Volume measurement of bone erosions in magnetic resonance images of patients with rheumatoid arthritis.

The volume of bone erosions in the metacarpophalangeal joints is a radiological feature that can be used to track the progression of rheumatoid arthritis. We introduce a hybrid segmentation algorithm that combines region growing and level-set segmentation algorithms to semiautomatically measure the volume of bone erosions in magnetic resonance images. A total of 40 rheumatoid arthritis patients were included in the study. The scans of eight patients were used for training, whereas the remaining 32 scans were used to determine the accuracy, precision, and speed of the technique. The reproducibility of the semiautomated technique and that of manual segmentation was defined in terms of intraclass correlation coefficients. Both techniques were equally precise with intraclass correlation coefficient values greater than 0.9. The hybrid algorithm was highly accurate: the least squares fit between the semiautomated segmentations to those manually traced by a musculoskeletal radiologist resulted in a slope of 1.030 with an x-intercept of 1.385 mm(3) and an R(2) value of 0.923. The semiautomated technique was significantly faster than manual segmentation, which took two to four times longer to complete. Our hybrid algorithm shows promise in the quantitative assessment of radiological features of rheumatoid arthritis in a clinical setting.

Quantitative analysis of subchondral sclerosis of the tibia by bone texture parameters in knee radiographs: site-specific relationships with joint space width.

OBJECTIVES: To determine the ability of radiographic bone texture (BTX) parameters to quantify subchondral tibia sclerosis and to examine clinical relevance for assessing osteoarthritis (OA) progression. We examined the relationship between BTX parameters and each of (1) location-specific joint space width (JSW) [JSW(x)] and minimum JSW (mJSW) of the affected compartment, and (2) knee alignment (KA) angle in knee radiographs of participants undergoing total knee arthroplasty (TKA). DESIGN: Digitized fixed-flexion knee radiographs were analyzed for run-length and topological BTX parameters in a subchondral region using an algorithm. Medial JSW(x) was computed at x=0.200, 0.225, 0.250 and 0.275 according to a coordinate system defined by anatomic landmarks. mJSW was determined for medial and lateral compartment lesions. KA angles were determined from radiographs using an anatomic landmark-guided algorithm. JSW measures and the magnitude of knee malalignment were each correlated with BTX parameters. Reproducibility of BTX parameters was measured by root-mean square coefficients of variation (RMSCV%). RESULTS: Run-length BTX parameters were highly reproducible (RMSCV%<1%) while topological parameters showed poorer reproducibility (>5%). In TKA participants (17 women, 13 men; age: 66+/-9 years; body mass index (BMI): 31+/-6 kg m(-2); WOMAC: 41.5+/-16.1; Kellgren-Lawrence score mode: 4), reduced trabecular spacing (Tb.Sp) and increased free ends (FE) were correlated with decreased JSW after accounting for BMI, gender and knee malalignment. These relationships were dependent on site of JSW measurement. CONCLUSION: High reproducibility in quantifying bone sclerosis using Tb.Sp and its significant relationship with JSW demonstrated potential for assessing OA progression. Increased trabecular FE and reduced porosity observed with smaller JSW suggest collapsing subchondral bone or trabecular plate perforation in advanced knee OA.