MRI of arthritis: comparison of ultrasmall superparamagnetic iron oxide vs. Gd-DTPA.
OBJECTIVE
To compare the ability of the ultrasmall superparamagnetic iron oxide (USPIO) SHU555C vs. gadopentetate dimeglumine (Gd-DTPA) to detect antigen-induced monoarthritis with MRI.


METHODS
Twelve seven-week-old female rats with an antigen-induced monoarthritis of the right knee were randomly assigned to two groups. Animals in group I (N = 6) underwent MRI using T1-weighted gradient-echo sequences before injection and at 2, 9, 17, 25, 33, 40, 47, 55, and 63 minutes postinjection (p.i.) of Gd-DTPA on day 1, and before injection and at 3, 23, 43, and 123 minutes p.i. of SHU555C on day 2. Animals in group II (N = 6) were imaged before injection and at 3, 23, 43, and 123 minutes p.i. using identical sequences. Signal-to-noise ratios (SNRs) and relative enhancement (DeltaSI%) of arthritic and normal synovium were determined from region-of-interest (ROI) measurements in consensus reading by two experienced radiologists. Data were tested for significant differences between the two agents and between the arthritic and normal knees using a mixed-effect model and F-tests (P < 0.05). Joints were processed for histopathology as the gold standard.


RESULTS
USPIO and Gd-DTPA showed significant enhancement differences (P < 0.001). USPIO provided a progressive and persistent enhancement of arthritic joints while Gd-DTPA provided an early and rapidly declining enhancement. Maximal enhancement in synovitis was 400% at 40-120 minutes p.i. of USPIO vs. 300% at two minutes p.i. of Gd-DTPA. USPIO provided a significant higher difference in enhancement between the arthritic and normal synovium than Gd-DTPA (P < 0.001). Histopathology confirmed marked inflammatory synovial changes in all arthritis-induced right knee joints and normal synovium in all left knee joints.


CONCLUSIONS
Both USPIO and Gd-DTPA detect arthritis by positive T1-enhancement. Compared to standard Gd-DTPA, the USPIO SHU555C provides a comparable maximal T1-enhancement (at two minutes p.i for Gd-DTPA and between 43 and 123 minutes p.i. for SHU555C), but in addition it provides a prolonged T1-enhancement of synovitis and a higher difference between the relative enhancement of arthritic and normal synovium.
Department of Radiology, UCSF Medical Center, University of California San Francisco, San Francisco, California 94143, USA. gerhardhsimon@hotmail.com
Gerhard H
GH
Simon
Johannes
J
von Vopelius-Feldt
Michael F
MF
Wendland
Yanjun
Y
Fu
Guido
G
Piontek
Juergen
J
Schlegel
Mei-Hsiu
MH
Chen
Heike E
HE
Daldrup-Link
D000818:Animals; D001169:Arthritis, Experimental / Q000175:diagnosis*; D003287:Contrast Media / Q000008:administration & dosage*; D003911:Dextrans; D004195:Disease Models, Animal; D005260:Female; D052203:Ferrosoferric Oxide; D019786:Gadolinium DTPA; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007501:Iron; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D010087:Oxides; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010087:Oxides; C097921:ferumoxtran-10; D007501:Iron; D019786:Gadolinium DTPA; D052203:Ferrosoferric Oxide