Importance

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Abstract

This invention relates to a set of aqueous marker compositions, each composition having a selected 1/T.sub.i value which is substantially invariant over an at least 10.degree. C. temperature range between 15 and 40.degree. C. and preferably over an at least .+-.2% magnetic field strength range about a selected field strength value between 0.01 and 5T and comprising an aqueous matrix material having a non-zero 1/T.sub.i temperature dependence within said temperature range with distributed therein a first paramagnetic material having a T.sub.i relaxivity which is substantially invariant within said range(s) and/or a second paramagnetic material having within said ranges(s) and T.sub.1 relaxivity which has a non-zero temperature dependence of opposite polarity to the temperature dependence of 1/T.sub.i of said matrix material, said set containing a plurality of said compositions with different selected 1/T.sub.i values preferably encompassing at least the range 1.0 to 2.5 s.sup.-1, said set preferably comprising at least one said composition containing said second paramagnetic material and at least one said composition containing said first paramagnetic material, where i in T.sub.i is 1 or 2.

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First Claim