isbe-astrazeneca strategic alliance project 21 progress report thickness mapping of articular hip...

ISBE-AstraZeneca Strategic Alliance Project 21

Progress Report

Thickness mapping of articular hip cartilage

Twelfth meeting of the Strategic Alliance

Alderley Park, 10 February 2005


Progress Report

Background

• Besides the knee, the hip is the major joint affected by OA. Many studies assessing knee cartilage, still very little in literature on hip (recent report in OA&Cart Aug 2004, Nishii et al measured acetabular cartilage thickness using traction to separate acetabular and femoral cartilage)

• Hip poses greater challenges than knee due to narrower joint space, spherical morphology, ligament and acetabular fossa

• Images collected from six normal volunteers (females aged 22-34), weightbearing and non-weightbearing, two occasions


Progress Report

T1W FS-FFE T2W FFE


Progress Report

Steps

• Segment bone from T2W images, cartilage from T1W images using Endpoint

• Fit to the bone segmentation using a sphere plus cone model and use the results to define a frame of reference

• Build a triangulated surface from the cartilage segmentation using code developed for the knee cartilage

• Produce cartilage thickness maps by finding points of intersection of the triangulated cartilage surface with normals fired from equally spaced points on the bone model sphere

• Look at weightbearing vs non-weightbearing, reproducibility, inter-subject variation


Progress Report

Sphere plus cone fit

• Axis of cone determines coordinate system on the sphere


Progress Report

Cartilage surface construction

• Uses Tom Williams code developed for knee cartilage


Progress Report

Thickness map


Progress Report

Difference map

• Non-weightbearing minus weightbearing


Progress Report

Mean thickness in mm

Subject visit Weight/Non

mean std

1 1 W 2.32 0.89

N 2.39 0.92

2 W 2.27 0.86

N 2.41 0.90

2 1 W 2.43 1.06

N 2.53 1.12

2 W 2.36 0.96

N 2.43 1.06


Progress Report

Next steps

• Complete segmentations for remaining subjects• Statistical analysis• Methods paper?

Future look:• Improve surface building for structures with high curvature• Produce signal intensity maps• Develop improved hip protocol at 3T

– possible to separate acetabular and femoral cartilage?– thinner slices to reduce partial volume effects at curved edges


Progress Report

(Very) preliminary results at 3T

isbe-astrazeneca strategic alliance project 21 progress report thickness mapping of articular hip...

Documents