Three-dimensional computerized reconstruction. Illustration of incremental articular cartilage thinning.
OBJECTIVE
The authors have addressed the ability of magnetic resonance (MR) imaging to resolve incremental thinning of articular cartilage by assessment of three-dimensional (3-D) and two-dimensional (2-D) representations.


METHODS
Using a porcine knee model, sequential cartilage shavings were characterized using a 3-D fat suppressed spoiled gradient-echo (SPGR) MR imaging protocol that provided good contrast between high-signal articular cartilage and lower signal surrounding tissues. Lesion dimensional measurements were made on both MR images and 3-D computerized reconstructions. Volumes of cartilage removed were approximately 0.06 mL.


RESULTS
Incremental articular cartilage thinning typically was apparent on 3-D reconstructed images. Three-dimensional articular cartilage reconstructions were effective in depicting location and orientation of shaved cartilage regions. Average percent error associated with length and with measurements based on 2-D MR images was approximately 19% for observer 1 and 33% for observer 2 when compared with direct measurements of the shaved cartilage. Average percent error of thickness measurements based on 2-D MR was approximately 21% for observer 1 and 37% for observer 2. Overall average errors associated with length, width, and thickness measurements were approximately 25%.


CONCLUSIONS
Incremental thinning of articular cartilage can be tracked qualitatively and quantitatively using 3-D computerized reconstructions and 2-D MR images. Errors associated with the quantitative measurements can be attributed to limitations of measurement methods and intrinsic limitation of MR resolution.
Tebben
P J
PJ
Imaging Resource Center, Kansas University School of Medicine, Kansas City 66103, USA.
Pope
T W
TW
Hinson
G
G
Batnitzky
S
S
Wetzel
L H
LH
DePaolis
D C
DC
Munns
S
S
Wilkinson
S B
SB
Gordon
M A
MA
D000818:Animals; D002358:Cartilage, Articular / Q000473:pathology*; D004195:Disease Models, Animal; D007091:Image Processing, Computer-Assisted; D007719:Knee Joint / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015588:Observer Variation; D010003:Osteoarthritis / Q000175:diagnosis; D012680:Sensitivity and Specificity; D013552:Swine