Pelvic lymph node visualization with MR imaging using local administration of ultra-small superparamagnetic iron oxide contrast

Purpose: To determine if interstitial injection of iron oxide particles improves visualization of pelvic lymph nodes at magnetic resonance imaging (MRI) and to determine the effect of injection site on location of visualized nodes. Materials and Methods: In nine healthy volunteers, ferumoxtran-10 iron oxide (0.28 mg iron per kg) was injected into the anterior thigh (three subjects) or perianal (three subjects) or periprostatic tissues (three subjects). MRI at 1.5 T was performed before injection and one, three, and seven days after injection. Results: The mean of 30 nodes seen post-injection was greater than the mean of 5.8 seen pre-injection (P < 0.001). After thigh injection, a mean of three internal vs. 36 external nodes were seen. Compared with thigh injection, there was a higher fraction of internal nodes with perianal (mean of nine internal vs. 14 external, P < 0.001) and periprostatic injection (mean of I I internal vs. five external, P < 0.001). More nodes were seen with gradient-echo sequences than with other sequences (P < 0.001). Conclusion: Interstitial injection of iron oxide particles increases visualization of pelvic lymph nodes. Perianal and periprostatic injection increases the number of internal pelvic lymph nodes seen compared with thigh injection.