SPIO-Enhanced Magnetic Resonance Imaging Of The Bone Marrow: Experimental Study

Objectives:1. to evaluate SPIO enhancement of normal bone marrow in New Zealand White Rabbits2. to assess the application of SPIO in a bone tumor model in rabbits3. to compare the efficiencies of Gd-DTPA and SPIO in MRI in a bone tumor model in rabbitsSubjects and Methods:1. 12 New Zealand Whites Rabbits were divided into two groups at random: normal, bone tumor group.2. For the signal-time course study, four sequences of MR images (T,WI, T2WI, T2*WI, STIR) were obtained before and 6hr to 16d after injection of SPIO-2 into an ear vein at a dose 200u mol/kg, and the signal intensity was measured respectively on four sequences of images.3. Bone tumor model was developed in 6 rabbits by inoculation of VX2 tumor fragments into the proximal tibial bone marrow.4. Four sequences of MR imagings (TtWI, T2WI, T2*WI, STIR) of the proximal tibia of 6 bone tumor model were obtained before and 24hr after injection SPIO-2 into an ear vein at a dose 200umol/kg, and to compare with Gd-DTPA imagings..5. Bone marrow biopsy were performed in normal group pre- and post-SPIO-2 enhanced MR imaging, and the bone marrow were processed for the pathological study. In the bone tumor group, the inoculated tibias were dissected free for the aim of pathological study.Results:1. normal group:After administration of SPIO, the SI of the normal bone marrow reduced significantly, and the maximal reduction of SI occurred at 24hr. The iron-oxide-induced decrease in bone marrow signal intensity was most pronounced on STIR images. T2*WI sequences images were of poor diagnostic quality for bone marrow due to artifactual magnetic susceptibility.2. tumor group:On enhanced images, the SI of the bone tumor remained unchanged, while the normal marrow reduced significantly. The contrast between normal bone marrow and bone tumor increased significantly. Pathological findings showed that bone tumor have only a minor or no iron oxide uptake, whereas normal bone marrow have large number of iron oxide uptake. There were significances on CNR between Gd-DTPA imagings and SPIO-2 imagings.Conclusions:l.The bone marrow enhanced MR image may be optimally obtained 6~24hr after injection SPIO-2 into an ear vein.2. SPIO-2 may be used to improve the contrast between normal bone marrow and bone tumor and may allow distinction of normal marrow from bone tumor by means of their different phagocytic activities.3. SPIO-2 imagings may demonstrate bone tumor more clearly and more accurately than Gd-DTPA...