Transverse relaxation in fixed tissue: Influence of temperature and resolution on image contrast in magnetic resonance microscopy. (5th May 2022)

• Record Type: Journal Article
• Authors: Meloche, Ryan; Vučković, Ivan; Mishra, Prasanna K.; Macura, Slobodan
• Is Part Of: NMR in biomedicine. Volume 35:Number 9(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-05
• Subjects: fixed tissue -- MRM -- NMR -- proton exchange -- resolution -- spin echo -- T2W -- temperature; Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.4747
• Languages: English
• ISSNs: 0952-3480

Abstract

Abstract : To describe transverse relaxation of water in fixed tissue, we propose a model of transverse relaxation accelerated by diffusion and exchange (TRADE) that assumes exchange between free (visible) and bound (invisible) water, which relax by the dipole–dipole interaction, chemical exchange, and translation in the field gradient. Depending on the prevailing mechanism, transverse relaxation time ( T 2 ) of water in fixed tissue could increase (when dipole–dipole interaction prevails) or decrease with temperature (when diffusion in the field gradient prevails). Chemical exchange can make T 2 even temperature independent. Also, variation of resolution from 100 to 15 μm/pxl (or less) affects effective transverse relaxation. T 2 steadily decreases with increased resolution ( T 2 ∝ ∆ x 2, ∆ x is the read direction resolution). TRADE can describe all of these observations (semi)quantitatively. The model has been experimentally verified on water phantoms and on formalin‐fixed zebrafish, mouse brain, and rabbit larynx tissues. TRADE could help predict optimal scanning parameters for high‐resolution MRM from much faster measurements at lower resolution. Abstract : Magnetic resonance On fixed tissue, magnetic resonance microscopy (MRM) is typically performed at room temperature using water protons as the principal source of signal. The imaging gradients in MRM are stronger than in MRI. This makes contrast and sensitivity of MRM images temperature and image resolution dependent. We proposed and tested a model (TRADE—transverse relaxation accelerated by diffusion and exchange) to describe the influence of temperature and resolution on image contrast in high‐resolution MRM of fixed tissue.