Method for measuring the reversible contribution to the transverse

Abstract

A technique for accurately measuring two different spin configurations of transverse magnetization from which the reversible dephasing rate constant R.sub.2 ' can be calculated. Such reversible dephasing may be caused by magnetic field inhomogeneity such as arising from intravascular changes in the oxidation state of hemoglobin, from brain iron, or from cancellous bone, which allows these characteristics to be measured. The different spin configurations can be measured in a single scan by deriving a small R.sub.2 ' through independent and separate measurements of the two magnetization configurations generated by two RF pulses. The two configurations can be recalled independently of each other since they are affected differently by respective gradients flanking the .beta.-pulse which permit one spin configuration to decay with T.sub.2 while the other decays with T.sub.2 * from the same RF pulse. Since the spin configurations come from the same RF pulse, they have the same relaxation time, thus permitting small changes in T.sub.2 ', and hence R.sub.2 ', to be measured by setting the relaxation time of both configurations to be long.