Preliminary study of PASP-USPIO in normal rabbit MR brain perfusion

Objective To explore the practicability and optimal dosage of polyaspartic acid (PASP)-surface-modified ultra-small superparamagnetic iron oxide (USPIO) (PASP-USPIO) in normal rabbit brain perfusion. Methods Thirty New Zealand rabbits were randomly divided into groups A1, A2, A3, A4 and C. Animals in groups A1-4 were intravenously injected (i.v.) with 5 μmol/kg, 10 μmol/kg, 20 μmol/kg and 40 μmol/kg PASP-USPIO, while animals in group C were injected (i.v.) with 0.2 mmol/kg gadolinium diethyl triamine-pentoacetic acid (Gd-DTPA), serving as a control group. Each group was subjected to T₂^* Gradient Echo-Echo Planar Imaging (T₂^*GRE-EPI)-sequenced perfusion-weighted imaging to obtain signal intensity-time curves, which were used to calculate the regional cerebral blood volume (rCBV), the maximum signal drop percentage (SRR_max), and Q_rCBV-Q_SRRmaX values. Data were compared within and between groups. Results The intra-group rCBV value and SRR_max value were significantly different between gray matter and white matter. The inter-group Q_rCBV and Q_SRRmax values were also significantly different. ANOVA analysis indicated that the Q_rCBV and Q_SRRmax values in group A4 were significantly different from those in other groups, while there were no significant differences among group A1, A2, A3 and C. Conclusion PASP-USPIO has colloid stability and can be used in normal rabbit MR brain perfusion. The optimal dosage is 10 μmol/kg.