Assessment of musculoskeletal infection in rats to determine usefulness of SPIO-enhanced MRI.
OBJECTIVE
The objective of our study was to evaluate the usefulness of superparamagnetic iron oxide (SPIO)-enhanced MRI in experimental models of infectious disease and to analyze the intracellular uptake of SPIO.


METHODS
Nine rats with infectious arthritis of the knee or soft-tissue infection were imaged on an MRI unit on days 4-6 after i.v. injection of a bacterial suspension. All animals were imaged on a T2-weighted fast spin-echo sequence before and 24 hours after administration of SPIO. The nine rats were classified into two groups according to the dose of SPIO. We calculated the relative signal-to-noise ratio (SNR) change and compared the relative SNR change with the histologic findings. We analyzed iron-loaded cells and the intracellular uptake of iron particles according to the dose of SPIO.


RESULTS
The SNR value decreased in proportion to the increase in the number of iron-laden macrophages or fibroblasts in the wall of the soft-tissue abscess (p < 0.01). The intracellular uptake of iron particles was shown in fibroblasts as well as in macrophages, and their uptake in the fibroblasts was greater than that in the macrophages (p < 0.05). There was no statistically significant difference in the intracellular uptake of iron particles according to the dose of SPIO (p > 0.1).


CONCLUSIONS
SPIO-enhanced MRI can be useful in evaluating infectious disease of the joint or soft tissue and is influenced by the uptake of iron particles in fibroblasts as well as macrophages.
Lee
Sang Min
SM
Department of Radiology, Bundang CHA General Hospital, College of Medicine, Pochon CHA University, Kyonggi-do 463-712, Korea.
Lee
Sang Hoon
SH
Kang
Hae Youn
HY
Baek
Seung Yon
SY
Kim
Sung Moon
SM
Shin
Myung Jin
MJ
D000818:Animals; D001168:Arthritis / Q000175:diagnosis*; D003287:Contrast Media; D005290:Ferric Compounds; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D018461:Soft Tissue Infections / Q000175:diagnosis*; D013203:Staphylococcal Infections / Q000175:diagnosis*
D003287:Contrast Media; D005290:Ferric Compounds; C000499:ferric oxide