QUANTIFICATION OF SIGNAL MODULATION OF ER YTHROGENETIC BONE-MARROW INGRADIENT-ECHO SEQUENCES - RESULTS FROM PHANTOMS AND PATIENTS WITH SIMULTANEOUS DETERMINATION OF T-2-ASTERISK RELAXATION-TIMES

The signals from spongy bone on gradient echo seguences depend on the fat and water proton content as well as the differences in magnetic su sceptibility at the border between the trabeculae and the bone marrow. From the signal intensities for different echo times, signal modulati on was quantified by a special algorithm and at the same time the T-2( ) relaxation time was calculated. Using a fat-water phantom, it was s hown that the product of the initial fat and water signal intensity (m odulation coefficient) is applicable to indicate the extent of signal modulation and thereby the chemical shift and, moreover, to indicate c hanges in the fat/water ratio sensitively. In 16 individuals of differ ent ages (23 to 64 years, average 42.4 years) there was a tendency for the T-2() relaxation time from the spongiosa of lumbar vertebrae to increase with age; this can be explained by a reduction in the trabecu lar content, causing reduction in the magnetic inhomogeneity of the bo ne marrow. The results indicate the usefulness of the sequence and the mathematical model for evaluating the spongy bone in eases of osteopo rosis and of malignant haematological disorders.