Accuracy and reliability of MRI vs. laboratory measurements in an ex vivo porcine model of arthritic cartilage loss.
OBJECTIVE
To quantify the accuracy of magnetic resonance imaging (MRI) measurement of change in cartilage volume due to thin linear excisions, simulating arthritic cartilage losses, by comparison with laboratory volume measurements in an ex vivo porcine model.


METHODS
We scanned 15 porcine patellae by T1-weighted spoiled gradient echo (SPGR) MRI at baseline and after excision of up to three thin layers of articular cartilage. Excised fragment volume was determined from density and weight. Postexcision scans were "fused" to the baseline scan by three-dimensional (3D) registration. This allowed automated recalculation of the remaining cartilage volume within a baseline region of interest (ROI) following each excision. We compared MRI estimates of change in cartilage volume to direct laboratory measurement of fragment volume.


RESULTS
Our 38 excised fragments averaged 0.16 mL, or approximately 7% of cartilage volume. MRI and laboratory estimates of total cartilage volume loss differed by 1.6% +/- 13.2% (mean, coefficient of variation [CV]). Accuracy was +/-0.1 mL for 95% of scans.


CONCLUSIONS
MRI estimates of small changes in porcine patellar cartilage volume were unbiased, reliable, and accurate to 0.1 mL. Despite a proportionately high error in the very thin fragments tested, achievement of similar accuracy in vivo would be adequate to detect approximately two years of osteoarthritic cartilage loss.
Jaremko
Jacob L
JL
Department of Radiology and Diagnostic Imaging, Faculty of Medicine, University of Alberta, Edmonton, Alberta, Canada. jjaremko@ualberta.cay
Maciejewski
Conrad M
CM
Cheng
Rita W T
RW
Ronsky
Janet L
JL
Thompson
Richard B
RB
Lambert
Robert G W
RG
Dhillon
Sukhvinder S
SS
D000818:Animals; D001168:Arthritis / Q000175:diagnosis* / Q000473:pathology*; D002358:Cartilage, Articular / Q000473:pathology*; D004195:Disease Models, Animal; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007717:Knee / Q000473:pathology; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010003:Osteoarthritis / Q000473:pathology; D015203:Reproducibility of Results; D013552:Swine