EVALUATION OF AN ULTRASMALL SUPERPARAMAGNETIC IRON-OXIDE IN MRI IN A BONE-TUMOR MODEL IN RABBITS

Ultrasmall superparamagnetic iron oxides (USPIOs) are a class of MRI c ontrast agents having moderately selective affinity for the reticuloen dothelial cells of lymph nodes and bone marrow, This study evaluated a USPIO preparation, Combidex (Code 7227), in MRI of a rabbit bone tumo r model, VX2 carcinoma implanted into the tibial marrow of nine subjec t rabbits was studied. After tumor growth, the subjects underwent MRI of their lesions both before and after intravenous administration of C ode 7227. Code 7227 was judged subjectively to conspicuously reduce th e signal intensity of normal marrow on some pulse sequences. A hypoint ense zone outlined the tumor margins on postcontrast imaging, which al lowed improved visualization of the soft tissue component of the large r lesions. Accumulation of the contrast agent in a zone of inflammatio n outside the tumor margin was demonstrated on histologic sections of the lesions. Code 7227 deserves additional study as a potential contra st agent for MRI of bone tumors.