiments have suggested that myelinated tissues exhibit multiple T 1D components probably due to a heterogeneous molecular mobility. A bi-component T 1D model is proposed and implemented. ihMT images of ex-vivo, fixed rat spinal cord were acquired with multiple frequency alternation rate. Fits to data yielded two T 1D s of about 500 µs and 10 ms. The proposed model seems to further explore the complexity of myelin organization compared to the previously reported mono-component T 1D model.

Keywords: Dipolar relaxation time; T 1D; Inhomogeneous magnetization transfer; ihMT; MRI contrast; Jeener-Broekaert; Myelin; Myelin Imaging

Domains: Life Sciences [q-bio]; Bioengineering; Imaging

Victor N.D. Carvalho, Andreea Hertanu, Axelle Grélard, Samira Mchinda, Lucas Soustelle, et al.. MRI assessment of multiple dipolar relaxation time ( T 1 D ) components in biological tissues interpreted with a generalized inhomogeneous magnetization transfer (ihMT) model. Journal of Magnetic Resonance, 2020, 311, pp.106668. ⟨10.1016/j.jmr.2019.106668⟩. ⟨hal-02456394⟩