Regensburg 2004 – scientific programme
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AKB: Biologische Physik
AKB 50: Poster Session "Biological Physics"
AKB 50.108: Poster
Friday, March 12, 2004, 10:30–13:00, B
Geometrical parameters of periodical structures by 1H NMR — •Stefan Kirsch and Peter Bachert — Dept. of Medical Physics in Radiology, Deutsches Krebsforschungszentrum, Heidelberg, Germany
Some biological tissue, e.g., muscle and trabecular bone, contains periodical structures at different levels of organisation. Assessment of the corresponding geometrical parameters is possible on the basis of intermolecular dipole-dipole couplings. In liquid-state 1H NMR the distant dipolar field generated by the bulk of water protons can have a significant effect on the evolution of the magnetization. Application of the CRAZED sequence (two rf pulses, delay τ, gradient G) yields a train of echo signals at times nτ (n = 1, 2, ...) which are explained by intermolecular multiple-quantum coherences of the order n (Warren et al.) and which are generated by dipolar-coupled spins of mutual distance d = π/(γ Gτ). In periodical structures echo formation for n≠ 2 is only expected when d is a linear combination of the characteristic length scale λs of the structure: d = Σi li· (λs/2); li = ± 1, ± 2,... . With the purpose of possible application in vivo, we performed CRAZED experiments with tightly packed microcapillaries immersed in water in a 1.5-T whole-body MR tomograph (MAGNETOM Vision; Siemens). We demonstrate, that for n=1 and 3 information on λs of the structure can be obtained.