[Measuring the contrast-enhancement in the skin and subcutaneous fatty tissue with the NMR-MOUSE: a feasibility study]. / Messung der Kontrastmittelanreicherung in der Haut und im subkutanen Fettgewebe mit der NMR-MOUSE -- eine Machbarkeitsstudie.

PURPOSE: The NMR-MOUSE is an open and mobile sensor for measuring NMR relaxation parameters in organic matters. T1-measurements of the subcutaneous fatty tissue and the skin are reported. MATERIAL AND METHOD: For the first time, the NMR-MOUSE was employed to measure the signal recovery following saturation of the skin and the subcutaneous fatty tissue of three patients, before and after administering a contrast agent. RESULTS: Despite a low signal-to-noise ratio, changes in the relaxation behaviour of the skin could be detected. Malignant tissue exhibits faster signal recovery than scar tissue and healthy tissue, which only show a small difference. CONCLUSIONS: Changes in the relaxation behavior can be monitored with the NMR-MOUSE. Before the clinical use of the NMR-MOUSE, sensitivity, sensor mounting device, and sensor tuning must be improved. Further investigations need to be performed on a statistically relevant number of patients.

Nuclear magnetic resonance in inhomogeneous magnetic fields

The response of the spin system has been investigated by numerical simulations in the case of a nuclear magnetic resonance (NMR) experiment performed in inhomogeneous static and radiofrequency fields. The particular case of the NMR-MOUSE was considered. The static field and the component of the radiofrequency field perpendicular to the static field were evaluated as well as the spatial distribution of the maximum NMR signal detected by the surface coil. The NMR response to various pulse sequences was evaluated numerically for the case of an ensemble of isolated spins (1/2). The behavior of the echo train in Carr-Purcell-like pulse sequences used for measurements of transverse relaxation and self-diffusion was simulated and compared with the experiment. The echo train is shown to behave qualitatively differently depending on the particular phase schemes used in these pulse sequences. Different echo trains are obtained, because of the different superposition of Hahn and stimulated echoes forming mixed echoes as a result of the spatial distribution of pulse flip angles. The superposition of Hahn and stimulated echoes originating from different spatial regions leads to distortions of the mixed echoes in intensity, shape, and phase. The volume selection produced by Carr-Purcell-like pulse sequences is also investigated for the NMR-MOUSE. The developed numerical simulation procedure is useful for understanding a variety of experiments performed with the NMR-MOUSE and for improving its performance. Copyright 2000 Academic Press.