SIZE DISTRIBUTION OF MAGNETIC CORES IN CONTRAST MATERIALS FOR MRI DIAGNOSTICS

In medical diagnostics by magnetic resonance imaging (MRT) one uses co ntrast materials to enhance preferred tissues. These materials general ly contain cores of small magnetic particles of iron compounds. Their size distribution affects their tissue preference. We have used Mossba uer spectroscopy to determine the particle size distribution of six di fferent contrast materials. The spectra of the materials at temperatur es 4.6 K to 260 K were analyzed in terms of a particle distribution wh ere the volume determines the super-paramagnetic relaxation rate and t he Fe magnetic hyperfine field. The average particle size obtained agr ees with determinations by other experimental techniques.