Power Doppler evaluation of joint effusions: investigation in a rabbit model.
OBJECTIVE
To study the power Doppler findings of septic arthritis and noninfectious synovitis in an animal model.


METHODS
The right knees of 10 rabbits were inoculated with an aqueous suspension of Staphylococcus aureus. The right knees of 5 rabbits were injected with talc suspension. The right knees of 5 rabbits were injected with saline. All 20 left knees were injected with saline. Serial power Doppler images were obtained using constant-imaging parameters. Images were reviewed by blinded observers who assessed for increased power Doppler signal.


RESULTS
All 10 knees inoculated with S. aureus developed septic arthritis. Each infected rabbit knee demonstrated increased signal on power Doppler on at least one examination, ranging from 1-6 days after inoculation. Only 23 of 45 examinations of infected knees were unequivocally positive by power Doppler on examinations performed 1 to 6 days after inoculation. No knee with talc synovitis demonstrated increased power Doppler signal. No control knee demonstrated increased power Doppler signal.


CONCLUSIONS
Increased power Doppler signal may be seen with septic arthritis; however, its intensity and timing may vary from subject to subject. A normal power Doppler examination does not exclude septic arthritis.
Division of Pediatric Radiology, C. S. Mott Children's Hospital, University of Michigan Medical Center, 1500 East Medical Center Drive, Ann Arbor, MI 48109-0252, USA.
P J
PJ
Strouse
M A
MA
DiPietro
E L
EL
Teo
K
K
Doi
C E
CE
Chrisp
D000818:Animals; D001170:Arthritis, Infectious / Q000000981:diagnostic imaging*; D004195:Disease Models, Animal; D005122:Exudates and Transudates; D007091:Image Processing, Computer-Assisted; D007717:Knee / Q000382:microbiology / Q000473:pathology; D011817:Rabbits; D012680:Sensitivity and Specificity; D013203:Staphylococcal Infections / Q000000981:diagnostic imaging*; D013211:Staphylococcus aureus; D013583:Synovial Membrane / Q000382:microbiology / Q000473:pathology*; D013585:Synovitis / Q000139:chemically induced / Q000000981:diagnostic imaging* / Q000382:microbiology; D013627:Talc; D018608:Ultrasonography, Doppler
D013627:Talc