Functional magnetic resonance imaging using iron oxide particles in characterizing head and neck adenopathy

Objectives: In lymph nodes harboring metastases the reticuloendothelial sys tem is replaced by tumor cells and does not concentrate iron particles. Thi s study assesses the value of contrast magnetic resonance imaging (MRI) usi ng ultrasmall superparamagnetic iron oxide particles (Combidex, Advanced Ma gnetics, Inc., Cambridge, MA) to characterize and stage neck nodes. Study D esign: Prospective analysis of neck imaging by Combidex MRI, with correlati on from pathological assessment of resected lymph nodes. Methods: Nine pati ents underwent MRI and subsequent bilateral neck dissections (three), unila teral neck dissections (five) or fine-needle aspiration (one). Each case wa s evaluated for the number, location, MRI characteristics, and pathological assessment of lymph nodes. Results: Forty-nine separate nodal levels were evaluated with both Combidex MRI and pathological assessment. The presence of metastatic nodal involvement among 45 levels was correctly assessed by t he Combidex MRI (three false-negative results, one false-positive result; s ensitivity, 84%; specificity, 97%). Analysis was possible for 101 of the in dividual lymph nodes identified by MRI that could be correlated with indivi dual nodes pathologically examined. Combidex MRI assessment was correct for 99 nodes (one-false positive result, one false-negative result; sensitivit y, 95%, specificity, 99%). Standard MRI interpretation without Combidex ide ntified that 12 of 18 nodes (67%) that were greater than or equal to 10 mm (greatest dimension) contained tumor, whereas 9 of 83 nodes (11%) that were less than 10 mm contained tumor. Conclusions: Combidex MRI provides functi onal information to characterize lymph nodes in the clinical staging of squ amous cell carcinoma of the head and neck. The inability of MRI to identify small lymph nodes restricts the usefulness of this technique.