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The objective of this work was to assess the feasibility and accuracy of T1 and relaxivity measurements in cell cultures using 1.5T magnetic resonance imaging (MRI) with the longterm goal to develop a tool for evaluation of novel paramagnetic agents in a realistic macromolecular environment. This initial study was carried out using MCF-7 cells treated with independently determined concentrations of Gd-DTPA.

The role of water of hydration in proton relaxation in tissues as exemplified by hydrated collagen in beef tendon was studied as a function of temperature from -40 degrees to 37 degrees C by using cross-relaxation spectroscopy. Experimental data were fitted to a simple binary spin-bath model. The outcome of this procedure allows the construction of a semi-quantitative depiction of proton relaxation in a heterogeneous system and its change as one of the water fractions freezes at about -10 to -20 degrees C, a transition observed by NMR and confirmed independently by differential scanning calorimetry. Such physical depiction provides a crude but insightful interpretation of the role "bound" water plays in proton relaxation. This may be important in shedding light on the mechanism of tissue relaxation and its role in MRI diagnosis, particularly for those diseases such as liver cirrhosis where the water-macromolecular interaction plays a prominent role.

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