Comparison of GE- and SE-sequences after i.v. application of superparamagnetic iron oxides in MRI of experimentally induced soft-tissue osteosarcomas.

Purpose: An MRI study on experimentally induced osteosarcomas of the peripheral soft-tissues in nude Fats was conducted, comparing SE- and CE-sequences after i.v. application of superparamagnetic iron oxides with regard to contrast and image quality. Material and methods: 40 nude rats with an osteosarcoma in the right hind leg and 7 tumour-free animals were measured without, one and 48 hours after i.v.-injection of the contrast medium. 4 SE- and 3 GE-sequences with different parameters and slice orientation were applied. The contrast medium consisted of Fe3O4-particles with a core diameter of 6-8 nm and a coating material of polyethytene glycol (PEG). The laboratory animals were divided into 5 groups of 7 - 12 animals each. The rats of the first 4 groups were given a contrast medium-dosage of 100, 150, 200 and 250 mu mol Fe/kg body weight, respectively. The animals of the fifth group were tumour-free and served as controls. Results: The minimum dosage for detection of Fe3O4 containing PEG-magnetites, one hour after application, was established at 700-150 mu mol Fe/kg body weight. The higher the dosage of the contrast medium, the more signal alterations could be measured. The CE sequences were more sensitive than SE sequences. One GE sequence with the parameters T-R 90 ms, T-E 13 ms, FL 8 degrees turned out to be highly sensitive. Conclusion: Superparamagnetic iron oxides induce signal alterations in tumours of the peripheral soft-tissue. CE sequences proved to be more sensitive than SE sequences.