Soo Jin Kim MD, Presenter: Nothing to Disclose

Jeong Min Lee MD, Abstract Co-Author: Nothing to Disclose

Kyu Ri Son MD, Abstract Co-Author: Nothing to Disclose

Joon Koo Han MD, Abstract Co-Author: Nothing to Disclose

Byung Ihn Choi, Abstract Co-Author: Nothing to Disclose

To determine whether superparamagnetic iron oxide (SPIO)-labeled autologous WBC MR imaging can differentiate soft tissue abscesses from necrotic tumors.

Pre-approval was obtained from our institutional research animal care and use committee. A VX2 carcinoma and a bacterial abscess were experimentally induced into the two hind thighs, respectively, of ten rabbits. Three weeks after inoculating rat feces or tumor chips, rabbits were imaged before and four hours after SPIO-labeled WBC administration at 3.0-T (axial T1-weighted spin-echo, axial and coronal T2*-weighted fast gradient-echo). The images were analyzed qualitatively and quantitatively with regard to signal intensity and signal pattern. The MR findings were correlated with the histopathologic findings which included Prussian blue staining for iron.

On post-contrast T2*-weighted images, curvilinear dark bands were observed in the peripheral regions of the abscesses (P = .004) but, no significant signal drops were observed in either the necrotic or solid portions of the VX2 carcinomas. Quantitative analysis also detected significant signal drop only in the abscess peripheries on post-contrast T2*-weighted images (P < .05). On histopathologic examination, abscess peripheries showing a signal drop were found to contain iron-containing monocytes, thus indicating that the curvilinear dark band observed at the abscess peripheries, was caused by the susceptibility effects of SPIO-tagged monocytes.

The characteristic signal drop at abscess peripheries on SPIO-labeled autologous WBC MR images, caused by the presence of iron-containing monocytes, may be a helpful finding in differentiating abscesses and necrotic tumors.

Macrophage-specific, SPIO-enhanced MR imaging may be helpful in differentiating super-infections from disease progression in cancer patients and would facilitate optimal clinical treatment.

Kim, S, Lee, J, Son, K, Han, J, Choi, B, Superparamagnetic Iron Oxide (SPIO)-labeled White Blood Cell MR Imaging: Differentiation of Abscess and Necrotic Tumor.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4429648.html